Phase 1 dose-expansion study of oral TP-1287, a cyclin-dependent kinase 9 (CDK9) inhibitor, in patients with Ewing sarcoma (EWS).

Abstract

TPS11589 Background: Cyclin-dependent kinase 9 (CDK9) blockade inhibits tumor growth and progression by impairing the transcription of key oncogenes, such as myeloid cell leukemia-1 (MCL-1) and c-MYC. CDK9 overexpression has been observed in sarcoma patients (pts), and CDK9 has emerged as a potential therapeutic target in pts with sarcoma. TP-1287 is an investigational orally delivered phosphate prodrug of the CDK9 inhibitor alvocidib. In preclinical studies, TP-1287 has been shown to decrease MCL-1 expression and phosphorylation of RNA polymerase II (RPB1), and inhibit tumor growth in an Ewing sarcoma (EWS) mouse model. Phase 1 dose-escalation in solid tumors has completed and TP-1287 is being investigated in a dose expansion cohort in pts with EWS (NCT03604783). The design of the expansion part of the trial in pts with EWS is herein described. Methods: Up to thirty pts with EWS will be enrolled in this dose expansion cohort. Key eligibility criteria are age ≥18 years (≥12 years, if weight ≥40 kg); histologically confirmed locally advanced or metastatic unresectable EWS; received 1 to 5 prior lines of treatment including an anthracycline; one or more measurable tumors per the RECIST v1.1; ECOG performance status of ≤1; acceptable liver and renal function, and acceptable hematologic and coagulation status; no treatment with surgery, chemotherapy, or investigational therapy within 28 days or 5 half-lives. Eligible pts will be treated with oral TP-1287 monotherapy RP2D established from the dose escalation part (11 mg BID, continuous dosing in a 28-day treatment cycle) and will continue treatment until treatment-related adverse event or disease progression. Assessments will be performed on Day 1 and Day 15 of each cycle. Tumor response assessment will be done after Cycle 2 and at the end of every other cycle thereafter. The primary objectives are objective response rate (ORR) and clinical benefit rate (CBR) ; secondary objectives are median progression-free survival (PFS), PFS rate at 16-weeks and 24-weeks and safety; and exploratory objectives include evaluation of systemic exposure and pharmacodynamics. Safety data will be reviewed on an ongoing basis and a Bayesian approach will be used to assess the efficacy data. Statistical analysis for safety and efficacy parameters will be primarily descriptive in nature. EWS dose expansion cohort is currently recruiting in the United States. Clinical trial information: NCT03604783 .