Discovery of GS-9131: Design, synthesis and optimization of amidate prodrugs of the novel nucleoside phosphonate HIV reverse transcriptase (RT) inhibitor GS-9148.

GS-9148 [(5-(6-amino-purin-9-yl)-4-fluoro-2,5-dihydro-furan-2-yloxymethyl)phosphonic acid] 4 is a novel nucleoside phosphonate HIV-1 reverse transcriptase (RT) inhibitor with a unique resistance profile toward N(t)RTI resistance mutations. To effectively deliver 4 and its active phosphorylated metabolite 15 into target cells, a series of amidate prodrugs were designed as substrates of cathepsin A, an intracellular lysosomal carboxypeptidase highly expressed in peripheral blood mononuclear cells (PBMCs). The ethylalaninyl phosphonamidate prodrug 5 (GS-9131) demonstrated favorable cathepsin A substrate properties, in addition to favorable in vitro intestinal and hepatic stabilities.

Design, synthesis, and anti-HIV activity of 4'-modified carbocyclic nucleoside phosphonate reverse transcriptase inhibitors.

A diphosphate of a novel cyclopentyl based nucleoside phosphonate with potent inhibition of HIV reverse transcriptase (RT) (20, IC(50)=0.13 microM) has been discovered. In cell culture the parent phosphonate diacid 9 demonstrated antiviral activity EC(50)=16 microM, within two-fold of GS-9148, a prodrug of which is currently under clinical investigation, and within 5-fold of tenofovir (PMPA).

Synthesis and anti-HIV activity of 2'-fluorine modified nucleoside phosphonates: analogs of GS-9148.

Modified purine analogs of GS-9148 [5-(6-amino-purin-9-yl)-4-fluoro-2,5-dihydro-furan-2-yloxymethyl]-phosphonic acid (2'-Fd4AP) were synthesized and their anti-HIV potency evaluated. The antiviral activity of guanosine analog (2'-Fd4GP) was comparable that of to 2'-Fd4AP in MT-2 cells, but selectivity was reduced.

Synthesis, anti-HIV activity, and resistance profiles of ribose modified nucleoside phosphonates.

A series of nucleoside phosphonate reverse transcriptase (RT) inhibitors have been synthesized and their anti-HIV activity and resistance profiles evaluated. The most potent analog [5-(6-amino-purin-9-yl)-2,5-dihydro-furan-2-yloxymethyl]-phosphonic acid (d4AP) demonstrated a HIV EC(50)=2.1 microM, and the most favorable resistance profile against HIV-1 variants with K65R, M184V or multiple thymidine analog mutations in RT.

Chalcomycin biosynthesis gene cluster from Streptomyces bikiniensis: novel features of an unusual ketolide produced through expression of the chm polyketide synthase in Streptomyces fradiae.

Chalcomycin, a 16-membered macrolide antibiotic made by the bacterium Streptomyces bikiniensis, contains a 2,3-trans double bond and the neutral sugar D-chalcose in place of the amino sugar mycaminose found in most other 16-membered macrolides. Degenerate polyketide synthase (PKS)-specific primers were used to amplify DNA fragments from S. bikiniensis with very high identity to a unique ketosynthase domain of the tylosin PKS.

Production of hybrid 16-membered macrolides by expressing combinations of polyketide synthase genes in engineered Streptomyces fradiae hosts.

Combinations of the five polyketide synthase (PKS) genes for biosynthesis of tylosin in Streptomyces fradiae (tylG), spiramycin in Streptomyces ambofaciens (srmG), or chalcomycin in Streptomyces bikiniensis (chmG) were expressed in engineered hosts derived from a tylosin-producing strain of S. fradiae. Surprisingly efficient synthesis of compounds predicted from the expressed hybrid PKS was obtained.