ARNA Arena Pharmaceuticals Inc

You are cordially invited to attend a virtual special meeting (including any adjournments or postponements thereof, the “Special Meeting”) of stockholders of Arena Pharmaceuticals, Inc. (“Arena”) to be held virtually on    , 2022, at    Pacific Time at www.virtualshareholdermeeting.com/ARNA2022SM.

At the Special Meeting, you will be asked to consider and vote on (i) a proposal to adopt the Agreement and Plan of Merger, dated December 12, 2021 (such agreement, as it may be amended, modified or supplemented from time to time, the “Merger Agreement”), by and among Arena, Pfizer Inc., a Delaware corporation (“Pfizer”), and Antioch Merger Sub, Inc., a Delaware corporation (“Merger Sub”), (ii) a proposal to approve, on an advisory (non-binding) basis, the compensation that may be paid or become payable to Arena’s named executive officers that is based on or otherwise relates to the Merger Agreement and the transactions contemplated by the Merger Agreement (the “Compensation Proposal”), and (iii) a proposal to approve the adjournment of the Special Meeting to a later date or dates, if necessary or appropriate, including to solicit additional proxies to approve the proposal to adopt the Merger Agreement if there are insufficient votes to adopt the Merger Agreement at the time of the Special Meeting (the “Adjournment Proposal”). Upon the terms and subject to the conditions of the Merger Agreement, Merger Sub will merge with and into Arena, with Arena continuing as the surviving corporation and a wholly owned subsidiary of Pfizer (the “Merger”).

If the Merger is completed, you will be entitled to receive $100.00 in cash, without interest thereon and subject to any withholding of taxes, for each share of Arena common stock (“common stock”) that you own (unless you have properly exercised your appraisal rights), which represents a premium of approximately 100% to the closing price of Arena’s common stock on December 10, 2021, the last full trading day prior to the announcement of the Merger.

Arena’s Board of Directors (the “Board of Directors”), after considering the factors more fully described in the enclosed proxy statement, has unanimously: (i) determined that the Merger and the transactions contemplated thereby are advisable, fair to and in the best interests of Arena and Arena’s stockholders; (ii) approved and declared it advisable to enter into the Merger Agreement; (iii) directed that the adoption of the Merger Agreement be submitted to a vote of Arena’s stockholders at the Special Meeting; and (iv) subject to the terms and conditions of the Merger Agreement, resolved to recommend that Arena’s stockholders approve the adoption of the Merger Agreement and approve the Merger on the terms and subject to the conditions set forth therein. The Board of Directors unanimously recommends, on behalf of Arena, that you vote: (1) “FOR” the adoption of the Merger Agreement; (2) “FOR” the approval, on an advisory (non-binding) basis, of the Compensation Proposal; and (3) “FOR” the Adjournment Proposal.

The enclosed proxy statement provides detailed information about the Special Meeting, the Merger Agreement and the Merger. A copy of the Merger Agreement is attached as Annex A to the proxy statement.

The proxy statement also describes the actions and determinations of the Board of Directors in connection with its evaluation of the Merger Agreement and the Merger. You should carefully read and consider the entire enclosed proxy statement and its annexes, including, but not limited to, the Merger Agreement, as they contain important information about, among other things, the Merger and how it affects you.

Whether or not you plan to attend the Special Meeting virtually, please sign, date and return, as promptly as possible, the enclosed proxy card in the accompanying prepaid reply envelope or grant your proxy electronically over the Internet or by telephone (using the instructions provided in the enclosed proxy card). If you attend the Special Meeting and vote at the meeting your vote will revoke any proxy that you have previously submitted.

If you hold your shares in “street name,” you should instruct your bank, broker or other nominee how to vote your shares in accordance with the voting instruction form that you will receive from your bank, broker or other nominee. Your bank, broker or other nominee cannot vote on any of the proposals, including the proposal to adopt the Merger Agreement, without your instructions.

Your vote is very important, regardless of the number of shares that you own. We cannot complete the Merger unless the proposal to adopt the Merger Agreement is approved by the affirmative vote of the holders of a majority of the shares of Arena’s common stock that are issued and outstanding as of the close of business on   , which is the record date for the Special Meeting.

If you have any questions or need assistance voting your shares, please contact our proxy solicitor:

On behalf of the Board of Directors, I thank you for your support and appreciate your consideration of this matter.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the Merger, passed upon the merits or fairness of the Merger Agreement or the transactions contemplated thereby, including the proposed Merger, or passed upon the adequacy or accuracy of the information contained in the accompanying proxy statement. Any representation to the contrary is a criminal offense.

The accompanying proxy statement is dated    , 2022 and, together with the enclosed form of proxy card, is first being mailed on or about    , 2022.

The following questions and answers address some commonly asked questions regarding the Merger, the Merger Agreement and the Special Meeting. These questions and answers may not address all questions that are important to you. You should carefully read and consider the more detailed information contained elsewhere in this proxy statement and the annexes to this proxy statement, including, but not limited to, the Merger Agreement, along with all of the documents we refer to in this proxy statement, as they contain important information about, among other things, the Merger and how it affects you. You may obtain the information incorporated by reference in this proxy statement without charge by following the instructions under the caption, “Where You Can Find More Information.”

This proxy statement and any documents referred to in this proxy statement contain certain forward-looking statements within the meaning of the federal securities laws with respect to the proposed Merger, including, but not limited to, statements regarding the expected benefits of the proposed Merger and the anticipated timing of the proposed Merger, strategies, objectives, future performance and the products and markets of each company. These forward-looking statements generally are identified by the words “believe,” “predict,” “target,” “contemplate,” “potential,” “project,” “expect,” “anticipate,” “estimate,” “intend,” “strategy,” “future,” “opportunity,” “plan,” “may,” “should,” “will,” “would,” “could,” “will be,” “will continue,” “will likely result,” and similar expressions. Forward-looking statements are predictions, projections and other statements about future events that are based on current expectations and assumptions and, as a result, are subject to risks and uncertainties. Many factors could cause actual future events to differ materially from the forward-looking statements in this proxy statement, including but not limited to:

The risks and uncertainties may be amplified by the COVID-19 pandemic (and related variants), which has caused significant economic uncertainty. The extent to which the COVID-19 pandemic (and related variants) impacts Arena’s businesses, operations, and financial results, including the duration and magnitude of such effects, will depend on numerous factors, which are unpredictable, including, but not limited to, the duration and spread of the outbreak, its severity, the actions to contain the virus or treat its impact, and how quickly and to what extent normal economic and operating conditions can resume. The foregoing list of factors is not exhaustive. You should carefully consider the foregoing factors and the other risks and uncertainties that affect the businesses of Pfizer and Arena described in the “Risk Factors” section of their respective Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q and other documents filed by either of them from time to time with the SEC. These filings identify and address other important risks and uncertainties that could cause actual events and results to differ materially from those contained in the forward-looking statements. Forward-looking statements speak only as of the date they are made. Readers are cautioned not to put undue reliance on forward-looking statements, and Arena assumes no obligation to, and does not intend to, update or revise these forward-looking statements, whether as a result of new information, future events, or otherwise, unless required by law. Arena gives no assurance that it will achieve its expectations.

Consequently, all of the forward-looking statements that we make in this proxy statement are qualified by the information contained or incorporated by reference herein, including: (i) the information contained under this caption; and (ii) the information contained under the caption “Risk Factors,” and information in our consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the period ended December 31, 2020 and elsewhere in our most recent filings with the SEC, including our Quarterly Report on Form 10-Q for the quarter ended March 31, 2021, Quarterly Report on Form 10-Q for the quarter ended June 30, 2021, Quarterly Report on Form 10-Q for the quarter ended September 30, 2021 and any subsequent reports on Form 10-K, Form 10-Q or Form 8-K filed with the SEC from time to time and available at www.sec.gov. No assurance can be given that these are all of the factors that could cause actual results to vary materially from the forward-looking statements.

Stockholders are advised to consult any future disclosures that we make on related subjects as may be detailed in our other filings made from time to time with the SEC.

The enclosed proxy is solicited on behalf of the Board of Directors for use at the Special Meeting.

We will hold the Special Meeting virtually on    , 2022 at     Pacific Time at www.virtualshareholdermeeting.com/ARNA2022SM and, if applicable, at any adjournment or postponement thereof.

At the Special Meeting, we will ask stockholders to vote on proposals to: (i) adopt the Merger Agreement; (ii) approve, on an advisory (non-binding) basis, the Compensation Proposal; and (iii) approve the Adjournment Proposal.

We do not expect that any matters other than the proposals set forth above will be brought before the Special Meeting, and only matters specified in the notice of the meeting may be acted upon at the Special Meeting.

Our stockholders must approve the proposal to adopt the Merger Agreement in order for the Merger to be consummated. If our stockholders fail to approve the proposal to adopt the Merger Agreement, the Merger will not be consummated. A copy of the Merger Agreement is attached as Annex A to this proxy statement, which we urge you to read carefully in its entirety.

Only stockholders of record as of the Record Date are entitled to notice of the Special Meeting and to vote at the Special Meeting. A list of stockholders entitled to vote at the Special Meeting will be available at our principal executive offices located at 136 Heber Avenue, Suite 204, Park City, Utah 84060, during regular business hours for a period of no less than ten (10) days before the Special Meeting and will be available electronically at the Special Meeting.

The holders of a majority of the stock issued and outstanding and entitled to vote thereat, present virtually or represented by proxy, will constitute a quorum at the Special Meeting. As of the Record Date, there were     shares of common stock outstanding and entitled to vote at the Special Meeting, meaning that     shares of common stock must be represented virtually or by proxy at the Special Meeting to have a quorum. In the event that a quorum is not present at the Special Meeting, it is expected that the meeting will be adjourned to solicit additional proxies to approve the proposal to adopt the Merger Agreement.

The affirmative vote of the holders of a majority of the shares of common stock that are issued and outstanding as of the Record Date is required to adopt the Merger Agreement. As of the Record Date,    shares constitute a majority of the outstanding shares of common stock. Adoption of the Merger Agreement by stockholders is a condition to the Closing.

The affirmative vote of a majority of the votes cast virtually or by proxy at the Special Meeting is required to approve the Compensation Proposal, on an advisory (non-binding) basis.

The affirmative vote of a majority of the votes cast virtually or by proxy at the Special Meeting is required to approve the Adjournment Proposal, whether or not a quorum is present.

An abstention represents a stockholder’s affirmative choice to decline to vote on a proposal. If a stockholder abstains from voting, that abstention will have the same effect as if the stockholder voted “AGAINST” the proposal to adopt the Merger Agreement. Abstentions will have no effect on the outcome of the Compensation Proposal or Adjournment Proposal but will be used to determine whether a quorum is present at the Special Meeting. As a result, an abstention of any of the aforementioned proposals will be counted for purposes of determining the presence or absence of a quorum, but will only count as a vote “AGAINST” the proposal to adopt the Merger.

Each “broker non-vote” will also count as a vote “AGAINST” the proposal to adopt the Merger Agreement, but will have no effect on the Compensation Proposal or any Adjournment Proposal. A “broker non-vote” generally occurs when a bank, broker or other nominee holding shares on your behalf does not vote on a proposal because the bank, broker or other nominee has not received your voting instructions and lacks discretionary power to vote the

shares. “Broker non-votes,” if any, will be counted for the purpose of determining whether a quorum is present. However, because none of the proposals to be voted on at the Special Meeting are routine matters for which brokers may have discretionary authority to vote, Arena does not expect any broker non-votes at the special meeting. As such, if you fail to instruct your broker, bank or other nominee how to vote your shares, your shares will not be counted towards a quorum at the Special Meeting.

As of the Record Date, our directors and executive officers beneficially owned and were entitled to vote, in the aggregate,    shares of common stock, representing approximately   % of the shares of common stock outstanding on the Record Date (and approximately   % of the shares of common stock outstanding when taking into account Arena Options, Arena RSUs and Arena PRSUs held, in the aggregate, by our directors and executive officers).

Our directors and executive officers have informed us that they currently intend to vote all of their respective shares of common stock (i) “FOR” the adoption of the Merger Agreement, (ii) “FOR” the approval, on an advisory (non-binding) basis, of the Compensation Proposal, and (iii) “FOR” the approval of the Adjournment Proposal.

If, at the close of business on the Record Date, your shares are registered in your name with our transfer agent, Computershare Trust Company, N.A., on the Record Date, you may cause your shares to be voted by returning a signed and dated proxy card in the accompanying prepaid envelope, or you may vote virtually at the Special Meeting. Additionally, you may grant a proxy electronically over the Internet or by telephone (using the instructions provided in the enclosed proxy card). You must have the enclosed proxy card available, and follow the instructions on the proxy card, in order to grant a proxy electronically over the Internet or by telephone. Based on your proxy card or Internet and telephone proxies, the proxy holders will vote your shares according to your directions.

If you plan to attend the Special Meeting and wish to vote virtually, you will need to enter the 16-digit Control Number found next to the label “Control Number” on your proxy card voting instruction form, or in the email sending you the proxy statement. If you attend the Special Meeting, and vote virtually, your vote will revoke any previously submitted proxy. If your shares are registered in your name, you are encouraged to vote by proxy even if you plan to attend the Special Meeting virtually.

Voting instructions are included on your proxy card. All shares represented by properly signed and dated proxies received in time for the Special Meeting will be voted at the Special Meeting in accordance with the instructions of the stockholder. Properly signed and dated proxies that do not contain voting instructions will be voted:

If, at the close of business on the Record Date, your shares are held in “street name” through a bank, broker or other nominee, you may vote through your bank, broker or other nominee by completing and returning the voting form provided by your bank, broker or other nominee or attending the Special Meeting and voting virtually with a “legal proxy” from your bank, broker or other nominee. If such a service is provided, you may vote over the Internet or telephone through your bank, broker or other nominee by following the instructions on the voting form provided by your bank, broker or other nominee. If you do not return your bank’s, broker’s or other nominee’s voting form, do not vote via the Internet or telephone through your bank, broker or other nominee, if possible, or do not attend the Special Meeting and vote virtually with a “legal proxy” from your bank, broker or other nominee, it will have the same effect as if you voted “AGAINST” the proposal to adopt the Merger Agreement but will not have any effect on the Compensation Proposal or the Adjournment Proposal.

If you are a stockholder of record entitled to vote at the Special Meeting, you may change your vote or revoke your proxy at any time before it is voted at the Special Meeting by:

If you have submitted a proxy, your virtual appearance at the Special Meeting will not have the effect of revoking your prior proxy; provided that you do not vote virtually or submit an additional proxy or revocation, which, in each case, will have the effect of revoking your proxy.

If you hold your shares of common stock in “street name,” you should contact your bank, broker or other nominee for instructions regarding how to change your vote. You may also vote virtually at the Special Meeting if you obtain a “legal proxy” from your bank, broker or other nominee.

Although it is not currently expected, the Special Meeting may be adjourned or recessed to a later date or dates, including for the purpose of soliciting additional proxies, if there are insufficient votes at the time of the Special Meeting to approve the proposal to adopt the Merger Agreement or if a quorum is not present at the Special Meeting. Other than an announcement to be made at the Special Meeting of the time, date and place of an adjourned meeting, an adjournment generally may be made without notice. Any adjournment or recess of the Special Meeting for the purpose of soliciting additional proxies will allow the stockholders who have already sent in their proxies to revoke them at any time prior to their use at the Special Meeting as adjourned or recessed.

The Board of Directors, after considering various factors described under the caption, “The Merger—Recommendation of the Board of Directors and Reasons for the Merger,” has unanimously: (i) determined that the Merger and the transactions contemplated thereby are advisable, fair to and in the best interests of Arena and the stockholders; (ii) approved and declared it advisable to enter into the Merger Agreement; (iii) directed that the adoption of the Merger Agreement be submitted to a vote of the stockholders at the Special Meeting; and (iv) subject to the terms and conditions of the Merger Agreement, resolved to recommend that the stockholders approve the adoption of the Merger Agreement and approve the Merger on the terms and subject to the conditions set forth therein.

Accordingly, the Board of Directors unanimously recommends, on behalf of Arena, that you vote: (i) “FOR” the adoption of the Merger Agreement; (ii) “FOR” the approval, on an advisory (non-binding) basis, of the Compensation Proposal; and (iii) “FOR” the approval of the Adjournment Proposal.

The expense of soliciting proxies will be borne by Arena. We have retained Alliance Advisors, LLC (“Alliance Advisors”), a proxy solicitation firm, to solicit proxies in connection with the Special Meeting at a cost of approximately $22,000 plus expenses. We will also indemnify Alliance Advisors against losses arising out of its provisions of these services on our behalf. In addition, we may reimburse banks, brokers and other nominees representing beneficial owners of shares for their expenses in forwarding soliciting materials to such beneficial owners. Proxies may also be solicited by our directors, officers and employees, personally or by telephone, email, fax, over the Internet or other means of communication. No additional compensation will be paid for such services.

Assuming timely satisfaction of necessary closing conditions, including obtaining the Requisite Vote, Arena is currently targeting to consummate the Merger in the first half of 2022, although Arena cannot assure completion by any particular date, if at all. Since the Merger is subject to a number of conditions, the exact timing of the Merger cannot be determined at this time.

If the Merger is completed, the shares of Arena’s common stock will be delisted from Nasdaq and deregistered under the Exchange Act, and shares of Arena’s common stock will no longer be publicly traded. As such, Arena will no longer file periodic reports with the SEC on account of Arena’s common stock.

Important Notice Regarding the Availability of Proxy Materials for the Stockholder Meeting to be Held on    , 2022

The proxy statement is available on the investor relations page of our website at http://invest.arenapharm.com/.

If you have any questions concerning the Merger, the Special Meeting or the accompanying proxy statement, would like additional copies of the accompanying proxy statement or need help voting your shares of common stock, please contact our proxy solicitor:

This discussion of the Merger is qualified in its entirety by reference to the Merger Agreement, which is attached to this proxy statement as Annex A and incorporated into this proxy statement by reference. You should carefully read and consider the entire Merger Agreement, which is the legal document that governs the Merger, because this document contains important information about the Merger and how it affects you.

Arena is a team with a singular purpose – deliver important medicines to patients. In a rapidly changing global market, Arena works with a sense of urgency every day to understand the needs of all its stakeholders, identify bold, sometimes disruptive, ideas to get medicines to patients, and relentlessly execute until it’s done. Arena’s common stock is listed on Nasdaq under the symbol “ARNA.” The principal executive offices of Arena are located at 136 Heber Avenue, Suite 204, Park City, Utah 84060, and its telephone number is (858) 453-7200.

Pfizer is a research-based, global biopharmaceutical company. Pfizer applies science and its global resources to bring therapies to people that extend and significantly improve their lives through the discovery, development, manufacture, marketing, sale and distribution of biopharmaceutical products worldwide. Pfizer works across developed and emerging markets to advance wellness, prevention, treatments and cures that challenge the most feared diseases of our time. Pfizer collaborates with healthcare providers, governments and local communities to support and expand access to reliable, affordable healthcare around the world.

Pfizer was incorporated under the laws of the State of Delaware. Pfizer’s principal executive offices are located at 235 East 42nd Street, New York, NY 10017, and its telephone number is (212) 733-2323.

Merger Sub is a Delaware corporation and a wholly owned subsidiary of Pfizer and was formed on December 6, 2021, solely for the purpose of engaging in the transactions contemplated by the Merger Agreement. Merger Sub has not engaged in any business activities other than in connection with the transactions contemplated by the Merger Agreement. Upon the completion of the Merger, Merger Sub will cease to exist and Arena will continue as the Surviving Corporation. The principal executive offices of Merger Sub are located at 235 East 42nd Street, New York, New York 10017, and its telephone number is (212) 733-2323.

Upon the terms and subject to the conditions of the Merger Agreement, Merger Sub will merge with and into Arena, with Arena continuing as the Surviving Corporation. As a result of the Merger, Arena will become a wholly owned subsidiary of Pfizer, and our common stock will no longer be publicly traded and will be delisted from Nasdaq. In addition, our common stock will be deregistered under the Exchange Act, and we will no longer file periodic reports with the SEC. If the Merger is completed, you will not own any shares of the capital stock of the Surviving Corporation.

The Effective Time will occur upon the filing of a certificate of merger with the Secretary of State of the State of Delaware (or at such later time as we, Pfizer and Merger Sub may agree in writing and specify in the certificate of merger).

If the Merger Agreement is not adopted by stockholders, or if the Merger is not completed for any other reason:

At the Effective Time, each share of common stock (other than (i) common stock owned by Arena as treasury stock, (ii) common stock owned by Pfizer or Merger Sub and (iii) any Dissenting Shares) outstanding as of immediately prior to the Effective Time will be cancelled and automatically converted into the right to receive the Merger Consideration, without interest thereon and subject to any withholding of taxes.

After the Merger is completed, you will have the right to receive the Merger Consideration in respect of each share of common stock that you own (subject to any withholding of taxes), but you will no longer have any rights as a stockholder (except that stockholders who properly exercise their appraisal rights will have a right to receive payment of the “fair value” of their shares as determined pursuant to an appraisal proceeding, as contemplated by Delaware law). For more information, please see the section of this proxy statement captioned “—Appraisal Rights.”

The Board of Directors, together with Arena senior management, and with the assistance of its outside advisors, frequently reviews Arena’s strategic and financial alternatives in light of developments in Arena’s business, the sectors in which it operates, and the economy and financial markets generally, as they, individually and together, may affect Arena’s long-term strategic goals and plans. Since early 2020, this assessment has also been informed by the current and prospective impact of the COVID-19 pandemic, including the emergence of new variants of the coronavirus that causes COVID-19. As part of this process, members of Arena’s senior management have engaged in business development and strategic discussions with participants in the biopharmaceutical and healthcare industries, all with the goal of enhancing value for stockholders, including by delivering the best possible treatments and services to patients and healthcare providers. Arena’s strategic discussions have focused on, among other things, strategic opportunities for business combinations, acquisitions, licensing transactions, commercial agreements and other financial and strategic alternatives for Arena, including continuing as a standalone company, with a view to enhance stockholder value.

On October 22, 2021, Mr. Amit D. Munshi, President and Chief Executive Officer of Arena, and Dr. Albert Bourla, Chairman and Chief Executive Officer of Pfizer, held a video conference that had been scheduled earlier that week at the request of Dr. Bourla. Dr. Bourla stated that Pfizer would be interested in acquiring Arena and would be prepared to execute a transaction by the end of the quarter but did not preview any valuation information. During the call, Dr. Bourla requested that Arena provide any available data for its ongoing ELEVATE UC-12 trial and ELEVATE UC- 52 trials that might inform Pfizer's proposal. Mr. Munshi responded that only blinded data would be available before the end of the year. Dr. Bourla concluded the conversation by noting that he would follow up with Mr. Munshi as soon as possible. Later that day, Mr. Munshi informed Dr. Garry Neil, Chairman of the Board of Directors, of his conversation with Dr. Bourla.

On October 27, 2021, Dr. Bourla indicated to Mr. Munshi that it was challenging for Pfizer to make a written proposal before reviewing the blinded ELEVATE UC-12 and ELEVATE UC-52 data. Dr. Bourla asked whether Arena would provide the information if Pfizer submitted a written letter of intent, exclusive of any price per share or other

valuation information. Mr. Munshi stated that Arena would not do so. Dr. Bourla asked Mr. Munshi to identify a price that would be sufficient for Arena to provide the requested information. Mr. Munshi declined to do so and indicated that he believed any proposal would need to be substantially higher than the 52-week intraday high of the trading price for shares of Arena common stock (which was $90.19 for the 52-week period ending October 27, 2021) in order to be considered by the Board of Directors. Dr. Bourla indicated that Pfizer would send a written proposal to Arena the next day. Mr. Munshi confirmed that he would notify the Board of Directors of receipt of such written proposal.

On October 28, 2021, Pfizer sent Arena an indication of interest, dated October 27, 2021, pursuant to which Pfizer proposed to acquire 100% of the outstanding common stock of Arena for $98.00 per share in cash (which we refer to as the “October 27 Proposal”).

On October 29, 2021, Mr. Munshi informed Dr. Bourla that the Board of Directors would meet later that day to discuss the October 27 Proposal. Mr. Munshi and Dr. Bourla discussed the appropriate contacts at Arena and Pfizer to coordinate the negotiation and execution of a non-disclosure agreement if authorized by the Board of Directors.

Later that day, the Board of Directors held a meeting with Arena senior management and representatives of Cooley LLP (“Cooley”), Arena’s outside legal counsel. During the meeting, Mr. Munshi described his conversations with Dr. Bourla and the October 27 Proposal. Representatives from Cooley summarized fiduciary duties attendant to any review of strategic alternatives, and Mr. Munshi reviewed a summary of certain publicly available financial information prepared by Guggenheim Securities (from which no representatives were present at the meeting) regarding certain similar acquisition transactions. The Board of Directors and Arena senior management then discussed the price proposed by Pfizer in the October 27 Proposal and how it compared to premiums previously paid by Pfizer and to premiums paid in similar recent pre-commercial biopharmaceutical transactions. The Board of Directors also discussed the inherent uncertainties in Arena’s business as a standalone company (including those relating to the ELEVATE UC-12 and ELEVATE UC-52 trials expected to read out in 2022), the premium to Arena’s current stock price represented by the price proposed in the October 27 Proposal and considerations for assessing strategic alternatives at that time, including the need for an assessment of Arena’s standalone plan and future outlook in order to assess the relative merits of Arena continuing to operate independently and pursuing its current business and financial plans on a standalone basis. The Board of Directors also noted that a draft of Arena’s Long Range Plan was scheduled to be reviewed by the Board of Directors the following week. Based on the discussion at this meeting, the Board of Directors determined that although it would expect to seek to negotiate a higher price per share if it were to consider entering into a transaction with Pfizer, it was advisable to permit Pfizer to proceed with limited due diligence in order to allow it to improve its proposal. Accordingly, the Board of Directors approved entering into a non-disclosure agreement with Pfizer and providing limited diligence through a management presentation, including a summary of the blinded ELEVATE UC-12 and ELEVATE UC-52 data requested by Dr. Bourla. The Board of Directors further directed Arena senior management to update and finalize Arena’s Long Range Plan for review by the Board of Directors at its next meeting.

At this meeting, the Board of Directors also discussed the potential benefits and risks associated with contacting additional third parties regarding interest in a potential transaction with Arena and which third parties could reasonably be expected to have both financial ability and strategic interest in a potential transaction with Arena, including third parties that previously expressed interest in Arena’s business. The Board of Directors determined to proceed with initial, preliminary outreach to selected third parties and authorized Arena senior management to contact Party A, a pharmaceutical company, at that time. The Board of Directors discussed reaching out to Party B, another pharmaceutical company, and determined based on recent discussions that because Party B was more interested in a collaboration agreement than a potential transaction to acquire Arena, it would not be advisable to reach out to Party B. The Board of Directors also directed Arena senior management to prepare additional information regarding third parties that could potentially be contacted for further discussion at a subsequent meeting.

Later that day, following the Board of Directors meeting, Mr. Vincent Aurentz, Executive Vice President and Chief Business Officer of Arena, contacted representatives of Party A to inquire as to whether Party A would have interest in acquiring Arena. At the end of the call, Party A indicated they would contact Mr. Aurentz in the coming days.

On October 30, 2021, at the request of the Board of Directors, Guggenheim Securities provided information about its relationships with Pfizer over the last five years. Representatives of Guggenheim Securities had verbally summarized this information for Arena senior management before the meeting of the Board of Directors the prior day. The information provided by Guggenheim Securities indicated that during the five year period prior to October 30, 2021, Guggenheim Securities had been engaged by Pfizer with respect to various matters unrelated to the Merger in

respect of which Guggenheim Securities received compensation, including five separate completed transactions on which Guggenheim Securities acted on behalf of Pfizer during this period. The information further indicated Guggenheim Securities received compensation of approximately $110 million to $115 million in the aggregate from Pfizer during this five year period. The Board of Directors had discussed the verbal summary of this information at its October 29 meeting and decided to further review at a subsequent meeting what role, if any, would be appropriate for Guggenheim Securities in connection with the proposed transaction. The Board of Directors then instructed Arena senior management to consider an additional financial advisor for consideration by the Board of Directors.

On October 31, 2021, Arena and Pfizer entered into an amendment to an existing non-disclosure agreement between Arena and Pfizer that was previously entered into in connection with a potential licensing transaction that was subsequently abandoned. The amendment included a standstill provision for a 12 month period and a non-solicit provision for a six month period. The standstill provision included customary exclusions, including to permit Pfizer to approach Arena privately and a fall away provision upon the entry into or public announcement of certain acquisition transactions.

On November 1, 2021, Arena held a management presentation for Pfizer during which Arena presented limited diligence information related to the safety, efficacy and competitive landscape of etrasimod, including blinded data available with respect to the ongoing ELEVATE UC-12 and ELEVATE UC-52 trials and completed trials relating to ulcerative colitis, or “UC,” and atopic dermatitis, or “AD”.

The same day, the Board of Directors held a meeting with Arena senior management and representatives of Cooley to discuss the engagement of one or more financial advisors. Arena senior management invited Evercore to the meeting to receive advice from an additional financial advisor regarding Pfizer’s proposal and a potential strategic transaction and to evaluate their experience and capabilities relevant to a potential strategic transaction. After discussions, the Board of Directors directed Arena senior management in an executive session at which Evercore was not present to begin negotiating engagement letters with each of Evercore and Guggenheim Securities for consideration by the Board at a subsequent meeting.

On November 2, 2021, Ms. Deborah Baron, Senior Vice President, Worldwide Business Development and Mr. Shay Tamari, Business Development Group Lead, Inflammation & Immunology from Pfizer contacted Mr. Aurentz following the initial management presentation held on November 1, 2021 to provide feedback and request certain additional due diligence information. In response to such request, Mr. Aurentz indicated that additional due diligence information would be made available only upon receipt of a revised indication of interest from Pfizer reflecting an increased price per share from the price proposed in the October 27 Proposal.

On November 3, 2021, a representative from Party A contacted Mr. Aurentz to inform Arena that Party A would not be able to pursue a transaction with Arena at that time due to its focus on other strategic priorities.

Later that day, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities. Representatives of Evercore summarized for the Board of Directors their recommendations regarding a strategic process designed to maximize value for Arena stockholders and presented their preliminary views on value. The Board of Directors then reviewed Arena’s Long Range Plan, which included the Projections. For a detailed discussion of the Projections, please see below under the caption “The Merger—Financial Projections”. In connection with reviewing the Long Range Plan, the Board of Directors engaged in further discussion regarding the uncertainties inherent in Arena’s standalone business plan, including the potential outcomes of clinical trials and the resulting ability to access adequate capital depending on those outcomes, and uncertainties in remaining a standalone business. The Board of Directors then directed Evercore and Guggenheim Securities to use the Projections in materials presented to the Board of Directors, including as part of any valuation analysis. Mr. Aurentz informed the Board of Directors that (i) Party A had declined to consider a potential transaction with Arena and (ii) Pfizer had requested to have access to additional diligence information and that in response to such request, he indicated that additional information would only be made available upon an increase in price per share from the price proposed in the October 27 Proposal. The Board of Directors further discussed the potential benefits and risks associated with contacting additional third parties regarding their potential interest in a transaction with Arena, including by reviewing a summary prepared by Arena senior management and Evercore and Guggenheim Securities of additional third parties and considerations relevant to their potential interest in a transaction with Arena.

On November 4, 2021, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities. Representatives of each of Evercore and Guggenheim Securities provided a process update and presented their perspectives on the current biopharmaceutical market environment as

well as their preliminary financial analyses. During the subsequent executive session of the meeting at which Evercore and Guggenheim Securities were not present, the Board of Directors continued to discuss the potential strategic transaction, including the potential benefits and risks associated with contacting additional third parties regarding potential interest in a transaction with Arena, as well as alternatives to the potential transaction, including Arena continuing as a standalone company. The Board of Directors directed Arena senior management to work with Evercore and Guggenheim Securities to target those parties believed most likely to be interested in and able to acquire Arena. In addition, the Board of Directors determined to formally engage each of Evercore and Guggenheim Securities in connection with the proposed transaction. In making this determination, the Board of Directors considered, among other things, Guggenheim Securities’ longstanding relationship and familiarity with Arena’s business and its knowledge of industry participants as well as Guggenheim Securities’ position as an internationally recognized investment banking, financial advisory and securities firm. The Board of Directors also considered that Evercore is an internationally recognized investment banking, financial advisory and securities firm with expertise in the biopharmaceutical sector that is regularly engaged in the valuation and financial assessment of businesses and securities in connection with mergers and acquisitions. Additionally, the Board of Directors considered the disclosure previously provided by Guggenheim Securities regarding its relationships with Pfizer in the past five years and similar information provided by Evercore, which indicated that Evercore had not been engaged by Pfizer in the past five years. The Board of Directors discussed the terms of the engagement letters with each of Evercore and Guggenheim Securities, including the related fees, and approved the terms of the engagements with each of Evercore and Guggenheim Securities.

Later that day, Arena executed an engagement letter with each of Evercore and Guggenheim Securities formalizing the engagement of each to act as a financial advisor to the Board of Directors in connection with a potential strategic transaction.

On November 8, 2021, Dr. Bourla indicated to Mr. Munshi that Pfizer would make a revised proposal. Later that day, Pfizer sent Arena a revised indication of interest for $105.00 per share in cash (which we refer to as the “November 8 Proposal”). The November 8 Proposal indicated that it was subject to due diligence, which Pfizer would require approximately three weeks to complete following receipt of full diligence access.

On November 9, 2021, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities to discuss the November 8 Proposal. The Board of Directors engaged in discussion regarding the terms of the November 8 Proposal and determined that although the Board of Directors would seek to negotiate additional value for Arena stockholders prior to further considering Pfizer’s proposal, the November 8 Proposal was a basis on which the Board of Directors was willing to allow Pfizer to conduct additional due diligence to enable it to potentially make an improved proposal. The Board of Directors also further discussed the potential benefits and risks of contacting additional third parties regarding potential interest in a transaction with Arena. The Board of Directors directed Arena senior management and representatives of Evercore and Guggenheim Securities to pursue additional outreach to Party C and Party D, each a pharmaceutical company.

Following the Board of Directors meeting on November 9, 2021, Mr. Munshi indicated to Dr. Bourla that Pfizer would need to improve the terms of its November 8 Proposal and suggested that in addition to a higher upfront purchase price, a transaction involving contingent value rights, or “CVRs,” could deliver additional value to Arena stockholders. Dr. Bourla indicated that Pfizer was not inclined to use CVRs but that it could potentially proposal a higher price per share depending upon the results of its due diligence. Consistent with the Board of Directors’ determination earlier that day, Mr. Munshi agreed to move forward with providing additional diligence information. Mr. Munshi and Dr. Bourla agreed to speak again during the week of November 14, 2021 to further discuss price.

On November 9, 2021, representatives of Evercore and Guggenheim Securities contacted a representative of Party C regarding interest in a potential transaction with Arena. Party C indicated they would contact Evercore and Guggenheim Securities shortly.

On November 10, 2021, representatives of Evercore and Guggenheim Securities spoke with a representative of Party D regarding interest in a potential transaction with Arena. The next day, a representative of Party D contacted Evercore and Guggenheim Securities to indicate that Party D was not interested in a potential transaction with Arena at that time.

Also on November 10, 2021, Pfizer sent Arena an initial due diligence request list, and Arena opened a virtual data room to Pfizer, which included, among other things, certain information regarding Arena’s intellectual property, certain tax information items and data and certain other information regarding both historical and ongoing clinical trials.

On November 11, 2021, Party C contacted representatives of Evercore and Guggenheim Securities and noted that they were interested in exploring a potential transaction and requested a non-disclosure agreement.

On November 11, 2021, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities. Representatives of each of Evercore and Guggenheim Securities informed the Board of Directors that (i) Party D stated that it was not interested in considering a transaction at that time and (ii) Party C indicated that it was interested in exploring a potential transaction and requested a non-disclosure agreement. Representatives from Evercore and Guggenheim Securities summarized Party C’s diligence requests and a request for a management presentation. Arena senior management indicated that it was willing to share blinded data with a small number of individuals from Party C, in addition to high priority diligence items, so that Party C would be in a position to submit a preliminary indication of interest. Representatives of each of Evercore and Guggenheim Securities also informed the Board of Directors that access to the virtual data room had been granted to Pfizer the previous day.

On November 12, 2021, Arena and Party C executed a non-disclosure agreement, which included a standstill provision for a 12 month period and a non-solicit provision for a 12 month period. The standstill provision included customary exclusions such as permitting Party C to approach Arena privately and confidentially and a fall away provision upon the entry into or public announcement of certain acquisition transactions.

Later that day, certain members of the Arena legal team, along with Cooley and Arena’s outside intellectual property counsel, held a legal diligence call and an intellectual property diligence call with representatives of Pfizer and Ropes & Gray LLP (“Ropes & Gray”), Pfizer’s outside legal counsel.

On November 13, 2021, representatives of Evercore and Guggenheim Securities had a call with Party C where Party C requested additional diligence information.

On November 15, 2021, Mr. Munshi and Dr. Bourla spoke regarding Pfizer’s the November 8 Proposal and deal process and timing considerations. Dr. Bourla indicated that Pfizer’s due diligence process was ongoing. Also on November 15, 2021, Party C conducted a diligence call with Arena management with respect to the blinded data and Arena’s clinical development plans.

On November 16, 2021, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities. Mr. Munshi provided an update on the strategic process and discussed his November 15, 2021 conversation with Dr. Bourla. Arena senior management then provided an update regarding Pfizer’s diligence to date. Representatives of each of Evercore and Guggenheim Securities summarized the status of outreach to other third parties regarding a potential transaction, including the status of discussions with Party C. The Board of Directors discussed the potential benefits and risks of pursuing additional outreach to other potential buyers, in the pharmaceutical industry. Based on that discussion and the discussion at prior meetings, as well as the fact that multiple third parties had been contacted to date, the Board of Directors determined not to contact additional third parties at that time.

The same day, Mr. Munshi emailed Dr. Bourla stating that although Arena and Pfizer were apart on value, Arena would move forward in negotiations and requested an initial draft of the Merger Agreement.

On November 17, 2021, Ropes & Gray sent an initial draft merger agreement to Cooley. The draft Merger Agreement proposed, among other things, a one-step merger structure, obligations by Pfizer to use commercially reasonable efforts to obtain required regulatory approvals, an unspecified termination fee payable by Arena to Pfizer in certain circumstances, no reverse termination fee payable by Pfizer to Arena, multiple closing conditions relating to receipt of regulatory approvals and no carveouts to the definition of Company Material Adverse Effect relating to the results of clinical trials. The same day, Arena and Pfizer senior management had a diligence call to discuss trial design and clinical questions relating to the AD trial.

On November 17, 2021, a representative of Party C contacted representatives of Evercore and Guggenheim Securities to convey that it would not be submitting an indication of interest at that time.

On November 18, 2021, Mr. Munshi and Dr. Bourla spoke regarding the draft merger agreement. Mr. Munshi summarized for Dr. Bourla certain provisions that were not acceptable to Arena. Dr. Bourla requested that Mr. Munshi direct Cooley to share a draft merger agreement that would address the concerns raised by Mr. Munshi.

On November 18, 2021, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities to review the transaction process with Pfizer and the status of outreach to third parties. Representatives of Evercore and Guggenheim Securities confirmed that Party C had indicated that it would not be submitting an indication of interest at that time. Representatives of Cooley summarized key terms of the draft merger agreement provided by Ropes & Gray on November 17, 2021. Mr. Munshi updated the Board of Directors that he and Dr. Bourla had agreed that Cooley would prepare a revised agreement on behalf of Arena with terms acceptable to the Board of Directors. Representatives of Cooley discussed with the Board of Directors considerations regarding certain terms of the merger agreement, including those regarding a tender offer or merger structure, regulatory efforts obligations, closing conditions, and termination fees. The Board of Directors gave direction based on this discussion regarding terms to be included in the draft merger agreement being prepared by Cooley.

On November 19, 2021, Arena issued a press release disclosing that it had achieved its target enrollment in Study A of the Phase 2/3 CULTIVATE trial for etrasimod.

Later that day, Cooley sent Ropes & Gray a draft merger agreement, which proposed, among other things, a two-step tender offer transaction structure, an Arena termination fee of 2.25% of the transaction value, regulatory efforts obligations requiring Pfizer to take all actions necessary or advisable to obtain any required regulatory approvals and broader carveouts to the definition of Company Material Adverse Effect, including for adverse events or outcomes of key clinical trials.

On November 20, 2021, Dr. Bourla indicated to Mr. Munshi that based on its due diligence to date, Pfizer no longer expected to be able to offer the price indicated in the November 8 Proposal. Dr. Bourla asked Mr. Munshi whether there might be any alternative transaction structures (such as a license of Arena’s assets outside the United States) or alternative price structures acceptable to Arena.

On November 21, 2021, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities. Mr. Munshi summarized for the Board of Directors his conversation with Dr. Bourla the previous day. The Board of Directors discussed whether to consider alternative transaction structures or alternative price structures that could provide additional value to Arena stockholders. Based on this discussion, it was the consensus of the Board of Directors that Arena should continue to engage in discussions with Pfizer and that other than a transaction that included CVRs tied to future achievement of certain milestones by the Arena business, an alternative structure would not be in the best interests of Arena and its stockholders. The Board of Directors agreed to take a brief recess from the meeting and directed Mr. Munshi to contact Dr. Bourla to indicate that the Board of Directors would consider a proposal involving CVRs.

During that recess, Mr. Munshi contacted Dr. Bourla to indicate that the Board of Directors would consider a proposal involving CVRs and that other transaction structures were not of interest to the Board of Directors at that time. Following that conversation, the meeting of the Board of Directors reconvened and Mr. Munshi summarized his conversation with Dr. Bourla.

On November 24, 2021, the Omicron variant of the coronavirus that causes COVID-19 was first reported to the World Health Organization, which designated it as a “Variant of Concern” on November 26, 2021.

That same day, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities to discuss the transaction process.

On November 26, 2021, Mr. Munshi and Dr. Bourla spoke twice. During these conversations, Dr. Bourla informed Mr. Munshi that Pfizer did not expect to be able to offer the amount proposed in the November 8 Proposal based on the results of its due diligence review, which remained ongoing. Dr. Bourla indicated that Pfizer was willing to continue to evaluate a transaction at a price of $95.00 per share plus a per share CVR or at a price of $100.00 per share without CVRs.

On November 27, 2021, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities. Mr. Munshi updated the Board of Directors on his conversations with Dr. Bourla the previous day. The Board of Directors discussed whether to continue discussions

with Pfizer, taking into account, among other things, Mr. Munshi’s most recent conversations with Dr. Bourla, the inherent uncertainties in remaining a standalone company, including the potential outcomes of clinical trials, the resulting ability to access capital depending on those outcomes, the recent lack of interest expressed by Party C and Party D, and the potential for lack of interest among other potential acquirors depending on the outcomes of pending clinical trials. The Board of Directors also received information from Arena senior management regarding the Omicron variant of the coronavirus that causes COVID-19 that had been reported to the World Health Organization and discussed the potential risks Arena may face in light of the new variant, including potential impacts on its ability to conduct clinical trials on the timelines then contemplated. Following this discussion, the Board of Directors directed Mr. Munshi to contact Dr. Bourla to indicate that Arena would continue to negotiate the terms of the Merger Agreement and allow Pfizer to progress its due diligence without expressing a view on price at that time. The Board of Directors further directed the Arena senior management team and Arena’s legal and financial advisors to engage in discussions with Pfizer and its legal and financial advisors to determine whether there would be terms on which Pfizer would be willing to transact with Arena that would be acceptable to the Board of Directors. The Board of Directors indicated that certainty of closing, including appropriate carveouts to the definition of Company Material Adverse Effect relating to clinical trials, appropriate regulatory efforts obligations, an appropriate reverse termination fee and termination fee, an outside date not substantially longer than one year and the ability to adequately operate Arena’s business between signing and closing of a transaction would be essential factors in the Board’s consideration of any transaction.

On November 28, 2021, Mr. Aurentz spoke with Mr. Shay Tamari, Business Development Group Lead, Inflammation & Immunology at Pfizer. Messrs. Aurentz and Tamari agreed to connect representatives of Evercore and Guggenheim Securities with representatives of BofA Securities, Inc. (“BofA Securities”) and Centerview Partners LLC (“Centerview”), financial advisors to Pfizer, to facilitate further discussion of certain key transaction terms, including the outside date, termination fee, reverse termination fee, regulatory efforts covenants and closing conditions relating to regulatory approvals. Mr. Aurentz and Mr. Tamari also agreed to progress in parallel the negotiation of other terms of the Merger Agreement and completion of Pfizer’s due diligence.

Later that day, Ropes & Gray sent Cooley a draft Merger Agreement, which was substantially similar to the draft Ropes & Gray shared on November 17, 2021, except that the draft included a reverse termination fee equal to the then unspecified termination fee payable by Pfizer to Arena. The draft Merger Agreement also included carveouts to the definition of Company Material Adverse Effect for adverse events or outcomes relating to the ELEVATE UC-12 and ELEVATE UC-52 trials.

On November 30, 2021, representatives of Evercore and Guggenheim Securities held a meeting with BofA Securities and Centerview to convey the proposal on certain key terms of the Merger Agreement developed by Arena senior management and its legal and financial advisors based on the guidance provided by the Board at the November 27 meeting. Representatives of Evercore and Guggenheim Securities proposed (i) an initial outside date of March 15, 2022 that could be extended to December 15, 2022 by either party, (ii) that on March 15, 2022, either party could terminate the Merger Agreement and Arena would receive a $350 million reverse termination fee from Pfizer in certain circumstances relating to the failure of certain regulatory approvals to be obtained, (iii) that if either party extended the proposed outside date, then Pfizer would advance $750 million to Arena as a loan at the time of the extension and if the Merger Agreement was subsequently terminated in certain circumstances relating to the failure of certain regulatory approvals to be obtained, then the $750 million loan was to be forgiven and (iv) stronger regulatory efforts covenants and closing conditions relating to regulatory approvals.

Later that day, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities. Mr. Munshi provided an update on the transaction process. Representatives of the legal and financial advisors summarized the terms proposed during the discussion between both parties’ financial advisors earlier that day, including considerations relating to the proposed outside date, reverse termination fee, loan and regulatory efforts covenants.

During the period from November 30, 2021 through December 2, 2021, representatives of Arena senior management and Pfizer management and their respective legal and financial advisors continued to engage in discussions regarding the terms of the Merger Agreement, the amounts of the termination fee and reverse termination fee and the circumstances in which they would be payable, Pfizer’s regulatory efforts obligations and regulatory closing conditions, Arena’s ability to pursue financing between signing and closing and the exceptions to the definition of Company Material Adverse Effect.

On December 2, 2021, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities. Representatives from each of Evercore and Guggenheim Securities gave an update on the transaction process, including a summary of their discussions over the prior few days with BofA Securities and Centerview. Representatives of Cooley summarized their discussions over the same period with Ropes & Gray. Representatives from each of Evercore and Guggenheim Securities then presented an updated financial analysis of the potential transaction with Pfizer. Following the presentations from each of Evercore and Guggenheim Securities, the Board of Directors met in an executive session and discussed views regarding price and other transaction terms. At the conclusion of the meeting, based on the further discussion by the Board of Directors of certain factors deemed relevant by the Board of Directors, including the inherent uncertainties in remaining a standalone company, the potential outcomes of clinical trials, the resulting ability to access capital depending on those outcomes and the Omicron variant of the coronavirus that causes COVID-19 and the potential risks Arena may face in light of the new variant, the Board of Directors directed Mr. Munshi to continue to negotiate with Pfizer, with the assistance of Arena’s legal and financial advisors.

Later that day, Cooley sent Ropes & Gray a revised draft Merger Agreement and an initial draft of the disclosure schedules. From December 2, 2021 to immediately prior to signing the Merger Agreement on December 12, 2021, the parties and their respective legal and financial advisors continued to negotiate the terms of the Merger Agreement, including, among other things, the amounts of the termination fee and reverse termination fee and the circumstances in which they would be payable, Pfizer’s regulatory efforts obligations and regulatory closing conditions, Arena’s ability to obtain financing between signing and closing and the exceptions to the definition of Company Material Adverse Effect, in all cases based on the views of the Board of Directors discussed with Arena senior management and Arena’s legal and financial advisors. During this period, Cooley and Ropes & Gray also exchanged multiple revised drafts of the Merger Agreement.

On December 7, 2021, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities. Arena senior management gave an update on the transaction process and an update regarding the negotiation of the Merger Agreement, including a summary of the terms of the draft Merger Agreement and material open items based on negotiations to date. The Board of Directors discussed the draft Merger Agreement and directed Arena senior management, specifically Mr. Aurentz, to negotiate certain terms, including price and matters relating to the reverse termination fee, Pfizer’s regulatory efforts obligations, the scope of the exceptions to the definition of Company Material Adverse Effect relating to clinical trials and the termination fee in accordance with the views expressed by the Board of Directors.

On December 9, 2021, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities to further discuss the terms of the draft Merger Agreement based on negotiations to date and the overall status of discussions with Pfizer.

Also on December 9, 2021, Mr. Aurentz spoke with Ms. Baron to convey Arena’s proposal regarding certain terms of the draft Merger Agreement as directed by the Board of Directors on December 7th. In addition, Mr. Aurentz provided a written summary of Arena’s proposal with respect to key terms to Ms. Baron. As part of this proposal, Mr. Aurentz indicated that Pfizer should propose an increase to $105.00 per share, the price included in the November 8 Proposal for consideration by the Board of Directors.

On December 10, 2021, Ms. Baron contacted Mr. Aurentz to convey Pfizer’s position regarding certain key terms of the Merger Agreement, including Pfizer's proposal of $100.00 per share.. Later that day, Ms. Baron contacted Mr. Aurentz again to confirm to Arena that $100.00 per share was Pfizer’s best and final proposal (which we refer to as the “December 10 Proposal”).

On December 11, 2021, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities. Messrs. Munshi and Aurentz summarized the discussions with Pfizer over the past two days, including the December 10 Proposal, which represented Pfizer’s best and final proposal. Representatives from Cooley summarized the fiduciary duties applicable to the Board of Directors in the context of the proposed transaction. Representatives from Cooley then summarized the latest draft of the Merger Agreement, which had been sent to Cooley by Ropes & Gray earlier that day to reflect the conversations the prior day between Mr. Aurentz and Ms. Baron, including the provisions relating to the reverse termination fee, Pfizer’s regulatory efforts obligations, exceptions to the definition of Company Material Adverse Effect relating to

clinical trials and the termination fee. Representatives from each of Evercore and Guggenheim Securities presented their financial analysis of the potential transaction with Pfizer. Following this discussion, the Board of Directors directed Arena senior management and the legal and financial advisors to finalize the terms of the Merger Agreement for consideration by the Board of Directors.

Throughout the remainder of December 11 and December 12, 2021, Cooley and Ropes & Gray worked to finalize the Merger Agreement and related documents.

On December 12, 2021, the Board of Directors held a meeting with Arena senior management and representatives of Cooley, Evercore and Guggenheim Securities. At this meeting, Evercore reviewed with the Board of Directors its financial analysis of the Merger Consideration and delivered to the Board of Directors its oral opinion (which was subsequently confirmed in writing) to the effect that, as of that date and based upon and subject to the assumptions, limitations, qualifications and conditions described in Evercore’s opinion, the Merger Consideration to be received by the holders of shares of common stock of Arena in the Merger was fair, from a financial point of view, to such holders. Also at this meeting of the Board of Directors, Guggenheim Securities reviewed its financial analysis of the Merger Consideration and rendered its oral opinion (which was subsequently confirmed in writing), to the Board of Directors to the effect that, as of that date and based on and subject to the assumptions, limitations, qualifications and conditions described in Guggenheim Securities’ opinion, the Merger Consideration in connection with the Merger was fair, from a financial point of view, to holders of common stock of Arena. For more information about the opinions of Evercore and Guggenheim Securities, see below under the captions “The Merger—Opinion of Evercore Group L.L.C.” and “The Merger—Opinion of Guggenheim Securities, LLC”.

Following the delivery of the opinions of Evercore and Guggenheim Securities, representatives of Cooley reviewed with the Board of Directors material terms of the proposed final Merger Agreement. For more information concerning the terms of the Merger Agreement, see the section titled “Proposal 1: Adoption of the Merger Agreement.” Representatives of Cooley answered questions from members of the Board of Directors regarding the terms of the Merger Agreement and the potential risks associated with the completion of the Merger based on the terms of the Merger Agreement. After the presentation by Cooley, the Board of Directors continued to discuss the potential transaction with Pfizer, Arena’s various alternatives (including whether to continue to operate the business on a standalone basis) and the reasons that the Board of Directors determined that the proposed Merger with Pfizer, Merger Agreement and other transactions contemplated thereby were advisable and in the best interests of Arena and its stockholders. For more information concerning the factors that the Board of Directors considered, see the section titled “The Merger—Recommendation of the Board of Directors and Reasons for the Merger.” Following that discussion, the Board of Directors unanimously determined that the Merger, the Merger Agreement and the other transactions contemplated thereby were advisable, fair to and in the best interests of Arena and its stockholders, and authorized and directed Arena senior management to execute the final Merger Agreement and related definitive documents with Pfizer.

Later that day, Arena and Pfizer executed the Merger Agreement.

On December 13, 2021, prior to the opening of trading on the U.S. stock markets, Arena and Pfizer issued a joint press release announcing the execution of the Merger Agreement.

The Board of Directors has unanimously: (i) determined that the Merger and the transactions contemplated thereby are advisable, fair to and in the best interests of Arena and the stockholders; (ii) approved and declared it advisable to enter into the Merger Agreement; (iii) directed that the adoption of the Merger Agreement be submitted to a vote of the stockholders at the Special Meeting; and (iv) subject to the terms and conditions of the Merger Agreement, resolved to recommend that the stockholders approve the adoption of the Merger Agreement and approve the Merger on the terms and subject to the conditions set forth therein.

The Board of Directors unanimously recommends, on behalf of Arena, that you vote: (i) “FOR” the adoption the Merger Agreement; (ii) “FOR” the approval, on an advisory (non-binding) basis, of the Compensation Proposal; and (iii) “FOR” the approval of the Adjournment Proposal.

In the course of reaching its determination and recommendation, the Board of Directors consulted with Arena management, Cooley and its financial advisors, Evercore and Guggenheim Securities. The Board of Directors considered the following reasons (which are not listed in any relative order of importance), all of which it viewed as generally supporting its (i) determination that the Merger and the transactions contemplated thereby are advisable, fair to and in the best interests of Arena and its stockholders; (ii) approval of and declaration that it is advisable to enter into the Merger Agreement; (iii) direction that the adoption of the Merger Agreement be submitted to a vote of Arena’s stockholders at the Special Meeting; and (iv) subject to the terms and conditions of the Merger Agreement, resolution to recommend that Arena’s stockholders approve the adoption of the Merger Agreement and approve the Merger on the terms and subject to the conditions set forth therein:

The Board of Directors assessed Arena’s prospects for substantially increasing stockholder value as a standalone company in excess of the Merger Consideration, given the risks and uncertainties in Arena’s business, including:

The Board of Directors also took into consideration that as a standalone company Arena would need to seek additional funding through future equity, royalty and/or debt financings or additional collaborations or strategic partnerships, and any such fundraising could have a highly dilutive effect on Arena’s existing stockholders, could require Arena to enter into restrictive covenants, might only be available on unfavorable terms given the recent downward trend in the biopharmaceutical financial markets, or might not be available at all.

The Board of Directors also considered a number of uncertainties and risks concerning the Merger, including the following (which are not listed in any relative order of importance):

The foregoing discussion of reasons for the recommendation to adopt the Merger Agreement and approve the Merger and the transactions contemplated thereby addresses the reasons considered by the Board of Directors in consideration of its recommendation. In view of the wide variety of reasons considered by the Board of Directors in connection with its evaluation of the Merger and the complexity of these matters, the Board of Directors did not find it practicable to, and did not, quantify or otherwise assign relative weights to the specific reasons considered in reaching its determination and recommendation. Rather, in considering the information and reasons described above, individual members of the Board of Directors each applied his or her own personal business judgment to the process and may have given differing weights to differing factors. The Board of Directors based its unanimous recommendation on the totality of the information presented. The explanation of the reasons and reasoning set forth above contain forward-looking statements that should be read in conjunction with the section of this proxy statement entitled “Forward-Looking Statements.”

The Projections included in this document have been prepared by, and are the responsibility of, Arena senior management. KPMG LLP has not audited, reviewed, examined, compiled nor applied agreed-upon procedures with respect to the accompanying Projections and, accordingly, KPMG LLP does not express an opinion or any other form of assurance with respect thereto. The KPMG LLP report incorporated by reference relates to Arena’s previously issued historical financial statements. It does not extend to the Projections and should not be read to do so.

The Projections reflect estimates and assumptions made by Arena senior management with respect to general business, economic, competitive, regulatory and other market and financial conditions and other future events, all of which are difficult to predict and many of which are beyond Arena’s control. In particular, the Projections, while presented with numerical specificity, necessarily were based on numerous variables and assumptions that are inherently uncertain. Because the Projections cover multiple years, by their nature, they become subject to greater uncertainty with each successive year and are unlikely to anticipate each and every circumstance that could have an effect on Arena’s business and its results of operations. The Projections were developed solely using the information available to Arena senior management at the time they were created and reflects assumptions as to certain business decisions that are subject to change. Important factors that may affect actual results or that may result in the Projections not being achieved include, but are not limited to, the ability to generate revenue for each of etrasimod indications, ralinepag and other Arena pipeline assets, the effect of regulatory actions, the decisions of third-party partners, the ability to out-license products, success of clinical testing, the effect of global economic conditions, including COVID-19, and increases in regulatory oversight and other risk factors described in Arena’s annual report on Form 10-K for the fiscal year ended December 31, 2020, subsequent quarterly reports on Form 10-Q and current reports on Form 8-K. The Projections also reflect assumptions as to certain business decisions that are subject to change. Modeling and forecasting the future in the biopharmaceutical industry, in particular, is a highly speculative endeavor.

None of Arena, Pfizer or any of their respective affiliates, advisors or other representatives makes any representation to any stockholder regarding the validity, reasonableness, accuracy or completeness of the Projections or the ultimate performance of Arena relative to the Projections. The inclusion of the Projections in this proxy statement does not constitute an admission or representation of Arena that the Projections or the information contained therein is material. Except as required by applicable law, neither Arena nor any of its affiliates intends to, and each of them disclaims any obligation to, update, correct or otherwise revise the Projections if any or all of them have changed or change or otherwise have become, are or become inappropriate (even in the short term). These considerations should be taken into account if evaluating the Projections, which were prepared as of an earlier date.

The Projections should be evaluated, if at all, in conjunction with the historical financial statements and other information regarding Arena in its public filings with the SEC. The Projections were developed by Arena senior management on a standalone basis without giving effect to the Merger and the other transactions contemplated by the

Merger Agreement, and therefore the Projections do not give effect to the proposed Merger or any changes to Arena’s operations or strategy that may be implemented after the consummation of the Merger, including any costs incurred in connection with the proposed Merger. Furthermore, the Projections do not take into account the effect of any failure of the proposed Merger to be completed and should not be viewed as accurate or continuing in that context.

The Projections further reflect subjective judgment in many respects and, therefore, are susceptible to multiple interpretations and periodic revisions based on actual experience and business developments. The inclusion of the Projections should not be regarded as an indication that Arena or anyone who received the Projections then considered, or now considers, the Projections to be necessarily predictive of actual future events, and this information should not be relied upon as such. Arena senior management views the Projections as being subject to inherent risks and uncertainties associated with such long-range projections.

EBIT and unlevered free cash flow contained in the Projections set forth below are each “non-GAAP financial measures,” which are financial performance measures that are not calculated in accordance with GAAP. These non-GAAP financial measures should not be viewed as a substitute for GAAP financial measures and may be different from non-GAAP financial measures used by other companies. Furthermore, there are limitations inherent in non-GAAP financial measures because they exclude charges and credits that are required to be included in a GAAP presentation. Accordingly, these non-GAAP financial measures should be considered together with, and not as an alternative to, financial measures prepared in accordance with GAAP.

The information and table set forth below is included solely to give Arena stockholders access to certain of the financial projections that were made available to the Board of Directors, Evercore and Guggenheim Securities and is not included in this proxy statement in order to influence any stockholder’s decision to vote with respect to the adoption of the Merger Agreement or for any other purpose:

Arena retained Evercore to act as its financial advisor in connection with the Merger. As part of this engagement, Arena requested that Evercore evaluate the fairness, from a financial point of view, of the Merger Consideration to be received by the holders of common stock. At a meeting of the Board of Directors held on December 12, 2021, Evercore rendered to the Board of Directors its opinion to the effect that, as of December 12, 2021 and based upon and subject to the assumptions, limitations, qualifications and conditions described in Evercore’s opinion, the Merger Consideration to be received by the holders of common stock in the Merger was fair, from a financial point of view, to such holders.

The full text of the written opinion of Evercore, dated as of December 12, 2021, which sets forth, among other things, the procedures followed, assumptions made, matters considered and qualifications and limitations on the scope of review undertaken in rendering its opinion, is attached as Annex B to this proxy statement and is incorporated herein by reference. Arena encourages you to read this opinion carefully and in its entirety. Evercore’s opinion was addressed to, and provided for the information and benefit of, the Board of Directors (in its capacity as such) in connection with its evaluation of the proposed Merger. The opinion does not constitute a recommendation to the Board of Directors or to any other persons in respect of the Merger, including as to how any holder of common stock should vote or act in respect of the Merger. Evercore’s opinion does not address the relative

merits of the Merger as compared to other business or financial strategies that might be available to Arena, nor does it address the underlying business decision of Arena to engage in the Merger.

In connection with rendering its opinion Evercore, among other things:

For purposes of its analysis and opinion, Evercore assumed and relied upon the accuracy and completeness of the financial and other information publicly available, and all of the information supplied or otherwise made available to, discussed with, or reviewed by Evercore, without any independent verification of such information (and has not assumed responsibility or liability for any independent verification of such information), and further relied upon the assurances of the management of Arena that they are not aware of any facts or circumstances that would make such information inaccurate or misleading. With respect to the Projections, Evercore assumed with Arena’s consent that they have been reasonably prepared on bases reflecting the best currently available estimates and good faith judgments of management of Arena as to the future financial performance of Arena and the other matters covered thereby. Evercore expressed no view as to the Projections or the assumptions on which they are based.

For purposes of its analysis and opinion, Evercore assumed, in all respects material to its analysis, that the representations and warranties of each party contained in the Merger Agreement are true and correct, that each party will perform all of the covenants and agreements required to be performed by it under the Merger Agreement and that all conditions to the consummation of the Merger will be satisfied without waiver or modification thereof. Evercore further assumed, in all respects material to its analysis, that all governmental, regulatory or other consents, approvals or releases necessary for the consummation of the Merger will be obtained without any delay, limitation, restriction or condition that would have an adverse effect on Arena or the consummation of the Merger or reduce the contemplated benefits of the Merger to the holders of the common stock.

Evercore did not conduct a physical inspection of the properties or facilities of Arena and did not make or assume any responsibility for making any independent valuation or appraisal of the assets or liabilities (including any contingent, derivative or other off-balance sheet assets and liabilities) of Arena, nor was Evercore furnished with any such valuations or appraisals, nor did Evercore evaluate the solvency or fair value of Arena under any state or federal laws relating to bankruptcy, insolvency or similar matters. Evercore’s opinion is necessarily based upon information made available to it as of December 12, 2021 and financial, economic, market and other conditions as they existed and as could be evaluated as of that date. It is understood that subsequent developments may affect Evercore’s opinion and that Evercore does not have any obligation to update, revise or reaffirm this opinion.

Evercore was not asked to pass upon, and expressed no opinion with respect to, any matter other than the fairness to the holders of the common stock, from a financial point of view, of the Merger Consideration. Evercore did not express any view on, and its opinion does not address, the fairness of the proposed transaction to, or any consideration received in connection therewith by, the holders of any other class of securities, creditors or other constituencies of Arena, nor as to the fairness of the amount or nature of any compensation to be paid or payable to any of the officers, directors or employees of Arena, or any class of such persons, whether relative to the Merger Consideration or otherwise. Evercore was not been asked to, nor did it express any view on, and Evercore’s opinion

did not address, any other term or aspect of the Merger Agreement or the Merger, including, without limitation, the structure or form of the Merger, or any term or aspect of any other agreement or instrument contemplated by the Merger Agreement or entered into or amended in connection with the Merger Agreement. Evercore’s opinion does not address the relative merits of the Merger as compared to other business or financial strategies that might be available to Arena, nor does it address the underlying business decision of Arena to engage in the Merger. Evercore’s opinion does not constitute a recommendation to the Board of Directors or to any other persons in respect of the Merger, including as to how any holder of shares of the common stock should act or vote in respect of the Merger. Evercore did not express any opinion as to the prices at which shares of common stock will trade at any time, as to the potential effects of volatility in the credit, financial and stock markets on Arena or the Merger or as to the impact of the Merger on the solvency or viability of Arena or the ability of Arena to pay its obligations when they come due. Evercore is not legal, regulatory, accounting or tax experts and has assumed the accuracy and completeness of assessments by Arena and its advisors with respect to legal, regulatory, accounting and tax matters.

Set forth below is a summary of the material financial analyses reviewed by Evercore with the Board of Directors on December 12, 2021 in connection with rendering its opinion. The following summary, however, does not purport to be a complete description of the analyses performed by Evercore. The order of the analyses described and the results of these analyses do not represent relative importance or weight given to these analyses by Evercore. Except as otherwise noted, the following quantitative information, to the extent that it is based on market data, is based on market data that existed on or before December 10, 2021 (the last trading date prior to the rendering of Evercore’s opinion), and is not necessarily indicative of current or future market conditions.

For purposes of its analyses and reviews, Evercore considered industry performance, general business, economic, market and financial conditions, and other matters, as they existed and could be evaluated as of the date of its opinion, many of which are beyond the control of Arena. The estimates contained in Evercore’s analyses and reviews, and the ranges of valuations resulting from any particular analysis or review, are not necessarily indicative of actual values or predictive of future results or values, which may be significantly more or less favorable than those suggested by Evercore’s analyses and reviews. In addition, analyses and reviews relating to the value of companies, businesses or securities do not purport to be appraisals or to reflect the prices at which companies, businesses or securities actually may be sold. Accordingly, the estimates used in, and the results derived from, Evercore’s analyses and reviews are inherently subject to substantial uncertainty.

The following summary of Evercore’s financial analyses includes information presented in tabular format. In order to fully understand the analyses, the tables should be read together with the full text of each summary. The tables are not intended to stand alone and alone do not constitute a complete description of Evercore’s financial analyses. Considering the tables below without considering the full narrative description of Evercore’s financial analyses, including the methodologies and assumptions underlying such analyses, could create a misleading or incomplete view of such analyses.

Evercore performed a discounted cash flow analysis of Arena to calculate the estimated present value of the standalone unlevered, after-tax free cash flows, defined as net operating profit after tax, plus depreciation and amortization, plus share-based compensation, less increases in net working capital and capital expenditures, that Arena was forecasted to generate during Arena’s fiscal years 2022 through 2040 based on the Projections provided by Arena senior management. Evercore calculated terminal values for Arena by applying perpetuity growth rates of negative 60.0% to negative 80.0%, which range was selected based on Evercore’s professional judgment and experience, to a terminal year estimate of the unlevered, after-tax free cash flows that Arena was forecasted to generate based on Projections. The cash flows were then discounted to present value as of December 31, 2021 using discount rates ranging from 8.5% to 10.0%, which were based on an estimate of Arena’s weighted average cost of capital, and the mid-year cash flow discounting convention, which range was selected based on Evercore’s professional judgment and experience. In calculating Arena’s implied enterprise value, Evercore included the upfront payment made to Aristea on July 27, 2021. Based on this range of implied enterprise values, Arena’s net debt (calculated as total debt less cash and cash equivalents) as of December 10, 2021, certain minority interests, the cost of projected future capital raises, the present value of tax savings from Arena’s estimated usage of net operating losses based on the Projections and the number of fully diluted shares of common stock, in each case as provided by Arena senior management, this analysis indicated a range of implied equity values per share of common stock of $82.95 to $101.00, compared to the Merger Consideration.

Evercore reviewed, to the extent publicly available, financial information related to the following selected transactions involving publicly-traded target companies in the biopharmaceutical industry announced since 2015 (the “Selected Transactions”). The Selected Transactions reviewed by Evercore, and the month and year each was announced, are set forth in the table below. For each Selected Transaction, Evercore calculated the implied enterprise value (defined as the target company’s implied equity value based on the consideration paid in the applicable transaction plus total debt, plus preferred equity and minority interest, less cash and cash equivalents) as a multiple of each target’s T+5 revenue (meaning revenue during the fifth year after the transaction was announced, based on broker consensus estimates as of the applicable unaffected date of each respective transaction, (“T+5 Revenue”)) as of the announcement of the applicable transaction.

Based on the multiples it derived from the Selected Transactions and based on its professional judgment and experience, Evercore selected a reference range of enterprise value to T+5 Revenue Multiples of 4.0x to 7.0x and applied this range of multiples to Arena’s estimated 2026 revenue based on the Projections. Based on this range of implied enterprise values and the number of fully diluted shares of common stock, in each case as provided by Arena senior management, this analysis indicated a range of implied equity values per share of common stock of $69.75 to $109.80, compared to the Merger Consideration.

Although none of the target companies or businesses reviewed in the Selected Transactions analysis is directly comparable to Arena and none of the Selected Transactions is directly comparable to the Merger, Evercore selected these transactions because they involve companies or businesses that Evercore, in its professional judgment and experience, considered generally relevant to Arena for purposes of its financial analyses. In evaluating the Selected Transactions, Evercore made judgments and assumptions with regard to general business, economic and market conditions and other factors existing at the time of the Selected Transactions, and other matters, as well as differences in financial, business and operating characteristics and other factors relevant to the target companies or businesses in the Selected Transactions. Accordingly, an evaluation of the results of this analysis is not entirely mathematical. Rather, this analysis involves complex considerations and judgments regarding many factors that could affect the relative values of the target companies or businesses in the Selected Transactions and the multiples derived from the Selected Transactions. Mathematical analysis, such as determining the mean or median, is not in itself a meaningful method of using the data of the Selected Transactions.

Evercore also noted certain other factors, which were not considered material to its financial analyses with respect to its opinion, but were referenced for informational purposes only, including, among other things, the following:

Evercore reviewed historical trading prices of shares of common stock during the twelve (12) month period ended December 10, 2021, noting that the low and high closing prices during such period ranged from $45.50 (on August 19, 2021) to $85.00 (February 16, 2021) per share of common stock, respectively.

Evercore reviewed selected public market trading price targets for the shares of common stock prepared and published by equity research analysts that were publicly available as of December 10, 2021, the last full trading day prior to the delivery by Evercore of its opinion to the Board of Directors. These price targets reflect analysts’ estimates of the future public market trading price of the shares of common stock at the time the price target was published. As of December 10, 2021, the range of selected equity research analyst price targets per share of common stock was $71.00 to $120.00. Public market trading price targets published by equity research analysts do not necessarily reflect current market trading prices for the shares of common stock and these target prices and the analysts’ earnings estimates on which they were based are subject to risk and uncertainties, including factors affecting the financial performance of Arena and future general industry and market conditions.

Evercore reviewed and compared certain financial information of Arena to corresponding financial multiples and ratios for the following selected publicly traded companies in the biopharmaceutical industry (the “Selected Companies”):

For each of the Selected Companies, Evercore calculated enterprise value (defined as equity market capitalization plus total debt, plus preferred equity and minority interest, less cash and cash equivalents) as a multiple of estimated revenue multiples in 2024, 2025 and 2026, based on closing share prices as of December 10, 2021. Estimated financial data of the Selected Companies were based on publicly available research analysts’ estimates.

This analysis indicated the following:

Based on the multiples it derived for the Selected Companies and based on its professional judgment and experience, Evercore applied a forward multiple reference range of 2.0x – 4.0x to Arena’s estimated 2026 revenue based on the Projections. Based on this range of implied enterprise values, Arena’s estimated net debt (calculated as total debt less cash and cash equivalents) as of December 10, 2021, and the number of fully diluted shares of common stock, in each case as provided by Arena senior management, this analysis indicated a range of implied equity values per share of common stock of $42.30 to $69.75, compared to the Merger Consideration.

Although none of the Selected Companies is directly comparable to Arena, Evercore selected these companies because they are publicly traded biopharmaceutical companies that Evercore, in its professional judgment and experience, considered generally relevant to Arena for purposes of its financial analyses. In evaluating the Selected Companies, Evercore made judgments and assumptions with regard to general business, economic and market conditions affecting the Selected Companies and other matters, as well as differences in the Selected Companies’ financial, business and operating characteristics. Accordingly, an evaluation of the results of this analysis is not entirely mathematical. Rather, this analysis involves complex considerations and judgments regarding many factors

that could affect the relative values of the Selected Companies and the multiples derived from the Selected Companies. Mathematical analysis, such as determining the mean or median, is not in itself a meaningful method of using the data of the Selected Companies.

Using publicly available information, Evercore reviewed ten transactions and announced all-cash bids for control of U.S. public biopharmaceutical targets with an aggregate transaction value between $5 billion and $10 billion announced since 2015. Using publicly available information, Evercore calculated the premiums paid as the percentage by which the per share consideration paid or proposed to be paid in each such transaction exceeded (a) the closing market share prices of the target companies one day, and (b) the volume weighted average price thirty (30) and sixty (60) days, in each case prior to the announcement of each transaction.

This analysis indicated the following:

Based on the results of this analysis and its professional judgment and experience, Evercore applied a premium range of 45% to 80% to the closing price per share of common stock of $49.94 as of December 10, 2021. This analysis indicated a range of implied equity values per share of common stock of $72.40 to $89.90, compared to the Merger Consideration.

The foregoing summary of Evercore’s financial analyses does not purport to be a complete description of the analyses or data presented by Evercore to the Board of Directors. In connection with the review of the Merger by the Board of Directors, Evercore performed a variety of financial and comparative analyses for purposes of rendering its opinion. The preparation of a fairness opinion is a complex process and is not necessarily susceptible to partial analysis or summary description. Selecting portions of the analyses or of the summary described above, without considering the analyses as a whole, could create an incomplete view of the processes underlying Evercore’s opinion. In arriving at its fairness determination, Evercore considered the results of all the analyses and did not draw, in isolation, conclusions from or with regard to any one analysis or factor considered by it for purposes of its opinion. Rather, Evercore made its determination as to fairness on the basis of its professional judgment and experience after considering the results of all the analyses. In addition, Evercore may have given various analyses and factors more or less weight than other analyses and factors, and may have deemed various assumptions more or less probable than other assumptions. As a result, the ranges of valuations resulting from any particular analysis or combination of analyses described above should not be taken to be the view of Evercore with respect to the actual value of the shares of common stock. Rounding may result in total sums set forth in this section not equaling the total of the figures shown.

Evercore prepared these analyses for the purpose of providing an opinion to the Board of Directors as to the fairness, from a financial point of view, of the Merger Consideration to the holders of shares of common stock. These analyses do not purport to be appraisals or to necessarily reflect the prices at which the business or securities actually may be sold. Any estimates contained in these analyses are not necessarily indicative of actual future results, which may be significantly more or less favorable than those suggested by such estimates. Accordingly, estimates used in, and the results derived from, Evercore’s analyses are inherently subject to substantial uncertainty, and Evercore assumes no responsibility if future results are materially different from those forecasted in such estimates.

Evercore’s financial advisory services and its opinion were provided for the information and benefit of the Board of Directors (in its capacity as such) in connection with its evaluation of the proposed Merger. The issuance of Evercore’s opinion was approved by an Opinion Committee of Evercore.

Evercore did not recommend any specific amount of consideration to the Board of Directors or Arena senior management or that any specific amount of consideration constituted the only appropriate consideration in the Merger for the holders of common stock.

Pursuant to the terms of Evercore’s engagement letter with Arena, Arena has agreed to pay Evercore a fee for its services in the amount of approximately $36.6 million, of which $2 million was paid upon delivery of Evercore’s opinion, and the balance of which will be payable contingent upon the consummation of the Merger. The Company has also agreed to reimburse Evercore for its expenses and to indemnify Evercore against certain liabilities arising out of its engagement.

During the two (2) year period prior to the date of its opinion, Evercore and its affiliates have not been engaged to provide financial advisory or other services to Arena, and Evercore has not received any compensation from Arena during such period. In addition, during the two (2) year period prior to the date of its opinion, Evercore and its affiliates have not been engaged to provide financial advisory or other services to Pfizer, and Evercore has not received any compensation from Pfizer during such period. Evercore may provide financial advisory or other services to Arena and Pfizer in the future, and in connection with any such services Evercore may receive compensation.

Evercore and its affiliates engage in a wide range of activities for its and their own accounts and the accounts of customers, including corporate finance, mergers and acquisitions, equity sales, trading and research, private equity, placement agent, asset management and related activities. In connection with these businesses or otherwise, Evercore and its affiliates and/or its or their respective employees, as well as investment funds in which any of them may have a financial interest, may at any time, directly or indirectly, hold long or short positions and may trade or otherwise effect transactions for their own accounts or the accounts of customers, in debt or equity securities, senior loans and/or derivative products or other financial instruments of or relating to Arena or its affiliates, Pfizer, potential parties to a transaction and their respective affiliates or persons that are competitors, customers or suppliers of Arena.

Arena engaged Evercore to act as a financial advisor based on Evercore’s qualifications, experience and reputation. Evercore is an internationally recognized investment banking firm and regularly provides fairness opinions to its clients in connection with mergers and acquisitions, leveraged buyouts and valuations for corporate and other purposes.

The Board of Directors retained Guggenheim Securities as its financial advisor, including in connection with Arena’s possible Merger with Pfizer. Guggenheim Securities has had a long-standing investment banking relationship with Arena and has been formally engaged since November 2021 as Arena’s financial advisor. In selecting Guggenheim Securities as its financial advisor, the Board of Directors considered that, among other things, Guggenheim Securities is an internationally recognized investment banking, financial advisory and securities firm whose senior professionals have substantial experience advising companies in, among other industries, the biopharmaceutical sector. Guggenheim Securities, as part of its investment banking, financial advisory and capital markets businesses, is regularly engaged in the valuation and financial assessment of businesses and securities in connection with mergers and acquisitions, recapitalizations, spin-offs/split-offs, restructurings, securities offerings in both the private and public capital markets and valuations for corporate and other purposes.

At the December 12, 2021 meeting of the Board of Directors, Guggenheim Securities rendered an oral opinion, which was confirmed by delivery of a written opinion, to the Board of Directors to the effect that, as of December 12, 2021 and based on and subject to the matters considered, the procedures followed, the assumptions made and various limitations of and qualifications to the review undertaken, the Merger Consideration to be received by the holders of common stock in connection with the Merger was fair, from a financial point of view, to holders of common stock.

This description of Guggenheim Securities’ opinion is qualified in its entirety by the full text of the written opinion, which is attached as Annex C to this proxy statement and which you should read carefully and in its entirety. Guggenheim Securities’ written opinion sets forth the matters considered, the procedures followed, the assumptions made and various limitations of and qualifications to the review undertaken by Guggenheim Securities. Guggenheim Securities’ written opinion, which was authorized for issuance by the Fairness Opinion and Valuation Committee of Guggenheim Securities, is necessarily based on economic, business, capital markets and other conditions, and the information made available to Guggenheim Securities, as of the date of such opinion. In connection with providing its opinion, Guggenheim Securities noted that global economic conditions and the global capital markets had been

experiencing and remain subject to unusual volatility, and Guggenheim Securities expressed no view or opinion as to any potential effects of such volatility on Arena, Pfizer or the Merger. Guggenheim Securities has no responsibility for updating or revising its opinion based on facts, circumstances or events occurring after the date of the rendering of the opinion.

In reading the discussion of Guggenheim Securities’ opinion set forth below, you should be aware that such opinion (and, as applicable, any materials provided in connection therewith or the summary of Guggenheim Securities’ underlying financial analyses elsewhere in this proxy statement):

In connection with rendering its opinion, Guggenheim Securities:

With respect to the information used in arriving at its opinion, Guggenheim Securities noted that:

Guggenheim Securities also noted certain other considerations with respect to its engagement and the rendering of its opinion:

This “Summary of Financial Analyses” presents a summary of the principal financial analyses performed by Guggenheim Securities and presented to the Board of Directors in connection with Guggenheim Securities’ rendering of its opinion. Such presentation to the Board of Directors was supplemented by Guggenheim Securities’ oral discussion with the Board of Directors, the nature and substance of which may not be fully described herein.

Some of the financial analyses summarized below include summary data and information presented in tabular format. In order to understand fully such financial analyses, the summary data and tables must be read together with the full text of the summary. Considering the summary data and tables alone could create a misleading or incomplete view of Guggenheim Securities’ financial analyses.

The preparation of a fairness opinion is a complex process and involves various judgments and determinations as to the most appropriate and relevant financial analyses and the application of those methods to the particular circumstances involved. A fairness opinion therefore is not readily susceptible to partial analysis or summary description, and taking portions of the financial analyses set forth below, without considering such analyses as a whole, would in Guggenheim Securities’ view create an incomplete and misleading picture of the processes underlying the financial analyses considered in rendering Guggenheim Securities’ opinion.

In arriving at its opinion, Guggenheim Securities:

With respect to the financial analyses performed by Guggenheim Securities in connection with rendering its opinion:

Throughout this “Summary of Financial Analyses,” the following defined terms are used in connection with Guggenheim Securities’ various financial analyses:

Based on the Merger Consideration, Guggenheim Securities calculated Merger-implied premia and the implied T+5 Revenue Multiple as outlined in the table below:

Recap of Arena Change-of-Control Financial Analyses. In evaluating Arena in connection with rendering its opinion, Guggenheim Securities performed various financial analyses which are summarized in the table below and described in more detail elsewhere herein, including a financing-adjusted discounted cash flow analysis and selected precedent merger and acquisition transactions analysis. Solely for informational reference purposes, Guggenheim Securities also reviewed the 52-week trading range of common stock, premia paid in selected mergers and acquisitions transactions and Wall Street equity research analysts’ stock price targets for common stock.

Arena Discounted Cash Flow Analysis. Guggenheim Securities performed a stand-alone financing-adjusted discounted cash flow analysis of Arena based on projected, risk-adjusted, after-tax unlevered free cash flows for Arena and an estimate of its terminal/continuing value at the end of the projection period.

In performing its discounted cash flow analyses with respect to Arena:

Guggenheim Securities’ financing-adjusted discounted cash flow analyses resulted in an overall reference range of $86.00 – $107.00 per share (rounded to the nearest $1.00) for purposes of evaluating the equity value per share of the common stock on a stand-alone intrinsic-value basis.

Arena Selected Precedent Merger and Acquisition Transactions Analysis. Guggenheim Securities reviewed and analyzed certain financial metrics associated with selected precedent merger and acquisition transactions involving companies in the biopharmaceutical sector that Guggenheim Securities deemed relevant in its professional judgment for purposes of this analysis. Guggenheim Securities calculated, among other things and to the extent publicly available, certain implied change-of-control transaction multiples for the selected precedent merger and acquisition transactions (based on each company’s most recent publicly available financial filings and certain other publicly available information), which are summarized in the table below:

In performing its selected precedent merger and acquisition transactions analysis with respect to Arena, Guggenheim Securities selected a reference range of T+5 Revenue Multiples of 5.3x to 8.1x (based on the 25^th and 75^th percentile range) for purposes of evaluating the Company on a change-of-control basis.

Guggenheim Securities’ selected precedent merger and acquisition transactions analysis resulted in an overall reference range of $86.00 - $123.00 per share (rounded to the closest $1.00) for purposes of evaluating the common stock on a change of control basis.

In order to provide certain context for the financial analyses in connection with its opinion as described above, Guggenheim Securities undertook various additional financial reviews and analyses as summarized below solely for informational reference purposes. As a general matter, Guggenheim Securities did not consider such additional financial reviews and analyses to be determinative methodologies for purposes of its opinion.

Arena Stock Price Trading History. Guggenheim Securities reviewed the common stock price trading history for the 52 weeks ending December 10, 2021, the last trading day prior to the announcement of the Merger. The common stock traded in a range of $45.50 (on August 19, 2021) - $85.00 (on February 16, 2021) per share.

Arena Wall Street Equity Research Analyst Stock Price Targets. Guggenheim Securities reviewed selected Wall Street equity research analyst stock price targets for Arena as published prior to December 10, 2021. Guggenheim Securities noted that such Wall Street equity research analyst stock price targets for common stock were $71.00 – $120.00 per share.

Premia Paid in Selected Precedent Merger and Acquisition Transactions. Guggenheim Securities reviewed, based on publicly available information, the implied premia paid or proposed to be paid in connection with selected precedent merger and acquisition transactions. Guggenheim Securities noted that such precedent M&A transaction-related premia ranged from (i) 49% -67% for transactions with enterprise values between $5-$15 billion and (ii) 57% - 110% for transactions with enterprise values between $2-$20 billion (each based on the 25^th to 75^th percentile range), based on the target company’s unaffected spot closing stock price. Guggenheim Securities further noted that, in connection with the Merger, the Merger-implied premium (based on the Merger Consideration) was 100% versus Arena’s spot closing stock price of $49.94 on December 10, 2021 (the last trading day prior to the announcement of the Merger).

Except as described in the summary above, Arena did not provide specific instructions to, or place any limitations on, Guggenheim Securities with respect to the procedures to be followed or factors to be considered in performing its financial analyses or providing its opinion. The type and amount of consideration payable in the Merger were determined through negotiations between Arena and Pfizer and were approved by the Board of Directors. The decision to enter into the Merger Agreement was solely that of the Board of Directors. Guggenheim Securities’ opinion was just one of the many factors taken into consideration by the Board of Directors. Consequently, Guggenheim Securities’ financial analyses should not be viewed as determinative of the view of the Board of Directors with respect to the fairness, from a financial point of view, of the Merger Consideration to be received by the holders of common stock.

Pursuant to the terms of Guggenheim Securities’ engagement letter, Arena has agreed to pay Guggenheim Securities a cash transaction fee (based on a percentage of the aggregate value associated with the Merger) upon consummation of the Merger, which cash transaction fee currently is estimated to be $36.6 million. Arena has previously paid Guggenheim Securities a cash milestone fee of $2 million that became payable upon the rendering of Guggenheim Securities’ opinion with respect to the Merger, which will be credited against the foregoing cash transaction fee. In addition, Arena has agreed to reimburse Guggenheim Securities for certain expenses and indemnify Guggenheim Securities against certain liabilities arising out of its engagement.

In the two (2) years prior to the date of its written opinion, Guggenheim Securities has been engaged by Arena in connection with various matters unrelated to the Merger, none of which resulted in a closed transaction or receipt by Guggenheim Securities of any compensation. At the request of the Board of Directors, Guggenheim Securities provided information about its relationships with Pfizer over the last five (5) years. During the five-year period prior to the date of its written opinion, Guggenheim Securities has been engaged by Pfizer with respect to various matters unrelated to the Merger, including the following, in respect of which Guggenheim Securities received compensation:

Pfizer’s (i) carve-out of its Upjohn unit and the merger of Upjohn with Mylan N.V., (ii) divestiture of its Magnesia Bisurada subsidiary in Brazil, (iii) joint venture with GlaxoSmithKline, (iv) acquisition of Array BioPharma Inc. and (v) sale of its Hospira Infusion Systems business. Guggenheim Securities received compensation of approximately $110 million to $115 million in the aggregate from Pfizer during this five (5)-year period.

Guggenheim Securities and its affiliates and related entities engage in a wide range of financial services activities for its and their own accounts and the accounts of customers, including but not limited to: asset, investment and wealth management; insurance services; investment banking, corporate finance, mergers and acquisitions and restructuring; merchant banking; fixed income and equity sales, trading and research; and derivatives, foreign exchange and futures. In the ordinary course of these activities, Guggenheim Securities and its affiliates and related entities may (i) provide such financial services to Arena, Pfizer, other participants in the Merger and their respective affiliates, for which services Guggenheim Securities and its affiliates and related entities may have received, and may in the future receive, compensation and (ii) directly and indirectly hold long and short positions, trade and otherwise conduct such activities in or with respect to loans, debt and equity securities and derivative products of or relating to Arena, Pfizer, other participants in the Merger and their respective affiliates. Furthermore, Guggenheim Securities and its affiliates and related entities and its or their respective directors, officers, employees, consultants and agents may have investments in Arena, Pfizer, other participants in the Merger and their respective affiliates.

Consistent with applicable legal and regulatory guidelines, Guggenheim Securities has adopted certain policies and procedures to establish and maintain the independence of its research departments and personnel. As a result, Guggenheim Securities’ research analysts may hold views, make statements or investment recommendations and publish research reports with respect to Arena, Pfizer, other participants in the Merger and their respective affiliates and the Merger that differ from the views of Guggenheim Securities’ investment banking personnel.

When considering the recommendation of the Board of Directors that you vote to approve the proposal to adopt the Merger Agreement, you should be aware that our directors and executive officers may have interests in the Merger that are different from, or in addition to, the interests of stockholders generally, as more fully described below. The Board of Directors was aware of and considered these interests, among other matters, to the extent that they existed at the time, in reaching the determination that the terms and conditions of the Merger and the Merger Agreement were advisable, fair to and in the best interests of Arena and its stockholders, in reaching its decision to approve and adopt the Merger Agreement and in making their recommendation that the stockholders vote in favor of the adoption of the Merger Agreement. For more information, please see the section of this proxy statement captioned “— Interests of Arena’s Directors and Executive Officers in the Merger.”

As of the date of this proxy statement, none of our executive officers has entered into any agreement with Pfizer or any of its affiliates regarding employment with, or the right to purchase or participate in the equity of, the Surviving Corporation or one or more of its affiliates. Prior to and following the Closing, however, certain of our executive officers may have discussions, and following the Closing, may enter into agreements with, Pfizer or Merger Sub, their subsidiaries or their respective affiliates regarding employment with, or the right to purchase or participate in the equity of, the Surviving Corporation or one or more of its affiliates.

Under the Merger Agreement, any rights to indemnification or exculpation now existing in favor of the directors or officers of Arena and its subsidiaries (the “Indemnified Parties” and, each, an “Indemnified Party”) as provided in their respective organizational documents or indemnification agreements, in effect as of the date of the Merger Agreement, with respect to matters occurring at or prior to the Effective Time, will (i) survive the Merger, (ii) continue in full force and effect for a period of six (6) years after the Effective Time, and (iii) not be amended, repealed or otherwise modified in any manner that would materially and adversely affect the rights thereunder of individuals who at any time on or prior to the Effective Time were directors or officers of Arena and its subsidiaries with respect to actions or omissions occurring at or prior to the Effective Time, unless such modification is required by law. If any claim is asserted or made either prior to the Effective Time or within such six (6) year period, all rights to indemnification with respect to any such claim or claims will continue until disposition of all such claims.

Additionally, for a period of six (6) years from the Effective Time, all rights to indemnification, advancement of expenses and exculpation from liabilities for acts or omissions occurring at or prior to the Effective Time (whether asserted

or claimed prior to, at or after the Effective Time) now existing in favor of the current or former directors or officers of Arena or any of its subsidiaries and any indemnification or other similar agreements of Arena, in each case as in effect on the date of the Merger Agreement, shall continue in full force and effect in accordance with their terms.

Without limiting the foregoing, from the Effective Time until the sixth anniversary of the Effective Time, Pfizer and the Surviving Corporation (the “Indemnifying Parties) will, to the fullest extent permitted under applicable law, indemnify and hold harmless each Indemnified Party in his or her capacity as an officer or director against all losses, claims, damages, liabilities, fees, expenses, judgments or fines incurred by such Indemnified Party in connection with any legal proceeding based on or arising out of the fact that such Indemnified Party is or was a director or officer of Arena and its subsidiaries at or prior to the Effective Time and pertaining to any and all matters pending, existing or occurring at or prior to the Effective Time, whether asserted or claimed prior to, at or after the Effective Time, including any such matter arising under any claim with respect to the transactions contemplated hereby. In addition, from the Effective Time until the sixth anniversary of the Effective Time, the Indemnifying Parties will, to the fullest extent permitted under applicable law, advance reasonable and documented out-of-pocket costs and expenses (including reasonable and documented attorneys’ fees) incurred by the Indemnified Parties in connection with eligible matters within fifteen (15) days after receipt by the Surviving Corporation of a written request for such advance, subject to the execution by such Indemnified Parties of appropriate undertakings in favor of the Indemnifying Parties to repay such advanced costs and expenses if it is ultimately determined in a final and non-appealable judgment of a court of competent jurisdiction that such Indemnified Party is not entitled to be indemnified under the Merger Agreement.

Arena may (i) maintain, at no expense to the beneficiaries, in effect for six (6) years from the Effective Time, the current policies of the directors’ and officers’ liability insurance maintained by Arena (the “Current D&O Insurance”) with respect to matters existing or occurring at or prior to the Effective Time, so long as the annual premium therefor would not be in excess of three hundred percent (300%) of the last annual premium paid prior to the Effective Time (such three hundred percent (300%), the “Maximum Premium”), or (ii) on terms with respect to coverage, deductibles and amounts no less favorable than the existing policy, purchase (through a nationally recognized insurance broker) a six (6) year “tail policy” for the existing policy effective as of the Effective Time, for a premium not in excess of the Maximum Premium, with respect to the Current D&O Insurance and maintain such endorsement in full force and effect for its full term. However, if Arena’s or the Surviving Corporation’s existing insurance expires, is terminated or cancelled during such six (6) year period or exceeds the Maximum Premium, the Surviving Corporation will obtain as much directors’ and officers’ liability insurance as can be obtained for the remainder of such period for an annualized premium not in excess of the Maximum Premium.

For more information, please see the section of this proxy statement captioned “Proposal 1: Adoption of the Merger Agreement—Employee Benefits.”

As of December 16, 2021, there were 61,424,497 shares of common stock outstanding, 8,056,793 shares of common stock subject to outstanding Arena Options, 719,241 shares of common stock subject to outstanding Arena RSUs and 183,696 shares of common stock subject to outstanding Arena PRSUs (assuming that the performance-based vesting conditions associated with such Arena PRSUs are achieved at target). The Arena RSUs and Arena Options held by Arena’s non-employee directors and the Arena Options, Arena RSUs and Arena PRSUs held by Arena’s executive officers immediately before the Effective Time will be treated as described below.

The Merger Agreement provides that, at the Effective Time, subject to all required withholding taxes, each:

For more information, please see the section of this proxy statement captioned “Proposal 1: Adoption of the Merger Agreement—Merger Consideration—Treatment of Arena Options, Arena RSUs, and Arena PRSUs.”

The Merger Agreement generally provides that after December 12, 2021, no new offering periods will begin under the Arena ESPP, no Arena employee may become a new participant in the Arena ESPP and no Arena ESPP participant may increase the percentage amount of his or her payroll deduction election. Each purchase right issued pursuant to the Arena ESPP must be fully exercised not later than the earlier of the last day of the current purchase period or five (5) business days prior to the Effective Time, and immediately following such purchase and contingent on Closing, the Arena ESPP will terminate. Two (2) of our executive officers currently participate in the Arena ESPP and have accumulated payroll deductions under the Arena ESPP for the purchase period that commenced on November 22, 2021. For more information, please see the section of this proxy statement captioned “Proposal 1: Adoption of the Merger Agreement—Merger Consideration—Treatment of Purchase Rights under the Employee Stock Purchase Plan.”

In connection with approving the Merger Agreement, Arena amended its Amended and Restated Severance Benefit Plan (the “Severance Plan”) as of December 12, 2021, that was previously most recently amended and restated effective June 11, 2021. Each of Arena’s current executive officers participates in the Severance Plan and is party to an eligibility notice thereunder.

Under the Severance Plan and the applicable eligibility notice, in the event that a participant’s employment is terminated by Arena without “cause” or by the participant for “good reason” during the period commencing upon a Change in Control (as defined in the Severance Plan and which includes the Merger) and ending twenty-four (24) months following such Change in Control (excluding as a result of his or her death or “disability”), and subject to the participant signing and not revoking a release of claims, the participant will receive (i) a lump sum payment

equal to the sum of the monthly base salary and monthly target bonus, as then in effect (ignoring any reduction that forms the basis for “good reason,” if applicable), multiplied by eighteen (18) months (for Senior Vice Presidents), 24 months (for Executive Vice Presidents, which includes all of Arena’s executive officers) or thirty (30) months (in the case of Mr. Munshi) (each such monthly period following termination of employment an “Applicable Severance Period”); (ii) direct payment of COBRA continuation premiums for the participant and his or her eligible dependents, or, in the discretion of Arena, cash payments in lieu thereof until the earlier of (a) the expiration of the Applicable Severance Period and (b) the expiration of the participant’s eligibility for continuation coverage under COBRA; (iii) 100% acceleration of then unvested equity awards, provided that in the case of any such equity awards that vest based on the achievement of performance criteria, such equity award will vest and be paid at the greater of target performance in such award or actual performance of Arena; and (iv) extension of the post termination exercise period with respect to any vested options until the later of (a) twenty-four (24) months following termination of employment (or in the case of Mr. Munshi, thirty (30) months) and (b) the original post-termination exercise period.

For the purposes of the Severance Plan, “cause” generally means an involuntary termination of a participant’s employment on or after the occurrence of a change in control upon the occurrence of one or more of the following events if such event results in a demonstrably and material harmful impact on Arena’s business or reputation as reasonably determined by the Board of Directors and such termination is effectuated within thirty (30) days of the Board of Directors becoming aware of such events: (1) the participant’s willful and continued failure to substantially perform his or her duties with Arena after a written demand for substantial performance is delivered to the participant by the Board of Directors, (2) the participant’s conviction of, or plea of guilty or nolo contendere to, a felony or any crime involving fraud, dishonesty or moral turpitude; (3) the participant’s willfully engaging in gross misconduct that is a violation of a written Arena policy; or (4) the participant’s unauthorized use or disclosure of confidential information or trade secrets of Arena or breach of any Employee Proprietary Information and Inventions Agreement (or similar intellectual property agreement).

For the purposes of the Severance Plan, “good reason” generally means the participant’s resignation within ninety (90) days following the expiration of any cure period (discussed below) following the occurrence of one or more of the following during the period commencing upon a change in control and ending twenty-four (24) months following such change in control: (i) a material reduction of the participant’s annual base salary; (ii) any material reduction in the participant’s annual target bonus level or bonus opportunities; (iii) the participant’s authority, duties or responsibilities are materially diminished such that they are no longer commensurate with his or her level of experience, training and education; (iv) any significant reduction, in the aggregate, in the employee benefit programs made available to the participant other than a reduction in such employee benefit programs affecting all employees of Arena substantially equally; (v) the relocation without the participant’s prior written approval to a location that would increase the participant’s one-way commute by more than thirty-five (35) miles in the participant’s one-way commuting distance from his or her principal residence to the principal office or business location in which the participant is required to perform services; or (vi) the failure of Arena to obtain a satisfactory agreement from any successor to assume and agree to perform under the terms of the Severance Plan. A participant (1) will not resign for “good reason” without first providing Arena with written notice of the acts or omissions constituting the grounds for “good reason” within thirty (30) days of the initial existence of the grounds for “good reason” and a reasonable cure period of thirty (30) days following the date Arena receives such notice during which such condition must not have been cured; and (2) must terminate employment within ninety (90) days following the initial existence of the event giving rise to good reason.

The aggregate amount of severance that would be paid to our other currently employed executive officer (Doug Manion, M.D., FRCP (C)), in connection with a qualifying termination under the Severance Plan and second amended and restated severance benefit plan eligibility notices is $1,569,753 and an estimated Section 4999 excise tax gross-up payment of $2,405,102. Kevin R. Lind, Steven W. Spector and Preston Klassen separated employment prior to the execution of the Merger Agreement and are not eligible to receive severance under the Severance Plan as a result of a qualifying termination in connection with the Merger.

We entered into a second amended and restated severance benefit plan eligibility notice (the “Eligibility Notices”) with each of our current executive officers, effective as of December 12, 2021. The Eligibility Notices provide for the reimbursement by Arena for excise taxes under Section 4999 of the Internal Revenue Code, to the extent applicable, so that on a net after-tax basis the executive officer would be in the same position as if no such excise tax had applied to the executive officer.

As described in the section of this proxy statement captioned “Treatment of Arena Options, Arena RSUs and Arena PRSUs,” our Compensation Committee has approved our annual 2022 equity grant in the form of 2022 Arena RSUs to be granted to each of our current executive officers on January 3, 2022. Such Arena RSUs will be substituted automatically with Adjusted RSUs the same terms and conditions (including vesting conditions) at the Effective Time. Each such Adjusted RSU will vest in full upon a upon a “Qualifying Termination”, which includes a termination without “Cause” (as defined in the applicable award agreement) and a voluntary termination in connection with a “Relocation Requirement” (generally related to certain forced relocations by Arena following notice and an opportunity to cure) at any time on or after the Closing Date or for “Good Reason'' within twenty-four (24) months of Closing under the terms of the Severance Plan, as described further in the section of this proxy statement captioned “—Payments Upon Termination at or Following Change in Control.''

In accordance with Item 402(t) of Regulation S-K, the table below sets forth the compensation that is based on or otherwise relates to the Merger that will or may become payable to Arena’s named executive officers in connection with the Merger. For more information, please see the section of this proxy statement captioned “—Payments Upon Termination at or Following Change in Control” for further information regarding certain elements of this compensation.

The table below assumes that:

The amounts shown in the table below do not include the value of payments or benefits that would have been earned, or any amounts associated with equity awards that would vest pursuant to their terms, on or prior to the Closing, or the value of payments or benefits that are not based on or otherwise related to the Merger.

In addition to the assumptions described in the preceding paragraph, the amounts set forth in the table below are based on certain other assumptions that are described in the footnotes accompanying the table below. The assumptions based upon which we have estimated the amounts in the table below may or may not actually occur. Accordingly, the ultimate amounts to be received by a named executive officer in connection with the Merger may differ from the amounts set forth below. For purposes of the footnotes to the table below, “single trigger” refers to benefits that arise solely as a result of

the Closing, and “double trigger” refers to benefits that require two (2) conditions, which are the Closing and a qualifying termination. For more information, see the section of this proxy statement captioned “The Merger —Interests of Arena’s Directors and Executive Officers” below for a quantification of the amounts that the named executive officers will receive in respect of vested equity awards at the Effective Time.

As discussed above at “Treatment of Arena Options, Arena RSUs and Arena PRSUs”, at the Effective Time, each Arena Option, Arena RSU (other than the 2022 Arena RSUs) and Arena PRSU will be cancelled and automatically converted into the right to receive an amount in cash equal to the product of (i) the aggregate number of shares subject to such award, multiplied by (ii) the Merger Consideration (or, for each Arena Option, the excess, if any, of the Merger Consideration over such Arena Option’s per share exercise price or, for each Arena PRSU, the

Merger Consideration with all the performance-based vesting conditions associated with the Arena PRSU being deemed achieved at the greater of actual completed performance at the Effective Time or at target), subject to any required withholding of taxes.

Effective as of the Effective Time, each 2022 Arena RSU will be substituted automatically with an Adjusted RSU equal to the product of (i) the total number of shares subject to the 2022 Arena RSU immediately prior to the Effective Time multiplied by (ii) the Arena RSU Exchange Ratio, with any fractional shares rounded to the nearest whole share. Each Adjusted RSU will otherwise be subject to the same terms and conditions applicable to such 2022 Arena RSU immediately prior to the Effective Time (including vesting terms, and subject to accelerated vesting in connection with certain qualifying terminations of employment following the Effective Time, as described above).

Each of our executive officers is eligible to receive the applicable vesting acceleration benefits with respect to his or her equity awards described above under the heading “Payments Upon Termination at or Following Change in Control”.

The following table sets forth the number of shares of common stock and the number of shares of common stock underlying equity awards held by each of Arena’s executive officers and non-employee directors that are outstanding as of December 16, 2021, and includes the quantity of 2022 Arena RSUs to be granted to each current executive officer on January 3, 2022 (which was determined by dividing the approved grant date value for each 2022 Arena RSU by $90.00, the estimated closing price of Arena common stock on January 3, 2022). The table also sets forth the values of these shares and equity awards, determined as the number of shares multiplied by the Merger Consideration (minus the applicable per share exercise price for any Arena Options and assuming that the performance-based vesting conditions associated with such Arena PRSUs are achieved at target). Except for the awards described herein, no additional shares of common stock or equity awards were granted to any executive officer or non-employee director in contemplation of the Merger.