A phase II study of ribociclib in men with unresectable, incurable teratoma with recent progression.

517Background: Most patients with teratoma are managed by surgery and no standard medical therapy exists for progressive and/or unresectable teratoma. Teratomas have functional expression of retinoblastoma protein and clinical activity was observed with CDK4/6 inhibition (Vaughn DJ, et al. Cancer. 2015). Here, we report results with the CDK4/6 inhibitor ribociclib (RIBO) for unresectable teratoma. Methods: This multicenter, double-blind study enrolled patients (pts) ≥ 15 years old with unresectable, progressive teratoma without malignant transformation, ECOG PS 0-1, and ≥ 1 line of prior chemotherapy. Pts were randomized (2:1) to receive RIBO (600 mg/day, 3 weeks on/1 week off) or placebo (PBO). Crossover to RIBO was permitted following progressive disease (PD) on PBO. The primary endpoint was progression-free survival (PFS). Secondary endpoints included additional efficacy measures, safety, and tolerability. Results: The trial was closed prematurely in the setting of slow accrual. Ten pts were randomized...