First Patient Dosed in Ph III Trial of Bemarituzumab for Advanced Gastric and Gastroesophageal Junction Cancers

Five Prime Therapeutics, Inc. (Nasdaq: FPRX) and Zai Lab Limited (Nasdaq: ZLAB) announced on 10/1/18 dosing of the first patient in the Phase 3 FIGHT pivotal trial of bemarituzumab (FPA144), an isoform-selective FGF receptor 2b (FGFR2b) antibody, in combination with chemotherapy in patients with previously untreated, advanced gastric cancer (GC) or gastroesophageal junction (GEJ) cancer. The first patient was dosed at a participating investigative site in China on Sept. 28.

“We are very pleased to have dosed the first patient in our FIGHT gastric cancer trial in China, where Zai Lab is responsible for the regulatory and development timeline for this global study,” said Helen Collins, M.D., Senior Vice President and Chief Medical Officer of Five Prime. “Tumors overexpressing FGFR2b are associated with a poor prognosis, and a targeted therapy that provides improved efficacy when added to standard therapy could transform treatment options for these patients. Bemarituzumab has demonstrated encouraging monotherapy activity in the late-line setting, and we hope to provide greater benefit by combining with chemotherapy in the front-line setting.”

Dr. Yongjiang Hei, CMO of Zai Lab said, "Gastric cancer is the fifth most common cancer in the world and the second most common in China. There is an urgent need globally, and particularly in China, where we are responsible for both development and commercialization, for more effective and well-tolerated targeted therapies for gastric cancer patients. We are pleased that the clinical trial application (CTA) was approved three months ahead of schedule, which will help accelerate the global FIGHT trial in our collaboration with Five Prime.”

GC, including GEJ cancer, is the fifth most common cancer worldwide and third leading cause of cancer death. Gastric cancer is the second most common cancer in China.

Current first-line chemotherapy treatment delays progression by approximately six months compared to best supportive care, but median OS remains poor with literature-reported ranges of approximately 10 to 11 months and PFS of approximately six months. The presence of FGFR2b overexpression is present in approximately 10% of patients with GC/GEJ and is associated with a worse prognosis. Few treatment options following progression are available after first-line chemotherapy, and a significant unmet need remains in the treatment of GC/GEJ worldwide.
Five Prime is developing companion diagnostics to identify FGFR2b overexpression using an immunohistochemistry (IHC) test and FGFR2 gene amplification using circulating tumor DNA (ctDNA) analysis. Five Prime will use both assays to select patients for the FIGHT trial.

Bemarituzumab is a first-in-class, isoform-selective, humanized monoclonal antibody in clinical development as a targeted immunotherapy for tumors that overexpress FGFR2b, a splice variant of a receptor for some members of the fibroblast growth factor (FGF) family. Bemarituzumab blocks FGFs 7, 10 and 22 from binding to FGFR2b, and has been engineered for enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) to increase direct tumor cell killing by recruiting natural killer (NK) cells. Clinical results to date suggest that the specificity of bemarituzumab avoids the dose-limiting toxicities that have been seen with less selective pan-FGFR tyrosine kinase inhibitors that act on multiple FGFRs, including FGFR2.
In December 2017, Five Prime and Zai Lab announced a strategic collaboration for the development and commercialization of bemarituzumab in Greater China.

Five Prime has nine additional candidates in development. Zai Lab is developing seven additional candidates.