This study will assess the safety, tolerability and antiviral activity of a simplified PI-based treatment regimen (Kaletra,ä) compared to conventional HAART regimens in patients infected with HIV-1 who are on their first boosted-PI antiretroviral treatment regimen.

The potency of the antiviral activity of Kaletra has been clearly demonstrated in a wide spectrum of patients in a number of different clinical trials.6-9 The durable viral suppression seen after 4 years of therapy10 proves that it can provide effective, long-term treatment for people with HIV-1.

Data from one of these trials (M97-720),6 an ongoing Phase II study of lopinavir/ritonavir in combination with NRTIs suggests there may be a role for monoclass therapy with Kaletra in the treatment of HIV-1-infection.

Inclusion Criteria:

• Subject has confirmed his or her willingness to participate in this study after being informed of all aspects of the trial that are relevant to his or her decision to take part, by signing and dating the IRB / IEC approved informed consent form.
• Subject is HIV positive and on their first antiretroviral treatment regimen, based on any two NRTIs plus lopinavir/ritonavir or a ritonavir-boosted PI combination. Subject must have had no previous exposure to other regimens.
• Subject has a viral load <50 copies/ml at the time of baseline evaluation for at least 6 months.
• Subject has a CD4 cell count ³ 100 cells/mm3.
• Subject is aged >18 years.
• Vital signs, physical examination and laboratory results do not exhibit evidence of acute illness.
• Subject has not been treated for an active opportunistic infection within 30 days of screening.
• If female, subject has a negative pregnancy test and agrees to use, for the duration of the study, a barrier method of birth control that has a history of proven reliability as judged by the investigator.
• Subject does not require and agrees not to take, for the duration of the study, any medication that is contraindicated with any of the antiretroviral drugs in their treatment regimen. The subject agrees not to take any medication, including over-the-counter medicine, alcohol, or recreational drugs without the knowledge and permission of the principal investigator

Exclusion Criteria:

• Subject has current uncontrolled substance abuse or psychiatric illness that could preclude compliance with the protocol.
• Subject has a viral load of > 50 copies/ml
• Subject is HBsAg +
• Subject has active tuberculosis or an opportunistic infection.
• Subject has active malignancy (except Kaposi's Sarcoma).
• Subject has liver failure as evidenced by ALT / AST > 5 x Upper Limit of Normal (ULN).
• Female subject is pregnant or lactating.
• Subject has received an investigational drug within 30 days prior to the initiation of the study.
• Subject has modified his/her antiretroviral therapy during the 3 months prior to baseline or is intending to do so during the course of the study.