Therapeutic Efficacy of SQ641-NE against Mycobacterium tuberculosis

Abstract

A phospholipid-based nanoemulsion formulation of SQ641 (SQ641-NE) was active against intracellular Mycobacterium tuberculosis in J774A.1 mouse macrophages, although SQ641 by itself was not. Intravenous (i.v.) SQ641-NE was cleared from circulation and reached peak concentrations in lung and spleen in 1 h. In a murine tuberculosis (TB) model, 8 i.v. doses of SQ641-NE at 100 mg/kg of body weight over 4 weeks caused a 1.73 log 10 CFU reduction of M. tuberculosis in spleen and were generally bacteriostatic in lungs. C apuramycin (CM) is a novel nucleoside antibiotic that specifically inhibits biosynthesis of peptidoglycan (PG) by blocking the translocase I (TL1) enzyme (1-4). SQ641 is the most potent analogue in this series for in vitro activity against several species of mycobacteria (5-8). SQ641 is rapidly bactericidal for Mycobacterium tuberculosis and has a lasting postantibiotic effect (PAE). It is synergistic with ethambutol (EMB) and additive with isoniazid (INH) (8-10).Despite its excellent in vitro activity, SQ641 possesses several deficiencies that impair its therapeutic efficacy against tuberculosis (TB): it is poorly soluble in water and is not absorbed orally. As a result, it has poor intracellular and in vivo activity (11,12). To overcome these deficiencies, we earlier developed ␣-tocopheryl polyethylene glycol 1000 succinate (TPGS) soluble and micellar formulations of SQ641 (13,14). Even though these formulations demonstrated better intracellular and in vivo efficacy, both formulations suffer from low drug loading and are thus unsuitable for human use: too large a volume is needed to see efficacy. We developed a phospholipid-based nanoemulsion formulation that accommodates higher drug loading and is compatible for human use.Animal experiments were performed by Sequella personnel at BIOQUAL, Inc. (Rockville, MD), by Institutional Agreement and were performed according to guidelines of U.S. Government Policy on Care and Use of Laboratory Animals in biomedical research (assurance A2796.02).SQ641 was synthesized at Sequella, Inc., as described previously (7, 12). INH, EMB, rifampin (RIF), and pyrazinamide (PZA) were purchased from Sigma-Aldrich, St. Louis, MO. A phospholipid-based nanoemulsion formulation of SQ641 (SQ641-NE) was prepared in phospholipid Phosal 53 MCT (Lipoid GmbH, Ludwigshafen, Germany) using TPGS as the emulsifier and characterized as described previously (15). Intracellular activity of the compounds was determined by using the M. tuberculosis luciferase reporter H37Rv-pSMT1 strain and J77A.1 mouse macrophage cell line (14,16,17). In vivo efficacy of SQ641-NE was tested in a mouse model of TB infection (11) using a mousepassaged M. tuberculosis H37Rv (Pasteur) strain (kind gift of J. Marshal). C57BL/6 female mice (Charles River Laboratories, Raleigh, NC) were infected intravenously (i.v.) with 10 5 CFU H37Rv, and therapy was initiated 3 weeks later. SQ641-NE was administered i.v. 2 times/week or intraperitoneally (i.p.) 5 times/week for 4 weeks; INH was administered orally (p.o.) 5 times/...

New tuberculosis drug leads from naturally occurring compounds

“…38,39 In a mouse model of chronic M. tuberculosis infection, SQ641 was able to reduce bacterial lung burden by 1.0-1.5 log 10 CFU. 40 However, its lipophilicity and low water solubility has led to studies with delivery vehicles 41 as well as further chemical modifications to improve intracellular activity. 42 A capuramycin analogue, UT-01320, inhibits bacterial RNA polymerases and has been shown to work in synergy with SQ641 to inhibit M. tuberculosis H37Rv growth to a greater extent than each molecule alone.…”

Advances in nanotechnology-based carrier systems for targeted delivery of bioactive drug molecules with special emphasis on immunotherapy in drug resistant tuberculosis – a critical review

“…In general, emulsions are cloudy but the nanoemulsions have translucent and clear appearance. Nikonenko et al (2014) developed phospholipid-based nanoemulsion system of SQ-641-NE which was found to be active against Mycobacterium tuberculosis. Different examples of antitubercular drug loaded emulsion systems are given in Table 3.…”

Self-Nano-Emulsifying Drug-Delivery Systems: From the Development to the Current Applications and Challenges in Oral Drug Delivery

“…Surface-modified nano-emulsions have been developed to reach animals and human liver in a similar way to chylomicrons [ 314 , 315 ]. SNEDDSs can drastically increase the concentration of the drug in liver and/or spleen and can be a smart way to reach these organs [ 316 , 317 , 318 ].…”