Source: Getty Images
Source: Getty Images

Personal Genome Diagnostics (PGDx) announced it will collaborate with Five Prime Therapeutics to develop a plasma-based companion diagnostic assay for use with Five Prime's first-in-class investigational drug candidate, bemarituzumab. The diagnostic assay will be used in Five Prime's global registrational study of bemarituzumab in combination with 5-fluorouracil (5-FU), leucovorin, and oxaliplatin, as front-line treatment in patients with advanced gastric or gastroesophageal junction cancer whose tumors overexpress FGFR2b or have FGFR2 gene amplification.

Five Prime will use IHC and ctDNA tests to identify the estimated 10% of patients with gastric and gastroesophageal junction cancer who would be eligible for treatment with bemarituzumab. Plans call for PGDx to develop and validate a plasma-based ctDNA in vitro diagnostic assay to help identify patients whose tumors are FGFR2 gene-amplified and therefore eligible for treatment with bemarituzumab. Initial use of the IVD will be for the phase 3 portion of the FGFR2b Inhibition in Gastric and Gastroesophageal Junction Cancer Treatment (FIGHT) Phase clinical trial, expect to begin later this year.

“Patients with advanced gastric and gastroesophageal junction cancer need new treatment options,” said Aron Knickerbocker, CEO of Five Prime, in a press release. “Prognosis is especially poor for patients whose tumors overexpress FGFR2b or have FGFR2 gene amplification. We believe that a targeted therapy like bemarituzumab may provide a clinical benefit in this setting and expect that PGDx's plasma-based assay will be an accessible and flexible tool to inform patient selection.”

Bemarituzumab is an isoform-selective, humanized monoclonal antibody in clinical development as a targeted immuno-therapy for tumors that overexpress FGFR2b, a splice variant of a receptor for some members of the fibroblast growth factor (FGF) family, or amplify the FGFR2 gene. Bemarituzumab has also 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 toxicities that have been seen with less selective pan-FGFR tyrosine kinase inhibitors that act on multiple FGFRs, including FGFR2.

Doug Ward, CEO of PGDx, noted: “Five Prime's bemarituzumab has shown encouraging activity against important genetic variants of certain gastric cancers that lack effective treatment options. This collaboration reflects our commitment to provide companion diagnostics in the form of regulated, standardized IVD kits to ensure they are widely available to patients around the globe.”

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