3rd International Workshop on HIV Drug Resistance 2-5 August 1994, Kauai, Hawaii, USA

COMPREHENSIVE ANALYSIS OF HIV-1 VARIANTS INDIVIDUALLY SELECTED FOR RESISTANCE TO SIX HIV PROTEASE INHIBITORS

Int Wkshop HIV Drug Res 1994 Aug 2-5;3:14 (abstract no. 13)

M. Tisdale, R. Myers, N.R. Parry, N. Oliver, B. Maschera, and E. Blair
Wellcome Research Labs., UK

Studies were undertaken to determine the potential for HIV-1 to develop resistance in cell culture to a panel of six HIV protease inhibitors. The six compounds were Roche, Ro3l-8959; Abbott, A77003; Dupont-Merck, XM323; Merck, L-735524 (synthesised by Dr R Tung and D.D. Deininger at Vertex); Agouron, Ag-1284 and Vertex, VBll-328. Initially, HIV-1 (clone HXB2) was grown in MT4 cells in a range of inhibitor concentrations, up to 10X the predetermined IC₅₀ value, to ascertain the maximum compound concentration which permitted virus growth. Virus from the highest permissive concentration was used for further passage in progressively increasing concentrations of inhibitor. Sensitivity assays were performed at passes 4 and 6, and the DNA sequence of the virus protease region analysed at each pass.

Resistant variants were selected within six passes for all the protease inhibitors examined, with reductions in sensitivity from 3 - 40 fold. Sequence analysis revealed from 1 - 4 mutations within the protease region after passage with each inhibitor. Changes observed were, G48V, L90M (Ro3l-8959); R8Q/K, M46I, G48V (A77003); L10F, K45I, I84V, (XM323); V32I, M46L, V82A, (L-735524); A7lV/T, V77I, V82A, T9lA (Ag1284) and I50V, M46I, I47V (VBll,328). In addition, passage of the AZT resistant clone RTMC (RT mutations at 67N, 70R, 2l5F, 2l9Q) in increasing concentrations of Ro3l-8959 produced dual resistance to AZT and Ro3l-8959 with mutations in protease at G48V, I84V, and L90M. Infectious molecular clones have been constructed to determine the contribution of individual mutations to the resistance phenotype. Sensitivity assays with the 6 passaged virus variants against the 6 protease inhibitors show that not all are co-resistant. These data suggest that some protease inhibitors may be useful together in combination therapy to slow development of resistance. Virus is currently being passed in the combined presence of 2 protease inhibitors in cell culture in an attempt to determine possible constraints on resistance development. In vitro resistance studies should provide useful information for future combination trials with protease and RT inhibitors.

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1994-08-02
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