Susceptibility to PNU-140690 (Tipranavir) of human immunodeficiency virus type 1 isolates derived from patients with multidrug resistance to other protease inhibitors

In our study we examined the anti-human immunodeficiency virus type 1 (anti -HIV-1) activity of a novel HIV-1 protease inhibitor, PNU-140690 (tipranavi r), against patient-derived isolates resistant to multiple other protease i nhibitors (PIs). The aim of our experiments was to investigate the genotype s and the in vitro phenotypes of drug resistance of PNU-140690. We carried out drug susceptibility tests with peripheral blood mononuclear cells and a fixed amount of infectious virus (1,000 50% tissue culture infective doses ) to determine the 50% inhibitory concentration (IC50) and IC90, PCR assays for the detection of drug resistance mutations in RNA in plasma, and direc t sequencing of PCR products. Phenotypic resistance to PIs was invariably r elated to genotypic mutations, The substitutions among the amino acid resid ues of the protease included L101, K20R, L24I, M36I, N37D, G48V, I54V: L63P , I64V, A71V, V77I, V82A, I84V, and L90M. Isolates from all of the patients had developed a maximal degree of resistance to indinavir, ritonavir, and nelfinavir (IC(50)s, >0.1 mu M). We also compared these mutations with the amino acid changes previously described in association with in vivo tiprana vir administration. The mutations included the following: I15V, E35D, N37D, R41K, D60E, and A71T. Infections with IIIB, 14aPre, and N70 were inhibited by an average drug IC90 of 0.18 +/- 0.02 mu M in multiple experiments. The average mean +/- standard error of mean IC90 for the entire group of multi drug-resistant isolates derived from the mean values for two culture wells with p24 antigen supernatant appeared to be 0.619 +/- 0.055 mu M (range, 0. 31 to 0.86 mu M). Tipranavir retained a sustained antiviral activity agains t PI-MDR clinical isolates and might be useful in combination regimens with other antiretroviral agents for patients who have already failed other PI- containing therapies.