Formation of active products of benzaldehyde dimethane sulfonate (NSC 281612, DMS612) in human blood and plasma and their activity against renal cell carcinoma lines

Characterization of the metabolism of benzaldehyde dimethane sulfonate (NSC 281612, DMS612)

INTRODUCTION

Benzaldehyde dimethane sulfonate (BEN, DMS612, NSC281612) is a bifunctional alkylating agent currently in clinical trials. We previously characterized the degradation products of BEN in plasma and blood. The conversion of BEN to its carboxylic acid analogue (BA) in whole blood, but not plasma, suggests that an enzyme in RBCs may be responsible for this conversion. BEN conversion to BA was observed in renal carcinoma cells and appeared to correlate with IC₅₀. To better understand the pharmacology of BEN, we aimed to evaluate the metabolism and enzymes potentially responsible for the conversion of BEN to BA.

METHODS

Human red blood cells (RBC) were used to characterize kinetics and susceptibility to enzyme-specific inhibitors. Recombinant enzymes were used to confirm metabolism of BEN to BA. Analytes were quantitated with established LC-MS/MS methods.

RESULTS

Average apparent Vmax and Km were 68 ng/mL min(-1) [10% RBC](-1) and 373 ng/mL, respectively. The conversion of BEN to BA in RBC was not inhibited by carbon monoxide, nitrogen gas, or menadione, an inhibitor of aldehyde oxidase. The conversion was inhibited by disulfiram, an inhibitor of ALDH. Of available ALDH isoforms ALDH1A1, ALDH3A1, ALDH2, and ALDH5A1, only ALDH1A1 converted BEN to BA.

CONCLUSION

The activating conversion of BEN to BA is mediated not by CYP450 enzymes or aldehyde oxidase, but by ALDH1A1. This enzyme, a potential stem cell marker, may be a candidate biomarker for clinical activity of BEN.

A phase i study of DMS612, a novel bifunctional alkylating agent

PURPOSE

DMS612 is a dimethane sulfonate analog with bifunctional alkylating activity and preferential cytotoxicity to human renal cell carcinoma (RCC) in the NCI-60 cell panel. This first-in-human phase I study aimed to determine dose-limiting toxicity (DLT), maximum tolerated dose (MTD), pharmacokinetics (PK), and pharmacodynamics (PD) of DMS612 administered by 10-minute intravenous infusion on days 1, 8, and 15 of an every-28-day schedule.

EXPERIMENTAL DESIGN

Patients with advanced solid malignancies were eligible. Enrollment followed a 3+3 design. PKs of DMS612 and metabolites were assessed by mass spectroscopy and PD by γ-H2AX immunofluorescence.

RESULTS

A total of 31 patients, including those with colorectal (11), RCC (4), cervical (2), and urothelial (1) cancers, were enrolled. Six dose levels were studied, from 1.5 mg/m(2) to 12 mg/m(2). DLTs of grade 4 neutropenia and prolonged grade 3 thrombocytopenia were observed at 12 mg/m(2). The MTD was determined to be 9 mg/m(2) with a single DLT of grade 4 thrombocytopenia in 1 of 12 patients. Two patients had a confirmed partial response at the 9 mg/m(2) dose level, in renal (1) and cervical (1) cancer. DMS612 was rapidly converted into active metabolites. γ-H2AX immunofluorescence revealed dose-dependent DNA damage in both peripheral blood lymphocytes and scalp hairs.

CONCLUSIONS

The MTD of DMS12 on days 1, 8, and 15 every 28 days was 9 mg/m(2). DMS612 appears to be an alkylating agent with unique tissue specificities. Dose-dependent PD signals and two partial responses at the MTD support further evaluation of DMS612 in phase II trials.

Benzaldehyde suppresses murine allergic asthma and rhinitis

To evaluate the antiallergic effects of oral benzaldehyde in a murine model of allergic asthma and rhinitis, we divided 20 female BALB/c mice aged 8-10 weeks into nonallergic (intraperitoneally sensitized and intranasally challenged to normal saline), allergic (intraperitoneally sensitized and intranasally challenged to ovalbumin), and 200- and 400-mg/kg benzaldehyde (allergic but treated) groups. The number of nose-scratching events in 10 min, levels of total and ovalbumin-specific IgE in serum, differential counts of inflammatory cells in bronchoalveolar lavage (BAL) fluid, titers of Th2 cytokines (IL-4, IL-5, IL-13) in BAL fluid, histopathologic findings of lung and nasal tissues, and expressions of proteins involved in apoptosis (Bcl-2, Bax, caspase-3), inflammation (COX-2), antioxidation (extracellular SOD, HO-1), and hypoxia (HIF-1α, VEGF) in lung tissue were evaluated. The treated mice had significantly fewer nose-scratching events, less inflammatory cell infiltration in lung and nasal tissues, and lower HIF-1α and VEGF expressions in lung tissue than the allergic group. The number of eosinophils and neutrophils and Th2 cytokine titers in BAL fluid significantly decreased after the treatment (P<0.05). These results imply that oral benzaldehyde exerts antiallergic effects in murine allergic asthma and rhinitis, possibly through inhibition of HIF-1α and VEGF.

Effects of the aldehyde dehydrogenase inhibitor disulfiram on the plasma pharmacokinetics, metabolism, and toxicity of benzaldehyde dimethane sulfonate (NSC281612, DMS612, BEN) in mice

PURPOSE

Benzaldehyde dimethane sulfonate (DMS612, NSC281612, BEN) is an alkylator with activity against renal cell carcinoma, currently in phase I trials. In blood, BEN is rapidly metabolized into its highly reactive carboxylic acid (BA), presumably the predominant alkylating species. We hypothesized that BEN is metabolized to BA by aldehyde dehydrogenase (ALDH) and aimed to increase BEN exposure in blood and tissues by inhibiting ALDH with disulfiram, thereby shifting BA production from blood to tissues.

METHODS

Female CD2F1 mice were dosed with 20 mg/kg BEN iv alone or 24 h after 300 mg/kg disulfiram ip. BEN, BA, and metabolites were quantitated in plasma and urine, and toxicities were assessed.

RESULTS

BEN had a plasma t½ <5 min and produced at least 12 products. The metabolite half-lives were <136 min. Disulfiram increased BEN plasma exposure 368-fold (AUC0-inf from 0.11 to 40.5 mg/L min), while plasma levels of BA remained similar. Urinary BEN excretion increased (1.0-1.5 % of dose), while BA excretion was unchanged. Hematocrit, white blood cell counts, and percentage lymphocytes decreased after BEN administration. Coadministration of disulfiram appeared to enhance these effects. Profound liver pathology was observed in mice treated with disulfiram and BEN.

CONCLUSIONS

BEN plasma concentrations increased after administration of disulfiram, suggesting that ALDH mediates the rapid metabolism of BEN in vivo, which may explain the increased toxicity seen with BEN after administration of disulfiram. Our results suggest that the coadministration of BEN with drugs that inhibit ALDH to patients that are ALDH deficient may cause liver damage.