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Cancer chemoprotection by oltipraz: experimental and clinical considerations
1Department of Epidemiology,p5chool of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland.
Abstract:
Oltipraz (4-methyl-5-(2-pyrazinyl)-1,2-dithiole-3-thione) is an antischistosomal drug presently under evaluation as a possible chemoprotective agent in humans. To date, oltipraz has proved effective as an inhibitor of carcinogenesis in experimental models for breast, bladder, liver, forestomach, colon, tracheal, lung, and skin cancer. Studies on the mechanisms of action of oltipraz indicate that it affects the metabolism and disposition of chemical carcinogens, principally through the induction of electrophile detoxication enzymes. While this feature is common to many different classes of both natural and synthetic experimental chemoprotectors (i.e., phenolic antioxidants, isothiocyanates, flavonoids, indoles, cinnamates, coumarins, terpenes, and others), oltipraz may offer the earliest and easiest prospect for examining the role of enzyme induction as a protective strategy in humans. Unlike the situation with many of the anutrients, substantial preclinical research has already been conducted with oltipraz to establish its safety and efficacy in animals. Hopefully, Phase I investigations will demonstrate a high tolerance for oltipraz in the chemoprotective dose range of the drug. A major concern for the success of any trial is selecting participants who are likely to adhere to the intervention as well as to all aspects of the protocol. Factors influencing participation and adherence in a trial include the design of the trial, the nature of the disease under study as well as the nature of the intervention, in particular the toxicities of the intervention (J. A. Tangrea, M. E. Adrianza, and W. E. Helsel, Cancer Epi Biomarkers Prev 1992; 1:325-330). Chemoprotection trials with oltipraz have an excellent prospect for success. Individuals with known carcinogenic exposures are likely to be interested in participation in trials designed to reduce the risks of the exposures. Moreover, the availability of intermediate markers reflecting the modulation of the biologically effective dose of environmental carcinogens as study end points will enable efficient trials to be designed.
Insights
Oltipraz, an antischistosomal drug, shows promise as a human chemoprotective agent by inducing enzymes that detoxify carcinogens. Its established safety profile and potential for successful clinical trials make it a strong candidate for cancer prevention research.
Area of Science:
- Oncology
- Pharmacology
- Biochemistry
Background:
- Oltipraz (4-methyl-5-(2-pyrazinyl)-1,2-dithiole-3-thione) is an antischistosomal drug with demonstrated chemopreventive effects in various experimental cancer models.
- Its mechanism involves modulating carcinogen metabolism and enhancing the activity of electrophile detoxication enzymes.
Purpose of the Study:
- To evaluate oltipraz as a potential chemoprotective agent in humans.
- To explore the feasibility of using enzyme induction as a cancer prevention strategy in clinical settings.
Main Methods:
- Review of preclinical data on oltipraz's safety and efficacy in animal models.
- Consideration of factors influencing human clinical trial design and participant adherence.
- Assessment of oltipraz's potential for modulating biologically effective doses of environmental carcinogens.
Main Results:
- Oltipraz has shown efficacy in inhibiting carcinogenesis across multiple experimental models.
- Substantial preclinical research supports oltipraz's safety and efficacy.
- Phase I investigations are anticipated to confirm its tolerability at chemoprotective doses.
Conclusions:
- Oltipraz presents a promising candidate for human chemoprotection due to its mechanism of action and established safety profile.
- Chemoprotection trials with oltipraz are likely to succeed, particularly in individuals with known carcinogenic exposures.
- The drug's ability to modulate carcinogen metabolism and the availability of intermediate markers facilitate efficient trial design.