A Safety Study to Evaluate the Antiviral Activity of Darunavir in Combination With Ritonavir in HIV 1 Infected Children

Inclusion Criteria: * Participants with a documented HIV 1 infection (by any of the local standard diagnostic methods, such as HIV PCR-DNA, ELISA or western blot (WB) test for HIV antibodies, etc.) * Body weight from 10 kg to less than 20 kg at screening * Participants currently on stable ART (anti retroviral therapy) for at least 12 weeks, who need to change their ARV regimen because it is currently failing, with a viral load of greater than 1000 copies/mL * Screening genotype resistance test results showing less than 3 DRV resistance-associated mutations * Parents or legal representative willing and able to give consent Exclusion Criteria: * Participants with presence of any currently active conditions included in the listing of WHO ( World Health Organisation) Clinical Stage 4 and participants with presence of a non-HIV encephalopathy * Administration of any ARV (antiretroviral) or non-ARV investigational medication or investigational vaccine within 30 days prior to screening, except for those medications where dose recommendations for children are available * Life expectancy less than 6 months, according to the judgment of the investigator * Co-enrollment in other clinical and/or cohort trials without written permission of the Sponsor * Participants with any active clinically significant disease (eg, tuberculosis \[TB\], cardiac dysfunction, pancreatitis, acute viral infections) or findings during screening of medical history or physical examination that, in the investigator's opinion, would compromise the subject's safety or outcome of the study