HIV-1-infected patients with advanced disease failing a raltegravir-containing salvage regimen in São Paulo, Brazil.

Raltegravir (RAL) is the first licensed antiretroviral integrase inhibitor that may be used both for treatment-naïve human immunodeficiency virus type 1 (HIV-1) patients and for salvage therapy. The Brazilian public free access programme limits its use for salvage therapy, with scarce information regarding RAL resistance from patients failing a RAL-containing salvage regimen. This study evaluated RAL resistance mutations detected by population sequencing in 69 HIV-infected patients with advanced disease failing a RAL-containing regimen in a real-world setting. RAL resistance mutations were identified in 47/69 patients (68%). The most common salvage regimen, used by 56/69 patients (81%), included lamivudine, tenofovir, darunavir/ritonavir and RAL. At failure, major RAL resistance mutations included Q148H/R/K (21/47; 45%), N155H (14/47; 30%), Y143R/H/C (3/47; 6%) and E92Q (1/47; 2%). Most samples with Q148H/R/K also showed G140S/A/C (21/47; 45%). RAL resistance was significantly associated with less than two active drugs in the optimised background therapy regimen at failure [39/39 (100%) vs. 9/17 (53%); P<0.001] and with a longer cumulative duration with detectable viraemia (viral load >50 copies/mL) (86 weeks vs. 32 weeks; P=0.001). A high frequency of RAL mutations was observed in this study. In addition, these results reinforce the importance of close monitoring of RAL-containing regimens to reduce the time of failure and consequent resistance accumulation.