To assess the safety of 48 weeks of treatment with 10 milligrams (mg) of elvucitabine in combination with background antiretroviral therapy (ART) in participants who completed Study ACH443-014A and meet the inclusion and exclusion criteria.

This study is an open-label extension study for participants who have completed 14 days of treatment in Study ACH443-014A and meet all inclusion and exclusion criteria. Elvucitabine treatment (10 mg) will begin on Day 1 (Day 15 following completion of Study ACH443-014A) for all consenting participants in combination with background ART as determined by the Principal Investigator. Participants will have clinical and laboratory assessments every 2 weeks for the first 8 weeks and then every 4 weeks to Week 48.

Inclusion Criteria:

• Participants who have completed 14 days of treatment in Study ACH443-014A and who, in the Investigator's judgment, remain candidates to receive elvucitabine together with background ART.

Exclusion Criteria:

• Failure to meet inclusion criteria