ESSA Pharma Announces Presentations at the American Society of Clinical Oncology Genitourinary Cancers Symposium (ASCO GU)

SOUTH SAN FRANCISCO, California and VANCOUVER, Canada, Feb. 13, 2023 /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 that further analyses of initial clinical data from two Phase 1 studies of EPI-7386 in patients with metastatic castration-resistant prostate cancer ("mCRPC") will be presented at the 2023 American Society of Clinical Oncology Genitourinary Cancers Symposium ("ASCO GU"), taking place February 16-19, 2023, in San Francisco, California and online. EPI-7386 is a first-in-class N-terminal domain androgen receptor ("AR") inhibitor that suppresses androgen activity through a novel mechanism of action. The two poster presentations are available on the ASCO GU Digital Program and the "Publications" section of the Company's website at www.essapharma.com.

"We are encouraged that EPI-7386 has continued to be well-tolerated and safe as well as demonstrate initial anti-tumor activity both as a monotherapy and in combination with enzalutamide in patients with metastatic castration-resistant prostate cancer," said David Parkinson, MD, President and CEO of ESSA. "Although the clinical data is still in the early stages, with longer follow-up we observe that EPI-7386 in combination with enzalutamide continues to show deep and sustained prostate-specific antigen ("PSA") declines, which may indicate the potential for long-term treatment benefits. We look forward to further exploring the potential clinical benefit of EPI-7386 in combination with enzalutamide as we look to enroll patients in the final cohort of the dose escalation study and prepare to enroll approximately 120 patients in the randomized Phase 2 study at clinical sites across the U.S., Canada, and Australia."

Abstract #179
Title: Phase 1/2 Study of EPI-7386 in Combination with Enzalutamide (Enz) Compared with Enz Alone in Subjects with Metastatic Castration-Resistant Prostate Cancer (mCRPC)
Presenting Author: Andrew Leonard Laccetti, MD, MS, Memorial Sloan Kettering Cancer Center
Format: Poster

The Phase 1/2 multicenter, open-label clinical trial is enrolling mCRPC patients on androgen deprivation therapy 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 current presentation of data is an update on the first two cohorts of patients which was previously presented at the Prostate Cancer Foundation Scientific Retreat in October 2022. In this update, EPI-7386 in combination with enzalutamide continues to be safe and well-tolerated at the doses tested with clinically relevant drug exposures of both enzalutamide and EPI-7386 with deep and durable PSA reductions continuing through 13 cycles of dosing in some patients. Five of six evaluable patients achieved a PSA90 (≥90% decline in PSA) during the study with these PSA responses being maintained or further deepening during the course of the study. These rapid and deep PSA declines occurred both in patients who have and have not received prior chemotherapy. A further analysis shows that four of six evaluable patients' PSA levels reached <0.2 ng/mL, one of the most stringent measures of PSA decline. 

Abstract #177
Title: Oral EPI-7386 in Patients with Metastatic Castration-Resistant Prostate Cancer
Presenting Author: Russell Kent Pachynski, MD, Washington University School of Medicine
Format: Poster

The data reported are from 45 heavily pretreated mCRPC patients from both the phase 1a and 1b patient populations. Updated results of EPI-7386 as a monotherapy demonstrate that EPI-7386 continues to be safe and well-tolerated with clinically relevant drug exposures reached at all dose levels tested. Similar to what was reported previously at the Prostate Cancer Foundation Scientific Retreat in October 2022, clinically important signals of anti-tumor activity of EPI-7386 were observed in a subset of these patients (those with less than 3 lines of treatment for mCRPC, lack of visceral disease, no prior chemotherapy and lack or few non-AR mutations).

Part 1b of the study is open with enrollment focused on pre-chemotherapy, post-second-generation antiandrogen treated mCRPC patients in one cohort, and treatment-naïve non-mCRPC patients in a window of opportunity proof-of-concept second cohort. Two doses will be evaluated based on FDA Project Optimus recommendations.

EPI-7386 is an investigational, highly-selective, oral, small molecule inhibitor of the N-terminal domain of the androgen receptor. EPI-7386 is currently being studied in a Phase 1 clinical trial (NCT04421222) in men with CRPC whose tumors have progressed on standard-of-care therapies. The U.S. FDA has granted Fast Track designation to EPI-7386 for the treatment of adult male patients with mCRPC resistant to standard-of-care treatment. ESSA is also conducting a Phase 1/2 clinical trial (NCT05075577) of EPI-7386 in combination with enzalutamide in metastatic CRPC patients who have not yet been treated with second-generation antiandrogen therapies. ESSA retains all rights to EPI-7386 worldwide.

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 under @ESSAPharma.

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 the presentation of clinical data from the Phase 1 studies, the clinical benefit of EPI-7386 in combination with enzalutamide, the enrollment of patients in the Phase 2 study, the results of clinical data in the combination and monotherapy studies, and the evaluation of the dose schedules in Part 1b of the monotherapy study.

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 Quarterly Report on Form 10-Q dated February 7, 2023 under the heading "Risk Factors", a copy of which is available on ESSA's profile on EDGAR at www.sec.gov and on the SEDAR website at www.sedar.com, 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.

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