Amgen's Bemarituzumab Shows Promise in Phase III Gastric Cancer Trial

Amgen's investigational monoclonal antibody, bemarituzumab, has demonstrated significant improvement in overall survival when combined with chemotherapy for patients with advanced gastric or gastroesophageal junction (G/GEJ) cancer, according to recent Phase III trial results. This development marks a potential breakthrough in targeted therapy for gastric cancer, a disease often diagnosed at advanced stages with limited treatment options.

FORTITUDE-101 Trial Results

The Phase III FORTITUDE-101 study, which enrolled 547 patients across 37 countries, met its primary endpoint of improved overall survival. Patients with unresectable locally advanced or metastatic G/GEJ cancer, who were non-HER2 positive and had an overexpression of fibroblast growth factor receptor 2b (FGFR2b), received either bemarituzumab plus chemotherapy or chemotherapy alone.

While specific efficacy data were not disclosed, Amgen reported a "statistically significant and clinically meaningful improvement" in overall survival for the bemarituzumab combination compared to chemotherapy with placebo. This outcome builds on promising Phase II results, where the combination therapy demonstrated a median overall survival of 24.7 months versus 11.1 months with chemotherapy alone in FGFR2b-overexpressing patients.

Dr. Jay Bradner, Amgen's executive vice president for research and development, stated, "These first positive top-line results of an FGFR2b targeted monoclonal antibody from our Phase 3 FORTITUDE-101 study mark a meaningful advance in the development of effective targeted therapy for gastric cancer."

Safety Profile and Adverse Events

The most common treatment-emergent adverse events reported in the trial were predominantly ocular-related, including reduced visual acuity, dry eye, and corneal epithelium defect. Other frequent side effects included nausea, neutropenia, and anemia. Amgen noted that while these ocular events were observed in both treatment arms, they occurred with greater frequency and severity in the bemarituzumab group.

The safety profile appears consistent with earlier Phase II findings, where all patients experienced some adverse effects, many of which were eye or cornea-related. However, most events were reported to be reversible. Analysts from Guggenheim and William Blair have emphasized the importance of further details on the magnitude of benefit and the full safety and tolerability profile in assessing the drug's potential market opportunity.

Next Steps and Regulatory Outlook

Based on these interim results, Zai Lab, which holds co-development and commercialization rights for bemarituzumab in greater China, plans to prepare a regulatory submission in the region. Bemarituzumab has previously received breakthrough therapy designation from the FDA for gastric cancer patients with at least 10% of tumor cells overexpressing FGFR2b.

Amgen and Zai Lab are also conducting another Phase III trial combining bemarituzumab with nivolumab (Opdivo) and chemotherapy in first-line gastric cancer, with results expected in the second half of this year. These ongoing studies and future data presentations at medical meetings will be crucial in fully understanding bemarituzumab's efficacy and safety profile.

As the pharmaceutical industry continues to seek effective targeted therapies for difficult-to-treat cancers, bemarituzumab's progress represents a potentially significant step forward in gastric cancer treatment. However, the full impact of this development awaits more comprehensive data disclosure and regulatory review.