Clofazimine, one of the riminophenazine class drugs, is effective in treating the mycobacterial infection Hansen’s disease (also known as leprosy). Clofazimine and other compounds of this class demonstrate impressive bactericidal and sterilizing efficacy against TB in vitro and in mouse models of the disease. Although its efficacy against TB is promising, clofazimine has poor solubility and a bright red color, its extremely long half-life leading to high accumulation of the drug in tissues of patients with consequent side effects including pronounced skin discoloration. TB Alliance has pursued compounds that mirror clofazimine’s potential as an anti-TB drug while possessing a superior side effect profile. TBI-166 was identified through a lead optimization effort by TB Alliance in partnership with the Institute of Materia Medica, Chinese Academy of Medical Sciences & Peking Union Medical College (IMM, CAMS & PUMC) in Beijing to identify a riminophenazine compound with improved physicochemical and pharmacokinetic properties that will avoid discoloration of the skin, but fight TB with efficacy similar to clofazimine. Following preliminary evaluations of pharmacokinetics and toxicity and extensive evaluations of efficacy, TBI-166 was selected as a preclinical development candidate. Supported by China National Science & Technology Major Project Grant and Beijing Municipal Science & Technology Commission Grant, IMM, in collaboration with its affiliated Beijing Union Second Pharmaceutical Factory, has completed preclinical development of TBI-166 and filed Clinical Trial Application to Chinese FDA in 2015, which was approved in November 2016. The Phase I clinical trial was started in January 2018.