Oltipraz is a synthetic, substituted 1,2-dithiole-3-thione originally used in humans as an antischistosomal agent. Animal studies have demonstrated that oltipraz is a potent inducer of Phase II detoxification enzymes, most notably glutathione-S-transferase (GST).

In vitro: Oltipraz has been classified as a monofunctional inducer since it advantageously elevates Phase II detoxification enzymes, while only slightly altering the expression of the Phase I “activating” enzymes. Oltipraz effectively induced quinone reductase in Hepa 1c1c7 cells defective in the aryl hydrocarbon receptor function required by bifunctional inducers [1].

In vivo: Dietary concentrations of oltipraz produce great inhibition of aflatoxin B1-induced hepatic tumorigenesis in rats. Levels of hepatic aflatoxin-DNA adducts and serum aflatoxin-albumin adducts decreased when biliary elimination of aflatoxin-glutathione conjugants increased, therefore providing predictive biomarkers that measured a chemopreventive effect. In other animal studies, oltipraz was found to inhibit chemically induced carcinogenesis in bladder, colon, breast, stomach, and skin cancer models [2].

Clinical trial: In a Phase I study, a single oral dose of oltipraz was given to normal volunteers at dose levels of 125, 250, 375, and 500 mg. There was no significant difference in half-life between the four dose levels nor in clearance at the 125 and 250 mg levels. A series of small trials evaluating single oral doses of oltipraz for up to 28 days also showed a short t1/2 (4.1-5.3 hours), a sustained steady state without variation after a loading dose, and increased serum and urine concentrations with consumption of a high-fat diet [2].

Reference:
[1] Clapper ML. Chemopreventive activity of oltipraz. Pharmacol Ther. 1998 Apr;78(1):17-27.
[2] Benson AB 3rd. Oltipraz: a laboratory and clinical review. J Cell Biochem Suppl. 1993;17F:278-91.