A phase (Ph) I/II study of belinostat (Bel) in combination with cisplatin, doxorubicin, and cyclophosphamide (PAC) in the first-line treatment of advanced or recurrent thymic malignancies.
7103 Background: Belinostat is a hydroxamic acid histone deacetylase (HDAC) pan-inhibitor with single agent activity in thymic malignancies. PAC has activity against thymic cancers. Synergy between Bel and several chemotherapeutic agents, including P, A, and C, has been demonstrated in preclinical models. Methods: Patients with histologically confirmed, treatment naive advanced thymic malignancies, PS<2, measurable disease, and adequate renal, hepatic and hematopoietic functions were eligible. Ph1 evaluated safety and tolerability of the combination using increasing dose levels (DL) of Bel (1000-2000 mg/m² over 48 h CIVI) and PAC (50/50/500 mg/m² IV/cycle) (3+3 dose escalation schema), administered every 21 days for no more than 6 cycles followed by optional maintenance Bel every 4 weeks. Primary end point of Ph2 is overall response rate (ORR). Results: From March 2010 to January 2012, 13 patients were enrolled [7 thymoma (T), 6 thymic carcinoma (TC); 8 in Ph1 and 5 in Ph2; median age: 49 years (range, 23-76)]. In Ph1, 6 patients were treated at DL1 (Bel 1000 mg/m2+ PAC) and 2 patients at DL2 (Bel 2000 mg/m2+ PAC). Dose Limiting Toxicities were Grade 3 nausea and diarrhea, and Grade 4 neutropenia and thrombocytopenia. Recommended phase II dose (RP2D) was set at DL1. Most common grade 3/4 treatment-related adverse events (AE) were lymphocytopenia (100%), leucopenia (85%), neutropenia (77%) thrombocytopenia (54%), anemia (38%), hypophosphatemia (38%), hypomagnesemia, hypokalemia, elevated AST, prolonged QTc and infusion-catheter related thromboembolic complications (23% each). Outcomes included one complete response (CR; T at DL1), 6 partial responses (PR; 4 T, 2 TC; 4 in Ph1, 2 in Ph2) and 6 stable disease (SD; 2 T, 4 TC; 3 each in Ph1 and Ph2). Four patients previously deemed unresectable underwent surgical resection. Conclusions: Belinostat in combination with PAC has activity in thymic malignancies with a predicable AE profile. ORR was 54% including 33% PR in the TC subgroup. RP2D of the combination has been defined. Accrual to Ph2 part and molecular profiling of patient tumors is ongoing.