Palbociclib (P) in patients (pts) with soft tissue sarcoma (STS) with CDK4 amplification: Results from the Targeted Agent and Profiling Utilization Registry (TAPUR) study.

Abstract

11565 Background: TAPUR is a phase II basket study evaluating anti-tumor activity of commercially available targeted agents in pts with advanced cancers with genomic alterations. Results in a cohort of STS pts with CDK4 amplification treated with P are reported. Methods: Eligible pts had advanced STS, no standard treatment options, measurable disease, ECOG PS 0-2, and adequate organ function. Genomic testing was performed in CLIA-certified, CAP-accredited site selected labs. Pts received P at 125 mg orally once daily for 21 days, followed by 7 days off until disease progression. Pts matched to P had CDK4 amplification and no RB mutations. Simon 2-stage design tested the null disease control (DC) - defined as partial (PR), complete response (CR) or stable disease at 16+ weeks (SD 16+) - rate of 15% vs. 35% (power = 0.85; α = 0.10). If ≥2 of 10 pts in stage 1 have DC, 18 more pts are enrolled. If ≥7 of 28 pts have DC, the null DC rate is rejected. Secondary endpoints are progression-free survival (PFS), overall survival (OS) and safety. Results: 29 pts (66% male) with STS with CDK4 amplification were enrolled from July 2016 to Nov 2019. 1 pt was not evaluable and excluded from efficacy analyses. Demographics and outcomes are summarized in Table. One pt with partial response (PR) and 12 pts with SD16+ were observed for DC and objective response (OR) rates of 48% (95% CI: 31%, 62%) and 3.7% (95% CI: 0.1%, 19%), respectively, and the null DC rate of 15% was rejected (p<0.001). 9/13 pts with DC continued on treatment for >32 weeks. 14 pts had at least one grade 3-4 AE at least possibly related to P with the most common being low WBC/platelets. Other grade 3 AEs included increased alanine aminotransferase, anemia, and fatigue. Conclusions: Monotherapy P demonstrated anti-tumor activity in heavily pre-treated pts with STS with CDK4 amplification. Additional study is warranted to confirm the efficacy of P in pts with STS with CDK4 amplification. Clinical trial information: NCT02693535. [Table: see text]