eFFECTOR Receives U.S. FDA Fast Track Designation for Zotatifin in Combination with Fulvestrant and Abemaciclib for Treatment of ER+/HER2- Advanced Metastatic Breast Cancer

Designation is for 2^nd or 3^rd line treatment of patients with disease progression following treatment with endocrine therapy and a CDK 4/6 inhibitor

Data updates and further development plans to be presented at 2023 San Antonio Breast Cancer Symposium (SABCS)

SOLANA BEACH, Calif. and REDWOOD CITY, Calif., Nov. 28, 2023 (GLOBE NEWSWIRE) — eFFECTOR Therapeutics, Inc. (NASDAQ: EFTR), a leader in the development of selective translation regulator inhibitors (STRIs) for the treatment of cancer, today announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track designation for zotatifin in combination with fulvestrant and abemaciclib (ZFA triplet) as second- or third-line therapy for the treatment of adult patients with estrogen receptor-positive (ER+)/human epidermal growth factor-negative (HER2-) advanced or metastatic breast cancer with disease progression following treatment with endocrine therapy and a CDK 4/6 inhibitor. The Fast Track designation was granted following FDA review of preclinical and clinical data for zotatifin, including recent safety and efficacy data for the ZFA triplet.

“We’re grateful to receive this Fast Track designation from FDA, which is a meaningful milestone for the development of zotatifin and reflects the demonstrated potential for zotatifin in combination with fulvestrant and abemaciclib to address unmet needs in ER+/HER2- breast cancer,” said Steve Worland, Ph.D., chief executive officer of eFFECTOR. “We value the opportunities provided by Fast Track designation for frequent interactions with the FDA review team as we advance this development program for zotatifin, and look forward to providing further data updates and development plans at the 2023 San Antonio Breast Cancer Symposium.”

Fast Track designation is available to a product if it is intended, whether alone or in combination with one or more other drugs, for the treatment of a serious or life-threatening disease or condition, and it demonstrates the potential to address unmet medical needs for such a disease or condition. This designation is intended to facilitate development and expedite review of drugs to treat serious and life-threatening conditions so that an approved product may reach the market expeditiously.

Zotatifin is being investigated in a Phase 1/2 dose escalation and expansion study, with cohorts currently enrolling in ER+/HER2- breast cancer. Data presented at the 2023 meeting of the American Society of Clinical Oncology (ASCO) showed that, in heavily pretreated patients (median four prior lines of therapy for metastatic disease), five out of 19 (26%) RECIST-evaluable patients achieved a partial response (PR), including four confirmed and one unconfirmed. All five patients who achieved a PR had previously progressed on prior CDK 4/6 and fulvestrant treatments, and all five had received one or more prior lines of chemotherapy in the metastatic setting. Based on safety and tolerability results to date, dose escalation was resumed in combination with fulvestrant (ZF doublet). Further updates to interim data from the ZFA triplet cohort and resumed dose escalation cohorts will be presented as a poster at SABCS on Friday, December 8, 2023.

About Zotatifin
Zotatifin is a potent and sequence-selective small molecule inhibitor of the RNA helicase eIF4A that is designed to suppress expression of a network of cancer driving proteins, including Cyclins D and E, CDKs 2, 4 and 6 and select RTKs as well as KRAS. Zotatifin is currently being evaluated in an ongoing clinical trial in patients with ER+/HER2- metastatic breast cancer.

About eFFECTOR Therapeutics
eFFECTOR is a clinical-stage biopharmaceutical company pioneering the development of a new class of oncology drugs referred to as STRIs. eFFECTOR’s STRI product candidates target the eIF4F complex and its activating kinase, mitogen-activated protein kinase interacting kinase (MNK). The eIF4F complex is a central node where two of the most frequently mutated signaling pathways in cancer, the PI3K-AKT-mTOR and RAS-MEK-ERK pathways, converge to activate the translation of select mRNA into proteins that are frequent culprits in key disease-driving processes. Each of eFFECTOR’s product candidates is designed to act on a single protein that drives the expression of a network of functionally related proteins, including oncoproteins and immunosuppressive proteins in T cells, that together control tumor growth, survival and immune evasion. eFFECTOR’s lead product candidate, tomivosertib, is a MNK inhibitor currently being evaluated in KICKSTART, a randomized, double-blind, placebo-controlled Phase 2b trial of tomivosertib in combination with pembrolizumab in patients with metastatic non-small cell lung cancer (NSCLC). Zotatifin, eFFECTOR’s inhibitor of eIF4A, is currently being evaluated in Phase 2a expansion cohorts in certain biomarker-positive solid tumors, including ER+ breast cancer and KRAS-mutant NSCLC. eFFECTOR has a global collaboration with Pfizer to develop inhibitors of a third target, eIF4E.

Forward-Looking Statements
eFFECTOR cautions you that statements contained in this press release regarding matters that are not historical facts are forward-looking statements. The forward-looking statements are based on our current beliefs and expectations and include, but are not limited to: the future clinical development of our product candidates; the potential therapeutic benefits of our product candidates; and our ability to realize the benefits from zotatifin receiving Fast Track designation from the FDA. Actual results may differ from those set forth in this press release due to the risks and uncertainties inherent in our business, including, without limitation: Fast Track designation may not result in a more expedited development or regulatory review process, and such a designation does not increase the likelihood that zotatifin will receive marketing approval in the United States; Fast Track designation does not change the standards for regulatory approval; the FDA may later decide that zotatifin no longer meets the conditions for qualification or decide that the time period for FDA review or approval will not be shortened; interim results of a clinical trial are not necessarily indicative of final results and one or more of the clinical outcomes may materially change as patient enrollment continues, following more comprehensive reviews of the data and more patient data become available; potential delays in the commencement, enrollment, data readouts and completion of clinical trials; the success of our clinical trials and preclinical studies for our product candidates is uncertain; regulatory developments in the United States and foreign countries; unexpected adverse side effects or inadequate efficacy of our product candidates that may limit their development, regulatory approval and/or commercialization, or may result in recalls or product liability claims; and other risks described in our prior filings with the Securities and Exchange Commission. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof, and we undertake no obligation to update such statements to reflect events that occur or circumstances that exist after the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement, which is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.

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