Five Prime Therapeutics Presents Data from Safety Lead-in to Phase 3 FIGHT Trial of Bemarituzumab at 2019 American Society of Clinical Oncology (ASCO) Gastrointestinal (GI) Cancers Symposium - Seite 2

The Phase 3 portion of the FIGHT trial will evaluate bemarituzumab in combination with mFOLFOX6 versus placebo plus mFOLFOX6 in approximately 550 patients with gastric cancer (GC) or gastroesophageal junction (GEJ) cancer whose tumors overexpress FGFR2b. The Phase 3 portion of the trial began in September 2018 and will include more than 250 sites in the U.S., Europe and Asia.

The primary endpoint of the FIGHT trial is overall survival (OS) with secondary endpoints of progression-free survival (PFS), objective response rate (ORR), safety and pharmacokinetic (PK) parameters.

Previous Bemarituzumab Trial Results

Data from a Phase 1 clinical trial of single-agent bemarituzumab were presented at the 2017 ASCO Annual Meeting. Bemarituzumab demonstrated single-agent activity and an acceptable safety profile in heavily pretreated patients with metastatic gastric cancer whose tumors overexpress FGFR2b.

Efficacy:

• In 21 treated patients with late-line GC/GEJ and high FGFR2b overexpression:
  • ORR was 19.0% with 4 confirmed PRs
  • Disease control rate at 6 weeks: 57.1%
  • Median duration of response was 15.4 weeks

Safety:

• Bemarituzumab was well tolerated
• There were no dose-limiting toxicities
• Maximum tolerated dose was not reached during dose escalation

Unmet Need in GC and GEJ

GC, including GEJ cancer, is the fifth most common cancer worldwide and third leading cause of cancer death. The presence of FGFR2 gene amplification or FGFR2b overexpression is associated with a worse prognosis and is present in 10% of patients with GC/GEJ.

Current first-line chemotherapy treatments prolong survival by approximately 6 months compared to best supportive care, but median OS remains poor with literature-reported ranges of approximately 10 to 11 months and PFS from 5 to 5.6 months. An unmet medical need exists in the treatment for GC/GEJ since few treatment options following progression are available after first-line chemotherapy.

Companion Diagnostic Development for FGFR2b

Five Prime is using companion diagnostics to identify FGFR2b overexpression using an IHC test and FGFR2 gene amplification using ctDNA analysis. Five Prime will use both assays to select patients for the FIGHT trial to identify the estimated 10% of patients with gastric and GEJ tumors that would qualify for the trial.

About Bemarituzumab

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 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.