Astellas has struck its second immuno-oncology deal of the month. The latest pact will see the Japanese drugmaker pay Sutro Biopharma $90 million, plus potentially upward of $1 billion in biobucks, for rights to three immunostimulatory antibody-drug conjugates (iADCs), a modality designed to combine the best features of ADCs and personalized vaccine biology.
The modality is a product of Sutro’s XpressCF+ system. Using the system, the biotech can conjugate a cytotoxic and immune agonist payload on a single antibody and, based on early preclinical data, create precisely targeted therapeutics that are suitable for systemic administration. When the iADC reaches its target, it should kill tumor cells with its cytotoxic warhead and induce the release of an immune agonist to support development of anti-tumor immunity.
Sutro presented preclinical data on the approach last week, showing mice that experienced complete responses after treatment with an iADC remained cancer free after being rechallenged with tumor cells. The preclinical proof-of-concept data have landed Sutro a partner.
Astellas has tasked Sutro with developing iADCs for three targets. In return, the Japanese drugmaker will pay $90 million upfront and commit to up to $422.5 million in milestones per candidate. In the event all three candidates hit most of their milestones, Astellas will be on the hook for more than $1 billion, plus tiered royalties that cap out in the mid-teens. Sutro has an option to split costs and profits in the U.S.
Sutro will handle research and preclinical studies, using its linker technologies and other capabilities to create candidates that both directly kill tumor cells and stimulate the resulting immune response. Once a candidate reaches the clinic, Astellas will take over and handle further development.
The clinical trials will show whether iADCs can live up to their potential. In theory, the molecules should be able to treat the cold tumors that checkpoint inhibitors struggle to damage and thereby offer a new treatment option for the large proportion of patients who don’t respond to existing immunotherapies. That prospect aligns iADCs with Astellas’ immuno-oncology goal of addressing unmet needs that persist despite the availability of checkpoint inhibitors.