ART forgiveness is the ability of a regimen to maintain HIV-RNA suppression despite a documented imperfect adherence. We explored forgiveness of bictegravir/emtricitabine/tenofovir alafenamide (B/F/TAF).
In this retrospective cohort study pharmacy drug refills were used to calculate the proportion of days covered (PDC) as a proxy of adherence. Forgiveness was defined as the possibility to achieve a selected HIV-RNA threshold by a given level of imperfect adherence. A logistic model was applied to verify the impact of baseline variables and adherence on the virologic outcomes.
We enrolled 420 adults. From them, 787 one-year time-periods were derived for a median cohort follow-up of 873 person/years.
Most of them were males (73.1%); the most frequent risk factor for HIV infection was heterosexual contacts (49.5% of cases), followed by 22.5% MSM and 22.5% intravenous drug users. The median age of enrolled persons with HIV was 51 years (IQR 45-57 years); the median duration of HIV infection was 7.9 years (IQR 4-18 years) and the median nadir of CD4 cells was 277 cells/mcL (IQR 100-513 cells/mcL).
Adherence showed a median of 0.97 (IQR 0.91-1.00), consequently only 17 time-periods (2.2%) in 17 different individuals (4.0%) showed HIV-RNA blood levels above 200 copies/ml.
A PDC of 0.75 was sufficient to obtain in > 90% of cases the virologic outcome for both 200 copies/ml or 50 copies/ml. An adherence value of 0.85 obtained a positive response in virtually all subjects either for a cut-off of 50 or 200 copies/ml.
Long-term success of ART needs effective, well tolerated, friendly regimens. Adherence remains a crucial determinant of long-term success, but suboptimal adherence levels are relatively common. Given this, an elevated forgiveness plays a relevant role to further improve long-term outcomes and should be considered a fundamental characteristic of any antiretroviral regimen. B/F/TAF has been proved to have all of these characteristics.