Targeting the myeloid checkpoint receptor SIRP alpha potentiates innate and adaptive immune responses to promote anti-tumor activity.
Kuo, T.C., Chen, A., Harrabi, O., Sockolosky, J.T., Zhang, A., Sangalang, E., Doyle, L.V., Kauder, S.E., Fontaine, D., Bollini, S., Han, B., Fu, Y.X., Sim, J., Pons, J., Wan, H.I.(2020) J Hematol Oncol 13: 160-160
- PubMed: 33256806 
- DOI: https://doi.org/10.1186/s13045-020-00989-w
- Primary Citation of Related Structures:  
7KPG - PubMed Abstract: 
Signal regulatory protein α (SIRPα) is a myeloid-lineage inhibitory receptor that restricts innate immunity through engagement of its cell surface ligand CD47. Blockade of the CD47-SIRPα interaction synergizes with tumor-specific antibodies and T-cell checkpoint inhibitors by promoting myeloid-mediated antitumor functions leading to the induction of adaptive immunity. Inhibition of the CD47-SIRPα interaction has focused predominantly on targeting CD47, which is expressed ubiquitously and contributes to the accelerated blood clearance of anti-CD47 therapeutics. Targeting SIRPα, which is myeloid-restricted, may provide a differential pharmacokinetic, safety, and efficacy profile; however, SIRPα polymorphisms and lack of pan-allelic and species cross-reactive agents have limited the clinical translation of antibodies against SIRPα. Here, we report the development of humanized AB21 (hAB21), a pan-allelic anti-SIRPα antibody that binds human, cynomolgus monkey, and mouse SIRPα alleles with high affinity and blocks the interaction with CD47.
Organizational Affiliation: 
ALX Oncology, Burlingame, CA, USA. tracy@tallactx.com.