Abstract B112: A dose escalation and cohort expansion study of the CDK9 inhibitor KB-0742 in relapsed, refractory ovarian cancer and transcriptionally addicted relapsed or refractory solid tumors

Abstract

Abstract Ovarian cancer is responsible for more female cancer deaths than any other female reproductive malignancy. MYC deregulation is a hallmark of ovarian cancer and is associated with poor clinical outcome. In a real-world cohort (n=1,667), the MYC family of genes is overexpressed and/or genomically amplified in up to 87% of ovarian cancer. Although MYC remains undrugged, targeting of its cofactors has emerged as an attractive strategy to inhibit MYC oncogenic activity. Cyclin-dependent kinase 9 (CDK9) is a critical regulator of oncogenic MYC expression and activity. KB-0742 is an orally bioavailable, highly selective, long half-life (~24 hours) CDK9 inhibitor that demonstrates promising preclinical activity against ovarian cancer and is currently being evaluated in a phase 1/2 dose escalation and cohort expansion study in patients with ovarian cancer and other transcriptionally addicted tumors (NCT04718675). The phase 1/2 study is being conducted in two parts: dose escalation (part 1) and cohort expansion (part 2). Part 2 is comprised of cohort A (solid tumors with high prevalence of MYC overexpression including ovarian cancer, non-small cell lung cancer, and triple negative breast cancer) and cohort B (other transcriptionally addicted tumor types including sarcomas, adenoid cystic carcinoma, nut midline carcinoma and small cell lung cancer). KB-0742 is dosed orally once daily for 3 consecutive days, followed by 4 days off, on a weekly basis in 28-day cycles until unacceptable toxicity or disease progression. It is estimated that up to 170 patients will be enrolled in the study. Part 1 dose escalation is open to patients with relapsed or refractory solid tumors or non-Hodgkin’s lymphoma. Part 2 is defined by tumor indications as described in cohorts A and B. Eligibility criteria include age > 18 years (≥ 12 years old and with a body weight ≥ 40 kg in part 2, cohort B), acceptable organ function, and ECOG PS < 2. Primary objectives include evaluation of pharmacokinetics (PK), pharmacodynamics (PD), safety, tolerability, and preliminary anti-tumor activity, with the goal of identifying a maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D). Plasma PK measurements include Cmax, tmax, AUC0-last, accumulation ratio (Racc) and t1/2. Safety data will be evaluated per the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) v5.0. Dose escalation and MTD identification is guided by a Modified Continuous Reassessment Method (mCRM) (Goodman et al., Stat Med 1995). RP2D is informed by PD in peripheral blood mononuclear cells using assays to evaluate phosphorylation of the CDK9 substrate serine 2 on the RNA Polymerase II C-terminal domain (pSER2) and CDK9-responsive gene expression. Radiographic tumor response is assessed using RECIST 1.1 criteria. Exploratory objectives include assessment of KB-0742 PD in tumor tissue and profiling of treatment-related genomic, transcriptomic, and proteomic changes. Enrollment continues in the United States with sites in Spain, France, and UK expected to open. Citation Format: Miguel Villalona-Calero, Monica Mita, Alain Mita, Noah Federman, Drew Rasco, David Spigel, Jia Luo, Gregory M. Cote, Richard E. Cutler, Pavan Kumar, Crystal J. MacKenzie, Charles Lin, Jorge F. DiMartino, Elizabeth A. Olek, Brian Van Tine. A dose escalation and cohort expansion study of the CDK9 inhibitor KB-0742 in relapsed, refractory ovarian cancer and transcriptionally addicted relapsed or refractory solid tumors [abstract]. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_2):Abstract nr B112.