Combination of masofaniten plus enzalutamide
continues to be well tolerated with deep and durable reductions in
PSA in patients with mCRPC
Phase 2 dose expansion currently underway at
the RP2CDs of masofaniten 600 mg BID in combination with
enzalutamide 160 mg QD
Across all dosing cohorts, 81% of patients
achieved PSA90, 69% of patients achieved PSA90 in less than 90
days, and 63% of patients achieved PSA <0.2ng/mL. While the
data are still maturing, median time to PSA progression is
currently at 16.6 months.
SOUTH
SAN FRANCISCO, California and VANCOUVER, Canada, Jan. 25,
2024 /PRNewswire/ - ESSA Pharma Inc. ("ESSA", or the
"Company") (NASDAQ: EPIX), a clinical-stage pharmaceutical company
focused on developing novel therapies for the treatment of prostate
cancer, today announced the presentation of updated dose escalation
data from its Phase 1/2 study evaluating masofaniten (formerly
EPI-7386) in combination with enzalutamide at the 2024 ASCO
Genitourinary Cancers Symposium, taking place January 25 - 27, 2024, in San Francisco, CA. Masofaniten is a
first-in-class N-terminal domain androgen receptor ("AR") inhibitor
that suppresses androgen activity through a novel mechanism of
action and is being developed for the treatment of prostate cancer.
The poster presentation is available on the "Publications" section
of the Company's website at www.essapharma.com.
"The maturing data from the Phase 1 dose escalation study
evaluating masofaniten in combination with enzalutamide continue to
demonstrate that the combination is well tolerated, accompanied by
deep and durable reductions in circulating prostate-specific
antigen ("PSA") levels. While the data are still immature, the
durability of the PSA responses is encouraging with a median time
to PSA progression currently at 16.6 months. The Phase 2 dose
expansion head-to-head portion of the study is underway and is
designed to evaluate the proportion of patients with a PSA decline
on combination therapy compared to single agent enzalutamide," said
David Parkinson, MD, President and
CEO of ESSA. "We look forward to evaluating the potential long-term
benefits of masofaniten in patients with metastatic
castration-resistant prostate cancer ("mCRPC") and to providing
future updates."
Poster presentation details:
Title: Phase 1/2 trial of oral EPI-7386
(masofaniten) in combination with enzalutamide (Enz) compared to
Enz alone in patients with metastatic castration-resistant prostate
cancer (mCRPC): Phase 1 (P1) results and phase 2 (P2) design.
Presenting Author: Christos Kyriakopoulos, MD,
University of Wisconsin-Madison Carbone
Cancer Center
Abstract #: 141
Date and time: Thursday, January 25,
2024; 11:30-1:00 p.m. PT
Data summary: This Phase 1/2 multicenter, open-label
clinical trial enrolled patients with mCRPC who have received
androgen deprivation therapy and who are naïve to second-generation
antiandrogens but may have been treated previously with one line of
prior chemotherapy in the metastatic hormone-sensitive prostate
cancer setting. The data presented today include 18 patients across
four cohorts in the Phase 1 dose escalation portion of the study.
Masofaniten has no effect on enzalutamide exposure, thus allowing
the use of full dose per label (160mg) of enzalutamide in
combination. Enzalutamide reduces masofaniten exposure but twice
daily dosing of masofaniten appears to mitigate the reduction and
maintains clinically relevant drug exposures.
In patients evaluable for safety (n=18), masofaniten combined
with enzalutamide, continues to be well-tolerated at the dose
levels tested through 25 cycles of dosing in some patients. Most
frequent adverse events were Grades 1 and 2, related to either AR
inhibition or gastrointestinal tract irritation. In Cohort 4, one
patient experienced a Grade 3 rash, which was observed immediately
following administration of masofaniten combined with enzalutamide
and deemed probably related, resulting in the expansion of the
cohort from four to seven patients. No additional dose-limiting
toxicities (DLTs) were observed, therefore the maximum tolerated
dose (MTD) was not reached. The recommended Phase 2 combination
doses (RP2CDs) were identified as masofaniten 600 mg twice daily
(BID) in combination with enzalutamide 160 mg once daily (QD).
In the patients evaluable for efficacy (n=16), rapid, deep and
durable reductions in PSA were observed, regardless of previous
chemotherapy status, including in patients who received lower than
the full dose of enzalutamide (120 mg). Across all dose cohorts,
88% of patients (14 of 16) achieved PSA50, 81% of patients (13 of
16) achieved PSA90, 69% of patients (11 of 16) achieved PSA90 in
less than 90 days, and 63% of patients (10 of 16) achieved PSA
<0.2ng/mL. While the data for disease PSA progression are still
maturing with a current median follow up of 11.1 months, the median
time to PSA progression is at 16.6 months.
The randomized, open-label, two arm, Phase 2 dose expansion
portion of the study is underway and is designed to evaluate the
combination of masofaniten and enzalutamide versus single agent
enzalutamide in patients with mCRPC naïve to second generation
anti-androgens. The study is currently enrolling at approximately
25 sites in the USA, Canada and Australia. Expansion to European sites is in
progress.
About Masofaniten
Masofaniten (formerly known as EPI-7386) is a first-in-class
investigational, highly selective, oral, small molecule inhibitor
of the N-terminal domain ("NTD") of the androgen receptor ("AR").
Masofaniten's unique mechanism of action disrupts the AR signaling
pathway, the primary pathway that drives prostate cancer growth, by
selectively binding to the NTD, a region of the AR that is not
currently targeted by other therapies. Masofaniten is currently
being studied in an open-label, randomized Phase 2 clinical
trial (NCT05075577) in combination with enzalutamide in
patients with metastatic castration-resistant prostate cancer
(mCRPC) naïve to second-generation antiandrogens. ESSA is also
conducting a Phase 1 monotherapy study (NCT04421222) in patients
with mCRPC whose tumors have progressed on standard-of-care
therapies. The U.S. Food and Drug Administration has granted Fast
Track designation to masofaniten for the treatment of adult male
patients with mCRPC resistant to standard-of-care treatment. ESSA
retains all rights to masofaniten worldwide.
About ESSA Pharma Inc.
ESSA is a clinical-stage pharmaceutical company focused on
developing novel and proprietary therapies for the treatment of
patients with prostate cancer. For more information, please
visit www.essapharma.com, and follow us on Twitter and
LinkedIn.
Forward-Looking Statement
Disclaimer
This release contains certain information which, as presented,
constitutes "forward-looking information" within the meaning of the
Private Securities Litigation Reform Act of 1995 and/or applicable
Canadian securities laws. Forward-looking information involves
statements that relate to future events and often addresses
expected future business and financial performance, containing
words such as "anticipate", "believe", "plan", "estimate",
"expect", and "intend", statements that an action or event "may",
"might", "could", "should", or "will" be taken or occur, or other
similar expressions and includes, but is not limited to, statements
regarding presentations with respect to the Phase 1/2 study, the
tolerability of masofaniten in combination with enzalutamide, PSA
reductions resulting from masofaniten in combination with
enzalutamide, the potential long-term benefits of masofaniten,
providing future updates on the Phase 1/2 and Phase 2 studies, the
timing of and enrollment in the Company's studies and other
statements surrounding the Company's evaluation of masofaniten.
Forward-looking statements and information are subject to
various known and unknown risks and uncertainties, many of which
are beyond the ability of ESSA to control or predict, and which may
cause ESSA's actual results, performance or achievements to be
materially different from those expressed or implied thereby. Such
statements reflect ESSA's current views with respect to future
events, are subject to risks and uncertainties and are necessarily
based upon a number of estimates and assumptions that, while
considered reasonable by ESSA as of the date of such statements,
are inherently subject to significant medical, scientific,
business, economic, competitive, political and social uncertainties
and contingencies. In making forward looking statements, ESSA may
make various material assumptions, including but not limited to (i)
the accuracy of ESSA's financial projections; (ii) obtaining
positive results of clinical trials; (iii) obtaining necessary
regulatory approvals; and (iv) general business, market and
economic conditions.
Forward-looking information is developed based on assumptions
about such risks, uncertainties and other factors set out herein
and in ESSA's Annual Report on Form 10-K dated December 12, 2023, under the heading "Risk
Factors", a copy of which is available on ESSA's profile on EDGAR
at www.sec.gov and on SEDAR+ at www.sedarplus.ca, and as otherwise
disclosed from time to time on ESSA's EDGAR and SEDAR+ profiles.
Forward-looking statements are made based on management's beliefs,
estimates and opinions on the date that statements are made and
ESSA undertakes no obligation to update forward-looking statements
if these beliefs, estimates and opinions or other circumstances
should change, except as may be required by applicable United States and Canadian securities laws.
Readers are cautioned against attributing undue certainty to
forward-looking statements.
Contacts
ESSA Pharma, Inc.
Peter Virsik, Chief Operating
Officer
778.331.0962
pvirsik@essapharma.com
Investors and Media:
Argot Partners
212.600.1902
essa@argotpartners.com
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