Rapid Evaluation in Whole Blood Culture of Regimens for XDR-TB Containing PNU-100480 (Sutezolid), TMC207, PA-824, SQ109, and Pyrazinamide

There presently is no rapid method to assess the bactericidal activity of new regimens for tuberculosis. This study examined PNU-100480, TMC207, PA-824, SQ109, and pyrazinamide, singly and in various combinations, against intracellular M. tuberculosis, using whole blood culture (WBA). The addition of 1,25-dihydroxy vitamin D facilitated detection of the activity of TMC207 in the 3-day cultures. Pyrazinamide failed to show significant activity against a PZA-resistant strain (M. bovis BCG), and was not further considered. Low, mid, and high therapeutic concentrations of each remaining drug were tested individually and in a paired checkerboard fashion. Observed bactericidal activity was compared to that predicted by the sum of the effects of individual drugs. Combinations of PNU-100480, TMC207, and SQ109 were fully additive, whereas those including PA-824 were less than additive or antagonistic. The cumulative activities of 2, 3, and 4 drug combinations were predicted based on the observed concentration-activity relationship, published pharmacokinetic data, and, for PNU-100480, published WBA data after oral dosing. The most active regimens, including PNU-100480, TMC207, and SQ109, were predicted to have cumulative activity comparable to standard TB therapy. Further testing of regimens including these compounds is warranted. Measurement of whole blood bactericidal activity can accelerate the development of novel TB regimens

Biomarker-Assisted Dose Selection for Safety and Efficacy in Early Development of PNU-100480 for Tuberculosis▿

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

Bactericidal activities of TMC207, PNU-1004800, rifampin (RIF), isoniazid (INH), and pyrazinamide (PZA), against intracellular <i>M. tuberculosis</i> in sealed whole blood cultures differing according to duration, air space, and addition of dihydroxy-vitamin D.

<p>Negative values indicate killing.</p><p>*Results are carried over from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0030479#pone-0030479-g002" target="_blank">figure 2</a>.</p

Process for calculating cumulative whole blood bactericidal activity (WBA) of drug combinations.

<p>Process for calculating cumulative whole blood bactericidal activity (WBA) of drug combinations.</p

Predicted whole blood bactericidal activity of TMC207 (J, bedaquiline) 400 mg QD and 200 mg TIW, and PNU-100480 (U, sutezolid) 600 mg BID, singly and together.

<p>Predicted whole blood bactericidal activity of TMC207 (J, bedaquiline) 400 mg QD and 200 mg TIW, and PNU-100480 (U, sutezolid) 600 mg BID, singly and together.</p

Predicted cumulative whole blood bactericidal activity of single drugs and multi-drug combinations against <i>M. tuberculosis</i>, based on published pharmacokinetic data, and the concentration-activity relationships and drug-drug pharmacodynamic interactions in figure 2.

<p>Drugs were tested by direct adding drugs directly to whole blood cultures of healthy volunteers except for: * drugs were administered orally; ⁺ subjects were TB patients. U = PNU-100480 600 mg BID; J = TMC207; Pa = PA-824; H = isoniazid; R = rifampin; E = ethambutol; Z = pyrazinamide; L = levofloxacin. The combination of PNU-100480, SQ109, and TMC207 400 mg QD was the most active of those tested.</p

Effects of substituting regression analysis for point-to-point interpolation in calculating Δ log CFU from time to positivity (TTP) in mycobacterial growth indicator tubes (MGIT).

<p>The left panel indicates the accuracy of curve fitting (the relationship between observed and predicted values). The right panel compares the results of the two methods (regression vs. interpolation).</p