eFFECTOR Therapeutics Announces Clinical Collaboration with Merck to Conduct a Phase 2 Combination Trial to Evaluate eFFECTOR’s Tomivosertib (eFT508) with KEYTRUDA® (pembrolizumab) for Metastatic Triple Negative Breast Cancer

SAN DIEGO, October 16, 2018 — eFFECTOR Therapeutics, Inc., a leader in the development of selective translation regulators (STRs) for the treatment of cancer, today announced it has entered into a clinical collaboration agreement with Merck (known as MSD outside the United States and Canada), through a subsidiary, to evaluate the combination of eFFECTOR’s tomivosertib (eFT508), an oral, small molecule inhibitor of MNK1/2, with Merck’s anti-PD-1 therapy, KEYTRUDA® (pembrolizumab), for the treatment of patients with metastatic triple negative breast cancer (TNBC).

“The TNBC trial will expand the current tomivosertib Phase 2 clinical trial program, allowing eFFECTOR to explore a combination with KEYTRUDA for an indication in which neither drug is yet approved,” said Steve Worland, Ph.D., president and chief executive officer of eFFECTOR. “Based on preclinical studies showing tomivosertib has substantial immunomodulatory activity and synergizes with checkpoint inhibitors, we believe targeting MNK1/2 has significant potential to enhance the clinical activity of KEYTRUDA.”

The multicenter Phase 2 clinical trial will evaluate objective response rate (ORR), duration of response (DOR), disease control rate (DCR), and time to event parameters (including PFS and OS) using RECIST v1.1 and iRECIST criteria in patients with metastatic TNBC who have failed up to two prior systemic therapies. Biomarker analysis will be performed on pretreatment tumor biopsies. Enrollment is expected to begin in early 2019.

About Triple Negative Breast Cancer 
Triple negative breast cancer (TNBC) is an often aggressive form of breast cancer that does not have specific cell receptors to the hormones estrogen or progesterone, or to human epidermal growth factor-2 (HER2) and therefore does not respond to hormonal therapies or therapies that target the HER2 receptor. Typically, TNBC is treated with a combination of therapies such as surgery, radiation and chemotherapy.

About Tomivosertib (eFT508) 
Tomivosertib (eFT508) is a selective translation regulator and is part of a new class of cancer treatments known as immunotherapies that are designed to harness the body’s own immune system in fighting cancer. Tomivosertib is a highly potent and selective, oral inhibitor of MNK1 and MNK2 (MNK1/2). MNK1/2 are terminal kinases in key oncogenic signaling pathways, including KRAS-BRAF-MEK-ERK, and are activated by the mitogen dependent protein kinases (MAPK) in multiple immune cell types. MNK1/2 integrate MAPK pathway signaling at the level of mRNA translation, resulting in decreased anti-tumor immune activity due to selective upregulation of several immune checkpoint receptors and specific immunosuppressive cytokines. Tomivosertib selectively blocks MNK1/2 driven mRNA translation, thereby promoting anti-tumor immune response. Tomivosertib is currently being evaluated as a monotherapy in a Phase 2 clinical trial in non-GCB DLBCL, study NCT02937675. Tomivosertib is also currently being evaluated in two additional Phase 2 combination trials with checkpoint inhibitors targeting PD-1 or PD-L1, including a trial (NCT03258398) in patients with relapsed or refractory microsatellite stable colorectal cancer (MSS CRC), and another trial (NCT03616834) wherein tomivosertib is being added on to patients experiencing insufficient response to approved checkpoint inhibitors in multiple important cancer indications, including non-small cell lung, urothelial, head and neck and hepatocellular cancer among others.

About eFFECTOR Therapeutics 
eFFECTOR Therapeutics is a clinical-stage biopharmaceutical company focused on pioneering the discovery and development of selective translation regulators as a new class of oncology drugs. The company’s investigational compounds are designed to restore the translational control of processes which tumors have hijacked for their benefit, while preserving normal cell function. eFFECTOR’s most advanced program focuses on the development of tomivosertib (eFT508), a MNK1/2 inhibitor in development for the treatment of patients with solid tumors and lymphoma. The company has additional selective translation regulator programs currently in discovery and development and maintains global rights to all of its development programs. For more information visit www.effector.com.

KEYTRUDA® is a registered trademark of Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA

SOURCE eFFECTOR Therapeutics, Inc.

Contacts:

Investors:
Robert H. Uhl
Westwicke Partners
858-356-5932
robert.uhl@westwicke.com

Media:
Heidi Chokeir, Ph.D.
Canale Communications
619-849-5377
heidi@canalecomm.com