Monthly Update: Anti-infectives: Recent advances in HIV-1 protease inhibitors

Synergistic Inhibition of Human Immunodeficiency Virus Type 1 Replication in Vitro by Two- and Three-Drug Combinations of Delavirdine, Lamivudine and Zidovudine

Delavirdine (DLV), a non-nucleoside human immunodeficiency virus type 1 (HIV-1) reverse transcriptase inhibitor, was evaluated in two- and three-drug combination regimens with lamivudine (3TC) and zidovudine (ZDV). The effect of continuous drug treatment on HIV-1JR-CSF replication in human peripheral blood mononuclear cells was measured by an ELISA for p24 core antigen. Drug synergy, estimated by the combination index method and the method of Pritchard & Shipman, was observed when DLV was combined with 3TC over a range of drug concentrations (DLV at 1, 3, 10, 30 and 100 nM; 3TC at 3, 10, 30, 100 and 300 nM). Two-drug combinations of ZDV and DLV at a 1: 3 ratio or ZDV and 3TC at a 1: 10 ratio were synergistic at greater than 75% inhibition levels. Three-drug combinations of ZDV, DLV and 3TC (ZDV at 0.3, 1, 3 and 10 nM; DLV at 1, 3, 10 and 30 nM; 3TC at 3, 10, 30 and 100 nM) at the ratio of 1: 3: 10 also yielded significant synergistic effects. None of the combinations studied showed significant additive or synergistic drug toxicity. These in vitro data suggest that DLV should be evaluated in two- and three-drug combinations with 3TC and ZDV in clinical trials.

Topological models for the prediction of HIV-protease inhibitory activity of tetrahydropyrimidin-2-ones

Relationship between the topological indices and HIV-protease inhibitory activity of tetrahydropyrimidine-2-ones has been investigated. Three topological indices, Wiener's index--a distance based topological descriptor, Zagreb group parameter--an adjacency based topological descriptor and eccentric connectivity index--an adjacency-cum-distance based topological descriptor were used for the present investigations. A dataset comprising of 80 substituted tetrahydropyrimidine-2-one analogues was selected for the present studies. The values of the Wiener's index, Zagreb group parameter and eccentric connectivity index for each of the 80 compounds comprising the dataset were computed using an in-house computer program. The dataset was divided randomly into training and test sets. Resultant data was analyzed and suitable models were developed after identifying the active ranges in the training set. Subsequently, a biological activity was assigned to each of the compound involved in the test set using these models, which was then compared with the reported HIV-protease inhibitory activity. Accuracy of prediction using these models was found to vary from a minimum of approximately 86% to a maximum of approximately 88%.

6-Hydroxy-1,3-dioxin-4-ones as non-peptidic HIV protease inhibitors

HIV protease inhibitors containing 6-hydroxy-1,3-dioxin-4-one ring system as a new scaffold have been prepared. Among them, compound 4d showed potent HIV protease inhibitory activity (IC50 = 0.01 microM) and antiviral activity in cell culture (EC50 = 0.96 microM, SI = 65.69).

Structure-based discovery of Tipranavir disodium (PNU-140690E): a potent, orally bioavailable, nonpeptidic HIV protease inhibitor

Efforts to develop therapeutically relevant HIV protease inhibitors as medicinal agents in confronting the AIDS crisis have been aided by the wealth of fundamental information acquired during related drug discovery campaigns against other aspartyl proteases. This knowledge base was brought to full force with the broad screening identification of small, nonpeptidic, inhibitory molecules as templates for chemical elaboration. Significantly, the ability to collect crystallographic data on the inhibitor-enzyme complexes in a rapid fashion afforded the opportunity for a structure-based approach to drug discovery. Iterative cycles of synthesis, biological testing, and structural information gathering followed by prudent design modifications afforded compounds suitable for clinical evaluation. Displaying high enzymatic inhibition (Ki = 8 pM), potent in vitro antiviral cell culture activity (IC90 = 100 nM), and a useful pharmacokinetic profile, PNU-140690E (Tipranavir disodium) has entered into clinical studies. Promising results from these early trials supported further evaluation of this compound in HIV-infected individuals. PNU-140690E is currently under extensive clinical study.

Tipranavir (PNU-140690): a potent, orally bioavailable nonpeptidic HIV protease inhibitor of the 5,6-dihydro-4-hydroxy-2-pyrone sulfonamide class

A broad screening program previously identified phenprocoumon (1) as a small molecule template for inhibition of HIV protease. Subsequent modification of this lead through iterative cycles of structure-based design led to the activity enhancements of pyrone and dihydropyrone ring systems (II and V) and amide-based substitution (III). Incorporation of sulfonamide substitution within the dihydropyrone template provided a series of highly potent HIV protease inhibitors, with structure-activity relationships described in this paper. Crystallographic studies provided further information on important binding interactions responsible for high enzymatic binding. These studies culminated in compound VI, which inhibits HIV protease with a Ki value of 8 pM and shows an IC90 value of 100 nM in antiviral cell culture. Clinical trials of this compound (PNU-140690, Tipranavir) for treatment of HIV infection are currently underway.