29 pts (66% male) with STS with CDK4 amplification were enrolled from July 2016 to Nov 2019....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)....Monotherapy P demonstrated anti-tumor activity in heavily pre-treated pts with STS with CDK4 amplification.

60 patients with advanced WD/DDLS, age ≥ 18 years...Patients received oral palbociclib at 125mg daily for 21 days in 28-day cycles....All of the patients in the initial cohort had CDK4 amplification. In the expansion cohort, 5 patients had CDK4 amplification and the rest were not tested….In the initial cohort, 14 of the first 28 patients were progression free at 12 weeks...The overall PFS at 12 weeks was 57.2% (2-sided 95% CI: 42.4% – 68.8%). The median PFS was 17.9 weeks (2-sided 95% CI: 11.9 – 24.0 weeks).

Treatment with the CDK4 inhibitor PD0332991 was associated with a favorable progression-free rate in patients with CDK4-amplified and RB-expressing WDLS/DDLS who had progressive disease despite systemic therapy.