Optimising pyrazinamide for the treatment of tuberculosis

Abstract

Pyrazinamide is a potent sterilising agent that shortens the treatment duration needed to cure tuberculosis. It is synergistic with novel and existing drugs for tuberculosis. The dose of pyrazinamide that optimises efficacy while remaining safe is uncertain, as is its potential role in shortening treatment duration further.

Pharmacokinetic data, sputum culture, and safety laboratory results were compiled from TBTC Studies 27 and 28 and PanACEA MAMS-TB, multi-center Phase 2 trials in which participants received rifampicin (range 10–35 mg·kg⁻¹), pyrazinamide (range 20–30 mg·kg⁻¹), plus two companion drugs. Pyrazinamide pharmacokinetic-pharmacodynamic (PK/PD) and PK-toxicity analyses were performed.

In TBTC studies (n=77), higher pyrazinamide maximum concentration (Cmax) was associated with shorter time to culture conversion (TTCC) and higher probability of two-month culture conversion (p-value<0.001). Parametric survival analyses showed that relationships varied geographically, with steeper PK-PD relationships seen among non-African than African participants. In PanACEA MAMS-TB (n=363), TTCC decreased as pyrazinamide Cmax increased and varied by rifampicin Cmax (p-value<0.01). Modeling and simulation suggested that very high doses of pyrazinamide (>4500 mg) or increasing both pyrazinamide and rifampicin would be required to reach targets associated with treatment shortening. Combining all trials, liver toxicity was rare (3.9% with Grade 3 or higher liver function tests, LFT), and no relationship was seen between pyrazinamide Cmax and LFT levels.

Pyrazinamide's microbiologic efficacy increases with increasing drug concentrations. Optimising pyrazinamide alone, though, is unlikely to be sufficient to allow tuberculosis treatment shortening; rather, rifampicin dose would need to be increased in parallel.