Stem Cell Therapeutics Corp. has announced that it will be providing an update on its SIRPaFc immune checkpoint inhibitor program, targeting the CD47 protein, at the 105th Annual Meeting of the American Association for Cancer Research.
The meeting will be held April 5-9, 2014 in San Diego, CA. Details of the poster presentation, entitled “Cancer Immunotherapy Targeting CD47: Wild Type SIRPaFc is the Ideal CD47-Blocking Agent to Minimize Unwanted Erythrocyte Binding”, are listed below:
Date: Wednesday April 9, 2014
Time: 8:00 am - 12:00 pm (PT)
Session ID: Immunology 11
Session Title: Immune Checkpoint Inhibition
Abstract #: 5011
Presenter: Dr. Robert Uger, Chief Scientific Officer
Location: Hall A-E, Poster Section 10, San Diego Convention Center
The company will present data demonstrating that its wild type SIRPaFc fusion protein, which binds effectively to CD47 with low nanomolar affinity, binds very poorly to human red blood cells (RBCs) compared to both commercial anti-CD47 monoclonal antibodies (mAbs) and proprietary CD47-blocking agents.
This striking difference in binding was not seen with other cell types, including acute myeloid leukemia (AML) tumor cells, suggesting it is an RBC-specific phenomenon. In addition, the lack of significant SIRPaFc binding to erythrocytes is unique to humans, since SIRPaFc bound strongly to mouse and non-human primate RBCs.
Overall, the data suggest that a wild type SIRPaFc fusion protein may be the ideal CD47-blocking agent to reduce the potential antigen sink effect caused by RBCs and to minimize hematological toxicity in patients, while maintaining potent anti-tumor effects.
“Our results are consistent with independently published reports documenting differences in binding between CD47-specific antibodies and the natural CD47 ligand, SIRPa. While the mechanism behind this observation is still under investigation, our preliminary data suggest that it may relate to unique structural features of CD47 in the human RBC membrane,” commented Dr. Uger.
Dr. Uger continued, “Importantly, our results indicate that our SIRPaFc protein has a preferable RBC binding profile compared to competing approaches, which we believe may predict a lower risk of toxicity in patients and a more favorable pharmacokinetic profile.”