Item 8.01 Other Events.
On December 8, 2023, eFFECTOR Therapeutics, Inc. (the “Company”) announced new positive interim data from dose escalation and Phase 2 expansion
cohorts of a Phase 1/2 clinical study of zotatifin in patients with estrogen receptor positive (“ER+”) metastatic breast cancer (“mBC”). The data, reflecting a cutoff date of November 17, 2023, is being presented by Ezra
Rosen, M.D., Ph.D., Medical Oncologist and Early Drug Development Specialist, Memorial Sloan Kettering Cancer Center, at the 2023 San Antonio Breast Cancer Symposium (SABCS®), held from
December 5 – 9, 2023 in San Antonio, Texas.
In the cohort evaluating zotatifin in combination with fulvestrant and abemaciclib (“ZFA
triplet”), patients with a median of four prior lines of therapy for metastatic disease received 0.07 mg/kg zotatifin dosed on Days 1 and 8 of 21-day cycles, combined with fulvestrant and abemaciclib. In
this cohort, the mPFS was 7.4 months (95% confidence intervals 2.8 to non-estimable). As previously reported, five of 19 (26%) RECIST-evaluable patients had partial responses, including four confirmed and one
unconfirmed. The ZFA triplet was generally well tolerated, with the large majority of zotatifin-related treatment-emergent adverse events (“TEAEs”) being Grade 1 or 2. The most common zotatifin-related TEAEs were nausea, vomiting and
fatigue, all Grade 1 or 2. The most common Grade 3 or higher zotatifin-related TEAEs were anemia and blood creatinine phosphokinase increase, each in two of 20 (10%) patients. Four of 20 (20%) of patients discontinued treatment due to adverse events
of any cause.
In the new dose escalation cohorts evaluating zotatifin and fulvestrant (“ZF doublet”), three patients were enrolled at each dose
level of 0.1, 0.14 and 0.2 mg/kg zotatifin administered once every two weeks, combined with fulvestrant. The patients were heavily pretreated, with a median of four prior lines of treatment for metastatic disease. There were no dose-limiting
toxicities (“DLTs”) or serious adverse events (“SAEs”) observed in these nine patients and enrollment is ongoing now at 0.28 mg/kg zotatifin combined with fulvestrant. There was one confirmed partial response in the 0.1 mg/kg
cohort, two instances of stable disease in the 0.14 mg/kg cohort and one instance of stable disease in the 0.2 mg/kg cohort.
Based on the safety and
tolerability of the ZF doublet, dose escalation has been reopened in the ZFA triplet, with enrollment ongoing at 0.1 mg/kg zotatifin dosed once every two weeks, combined with fulvestrant and abemaciclib. The Company expects to report additional data
from dose escalation in the first half of 2024.
The Phase 1/2 trial is an open-label randomized dose-escalation and cohort-expansion study evaluating
eIF4A inhibitor, zotatifin, in patients with advanced solid tumors. The primary objectives of part one of the trial are to evaluate the safety and tolerability of zotatifin as a monotherapy in patients with defined, advanced solid tumors, determine
the recommended Phase 2 dose for zotatifin as a monotherapy and to evaluate the pharmacokinetics profile. In part two of the trial, the primary objective is to evaluate the preliminary antitumor activity of zotatifin as a monotherapy and as a
combination therapy in patients with defined, advanced solid tumors.
Forward-Looking Statements
The Company cautions you that statements contained in this report 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 potential therapeutic benefits of zotatifin; and the future clinical development and data readouts of zotatifin and the timing
thereof. Actual results may differ from those set forth in this report due to the risks and uncertainties inherent in our business, including, without limitation: 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 as more patient data becomes available, including the risk that unconfirmed responses may not
ultimately result in confirmed responses to treatment after follow-up evaluations; potential delays in the commencement, enrollment and completion of clinical trials; 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; the success of our clinical trials and preclinical
studies for our product candidates is uncertain; we may use our capital resources sooner than expected and they may be insufficient to allow clinical trial readouts; 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; our ability to obtain and maintain
intellectual property protection for our product candidates; 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.