“Green” cyclodextrin-based nanoparticles for tuberculosis treatment – ANTI-TB-NANO

A series of nanoparticles able to (co)encapsulate synergic drugs (ethionamide and its booster) have been prepared. Advantageously, some of these nanocarriers can be synthesized in the absence of organic solvents. Moreover, drug encapsulation can be acheived by a «green« technology devois of organic solvent with potential toxic effects. Studies are underway to achieve biomimentic coatings.
An automatised method has been set up to stud the efficacy of the drug-loaded nanoparticles to kill intracellular Mtb. This method is based on confocal microscopy (Opera Phenix HCS, Perkin Elmer).

First in vivo data are promissing, showing the efficacy of nanoparticles to reduce bacterial loads in a model of infected mice. The nanoparticles allowed administering the drugs, with very low solubilities in aqueous media. Noteworthy, the direct administration of the nanoparticles in the lungs of infected mice allowed reducing the Mtb loads.

Studies are underway to optimise the systems and to decipher the intracellular fate of the nanoparticles.

C. Ladavière, R. Gref, Nanomedicine, 10 (19), 3033-3055, (2015) «Toward an optimized treatment of intracellular bacterial infections: input of nanoparticulate drug delivery systems.«

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis (Mtb) that still results in more than one million deaths annually despite numerous control programs. Increasing numbers of drug resistant cases are being reported each year. Almost 90% of all TB cases are highly contagious pulmonary cases, putting at risk families and medical staff. Mtb is able to survive and replicate within macrophages (professional phagocytic cells) despite their internal unfavorable microenvironment.
A promising approach is to develop efficient drug nanocarriers that would target Mtb localized in the infected macrophages within the lungs. However, the current TB regimens include anti-TB agents that, despite their strong activity against the bacterium per se, penetrate poorly into the infected macrophages. To increase the efficacy of ethionamide (ETH), a second-line anti-TB drug, and reduce the administered doses, partner 3 (IPL) has discovered a potent association with a family of molecules, called “boosters”. This association enables to reduce the amount of administered drugs and associated side effects. An industrial consortium (Bioversys, TB-Alliance and GSK) has signed an agreement with IPL to initiate the clinical trials for the ETH/booster pair. However, the in vivo co-administration of these two drugs is very challenging, because of their totally different solubilities, bioavailabilities and in vivo fate.
ANTI-TB-NANO proposes an original approach consisting in optimizing the TB treatment using the novel ETH/booster pair, by (co)encapsulation in engineered nanoparticles targeting Mtb in alveolar macrophages. The nanoparticles would efficiently co-encapsulate ETH/booster pair at precise molar ratios, protect the drugs towards inactivation and release them inside the infected macrophages.
The five interdisciplinary teams in ANTI-TB-NANO will combine their complementary expertise to design, synthesize and evaluate both in vitro and in vivo optimized drug-loaded nanoparticles. Based on our promising preliminary data, the nanoparticles will be made of cyclodextrins (CDs) with strong affinity for both ETH and its booster. The CD-nanoparticles allow efficient encapsulation by a “green” procedure (no solvent, no surfactant). The nanoparticle surface will be coated with lipids and ligands to enhance macrophage internalization to track Mtb in its hideouts. Besides, the coating should avoid drug leakage before reaching the target.
A main innovation in ANTI-TB-NANO will be the first use of high content screening (advanced confocal fluorescence-based imaging method) to simultaneously investigate the fate of the nanoparticles and living bacteria inside the living macrophages. We expect to obtain crucial information concerning the antibacterial efficacies of the drug-loaded nanoparticles, as well as their mechanisms of cell penetration, location in sub-cellular compartments and toxicities. Eventually, the efficacy of the best formulations will be assayed in a mouse model of Mtb infection.
The optimized drug nanocarriers will be aerosolized in the lungs to primarily target infected pulmonary macrophages, to rapidly increase the bacterial clearance, reduce the risk of resistance and allow a more rapid evolution to a non-infective status and a decrease of undesirable side effects and toxic issues.
Optimized delivery of ETH/booster to infected macrophages should help reducing drug dosage to improve tolerability and patient compliance. It will pave the way towards improving drug efficacy, potentially allowing destruction of latent bacteria, and thus reducing risks of acquired resistance. Our approach also applies for other anti-TB drugs such as isoniazid, rifampicin, pyrazinamide, ethambutol and fluoroquinolones. ANTI-TB-NANO aims to develop a new concept of drug therapy to efficiently chase Mtb, reduce contagiousness rapidly after TB diagnosis, limit treatment side effects, and ultimately combat innate and acquired drug resistance.