Immunosuppressive properties of chloroquinoxaline sulfonamide

Antitubulin sulfonamides: The successful combination of an established drug class and a multifaceted target

Tubulin, the microtubules and their dynamic behavior are amongst the most successful antitumor, antifungal, antiparasitic, and herbicidal drug targets. Sulfonamides are exemplary drugs with applications in the clinic, in veterinary and in the agrochemical industry. This review summarizes the actual state and recent progress of both fields looking from the double point of view of the target and its drugs, with special focus onto the structural aspects. The article starts with a brief description of tubulin structure and its dynamic assembly and disassembly into microtubules and other polymers. Posttranslational modifications and the many cellular means of regulating and modulating tubulin's biology are briefly presented in the tubulin code. Next, the structurally characterized drug binding sites, their occupying drugs and the effects they induce are described, emphasizing on the structural requirements for high potency, selectivity, and low toxicity. The second part starts with a summary of the favorable and highly tunable combination of physical-chemical and biological properties that render sulfonamides a prototypical example of privileged scaffolds with representatives in many therapeutic areas. A complete description of tubulin-binding sulfonamides is provided, covering the different species and drug sites. Some of the antimitotic sulfonamides have met with very successful applications and others less so, thus illustrating the advances, limitations, and future perspectives of the field. All of them combine in a mechanism of action and a clinical outcome that conform efficient drugs.

A phase II study of chloroquinoxaline sulfonamide (CQS) in patients with metastatic colorectal carcinoma (MCRC)

PURPOSE

Phase II multicenter study investigated the efficacy and toxicity of the novel halogenated derivative of sulfaquixonaline Chloroquinoxaline Sulfonamide (CQS) in metastatic colorectal cancer.

EXPERIMENTAL DESIGN

Eligible patients with metastatic or recurrent colorectal cancer received CQS at a dose schedule of 2000 mg/m2 over an hour weekly for 4 weeks every 42 days. Treatment was continued until unexpected toxicity or disease progression.

RESULTS

A total of seventeen patients were enrolled on this study. 94% of all patients enrolled had prior treatment. Sixteen patients were evaluable for response with fifteen patients showing evidence of disease progression and one patient with prolonged stable disease. One patient had non-evaluable disease. Following this interim analysis, the drug was considered ineffective and the study was terminated early. The most frequent adverse event was anemia. No patients discontinued the treatment because of toxicity.

CONCLUSION

CQS, when given at a dose of 2000 mg/m2 weekly for 4 weeks every 42 days to patients with metastatic colorectal cancer, does not result in significant tumor regression.

Phase I and pharmacokinetic study of E7070, a novel chloroindolyl sulfonamide cell-cycle inhibitor, administered as a one-hour infusion every three weeks in patients with advanced cancer

PURPOSE

The objectives were to determine the maximum-tolerated dose, the recommended dose, the dose-limiting toxicity, the pharmacokinetics, and the activity of E7070, a novel cell-cycle inhibitor.

PATIENTS AND METHODS

E7070 was given as a 1-hour intravenous infusion every 3 weeks in two groups of patients with advanced solid tumors who met prespecified eligibility criteria (group A) or who met the same eligibility criteria but in addition were less heavily pretreated and had more favorable liver functions (group B).

RESULTS

Forty patients (31 patients in group A and nine patients in group B) were entered. Dose escalation proceeded through eight levels (range, 50 to 1,000 mg/m(2)). In group A, neutropenia and thrombocytopenia were dose-limiting toxicities occurring during the first cycle in two of seven patients treated at the doses of 700 mg/m(2) and two of four patients treated at 800 mg/m(2). Identical dose-limiting toxicities were observed in zero of six and two of three patients from group B at doses of 800 and 1,000 mg/m(2), respectively. Other toxicities included acne-like skin eruption, mucositis, conjunctivitis, nausea, fatigue, and alopecia. At doses greater than 400 mg/m(2), the area under the concentration-time curve increased disproportionately to the administered dose. Tumor stabilization lasting > or = 6 months was observed in six assessable patients.

CONCLUSION

The recommended doses of E7070 in this schedule were 700 mg/m(2) (group A) and 800 mg/m(2) in patients who were less heavily pretreated (group B) with a moderate tumor burden. Prolonged disease stabilization observed in this study might warrant further investigation of E7070 in selected tumor types.

Arylsulfonyl-N,N-diethyl-dithiocarbamates: a novel class of antitumor agents

A series of alkyl/arylsulfonyl-N,N-diethyl-dithiocarbamates has been prepared by reaction of sodium N,N-diethyldithiocarbamate with alkyl/arylsulfonyl halides. The reactivity of these new derivatives against cysteine and glutathione has been investigated in order to identify derivatives that might label a critical cysteine residue of tubulin (Cys 239 of human beta2 tubulin chain). Some of the most reactive compounds showed moderate to powerful tumor growth inhibitory properties against several leukemia, non-small cell lung, ovarian, melanoma, colon, CNS, renal, prostate and breast cancer cell lines in vitro.

Preclinical antitumor efficacy of analogs of XK469: sodium-(2-[4-(7-chloro-2-quinoxalinyloxy)phenoxy]propionate

A series of quinoxaline analogs of the herbicide Assure was found to have selective cytotoxicity for solid tumors of mice in a disk-diffusion-soft-agar-colony-formation-assay compared to L1210 leukemia. Four agents without selective cytotoxicity and 14 agents with selective cytotoxicity were evaluated in vivo for activity against a solid tumor. The four agents without selective cytotoxicity in the disk-assay were inactive in vivo (T/C > 42%). Thirteen of the fourteen agents with selectivity in the disk-assay were active in vivo (T/C < 42%). Five of the agents had curative activity. These five agents had a halogen (F, Cl, Br) in the 7-position (whereas Assure had a CI in the 6 position). All agents with curative activity were either a carboxylic acid, or a derivative thereof, whereas Assure is the ethyl ester of the carboxylic acid. All other structural features were identical between Assure and the curative agents. Assure had no selective cytotoxicity for solid tumors in the disk-assay, and was devoid of antitumor activity. The analog XK469 is in clinical development.

Clinical and pharmacology study of chloroquinoxaline sulfonamide given on a weekly schedule

The in vitro human tumor colony-forming assay identified chloroquinoxaline sulfonamide (CQS) as an active agent at human plasma concentrations of > 100 micrograms/ml. In the initial phase I trial of CQS given every 28 days, peak plasma concentrations > 500 micrograms/ml were associated with reversible dose-limiting hypoglycemia and occasional cardiac arrhythmias. Therefore, we evaluated whether a weekly schedule of treatment might minimize the drug-associated toxicity while maintaining potential therapeutic concentrations. CQS was given intravenously over 1 h once per week for 4 weeks to 12 patients, beginning at a dose of 2,000 mg/m2. All patients underwent monitoring for cardiac arrhythmias and hypoglycemia. Plasma drug levels were measured following each dose. Mild hypoglycemia was the most common adverse effect. A median nadir plasma glucose concentration of 56 mg/dl was observed at a weekly dose of 2,500 mg/m2. Two patients experienced cardiac dysrhythmia while on study. Continuous electrocardiographic monitoring failed to identify any significant infusion-related arrhythmia. The median CQS plasma concentration measured 24 h following a 2,000-mg/m2 dose of CQS was > 100 micrograms/ml, and the cumulative area under the concentration x time curve (AUC) determined at concentrations of > or = 100 micrograms/ml was similar to that observed with the every-28-day schedule. The weekly schedule described herein appears to maximize the plasma AUC with an acceptable margin of safety. The recommended phase II dose and schedule for CQS is 2,000 mg/m2 given once per week. Although severe hypoglycemia is unlikely, glucose monitoring is appropriate for 6 h following CQS administration.

Immune stimulation by an antisense oligomer complementary to the rev gene of HIV-1

Mice developed massive splenomegaly and polyclonal hypergammaglobulinemia within 2 days after intravenous injection of a phosphorothioate oligomer that is antisense to a portion of the rev region of the HIV-1 genome. Histologic examination of spleens from injected animals showed marked expansion of a uniform-appearing population of small lymphocytes and many mitoses. Spleen mononuclear cells (SMNCs) from injected animals showed approximately a 10-fold-increased uptake of [3H]thymidine and production of IgM and IgG. Flow cytometry analysis indicated that the responding cells were predominantly B-lymphocytes. The anti-rev oligomer also was mitogenic in vitro and stimulated immunoglobulin production by normal mouse SMNCs and human peripheral blood mononuclear cells. Similar immunologic effects were observed with an anti-rev 21-mer phosphorothioate, truncated at the 3' end, but not with a 20-mer human p53 antisense phosphorothioate or a 28-mer anti-rev phosphodiester. These observations are consistent with the possibility that DNA sequences homologous to the rev gene participate in the regulation of mammalian lymphocyte activation, proliferation and maturation.

Chloroquinoxaline sulfonamide: a sulfanilamide antitumor agent entering clinical trials

Chloroquinoxaline sulfonamide (CQS) has been developed to the clinical trial stage based on its activity in the Human Tumor Colony Forming Assay (HTCFA). In the HTCFA, CQS demonstrated inhibition of colony formation against breast, lung, melanoma and ovarian carcinomas. The mechanism of action of CQS is unknown. It does not appear to inhibit folate metabolism as does the structurally similar sulfaquinoxaline. Preclinical toxicology studies in dogs and rats have shown that CQS is toxic to lymphoid organs, bone marrow, gastrointestinal tract, pancreas, CNS, adrenal glands and testes. Toxicity was generally reversible with the exception of testicular atrophy in dogs and rats which occurred late and was not reversible within the study time frame. The pharmacokinetic data indicate that CQS binds to serum proteins in a dose and species specific manner. Terminal half-lives appear to vary between species from 60 hours in mice, 15 hours in rats, and 45-132 hours in dogs. Preliminary data indicate a longer terminal half-life in humans. Two phase I trials are ongoing using a 60 min infusion schedule once every 28 days. The starting dose for each trial was 18 mg/m2.