The fight for two tumor types is poised to intensify, with BioNTech lining up a challenge to AstraZeneca, while SynOx Therapeutics is planning to enter a market served by companies including Daiichi Sankyo.
BioNTech’s data come from a phase 2 trial of its Duality Biologics-partnered antibody-drug conjugate (ADC) trastuzumab pamirtecan. The biotech reported a 49.3% response rate to the HER2-targeted ADC in a phase 2 cohort of 73 patients with HER2-expressing, advanced endometrial cancer who progressed on or after first-line chemotherapy and checkpoint inhibitor therapy, hitting its primary endpoint.
The primary analysis cohort was part of a broader study that included people without prior exposure to checkpoint inhibitor therapy. Across all 96 centrally tested patients, BioNTech reported a response rate of 47.9% and median progression-free survival of 8.1 months. The response rate fell to 44.1% in the full, 143-patient cohort, which included patients tested for HER2 at their trial site or local laboratory.
BioNTech said the safety profile was manageable and as expected for HER2-targeted ADCs. Almost 47% of patients had grade 3 or greater treatment-related adverse events. Almost 5% of patients had grade 3 or greater interstitial lung disease (ILD) or pneumonitis. AstraZeneca and Daiichi’s HER2-directed ADC Enhertu carries a boxed warning for ILD and pneumonitis.
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The FDA approved Enhertu in adults with unresectable or metastatic HER2-positive solid tumors in 2024. The tumor-agnostic authorization was supported (PDF) by data including a 56.3% response rate in 16 endometrial cancer patients. BioNTech, which hailed its trial as the largest in the indication, plans to file for FDA approval this year.
Separately, SynOx aims to file for FDA approval of emactuzumab in tenosynovial giant cell tumor (TGCT) patients in the second half of the year. SynOx outlined the plan as part of the release of phase 3 data on the CSF1R inhibitor, which achieved a significantly better response rate than placebo at Month 6 to hit the primary endpoint. The biotech also reported hits on secondary endpoints.
Daiichi won FDA approval for a CSF1R inhibitor, Turalio, in TGCT in 2019. Last year, Ono Pharmaceutical got the green light to sell a rival drug, Romvimza, that it acquired in its $2.4 billion takeover of Deciphera. Merck KGaA filed for FDA approval of another CSF1R inhibitor, pimicotinib, in the indication in January.
Having ceded a head start to rivals, SynOx is positioning the former Roche antibody emactuzumab as a differentiated, short-course treatment. Phase 3 participants received emactuzumab intravenously every two weeks for eight weeks. Turalio (PDF) and Romvimza (PDF) are given orally, respectively twice daily and twice weekly. Merck tested once-daily pimicotinib in its phase 3 trial.
