Thiazomycin, nocathiacin and analogs show strong activity against clinical strains of drug-resistant Mycobacterium tuberculosis

Thiazolyl peptides are a class of natural products with potent Gram-positive antibacterial activities. Lack of aqueous solubility precluded this class of compounds from advancing to clinical evaluations. Nocathiacins and thiazomycins are sub-classes of thiazolyl peptides that are endowed with structural features amenable for chemical modifications. Semi-synthetic modifications of nocathiacin led to a series of analogs with improved water solubility, while retaining potency and antibacterial spectrum. We studied the activities of a selection of two natural products (nocathiacin and thiazomycin) as well as seven polar semi-synthetic analogs against twenty clinical strains of Mycobacterium tuberculosis with MDR phenotypes. Two compounds show useful activity against H37Rv strain with MIC values ≤1 μM, two (≤0.5 μm) and three (≤10 μm). These two derivatives showed MIC values ≤2.5 μm against most of the 20 MDR strains regardless their resistance profile. Specifically, these lack cross-resistance to rifampicin, isoniazid and moxifloxacin.