Results of a completed phase I trial of CBL0137 administered intravenously (IV) to patients (Pts) with advanced solid tumors.

Abstract

3583 Background: The novel curaxin CBL0137 intercalates into DNA, interfering with histone/DNA binding. Consequent trapping of histone chaperone FACT leads to MYC, NF-kB, and HSF1 inhibition, p53 activation, and an IFN response. CBL0137 shows broad nonclinical antitumor activity (Gasparian et al. Sci Transl Med. 2011; 3(95):95ra74). Methods: This dose-ranging study assessed the CBL0137 maximum tolerated dose (MTD) and recommended Phase 2 dose (RP2D) and CBL0137 safety, pharmacokinetics (PK), and efficacy in adults with advanced treatment-refractory solid tumors. CBL0137 was administered IV on Days 1, 8, and 15 of repeated 28-day cycles until progressive disease (PD) or unacceptable toxicity. Doses were escalated using a 3+3 design based on Cycle 1 dose-limiting toxicities (DLTs). PK was assessed through 168 hours after Day 1. Efficacy was evaluated every 8 weeks. Results: The study enrolled 83 pts (M/F [n] = 49/34; median [range] age = 64 [33-85] years; ECOG status [n] = 1/2 [32/51]), with cancer types (n) of colorectal (23), prostate (7), glioblastoma (6), liver (6), non-small-cell (5), and others (36) across 17 dose levels from 10 to 700 mg/m2/infusion. Durations of therapy ranged to 24 months. Cycle 1 DLTs (n type) were observed at 240 mg/m2 (1 Gr 3 photosensitivity), 400 mg/m2 (1 Gr 3 anemia), 700 mg/m2 (1 Gr 4 thrombocytopenia, 1 Gr 4 neutropenia/Gr 4 thrombocytopenia), and 650 mg/m2 (1 Gr 3 thrombocytopenia, 1 Gr 4 neutropenia/Gr 3 thrombocytopenia). Nausea and vomiting were successfully prevented with dexamethasone/serotonin antagonists. Photosensitization was effectively managed with sun protection. Peripheral venous thrombosis required central vein infusion in subjects with glioblastoma. PK showed dose-proportional increases in plasma CBL0137 area under the concentration-time curve (AUC), a high mean (range) volume of distribution (Vd) of 1,030 (655-1460) L/m2 consistent with extensive tissue distribution and DNA intercalation, and an average mean (range) half-life (t1/2) of 24.7 (10.3-40.7) hours without dose dependence. The best response was stable disease: 2 pts with liver cancer had tumor control for 9 and 24 months and a maximum tumor regression of 10%; 2 pts with prostate cancer had tumor regressions by 11% and 22%; 1 pt with uterine cancer had a 20% tumor regression. Conclusions: CBL0137 administered IV was generally well tolerated with manageable toxicities The MTD and RP2D were estimated at 540 mg/m2 due to myelosuppressive DLTs. PK were predictable. Preliminary evidence of antitumor activity supports Phase 2 testing. Clinical trial information: NCT01905228 .