This is a Phase I, multi-site, open-label, non-comparative study of the PK, safety, tolerability, and acceptability of a single-dose of pretomanid added to an OBR in infants, children, and adolescents with RR-TB. The term children is used within the protocol to indicate the total age range from infants through adolescents; enrollment will be limited to children assigned female sex at birth and enrollment of neonates will be deferred until safety and pharmacokinetic data are available in older groups, pending review by the CMC and SMC during the interim analysis. Refer to the study design and the study eligibility criteria and a description of the study recruitment, screening, and enrollment process. Participants are expected to be enrolled at study sites in Brazil, India, South Africa, Tanzania, and Thailand. Up to 72 participants will be enrolled to achieve at least nine evaluable participants in each of four weight groups, for a total of at least 36 enrolled participants.

Participants will receive a single dose of pretomanid on the day of study entry. No additional doses of pretomanid will be administered; participants will continue their OBR. Intensive PK sampling and safety monitoring will be performed on the day of study entry and over the course of the next 48 hours. Participants will then complete a final study visit approximately two weeks after study entry.