Laromustine, a sulfonyl hydrolyzing alkylating prodrug for cancer therapy
Service des Maladies du Sang, Centre François Magendie, Hôpital Haut-Lévêque, Avenue de Magellan, 33604 Pessac CEDEX, France.IDrugs: the investigational drugs journal (Impact Factor: 2.33). 02/2009; 12(1):39-53.
Laromustine (Onrigin), under development by Vion Pharmaceuticals Inc, belongs to the sulfonylhydrazine class of alkylating agents and is in clinical development for the treatment of malignancies. Laromustine is a prodrug that yields a chloroethylating compound (VNP-4090-CE) and a carbamoylating compound (methyl isocyanate). The antineoplastic effect of laromustine is attributed primarily to the chloroethylating species, which causes the preferential alkylation of DNA at the O6 position of guanine, a lesion that results in interstrand crosslinks and, eventually, cell death. The carbamoylating species contributes to antitumor activity by inhibiting the DNA repair protein O6-alkylguanine transferase. Early phase I clinical trials in patients with solid tumors indicated that laromustine was associated with myelosuppression; few extramedullary toxicities were observed, indicating potential efficacy for the treatment of hematological malignancies. Phase II trials have been completed in patients with previously untreated acute myelogenous leukemia (AML), high-risk myelodysplastic syndrome (MDS) and relapsed AML. The most encouraging results were observed in patients over 60 years of age with poor-risk de novo AML for which no standard treatment exists. Laromustine is currently in phase II/III trials for AML and phase II trials for MDS and solid tumors. Laromustine appears to be a promising agent that will add to the armamentarium of drugs available to treat patients who do not respond to, or are not fit for, intensive chemotherapy, such as elderly individuals.
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ABSTRACT: Human cytochrome P450 1A2 (CYP1A2) is one of the major CYPs in the liver (&sim13%) and metabolizes about 20% of clinically used drugs. CYP1A2 is a 515-residue protein with a molecular mass of 58,294 Dal. The recently published crystal structure of CYP1A2 in complex with α-naphthoflavone has showed a rather compact active site with a relatively small volume of the cavity of 375 Å3, which is 44.2% and 49.3% larger than that of CYP2A6 (260 Å3) and CYP2E1 (190 Å3), respectively. A series of residues in the substrate recognition regions of CYP1A2 (e.g. Arg108, Thr124, Thr223, Glu225, Phe226, Lys250, Arg251, Lys253, Asn312, Asp313, Glu318, Thr319, Asp320, Thr321, Val322, Leu382, Thr385, and Ile386) have been shown to play important roles in ligand-enzyme binding based on site-directed mutagenesis and homology modeling studies. Typical CYP1A2 substrates generally contain planar ring that can fit the narrow and planar active site of the enzyme, such as propranolol, clozapine, guanabenz, flutamide, imatinib, thalidomide, carbamazepine, lidocaine, theophylline, tacrine, tizanidine, zolpidem, riluzole, zileuton, and leflunomide. CYP1A2 is one of the major enzymes that bioactivate a number of procarcinogens including polycyclic aromatic hydrocarbons (e.g., benzo[a]pyrene), heterocyclic aromatic amines/amides (e.g. 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine), mycotoxins (e.g. aflatoxin B1) and some natural compounds such as aristolochic acids present in several Chinese herbal medicines. This enzyme also metabolizes several important endogenous compounds including retinols, melatonin, steroids, uroporphyrinogen and arachidonic acids. Like many of other CYPs, CYP1A2 is subject to induction and inhibition by a number of compounds. In particular, several therapeutic drugs including antofloxacin, carbamazepine, dihydralazine, furafylline, isoniazid, rofecoxib, clorgyline, thiabendazole, and zileuton are mechanism-based inhibitors of CYP1A2. Reversible and irreversible inhibition of by drugs CYP1A2 may provide an explanation for some clinical drug-drug interactions. Similar to CYP1A1 and 1B1, CYP1A2 is primarily regulated by the aromatic hydrocarbon receptor (AhR), a ligand-activated transcription factor and a basic helix-loop-helix protein belonging to the Per-Arnt-Sim family of transcription factors. CYP1A2 is polymorphic and a number of genetic mutations in CYP1A2 have been reported. It has been suggested that approximately 35 to 75% of the interindividual variability in CYP1A2 activity is due to genetic factors. Some of the mutations of CYP1A2 have been found to alter the clearance of drugs that are extensively metabolized by CYP1A2. Collectively, CYP1A2 plays a major role in drug metabolism, procarcinogen activation and some drug-drug interactions; it is important to identify whether a new drug is a substrate, inducer or inhibitor in drug development. This candidate selection might eventually lead to a less prominent role of this enzyme in the future for drug metabolism and minimize the potential for significant polymorphic metabolism in humans and drug-drug interactions when used in combination with CYP1A2 inhibitors.
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ABSTRACT: 1,2-Bis(methylsulfonyl)-1-(2-chloroethyl)-2-[[1-(4-nitrophenyl)ethoxy]carbonyl]hydrazine (KS119) is a prodrug of the 1,2-bis(sulfonyl)hydrazine class of antineoplastic agents designed to exploit the oxygen-deficient regions of cancerous tissue. Thus, under reductive conditions in hypoxic cells this agent decomposes to produce the reactive intermediate 1,2-bis(methylsulfonyl)-1-(2-chloroethyl)hydrazine (90CE), which in turn generates products that alkylate the O(6)-position of guanine in DNA. Comparison of the cytotoxicity of KS119 in cultured cells lacking O(6)-alkylguanine-DNA alkyltransferase (AGT) to an agent such as Onrigin, which through base catalyzed activation produces the same critical DNA G-C cross-link lesions by the generation of 90CE, indicates that KS119 is substantially more potent than Onrigin under conditions of oxygen deficiency, despite being incompletely activated. In cell lines expressing relatively large amounts of AGT, the design of the prodrug KS119, which requires intracellular activation by reductase enzymes to produce a cytotoxic effect, results in an ability to overcome resistance derived from the expression of AGT. This appears to derive from the ability of a small portion of the chloroethylating species produced by the activation of KS119 to slip through the cellular protection afforded by AGT to generate the few DNA G-C cross-links that are required for tumor cell lethality. The findings also demonstrate that activation of KS119 under oxygen-deficient conditions is ubiquitous, occurring in all of the cell lines tested thus far, suggesting that the enzymes required for reductive activation of this agent are widely distributed in many different tumor types.
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ABSTRACT: PURPOSE An international phase II study of laromustine (VNP40101M), a sulfonylhydrazine alkylating agent, was conducted in patients age 60 years or older with previously untreated poor-risk acute myeloid leukemia (AML). PATIENTS AND METHODS Laromustine 600 mg/m(2) was administered as a single 60-minute intravenous infusion. Patients were age 70 years or older or 60 years or older with at least one additional risk factor-unfavorable AML karyotype, Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 2, and/or cardiac, pulmonary, or hepatic comorbidities. Results Eighty-five patients (median age, 72 years; range, 60 to 87 years) were treated. Poor-risk features included age 70 years or older, 78%; adverse karyotype, 47%; PS of 2, 41%; pulmonary disease, 77%; cardiac disease, 73%; and hepatic disease, 3%. Ninety-six percent of patients had at least two risk factors, and 39% had at least four risk factors. The overall response rate (ORR) was 32%, with 20 patients (23%) achieving complete response (CR) and seven (8%) achieving CR with incomplete platelet recovery (CRp). ORR was 20% in patients with adverse cytogenetics; 32% in those age 70 years or older; 32% in those with PS of 2; 32% in patients with baseline pulmonary dysfunction; 34% in patients with baseline cardiac dysfunction; and 27% in 33 patients with at least four risk factors. Twelve (14%) patients died within 30 days of receiving laromustine therapy. Median overall survival was 3.2 months, with a 1-year survival of 21%; the median duration of survival for those who achieved CR/CRp was 12.4 months, with a 1-year survival of 52%. CONCLUSION Laromustine has significant single-agent activity in elderly patients with poor-risk AML. Adverse events are predominantly myelosuppressive or respiratory. Response rates are consistent across a spectrum of poor-risk features.
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