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Aim We aimed to explore the effect of pregnancy on bedaquiline pharmacokinetics and describe bedaquiline exposure in the human milk of mothers treated for rifampicin-resistant TB, where there is no human data available. Methods We performed a longitudinal pharmacokinetic study in pregnant women treated for rifampicin-resistant TB to explore the effect of pregnancy on bedaquiline exposure. Pharmacokinetic sampling was performed at four time-points over six hours in the third trimester, and again at approximately six weeks postpartum. We obtained serial human milk samples from breastfeeding mothers, and a single plasma sample taken from breastfed and non-breastfed infants to assess bedaquiline exposure. We used liquid chromatography-tandem mass spectrometry to perform the human milk and plasma bedaquiline assays, and population pharmacokinetic modelling to interpret the bedaquiline concentrations. Results We recruited 13 women, six of whom completed the ante- and post-partum PK sampling. All participants were HIV-positive on antiretroviral therapy. We observed lower ante- and post-partum bedaquiline exposures than reported in non-pregnant controls. Bedaquiline concentrations in human milk were higher than maternal plasma (milk to maternal plasma ratio: 24:1). A single random plasma bedaquiline and M2 concentration was available in four infants (median age: 6.5 weeks): concentrations in the one breastfed infant were similar to maternal plasma concentrations; concentrations in the three non-breastfed infants were detectable but lower than maternal plasma concentrations. Conclusion We report low exposure of bedaquiline in pregnant women treated for rifampicin-resistant TB. Bedaquiline significantly accumulates in human milk; breastfed infants receive mg/kg doses of bedaquiline equivalent to maternal doses.

A robust analytical method based on liquid chromatography coupled to tandem mass spectrometry was developed and validated to quantify rifapentine and 25-O-desacetyl rifapentine in human breast milk to aid in determining the breastfed infant risk to the excreted drug in human milk. Samples were extracted by a combination of protein precipitation and solid phase extraction using rifampicin-d3 as an internal standard. An Agilent® Poroshell 120 EC-C18 (4.6 mm × 50 mm, 2.7 µm) column was used for chromatographic separation employing an isocratic mobile phase consisting of acetonitrile: methanol: 0.1% formic acid (55/5/40, v/v/v) at a flow rate of 450 µL/min, and with a total run time of four minutes. Mass detection was on an AB Sciex API 4000 mass spectrometer using electrospray ionization in the positive mode and based on multiple reaction monitoring data acquisition. Rifapentine was accurately quantified across a concentration range of 2.00-2000 ng/mL and 25-O-desacetyl rifapentine from 4.00 to 2000 ng/mL. During validation, the inter- and intra-day accuracy and precision at the tested QC concentrations (N = 18) for rifapentine were between 97.4% and 100.6%, and 3.1% and 8.3%, respectively. The inter- and intra-day accuracy and precision for 25-O-desacetyl rifapentine were between 96.4% and 106.3%, and 6.7% and 11.8%, respectively. No significant matrix effects were observed, and the method was shown to be specific for rifapentine and 25-O-desacetyl rifapentine. Human milk samples (N = 22) generated during a phase I/II clinical trial were successfully analysed for rifapentine and 25-O-desacetyl rifapentine using this validated method. Concentrations for rifapentine and 25-O-desacetyl rifapentine in human milk samples (N = 22) ranged from 11.2-1180 ng/mL and 7.11-573 ng/mL, respectively.