Researchers, led by Barbara Rossetti, aimed to measure the effectiveness and durability of integrase strand transfer inhibitor (INSTI)-based regimens in previously treated patients with human immunodeficiency virus (HIV) in Europe. Their study, published in HIV Medicine, reported that “both [virologic failure (VF)] INSTI discontinuation occur at substantial rates in viremic subjects.”

The researchers analyzed 13,560 treatment records of treatment-experienced patients who had started an INSTI-based regimen in the INTEGRATE study. The primary endpoints of the analysis were time to treatment discontinuation, and time to virologic failure, defined as “one measurement of viral load (VL) ≥ 1000 copies/mL or two ≥ 50 copies/ml or one VL measurement ≥ 50 copies/mL followed by treatment change.”

Among all the records, 4,284 were from INSTI-naïve and non-viremic (IN-NV) patients; 1,465 were from INSTI-naïve and viremic (IN-V) patients; 6,016 from INSTI-experienced and non-viremic (IE-NV) patients; and 1,795 were from INSTI-experienced and viremic (IE-V) patients. According to the investigators, major drug resistant mutations (DRMs) were previously seen in 4/519 (0.8%) IN-NV, 3/394 (0.8%) IN-V, 7/1510 (0.5%) IE-NV and 25/935 (2.7%) IE-V individuals.

Given poor time to VF and discontinuation in viremic patients, the study’s collaborators concluded that viremic subjects still face poorer outcomes. In closing, the authors also stressed that the observation of INSTI DRMS in a proportion of their cohort “makes INSTI resistance testing mandatory after failure.”