Intervention: Rifaximin
Trial phase: Phase 2
ATC code: A07AA11 | D06AX11
SMILES: COC1C=COC2(C)Oc3c(C)c(O)c4c(O)c(c5c(nc6cc(C)ccn65)c4c3C2=O)NC(=O)C(C)=CC=CC(C)C(O)C(C)C(O)C(C)C(OC(C)=O)C1C
Sex: All
Age groups: Adult | Older Adult
Healthy volunteers: No
Participants at risk: 49
Group description: Participants were administered one 550 mg tablet of rifaximin to be taken orally two times a day for 4 weeks.
Eligibility criteria:
Inclusion Criteria:

HIV-1 infection
On ART for at least 96 weeks prior to study entry with a regimen that includes three or more antiretroviral medications. (Ritonavir ≤ 400 mg/day will not be considered a separate antiretroviral agent.)
No plans to change the antiretroviral regimen at least in the next 3 months after study entry.
CD4+ cell count < 350 cells/mm3 obtained within 120 days prior to study entry at any laboratory that has a Clinical Laboratory Improvement Amendments (CLIA) certification or its equivalent.
All previous CD4+ cell counts should be < 350 cells/mm3 for at least 96 weeks prior to study entry while subjects were on ART. (A single CD4+ cell count ≥ 350 cells/mm3 is permitted within 96 weeks prior to study entry while subjects were on ART.)
Documentation of HIV-1 RNA below the limit of detection (e.g., < 50 copies/mL on Roche Amplicor HIV-1 Monitor assay, < 75 copies/mL on the Versant HIV-1 RNA assay by branched DNA, < 400 copies/mL on a standard Roche Amplicor assay, < 40 copies/mL on the Abbott m2000sp/m2000rt real-time PCR test, < 48 copies/mL on the COBAS AmpliPrep/TAQMAN HIV-1 assay) verified by at least two measurements prior to study entry, one of which must be at least 48 weeks prior to study entry and one measurement that was obtained between 121 days and 48 weeks prior to study entry.
Screening HIV-1 RNA below the limit of detection obtained within 120 days prior to study entry using a FDA -approved assay (e.g., < 50 copies/mL on Roche Amplicor HIV-1 Monitor assay, < 75 copies/mL on the Versant HIV-1 RNA assay by branched DNA, < 40 copies/mL on the Abbott m2000sp/m2000rt real-time PCR test, < 48 copies/mL on the COBAS AmpliPrep/TAQMAN HIV-1 assay). (The virologic assay must have a lower limit of detection of ≤ 75 copies/mL.)
All other plasma HIV-1 RNA measurements in the 48 weeks prior to study entry must be below the limit of detection. (A single detectable measurement of ≤ 200 copies/mL is permitted if RNA levels immediately before and after are below the limits of detection for the assay.)
Certain fasting laboratory values obtained within 45 days prior to entry as indicated in Section 4.1.9 of the protocol.
Pre-entry peripheral blood mononuclear cell (PBMC) specimen for assay of the primary immune activation endpoint (change in CD8+ T-cells activation (%HLA-DR+CD38+CD8+ T-cells) has been obtained. Sites must receive confirmation from the processing lab via phone, e-mail, or fax, that this specimen has been entered into the ACTG's Laboratory Data Management System (LDMS).
Female subjects of reproductive potential must have a negative serum or urine β-HCG pregnancy test with a sensitivity of at least 50 mIU/mL performed within 24 hours prior to study entry.
If participating in sexual activity that could lead to pregnancy, the female subject must agree to use one form of contraceptive as listed in section 4.1.11 of the protocol while receiving protocol-specified treatment and for 4 weeks after stopping the treatment.
If the female subject is not of reproductive potential, she is eligible without requiring the use of a contraceptive. Self report is acceptable documentation of sterilization, other contraceptive methods, and menopause.
Ability and willingness of subject or legally authorized representative to provide informed consent.

Exclusion Criteria:

Active diarrhea (3 or more unformed stools per day) within 28 days prior to study entry (except if site investigator or primary care provider attributes diarrhea to antiretroviral or azithromycin use).
History of or active inflammatory bowel disease.
History of or active Clostridium difficile colitis.
History of significant liver disease, defined as having chronic liver disease (including chronic alcoholic liver disease, hepatitis B or C), plus either: a) ascites, b) encephalopathy, or c) a Child-Pugh Score of > 7.
Receipt of antimicrobial therapy within 30 days prior to study entry. (NOTE: Antimicrobial use for prophylaxis of opportunistic infections, e.g., azithromycin or trimethoprim-sulfamethoxazole, is allowed.)
Active infection requiring the use of antibiotics within 30 days prior to study entry.
Known allergy/sensitivity or any hypersensitivity to components of study drug or their formulation (e.g., allergy to rifampin).
Serious illness requiring systemic treatment and/or hospitalization within 14 days prior to entry.

Use of any of the following medications for more than 3 consecutive days within the 60 days prior to study entry:

Immunosuppressives
Immune modulators
Antineoplastic agents
Probiotics
Anticoagulants
Vaccinations within 1 week prior to the pre-entry or study entry visits. (NOTE: Subjects are encouraged to get the flu vaccine prior to study pre-entry visit.)
Participation on any HIV immunotherapy/therapeutic vaccination trials within 6 months prior to study entry.
Active drug or alcohol use or dependence that, in the opinion of the site investigator, would interfere with adherence to study requirements.
Breastfeeding.