Identification of constrained peptidomimetic chemotypes as HIV protease inhibitors.

Small-molecule peptidomimetic inhibitors that already showed activity towards Secreted aspartic protease 2 as anti-Candida agents are herein presented as candidate HIV protease inhibitors. A library of 6,8-dioxa-3-azabicyclo[3.2.1]-octane peptidomimetic scaffolds was screened towards HIV protease, resulting in the identification of hit compounds possessing IC50 in the sub-micromolar range, and showing the bicyclic acetal portion as a potential transition state analogue in the interaction with catalytic aspartic acid residues.

Evaluation of efficacy, pharmacokinetics and tolerability of peptidomimetic aspartic proteinase inhibitors as cream formulation in experimental vaginal candidiasis.

OBJECTIVES: It has been previously shown that the treatment with the two protease inhibitors APG12 and APG19 confers protection in a rat model of mucosal candidiasis; in this study, we examined whether these peptidomimetic inhibitors are also effective as a cream formulation in reducing Candida albicans vaginal infection. METHODS: These efficacy studies were performed in a rat model of estrogen-dependent rat vaginitis by C. albicans on both azole-susceptible and azole-resistant C. albicans, and on both caspofungin-susceptible and caspofungin-resistant C. albicans strains. In vivo studies were also conducted in female albino rats and rabbits to obtain information about the safety, local tolerability and principal pharmacokinetics parameters of the two compounds. KEY FINDINGS AND CONCLUSIONS: Both hit compounds showed remarkable results within the 48-h range as effective inhibitors of the infection, particularly causing rapid decay of vaginal C. albicans burden. Importantly, the two compounds showed marked acceleration of fungus clearance in the rats challenged with the fluconazole-resistant as well as with the capsofungin-resistant strain of C. albicans. Both compounds showed fast elimination rates when given by the intravenous route, and poor systemic absorption after intravaginal cream administration. Test drugs were also well tolerated in 7-day local tolerability experiments in the rabbit.

Insight into the structural similarity between HIV protease and secreted aspartic protease-2 and binding mode analysis of HIV-Candida albicans inhibitors.

The analysis of the structural similarity between Candida albicans Sap2 and HIV-1 aspartic proteases by molecular modeling gave insight into the common requirements for inhibition of both targets. Structure superimposition of Sap2 and HIV-1 protease confirmed the similarity between their active sites and flap regions. HIV-1 protease inhibitors herein investigated can fit the active site of Sap2, adopting very similar ligand-backbone conformations. In particular, key anchoring sites consisting of Gly85 in Sap2 and Ile50 in HIV-1 protease, both belonging to their corresponding flap regions, were found as elements of a similar binding-mode interaction. The knowledge of the molecular basis for binding to both Sap2 and HIV-1 proteases may ultimately lead to the development of single inhibitor acting on both targets.

Bicyclic peptidomimetics targeting secreted aspartic protease 2 (SAP2) from Candida albicans reveal a constrained inhibitory chemotype.

The in vitro screening of stereoisomeric bicyclic peptidomimetics towards SAP2 of Candida albicans revealed a constrained chemotype as aspartic protease inhibitor in the micromolar to nanomolar range. The results indicated that the acetal bridge may serve as a transition-state isostere, and that the right match between interactions with subsites and the orientation by hydrogen bonding with Gly85 is the main requisite for inhibitory activity. Molecular docking calculations suggested the bicyclic acetal scaffold to be capable of interacting with the two catalytic aspartic acids, thus resulting in good inhibitory activity with only two hydrophobic groups addressing the enzyme catalytic subsites.

D-proline-based peptidomimetic inhibitors of anthrax lethal factor.

In this work we reported the generation of d-proline-derived hydroxamic acids as inhibitors of anthrax lethal factor (LF), taking advantage of a pyrrolidine ring as the central scaffold and a hydroxamate group as the Zn(2+) chelating agent. The introduction of two hydrophobic groups addressing the S1' subsite and a long substrate-binding groove was conceived by overlapping the bioactive conformations of two reported LF inhibitors. Micromolar affinity of compound 38 suggested cis-3-substituted-1-sulfonamido-d-proline hydroxamic acids as a promising class of peptidomimetic inhibitors for developing novel LF inhibitors.

Novel small molecules for the treatment of infections caused by Candida albicans: a patent review (2002-2010).

INTRODUCTION: The fungal pathogen Candida albicans is one of the leading causes of infections affecting immunodeficient individuals, including those HIV-infected and patients undergoing cancer therapy. Emerging problems in terms of therapeutic efficacy and drug resistance have highlighted the need to consider new therapeutic approaches, based on the exploitation of virulence factors as alternatives to conventional drug targets. AREAS COVERED: Advances in the development of anti-Candida drugs are examined in this review, as reflected by the patent literature since 2002 along with selected peer-reviewed publications. Taking into account a total of 26 patents, the discussion encompasses several therapeutic approaches, including azoles as ergosterol biosynthesis inhibitors, glucan and chitin synthase inhibitors, and secreted aspartyl protease inhibitors. EXPERT OPINION: New analogs of existing drugs are being developed as broad spectrum antifungals to improve efficacy and circumvent drug resistance. Also, candidate drugs targeting new virulence factors are promising to overcome limitations due to poor efficacy and the rising of drug resistance observed for several available drugs. Efforts for the discovery and development of antifungal agents should be equivalent to other therapeutic areas, and advances in the generation of therapeutic agents with fungus-specific mechanisms of action are of highest priority.