Biotech Values

[DewDiligence]

Design of a Late-Stage HIV Trial

>I haven't followed HIV drugs before, so would appreciate some info on the typical P3 duration and endpoints.<

The main efficacy endpoint in late-stage HIV studies is typically the proportion of patients who achieve and maintain viral load below a pre-specified threshold (e.g. 400 copies/ml of plasma). Typical secondary endpoints include: a) the proportion of patients who reach a more stringent viral-load threshold (e.g. 50 copies/ml); and b) the mean increase relative to baseline in CD4 cell count.

The primary efficacy endpoint is typically evaluated at 48 weeks, but it may be done at 96 weeks or even 144 weeks. In any case, patients in phase-3 trials are generally followed for at least 144 weeks to evaluate safety.

Unlike trials in HCV, which evaluate the proportion of patients who are cured of their disease, HIV trials merely seek to show whether the virus can be held in check. Thus, there is no HIV endpoint that is comparable to the sustained virologic response (SVR) endpoint that is universally employed in late-stage HCV trials.

>Seems to me that not that many patients are required given the clear impact of the drug.<

Absolutely correct––this is the beauty of drug development in the antiviral arena. You find out very early whether or not a drug has efficacy at suppressing viral replication. By the time an antiviral drug gets into phase-2, there is usually little question about its efficacy, and hence the rest of the clinical-development program seeks to determine safety, tolerability, and (in the case of non-curable conditions such as HIV) cross-resistance to therapies that may have to be used later on.



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