Pharmacokinetic Study of Antiretroviral Drugs and Related Drugs During and After Pregnancy

Pharmacokinetic Properties of Antiretroviral and Related Drugs During Pregnancy and Postpartum

IMPAACT P1026s is a Phase IV prospective clinical study to evaluate the pharmacokinetics (PKs) of antiretroviral (ARV) and tuberculosis (TB) medications in pregnant women and their infants. (Pharmacokinetics are the various interactions between a drug and the body.) This study also evaluated the PKs of certain ARVs in postpartum women before and after starting hormonal contraceptives. The PKs of these drugs were evaluated by measuring the amount of medicine present in blood and/or vaginal secretions.

Pregnant women experience unique physiological changes that may result in clinically significant alterations in drug PKs. Unfortunately, there have been few clinical trials to study the PKs of ARV, TB, and hormonal contraceptive drugs in pregnant women. The development of appropriate dosing regimens for the HIV-infected pregnant woman is critical to the health of both mother and fetus. Overdosing may lead to maternal adverse events and increased risk of fetal toxicity, while underdosing may lead to inadequate virologic control, increased risk of developing drug resistance mutations, and a higher rate of perinatal HIV transmission. This study evaluated the PKs of ARVs used during pregnancy; the PKs of TB drugs used during pregnancy, both in women who are HIV-positive and also taking ARVs and in women who are HIV-negative and not taking ARVs; and the PKs of hormonal contraceptive medications taken along with ARVs.

P1026s is a Phase IV clinical study. Participants were not assigned to the drugs under study, but were already receiving the drugs for clinical care by prescription of their clinical care providers. They were enrolled into study arms according to the drugs they were receiving through clinical care, and if on multiple drugs of interest, were able to enroll into multiple arms simultaneously. No drugs were provided as part of this study. This observational study was added to an existing investigational new drug (IND) number because several of the drugs were studied at a higher does than the approved dose after the PK results for the approved dose were found to be inadequate.

P1026s went through 10 protocol versions, with the first and last versions of the protocol finalized in 2002 and 2016, respectively. New study arms were added and analyzed separately with each update of the protocol version. In general, there were five main groups of study arms: HIV-infected pregnant women taking ARVs without TB treatment, HIV-infected pregnant women taking ARVs with first-line TB treatment, HIV-uninfected pregnant women taking no ARVs with first-line TB treatment, HIV-infected and HIV-uninfected pregnant women with or without ARVs with second-line TB treatment for drug-resistant TB, and HIV-infected postpartum women taking ARVs and hormonal contraceptives. The primary analysis of each arm was designed and conducted as a separate single arm evaluation of the drug (or combination of drugs) of interest.

Women who were 20 0/7 weeks to 37 6/7 weeks pregnant were enrolled in this study and remained in the study for up to 12 weeks after delivery. Postpartum women were enrolled at 2 to 12 weeks after delivery and followed until 6 to 7 weeks after starting contraceptives. Infants were enrolled in-utero and followed for 16 to 24 weeks of life. At all study visits, participants underwent a medical history, a physical exam, and blood collection. At some visits, women in some arms underwent a vaginal swab. Blood collection from the mother and the detached umbilical cord occurred during delivery. Intensive PK sampling was performed at study visits during the second and third trimester of pregnancy and/or postpartum, depending on the study arm. Additional study visits may have occurred depending on the ARV drug regimen prescribed. Infant washout PK samples were collected at 2-10, 18-28, 36-72 hours after birth, and 5-9 days of life.

There are a total of 49 study arms across all versions of P1026s protocols. Out of the 49 study arms, 2 did not have PK data* [didanosine delayed release (DDI) and lopinavir/ritonavir (LPV/RTV) African sites only]; 2 never enrolled any participants [amprenavir (APV) and nevirapine/rifampicin (NVP/RIF) with at least one first line TB drug]; 9 are in the line to be tested/analyzed due to batched analysis which has to be done after the end of the study, the lengthy process of development, validation and approval (regulatory burdens), and laboratory delays related to the COVID-19 pandemic [all TB arms and all but 3 contraceptive arms (atazanavir/ritonavir/tenofovir (ATV/RTV/TFV) with etonogestrel (ENG), efavirenz (EFV) with ENG, and LPV/RTV with ENG)]; and 8 had completion dates earlier than December 26, 2007 [nevirapine (NVP), abacavir (ABC), LPV/RTV 400/100 mg twice daily (b.i.d.), LPV/RTV 400/100mg then 533/133mg b.i.d, nelfinavir (NFV), emtricitabine (FTC), indinavir/ritonavir (IDV/RTV), and tipranavir/ritonavir]. In this submission, the Results Section presents participant flow, baseline characteristics and adverse events for all study arms (except the 2 arms that never enrolled), and outcome measure results for the 28 remaining study arms that have been completed and have final results available. For study arms completed prior to December 26, 2007, refer to the study publications in the References section for outcome measures.

For arms with very low enrollment (N<3), some results throughout the record (e.g. baseline characteristics and outcome measures) were not reported in order to avoid making individual participant data identifiable.

In the Outcome Measures section, there could be multiple outcome measures for same PK parameters (e.g. AUC12) depending on different units or summary statistics used in the analyses (such as median with range vs. median with interquartile range (IQR)).

Maternal Inclusion Criteria:

• Participant must belong to one of the following 5 groups:

  1. HIV-infected pregnant women greater than or equal to 20 weeks gestation NOT on TB treatment receiving one or more of the ARV drugs/drug combinations specified in the protocol
  2. HIV-infected pregnant women greater than or equal to 20 weeks gestation receiving one of the ARV drugs/drug combinations specified in the protocol and TB treatment with at least one of the TB drugs, specified in the protocol, at study entry
  3. HIV-uninfected pregnant women greater than or equal to 20 weeks gestation receiving at least two of the first-line TB drugs, specified in the protocol, at study entry
  4. HIV-infected and HIV-uninfected pregnant women greater than or equal to 20 weeks gestation receiving at least two of the second-line TB drugs, specified in the protocol, at study entry
  5. HIV-infected women 2 to 12 weeks (14 to 84 days) post-delivery receiving one of the ARV drug combinations listed in the protocol AND starting postpartum contraceptives as listed in the protocol

• The woman must be stable on the ARV drug/drug combination and/or TB drug combination for at least 2 weeks prior to PK sampling

• If a woman is receiving a specific generic ARV formulation, the protocol team has approved this formulation

• HIV-infected pregnant women must be planning to continue on current ARV regimen until postpartum PK sampling is completed. HIV-infected postpartum women on hormonal contraceptives must be planning to continue on ARV and contraceptive regimens until final PK sampling is completed

• For HIV-infected women: confirmed HIV infection, documented by positive results from two samples collected at different time points prior to study entry. More information on this criterion can be found in the protocol.

• HIV-uninfected pregnant women must have documented negative HIV antibody test during current pregnancy. Note: adequate source documentation, including the date of specimen collection, date of testing, test performed, and test result, must be available.

• Participants enrolling in the 3rd trimester must enroll by 37 6/7 weeks gestation

• Participant can provide legal informed consent per local regulations

• If a woman has completed this study and becomes pregnant again, she may re-enroll in the study only if she is enrolled in a different arm than that studied during her initial enrollment

Maternal Exclusion Criteria:

• Women on medicines known to interfere with absorption, metabolism, or clearance of the drug being evaluated (see protocol for more information). Rifampicin is permitted for women being evaluated for TB and ARV drug interactions
• If pregnant, carrying multiple fetuses
• Clinical or laboratory toxicity that, in the opinion of the site investigator, would be likely to require a change in the medicine regimen during the period of study

Infant Enrollment Criteria:

- All infants of mothers enrolled during pregnancy (meeting criteria specified above) are enrolled, in utero, immediately after maternal enrollment.

Infant Requirements for Washout Pharmacokinetic Sampling:

• Born to HIV-infected mother enrolled during pregnancy in an ARV arm (does not include infants born to HIV-uninfected mothers receiving TB drugs)
• Birth weight greater than 1000 grams
• Is NOT receiving disallowed medications described in Section 7 of the protocol
• Does not have any severe congenital malformation or other medical condition not compatible with life or that would interfere with study participation or interpretation, as judged by the site investigator
• Born after singleton delivery (not after multiple birth)