Amgen and Zai Lab eye a gastric niche

Amgen and Zai Lab have claimed a win with their anti-FGFR2b MAb bemarituzumab in phase 3, but full data will be needed to gauge the project’s risk/benefit profile. The companies said on Monday that Fortitude-101, testing a chemo combo in FGFR2b-overexpressing first-line gastric and gastroesophageal junction cancers, had met its primary overall survival endpoint at interim analysis.

However, ocular toxicity has long been a worry, being seen at any grade in 67% of bemarituzumab-treated patients in the phase 2 Fight trial. All the partners disclosed here was that, while ocular events were “consistent” with phase 2 and seen in both cohorts, “they occurred with greater frequency and severity in the phase 3 bemarituzumab arm”. Full results are expected at a future medical meeting.

Fortitude-101 enrolled patients with 10% or higher expression of FGFR2b, which is seen in around 16% of those with advanced gastric or GEJ cancers, according to the companies. This looks like a fairly small niche, although Zai has previously said it could amount to 100,000 patients in China. Zai gained Chinese rights via a deal with bemarituzumab’s originator Five Prime Therapeutics, before Amgen bought the latter in 2021 for $1.9bn.

Another phase 3 trial of bemarituzumab, Fortitude-2, is ongoing, testing an Opdivo/chemo triplet, also in ≥10% expressers. Data are due in the second half.

Amgen and Zai are well ahead of the pack in targeting FGFR2b; there aren’t too many other contenders, although a couple have started clinical development since the last time ApexOnco carried out this analysis. Most hopefuls are ADCs, including Allink’s ALK201, BeOne’s BG-C137 and Jiangsu Simcere’s SIM0686 (the last began a Chinese phase 1 trial in April). Still, Chia Tai’s TQB2210, also in phase 1 in China, is a MAb.

Phase 3 trials of bemarituzumab

Note: *FGFR2b ≥10% expression. Source: OncologyPipeline & company release.