KT-333 diammonium functions as a molecular glue that targets and degrades the STAT3 protein. It selectively mediates the degradation of STAT3 via the ubiquitin-proteasome pathway by attaching to STAT3 and the E3 ubiquitin ligase von Hippel-Lindau protein (VHL). This compound exhibits strong specificity in degrading STAT3 and demonstrates significant antitumor activity. KT-333 diammonium is applicable in researching hematologic malignancies, including large granular lymphocytic leukemia (LGL-L), peripheral T-cell lymphoma (PTCL), and cutaneous T-cell lymphoma (CTCL).

KT-333 ammonium, after degrading STAT3, induces irreversible growth inhibition in the SU-DHL-1 cell line and activates caspase 3/7 activity, which is a hallmark of apoptosis [1]. It shows degradative effects on the STAT3 protein and, according to cell phenotypic analysis, has GI 50 values ranging from 8.1 to 57.4 nM across multiple ALCL cell lines [1].

KT-333 diammonium, administered intravenously at doses of 5, 10, 15, and 45 mg/kg once weekly for two consecutive weeks, exhibits dose-dependent antitumor activity. At 5 mg/kg, mice exhibited a tumor growth inhibition (TGI) of 79.9%, while doses of 10, 15, or 45 mg/kg led to complete tumor regression, effects that persisted until the study's conclusion [1]. KT-333 diammonium, at doses of 10, 20, and 30 mg/kg, also administered intravenously once weekly for two weeks, demonstrated similar dose-dependent antitumor properties. A TGI of 83.8% was observed at 10 mg/kg, and complete tumor regression was noted at 20 or 30 mg/kg, with results maintained through the study's end [1].