The primary purpose of the study is to investigate the safety and efficacy of KP-1461 given every 12 hours for 124 days to HIV+ patients who have failed multiple antiretroviral regimens.

KP-1461 is a prodrug of KP-1212 triphosphate, a unique nucleoside that is incorporated into the HIV viral genome resulting in an accumulation of nucleic substitutions that interfere with viral replication. The study is designed to investigate the safety and antiviral activity for 124 days in antiretroviral-experienced HIV-1-infected subjects. By inducing additional mutagenic events in the viral genome, viral decay accelerators such as KP-1212 may force the virus to exceed the threshold of nonviability.

Inclusion Criteria:

• Asymptomatic HIV-1-infected individuals who are treatment-experienced and who have not been on ART for at least 16 weeks.
• Have documented prior non-suppressive ART including at least 1 NRTI, 1 NNRTI and 2 PIs; or have documented prior ART resistance to at least 1 NRTI, 1 NNRTI and 1 PI; AND in the opinion of the investigator, have few, if any, effective treatment options available.
• Have >2,500 copies/mL of HIV-1 RNA at screening.
• Have a stable CD4 cell count while off ART and >250 cells/mL at screening.
• Have no clinically significant findings on screening evaluations.

Exclusion Criteria:

• Have a current or recent opportunistic infection that, in the opinion of the investigator, is not being controlled by medication.
• Have any condition that, in the opinion of the investigator, could compromise subject safety or adherence to the protocol.
• Have a documented positive test for hepatitis B surface antigen, or have received any antiviral therapy for hepatitis C <6 weeks prior to study drug administration.