Background: The pilot Phase IIb VIKING study suggested that dolutegravir (DTG), an HIV integrase inhibitor (INI), is efficacious in INI-resistant patients at the 50 mg twice-daily dose. However, DTG response was most reduced in subjects carrying resistance-associated mutations at position G140 and Q148. These mutations can cause a 10-20-fold reduced susceptibility to DTG as well as a 96% lower odds of achieving HIV-1 RNA <50 copies/ml at week 24 if compared with those with no mutations at these positions.
Methods: Five multi-experienced patients harbouring the mutation complex G140-Q148, resistant to at least three drug classes, and previously exposed to DTG 50 mg twice daily, were treated with an increased dose of DTG (100 mg twice daily) in association with an optimized background regimen (OBR) based on their individual viral genotyping assays. The blood concentration of DTG was measured in order to determine whether a solubility issue is related with this high dosage.
Results: Four out of five patients attained an HIV-1 RNA <50 copies/ml at week 48 and no relevant adverse events were detected. The measured DTG blood concentration was that expected for the administered dosage, ruling out any solubility concerns.
Conclusions: For the first time 100 mg twice daily of DTG was administered to five multi-experienced patients harbouring the mutation complex G140-Q148. Although a small number of patients were tested, the results show a potential for a high-dose regimen of DTG as a rescue therapy in patients harbouring integrase strand transfer inhibitor resistant viruses.