Five Prime Therapeutics Begins Dose Expansion in Gastric Cancer Patients With FGFR2b Over-Expression in Phase 1 Trial of FPA144

Five Prime Therapeutics, Inc.

, a clinical-stage biotechnology company focused on discovering and developing novel protein therapeutics for cancer and inflammatory diseases, announced that the dose escalation part of the ongoing Phase 1 trial of FPA144 has been completed and that dose expansion at has begun at a selected dose in new cohorts of gastric cancer patients whose tumors overexpress FGFR2b. FPA144 is an isoform-selective antibody in development as a targeted therapy for tumors that over-express FGFR2b, and has been engineered for enhanced ADCC, increasing direct tumor cell killing by recruiting natural killer (NK) cells. FGFR2 gene amplification is found in a number of tumors, including approximately 5% of gastric cancers, and is associated with poor prognosis. Part 1 of the Phase 1 study evaluated the safety and pharmacokinetics (PK) of escalating doses of FPA144 in 27 patients with solid tumors, including unselected gastric cancer patients. Data from Part 1 will be presented at the American Society of Clinical Oncology's (ASCO) 2016 Gastrointestinal Cancers Symposium in San Francisco. The poster entitled, "FPA144-001: A first in human study of FPA 144, an ADCC-enhanced, FGFR2b isoform-selective monoclonal antibody in patients with advanced solid tumors," is scheduled during the session entitled, "Cancers of the Esophagus and Stomach," on Thursday, January 21, 2016 from 12:30-2:00 and 5:30-7:00 Pacific Time. Abstracts are expected to be posted on the meeting website on Tuesday, January 19, 2016. Enrollment has begun in Part 2 of the trial, evaluating the efficacy of biweekly infusions of FPA144 in approximately 70 metastatic gastric cancer patients, with the aim of exploring the correlation between efficacy and FGFR2b overexpression. Tumor testing for FGFR2b overexpression is being conducted centrally, using a proprietary immunohistochemistry assay. Tumors are also being assessed for FGFR2 gene amplification by FISH analysis. Trial endpoints include safety, pharmacokinetics, response rate and duration of response. "We are really pleased with the progress we are making in this study and to now be moving into our target population of gastric cancer patients," said Julie Hambleton, M.D., Executive Vice President and Chief Medical Officer of Five Prime. "This is an orphan indication in the U.S. and given the unmet need in this disease and the potential for patients to benefit greatly from new treatment options, we aspire to develop the program expeditiously. In the Phase 1 study, we are already enrolling at global sites, including in Asia where gastric cancer is most prevalent. We are also running preclinical studies to evaluate therapeutic combinations with FPA144 for future testing in gastric cancer patients and to identify other indications that may be suitable for FPA144 therapy."