BOOST: Study of Increased Dosage of Lopinavir/Ritonavir (LPV/r)

There are several reasons for low level viremia in patients on Kaletra (LPV/r), including poor adherence, incomplete absorption, cellular drug pumps or resistance mutations. Increasing exposure to protease inhibitors via boosting with ritonavir increases minimum blood concentrations, and is a strategy which has been shown to improve suppression of virologic replication. Little is known about the pharmacokinetics (PK), tolerability and safety of increased doses of LPV/r. The objectives of this 24-week single arm pilot study are to assess the PK parameters, safety, tolerability, change in viral load and CD4 counts on increased dose (600/150 and 800/200 mg) LPV/r in participants with low level viremia on standard dose LPV/r-based ART. Participants will undergo six PK samplings over 12 hours on standard dose LPV/r. The dose will be increased to 3 tabs (600/150) BID and blood will be sampled for PK after two weeks. If tolerated at 8 weeks, the dose will be increased to 4 tabs (800/200 mg) BID and final PK sampling will be performed after two weeks. There will be a one time, optional, optimization of background regimen of NRTIs two weeks after the first dose escalation. Major Eligibility Criteria: * CD4 count: \> 50 * Viral load: 200-75,000 on two most recent measures * Current treatment: \> 16 weeks standard dose (400/100mg BID) LPV/r-based ART (no other PI or NNRTI allowed * Prior treatment experience and resistance profile: Up to 20-fold resistance to LPV/r