Amgen's Five Prime takeover delivers gastric cancer win

Four years after buying Five Prime for $1.9 billion, Amgen has promising phase 3 results with a drug for gastric cancer that was the focal point for the deal.

The new data comes from the FORTITUDE-101 looking at bemarituzumab plus chemotherapy as a front-line therapy for FGFR2b-positive advanced gastric cancer, and has revealed a significant improvement in overall survival (OS) compared to placebo plus chemo.

FGFR2b – fibroblast growth factor receptor 2b – is an emerging biomarker that is particularly prominent in gastric cancer and gastroesophageal junction (GEJ) cancer, occurring in around 38% of cases, and seems to promote the proliferation of tumour cells.

Bemarituzumab is directed against the receptor and is designed to inhibit the signalling pathways promoting tumour growth. The study involved patients with a level of FGFR2b expression – 2+/3+ staining intensity in 10% of tumour cells or more – that is seen in around 16% of patients with gastric and GEJ cancers.

Amgen acquired Five Prime in 2021 on the back of the phase 2 FIGHT trial of bemarituzumab, which achieved significant improvements in overall survival, progression-free survival, and overall response rate compared to chemo alone.

The deal came as Amgen was looking to build its pipeline in the face of the loss of market exclusivity for immunology blockbuster Enbrel (etanercept), at the time a near-$5 billion product.

Details of the FORTIRUDE-101 study will have to wait until the results are presented at a future medical congress. Still, the positive result bodes well for a second phase 3 study of bemarituzumab with chemo and Bristol Myers Squibb's PD-1 inhibitor Opdivo (nivolumab) in first-line gastric and GEJ cancer, FORTITUDE-102, which is due to read out in the latter half of this year.

"Most patients with gastric cancer are diagnosed at an advanced stage, with poor prognosis, low survival rates, and limited therapeutic options," said Jay Bradner, Amgen's R&D chief.

"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," he added.

Gastric cancer is the fifth leading cause of cancer-related death worldwide, with nearly one million new cases and over 650,000 deaths globally each year. GlobalData has predicted that bemarituzumab could make US sales of $500 million in the US alone in the next 10 years.

Gastric cancer is particularly prevalent in Asia-Pacific countries, a key growth market for Amgen. The company is working on the development of bemarituzumab in collaboration with China's Zai Lab, which holds co-development and commercialisation rights for bemarituzumab for mainland China, Hong Kong, Macau, and Taiwan.