The purpose of this study is to characterize the pharmacokinetics (PK) of understudied drugs administered to lactating women, receiving antiretroviral drugs per SOC as prescribed by their healthcare provider, and their co-enrolled infants ≤180 days of age who receive maternal breastmilk.

Prospective, single-site, open label, PK and safety study. Co-enrollment of lactating women ≥18 years of age receiving drugs of interest (DOIs) per standard of care (SOC), as prescribed by their healthcare providers, and their infants who receive maternal breastmilk ≤180 days postpartum.

To understand drug transfer into breastmilk and determine subsequent infant exposure, biological samples will be collected from lactating women (blood and breastmilk) and infants (blood). The opportunistic design of this study will allow for a minimal risk study, an expanded enrollment net, evaluation of antiretroviral drugs, and capitalization of procedures performed per SOC to maximize study efficiency and data collection and minimize potential risk to participants. The data collected through this initiative will provide valuable PK, dosing, and safety information for drugs in this vulnerable population in order to inform public health.

Inclusion Criteria Mothers/Infants:

1. Lactating women ≥18 years of age who are receiving at least one DOI per SOC who are ≤180 days postpartum, and their infants (≤180 days of age) who receive maternal breastmilk.

2. Informed consent, according to local IRB/REB/IEC guidelines, prior to any study-related procedures.

3. If the mother is receiving more than one DOI, the mother must have taken all DOIs that she is receiving concomitantly for the 6 doses prior to sample collection.

4. Mother participant is fluent in English or Setswana.

5. Willing to provide at least 1 of the below required samples between the co-enrolled mother/infant pair:

   • Maternal breastmilk
   • Infant blood

Exclusion Criteria Mothers/Infants:

1. Any concomitant condition which, in the opinion of the participant's healthcare provider, the site principal investigator (PI), a research nurse, or designee conducting the study, would preclude participation in the study.
2. Known pregnancy of mother during sample collection.
3. Mother has pumped any breastmilk at all in between the last 6 direct infant feedings prior to sample collection.
4. Infant was fed breastmilk in any manner besides nursing at mother's breast for any of the last 6 feedings prior to sample collection.
5. Previous enrollment on this study.

Approximately 50 eligible lactating women and their breastmilk fed infants per DOI will be co-enrolled. Participants may be enrolled for one or more DOIs with a single consent. The co-enrollment of mothers and more than 1 infant (multiple birth) is permitted.

After the study is completed, information about the study, including de-identified study data, will be submitted to the NIH data repository (https://dash.nichd.nih.gov and referred to below as "DASH"). With NIH approval, the data submitted to DASH may be used by other researchers for future research. The study data submitted to DASH will be de-identified, meaning it will not include any information that can identify the participant. The study team may also share the de-identified study data with other researchers. When the participant's de-identified study data are provided to other researchers for the purposes of future research, it will be done without obtaining additional permission from the participant.

Data will be uploaded to the repository within 2 years of study completion. Biological samples will be stored indefinitely. If a participant decides to withdraw from the study, they will be instructed per the ICF to contact the site investigator. Study data and samples that have been recorded / collected prior to withdrawal will continue to be used, but no new data or samples will be collected.

In order to have access, researchers have to complete a Data access request. NICHD will review the request and either approve or deny it. IRB approval must be obtained by the researcher to access the data.