Bruce S. Burnham

Hypolipidemic activity of boronated nucleosides and nucleotides in rodents

Base-boronated nucleoside and phosphate-boronated nucleotides were potent hypolipidemic agents in rodents, lowering both serum cholesterol and triglyceride levels. Rat VLDL and LDL cholesterol levels were generally reduced and HDL cholesterol levels were significantly elevated after 14 days dosing at 8 mg/kg/day. Tissue cholesterol, triglyceride and phospholipid levels were reduced by selected derivatives. Increased fecal excretion of lipids did not appear to be a mechanism by which these derivatives lowered serum lipids in rodents. Rather, the agents suppressed appetite and reduced the activities of rate-limiting enzymes for de novo lipid synthesis, specifically cytoplasmic acetyl CoA synthetase, squalene synthetase, and phosphatidylate phosphohydrolase with IC50 values of approximately 10(-5) m.

Boronated pyrimidines and purines as cytotoxic, hypolipidemic and anti-inflammatory agents.

The simple boronated bases, e.g. cytosine, adenine and guanine, containing no sugar residues retained good pharmacological activity as hypolipidemic, anti-neoplastic and anti-inflammatory agents in mice at 8 mg/kg. Their activities were generally identical to their respective nucleoside derivatives. Interestingly the boronated acyclovir derivative was a very potent hypolipidemic agent achieving better activity than clofibrate and lovastatin. The boronated adenine derivatives appeared to have the best anti-inflammatory activity in reducing local edema and analgesic effects. The agents were active against the growth of murine and human leukemias and human HeLa-S3 suspended uterine carcinoma. Only the boronated adenine derivatives were effective in blocking the growth of human SW480 adenocarcinoma and the KB nasopharynx.

Synthesis of Trimethylamine-[14C]carboxyborane and Trimethylamine-[14C]carboxymethoxyborane and L1210 Leukemia Cell Uptake

The anti-neoplastic agents trimethylamine-carboxyborane and its corresponding methyl ester have successfully been radiolabeled with carbon-14 in the carboxyl group. Using the radiolabeled agents we have shown that their L1210 leukemia cell uptake appeared to be by a passive process and binding of the agents to DNA, RNA and protein over 24 h was minimal.

Synthesis and cytotoxicity of cyanoborane adducts of n6-benzoyladenine and 6-triphenylphosphonylpurine.

N 6 -Benzoyladenine-cyanoborane (2), and 6-triphenylphosphonylpurine-cyanoborane (3) were selected for investigation of cytotoxicity in murine and human tumor cell lines, effects on human HL-60 leukemic metabolism and DNA strand scission to determine the feasibility of these compounds as clinical antineoplastic agents. Compounds 2 and 3 both showed effective cytotoxicity based on ED50 values less than 4 μg/ml for L1210, P388, HL-60, Tmolt3, HUT-78, HeLa-S3 uterine, ileum HCT-8, and liver Hepe-2. Compound 2 had activity against ovary 1-A9, while compound 3 was only active against prostate PL and glioma UM. Neither compound was active against the growth of lung 549, breast MCF-7, osteosarcoma HSO, melanoma SK2, KB nasopharynx, and THP-1 acute monocytic leukemia. In mode of action studies in human leukemia HL-60 cells, both compounds demonstrated inhibition of DNA and protein syntheses after 60 min at 100 μM. These compounds inhibited RNA synthesis to a lesser extent. The utilization of the DNA template was suppressed by the compounds as determined by inhibition of the activities of DNA polymerase α, m-RNA polymerase, r-RNA polymerase and t-RNA polymerase, which would cause adequate inhibition of the synthesis of both DNA and RNA. Both compounds markedly inhibited dihydrofolate reductase activity, especially in compound 2. The compounds appeared to have caused cross-linking of the DNA strands after 24 hr at 100 μM in HL-60 cells, which was consistent with the observed increased in ct-DNA viscosity after 24 hr at 100 μM. The compounds had no inhibitory effects on DNA topoisomerase I and II activities or DNA-protein linked breaks. Neither compound interacted with the DNA molecule itself through alkylation of the nucleotide bases nor caused DNA interculation between base pairs. Overall, these antineoplastic agents caused reduction of DNA and protein replication, which would lead to killing of cancer cells.

Disposition and Distribution of the Cytidine Cyanoborane Adduct, [2-14C]-2′-Deoxycytidine-3N-Cyanoborane, in CF1 Mice

Summary2′-Deoxycytidine-3N-cyanoborane (dC-BH2CN) had been found to possess cytotoxic, hypo-lipidaemic, and anti-inflammatory activity; its disposition in mice was investigated in this report. The half-life of dC-BH2CN was found to be 0.3 hours and 2′-deoxycytidine was identified as one metabolite. A second elimination rate-limited metabolite was also formed, but was not identified. dC-BH2CN was taken up in vitro in human BG-9 fibroblasts, rat red blood cells, and murine Tmolt3 cells, and in vivo in Ehrlich ascites carcinoma cells. In the Ehrlich ascites tumour, concentrations of dC-BH2CN were 4- to 8-fold higher than liver and plasma from 2 to 24 hours after administration.

The hypolipidemic activity of boronated nucleosides in male mice and rats.

The boronated nucleosides with varying bases and sugar moieties were shown to be potent hypolipidemic agents in rodents. The 3′– aminocynaoborane dideoxythymidine derivative caused reductions in serum cholesterol and triglyceride levels, tissue lipids, VLDL and LDL cholesterol levels while elevating HDL cholesterol levels in rodents. The agents suppressed rat hepatic acetyl CoA synthetase, HMG-CoA reductase, acyl-CoA cholesterol acyl transferase, phosphatidylate phosphohydrolase and lipoprotein lipase activities while elevating cholesterol-7α-hydroxylase activity from 25 to 100 μM.

Hypolipidemic activity of amine-borane aducts of cyclohexylamine and toluidine in rodents.

The amine-borane adducts of cyclohexylamine and toluidine were observed to be potent hypolipidemic agents in mice, I.P. and rats orally at 8 mg/kg/day lowering both serum cholesterol and triglyceride levels after 14-16 days. These compounds were able to lower tissue lipids including the cholesterol content of the aorta wall. The agents successfully lower VLDL- and LDL-cholesterol content while elevating HDL-cholesterol content significantly. The agents also modulate lipid regulatory enzyme activities in a manner to reduce liver lipid levels. These studies demonstrate that the nitrogen atom does not have to be apart of the aromatic ring as in heterocyclic-amine borane to afford good hypolipidemic activity in rodents.

An investigation of 2'-deoxyribonucleoside cyanoboranes in mice for therapeutic safety.

A standard acute toxicity study was undertaken to assess 2′-deoxyribonucleoside cyanoboranes for therapeutic safety. 2′-Deoxyribonucleoside cyanoboranes and related derivatives were nontoxic at doses required for anti-neoplastic and hypolipidemic activities. At higher doses (50 and 100 mg/kg/day IP for 7 days), all treated animals survived with slight reductions in total body weight and small decrements in daily food consumption. No clinical chemistry value was elevated to a magnitude suggesting onset of organ specific toxicity. However, agents appeared to modulate subpopulations of white blood cells, i.e., more lymphocytes than PMNs were present in blood from treated animals as determined by differential cell counts. This modulation is correlated with increases in granulomatous foci in the spleen and mesentery of treated animals after 7 days. The kidney was damaged only by Compound 5 at 50 and 100 mg/kg/day; Compound 5 had the most potent anti-neoplastic activity. The compounds demonstrated no in vitro toxicity against human HCT-8 ileum cells. LD50 values were greater than 1000 mg/kg, IP, for all compounds.

Disposition of the Pharmacologically Active Compound [1-14C-Acetyl]-1-Acetyl-4-Phenyl-1,2,4-Triazolidine-3,5-Dione in CF1 Mice

Summary1-Acetyl-4-phenyl-1,2,4-triazolidine-3,5-dione (APTD) has hypolipidaemic, anti-inflammatory, analgesic, antineoplastic, and aldose reductase inhibitory activities in animals. Disposition studies using pooled plasma and urine samples showed that [1-14C-acetyl]-1-acetyl-4-phenyl-1,2,4-triazolidine-3,5-dione (14C-APTD) had a maximum half-life of 20 hours. Urinary excretion accounted for less than 3% of the radioactivity elimination, while faecal excretion may account for up to 45% of the total elimination. In a 96-hour tissue distribution study, there was no sequestering of 14C-APTD in any of the organs. 14C-APTD demonstrated significant aqueous partitioning, and almost no binding to bovine serum albumin. In L1210 tumour cells, 14C-APTD was bound to DNA and RNA, and there was no binding to intracellular protein. 14C-APTD underwent significant metabolism in mice. One metabolite excreted in urine was identified; two other possible metabolites were proposed.