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Inhaled Pyrazinoic Acid Esters for the Treatment of Tuberculosis



Analog development of existing drugs and direct drug delivery to the lungs by inhalation as treatments for multiple and extensively drug resistant (MDR and XDR) tuberculosis (TB) represent new therapeutic strategies. Pyrazinamide (PZA) is critical to drug sensitive TB therapy and is included in regimens for MDR TB. However, PZA-resistant Mycobacterium tuberculosis (Mtb) strains threaten its use. Pyrazinoic acid esters (PAEs) are PZA analogs effective against Mtb in vitro, including against the most common PZA resistant strains. However, PAEs require testing for TB efficacy in animal models.


PAEs were delivered daily as aqueous dispersions from a vibrating mesh nebulizer to Mtb infected guinea pigs for 4 weeks in a regimen including orally administered first-line TB drugs.


PAEs tested as a supplement to oral therapy significantly reduced the organ bacterial burden in comparison to infected, untreated control animals. Thus, PAE aerosol therapy is a potentially significant addition to the regimen for PZA resistant MDR-TB and XDR-TB treatment. Interestingly, low dose oral PZA treatment combined with standard therapy also reduced bacterial burden. This observation may be important for PZA susceptible disease treatment.


The present study justifies further evaluation of PZA analogs and their lung delivery to treat TB.

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Colony forming units




Multiple drug resistant


Mass median aerodynamic diameter

Mtb :

Mycobacterium tuberculosis


Pyrazinoic acid esters


Polydispersity index


Pyrazinoic acid








Extensively drug resistant


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Funded by AIDS Clinical Trials Group (ACTG) UM1 AI068636, DAIDS, NIAID, co-principal investigators Dr. Miriam Braunstein and Dr. Anthony J. Hickey. We appreciate statistical support provided by Dr. Feng-Chang Lin of the NC-TraCS Biostats core.

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Correspondence to Miriam S. Braunstein or Anthony J. Hickey.

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Supplemental Figure 1S

Mean body weight of guinea pig groups at the start and end of the drug treatment period in A) study 1 and B) study 2. * p < 0.01 comparing starting and ending mean weight for groups of animals using Student’s t-test. Error bars represent standard deviation of the mean. (GIF 78 kb)

Supplemental Figure 2S

Organ weight from efficacy study 1. Groups of six guinea pigs were infected with Mycobacterium tuberculosis for 28 days then treated daily for 28 days with oral rifampicin and isoniazid (RH) alone or in combination with aerosolized PAE1 (2–4 mg/kg), aerosolized PAE2 (2–4 mg/kg), oral PZA5 (5 mg/kg), or oral PZA25 (25 mg/kg). After one month of treatment, lungs (A), spleen (B), and mediastinal lymph nodes (C) were collected and weighed. Relative organ weights for each animal are plotted (g organ weight/100 gram body weight). *p < 0.05, **p < 0.01, ***p < 0.001 using one-way ANOVA with Dunnett’s post test in comparison to the untreated group. Error bars represent standard deviation of the mean. (GIF 113 kb)

Supplemental Figure 3S

Organ weight from efficacy study 2. Groups of six guinea pigs were infected with Mycobacterium tuberculosis for 28 days then treated daily for 28 days with oral rifampicin (R) alone or in combination with aerosolized PAE1 (2–4 mg/kg), aerosolized PAE3 (2–4 mg/kg), oral PZA25 (25 mg/kg) or oral PZA300 (300 mg/kg). After one month of treatment, lungs (A), spleen (B), and mediastinal lymph nodes (C) were collected and weighed. Relative organ weights for each animal are plotted (g organ weight/100 gram body weight). *p <0.05, **p <0.01 using one-way ANOVA with Dunnett’s post test in comparison to the untreated group. Error bars represent standard deviation of the mean. (GIF 105 kb)

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Young, E.F., Perkowski, E., Malik, S. et al. Inhaled Pyrazinoic Acid Esters for the Treatment of Tuberculosis. Pharm Res 33, 2495–2505 (2016). https://doi.org/10.1007/s11095-016-1974-5

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  • inhaled therapy
  • pyrazinoic acid
  • pyrazinoic acid esters
  • TB drugs
  • tuberculosis