Pharmacokinetics and target attainment of SQ109 in plasma and human-like tuberculosis lesions in rabbits

Oluwaseun Egbelowo, Jansy P. Sarathy, Kamunkhwala Gausi, Matthew D. Zimmerman, Han Wang, Gert Jan Wijnant, Firat Kay, Martin Gengenbacher, Nhi Van, Yonatan Degefu, Carol Nacy, Bree B. Aldridge, Claire L. Carter, Paolo Denti, Véronique Dartois

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


SQ109 is a novel well-tolerated drug candidate in clinical development for the treatment of drug-resistant tuberculosis (TB). It is the only inhibitor of the MmpL3 mycolic acid transporter in clinical development. No SQ109-resistant mutant has been directly isolated thus far in vitro, in mice, or in patients, which is tentatively attributed to its multiple targets. It is considered a potential replacement for poorly tolerated components of multidrug- resistant TB regimens. To prioritize SQ109-containing combinations with the best potential for cure and treatment shortening, one must understand its contribution against different bacterial populations in pulmonary lesions. Here, we have characterized the pharmacokinetics of SQ109 in the rabbit model of active TB and its penetration at the sites of disease-lung tissue, cellular and necrotic lesions, and caseum. A two-compartment model with first-order absorption and elimination described the plasma pharmacokinetics. At the human-equivalent dose, parameter estimates fell within the ranges published for preclinical species. Tissue concentrations were modeled using an "effect"compartment, showing high accumulation in lung and cellular lesion areas with penetration coefficients in excess of 1,000 and lower passive diffusion in caseum after 7 daily doses. These results, together with the hydrophobic nature and high nonspecific caseum binding of SQ109, suggest that multiweek dosing would be required to reach steady state in caseum and poorly vascularized compartments, similar to bedaquiline. Linking lesion pharmacokinetics to SQ109 potency in assays against replicating, nonreplicating, and intracellular M. tuberculosis showed SQ109 concentrations markedly above pharmacokinetic-pharmacodynamic targets in lung and cellular lesions throughout the dosing interval.

Original languageEnglish (US)
Article numbere00024-21
JournalAntimicrobial agents and chemotherapy
Issue number9
StatePublished - Sep 2021

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases


  • Lesion penetration
  • MDR-TB
  • Mycobacterium tuberculosis
  • PK-PD
  • Pharmacokinetics
  • SQ109


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