Resistance and cross-resistance to abacavir

Abacavir (ABC) is a potent nucleoside reverse transcriptase inhibitor (NRTI) used in multi-drug antiretroviral regimens and in combination with other NRTIs, protease and/or non-nucleoside reverse transcriptase inhibitors (NNRTIs) in both treatment naive and treatment experienced patients.

Resistance to ABC has been demonstrated in vitro and in vivo. Patterns of emerging mutations may vary when ABC is combined with other NRTIs relative to the mutations observed in monotherapy. Additionally, thymidine NRTIs may select for mutations that, while not selected for by ABC, may confer diminished susceptibility and diminished clinical response to ABC.

Resistance and clinical data indicate that ABC may be a suitable component of initial regimens and second or subsequent lines of therapy. It may be used as a substitution agent for persons wishing to discontinue protease inhibitor therapy who have not previously experienced viral rebound on NRTI therapy.