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Exelixis, Sairopa to Begin Phase I Trial of ADU-1805 in Advanced Solid Tumors

NEW YORK – Exelixis and Sairopa announced Monday that they will begin a first-in-human clinical trial of the investigational SIRPα-blocking antibody ADU-1805 in patients with advanced solid tumors. 

The companies are starting the Phase I trial now that the US Food and Drug Administration has cleared their investigational new drug application for ADU-1805. Exelixis and Sairopa will evaluate ADU-1805's safety, pharmacokinetics, and target binding across multiple tumor types. Because the drug is meant to bind to all known human variants of signal-regulatory protein alpha, or SIRPα, patients will not need to undergo screening for the biomarker prior to enrolling in the trial. However, the firms have identified other biomarkers that are modulated when ADU-1805 binds to SIRPα, and investigators will analyze them alongside early signs of clinical efficacy.

Under the terms of a November 2022 deal between the two firms, the FDA's clearance of the IND for ADU-1805 triggers a $35 million milestone payment that Alameda, California-based Exelixis must pay to Sairopa, based in Rotterdam, Netherlands. In that deal, Exelixis paid $40 million upfront and committed to paying an additional $70 million in near-term milestones in exchange for the option to exclusively commercialize and develop ADU-1805 and any other anti-SIRPα antibodies. After the completion of prespecified Phase I studies, Exelixis can still exercise its option for an additional $225 million.

ADU-1805 is meant to block the SIRPα-CD47 checkpoint, binding preferentially to SIRPα as opposed to other SIRP family members, which the firms believe will improve the immune system's ability to attack tumors. "Based on its best-in-class potential and broad applicability, we look forward to learning more about ADU-1805 from the upcoming Phase I trial across multiple tumor types," Vicki Goodman, Exelixis' chief medical officer and executive VP of product development and medical affairs, said in a statement.