LWAC Locust Walk Acquisition Corporation

Filed pursuant to Rule 424(b)(3)

Registration Statement No. 333-262339

Prospectus Supplement No. 16

(To Prospectus dated March 21, 2022)

eFFECTOR Therapeutics, Inc.

This prospectus supplement updates, amends and supplements the prospectus dated March 21, 2022 (the “Prospectus”), which forms a part of our Registration Statement on Form S-1 (Registration No. 333-262339). Capitalized terms used in this prospectus supplement and not otherwise defined herein have the meanings specified in the Prospectus.

This prospectus supplement is being filed to update, amend and supplement the information included in the Prospectus with the information contained in our Current Report on Form 8-K (the “Current Report”), filed with the SEC on March 6, 2023. Accordingly, we have attached the Current Report to this prospectus supplement.

This prospectus supplement is not complete without the Prospectus. This prospectus supplement should be read in conjunction with the Prospectus, which is to be delivered with this prospectus supplement, and is qualified by reference thereto, except to the extent that the information in this prospectus supplement updates or supersedes the information contained in the Prospectus.

Our common stock and warrants are listed on the Nasdaq Capital Market under the symbols “EFTR” and “EFTRW.” On March 3, 2023, the closing price of our common stock was $0.53 and the closing price of our warrants was $0.13.

We are an “emerging growth company” under federal securities laws and are subject to reduced public company reporting requirements. Investing in our securities involves certain risks. See “Risk Factors” beginning on page 7 of the Prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if the Prospectus or this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus supplement is March 6, 2023.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): February 28, 2023

eFFECTOR Therapeutics, Inc.

(Exact name of registrant as specified in its charter)

(858) 925-8215

(Registrant’s telephone number, including area code)

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (Sec.230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (Sec.240.12b-2 of this chapter).

Emerging growth company  ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☐

Item 3.01 Notice of Delisting or Failure to Satisfy Continued Listing Rule or Standard; Transfer of Listing.

As previously reported, on August 29, 2022, eFFECTOR Therapeutics, Inc. (the “Company”) received written notice (the “Notification Letter”) from the Listings Qualifications Department of The Nasdaq Stock Market LLC (“Nasdaq”) that because the closing bid price for the Company’s common stock had fallen below $1.00 per share for 30 consecutive business days, the Company no longer complied with the minimum bid price requirement pursuant to Nasdaq Listing Rule 5550(a)(2) (the “Minimum Bid Requirement”). The Notification Letter stated that the Company had 180 days, or until February 27, 2023, to demonstrate its compliance with the Minimum Bid Requirement.

On February 28, 2023, the Company received a second letter from Nasdaq advising that the Company had been granted an additional 180 calendar days, or to August 28, 2023, to regain compliance with the Minimum Bid Requirement, in accordance with Nasdaq Listing Rule 5810(c)(3)(A).

The Company intends to continue to actively monitor the closing bid price of its common stock and will evaluate available options to regain compliance with the Minimum Bid Requirement, including potentially implementing a reverse stock split of its outstanding common stock (if approved by the Company’s stockholders) to attempt to regain compliance. If the Company does not regain compliance within the additional compliance period, Nasdaq will provide notice that the Company’s common stock will be subject to delisting. The Company would then be entitled to appeal that determination to a Nasdaq hearings panel. There can be no assurance that the Company will regain compliance with the Minimum Bid Requirement during the 180-day additional compliance period or maintain compliance with the other Nasdaq listing requirements.