Synthesis and Biological Properties of Amino Acid Amide Ligand-Based Pyridinioalkanoyl Thioesters as Anti-HIV Agents Yongsheng Song, a,y Atul Goel, b,y Venkatesha Basrur, b Paula E.A. Roberts, c JudyA.Mikovits, c JohnK.Inman, d JimA.Turpin, e WilliamG.Rice a and Ettore Appella b, * a Achillion Pharmaceuticals, Inc., 300 George Street, New Haven, CT O6511, USA b Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA c Laboratory of Antiviral Drug Mechanisms, SAIC Frederick, Frederick, MD 21702, USA d Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD 20892, USA e Infectious Disease Research Department, Southern Research Institute, 431 Aviation Way, Frederick, MD 21702, USA Received 23 August 2001; accepted 23 October 2001 Abstract—Hyper-mutable retroviruses such as HIV can become rapidly resistant to drugs used to treat infection. Strategies for coping with drug-resistant strains of virus include combination therapies, using viral protease and reverse transcriptase inhibitors. Another approach is the development of antiviral agents that attack mutationally nonpermissive targets that have functions essential for viral replication. Thus, the highly conserved nucleocapsid protein, NCp7, was chosen as a prime target in our search fornovelanti-HIVagentsthatcanovercometheproblemofviraldrugresistance.Recently,wereported(J. Med. Chem. 1999, 42, 67) a novel chemotype, the pyridinioalkanoyl thioesters (PATEs), based on 2-mercaptobenzamides as the thiol component and havingitsamidenitrogensubstitutedwithvariousphenylsulfonylmoieties.Thesecompoundswereidentifiedasrelativelynontoxic anti-HIV agents in the XTT cytoprotection assay. In this study, we wish to report a separate genre of active PATEs wherein the thiol component consists of an N-2-mercaptobenzoyl-amino acid derivative. Active derivatives (EC 50 < 10 mM) reported herein wereconfinedtoaminoacidprimaryamidesormethylamideshavingsidechainsnolargerthanisobutyl.Aminoacidsterminating in free carboxyl or carboxylic acid ester groups were mostly inactive. Selected compounds were shown to be active on chronically infectedCEM/SK-1,TNFa-inducedU1,ACH-2cellsandvirucidaloncell-freevirus,latentlyinfectedU1cellsandacutelyinfected primary peripheral blood mononuclear cells (PBMCs). # 2002ElsevierScienceLtd.Allrightsreserved. Introduction The HIV/AIDS epidemic continues to take its toll worldwide,despitemajoradvancesinunderstandingthe pathogenesis and treatment of HIV infection. One of the principal obstacles that has weakened the prospects for development of innovative therapeutic regimens is the tendency of HIV-1 to mutate to genotypes that are resistant to prevailing antiviral therapies. 1 4 One approachtoovercomethisproblemhasbeentheuseof multidrug cocktails 5,6 that seek to cripple the virus on multiple fronts, thus slowing progression to resistance. An alternative approach is the development of antiviral agents that target novel or mutationally intolerant tar- getsthatareessentialforvirusreplication. The nucleocapsid p7 protein (NCp7) of HIV-1 has recently been proposed and developed as a novel anti- retroviral target 7,8 for antiviral therapy based on both its biological mechanism of action and chemical prop- erties.Thebiologicalimportanceofthistargetrelatesto functions of the two retroviral zinc finger domains of NCp7 that provide essential functions during early and latephasesofHIVreplicationcycle.TheCys-Xaa 2 -Cys- Xaa 4 -His-Xaa 4 -Cys (CCHC) motifs 9,10 are present in both zinc fingers of HIV-1NCp7. The zinc chelating residues (three Cys, one His), as well as other specific amino acid residues in these structures, are highly con- served and mutationally intolerant. 11 Site-directed mutationalstudieshaverevealedthatchangesinanyof the zinc chelating and a number of non-chelating resi- dues in the zinc finger loops and adjacent sequences yields virions with defective RNA encapsidation and NCp7functionduringreversetranscriptionthatrenders them noninfectious. 12 14 0968-0896/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII:S0968-0896(01)00392-3 Bioorganic & Medicinal Chemistry 10 (2002) 1263–1273 *Corresponding author. Fax: +1-301-496-7220; e-mail: appellae@ pop.nci.nih.gov y Theseauthorshavemadeanequalcontribution.