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The tricyclic nucleotide triciribine phosphate (TCN-P) was synthesized as a water-soluble derivative of the tricyclic nucleoside TCN (L. B. Townsend et al, INSERM 81:37, 1978). Growth of L1210 cells in vitro was inhibited equally by TCN and TCN-P. A requirement for adenosine kinase activity for activation of both TCN and TCN-P was established by the observation that growth inhibition by either compound was decreased 200-fold by the adenosine kinase inhibitor 5-iodotubercidin and greater than 5000-fold in L1210/T, an adenosine kinase-deficient subline. The TCN/TCN-P resistance of L1210/T cells was correlated with lack of formation of intracellular TCN-P from either TCN or TCN-P. Thus, it appeared that TCN-P was hydrolyzed to TCN and then rephosphorylated intracellularly. Both the horse serum-containing culture medium and the intact cells possessed nucleotide phosphatase activity, which may contribute to the hydrolysis of TCN-P to TCN in the L1210 cell cultures. The requirement for hydrolysis of TCN-P to TCN for formation of intracellular TCN-P from exogenous TCN-P was also shown directly by the observation that human erythrocytes, which lack ectophosphatases, readily formed intracellular TCN-P from TCN but not from TCN-P when incubated in buffer.

Clinical, pharmacologic, and immunologic effects of 2'-deoxycoformycin (dCF) were evaluated in 15 patients with advanced malignancies. Toxicity was less severe with a low dose (4 mg/m2) of dCF, but this dose still resulted in suppression of cellular adenosine deaminase activity, skin test reactivity, and lymphocyte responses to mitogens. Improvement in cutaneous T cell lymphoma plaques was seen after dCF. Further investigations of antitumor efficacy with the use of this low dosage schedule should continue in patients with hematologic neoplasms, and additional preliminary studies of the combination of an adenosine deaminase inhibitor with an adenosine analog should also be considered.

-Deazaadenosine (9-DAA), a novel purine analog, was found to be a potent inhibitor of the growth of nine different human solid tumor cell lines in vitro and of pancreatic carcinoma (DAN) in antithymocyte serum (ATS)-immunosuppressed mice. In culture, IC50 values ranged from 1.1 to 8.5 X 10(-8)M. Ovarian carcinoma (MR) was the only cell line in which the activity of 9-DAA was potentiated (about 10-fold) by pretreatment with the adenosine deaminase inhibitor 2'-deoxycoformycin (dCF). After incubation of cultured pancreatic DAN cells with 9-DAA (10(-5)M) for 2 hr, a peak appeared in the triphosphate region of HPLC nucleotide profiles that was identified tentatively as 9-deazaATP. Under the same incubation conditions, the incorporation of [3H]uridine into RNA and of [3H]thymidine into DNA was inhibited by 34 and 80% respectively. In vivo studies using ATS-immunosuppressed mice showed that 9-DAA at 0.4 mg/kg/day for 3 consecutive days reduced pancreatic carcinoma (DAN) tumor weights to approximately 50% of untreated controls. The nucleoside transport inhibitor p-nitrobenzyl-6-thioinosine (NBMPR) was shown to selectively protect host tissues from 9-DAA toxicity and, thereby, potentiated the antitumor activity of 9-DAA in vivo at optimal dosages.

The toxicology and metabolism of 8-azaadenosine (8-azaAdo) were examined both as a single agent and in combination with the adenosine deaminase inhibitor, 2'-deoxycoformycin (dCF). The LD10 (mice) for 8-azaAdo alone on a once daily for 5 days (q.d. x 5) schedule was 30 mg . kg-1 . day-1. When the animals were pretreated with 0.1 mg . kg-1 . day-1 of dCF, the LD10 dose was reduced to 10 mg . kg-1 . day-1 x 5. The major organ toxicity seen was hepatic. Bone marrow cellularity was only slightly altered at the LD10 dose. 8-AzaAdo nucleotides were detected in the livers of treated mice as determined by high performance liquid chromatography. Further, after 2 hr of incubation, isolated rat hepatocytes accumulated 8-azaATP to levels of 2.2 mumoles/g of cells with 8-azaAdo (1 mM) alone and to 4.3 mumoles/g of cells when 8-azaAdo was used in combination with dCF (1 microgram/ml). ATP levels decreased to below the limits of detection after 2 hr in cells treated with the combination. The replacement of cellular ATP by 8-azaATP may provide an explanation for the hepatotoxicity observed in the murine toxicology studies.

The physiologic role of cyclic adenosine monophosphate (cAMP) in the growth control of a spectrum of human cancer lines, including leukemic lines, and v-rasH oncogene-transformed NIH/3T3 cells is demonstrated by the use of site-selective cAMP analogs. These cAMP analogs, which can select either of the two known cAMP binding sites of the cAMP receptor protein, induce potent growth inhibition, phenotypic change, and differentiation (leukemic cells) of cancer cells at micromolar concentrations with no sign of cytotoxicity. The growth inhibition parallels selective modulation of cAMP-dependent protein kinase isozymes, type I versus type II, and suppression of cellular proto-oncogene expression. Site-selective cAMP analogs thus provide new biological tools for investigating cell proliferation and differentiation and also for the improved management of human cancers.

This report describes a gas chromatographic procedure using a packed column and a flame ionization detector, which is suitable for the therapeutic monitoring of N-methylformamide (N-MF). N-MF is a polar compound that induces cancer cell maturation in vitro and exhibits antitumor activity with human tumors xenografted in nude mice. Toxicology studies with mice have shown this compound to be hepatotoxic. N-MF is currently undergoing Phase I clinical trial as an anticancer drug at this institution. In concert with its clinical trial, a method for the analysis of N-MF in biological fluids has been developed to study its pharmacokinetics. This method involves direct injection of urine or acetone-deproteinized serum onto a Chromosorb 103 column, using N,N-diethylformamide as an internal standard.

Total and filterable platinum in plasma were monitored for seven courses (five patients, 25 mg/m2/day) using continuous 5-day infusions and one 30-minute infusion at a similar dose level (120 mg/m2). Maximum filterable (non-protein-bound) platinum levels (0.1-0.3 mg/L) for the extended infusions were ten to 40 times lower than that for the short-term infusion (4.0 mg/L). Filterable drug exposure as measured by the area under the [Pt]filterable-time curve is greater for the extended infusions (9.6 mg X hr/L) than that for the short-term infusion (4.8 mg X hr/L). Renal excretion of cisplatin (% of dose excreted/24-hour period after the beginning of the infusion) was measured for four courses of continuous 5-day infusions and for the 30-minute infusion. Urine excretion rates were lower for the continuous infusion (5%-8% of dose/24-hour period during the infusion) compared to the short-term infusion (33% of dose/24-hour period after the beginning of the 30-minute infusion).

6-Methylmercaptopurine riboside (MMPR) and 5-fluorouracil (5-FU) were administered sequentially to 12 patients in a phase I clinical trial. Toxicities included mild nausea and vomiting, as well as reversible leukopenia and thrombocytopenia. Maximal accumulation of 6-methylmercaptopurine ribonucleoside 5'-monophosphate (MMPR-P), the active metabolite of MMPR, in patients' erythrocytes occurred between 2 and 6 h after the administration of MMPR and the degree of accumulation was dose-related. At 96 h after MMPR administration, MMPR-P was still detectable in patients' erythrocytes. Although no clinical responses were documented, a modified dosage schedule of these drugs should be pursued based on the pharmacokinetic data obtained.

2'-Deoxycoformycin (dCF), a tight-binding inhibitor of adenosine deaminase, has recently been entered into clinical trials. Toxicity has included lymphopenia, seizures, coma, conjunctivitis, renal failure, and hemolysis. Mice treated with dCF on a variety of schedules exhibited massive hemolysis. Hemolysis was brief, lasting about 20 hours, and did not recur upon readministration of the drug unless readministration was delayed for at least 6 days after initial exposure, which suggests that a sensitive subpopulation of cells was selectively destroyed. Splenectomy failed to protect the animals from dCF-induced hemolysis. Administration of adenosine or 2'-deoxyadenosine without dCF did not cause hemolysis, and use of these two agents with dCF did not potentiate the observed hemolysis. ATP and dATP levels were measured in erythrocytes, and changes in levels of these nucleotides did not correspond with the development of hemolysis.

The toxicology and pharmacology of formycin both as a single agent and combined with the adenosine deaminase inhibitor 2'-deoxycoformycin (dCF) were examined in outbred Swiss mice heterozygous for the nude gene (nu/+). The LD10 for formycin alone given on a daily x 5 schedule was 21 mg/kg. When the animals were pretreated with 1 mg/kg of dCF 1 hour prior to each dose of formycin, toxicity was approximately doubled, ie, LD10 was reduced to 10 mg/kg. Death was associated with hepatic toxicity in both treatment regimens; suppression of leukocyte counts was mild except at doses greater than the LD10. Formycin nucleotides were detected by high-performance liquid chromatography in the livers of mice treated with formycin either alone or combined with dCF. When isolated rat hepatocytes were incubated for 2 hours with either formycin or dCF plus formycin, analog nucleotides accumulated in the cells. Cellular ATP decreased to below the limits of detection, whereas a large peak corresponding to formycin-5'-triphosphate was present. This replacement of cellular ATP by formycin-5'-triphosphate may help explain the hepatic toxicity observed.

Deficiency of erythrocytic and lymphocytic adenosine deaminase (ADA) occurs in some patients with severe combined immunodeficiency disease (SCID). SCID with ADA deficiency is inherited as an autosomal recessive trait. ADA is markedly reduced or undetectable in affected patients (homozygotes), and approximately one-half normal levels are found in individuals heterozygous for ADA deficiency. The metabolism of purine nucleosides was studied in erythrocytes from normal individuals, four ADA-deficiency patients, and two heterozygous individuals. ADA deficiency in intake erythrocytes was confirmed by a very sensitive ammonia-liberation technique. Erythrocytic ADA activity in three heterozygous individuals (0.07,0.08, and 0.14 mumolar units/ml of packed cells) was between that of the four normal controls (0.20-0.37 mumol/ml) and the ADA-deficient patients (no activity). In vitro, adenosine was incorporated principally into IMP in the heterozygous and normal individuals but into the adenosine nucleotides in the ADa-deficient patients. Coformycin (3-beta-D-ribofuranosyl-6,7,8-trihydroimidazo[4,5-4] [1,3] diazepin-8 (R)-ol), a potent inhibitor of ADA, made possible incorporation of adenosine nucleotides in the ADA-deficient patients...

Adenosine (Ado) and Ado analogues produce multiple hemodynamic effects including coronary vasodilation, bradycardia, alterations in left ventricular contractility, and peripheral vasodilation or vasoconstriction depending on the vascular bed. The intact anesthetized Sprague-Dawley rat was examined in relation to electrocardiogram and blood pressure alterations induced by a series of potentially useful antineoplastic agents that are purine or pyrimidine analogues as part of a preclinical evaluation of these agents. The drugs tested were arabinosyladenine and its 5'-monophosphate derivative arabinosyladenine-5'-monophosphate (ara-AMP), the 2-fluoro derivative of ara-AMP, the pyrazolo[4,3-d]pyrimidines (formycin and formycin B), 8-azaadenosine, 6-methylmercaptopurine riboside, tricyclic nucleoside-5'-monophosphate, 5-fluorouracil, arabinosylcytosine, and 3-deazauridine. Those Ado analogues subject to deamination by adenosine deaminase (ADA) were also studied in the intact Sprague-Dawley rat after pretreatment with the ADA inhibitor 2'-deoxycoformycin. The results indicate that these agents have significant hemodynamic effects and should alert clinicians to potential adverse reactions when infusing these drugs.