In Vitro Susceptibility Testing of a Novel Benzimidazole, SPR719, Against Nontuberculous Mycobacteria [Susceptibility]

Nontuberculous mycobacteria (NTM) infections are increasing globally. Mycobacterium avium complex (MAC) and M. abscessus are the most frequently encountered NTM among clinical laboratories, and treatment options are extremely limited. In this study, the in vitro potency of a novel benzimidazole, SPR719, the microbiologically active form of the orally available prodrug SPR720, was tested against several species of NTM.

MICs were performed on 161 isolates of NTM of 13 taxa (seven species, three subspecies and three groups/complexes) in cation adjusted Mueller Hinton Broth as described and recommended by the Clinical and Laboratory Standards Institute (CLSI M24-A2). Comparator antimicrobials included amikacin, cefoxitin, ciprofloxacin, clarithromycin, doxycycline, imipenem, linezolid, minocycline, moxifloxacin, tigecycline, and trimethoprim/sulfamethoxazole (TMP/SMX) for the rapidly growing species (RGM); amikacin and clarithromycin for the MAC; amikacin, ciprofloxacin, clarithromycin, doxycycline, linezolid, moxifloxacin, rifabutin, rifampin and TMP/SMX for the other slowly growing NTM. SPR719 was found to be potent against multiple clinical strains of NTM with an MIC₅₀ range of 0.25 – 4 μg/mL for several species of NTM. These findings support the further advancement of SPR720 for the treatment of NTM disease.

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