Dry powder Inhalation of lytic mycobacteriophages for adjunct therapy in a mouse model of infection with Mycobacteriumtuberculosis

Inhaled therapy of tuberculosis (TB) by a Dry Powder Inhalation (DPI) comprising mycobacteriophage D29 and TM4 was non-inferior to oral anti-tuberculosis therapy (ATT) with isoniazid and rifampicin in a mouse model of infection with Mycobacterium tuberculosis (Mtb). No pharmaceutical phage product of mycobacteriophages is approved for large-scale production. We scaled up preparation and downstream processing of phages, developed DPI formulations, and established methods for determining identity, purity, assay, stability, and critical quality attributes (CQA). We carried out cell-based assays of intracellular bactericidal activity and pharmacokinetics and comparative efficacy in Mtb-infected mice. Daily doses of the DPI containing ∼1010 Plaque Forming Units/dose DPI reduced Mtb colony forming units (CFU) in the lungs from 6.4 ± 0.3-log to 4.8 ± 0.7-log in four weeks, while oral human equivalent doses (HED) of isoniazid and rifampicin reduced CFU to 3.8 ± 0.8-log. Combining inhaled phages with oral drugs sterilized the lungs of one of four mice and reduced group mean CFU to 2.3-log. Inhalations significantly upregulated tumor necrosis factor (TNF) in lung tissue to ∼1500 pg/ml of homogenate, improved organ morphology, and reduced histopathology. The HD DPI may be a useful adjunct to oral drugs. Dose-finding animal efficacy studies are required before assessing preclinical safety.

Inhalable particles containing isoniazid and rifabutin as adjunct therapy for safe, efficacious and relapse-free cure of experimental animal tuberculosis in one month

We investigated the preclinical efficacy and safety/tolerability of biodegradable polymeric particles containing isoniazid (INH) and rifabutin (RFB) dry powder for inhalation (DPI) as an adjunct to oral first-line therapy. Mice and guinea pigs infected with Mycobacterium tuberculosis H37Rv (Mtb) were treated with ∼80 and ∼300 μg of the DPI, respectively, for 3-4 weeks starting 3, 10, and 30 days post-infection. Adjunct combination therapy eliminated culturable Mtb from the lungs and spleens of all but one of 52 animals that received the DPI. Relapse-free cure was not achieved in one mouse that received DPI + oral, human-equivalent doses (HED) of four drugs used in the Directly Observed Treatment, Short Course (DOTS), starting 30 days post-infection. Oral doses (20 mg/Kg/day, each) of INH + RFB reduced Mtb burden from ∼10⁶ to ∼10³ colony-forming units. Combining half the oral dose with DPI prevented relapse of infection four weeks after stopping the treatment. The DPI was safe in rodents, guinea pigs, and monkeys at 1, 10, and 100 μg/day doses over 90 days. In conclusion, we show the efficacy and safety/tolerability of the DPI as an adjunct to oral chemotherapy in three different animal models of TB.

An update on the use of rifapentine for tuberculosis therapy

INTRODUCTION

Tuberculosis (TB) remains rampant throughout the world, in large part due to the lengthy treatment times of current therapeutic options. Rifapentine, a rifamycin antibiotic, is currently approved for intermittent dosing in the treatment of TB. Recent animal studies have shown that more frequent administration of rifapentine could shorten treatment times, for both latent and active TB infection. However, these results were not replicated in a subsequent human clinical trial.

AREAS COVERED

This review analyses the evidence for more frequent administration of rifapentine and the reasons for the apparent lack of efficacy in shortening treatment times in human patients. Inhaled delivery is discussed as a potential option to achieve the therapeutic effect of rifapentine by overcoming the barriers associated with oral administration of this drug. Avenues for developing an inhalable form of rifapentine are also presented.

EXPERT OPINION

Rifapentine is a promising active pharmaceutical ingredient with potential to accelerate treatment of TB if delivered by inhaled administration. Progression of current fundamental work on inhaled anti-tubercular therapies to human clinical trials is essential for determining their role in future treatment regimens. While the ultimate goal for global TB control is a vaccine, a short and effective treatment option is equally crucial.

HLA-DRB1*1501 and VDR polymorphisms and survival of Mycobacterium tuberculosis in human macrophages exposed to inhalable microparticles

AIM

We examined whether HLA-DRB1*1501 and four VDR SNPs influence the macrophage response to infection with Mycobacterium tuberculosis (Mtb) via innate immune versus drug treatment or drug delivery mechanisms.

MATERIALS & METHODS

Monocyte-derived macrophages from 24 healthy donors were infected with Mtb in vitro. Survival of intracellular bacilli and secretion of cytokines and nitric oxide by the infected cells were monitored with and without exposure to isoniazid and rifabutin.

RESULTS

Haplotype analysis was conducted, and an arbitrary score of genetic 'susceptibility' (S ) score ranging from -3 to +3 was assigned to donors based on the presence or absence of genetic markers. S scores correlated more strongly with Mtb survival (r = 0.68) than TNF and nitric oxide (NO; r = ∼0.01-0.11). A specific haplotype was significantly associated with decreased Mtb survival (p < 0.05), increased NO and decreased IL-10/IL-4. Macrophages with S scores ≥ 2 secreted significantly (p < 0.05) more IL-10 and IL-4, and less NO upon infection, and supported Mtb survival. Microparticulate drugs showed higher bactericidal activity than free drugs, irrespective of S score.

CONCLUSION

S score predicts colonization of macrophages by Mtb, as does haplotype analysis. Drug-containing microparticles are superior to free drugs across diverse genetic backgrounds.

Isoniazid-gelatin conjugate microparticles containing rifampicin for the treatment of tuberculosis

Objectives 

In this work, a new polymeric microparticle system based on gelatin covalently bound to isoniazid (ISN) and containing rifampicin (RFP) was prepared by spray-drying technique. Microparticle aptitude to nebulisation and their capability of interacting with A549, alveolar basal epithelial cells, were evaluated in vitro.

Methods

Microparticles were obtained by spray drying, and their morphology, size, zeta potential, thermotropic behaviour and nebulisation ability were evaluated.

Key findings 

Microparticles were positively charged with a mean size of 4.88 ± 0.3 μm. Microspheres were able to incorporate both RFP and ISN: encapsulation efficiency was 51 ± 6% and 22 ± 1%, respectively. X-ray diffraction study showed a new extensive and flattened diffraction peak providing evidence that the drugs were dispersed into the microparticles. Differential scanning calorimetry analysis confirmed effective interactions between gelatin and drug molecules by the presence of new transition peaks. Fifty-nine per cent of used microparticles were aerosolised. In-vitro toxicity studies on A549 alveolar basal epithelial cells showed that microparticles decreased cytotoxicity in comparison with the RFP solution. Laser scanning confocal microscopy observation confirmed that fluorescent probes delivered by microparticles are efficiently internalised in A549 cells.

Conclusions 

Overall, microparticles based on gelatin covalently bound to ISN and containing RFP showed a promising behaviour for pulmonary drug delivery.

Composition influence on pulmonary delivery of rifampicin liposomes

The effects of lipid concentration and composition on the physicochemical properties, aerosol performance and in vitro toxicity activity of several rifampicin-loaded liposomes were investigated. To this purpose, six liposome formulations containing different amounts of soy phosphatidylcholine and hydrogenated soy phosphatidylcholine, with and without cholesterol and oleic acid, were prepared and fully characterized. Uni- or oligo-lamellar, small (~100 nm), negatively charged (~60 mV) vesicles were obtained. Lipid composition affected aerosol delivery features of liposomal rifampicin; in particular, the highest phospholipid concentration led to a better packing of the vesicular bilayers with a consequent higher nebulization stability. The retention of drug in nebulized vesicles (NER%) was higher for oleic acid containing vesicles (55% ± 1.4%) than for the other samples (~47%). A549 cells were used to evaluate intracellular drug uptake and in vitro toxicity activity of rifampicin-loaded liposomes in comparison with the free drug. Cell toxicity was more evident when oleic acid containing liposomes were used.