Tuberculosis is a serious global health threat for which new treatments are urgently needed. This study examined the safety, tolerability, pharmacokinetics, and pharmacodynamics of multiple ascending doses of the
oxazolidinone PNU-100480 in healthy volunteers, using
biomarkers for safety and efficacy. Subjects were randomly assigned to
PNU-100480 or placebo (4:1) at schedules of 100, 300, or 600 mg twice daily or 1,200 mg daily for 14 days or a schedule of 600 mg twice daily for 28 days to which
pyrazinamide was added on days 27 and 28. A sixth cohort was given
linezolid at 300 mg daily for 4 days. Signs, symptoms, and routine safety tests were monitored. Bactericidal activity against Mycobacterium tuberculosis was measured in ex vivo whole-blood culture. Plasma
drug and metabolite concentrations were compared to the levels required for inhibition of M.
tuberculosis growth and 50% inhibition of
mitochondrial protein synthesis. All doses were safe and well tolerated. There were no hematologic or other safety signals during 28 days of dosing at 600 mg twice daily. Plasma concentrations of
PNU-100480 and metabolites at this dose remained below those required for 50% inhibition of
mitochondrial protein synthesis. Cumulative whole-blood bactericidal activity of
PNU-100480 at this dose (-0.316 ± 0.04 log) was superior to the activities of all other doses tested (P < 0.001) and was significantly augmented by
pyrazinamide (-0.420 ± 0.06 log) (P = 0.002). In conclusion,
PNU-100480 was safe and well tolerated at all tested doses. Further studies in patients with
tuberculosis are warranted.
Biomarkers can accelerate early development of new
tuberculosis treatments.