Structure-based design of haloperidol analogues as inhibitors of acetyltransferase Eis from <i>Mycobacterium tuberculosis</i> to overcome kanamycin resistance.
Punetha A, Green KD, Garzan A, Thamban Chandrika N, Willby MJ, Pang AH, Hou C, Holbrook SYL, Krieger K, Posey JE, Parish T, Tsodikov OV, Garneau-Tsodikova S.
Tuberculosis (TB), caused by <i>Mycobacterium tuberculosis</i> (<i>Mtb</i>), is a deadly bacterial disease. Drug-resistant strains of <i>Mtb</i> make eradication of TB a daunting task. Overexpression of the enhanced intracellular survival (Eis) protein by <i>Mtb</i> confers resistance to the second-line antibiotic kanamycin (KAN). Eis is an acetyltransferase that acetylates KAN, inactivating its antimicrobial function. Development of Eis inhibitors as KAN adjuvant therapeutics is an attractive path to forestall and overcome KAN resistance. We discovered that an antipsychotic drug, haloperidol (HPD, <b>1</b>), was a potent Eis inhibitor with IC<sub>50</sub> = 0.39 ± 0.08 μM. We determined the crystal structure of the Eis-haloperidol (<b>1</b>) complex, which guided synthesis of 34 analogues. The structure-activity relationship study showed that in addition to haloperidol (<b>1</b>), eight analogues, some of which were smaller than <b>1</b>, potently inhibited Eis (IC<sub>50</sub> ≤ 1 μM). Crystal structures of Eis in complexes with three potent analogues and droperidol (DPD), an antiemetic and antipsychotic, were determined. Three compounds partially restored KAN sensitivity of a KAN-resistant <i>Mtb</i> strain K204 overexpressing Eis. The Eis inhibitors generally did not exhibit cytotoxicity against mammalian cells. All tested compounds were modestly metabolically stable in human liver microsomes, exhibiting 30-60% metabolism over the course of the assay. While direct repurposing of haloperidol as an anti-TB agent is unlikely due to its neurotoxicity, this study reveals potential approaches to modifying this chemical scaffold to minimize toxicity and improve metabolic stability, while preserving potent Eis inhibition.