eFFECTOR Therapeutics to Collaborate with the Dana-Farber Cancer Institute on an Investigator-Sponsored Phase 2 Clinical Trial Evaluating Zotatifin as Combination Treatment in ER+ Endometrial Cancer and in Low Grade Serous Ovarian Cancer

SOLANA BEACH, Calif. and REDWOOD CITY, Calif., May 20, 2024 (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 a collaboration to conduct an investigator-sponsored trial (IST) evaluating zotatifin in combination with abemaciclib and letrozole in patients with estrogen receptor-positive (ER+) endometrial cancer and low grade serous ovarian cancer at the Dana-Farber Cancer Institute (DFCI) under the direction of Panagiotis Konstantinopoulos, M.D., Ph.D., Director of Translational Research and attending oncologist in the Division of Gynecologic Oncology at DFCI, and an Associate Professor of Medicine at Harvard Medical School.

“Endometrial cancer is the most prevalent cancer affecting the female reproductive organs in the United States,” said Dr. Konstantinopoulos. “While early detection offers hope for successful treatment, patients with recurrent or metastatic disease have limited treatment options. Recent studies of the abemaciclib and letrozole combo in ER+ endometrial cancer patients have shown promising activity, however, most patients either fail to respond or eventually develop resistance to CDK4/6 inhibition, a critical aspect of treatment. Similarly, low grade serous ovarian cancer has shown sensitivity to combined treatment with aromatase inhibitors and CDK4/6 inhibition, but responding patients eventually develop disease progression. By targeting eIF4A, which subsequently downregulates the key factors implicated in CDK4/6 inhibition resistance, we believe that integrating zotatifin with abemaciclib and letrozole treatment regimen represents a compelling strategy for combating recurrent endometrial cancer and low grade serous ovarian cancer.”

Doug Warner, M.D., chief medical officer of eFFECTOR Therapeutics added, “We are thrilled to embark on this investigator-sponsored Phase 2 trial in collaboration with Dr. Konstantinopoulos and his team at the DFCI. This trial represents a significant step forward in our collective efforts to address the complexities of endometrial cancer and low grade serous ovarian cancer. By exploring the potential of zotatifin as a combination treatment and its unique mechanism of action, we aim to redefine the treatment landscape and improve outcomes for these patients. With this comprehensive approach which simultaneously targets tumor cell cycle progression while reducing estrogen levels, we hope to overcome resistance mechanisms and enhance treatment efficacy which we believe could be applied in various malignancies beyond breast and endometrial cancers. In parallel, we continue to advance development of zotatifin in ER+ metastatic breast cancer and anticipate determination of the Phase 2 dose (RP2D) of zotatifin in combination with fulvestrant and abemaciclib, in the second half of 2024.”

About Zotatifin

Zotatifin is a potent and sequence-selective small molecule inhibitor of the RNA helicase eIF4A that is designed to suppress the overproduction of cell cycle proteins and oncogenes, including Cyclins D and E, CDKs 4 and 6, ERα, KRAS, HER2, and other RTKs. Zotatifin is currently being evaluated in a Phase 2a expansion cohort in combination with fulvestrant and abemaciclib in ER+ breast cancer. Efficacy data presented at 2023 ASCO and SABCS showed a 26% response rate and mPFS of 7.4 months as a triplet in heavily pretreated patients.

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 and RAS-MEK 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. Zotatifin, eFFECTOR’s inhibitor of eIF4A, is currently being evaluated in a Phase 2a expansion cohort in combination with fulvestrant and abemaciclib in ER+ breast cancer and in Phase 2 IST in combination with abemaciclib and letrozole in ER+ endometrial cancer. Tomivosertib, eFFECTOR’s MNK inhibitor, is currently being evaluated in an investigator-sponsored trial in AML. 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, including expectations on enrollment and the timing of reporting data from ongoing clinical trials; the potential therapeutic benefits of our product candidates; and the timing and potential benefits of the IST evaluating zotatifin in combination with abemaciclib and letrozole in patients with ER+ endometrial cancer and low grade serous ovarian cancer. 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: potential delays in the commencement, enrollment and completion of clinical trials, including the IST conducted by DFCI; the success of our clinical trials and preclinical studies for our product candidates is uncertain; we are dependent on DFCI to conduct the IST trial and we may not realize any benefits from the collaboration with DFCI; our dependence on third parties in connection with product manufacturing, research and preclinical and clinical testing; the results of preclinical studies and early clinical trials are not necessarily predictive of future results; 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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Christopher M. Calabrese
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kgardner@lifesciadvisors.com

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Michael Fitzhugh
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