Synthesis and anti-HIV evaluation of new 2',3'-dideoxy-3'-thiacytidine prodrugs.

A series of anti-HIV prodrugs possessing various polyaminated side arms have been developed. The incorporation of a N-Boc protected monoamine or diamine side arm into the backbone of the 2',3'-dideoxy-3'-thiacytidine 1 (BCH-189) provided an increase in antiviral potency, which could be several orders magnitude greater than the parent drug (1) depending on the cell culture systems used (MT-4 or MDMs). Twenty six 2',3'-dideoxy-3'-thiacytidine prodrugs which differ from each other by the length, the nature of the 5'-O function and the 5'-O or/and N-4 position on the nucleoside moiety were synthesized. Among this new series of prodrugs, several congeners (12c and 12a) were found to inhibit HIV-1 replication in cell culture with 50% effective concentrations EC50 of 10 and 50 nM respectively, in MT-4 cells. Compound 12c was found more active on infected MDMs cells with 50% effective concentration of 0.01 nM. The synthesis and the antiviral properties of these compounds are discussed.

Synthesis and biological evaluation of polyaminated 2',3'-dideoxy-3'-thiacytidine prodrugs.

The syntheses and biological evaluation of polyaminated 2',3'-dideoxy-3'-thiacytidine have been performed. A new lead was found to increase the in vitro antiviral potency (syncitia formation on MT-4 cell line) of two order magnitude greater than the parent nucleoside drug. Moreover, the in vitro activity on HIV macrophages was found to be more than 3 log greater than the activity of the parent drug 1.

Tri-N-Boc-tetraazamacrocycle-nucleoside conjugates: synthesis and anti-HIV activities.

As far as linear N-Boc-polyamines conjugates elicited remarkable anti-HIV activity, the synthesis and anti-HIV properties of cyclic N-Boc-polyamines conjugates such as tetraazamacrocycle-nucleoside were studied. These new conjugates include an ester linkage between the two moieties. They were synthesized using Benzotriazol-1-yloxy-tris(dimethylamino)phosphonium hexafluorophosphate coupling reagent, in the case of N-alkyl polyazamacrocycle derivatives, or through direct condensation of the acyl chloride derivative with nucleoside in the case of N-acyl polyazamacrocycle compounds. None of the new conjugates presented anti-HIV activity greater than that of the corresponding parent nucleosides.

Design, synthesis and structure relationships of new N,N',N",N"'-tetrakis (omega-amino alkyl) tetraazamacrocycles.

A number of N,N',N",N"'-tetrakis (omega-aminoalkyl) tetraazamacrocycles and related compounds were synthesized and evaluated for their inhibitory effects on human immunodeficiency virus type 1 (HIV-1) and duck hepatitis B virus (DHBV) replication. The activity of these compounds was found to be highly dependent upon structural features: (i) the length of the alkyl linker connecting the nitrogen atoms of the macrocyclic ring to the exocyclic nitrogen atoms of the terminal amino groups (five methylenes favoured antiviral activity); (ii) substitution of the terminal amino groups of the linker reduced antiviral activity; and (iii) the size of the tetraazamacrocyclic ring (14 or 15 atoms) did not markedly affect the antiviral activity. Some analogues were potent inhibitors of HIV-1 replication, with anti-HIV activity similar to that of biscyclam (JM 2763). In contrast, other analogues were found to be highly toxic in duck hepatocyte primary culture, the 2.2.15 cell line and to a lesser extent in MT-4 cells. Structural parameters, macrocyclic ring size and metal-chelating ability have been used to develop a structure-activity relationship model in order to aid the design of antiviral molecules derived from N,N',N",N"'-tetrakis (omega-aminoalkyl) tetraazamacrocycles.

Syntheses of new modified Phe-Pro peptides. Use of proline replacements in potential HIV inhibitors.

The syntheses consisting of replacement of proline amino acid by a 3-pyrrolidinone ring in Phe-Pro analogues are described. Preliminary anti-HIV studies demonstrated the potential activity of this new class of compounds.

Selective inhibition of the duck hepatitis B virus by a new class of tetraazamacrocycles.

The antiviral activity of a new class of N,N,N',N",NA'''-pentakis (omega-aminoalkyl) tetraazamacrocycles was evaluated in primary duck hepatocyte cultures infected with the duck hepatitis B virus (DHBV). Three of the four tested compounds were able to selectively inhibit DHBV replication by acting at an early step of the hepadnavirus infection but were associated with significant toxicity.

Synthesis and antiviral activity of new carbonylphosphonate 2',3'-dideoxy-3'-thiacytidine conjugates.

The synthesis of new potential PFA-BCH-189 conjugate analogues is described and their molecular structure clearly identified through NMR and mass spectra techniques. The anti-HIV-1 activity was determined according to the inhibition of syncytium formation in MT-4 cells, while the anti-HBV activity was determined in infected duck hepatocytes. Both antiviral activities of the PFA-BCH-189 conjugates were much lower than those of the parent BCH-189 (2',3'-dideoxy-3'-thiacytidine) (1). Whereas a prodrug effect, following cleavage and release of the free BCH-189 and PFA, cannot be ruled out, poor cellular permeation of the drug seems to be the most likely reason for the reduced activities against HIV and DHBV. The presence of the PFA moiety appears to be detrimental for both the anti-HIV and anti-DHBV activity of PFA-BCH-189 cases.

Inhibition of human immunodeficiency virus type 1 replication by phosphonoformate- and phosphonoacetate-2',3'-dideoxy-3'-thiacytidine conjugates.

The synthesis of potential "combined prodrugs" where phosphonoformic acid (PFA) or phosphonoacetic acid (PAA) was attached to the 5'-O or N4 position of 2',3'-dideoxy-3'-thiacytidine (BCH-189) is described. The anti-HIV-1 activity of 11 analogues which included carboxylic ester or phosphoric ester linkages of PFA or PAA to BCH-189 was determined in MT-4 cells. Of these compounds, the IC50 of analogues 3, 4, 6, and 7 ranged from 0.2 to 100 microM, while IC50 for BCH-189 in this system was 0.1 microM. In vitro hydrolysis of the various esters or amides in human plasma indicated that these agents were relatively stable in the presence of plasma esterases with t1/2 values of up to 120 min. Moreover, lipophilicity of these compounds (partition coefficient) was determined in order to establish correlation between lipophilicity and diffusion of BCH-189 analogues into the cells. The active compounds may exert their effects by extracellular or intracellular hydrolysis to the corresponding antiviral agent BCH-189, but intrinsic anti-HIV-1 activity of some of PAA and PFA adducts, themselves, may also be involved.

Tetrazole isosteres of biologically active acids and their effects on enzymes.

A number of tetrazole analogs of carboxylic substrates and inhibitors have been tested. Lactic and pyruvic tetrazoles were found to be competitive inhibitors of rabbit muscle L-lactate dehydrogenase in both the pyruvate reduction and the lactate oxidation reactions (Ki's of 0.04 M and 0.08 M D,L-lactic tetrazole and 0.02 M and 0.035 M pyruvic tetrazole, respectively). Lactic tetrazole is a non-competitive inhibitor of yeast L-lactate dehydrogenase (Ki = 0.10 M D,L-lactic tetrazole) while pyruvic tetrazole is predominantly competitive (Ki = 0.15 M). Alanine tetrazole is a poorer substrate than alanine for D-amino acid oxidase. It also acts as weak inhibitor. Benzoic tetrazole is a substrate-competitive inhibitor of D-amino acid oxidase (Ki = 0.7 mM) and is also a stronger ethanol-competitive inhibitor than benzoic acid (Ki = 0.03 M) of liver alcohol dehydrogenase. In all the substrates and inhibitors tested, substitution of a tetrazole ring for a carboxylic group has resulted in decreased binding, presumably due to a dilution of the negative charge density and the larger size of the tetrazoyl anion.

Structural requirements for unsaturated fatty acids and fatty alcohols to induce optimal biological responses: an approach using model membranes.

The permeation induced by unsaturated fatty acids and fatty alcohols through the membrane of dihexadecyl phosphate vesicles was quantified, using [Ru(bpy)3(2+)] ions as a permeant probe. In both the free fatty acid and the free fatty alcohol series, the permeation induced by the unsaturated isomers is higher than that of the corresponding saturated analogues. Moreover the permeant effect associated with free fatty acids or free fatty alcohols is under the control of structural and conformational parameters: carbon chain length, number and position of the double bonds, and the geometry Z or E of the double bond. Optimal membrane perturbing effects are observed for compounds having a carbon chain length ranging from 18 to 20 carbon atoms, incorporating two or four Z double bonds in the center of the carbon chain. Good correlation has been found between the membrane perturbing effect quantified as PD50 values and some of the biological properties associated with these fatty lipids. The PD50 values obtained for free fatty alcohols are in fair agreement with anesthetic properties reported by different authors, (Pringle et al., 1981) while PD50 values obtained for free fatty acids show a good correlation with their activity on the superoxide respiratory burst induced by chemotactic peptides. These preliminary results led to the conclusion that as far as a biological activity directly associated with unsaturated fatty acids or alcohols, involved a membrane barrier passage, the measure of their permeant properties using a DHP vesicle model appears to be an excellent criterion for the quantification of optimal biological effects.

Passive permeability of dihexadecylphosphate vesicles altered by aliphatic alcohols and omega-diols.

Alcohols act as anaesthetics only up to a certain chain length, beyond which their biological activity disappears. Although the molecular nature of general target sites remains unknown, presently available data support the hypothesis that this 'cut-off' in anaesthetic activity could be due to a corresponding cut-off in the absorption of long-chain alcohols into lipid-bilayer portions of nerve membranes. To test this hypothesis, we developed a method based on leakage of Ru(bpy)3(2+) ions across the membrane of dihexadecylphosphate (DHP) vesicles induced by aliphatic alcohols (C1 to C18) and some of their omega-diol. The permeant effects of aliphatic linear alcohols expressed as PD50 values rise to a maximum for n-dodecanol (PD50 = 2 x 10(-3) M 1(-1]. Dodecanol was found to be the alcohol which presents the greatest anaesthetic potency among the series of linear aliphatic alcohols (cut-off anaesthetic effect). The results are discussed in terms of the structural physicochemical and geometrical characteristics of the permeating alcohols.