Amgen’s investigational monoclonal antibody paired with chemotherapy significantly improved overall survival for patients in a phase 3 stomach cancer trial compared to chemotherapy alone, according to the pharma.
Based on the interim results, Zai Lab—a biotech that holds co-development and commercialization rights for bemarituzumab in greater China—will prepare a regulatory submission for the cancer candidate in the country, according to a June 30 release.
The late-stage study, called Fortitude-101, enrolled 547 patients across 37 countries. All participants had unresectable locally advanced or metastatic gastric or gastroesophageal junction (G/GEJ) cancer, were non-HER2 positive and had an overexpression of fibroblast growth factor receptor 2b (FGFR2b).
At the center of the trial was bemarituzumab, a first-line candidate designed to target tumors overexpressing FGFR2b, which occurs in about 38% of patients with advanced G/GEJ cancer.
The study met its sole primary endpoint, with bemarituzumab and chemotherapy tied to a significant improvement in overall survival compared to chemotherapy by itself, according to the release. However, Amgen and Zai didn’t release any efficacy data behind the win, with more detailed findings slated for presentation at a future medical meeting.
Previously, in a phase 2 FGFR2b-overexpressing group of patients, bemarituzumab plus chemotherapy were linked to a median overall survival of 24.7 months versus 11.1 months with just chemotherapy.
As for safety in the phase 3 trial, the most common treatment-emergent adverse events for patients receiving the investigational combo were reduced visual acuity, corneal inflammation, anemia, neutropenia, nausea, corneal epithelial defect and dry eye.
Amgen said the ocular events were observed in both arms and consistent with phase 2 findings but that the events occurred with greater frequency and severity in the late-stage investigational arm. The companies didn’t share any other safety information at this time.
Analysts with William Blair said the ocular adverse event rates and discontinuation rates will be “important data points to evaluate the potential market opportunity,” in a June 30 note.
“Most patients with gastric cancer are diagnosed at an advanced stage, with poor prognosis, low survival rates and limited therapeutic options,” Amgen’s R&D head Jay Bradner, M.D., said in a release from the pharma. “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.”
A few years back, the FDA granted bemarituzumab breakthrough therapy status for gastric cancer patients with at least 10% of tumor cells overexpressing FGFR2b.
Back in 2021, Amgen picked up the phase 3-ready candidate in a $1.9 billion acquisition of Five Prime Therapeutics. The biotech had granted Zai Lab an exclusive license for bemarituzumab in mainland China, Hong Kong, Macau and Taiwan, rights the biotech still retains.
Now, the companies are also running another phase 3 trial of the investigational combo plus nivolumab—marketed as Opdivo—in first-line gastric cancer, with a readout expected in the second half of this year.