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Five Prime Therapeutics Reports Bemarituzumab Shrunk Gastric Tumors in Phase I Trial

NEW YORK – Clinical-stage biotech company Five Prime Therapeutics reported data from their Phase I trial of bemarituzumab (FPA144) in patients with FGFR2b-overexpressing gastric and gastroesophageal junction adenocarcinoma (GEA) in the Journal of Clinical Oncology Friday.

In the study, five patients with high FGFR2b-overexpressing GEA had a partial response, yielding an overall response rate of 17.9 percent.

"Monotherapy activity of bemarituzumab and its lack of significant overlapping toxicities with standard chemotherapeutic agents suggest that combining bemarituzumab with chemotherapy may potentially benefit patients in the front-line setting whose GEA tumors overexpress FGFR2b," Daniel Catenacci, lead investigator on the trial, said in a statement.

The results are from a three-part, open-label Phase I trial involving 79 participants. The first part, with 19 patients, focused on dose escalation in patients with recurrent solid tumors. The second part, with eight patients, escalated bemarituzumab's dose in patients with advanced GEA. The third part, with 52 patients, also explored the right dosing for patients with advanced GEA that overexpressed FGFR2b at four different levels (high, medium, low, none) and one cohort of advanced bladder cancer overexpressing FGFR2b.

No dose-limiting toxicities occurred, and the recommended dose determined is 15 mg/kg every two weeks. Some mild treatment related symptoms such as fatigue, nausea, and dry eye were observed, and two patients had grade 3 adverse events. No treatment-related adverse events of grade 4 or above was reported, which indicated to investigators that the drug was well-tolerated.

Bemaritizumab blocks FGFR2b activation, which enhances cancer cell killing. Approximately 30 percent of front-line gastric cancer is FGFR2b positive. The company said at the JP Morgan Healthcare conference earlier this year that it hopes the antibody's specificity will make it less toxic than oral FGFR tyrosine kinase inhibitors.