The impact of PheroidTM technology on the bioavailability and efficacy of anti-tuberculosis drugs in an animal model

Abstract

Tuberculosis (TB) is a worldwide pandemic with vast challenges in the fight against the disease. Challenges include the long and tedious treatment regimens and chemotherapy with adverse side effects. One approach in defeating TB is to improve patient compliance to the treatment regimes. The Pheroid™ drug delivery system possesses characteristics and abilities to make it a good candidate to lower the dosage of the anti-TB actives; ethambutol (EMB), rifampicin (RMP), pyrazinamide (PZA) and isoniazid (INH). For the purpose of this study, the bioavailability of the anti-TB actives EMB, PZA, RMP and INH were determined in the mouse model. Plasma was collected from 8 mice per group over 4 hours and analysed by an independent laboratory. Area under the plasma curve, as a function of bioavailability, increased by 85.7% for EMB, 45.5% for INH and 33.2% for PZA with the Pheroid™ formulation when compared with the formulation currently prescribed. Although not significantly different, RMP also showed a 33.3% increase with the Pheroid™ formulation. Bioavailability decreased between 7% and 58% for EMB, INH, and PZA when the formulation currently prescribed is compared with the pro-Pheroid™ formulation, but RMP increased significantly by 84%. Efficacy of a Pheroid™ based formulation was compared to the free actives in the mouse model. Mice were inoculated with Mycobacterium tuberculosis H37Rv reference strain. Treatment started two weeks after inoculation and continued for 12 weeks with a 3 month post treatment observation period. Methods used to assess treatment efficacy were the Mycobacteria Growth Indicator Tubes (MGID method in parallel with a method counting colony forming units (CFU) on agar plates. According to the MGIT method, the Pheroid™ treatment is statistically more effective at week 4 by 10% and at week 10 by 9%. Although not statistically more efficient, the Pheroid™ based treatment is 16.7% more effective at 3 months post treatment. According to the agar plate method, the Pheroid™ treatment is statistically 7% more effective than the Free drug treatment at week 2. Although the two methods gave slightly different results, a trend in efficacy could be observed. The mice treated with the Pheroid™ formulations showed a significant improvement from onset of treatment to about week 10 (with the exception of week 6) and again at 3 months post treatment. The bioavailability and efficacy data accumulated in this study indicate that a new antituberculosis treatment regime based on the Pheroid™ drug delivery system opens the opportunity for a new dosage form where APls are either lowered, treatment time shortened or treatment intervals increased. TB patient compliance might be improved with such a new treatment regime while assisting in the fight against TB.