Natl Conf Hum Retroviruses Relat Infect (1st). 1993 Dec 12-16;:137.
AIDS Clinical Trials Group protocol 194 is a placebo- controlled,
randomized study to evaluate the short-term virologic effect of
continuing ZDV, switching to ddI, or adding ddI in ZDV-resistant HIV-1
seropositive subjects with CD4 counts 100-300/microliter following
greater than 1 yr prior ZDV therapy. The trial has accrued 81 subjects
thus far; median pre-study duration of ZDV use was 2.6 yrs (25- 75%
range 1.9-3.6 yrs). Median absolute baseline CD4 count was
187/microliter (136-241/microliter). To date, of 31 persons evaluated,
34% had a sensitive baseline ZDV phenotype (IC50 less than or equal to
0.1 micromolar) by the ACTG/DOD consensus assay, 34% were intermediate
(0.1-1.0 micromolar), and 32% showed resistance (greater than or equal
to 1.0 micromolar). For a subset (n= 23) of these patients, the
occurrence of a mutation at pol codon 215 was associated with ZDV IC50
greater than or equal to 1.0 micromolar; genotypes were 35% wildtype,
30% mutant 215 codon, and 35% mixed. SI occurred in 11/20 of assayed
baseline isolates, but did not appear more often with resistant
isolates. IC50 showed no significant correlation with baseline viral
load by quantitative HIV-RNA (n=23, bDNA assay) or p24 antigen (n=31).
This ongoing trial shows high- level resistance at study entry for
one-third of subjects who had received over 2 years of prior ZDV. ZDV
susceptibility may not correlate with HIV-RNA, p24 antigen, or SI
phenotype.
Drug Resistance, Microbial/*GENETICS HIV-1/*DRUG
EFFECTS/ENZYMOLOGY/GENETICS Mutagenesis, Site-Directed Mutation
RNA-Directed DNA Polymerase/GENETICS Zidovudine/*PHARMACOLOGY ABSTRACT