FLX Bio Announces Clinical Trial Collaboration Agreement With Merck for Ongoing Phase 1/2 Study of FLX475

November 05, 2018

Trial will evaluate FLX Bio’s CCR4 inhibitor, FLX475, in combination with Merck’s KEYTRUDA® (pembrolizumab), an anti-PD-1 therapy, in multiple types of cancer

SOUTH SAN FRANCISCO, Calif.--(BUSINESS WIRE)--FLX Bio, Inc., a clinical-stage, biopharmaceutical company focused on the development of oral small-molecule drugs that target drivers of cancer and other immune-related disorders, today announced that it has established a clinical trial collaboration agreement with Merck (known as MSD outside the U.S. and Canada) to conduct a Phase 1/2 study evaluating the safety and efficacy of the combination of KEYTRUDA® (pembrolizumab), Merck’s anti-PD-1 therapy , and FLX Bio’s investigational oral small molecule CCR4 inhibitor, FLX475, in patients with multiple types of cancer.

The open-label, dose-escalation and cohort expansion Phase 1/2 study is enrolling patients with multiple types of cancer at leading cancer centers across the United States, Australia and Asia. In addition to evaluating the safety and tolerability of FLX475 as a monotherapy and in combination with pembrolizumab, the study will evaluate changes in the tumor microenvironment and the antitumor activity of both monotherapy and combination therapy. For more information please visit identifier NCT03674567.

“We are extremely pleased to collaborate with Merck, an established leader in the field of cancer immunotherapy,” said Brian Wong, M.D., Ph.D., CEO of FLX Bio. “KEYTRUDA is an anti-PD1 immunotherapy that has demonstrated efficacy in a range of cancers. FLX475 targets a novel mechanism to selectively inhibit the recruitment of regulatory T cells (Treg) into the tumor, where Treg potentially suppress the anti-tumor immune response; thus FLX475 has the potential to deepen and broaden the efficacy of KEYTRUDA when combined. We are excited to collaborate with the Merck team to evaluate the efficacy of a combination of FLX475 and KEYTRUDA which we believe could substantially improve patient outcomes.”

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

About FLX475

FLX475 is a best-in-class oral, small molecule antagonist of CCR4 which selectively blocks suppressive regulatory T cells in tumor tissue and promotes a durable anti-tumor immune response. FLX Bio has completed a study of FLX475 in healthy volunteers, demonstrating that the compound is safe with excellent pharmacokinetic and pharmacodynamic properties. In preclinical studies, FLX475 inhibited tumor growth and increased tumor regression as a single agent. In addition, FLX475 enhanced the anti-tumor effects of various checkpoint inhibitors as well as immune agonist antibodies. FLX475 also has the potential to enhance cell-based immunotherapies such as CAR-T and cancer vaccines. In contrast to depleting antibody approaches, FLX475 selectively blocks the recruitment of regulatory T cells to the tumor site and does not deplete cells beneficial to an anti-tumor response or regulatory T cells in healthy tissue.

About FLX Bio

FLX Bio, Inc. is a privately-held biopharmaceutical company focused on the discovery, development and commercialization of best-in-class, oral small molecule therapeutics for the treatment of cancers and other immune disorders. Our lead compounds inhibit the CCR4 pathway which plays a key role in both suppressing the immune response to cancer and in the initiation, progression and persistence of allergic inflammation. We leverage big data and proprietary informatics together with our advanced drug discovery capabilities and deep biology expertise, to develop therapeutics that address key pressure points in pathways that propagate an abnormal immune response.

Located in South San Francisco, Calif., and funded by leading investors, including The Column Group (TCG), Kleiner Perkins (KP), Topspin Partners, GV (formerly Google Ventures) and Celgene Corporation, FLX Bio has assembled a leadership team and advisory group with a proven track record of success and team of scientists with substantial knowledge and expertise in drug discovery and translational areas essential to execute on this approach. For more information, please visit



For FLX Bio, Inc.
Angela Bitting, 925-202-6211

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