PRS-343: Addressing Biology That Has Been Intractable for Monoclonals

Candidate Targets Indication Partner Our Commercial
Discovery Preclinical IND-
Phase I Phase IIa
PRS-343 4-1BB/HER2
Immuno-Oncology Worldwide
Discovery Phase completed
Pre-Clinical Phase completed
IND-enabling Phase completed
Phase 1 in progress
Phase 2 not started

PRS-343 is combining a CD137-specific Anticalin with a HER2-targeting antibody in a bispecific compound with the intent of trafficking an anti-CD137 therapeutic protein to the tumor microenvironment.

PRS-343 is a bivalent, bispecific fusion protein targeting CD137 (4-1BB) and HER2 comprising an agonistic CD137-targeting Anticalin genetically linked to a HER2-targeting antibody. CD137 is a key costimulatory immunoreceptor and a member of the TNF-receptor (TNFR) superfamily.

While multiple lines of evidence show that CD137 is a highly promising therapeutic target in cancer, current mAb approaches are not designed to achieve a tumor-mediated activation and, therefore, may display toxicity and a limited therapeutic window due to peripheral T cell and NK cell activation. To overcome this limitation, we generated PRS-343, which is designed to promote CD137 clustering by bridging CD137-positive T cells with HER2-positive tumor cells, thereby providing a potent costimulatory signal to tumor antigen-specific T cells.