KL1333 hydrochloride is an orally effective NAD+ modulator that acts as a substrate for NAD(P)H: quinone oxidoreductase 1 (NQO1), leading to increased intracellular NAD+ levels through NADH oxidation. Elevated NAD+ subsequently activates SIRT1 and AMPK, which in turn activate PGC-1α. KL1333 hydrochloride improves energy metabolism and mitochondrial dysfunction in fibroblasts of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). It also has a protective effect against cisplatin-induced ototoxicity in cultured mouse cochlea.