Summit Therapeutics has cleared out an asset from its pre-ivonescimab history, offloading the antibiotic candidate ridinilazole to the OpenAI-backed startup Biossil for $500,000 upfront.
Going into 2021, ridinilazole was Summit’s top priority. The failure of the molecule to beat vancomycin in a phase 3 trial of patients with Clostridioides difficile infection prompted the biotech to pivot, leading it to terminate ridinilazole development in September 2022 and pay Akeso $500 million upfront for rights to ivonescimab weeks later. The pivot followed the FDA’s request for data from another phase 3 trial.
Summit sought a buyer for ridinilazole but, with the hoped-for deal never materializing and ivonescimab becoming one of the hottest assets in biopharma, the antibiotic prospect became a footnote in the biotech’s history. The company made no references to ridinilazole in its 2025 annual report.
Yet Biossil sees value in the asset. The Toronto-based biotech is paying $500,000 and committing up to $104.5 million in regulatory and commercial milestones for the drug candidate, furthering its strategy of salvaging failed programs.
In April, Biossil exited stealth with $70 million from investors including OpenAI and Founders Fund and plans to use AI to identify failed molecules that deserve a second chance. The biotech broke cover before its formal coming-out party when, in October 2025, Galera Therapeutics revealed it struck a deal to sell assets including avasopasem for $3.5 million. Avasopasem failed a phase 3 trial in a radiotherapy complication.
Like Summit, Galera scrapped development after the FDA requested data from another phase 3 study. Biossil has shown a willingness to run new trials to try to rescue assets, starting a phase 3 clinical trial of senicapoc in sickle cell disease almost 20 years after Icagen halted a late-phase trial early for futility. The biotech has also taken over a completed trial of a sickle cell prospect, rivipansel, developed by Pfizer.