GS-9901

GS-9901 is an orally bioavailable, highly selective small molecule inhibitor of the delta isoform of phosphoinositide 3-kinase (PI3Kδ). It binds selectively to PI3Kδ and inhibits its activity, thereby blocking the PI3Kδ-mediated signaling pathway. This inhibition prevents proliferation and survival of tumor cells that overexpress PI3Kδ, while sparing normal cells and reducing toxicity. GS-9901 was developed as a potential immunomodulating and antineoplastic agent for hematologic malignancies such as chronic lymphocytic leukemia, marginal zone B-cell lymphoma, refractory follicular lymphoma, and small lymphocytic lymphoma. The drug reached Phase 1 clinical trials but development has been discontinued[1][5][7].