Activity of PNU and its major metabolite in whole blood and broth culture models of TB

Transcription

1 Activity of PNU and its major metabolite in whole blood and broth culture models of TB Paul Converse 1, Jin Lee 1, Kathy Williams 1, Opokua Amoabeng 1, Kim Dionne 1, Nicole Parish 1, Robert Wallis 2, Eric Nuermberger 1 1 Center for Tuberculosis Research, Johns Hopkins University, Baltimore, MD 2 Pfizer Inc., Groton, CT

2 PNU Thiomorpholinyl derivative of linezolid In vitro: MIC = 0.25 μg/ml vs. M. tb H37Rv In vivo: Rapidly metabolized to cmpds with ~ same MIC as parent

3 Dose ranging activity of PNU, LZD in mice Lung log10 CFU count Dose (mg/kg) D0 count = 7.49 INH PNU Linezolid Parameter Regimen MIC (mg/l) C max (mg/l) AUC 0-24 (mg-h/l) PNU metab mg/kg a LZD 130 mg/kg b a Compiled (i.e., sum of the parent + metab) concentration-time profile used for PK calcs. b For comparison, steady state values in humans are: C max, mg/l; AUC 0-24, mg-h/l Williams et al, AAC (2009);53:1314

4 PNU contributes sterilizing activity to RHZ and novel combinations Proportion (%) of mice with relapse after treatment for: Regimen* 3 months 4 months 5 months 6 months 2RHZ + 4RH 18 of 20 (90%) 1 of 20 (5%) 0 of 20 (0%) 2RHZU + 2 RHU 9 of 20 (45%) 1 of 20 (5%)** 2RHZL + 2 RHL 20 of 20 (100%) *R = rifampin, H = isoniazid, Z = pyrazinamide, U= PNU (sutezolid), L = linezolid **p< vs. RHZ/RH control % (proportion) of mice with relapse after treatment for: Regimen* 2 months 3 months 4 months 2RHZ/4RH 100% (15/15) 64% (9/14) JCPaU 93% (14/15) 13% (2/15)** 7% (1/15)* JCPa 100% (15/15) 60% (9 /15) 33% (5/15) *R = rifampin, H = isoniazid, Z = pyrazinamide, U= PNU (sutezolid), J = bedaquiline, C = clofazimine, Pa = PA-824 **p< 0.05 vs. RHZ/RH control Williams et al, Am J Respir Crit Care Med 2009 Williams et al, Antimicrob Agent Chemother 2012

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6 Objectives of study To gain insight into why PNU is more bactericidal than LZD despite achieving lower exposures in mice by: 1. Comparing the concentration response profile for LZD and PNU in several in vitro models of: extracellular infection (broth, plasma), and intracellular infection (WBA, J774 macrophages) 2. Determining the respective contributions of PNU (the parent) and PNU (the principal metabolite) in the same assays

7 Time to positivity in WB cultures

8 Whole blood activity by calculated log kill

9 WBA of PNU and PNU

10 Oxie activity in spiked WB or plasma from healthy volunteers

11 Time kill study in complete 7H9 broth

12 Time kill study in J774 macrophages

13 Modeling the respective contributions of PNU 480 and 603 in humans Developed dose response curve for each in vitro model Used plasma PK profiles from Ph I SAD study to estimate the log CFU ct at each point of sampling Using control CFU cts (Time 0 or untreated), calculated the area under the 24 hr killing (or inhibition) curve for a single 1 g daily dose for each cmpd Assumed additivity (based on in vitro checkerboard assay) and calculated the contribution of each cmpd to the overall activity of the combination

14 Cumulative activity over 24 hrs by model

15 Conclusions In vivo activity of PNU likely derives from the combined activity of the parent and the sulfoxide metabolite Though the metabolite comprises ~85% of total serum AUC, the parent drives the activity against intracellular bacilli (e.g., WBA, J774, mice?) due to its striking potency advantage On the other hand, activity vs. extracellular M.tb may be driven by the more abundant metabolite Modeling cell kill based on actual CFU from WB or plasma culture gives results more like human EBA The potency advantage of PNU over linezolid will likely be smaller against extracellular as opposed to intracellular bacilli

16 Next steps Similar analysis for linezolid Repeat WBA CFU cts using additional volunteers More sophisticated models of additive oxie effects, using steady state PK data from humans and mice Confirm with one or more additional strains

17 Acknowledgements The work Kathy Williams Paul Converse Opokua Amoabeng Intellectual support Rokeya Tasneen Jin Lee Tong Zhu Ken Stover Bob Wallis Steve Brickner Mark Mitton-Fry Colleagues at the TB Alliance Funding support Pfizer, NIH (R01-AI )