Summit Therapeutics Inc. (NASDAQ: SMMT) has signed an agreement to sell ridinilazole, an investigational Phase III antibiotic, to Toronto-based Biossil, Inc., according to a press release from the company.

Under the terms of the deal, Summit will receive $500,000 upfront and up to $104.5 million in regulatory and commercial milestone payments, plus tiered royalties on net sales.

Ridinilazole was previously evaluated in Summit's Phase III Ri-CoDIFy study for the treatment of C. difficile infection (CDI). The study showed a higher observed Sustained Clinical Response rate compared with vancomycin but did not meet the primary endpoint for superiority within the established time boundaries. Results were announced in December 2021 and later published in the journal Clinical Infectious Diseases.

Biossil describes itself as an AI-native biopharma company with teams in Toronto and Boston. The company said it plans to continue clinical development of ridinilazole.

"We believe Biossil's AI-native development capabilities and focus on urgent unmet medical needs make them well positioned to advance this program, while allowing Summit to continue prioritizing our core oncology strategy and the development of ivonescimab," said Robert W. Duggan, Chairman and Co-Chief Executive Officer of Summit.

Ridinilazole has not been approved by the U.S. Food and Drug Administration, and its safety and efficacy have not been evaluated by regulatory authorities.