The St. Marys and The Mater Switch Study (SMASH)

Inclusion Criteria:

• HIV-1 infected males or females
• Between 18 and 65 years of age
• Signed informed consent

• Currently receiving a stable antiretroviral regimen comprising of:

  • two licensed NRTIs including abacavir and/or didanosine
  • any licensed boosted protease inhibitor at any dose (excluding tipranavir*)
• Undetectable plasma HIV RNA to less than 50 copies/mL for at least 24 weeks prior to screening
• Availability of stored plasma with which to perform a tropism assay
• CCR5 tropic HIV virus based on a tropism assay from a stored plasma sample
• Willing to continue unchanged, or to modify antiretroviral therapy, in accordance with the randomisation assignment
• No documented viral resistance to currently licensed HIV-1 protease inhibitors based either on previous HIV-1 genotypic resistance testing or in the judgement of the study investigators
• No previous exposure to maraviroc or CCR5 receptor antagonists
• Subjects in good health upon medical history, physical exam, and laboratory testing in the opinion of the investigator

• Female subjects who are heterosexually active and of childbearing potential (i.e., not surgically sterile or at least two years post menopausal) must avoid becoming pregnancy as follows from screening through completion of the study using one or both of the following methods:

  • barrier contraceptives (condom, diaphragm with spermicide)
  • IUD PLUS a barrier contraceptive
• Female subjects of childbearing potential must have a negative pregnancy test

Exclusion Criteria:

• failure of current antiretroviral regimen due to virological failure
• active opportunistic infection, malignancy or significant co-morbidities in the opinion of the investigator
• pregnancy
• current prohibited concomitant medication (as listed in section 4.1.4)
• no available stored plasma sample predating their current antiretroviral regimen upon which a tropism assay can be performed
• active HBV infection as evidenced by positive hepatitis B surface antigen
• active hepatitis C virus infection as evidenced by positive HCV PCR or HCV antibody.