FS222: Improving outcomes in PD-L1 low tumors

Although many patients respond to PD-1 therapies, in some patients, the PD-1 blockade is not enough to activate immune cells, particularly in patients with low levels of PD-L1 on their tumor. These patients require additional pathways to be targeted to activate their immune system. FS222 simultaneously “releases the brake” on immune control of cancer by blocking the PD-1/PD-L1 pathway and “hits the gas” on immune activation by stimulating the CD137 pathway.  

Our approach for improving outcomes in PD-L1 low tumors: 

  • CD137/PD-L1 mAb² bispecific antibody
  • Conditional PD-L1 dependent activation of effector cells leading to profound anti-tumor activity in preclinical models
  • Conditionally active and FcgR null for improved safety
  • Potential clinical differentiation using our tetravalent mAb2 bispecific in patients with low tumor expressed PD-L1
  • CTA opened in 2020 and we plan to initiate a European Phase 1 study in 2021