- Participants who are HLA-B*5701 positive and are unable to use an nuclease reverse transcriptase inhibitors (NRTI) backbone that does not contain abacavir (participants who are HLA-B*5701 positive may be enrolled if they use a NRTI backbone that does not contain abacavir; HLA-B*5701 positive participants may be excluded from the study if local provision of an alternate NRTI backbone is not possible).