Plasma-Based Companion Diagnostic Assay for Targeted Immuno-Oncology Drug Candidate Bemarituzumab

Personal Genome Diagnostics Inc. (PGDx) has announced that it has entered into a collaboration with Five Prime Therapeutics Inc. to develop a plasma-based companion diagnostic assay, for use with Five Prime’s first-in-class investigational drug candidate - bemarituzumab, an anti-FGFR2b antibody (also known as FPA144). The diagnostic assay will be used in Five Prime’s global registrational study (the FIGHT trial) 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 plans to use immunohistochemistry and circulating tumor DNA (ctDNA) tests to identify the estimated 10% of patients with gastric and gastroesophageal junction cancer who would be eligible for treatment with bemarituzumab. Under the collaboration, PGDx will develop and validate a plasma-based ctDNA in vitro diagnostic (IVD) assay to help identify patients whose tumors are FGFR2 gene-amplified and therefore eligible for treatment with bemarituzumab, initially for the Phase 3 portion of the FIGHT trial. PGDx intends to submit the assay for regulatory approval and commercialize it in the United States, Europe, Japan, China and other countries.

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“We are pleased to collaborate with PGDx, a cancer genomics pioneer with a wealth of experience in accurately identifying genomic alterations in tumors,” said Aron Knickerbocker, Chief Executive Officer of Five Prime. “Patients with advanced gastric and gastroesophageal junction cancer need new treatment options. 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.

Bemarituzumab is being evaluated in the FGFR2b Inhibition in Gastric and GastroesopHageal Junction Cancer Treatment (FIGHT) Phase 1/3 clinical trial, a global registrational study in patients with advanced gastric or gastroesophageal junction cancer whose tumors overexpress FGFR2b or have FGFR2 gene amplification. The Phase 3 portion of the trial is expected to begin in the second half of 2018.

Doug Ward, Chief Executive Officer of PGDx noted: “Five Prime’s bemarituzumab has shown encouraging activity against important genetic variants of certain gastric cancers that lack effective treatment options. We welcome the opportunity to work with Five Prime to develop accurate and accessible diagnostic assays to identify patients who may benefit from this promising new drug. 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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