[CANCER RESEARCH 44, 2352-2357, June 1984] Treatment of Human Glioma and Medulloblastoma Tumor Lines in Athymic Mice with Diaziquone and Diaziquone-based Drug Combinations S. Clifford Schold, Jr.,1 Henry S. Friedman,2 Thorir D. Bjornsson,3 and Darell D. Bigner4 Departments ol Medicine (Neurology) ¡S.C. S.J, Pediatrics [H. S. F.], Pharmacology (Clinical Pharmacology) [T. D. B.], and Pathology (Neuropathology) [D. D. B.], Duke University Medical Center, Durham, North Carolina 27710 ABSTRACT We used diaziquone (NSC 182986) alone and in combination with other antineoplastic drugs to treat six human glioma and one human medulloblastoma tumor lines growing s.c. in athymic mice. Pharmacokinetic studies of diaziquone in the plasma of athymic mice indicated rapid clearance with a half-life of approx imately 11.5 min. Diaziquone produced significant growth delays in at least one experiment using each of seven different tumor lines, and it produced consistent and significant delays in five of the seven. There was no obvious difference between a single dose and a dose administered once daily for 5 days, and tumor regressions to a volume smaller than that at treatment were uncommon in any of the single-drug experiments. Using our most extensively characterized human glioma line, D-54 MG, we found striking enhancement of the therapeutic effect by using nontoxic combinations of either diaziquone and carmustine (1,3- bis(2-chloroethyl)-1 -nitrosourea, NSC 409962) or diaziquone and procarbazine (NSC 77213). These combinations produced sig nificant increases in the median growth delay, significant in creases in the number of tumor regressions, and some instances in which no palpable tumors were present 100 days after treat ment. In contrast, in experiments using diaziquone-based chem otherapy combinations with either cyclophosphamide, c/s-plati- num, or vincristine, there was only slight enhancement of the therapeutic effect. These results, using human glioma and me dulloblastoma tumor lines in athymic mice, suggest a broad range of activity of diaziquone against primary nervous system tumors and enhancement of its therapeutic effect with either 1,3- bis(2-chloroethyl)-1 -nitrosourea or procarbazine. If Phase II and Phase III clinical trials corroborate these findings, the value of the nude mouse system for the evaluation of new therapeutic approaches to brain neoplasms would be further confirmed. INTRODUCTION Diaziquone is a lipid-soluble synthetic benzoquinone that has been introduced recently into clinical trials for the treatment of patients with primary anaplastic tumors of the nervous system. Its potential importance lies in its impressive efficacy against standard animal brain tumor models (12), its activity against 1Recipient of support from NIH Grant R01-NS-20581. To whom requests for reprints should be addressed, at Box 2905, Duke University Medical Center, Durham, NC 27710. 2 Recipient of a Brain Tumor Research Association fellowship, in memory of Bryce Davis, and of American Cancer Society Junior Faculty Clinical Fellowship 707. 3 Nanaline H. Duke Scholar. 'Recipient of support from NIH Grants PO1-NS 20023, R01-CA 11898, and PO1-CA 32672. Received December 15,1983; accepted March 2,1984. human brain tumors in early clinical trials (1, 5, 6, 19), and its modest toxicity in humans (14). Little is known yet about its spectrum of efficacy, mechanisms of sensitivity and resistance, optimal doses, mode of administration, or schedules, and its use in combination with other agents active against human brain tumors. In this paper, we are reporting pharmacokinetic data of diaziquone in athymic mice, its activity against a series of human brain tumor lines growing in these animals, and the activity of diaziquone-based chemotherapy combinations against D-54 MG, the most extensively characterized glioma line available in this laboratory. Results indicate rapid plasma clearance in mice, variable sensitivity of the tumor lines to the drug, and enhance ment of the therapeutic effect of diaziquone by combination with other agents, notably BCNU5 and procarbazine. MATERIALS AND METHODS Animals. Homozygous nu/nu BALB/c athymic mice at least 6 weeks old were used for these experiments. Animals were derived from an independent breeding colony at Duke University and maintained as described previously (4,18). Drug Administration and Toxicity. Diaziquone was supplied by the Division of Cancer Treatment of the National Cancer Institute. The parent compound was dissolved in dimethyl acetamide and diluted in phosphate buffer (0.01 M. pH 6.5). The lethal toxicity of diaziquone in our animal colony was determined by probit analysis using 3 doses between an LD,o and an LD«, (21 ). An LD10dose was calculated for both a once daily for 5 days schedule and a single dose. The drug was administered i.p. in a volume of 30 ml/sq m. Procarbazine HCI was supplied by Hoffmann- La Roche Inc., Nutley, NJ. The other drugs were purchased commer cially. All animals were weighed twice weekly after drug administration. Analysis of Plasma Diaziquone. Concentrations of diaziquone were determined in plasma samples pooled from 3 non-tumor-bearing animals at each time point after a single i.p. injection of the drug. Samples were obtained at 5,15, 30, and 60 min after a single injection of 26 mg/sq m and at 10, 30, 60, and 120 min after a single injection of 6.75 mg/sq m. The blood was collected after decapitation and anticoagulated with heparin. The plasma volumes obtained from each animal at each time point were similar. Plasma diaziquone was analyzed by a high-pressure liquid Chromatographie assay (11). The lower limit of sensitivity of this method is approximately 20 ng/ml. The coefficient of variation of the assay of 3.0%. The elimination half-life, f«,of diaziquone was determined by linear regression analysis after transformation of diaziquone concen trations to natural logarithmic values; the slope of the regression line is -ß,and the half-life is 0.693/0. Total clearance was determined from the total area under the plasma diaziquone concentration versus time curve, which was measured by the trapezoidal method, with the area after the last data point being determined by dividing plasma diaziquone at that time by ß;total clearance is dose divided by area under curve. The 5The abbreviationsused are: BCNU, 1,3-bis(2-chloroethyl)-1-nitrosourea;LD,0, 10% lethal dose; LD«o, 90% lethal dose; PCB, procarbazine; CPA, cyclophospha mide; CDP, c/s-platinum; VCR, vincristine; i.e. ¡ntracerebral(ly). 2352 CANCER RESEARCH VOL. 44 Research. on November 27, 2021. © 1984 American Association for Cancer cancerres.aacrjournals.org Downloaded from