FDA Clears Exelixis, Sairopa’s SIRPα Antibody For Solid Tumor Trial

Exelixis Inc. and Sairopa B.V. have received the go-ahead from the U.S. FDA to begin a clinical trial assessing ADU-1805, a SIRPα monoclonal antibody in adults with advanced solid tumors. 

The two companies designed ADU-1805 to be active against all human alleles of SIRPα, which gives the drug the potential to treat a broader patient population than other SIRPα therapies. 

“The clearance of this Investigational New Drug Application for ADU-1805 is an exciting milestone for our expanding biologics pipeline, marking the first of many anticipated advancements we expect this year,” said Vicki L. Goodman, M.D., Executive Vice President, Product Development & Medical Affairs, and Chief Medical Officer, Exelixis. 

“Based on its best-in-class potential and broad applicability, we look forward to learning more about ADU-1805 from the upcoming phase 1 trial across multiple tumor types, as we continue toward our goal of finding innovative solutions for patients with advanced cancers.”

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Blocking the “Don’t-Eat-Me” Interaction between SIRPα and CD47

SIRPα is expressed by immune cells such as macrophages and dendritic cells. When it binds to CD47, also known as the “don’t-eat-me” signal, SIRPα triggers a signaling cascade that inhibits phagocytosis. Cancer cells often express CD47 as an immune escape mechanism.

Due to their therapeutic potential, the SIRPα/CD47 axis has been a target of major acquisitions and collaborations, such as Pfizer’s $2.3 billion acquisition of Trillium Therapeutics for a pair of SIRPα-Fc fusion proteins. Meanwhile, GS-0189, an anti-CD47 antibody and fruit of Gilead’s $4.7 billion buyout of Forty Seven, is undergoing a clinical trial in myelodysplastic syndrome. 

By blocking SIRPα, ADU-1805 could potentially improve the immune system’s ability to attack tumors. The antibody has also been optimized to bind preferentially to SIRPα compared to other members of the SIRP family. 

Under a collaboration established last November, Exelixis holds the option to license ADU-1805 and other anti-SIRPα antibodies upon review of data from Phase 1 clinical studies of ADU-1805, which would be conducted by Sairopa. The recent clearance from the FDA triggers a $35 million milestone payment to Sairopa, which would be paid in the first quarter of 2023. 

Author

Joy Lin

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