Safety and Tolerability of 1 Month Daily (1HP) and 3 Months Weekly (3HP) Isoniazid and Rifapentine With Pharmacokinetics of Dolutegravir (DTG) in Pregnant People With HIV

Open-label, two-arm, randomized multicenter study to investigate the safety, tolerability, and pharmacokinetics (PK), and potential interactions between dolutegravir (DTG) and rifapentine (RPT) during pregnancy in people with HIV when RPT is given with isoniazid (INH) daily for 4 weeks (1HP) or weekly for 3 months (3HP) as part of tuberculosis (TB) preventive therapy (TPT). Adults (age ≥18) who are pregnant with a singleton pregnancy (confirmed by ultrasound) at a gestational age of 20-34 weeks and virally suppressed on an existing DTG-based plus two nucleoside reverse transcriptase inhibitors (NRTI) antiretroviral (ART) regimen for at least four weeks may participate.

Enrolled participants will be randomized 1:1 to Arms 1 and 2.

Arm 1: 1HP (n=126):

Participants will start twice-daily DTG on Day 0, and will receive once-daily HP for 28 total doses, starting on Day 1. HIV viral load (VL) will be measured at baseline (screening), week 3 (Day 17), at delivery, and post-partum week 12. Safety labs: complete blood count (CBC), urea and electrolytes (U\&E), creatinine, prothrombin time and international normalized ratio (PT/INR), and liver function tests (LFT) will be obtained at screening for everyone and at follow-up visits, if clinically indicated; CBCs and LFTs will be checked at delivery in all participants.

The first 25 participants enrolled to Arm 1 who consent to be in a PK substudy will participate in sparse PK blood collections for DTG. Sparse PK sampling for DTG will be performed on the morning of Day 1, before starting 1HP and before the morning dose of DTG. Additional sparse PK sampling for DTG will be performed prior to DTG dosing on Day 17 (to track with 72 hours after the 3rd dose of HP in Arm 2).

A plasma specimen for RPT PK will also be collected on Day 17.

Arm 2: 3HP (n=126):

Participants will start twice-daily DTG on Day 0, and will receive once-weekly HP for 12 total doses starting on Day 1. HIV VL will be measured at baseline (screening), week 3 (Day 17), at delivery, and at post-partum week 12. Safety labs: CBC, U\&E, creatinine, PT/INR, and LFTs will be obtained at screening for everyone and at follow-up visits, if clinically indicated; CBCs and LFTs will be drawn at delivery.

The first 25 participants enrolled to Arm 2 who consent to be in a PK substudy will participate in sparse PK blood collections for DTG. Sparse PK sampling for DTG will be performed on the morning of Day 1, before starting 3HP, and before the morning dose of DTG. Additional sparse PK sampling for DTG will be performed on Day 17 prior to DTG dosing (72 hours after the 3rd dose of HP) and on Day 52 prior to DTG dosing (72 hours after the 8th dose of HP).

There will not be plasma collection on Day 17 for RPT PK in Arm 2, because specimen collection would be 72 hours after the weekly HP dose and a RPT level will likely not be detectable.

Interim analysis will occur when 25 participants each from Arms 1 and 2 have completed the Week 3 (Day 17) sparse PK visit. Ongoing enrolment will not be paused during the interim analysis, which will assess DTG PK, safety, and VL data.

Enrollment will be paused if accrual to each arm reaches 101 participants before the interim analysis has been completed. Once results are available, then enrollment will restart with dosing (daily vs. BID) based on the DTG PK results.

Eligibility Criteria:
Inclusion Criteria:

1. Age \> 18 years
2. Weight \> 50 kg
3. Documented HIV infection
4. At least 4 weeks of ART and virally suppressed on dolutegravir plus two NRTIs
5. Undetectable HIV-1 viral load
6. Pregnancy at 20-34 weeks as confirmed by ultrasound
7. Singleton pregnancy

Exclusion Criteria:

1. Confirmed or suspected TB disease
2. Likely to move from the study area during the study period
3. Known exposure to pulmonary TB cases with known or suspected resistance to isoniazid or rifampicin in the source case
4. TB treatment within the past year
5. TB preventive therapy within the last year
6. Sensitivity or intolerance to isoniazid or rifamycins
7. On nevirapine, etravirine, rilpivirine, PI-based, or raltegravir-containing ART regimens
8. Suspected acute hepatitis or known chronic liver disease; HBsAg positivity; severe hepatic impairment
9. Alanine aminotransferase (ALT) ≥ 3 times the upper limit of normal (ULN)
10. Total bilirubin ≥ 2.5 times the ULN
11. Absolute neutrophil count (ANC) \< 750 cells/mm3
12. Creatinine clearance \< 50 ml/min
13. Self-reported alcohol use exceeding 21 units per week
14. Karnofsky status \< 80
15. On prohibited medications e.g. dofetilide