Gilead announced interim results from a Phase 2 study evaluating GS-9973 for the treatment of patients with relapsed or refractory hematologic malignancies. GS-9973 is an investigational reversible oral inhibitor of spleen tyrosine kinase (Syk), a protein that is critical for the activation, proliferation, and survival of B lymphocytes.

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This open-label, single-arm safety and efficacy study is evaluating GS-9973 in patients with relapsed or refractory  chronic lymphocytic leukemia (CLL) or non-Hodgkin’s lymphoma (NHL), including indolent NHL (iNHL), diffuse large B-cell lymphoma, and mantle cell lymphoma. Patients had received a median of two prior treatment regimens before study entry. The primary endpoint of the study is progression-free survival.

Results showed that among patients with chronic lymphocytic leukemia (CLL) who received at least eight weeks of GS-9973 monotherapy, 97% (n=28/29) experienced a reduction in lymph node size. Twenty (69%) out of the twenty-nine patients included in the efficacy analysis achieved greater than 50% tumor shrinkage, including four of seven patients with a chromosome 17p deletion and/or a mutation in the TP53 gene.

Gilead is also currently evaluating combination therapy with GS-9973 and its investigational oral inhibitor of PI3K delta, idelalisib, in a Phase 2 trial of patients with relapsed or refractory CLL, iNHL, and other lymphoid and hematological malignancies.

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