July 12, 2000
Can efavirenz be used successfully in those who have already developed resistance to another non-nucleoside? While there are reasons based on genotypic testing to expect that it could, the results of this cohort study suggest otherwise. The researchers reported on the initial outcomes of 67 patients who were all given efavirenz after having been treated with multiple other regimens. This group had taken a median of seven prior antivirals. This included some people who had already taken one of the other non-nucleosides (nevirapine or delavirdine). Unfortunately, the predictors of failure on the efavirenz-containing regimen -- including past use of another non-nucleoside -- with this group twice as likely to see viral rebound than those who had not taken a non-nucleoside in the past. The number of genotypic mutations known to confer resistance to the non-nucleoside class was also correlated with subsequent rebound on efavirenz.
This study confirms the work done by several others that suggest that there is significant cross-resistance in the currently available non-nucleoside antivirals. Thus, it appears that if one of these meds has already been taken in a non-suppressive regimen, another one of the current group is unlikely to be successful. Research continues to hopefully develop new active agents in this class that will not be as cross-resistant as these have been.