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

Advance of structural modification of nucleosides scaffold

With Remdesivir being approved by FDA as a drug for the treatment of Corona Virus Disease 2019 (COVID-19), nucleoside drugs have once again received widespread attention in the medical community. Herein, we summarized modification of traditional nucleoside framework (sugar + base), traizole nucleosides, nucleoside analogues assembled by other drugs, macromolecule-modified nucleosides, and their bioactivity rules. 2′-“Ara”-substituted by –F or –CN group, and 3′-“ara” substituted by acetylenyl group can greatly influence their anti-tumor activities. Dideoxy dehydrogenation of 2′,3′-sites can enhance antiviral efficiencies. Acyclic nucleosides and L-type nucleosides mainly represented antiviral capabilities. 5-F Substituted uracil analogues exihibit anti-tumor effects, and the substrates substituted by –I, –CF₃, bromovinyl group usually show antiviral activities. The sugar coupled with 1-N of triazolid usually displays anti-tumor efficiencies, while the sugar coupled with 2-N of triazolid mainly represents antiviral activities. The nucleoside analogues assembled by cholesterol, polyethylene glycol, fatty acid and phospholipid would improve their bioavailabilities and bioactivities, or reduce their toxicities.

Comparative Studies on the Susceptibility of (R)-2,3-Dipalmitoyloxypropylphosphonocholine (DPPnC) and Its Phospholipid Analogues to the Hydrolysis or Ethanolysis Catalyzed by Selected Lipases and Phospholipases

Susceptibility of soybean phosphatidylcholine, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and its phosphono analogue (R)-2,3-dipalmitoyloxypropylphosphonocholine (DPPnC) towards selected lipases and phospholipases was compared. The ethanolysis of substrates at sn-1 position was carried out by lipase from Mucor miehei (Lipozyme®) and lipase B from Candida antarctica (Novozym 435) in 95% ethanol at 30 °C, and the hydrolysis with LecitaseTM Ultra was carried out in hexane/water at 50 °C. Hydrolysis at sn-2 position was carried out in isooctane/Tris-HCl/AOT system at 40 °C using phospholipase A2 (PLA2) from porcine pancreas and PLA2 from bovine pancreas or 25 °C using PLA2 from bee venom. Hydrolysis in the polar part of the studied compounds was carried out at 30 °C in acetate buffer/ethyl acetate system using phospholipase D (PLD) from Streptococcus sp. and PLD from white cabbage or in Tris-HCl buffer/methylene chloride system at 35 °C using PLD from Streptomyces chromofuscus. The results showed that the presence of C-P bond between glycerol and phosphoric acid residue in DPPnC increases the rate of enzymatic hydrolysis or ethanolysis of ester bonds at the sn-1 and sn-2 position and decreases the rate of hydrolysis in the polar head of the molecule. The most significant changes in the reaction rates were observed for reaction with PLD from Streptococcus sp. and PLD from Streptomyces chromofuscus that hydrolyzed DPPnC approximately two times slower than DPPC and soybean PC. The lower susceptibility of DPPnC towards enzymatic hydrolysis by phospholipases D gives hope for the possibility of using DPPnC-like phosphonolipids as the carriers of bioactive molecules that, instead of choline, can be bounded with diacylpropylphosphonic acids (DPPnA).

An Overview of Therapeutic Applications

Over the last few years' great advances have been made on the development drug delivery systems for different purposes for targeting the diseased conditions. Novel drug delivery originates from polymers or associated with some devices is generally related with the emergence of novel characteristics. These changes are what eventually comprise the value of drug delivery system and Novel drug delivery system. Novel properties become existed without making new materials. Novel drug delivery system comparable to traditional system, following Targeted Drug Delivery System (TDDS) is also called targeting drug system. A new drug delivery system makes the drugs densely gather pathological-change structures, and has an improved healing effect and less toxic side effects. The drugs can improve the strength of pharmacological action and reduce the bad effect all over the body, for they release in the target organs.

Phospholipid derivatives of cladribine and fludarabine: synthesis and biological properties

Phospholipid derivatives of anticancer nucleosides cladribine and fludarabine (F-ara-A) bearing 1,2- and 1,3-diacylglycerol moieties have been prepared by the H-phosphonate approach using 1,1,3,3-tetraisopropyldisiloxane-1,3-diyl protecting group for cladribine and a combination of tert-butyldimethylsilyl and levulinyl protecting groups for 2-fluoroadenine nucleosides. The synthesized conjugates exhibited lower in vitro antiproliferative activity against human tumor cell lines in comparison with the same concentrations of the parent cladribine and fludarabine phosphate. In the course of biokinetic study, it was found that intragastric administration of phospholipid F-ara-A derivatives to Wistar rats and ICR outbred male mice led to a slow release of F-ara-A into the bloodstream, a smooth increase in nucleoside concentration, and prolonged serum circulation of liberated nucleoside. The oral bioavailability of F-ara-A from 1,2-dimyristoylglycerophosphate derivative 29 was similar to its oral bioavailability from fludarabine phosphate.

Advances in the development of nucleoside and nucleotide analogues for cancer and viral diseases

Nucleoside analogues have been in clinical use for almost 50 years and have become cornerstones of treatment for patients with cancer or viral infections. The approval of several additional drugs over the past decade demonstrates that this family still possesses strong potential. Here, we review new nucleoside analogues and associated compounds that are currently in preclinical or clinical development for the treatment of cancer and viral infections, and that aim to provide increased response rates and reduced side effects. We also highlight the different approaches used in the development of these drugs and the potential of personalized therapy.

Synthesis and in vitro cytostatic activity of 1,2- and 1,3-diacylglycerophosphates of clofarabine

The conjugates of anticancer nucleoside clofarabine [2-chloro-9-(2-deoxy-2-fluoro-β-d-arabinofuranosyl)adenine] with 1,2- and 1,3-diacylglycerophosphates have been prepared by the phosphoramidite method using a combination of 1,1,3,3-tetraisopropyldisiloxane-1,3-diyl protecting group for the sugar moiety of the nucleoside and 2-cyanoethyl protection for the phosphate fragment. Some of the synthesized conjugates exhibited cytostatic activity against HL-60, A-549, MCF-7, and HeLa tumor cell lines.

Advances in the development of nucleoside and nucleotide analogues for cancer and viral diseases

Nucleoside analogues have been in clinical use for almost 50 years and have become cornerstones of treatment for patients with cancer or viral infections. The approval of several additional drugs over the past decade demonstrates that this family still possesses strong potential. Here, we review new nucleoside analogues and associated compounds that are currently in preclinical or clinical development for the treatment of cancer and viral infections, and that aim to provide increased response rates and reduced side effects. We also highlight the different approaches used in the development of these drugs and the potential of personalized therapy.

Synthesis of dehydroepiandrosterone analogues modified with phosphatidic acid moiety

Dehydroepiandrosterone (DHEA) and its metabolite 7α-OH DHEA have many diverse physiological, biological and biochemical effects encompassing various cell types, tissues and organs. In in vitro studies, DHEA analogues have myriad biological actions, but in vivo, especially in oral administration, DHEA produces far more limited clinical effects. One of the possible solutions of this problem is conversion of DHEA to active analogues and/or its transformation into prodrug form. In this article, the studies on the conversion of DHEA and 7α-OH DHEA into their phosphatides by the phosphodiester approach are described. In this esterification, N,N-dicyclohexylcarbodiimide (DCC) was the most efficient coupling agent as well as p-toluenesulphonyl chloride (TsCl).

Nucleoside, nucleotide and oligonucleotide based amphiphiles: a successful marriage of nucleic acids with lipids

Amphiphilic molecules based on nucleosides, nucleotides and oligonucleotides are finding more and more biotechnological applications. This Perspective highlights their synthesis, supramolecular organization as well as their applications in the field of biotechnology.

A novel mechanism for oral controlled release of drugs by continuous degradation of a phospholipid prodrug along the intestine: In-vivo and in-vitro evaluation of an indomethacin–lecithin conjugate

PURPOSE

To investigate a novel mechanism for oral controlled release of drugs involving a continuous degradation of a phospholipid prodrug along the intestine. An indomethacin-lecithin conjugate with the drug attached to the sn-2 position of the phospholipid through a 5-carbon linker (DP-155) was used as a model molecule.

METHODS

The pharmacokinetics of DP-155 and free indomethacin liberated from the prodrug following intravenous, oral or intra-colon administration was investigated in rats, and evaluated in comparison to free indomethacin administration. Degradation by phospholipase A(2) (PLA(2)) enzymes was assessed in-vitro. The impact of the linker length was evaluated in comparison to an indomethacin-phospholipid conjugate with a shorter linker (2-carbons).

RESULTS

Following oral or intra-colon DP-155 administration, free indomethacin was liberated along the intestine and absorbed into the systemic circulation, resulting in a controlled release profile of indomethacin in the plasma. The shorter linker caused a 20-fold decrease in the subsequent indomethacin absorption. DP-155 in-vitro degradation by PLA(2) was over 60%, while shorter linkers were profoundly less degradable.

CONCLUSIONS

DP-155 caused a continuous input of free indomethacin into the plasma following degradation by PLA(2) in the gut lumen. Since the rate of drug release is not formulation dependent, the prodrug can be compounded even in a liquid dosage form. The phospholipid-drug conjugate is thus a potential novel mechanism for oral controlled release of drugs.

Nucleolipids: natural occurrence, synthesis, molecular recognition, and supramolecular assemblies as potential precursors of life and bioorganic materials

Nucleolipids are hybrid molecules composed of a nucleobase, a nucleoside, a nucleotide or an oligonucleotide (either DNA or RNA), and a lipophilic moiety, which might be either simply a single- or double-chained alkyl (or alkenyl) moiety or a carbocyclic hydrocarbon such as cholesterol, a vitamin, or a bile acid. This review covers all aspects of nucleolipids, namely their natural occurrence, their synthesis, their molecular recognition, as well as aggregation behavior, either in aqueous or non-aqueous solution. Potential future aspects of nucleolipids in material sciences and for the elucidation of biochemical reactions in living cells are discussed.

A comparison of enzymatic phosphorylation and phosphatidylation of β-l- and β-d-nucleosides

Enzymatic 5'-monophosphorylation and 5'-phosphatidylation of a number of beta-L- and beta-D-nucleosides was investigated. The first reaction, catalyzed by nucleoside phosphotransferase (NPT) from Erwinia herbicola, consisted of the transfer of the phosphate residue from p-nitrophenylphosphate (p-NPP) to the 5'-hydroxyl group of nucleoside; the second was the phospholipase D (PLD)-catalyzed transphosphatidylation of L-alpha-lecithin with a series of beta-L- and beta-D-nucleosides as the phosphatidyl acceptor resulted in the formation of the respective phospholipid-nucleoside conjugates. Some beta-L-nucleosides displayed similar or even higher substrate activity compared to the beta-D-enantiomers.

A novel phospholipid gemcitabine conjugate is able to bypass three drug-resistance mechanisms

We have previously synthesized a phospholipid-gemcitabine conjugate and a phospholipid-cytosine arabinoside conjugate that we tested in different human cancer cell lines. The gemcitabine conjugate was more cytotoxic to the cancer cells tested than the cytosine arabinoside (ara-C) conjugate. The focus here was to elucidate the mechanism of action of the conjugate molecule and its ability to bypass certain drug-resistance mechanisms. In contrast to gemcitabine, the gemcitabine conjugate did not enter the cell via the human equilibrative nucleoside transporter (hENT1). Additionally, the gemcitabine conjugate was not a substrate for the multidrug resistance efflux pump, MDR-1, even though the molecule is more lipophilic. Finally, we showed that deoxycytidine kinase (dCK) was not required for the activation of the gemcitabine conjugate. As expected, cells overexpressing dCK were more sensitive to gemcitabine whereas cells overexpressing dCK were not more sensitive to the gemcitabine conjugate. Taken together, these results suggest that the gemcitabine conjugate may be therapeutically superior to gemcitabine due to the conjugate's ability to bypass three resistance mechanisms that often render gemcitabine ineffective as an anticancer agent.

Drug-phospholipid conjugates as potential prodrugs: synthesis, characterization, and degradation by pancreatic phospholipase A(2)

The aim of the present study was the synthesis of phospholipids containing a drug molecule instead of a fatty acid. Valproic acid and ibuprofen served as model compounds. The target molecules were synthesized either starting from sn-glycero-3-phosphocholine (1) or using (S)-2-O-benzyl-1-O-tritylglycerol (11) and (R)-2-O-benzyl-1-O-tert-butyldiphenylsilylglycerol (12), respectively, as key intermediates. With respect to the surface properties and the aggregation behavior, the drug-phospholipid conjugates resembled natural phosopholipids. Upon incubation with porcine pancreatic phospholipase A(2), only compounds with a fatty acid in the sn-2 position of the glycerol backbone were degraded. Derivatives with either ibuprofen in the sn-2 position or displaying the unnatural S-configuration were resistant to enzymatic in vitro hydrolysis.

Minireview: nucleotide prodrugs

Nucleotides have shown interesting biological activities in a wide variety of antiviral, antiproliferative, immunomodulatory and other biological assays, and they present promising drug candidates. Because of their negative charge(s) nucleotides suffer from some disadvantages which can be successfully overcome by the utilization of nucleotide prodrugs. Nucleotide prodrugs were successfully used to increase oral absorption of nucleotides in vivo. By taking advantage of intracellular triggers (reducing potential, enzyme activity, pH), nucleotide prodrugs can be used in vitro for the intracellular delivery of the nucleotide resulting in enhanced potency and in some cases enhanced selectivity. Nucleotide prodrugs have also been utilized for tissue specific delivery of the nucleotides in vivo resulting in altered selectivity and reduced toxicity. For nucleotide prodrugs, their ultimate intended use is (in most cases) in vivo for the treatment of a disease. Thus, it is important to incorporate adequate assays and design criteria into any prodrug effort. In vivo systems are complicated because of metabolism, excretion and tissue distribution of the prodrug and the parent. Thus, results of in vitro assays have to be interpreted cautiously because they may be unsuitable predictors of the in vivo situation.

1-beta-D-arabinofuranosylcytosine conjugates of ether and thioether phospholipids. A new class of ara-C prodrug with improved antitumor activity

The 1-beta-D-arabinofuranosylcytosine (ara-C) conjugates 1-O-alkyl (ether) and 1-S-alkyl (thioether) phospholipids, being analogues of ara-CDP-sn-1,2-O-dipalmitoylglycerol (1), showed significant antitumor activity against L1210 and P388 leukemia in vivo. The more active conjugates include the 1-O-alkyl analogues, ara-CDP-rac-1-O-hexadecyl-2-O-palmitoylglycerol (2) and ara-CDP-rac-1-O-octa-decyl-2-O-palmitoylglycerol (3), and the corresponding 1-S-alkyl analogues, ara-CDP-rac-1-S-hexadecyl-2-O-palmitoyl-1-thioglycerol (4) and ara-CDP-rac-1-S-octadecyl-2-O-palmitoyl-1-thioglycerol (5, Cytoros). The conjugates were formulated by sonication, in which the conjugates existed as discs (size 0.01-0.04 microns). Among the conjugates of the three different phospholipids, the 1-S-alkyl analogues 4 and 5 displayed the strongest antitumor activity against L1210 leukemia in mice, followed by the 1-O-alkyl (2 and 3) and the 1-O-acyl (1) analogues. The 1-S-alkyl analogue 5 was considerably more effective than the 1-O-acyl analogue 1 against myelomonocytic WEHI-3B leukemia in mice. Conjugate 5 (Cytoros) showed a significant therapeutic activity in mice with colon 26 carcinoma, M5076 sarcoma, and C-1300 neuroblastoma. Furthermore, this agent inhibited liver metastases of M5076 sarcoma. Conjugates 3 and 5 also inhibited the metastasis of 3-Lewis lung carcinoma to the lungs of mice. Cytoros (5) and its analogues, with other ether and thioether phospholipids, appear to offer increased therapeutic benefit to mice with tumors.

Nucleoside and nucleotide transport through a model liquid membrane. Periodic-catastrophic transport of a novel amantadine phosphoramidate conjugate of 5'-AMP

Adenosine 5'-phosphor(adamantyl)amidate (5), an analog derived by linking the antiviral drug amantadine to 5'-AMP is transported through a model membrane system in a discontinuous periodic-catastrophic fashion. The system was composed of a glass cell containing two aqueous buffer phases separated by a chloroform layer. A more lipophilic, but structurally related derivative, adenosine 5'-phosphor(n-decyl)amidate (3) showed linear transport in the same system. Less lipophilic substances, including 5'-AMP and adenosine 5'-phosphor(morpholidyl)amidate (2), did not show transport. It is hypothesized that the periodic-catastrophic transport is a result of the collective activity of amidate 5 at the interface between the first aqueous interface and the chloroform layer. The time between catastrophic events is thought to be a reflection of the time necessary for molecular organization at the interface. The phenomenon is a new example of molecular organization in a system far from equilibrium leading to a repetitive dynamic process.

Lipid conjugates of antiretroviral agents. I. Azidothymidine-monophosphate-diglyceride: anti-HIV activity, physical properties, and interaction with plasma proteins

3'-Azido-3'-deoxythymidine-5'-phosphate diglyceride (16:0/18:1 omega 9), a phosphatic acid conjugate of AZT, is active against HIV replication in H9 cells and syncytia formation in MOLT-3 cells. The activities rank as AZT greater than pure conjugate greater than conjugate in mixed liposomes, with the pure conjugate having about one-third the activity of free AZT. The compound binds very rapidly to serum lipoproteins, but not to serum albumin, alpha and beta globulins, or red cells. Pancreatic phospholipase A2 hydrolyzes it to the lysophosphatidic acid conjugate.

Synthesis and biological evaluation of some phosphate triester derivatives of the anti-cancer drug araC

A number of novel phosphate triester derivatives of the anti-cancer nucleoside analogue araC have been prepared by a rapid 2-step procedure, not necessitating prior sugar protection. Spectroscopic and lipophilicity data have been collected on these compounds. An in vitro assay indicated inhibition of thymidine incorporation by mammalian epithelial cells, by each of these compounds, in the range 3-300 microM. Moreover, the degree of inhibition showed a close correlation to chemical structure; in particular, there was a clear relationship between inhibition of thymidine incorporation and log(P). These results are consistent with cellular penetration by the intact phosphate triesters and intracellular action by an unspecified mechanism. Triethyl phosphate is inactive under the conditions of the test.

1-beta-D-arabinofuranosylcytosine conjugates of thioether phospholipids as a new class of potential antitumor drugs

Three 1-beta-D-arabinofuranosylcytosine (ara-C) conjugates of 1-S-alkyl-phospholipids (thioether phospholipids) were tested for their antitumor efficacies against L1210 and P388 leukemia in mice. These include 1-beta-D-arabinofuranosylcytosine 5'-diphosphate-rac-1-S-hexadecyl-2-0-palmitoyl-1-thioglycerol (ara-CDP-beta-palmitoyl-DL-thiochimyl alcohol, I), ara-CDP-rac-1-S-octadecyl-2-0-palmitoyl-1-thioglycerol (ara-CDP-beta-palmitoyl-DL-thiobatyl alcohol, II), and ara-CDP-rac-1-S-octadecyl-2-0-hexadecyl-1-thioglycerol (ara-CDP-beta-cetyl-DL-thiobatyl alcohol, III). Conjugates I and II produced significant increase in life span (293-379%) and longterm survivors among mice bearing i.p. implanted L1210 lymphoid leukemia at a total dose of 400 mg (389-400 mumol)/kg. Conjugate II also displayed a strong antitumor activity against i.c. implanted L1210 leukemia in mice with an ILS range of 160-200% at a total dose of 300-450 mg (292-438 mumol/kg. Significant schedule dependency was not observed when the conjugates were administered i.p. once daily with following schedules: qd l; 1,5, 9; 1-5; and 1-9, but single doses typically produced the best effects. The i.p. administration of conjugate II gave the best results on survival of i.p. inoculated L1210 leukemic mice, then followed by the s.c. and i.m. treatments. The i.v. treatment produced a lower activity than the others. Conjugate II also exhibited a strong antitumor activity against i.p. implanted P388 leukemia in mice with ILS values of greater than 255-greater than 329% with 3-5 45-day survivors at a total dose of 300-500 mg (292-486 mumol)/kg (qd 1 or 1-5). The new conjugates I and II displayed a comparable or somewhat higher activity than the previous diacyl and 1-0-alkyl analogs.

The treatment of intravenously implanted Lewis lung carcinoma with two sustained release forms of 1-β-d-arabinofuranosylcytosine

Liposomes have been used in recent years as carriers for drugs and molecules of biological importance. In cancer chemotherapy, however, the advantages of liposome encapsulation of antitumor drugs remain uncertain, with the possible exception of the usefulness of encapsulated 1-beta-D-arabinofuranosyl-cytosine (ara-C), an antitumor drug of a very short half-life. Liposome-encapsulated ara-C has been shown by others to enhance significantly the survival time of mice bearing leukemia, and the enhancement may be attributable to the role of liposomes as a slow release system for ara-C. We now further explore the advantages of two sustained release systems for ara-C, namely the liposome-encapsulated ara-C and 1-beta-D-arabinofuranosylcytosine-5'-diphosphate-L-1,2-dipalmitin (ara-CDP-L-dipalmitin, a prodrug of ara-C). Intravenously implanted Lewis lung carcinoma is used as a solid tumor model. The therapeutic effectiveness of the two slow release forms of ara-C given by either i.v. or i.p. injections is examined. Viable tumor cells (1.0 X 10(5) cells/mouse) were inoculated i.v. and treatment was initiated 24 hr later using three schedules of multiple treatments for liposomal ara-C and single or multiple injections of ara-CDP-L-dipalmitin. Liposomal ara-C given by the i.p. route consistently increased the number of cures (greater than 120 days survival). For example, when nine small doses (10 mg/kg) were given on consecutive days by i.p. injections, 50% of mice given liposomal ara-C were cured, compared with 10% cures in the group given ara-C liposomes by i.v. and no cures in mice receiving free ara-C given according to the same schedules. On the other hand, ara-CDP-L-dipalmitin given at a single dose is more effective than an equal dose divided in five injections. However, no cures have been obtained by treatments with ara-CDP-L-dipalmitin. These results have further demonstrated the advantage of liposomes as carriers for antitumor drugs of short half-life.

1-β-D-Arabinofuranosylcytosine-Phospholipid Conjugates As Prodrugs of Ara-C

The L-, D-, and D,L-isomers of 1-beta-D-arabinofuranosylcytosine 5'-diphosphate-1,2-dipalmitin, new prodrugs of ara-C5, have been evaluated for antitumor activity in L1210 lymphoid leukemic mice. The L-isomer produced significant increase in life span (ILS), and longterm survivors among mice bearing i.p. and i.c. implanted L1210 leukemia and the maximal ILS values found were greater than 543 and greater than 374% with five and four 45-day survivors out of six mice, respectively, at the optimal single doses of 300 mg/kg and 125 mg/kg. The D- and D,L-isomers also displayed significant in vivo antitumor activity against both i.p. and i.c. implanted L1210 leukemia in mice with ILS range of 144-293% at a total dose of 125-250 mg/kg. Significant schedule dependency was not observed when the conjugates were administered i.p. once daily for 5 days, once every 4 days, or as a single dose, but single doses typically produced the best effects. The L-isomer was found to be a more effective prodrug of ara-C than its isomers and other lipophilic prodrugs, 5'-O-palmitoyl-ara-C and N4-acyl-ara-C. Unlike the latter prodrugs, the new conjugates are water soluble by sonication method.

Phospholipid-nucleoside conjugates. 5. The interaction of selected 1-beta-D-arabinofuranosylcytosine-5'-diphosphate-L-1,2-diacylglycerols with serum lipoproteins

The phospholipid-nucleoside conjugates 1-beta-D-arabinofuranosylcytosine-5'-diphosphate-L-1,2-dipalmitin (1), -distearin (2), and -diolein (3) have been shown to interact rapidly with canine high density lipoprotein and with both high density and low density lipoproteins isolated from human serum. The extent of interaction with the high density lipoproteins appears to be dependent upon the characteristic gel-liquid crystalline phase transition of the conjugate's phospholipid. Since the phospholipid-nucleoside conjugates under study represent sustained release forms of the antileukemic agent 1-beta-D-arabinofuranosylcytosine, the therapeutic efficacy of these conjugates should now be considered in light of these interactions.