Cytokinin activity of ureidopurine derivatives related to a modified nucleoside found in transfer RNA.

By use of a radioactive labeling technique N-(nebularin-6-ylcarbamoyl)threonine has been detected in plant transfer RNA. Derivatives of this nucleoside promote cell division of a cytokinin-requiring soya bean tissue.

Phospholipid derivatives of nucleoside analogs as prodrugs with enhanced catabolic stability.

The nucleoside 5'-diphosphate-L-1,2-dipalmitin derivatives of 1-beta-D-arabinofuranosylcytosine (ara-C), 9-beta-D-arabinofuranosyladenine (ara-A), and tubercidin have been synthesized, and their cytotoxicity has been evaluated against a mouse myeloma cell line (MPC-11) in vitro and against L1210 lymphoid leukemia both in vitro and in vivo. Sonication methods were utilized to solubilize these lipophilic derivatives in aqueous solution in order to facilitate such biological evaluation; the ara-A derivative resisted solubilization by several techniques. The nucleoside:phospholipid conjugates of ara-C and tubercidin both were cytotoxic towards the two cell lines, and detailed experiments were cytotoxic towards the two cell lines, and detailed experiments were carried out to show that the new derivatives (a) were not degraded in the medium prior to cellular uptake and (b) acted as prodrugs or molecular depots of the parent nucleoside analog. In addition, 1-beta-D-arabinofuranosylcytosine 5'-diphosphate'5'-L-1,2-dipalmitin was not a substrate for cytidine deaminase (cytidine aminohydrolase, EC 3.5.4.5), the primary enzyme responsible for the rapid catabolism of ara-C. In in vivo studies against L1210 lymphoid leukemia in mice, the 1-beta-D-arabinofuranosylcytosine 5'-diphosphate-5'-L-1,2-dipalmitin showed an increased efficacy (increased life span, 260%) relative to the parent ara-C (increased life span, 89%) regardless of treatment schedule used, whereas the tubercidin 5'-diphosphate-5'-L-1,2-dipalmitin appeared extremely toxic even at low dosages. That 1-beta-D-arabinofuranosylcytosine 5'-diphosphate-5'-L-1,2-dipalmitin was acting as a sustained release drug in vivo was demonstrated by utilizing a single dose administered on Days -1, 0, +1, and +2 relative to inoculation of the L1210 lymphoid leukemia cells on Day 0. Again, a much increased efficacy relative to the best treatment using ara-C was apparent. The potential advantages and the biochemical rationale for the development of these novel prodrugs are discussed.

Formulation, stability, and antitumor activity of 1-beta-D-arabinofuranosylcytosine conjugate of thioether phospholipid.

1-beta-D-Arabinofuranosylcytosine 5'-diphosphate-rac-1-S-octadecyl-2-O- palmitoyl-1-thioglycerol (ara-CDP-DL-PTBA) is an effective stable 1-beta-D-arabinofuranosylcytosine (ara-C) conjugate of thioether phospholipid against a variety of transplantable tumors in mice. The conjugate was formulated in a micellar solution by sonication, in which the conjugate exists as micellar discs (size, 0.01 to 0.04 micron). Analyses on thin-layer and high-pressure liquid chromatography showed that the conjugate was chemically stable upon storage at 3-4 degrees C for more than a 6-mo period. However, stored at room temperature for 3 mo it began to degrade (3 to 11%) to 1-beta-D-arabinofuranosylcytosine 5'-monophosphate and phosphatidic acid. At 3-4 degrees C, the micellar structure remained generally unchanged for 6 mo (size, less than 0.1 micron). Samples stored for 4 mo at room temperature formed some larger vesicles (size, 0.1 to 0.4 micron). Antitumor activity against i.p. implanted L1210 leukemia in mice remained relatively constant with samples stored for 6 mo at 3-4 degrees C or 3 mo at room temperature. 1-beta-D-Arabinofuranosylcytosine 5'-triphosphate (ara-CTP) levels were elevated (greater than 500 pmol/10(7) cells) in L1210 leukemia cells within 1 h following i.p. administration of 400 mg/kg of ara-CDP-DL-PTBA to mice. More importantly, retention of cellular ara-CTP was prolonged (greater than 24 h) in these tumor cells as compared with ara-C treatments. Administration of ara-CDP-DL-PTBA to mice with colon 26 carcinoma (s.c.) resulted in both significant antitumor activity with an increased life span greater than 100% and decreased tumor size. The conjugate also demonstrated a dose-dependent therapeutic effect in mice with M5076 sarcoma (s.c.) as demonstrated by decreases in tumor size and liver metastases. Overall, ara-CDP-DL-PTBA, a stable lipid conjugate of ara-C in a micellar solution, appears to offer substantial therapeutic benefit to mice with leukemia and solid tumors warranting its further development and clinical investigation.

Influence of 1-beta-D-arabinofuranosylcytosine conjugates of lipids on the growth and metastasis of Lewis lung carcinoma.

Five different lipid conjugates of 1-beta-D-arabinofuranosylcytosine (ara-C) were tested for their therapeutic activity on the growth and metastasis of Lewis lung carcinoma (3-LL). Among 1 ester-linked lipid conjugate (Ara-CDP-L-dipalmitin), 3 1-O-alkyl-lipid conjugates (ara-CDP-D,L-PBA, ara-CDP-D,L-PCA, ara-CDP-D,L-MBA) and a thioether-lipid conjugate (ara-CDP-D,L-PTBA) ara-CDP-D,L-PTBA, ara-CDP-D,L-PBA, and ara-CDP-L-dipalmitin produced the strongest tumor growth inhibition and increase of surviving animals in C57Bl6-mice bearing i.p.-implanted 3-LL. Furthermore these conjugates were superior to the parent compounds alone, or equimolar mixtures of the alkyllysophospholipid derivatives ET-18-OCH3 and ara-C. Successful therapeutic regimen consisted of 80-100 mg conjugate/kg, given i.p. daily for five consecutive days. Similar regimen injected shortly after the surgical removal of the primary tumor as adjuvant chemotherapy inhibited the metastasis of 3-LL to the lungs of the animals as demonstrated by an increase of survival time and the number of surviving animals.

Therapeutic activity of 1-beta-D-arabinofuranosylcytosine conjugates of lipids in WEHI-3B leukemia in mice.

Two new conjugates of 1-beta-D-arabinofuranosylcytosine (ara-C) and lipids were tested for therapeutic activity in myelomonocytic WEHI-3B leukemia in mice. Both conjugates were superior to equimolar mixtures of their respective parent compounds and to ara-C alone. IP treatment was found effective after either IP or IV transplantation of the leukemia. The thioether-linked lipid conjugate ara-CDP-D,L-PTBA showed considerably higher efficacy than the ester-linked lipid conjugate ara-CDP-L-dipalmitin. The optimal therapeutic regimen of ara-CDP-D,L-PTBA consisted of 60 mg/kg given IP qd 1-5 after transplantation of the WEHI-3B leukemia.

A simple model of circadian rhythms based on dimerization and proteolysis of PER and TIM.

Many organisms display rhythms of physiology and behavior that are entrained to the 24-h cycle of light and darkness prevailing on Earth. Under constant conditions of illumination and temperature, these internal biological rhythms persist with a period close to 1 day ("circadian"), but it is usually not exactly 24h. Recent discoveries have uncovered stunning similarities among the molecular circuitries of circadian clocks in mice, fruit flies, and bread molds. A consensus picture is coming into focus around two proteins (called PER and TIM in fruit flies), which dimerize and then inhibit transcription of their own genes. Although this picture seems to confirm a venerable model of circadian rhythms based on time-delayed negative feedback, we suggest that just as crucial to the circadian oscillator is a positive feedback loop based on stabilization of PER upon dimerization. These ideas can be expressed in simple mathematical form (phase plane portraits), and the model accounts naturally for several hallmarks of circadian rhythms, including temperature compensation and the per(L) mutant phenotype. In addition, the model suggests how an endogenous circadian oscillator could have evolved from a more primitive, light-activated switch.

Purinylhydantoins. Facile conversion of the naturally occurring N-(purin-6-ylcarbamoyl)-L-amino acids into 3-pruin-6-ylhydantoins and 3-cyclohexyl-1-(purin-6-ylcarbamoyl)hydantoins.

The naturally occurring N-(purin-6-ylcarbamoyl)-L-threonine (PCT, 1b), N-(purin-6-ylcarbamoyl)glycine (PCG, 1a), and some of their analogs were converted into novel purine derivatives, the purinylhydantoins. The PCT and PCG underwent intramolecular cyclization in the presence of N,N-dicyclohexylcarbodiimide (CDD) to give the 3-purin-6-ylhydantoins (2a-c). The same hydantoins were also obtained when the PCT and PCG were allowed to react through the mixed anhydride formed from cyclohexyl isocyanate or ethyl chloroformate. 1,3-Dicyclohexyl-1-(N-(purin-6-ylcarbamoyl)aminoacyl)ureas 3a and 3c, by-products obtained from the DCC reaction, were rapidly converted in aqueous NaOH to another type of purinylhydantoins, the 3-cyclohexyl-1-(purin-6-ylcarbamoyl)hydantoins 4a and 4b. Compound 4a when heated in base underwent hydrolysis of the hydantoin ring giving biuret N-(cyclohexylcarbamoyl)-N-(purin-6-ylcarbamoyl)glycine (5a) and N-(purin-6-ylcarbamoyl)glycine cyclohexylamide (6a). The characterization of these hydantoins was carried out by uv, nmr, and mass spectrometry. The 3-purin-6-ylhydantoins and 3-cyclohexyl-1-(purin-6-ylcarbamoyl)hydantoins showed growth inhibitory activity in the cultured leukemic cells, while the parent amino acid compounds were inactive.

Nucleoside conjugates as potential antitumor agents. 2. Synthesis and biological activity of 1-(beta-D-arabinofuranosyl)cytosine conjugates of prednisolone and prednisone.

Two of the new anticancer drugs recently synthesized in our laboratory from conjugation of ara-C2 and several corticosteroids linked through a phosphodiester bond include prednisolone- (I) and prednisone-p-ara-C (II). They were demonstrated to be enzymatically hydrolyzed to the corresponding steroid and ara-CMP and the latter was further shown to be hydrolyzed to ara-C by phosphodiesterase I, snake venom, 5'-nucleotidase, and acid phosphatase. However, the conjugates were shown to be resistant to hydrolysis by alkaline phosphatase. The activity of conjugates I and II against L1210 lymphoid leukemia in female mice (C3D2F1/J) was significantly greater than that of ara-C alone or in combination with the steroid. In fact, when the optimum dosage of 75 (mumol/kg)/day x 5 was used, the administration of ara-C alone was followed by an increased life span (ILS) of 45%. This result is similar to that previously reported. With the same equimolar doses of mixtures of ara-C and either prednisolone or prednisone, the ILS values were 40 and 44%, respectively. However, when the conjugates were used, the ILS values were 89 and 100% respectively. These findings seem promising and have provided the bases for continued study of these new compounds.

Nucleoside conjugates. 6. Synthesis and comparison of antitumor activity of 1-beta-D-arabinofuranosylcytosine conjugates of corticosteroids and selected lipophilic alcohols.

Five new P1-(steroid-21-yl)-P2-(1-beta-D-arabinofuranosylcytosin-5'-yl)pyro phosphates (ara-CDP-steroids), five 1-beta-D-arabinofuranosylcytosine 5'-O-(alkyl)phosphates (ara-CMP-alkyl esters), and two P1-(alkyl)-P2-(1-beta-D-arabinofuranosylcytosin-5'-yl)pyrophosphat e (ara-CDP-alkyl esters) have been prepared and evaluated against L1210 lymphoid leukemia in culture and in mice (C3D2F1/J). These include ara-CDP-11-deoxycorticosterone (6a), ara-CDP-cortisone (6c), ara-CDP-corticosterone (6d), ara-CDP-cortexolone (6e), and ara-CDP-prednisone (6g), ara-CMP hexadecyl ester (7a), ara-CMP 1-cyclohexylmethyl ester (7b), ara-CMP 1-adamantylmethyl ester (7c), ara-CMP 2-(1-adamanthyl)ethyl ester (7d), ara-CMP 2-chloroethyl ester (7e), ara-CDP hexadecyl ester (9a), and ara-CDP 1-cyclohexylmethyl ester (9b). The in vitro antitumor results indicated that ara-CDP-steroids were as active as the previously reported ara-CMP-steroids and that ara-CMP and ara-CDP-alkyl esters were less growth inhibiting than ara-CDP-steroids and ara-C. However, the in vivo antitumor results indicated that ara-CDP-steroids were generally less effective than the previous monophosphate derivatives. Among them ara-CDP-corticosterone (6d) and the known ara-CDP-cortisol (6b) showed greater efficacy than ara-C with ILS value of 152% and 209%, respectively, at the optimal dose of 40 and 80 (mg/kg)/day for 9 days, while that of ara-C was 138% at the optimum dose of 9.2 (mg/kg)/day. Generally, ara-CMP alkyl esters (7a-e), given ip to the L1210 leukemic mice, were found to be toxic and ineffective. However, ara-CDP hexadecyl ester (9a) showed marginal activity (ILS, 38%). These preliminary results support the thesis that the ara-C conjugates of this type may require a lipophilic and naturally occurring moiety for improved efficacy.

Nucleoside conjugates. 11. Synthesis and antitumor activity of 1-beta-D-arabinofuranosylcytosine and cytidine conjugates of thioether lipids.

Five 1-beta-D-arabinofuranosylcytosine conjugates and two cytidine conjugates of thioether lipids (1-S-alkylthioglycerols) linked by a pyrophosphate diester bond have been prepared and their antitumor activity against an ara-C2 sensitive (L1210/0) and two ara-C resistant L1210 lymphoid leukemia sublines in mice were evaluated. These prodrugs of ara-C include ara-CDP-rac-1-S-hexadecyl-2-O-palmitoyl-1-thioglycerol (8a), ara-CDP-rac-1-S-octadecyl-2-O-palmitoylthioglycerol (8b), and ara-CDP-rac-1-S-octadecyl-2-O-methyl(or -ethyl, -hexadecyl)thioglycerols (8c-e). The cytidine conjugates include CDP-rac-1-S-octadecyl-2-O-palmitoyl(or -methyl)- 1-thioglycerols (9a and 9b). Sonicated solutions of the conjugates existed in the form of micellar disks (size 0.01-0.04 microns). Single doses (200-400 mg/kg) of 8a and 8b produced significant increase in life span (257-371%) in mice bearing ip implanted L1210/0 leukemia. In contrast, conjugates 8c-e were less effective (ILS 19-75%) and cytidine conjugates (9a and 9b) were ineffective. Even though 8a and 8b were found to be curative in a high percentage of mice bearing ip implanted partially ara-C resistant L1210 subline [L1210/ara-C(I)], they were completely ineffective against deoxycytidine kinase deficient ara-C resistant L1210 subline [L1210/ara-C(II)]. However, the present results, together with the previous, demonstrate that 8a and 8b are promising new prodrugs of ara-C with improved efficacy.

Nucleoside conjugates. 14. Synthesis and antitumor activity of 1-beta-D-arabinofuranosylcytosine conjugates of ether lipids with improved water solubility.

A series of ara-CDP-rac-1-O-alkyl-2-O-acylglycerols (9a-f), analogues of highly active ara-CDP-rac-1-O-hexadecyl-2-O-palmitoylglycerol (1) and Cytoros2 (2), was prepared, and solubility, lipophilicity, and structure-activity relationships of these conjugates were investigated. Conjugates 9a-f containing sn-1 alkyl (< C16) and sn-2 fatty acyl (< C14) and sn-1 alkyl (< C14) and sn-2 fatty acyl (< C16) substituents of the glycerol were water-soluble by shaking, while those with the sn-1 alkyl (> C16) and the sn-2 fatty acyl (> C16) such as conjugate 1 were sparingly soluble. Conjugates 9a-c,e were almost completely solubilized in water by shaking. However, a large portion of conjugates 9d and 9f in water by shaking exist in micelles with mean diameters ranging 7.0-55.2 nm. The partition coefficients (1-octanol/PBS) of the water-soluble conjugates were about 9-18 times greater than that of ara-C. A single dose (300 mg/kg) of conjugates 9d and 9f produced a significant increase in life span (ILS 206 to > 543%) with 17-67% long-term survivors (> 45 days) in mice bearing ip-implanted L1210 lymphoid leukemia. These results were comparable to those of the previous conjugate 1 and Cytoros (2). In contrast, conjugates 9a-c,e at single doses were less effective (ILS 69-178% with no long-term survivors). However, two (qd, 1, 7) or three (qd 1, 5, 9) divided doses of these conjugates were found to be as effective as a single dose of the previous conjugates. The three divided doses (150 mg/kg per day) of conjugates 9d, 9e, and 9f produced a remarkable antitumor activity in L1210 leukemic mice (ILS > 350% with > 50% long-term survivors). Because of the convenient formulation and the significant antitumor activities, the water-soluble conjugates 9d, 9e, and 9f warrant further investigation.

Synthesis and biological activities of some N4-substituted 4-aminopyrazolo(3,4-d)pyrimidines.

Syntheses and biological activities of 26 N4-substituted 4-aminopyrazolo[3,4-d]pyrimidines as analogs of naturally occurring modified nucleic acid bases, N-(purin-6-ylcarbamoyl)-L-threonine and N6-(delta2-isopentenyl)adenine, are described. 4-Aminopyrazolo[3,4-d]pyrimidine was converted into the desired intermediate, ethyl pyrazolo[3,4-d]pyrimidine-4-carbamate (2). 4-Ureidopyrazolo[3,4-d]pyrimidines (6-26) were prepared by displacement of the ethoxy group of the carbamate 2 by amino acids and a variety of amines and by a reaction of 4-aminopyrazolo[3,4-d]pyrimidine (1) with isocyanates. N4-Alkylaminopyrazolo[3,4-d]pyrimidines were generally prepared by displacement of the chlorine from 4-chloropyrazolo[3,4-d]pyrimidine with various amines. Several analogs exhibited moderate to very good growth inhibitory activities against cultured L1210 leukemia and 6410 human leukemic myeloblasts.

Synthesis and antitumor activity of 5'-phosphates and cyclic 3',5'-phosphates derived from biologically active nucleosides.

Syntheses and biological activities of 12 N6-substituted adenosine 5'-phosphates and 15 cyclic 3',5'-phosphates are described. Included among these are the cyclic phosphates of the naturally occurring anticodon adjacent modified nucleosides, N6-(delta2-isopentenyl)adenosine and N-(purin-6-ylcarbamoyl)-L-threonine ribonucleoside. Also reported in this paper are the 5'-phosphates and cyclic phosphates of the cytokinins, N6-benzyladenosine, kinetin ribonucleoside, 3-(chloro-trans-2-buten-2-yl)adenosine,6-o-chlorophenylureidopurine ribonucleoside, and 6-allylureidopurine ribonucleoside. The 5'-nucleotides were prepared by direct phosphorylation of the corresponding ribonucleosides with POCl3 and triethyl phosphate. These compounds were converted to the cyclic 3',5'-phosphates by cyclization of the corresponding 5'-nucleotides with dicyclohexylcarbodiimide. Comparison of the cytotoxicity of the ribonucleosides with their 5'-nucleotides and cyclic 3',5'-nucleotides showed that some of the 5'-phosphates and cyclic phosphates were almost as active as the parent nucleosides. The 5'-nucleotides and the cyclic phosphates were more soluble than the parent nucleosides. The cyclic 3',5'-nucleotides were examined as alternate activators of cAMP-dependent protein kinase from beef heart. While all of the analogs studied showed some activity toward this enzyme, several compounds were more effective than cAMP itself. The analogs were also tested as substrates for cyclic 3',5'-nucleotide phosphodiesterase from beef heart. The N6-alkyl-cAMP analogs were poor substrates for the enzyme, while N6-carbamoyl-cAMP derivatives were inert toward this enzyme. These compounds did not inhibit the phosphodiesterase. Some of the cyclic phosphates exhibited marginal effect in the inhibition of glycogen synthesis in skin slices.

Phospholipid-nucleoside conjugates. 3. Syntheses and preliminary biological evaluation of 1-beta-D-arabinofuranosylcytosine 5'-monophosphate-L-1,2-dipalmitin and selected 1-beta-D-arabinofuranosylcytosine 5-diphosphate-L-1,2-diacylglycerols.

Several new phospholipid-ara-C conjugates have been prepared and tested as prodrugs of the parent ara-C. The new derivative include ara-CMP-L-dipalmitin, ara-CDP-L-distearin, ara-CDP-L dimyristin, ara-CDP-L-diolein, and the radioactively labeled derivative ara-CDP-L-di[1-14C]palmitin. In addition, the unusually stable ara-CMP-L-dipalmitin-N-phosphoryldicyclohexylurea adduct was isolated as a crystalline solid (two diastereomers) in the reaction sequence to prepare ara-CMP-L-dipalmitin. The new prodrugs were solubilized by sonication methods and tested for their antiproliferative activity in vitro against mouse myeloma MPC-11 cells and against L1210 lymphoid leukemia. Such studies demonstrated that the antiproliferative activities of the prodrugs (as determined by ED50) were less that ara-C on a molar basis. In the mouse myeloma cell line some evidence was obtained that the antiproliferative activity was related to the chain length of the fatty acid side chains in the prodrugs. In in vivo studies against L1210 lymphoid leukemia in mice, the prodrugs were shown to be much more effective than ara-C, with the overall efficacy apparently being independent of the length of the fatty acid side chain. Some evidence was obtained in the vivo studies that the ara-CDP-L-dimyristin, which bears the shortest fatty acid side chain, was more toxic at the higher dosages than the longer chain length derivatives.

Nucleoside conjugates as potential antitumor agents. 3. Synthesis and antitumor activity of 1-(beta-D-arabinofuranosyl)cytosine conjugates of corticosteroids.

Six 5'-(steroid-21-phosphoryl)-1-(beta-D-arabinofuranosyl)cytosines have been prepared and evaluated against L1210 lymphoid leukemia in culture and in mice (C3D2F1/J). These include the ara-C conjugates of 11-deoxycorticosterone (5a), corticosterone (5b), cortexolone (5c), fludrocortisone (5d), 6 alpha-methylprednisolone (5e), and dexamethasone (5f). When the optimum dosage of ara-C [38 (mumol/kg)/day X 5] was given to mice bearing L1210, the ILS value found was 89%. A simple mixture of each steroid and ara-C gave ILS values that were on the whole significantly less than that of the parent nucleoside. However, of six conjugates, all but two (5d and 5f) were more active than ara-C at their optimal doses. Both corticosterone- (5b) and cortexolone-p-ara-C (5c) were especially effective at the respective optimal doses of 76.7 and 115 (mumol/kg)/day X 5. These gave ILS values of 200% each. All of the conjugates were demonstrated to be enzymatically hydrolyzed to the corresponding steroid and ara-CMP, and the latter was further shown to be hydrolyzed to ara-C by phosphodiesterase I, 5'-nucleotidase, and acid phosphatase. However, they were shown to be resistant to hydrolysis by alkaline phosphatase.

Nucleoside conjugates. 13. Synthesis and antitumor activity of 1-beta-D-arabinofuranosylcytosine conjugates of thioether lipids with improved water solubility.

A series of ara-CDP-rac-1-S-alkyl-2-O-acyl-1-thioglycerols (3-12), analogues of highly active Cytoros2 (1), was prepared, and solubility, lipophilicity, and structure-activity relationships of these conjugates were investigated. The conjugates with sn-1 alkyl (< C18) and sn-2 fatty acyl (< C14) substituents of the thioglycerol were water-soluble, while those with the sn-1 alkyl (> C14) and the sn-2 fatty acyl (> C16) were sparingly soluble. The latter formed micelles upon sonication. Conjugate 7 containing the sn-1 tetradecyl and the sn-2 palmitoyl (C16) groups formed micelles by both sonication and shaking. The partition coefficients (1-octanol/PBS) of the water-soluble conjugates were about 20 times greater than that of ara-C. The water-insoluble showed a more than 40 times increase. A single dose of the micelle-forming conjugates 7 and 10 produced a significant increase in life span (ILS > 421%) with 50% long-term survivors (> 45 days) in mice bearing ip-implanted L1210 lymphoid leukemia. These results were comparable to those of previous micelle-forming conjugate 1 (Cytoros). In contrast, the water-soluble conjugates at single doses were less effective (ILS 81-386% with 0-33% long-term survivors). However, three divided doses of the water-soluble conjugates were found to be as effective as a single dose of micellar solution of the water-insoluble. The results indicate that conjugate 7 and most of the water-soluble derivatives warrant further investigation.

Nucleoside conjugates. 10. Synthesis and antitumor activity of 1-beta-D-arabinofuranosylcytosine 5'-diphosphate-1,2-dipalmitins.

Three 1-beta-D-arabinofuranosylcytosine 5'-diphosphate-1,2-dipalmitins from L-, D-, and DL-alpha-dipalmitoylphosphatidic acids have been synthesized and their antitumor activity against two ara-C2 resistant L1210 lymphoid leukemia sublines in mice were evaluated. These new prodrugs of ara-C include ara-CDP-L-dipalmitin, ara-CDP-D-dipalmitin, and ara-CDP-DL-dipalmitin. The L and DL isomers produced significant increase in life span (greater than 400%) and four to five long-term survivors (greater than 45 days) out of six animals bearing ip implanted partially ara-C resistant L1210 subline [L1210/ara-C (I)], while the D isomer displayed a marginal activity (ILS 100-121%). In contrast, the L isomer was completely ineffective against deoxycytidine kinase deficient ara-C resistant L1210 subline [L1210/ara-C (II)]. However, the results demonstrate that the L and DL isomers of ara-CDP-dipalmitin are promising new prodrugs of ara-C with improved efficacy.

Nucleoside conjugates. 7. Synthesis and antitumor activity of 1-beta-D-arabinofuranosylcytosine conjugates of ether lipids.

Three new 1-beta-D-arabinofuranosylcytosine conjugates of ether lipids (alkyl glycerols) linked by a pyrophosphate diester bond have been prepared and evaluated against mouse leukemia L1210 and P388. These include ara-CDP-rac-1-O-hexadecyl-2-O-palmitoylglycerol (9a) (ara-CDP = 1-beta-D-arabinofuranosylcytosine 5'-diphosphate), ara-CDP-rac-1-O-octadecyl-2-O-palmitoylglycerol (9b), and ara-CDP-rac-1-O-octadecyl-2-O-methylglycerol (9c). Among them, conjugate 9a produced significant increase in life span (200-293%) in mice bearing ip and ic implanted L1210 lymphoic leukemia at a total dose of 400-500 mg (406-508 mumol/kg). Significant schedule dependence was not observed when the conjugate was given ip once daily on day 1, days 1, 5, and 9, and days 1-5. The new conjugates are water soluble by sonication.

Nucleoside conjugates. 15. Synthesis and biological activity of anti-HIV nucleoside conjugates of ether and thioether phospholipids.

A series of the anti-HIV nucleoside conjugates of either (1-O-alkyl) and thioether (1-S-alkyl) lipids linked by a pyrophosphate diester bond has been synthesized as micelle-forming prodrugs of the nucleosides to improve their therapeutic efficiency. These include AZT 5'-diphosphate-rac-1-S-octadecyl-2-O-palmitoyl-1-thioglycerol (1), 3'-azido-2',3'-dideoxyuridine 5'-diphosphate-rac-1-S-octadecyl-2-O-palmitoyl-1-thioglycerol (2) 2',3'-dideoxycytidine 5'-diphosphate-rac-1-S-octadecyl-2-O-palmitoyl-1-thioglycerol (3), and AZT 5'-diphosphate-rac-1-O-tetradecyl-2-O-palmitoylglycerol (4). The conjugates form micelles by sonication (mean diameters ranging 6.8-55.5 nm). Conjugate 1 protected 80% of HIV-infected CEM cells as low as 0.58 microM and lost the protection at 180 microM due to prevailing cytotoxicity, while the conjugate started to show the cytotoxicity at 100 microM. Pharmacokinetics studies showed a significant increase of half-life values (t1/2) of AZT and AZddU2 (respective t1/2 = 5.69 and 6.5 h) after administration of conjugates 1 and 2, while those after administration of AZT and AZddU were 0.28 and 0.89 h, respectively. The fractions of the prodrugs 1 and 2 converted to the parent compounds AZT and AZddU were 36% and 55%, respectively. The results indicate that AZT and AZddU thioether lipid conjugates 1 and 2 warrant further investigation.

Intraarterial 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and systemic chemotherapy for malignant gliomas: a follow-up study.

Twenty-five adults who harbored malignant gliomas received 72 courses of intraarterial 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) (100 mg/m2) and 67 courses of systemic vincristine (1.0 mg/m2) and procarbazine (100 mg/m2) as induction therapy (BVP) followed by 106 courses of systemic 1-(2-chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (methyl-CCNU) (130 mg/m2), vincristine, and procarbazine as maintenance therapy (MVP). With a 6-week interval between each treatment, the median and range for the number of courses of BVP were 3 and 1 to 4 and those for MVP were 3 and 0 to 14, respectively. Fifteen patients (60%) responded to both BVP and MVP, and 10 (40%) did not. The overall median survival time was 12.7 months (range, 1.8 to 48.5+ months). Two of 3 patients who had recurrent gliomas responded and survived for 37+ to 45+ months. Seven of 10 who had nonirradiated glioblastomas responded and survived for 9 to 22 months. Four who had nonirradiated anaplastic astrocytomas all responded and survived for 38+ to 48.5+ months. Two who also received radiotherapy (1 glioblastoma and 1 primitive neuroectodermal tumor) benefited and survived for 16.9 and 28.5+ months. All who did not respond favorably died within 8 months. During the infusion of BCNU, complications included transient orbital and head pain, periorbital and scleral erythema in all patients, and a focal seizure in 1 (4%). During the 6-month induction periods, leukopenia and thrombocytopenia occurred in 1 (4%), deep vein thrombosis occurred in 9 (36%), pulmonary emboli occurred in 8 (32%), upper respiratory infections occurred in 6 (24%), pneumonia occurred in 9 (36%), and herpes zoster occurred in 1 (4%).(ABSTRACT TRUNCATED AT 250 WORDS)