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J Antimicrob Chemother. 2005 Nov;56(5):968-74. Epub 2005 Sep 19.

Identification of a new antitubercular drug candidate, SQ109, from a combinatorial library of 1,2-ethylenediamines.

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  • 1Sequella, Inc., 9610 Medical Center Drive, Suite 200, Rockville, MD 20850, USA.



The aim of this study was to identify a candidate drug for clinical development from a previously synthesized combinatorial library based on the 1,2-ethylenediamine structure of ethambutol.


Sixty-nine of the most potent hits against Mycobacterium tuberculosis from the original studies were subjected to a sequential set of tests in vitro and in vivo--determination of MIC for M. tuberculosis H37Rv, cytotoxicity, intracellular antimycobacterial activity, permeability evaluation and in vivo efficacy testing.


Twenty-seven compounds with MICs of < or = 15.6 microM were tested on Vero cells to determine in vitro cytotoxicity (IC50) and to establish a selectivity index (SI) (SI = IC50/MIC). Ten compounds with acceptable SI were tested for activity against intracellular bacteria--all were equivalent (within 1%) or superior to ethambutol and several demonstrated cidal activity. Five of the most potent compounds were tested for in vivo efficacy in a murine model of chronic tuberculosis infection.


Compound SQ109 with an MIC of 0.7-1.56 microM (H37Rv, Erdman and drug-resistant strains of M. tuberculosis), an SI of 16.7 and 99% inhibition activity against intracellular bacteria, demonstrated potency in vivo and limited toxicity in vitro and in vivo, and was selected for further development.

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