Two partial responses observed in heavily pre-treated ER+ breast cancer patients

One ongoing cohort in ER+ breast cancer has been expanded and new expansion cohort planned in ER+ breast cancer patients with Cyclin D amplification

Management and key opinion leaders to present results and provide update on expanded development of zotatifin in investor call on June 5th at 7 p.m. ET / 6 p.m. CT

SAN DIEGO and REDWOOD CITY, Calif., June 05, 2022 (GLOBE NEWSWIRE) — eFFECTOR Therapeutics, Inc. (NASDAQ:EFTR), a leader in the development of selective translation regulator inhibitors (“STRIs”) for the treatment of cancer, today reported positive interim results of the company’s ongoing Phase 1/2 clinical trial of eIF4A inhibitor zotatifin in patients with solid tumors that showed treatment was generally well tolerated, resulted in suppression of multiple oncogenic drivers and demonstrated initial signals of clinical activity.

The interim data was presented today at the 2022 ASCO Annual Meeting in a poster, entitled “First-in-human phase 1/2 dose escalation and expansion study evaluating first-in-class eIF4A inhibitor zotatifin in patients with solid tumors,” by Funda Meric-Bernstam, M.D., chair of Investigational Cancer Therapeutics, and The Nellie B. Connally Chair in Breast Cancer at The University of Texas MD Anderson Cancer Center.

As of the cutoff date of March 4, 2022, interim results showed that zotatifin was generally well tolerated. Treatment emergent adverse events (TEAEs) related to zotatifin were mostly mild, readily managed and reversible, and included fatigue, anemia, diarrhea, vomiting and nausea. In the 25 patients who received the recommended Phase 2 dose, none exhibited zotatifin-related Grade 3, 4 or 5 TEAEs.

In Part 2 of the trial, early signals of clinical activity were observed in two patients with breast cancer. One patient with amplified Cyclin D1 and an ESR1 mutation, who had progressed on prior treatment with fulvestrant, experienced a confirmed partial response when zotatifin was combined with fulvestrant. A second partial response, which was awaiting confirmatory scan at the time of data analysis, was observed with the combination of zotatifin, fulvestrant and abemaciclib in a patient with PIK3CA mutations. Both patients were heavily pretreated for metastatic disease, having failed multiple lines of therapy prior to trial enrollment.

“The low emergence of adverse events with this entirely new class of medicines is a very important point to highlight,” said Dr. Meric-Bernstam. “Coupled with the initial signals of activity, these early results are encouraging for further development of zotatifin, especially in ER+ breast cancer.”

In a pharmacodynamic analysis measuring protein expression, modulation of protein translation by zotatifin was highly selective, with less than 1% of protein expression altered. Patients treated with zotatifin demonstrated reductions in the expression of key oncogenic drivers, including Cyclin E1 and Bcl-2. The most dramatic reductions in expression of these two proteins were seen in patients who showed the highest levels of expression prior to treatment with zotatifin.

“We are very encouraged by these interim data analyses as they provide evidence that zotatifin has the potential to suppress a network of cancer driving proteins and still remain generally well tolerated. Most cancers require suppression at multiple points in a complex network of …

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