Synthesis and Biological Properties of Novel Pyridinioalkanoyl Thiolesters (PATE) as Anti-HIV-1 Agents That Target the Viral Nucleocapsid Protein Zinc Fingers

Abstract

Nucleocapsid p7 protein (NCp7) zinc finger domains of the human immunodeficiency virus type 1 (HIV-1) are being developed as antiviral targets due to their key roles in viral replication and their mutationally nonpermissive nature. On the basis of our experience with symmetrical disulfide benzamides (DIBAs; Rice et al. Science 1995, 270, 1194-1197), we synthesized and evaluated variants of these dimers, including sets of 4,4'- and 3,3'-disubstituted diphenyl sulfones and their monomeric benzisothiazolone derivatives (BITA). BITAs generally exhibited diminished antiviral potency when compared to their disulfide precursors. Novel, monomeric structures were created by linking haloalkanoyl groups to the benzamide ring through -NH-C(=O)- (amide) or -S-C(=O)- (thiolester) bridges. Amide-linked compounds generally lacked antiviral activity, while haloalkanoyl thiolesters and non-halogen-bearing analogues frequently exhibited acceptable antiviral potency, thus establishing thiolester benzamides per se as a new anti-HIV chemotype. Pyridinioalkanoyl thiolesters (PATEs) exhibited superior anti-HIV-1 activity with minimal cellular toxicity and appreciable water solubility. PATEs were shown to preferentially target the NCp7 Zn finger when tested against other molecular targets, thus identifying thiolester benzamides, and PATEs in particular, as novel NCp7 Zn finger inhibitors for in vivo studies.

Inactivation of HIV-1 Nucleocapsid Protein P7 by Pyridinioalkanoyl Thioesters

“…In this study, the mechanism of NCp7 inhibition by two novel PATEs, compounds 45 and 47, was probed with fluorescence-based assays and mass spectrometric techniques. Although both compounds were very active in cell and target based assays in inhibiting HIV-1, and preliminary studies indicated that these compounds acted through modification of NCp7 zinc fingers (12), they failed to show any appreciable zinc ejection in vitro from purified, recombinant NCp7 or its synthetic peptides under the standard zinc ejection assay conditions. However, zinc ejection was evident upon "activation" with silver ions.…”

“…However, this compound was unable to initiate crosslinking of NCp7 protein within cell-free virions. In contrast, compound 45 did not inhibit the Gag precursor processing, and its anti-viral activity was ascribed to its ability to produce extensive cross-linking of NCp7 protein in cell-free virions (12).…”

“…Ejection from NCp7 by the Pyridinioalkanoyl Thioesters-Since the PATEs analyzed in this study had a very high absorbance at 280 nm, the commonly used method of monitoring the rate of zinc ejection by following the decrease in tryptophan fluorescence (excitation at 280 nm) was not feasible (12,15). Instead, a method of monitoring zinc ejection directly using NPG was adopted.…”

“…Even though 2,2Ј-dithiobis(benzamide) disulfides represent a new class of highly specific antiretroviral agents, the disulfide bond is susceptible to reduction in vivo, resulting in the loss of antiviral activity. To circumvent this problem, we synthesized novel pyridinioalkanoyl thioester (PATE) derivatives (12). Of various such compounds synthesized, two of them, compounds 45 and 47 ( Fig.…”

Novel fused tetrathiocines as antivirals that target the nucleocapsid zinc finger containing protein of the feline immunodeficiency virus (FIV) as a model of HIV infection

“…1) have shown encouraging results but so far have failed to make the progression to late stage clinical trials. [15][16][17][18][19][20] As a result of the similarity and sequence overlap between the nucleocapsid protein of HIV and FIV, we recently initiated a research program to develop compounds that could target this key protein. We previously described the results of our first class of compounds against this key target with a series of bis [1,2]dithiolo [1,4]thiazines and bis [1,2]dithiolopyrroles that showed promising activity against FIV, but were limited by their chemical tractability.…”