Phase I pharmacokinetic (PK) and pharmacodynamic (PD) study of intravenous dimethane sulfonate (DMS612, NSC 281612) in advanced malignancies.

Abstract

2553 Background: DMS612 is a dimethane sulfonate compound that was identified as preferentially cytotoxic to renal cell carcinoma (RCC) cell lines in a chemical screen of the NCI-60 panel. DMS612 has bifunctional alkylating activity in vitro. Objectives of this first-in-human phase I study included determining the dose-limiting toxicity (DLT), maximum tolerated dose (MTD), recommended phase 2 dose (RP2D), PK and PD of DMS612 administered by 10 minute intravenous infusion on day 1, 8 and 15 of a 28 day cycle. Methods: Eligibility criteria included adults with advanced solid malignancies or lymphoma with ECOG performance status 0-2, life expectancy > 3 months and adequate organ and marrow function. Patients were enrolled using a standard “3+3” dose escalation scheme. Plasma PK of DMS612 and metabolites was assessed by LC-MS/MS. DNA damage PD was assessed by γ-H2AX immunofluorescence. Results: 35 subjects were enrolled (22 male, 13 female) with median age 59 years (41-75). Tumor types included colorectal (8), RCC (4), cervix (2), and urothelial (2). Doses administered were 1.5, 3, 5, 7, 9 and 12 mg/m2. The MTD was determined to be 9 mg/m2, with only one DLT of grade 4 thrombocytopenia in 12 subjects enrolled. The maximum administered dose of 12 mg/m2 was considered to be intolerable after 1 of 3 subjects had grade 4 neutropenia and 1 had prolonged grade 3 thrombocytopenia. Prolonged thrombocytopenia in later cycles was observed in other subjects, including one patient naïve to prior cytotoxic chemotherapy. One subject with RCC had a confirmed partial response at 7 mg/m2. DMS612 was rapidly converted into carboxy, chloroethyl and hydroxyethyl analogues and their glucuronides, some of which retained alkylating activity in vitro. Dose-dependent pharmacodynamic evidence of DNA damage induced by DMS612 in vivo was observed by γ-H2AX immunofluorescance in both peripheral blood lymphocytes and plucked scalp hairs. Conclusions: The MTD of DMS12 administered by intravenous infusion on day 1, 8 and 15 of a 28-day cycle was 9 mg/m2. Pre-clinical and clinical observations suggest that further study of DMS612 in RCC is warranted.