Isoniazid-d4 (INH-d4) is the deuterium labeled Isoniazid. Isoniazid (INH) is a prodrug and must be activated by a bacterial catalase-peroxidase enzyme KatG. Isoniazid is bactericidal to rapidly dividing mycobacteria and has anti-tuberculostatic activity[1][2][3][4].

Stable heavy isotopes of hydrogen, carbon, and other elements have been incorporated into drug molecules, largely as tracers for quantitation during the drug development process. Deuteration has gained attention because of its potential to affect the pharmacokinetic and metabolic profiles of drugs[1].

[1]. Russak EM, et al. Impact of Deuterium Substitution on the Pharmacokinetics of Pharmaceuticals. Ann Pharmacother. 2019;53(2):211-216. [2]. Suarez, J., et al., An oxyferrous heme/protein-based radical intermediate is catalytically competent in the catalase reaction of Mycobacterium tuberculosis catalase-peroxidase (KatG). J Biol Chem, 2009. 284(11): p. 7017-29.
[3]. Timmins, G.S., et al., Nitric oxide generated from isoniazid activation by KatG: source of nitric oxide and activity against Mycobacterium tuberculosis. Antimicrob Agents Chemother, 2004. 48(8): p. 3006-9.
[4]. Singh, R., et al., PA-824 kills nonreplicating Mycobacterium tuberculosis by intracellular NO release. Science, 2008. 322(5906): p. 1392-5.
[5]. Ahmad, Z., et al., Biphasic kill curve of isoniazid reveals the presence of drug-tolerant, not drug-resistant, Mycobacterium tuberculosis in the guinea pig. J Infect Dis, 2009. 200(7): p. 1136-43.