Preliminary Safety, Pharmacokinetics, Pharmacodynamics and Clinical Activity of KT-333, a Targeted Protein Degrader of STAT3, in Patients with Relapsed or Refractory Lymphomas, Large Granular Lymphocytic Leukemia, and Solid Tumors

Background:KT-333is a first-in-class, potent, highly selective, heterobifunctional small molecule degrader of the signal transducer and activator of transcription 3 (STAT3) protein. Aberrant activation of STAT3 resulting from activating mutations or deregulated cytokine signaling underlies various malignancies including peripheral T-cell lymphomas (PTCL), cutaneous T-cell lymphoma (CTCL), and large granular lymphocytic leukemia (LGL-L). Approximately 70% of human cancers including hematological malignancies and solid tumors exhibit increased levels of phosphorylated STAT3 (pSTAT3), a biomarker of pathway activation. In non-clinical studies, treatment with KT-333 resulted in durable tumor regressions with weekly (QW) or once every two weeks IV administration in STAT3-dependent T cell lymphomas. STAT3 degradation also sensitized immunocompetent mouse models of solid and liquid cancers to anti-PD1(ASH 2021, SITC 2021).