eFFECTOR Therapeutics to Present Interim Data from Ongoing Zotatifin Phase 1/2 Dose Escalation and Expansion Trial at 2022 ASCO Annual Meeting

Positive initial data demonstrated pharmacologically relevant exposures Management and key opinion leaders to present complete 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., May 26, 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 announced that it will present interim data from its ongoing Phase 1/2 dose escalation and expansion trial of zotatifin in multiple solid tumors in an oral poster presentation at the 2022 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, IL, including safety, pharmacokinetics, pharmacodynamics and responses in two expansion cohorts. Zotatifin (eFT226) is eFFECTOR’s wholly-owned potent and selective inhibitor of mRNA helicase eIF4A, designed to downregulate expression of key oncoproteins and cell cycle proteins that drive tumor growth and resistance. eFFECTOR has completed the Phase 1 portion of this trial and is currently enrolling patients in multiple Phase 2a open-label expansion cohorts in patients with solid tumors, including ER+ breast cancer and KRAS G12C non-small cell lung cancer (NSCLC). “The data to be reported at ASCO represent the first clinical profile for this novel mechanism of action to treat cancer,” said Steve Worland, Ph.D., President, and Chief Executive Officer of eFFECTOR. “The interim data from our ongoing trial demonstrated that the recommended Phase 2 dose (RP2D) of zotatifin was well-tolerated and achieved pharmacologically active exposures as shown by reductions in target proteins in on-treatment biopsies and by two responses as of the most recent data cut-off in the expansion cohorts. We look forward to sharing more in-depth data and plan to elaborate on our expanded development plans for the zotatifin program during our investor call.” 2022 ASCO Annual Meeting Abstract title: First-in-human Phase 1/2 dose escalation and expansion study evaluating first-in-class eIF4A inhibitor zotatifin in patients with solid tumorsPresenter: Funda Meric-Bernstam, M.D., The University of Texas MD Anderson Cancer CenterDate: June 5, 2022Time: 8:00 AM – 11:00 AM CTAbstract number: 3081Poster Session: Developmental Therapeutics—Molecularly Targeted Agents and Tumor BiologyPoster number: 73 Conference CalleFFECTOR management will host a conference call with commentary from key opinion leaders to provide additional details of the interim study results and discuss upcoming milestones. Call details are as follows: Date: June 5, 2022Time: 7:00 p.m. ET | 6 p.m. CT | 4:00 p.m. PTConference ID: 7267595Dial-in: Toll-Free Dial-In Number: (855) 493-1511; International Dial-In Number: (409) 497-0884 The webcast can be accessed on the “Events and Presentations” page of the “Investors” section of the Company’s website. The webcast will be archived and available for replay on the Company’s website for 30 days following the call. Please log on approximately 5 to 10 minutes prior to the scheduled start time to download and install any audio software if needed. For more information, please visit investors.effector.com. About Zotatifin (eFT226)Zotatifin is a potent and sequence-selective inhibitor of eukaryotic translation initiation factor 4A (eIF4A)-mediated translation. eIF4A is responsible for unwinding complex structures in the non-coding 5’ untranslated region of certain messenger RNA (mRNA). Zotatifin is designed to block this process, thereby inhibiting the translation of mRNAs encoding several important cell cycle proteins, oncogenes and survival factors, including Cyclin D, CDK4/6, receptor tyrosine kinases (RTKs), KRAS, and MYC. In vivo studies have shown potent tumor regression in multiple tumor models dependent on these factors, including breast cancer and NSCLC. Since zotatifin inhibits the translation of mRNA by acting in the non-coding region of mRNAs, it is not limited to specific KRAS activating mutation subtypes such as KRAS G12C or KRAS G12D. Zotatifin is currently being evaluated as an intravenous (IV) infusion in a Phase 2a clinical trial that includes patients with breast cancer and KRAS-mutant NSCLC and in a Phase 1b clinical trial in patients with mild to moderate COVID-19 infections pursuant to grant sponsorship by the Defense Advanced Research Projects Agency (DARPA). About eFFECTOR TherapeuticseFFECTOR 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. 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 StatementseFFECTOR 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 the planned update on expanded development of zotatifin and the timing thereof; and the potential therapeutic benefits of our product candidates. 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: 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 and completion of clinical trials; additional disruptions to our operations from the COVID-19 pandemic, including clinical trial and manufacturing delays; 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; any future impacts to our business resulting from the conflict between Russia and Ukraine 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. Contacts: Investors:Stephanie CarringtonWestwicke, an ICR [email protected] Media:Heidi Chokeir, Ph.D.Canale [email protected]