F-star Therapeutics presents clinical data on antitumor activity of FS222

F-star Therapeutics announced new clinical data from its potentially best-in-class clinical asset FS222, a CD137/PD-L1 targeting tetravalent bispecific antibody, at the European Society of Medical Oncology Immuno-Oncology Annual Congress in Geneva. In preclinical models, engagement of PD-L1 and CD137 by FS222 induced T cell proliferation and cytokine production that was associated with significant tumor regression compared to the combination of CD137 and PD-L1 targeting monospecific antibodies. Phase 1 interim efficacy and safety results on FS222 as of July 20: 33 patients had been treated to date with FS222; one non-squamous NSCLC, PD-L1 naive patient experienced a complete response at 8 weeks, at a dose of 1mg/kg. The CR has remained persistent for 40.9 weeks as of 20th July 2022. 6 patients had disease stabilization, 16 had progressive disease, 2 were discontinued before week 8, and 8 were awaiting their week 8 evaluation. FS222 showed a manageable safety profile with most adverse events Grade 1-2. One patient experienced a DLT of Grade 3 febrile neutropenia. No patients discontinued FS222 due to an AE. Maximum tolerated dose was not reached, and dose escalation is ongoing. The pharmacological activity was demonstrated by increased peripheral soluble target receptors and proliferating CD4+ and CD8+ T cells.