Drugs in Clinical Use Which Cause Cancer

A Novel Strategy to Predict Carcinogenicity of Antiparasitics Based on a Combination of DNA Lesions and Bacterial Mutagenicity Tests

Genotoxicity and carcinogenicity testing of pharmaceuticals prior to commercialization is requested by regulatory agencies. The bacterial mutagenicity test was considered having the highest accuracy of carcinogenic prediction. However, some evidences suggest that it always results in false-positive responses when the bacterial mutagenicity test is used to predict carcinogenicity. Along with major changes made to the International Committee on Harmonization guidance on genotoxicity testing [S2 (R1)], the old data (especially the cytotgenetic data) may not meet current guidelines. This review provides a compendium of retrievable results of genotoxicity and animal carcinogenicity of 136 antiparasitics. Neither genotoxicity nor carcinogenicity data is available for 84 (61.8%), while 52 (38.2%) have been evaluated in at least one genotoxicity or carcinogenicity study, and only 20 (14.7%) in both genotoxicity and carcinogenicity studies. Among 33 antiparasitics with at least one old result in in vitro genotoxicity, 15 (45.5%) are in agreement with the current ICH S2 (R1) guidance for data acceptance. Compared with other genotoxicity assays, the DNA lesions can significantly increase the accuracy of prediction of carcinogenicity. Together, a combination of DNA lesion and bacterial tests is a more accurate way to predict carcinogenicity.

Update of carcinogenicity studies in animals and humans of 535 marketed pharmaceuticals

This survey is a compendium of information retrieved on carcinogenicity in animals and humans of 535 marketed pharmaceuticals whose expected clinical use is continuous for at least 6 months or intermittent over an extended period of time. Of the 535 drugs, 530 have the result of at least one carcinogenicity assay in animals, and 279 (52.1%) of them gave a positive response in at least one assay. Only 186 drugs (34.8%) have retrievable information on carcinogenicity in humans, and 104 of them gave to a variable extent evidence of a potential carcinogenic activity. Concerning the correlation between results obtained in animals and epidemiological findings, 58 drugs gave at least one positive result in carcinogenicity assays performed in animals and to a variable extent displayed evidence of carcinogenicity in humans, but 97 drugs tested positive in animals and were noncarcinogenic in humans or vice versa. Our findings, which are in agreement with previous studies, indicate that the evaluation of the benefit/carcinogenic risk ratio should be always made in prescribing a drug.

Diethylstilbestrol, genetics, teratogenesis, and tumor spectrum in humans

Diethylstilbestrol (DES) is the first example of transplacental carcinogenesis in humans, as evidenced by an excess of clear cell adenocarcinoma of the vagina and cervix in exposed women. We hypothesize that: 1) in utero DES exposure will be responsible for a broader spectrum of cancer with variable age of onset as a function of latency effects in exposed humans of both sexes; 2) teratogenicity of DES will be more far-reaching than currently recognized and will harbor cancer implications in the face of known associations between teratogenesis and carcinogenesis; and 3) genetic heterogeneity will be a critical etiologic discriminant in DES associated cancer. This hypothesis embraces a prodigious body of data at the infrahuman level, as well as extant pharmacogenetic and ecogenetic observations in humans which signify heritable variations in response to environmental carcinogenic exposures. This hypothesis has important implications for drug testing with appropriate preventive strategies. Herein, particular restraints with monitoring through governmental legal channels must be employed. Past experience has clearly indicated negligence in shouldering this responsibility by both the pharmaceutical industry and government regulatory bodies.

Bioassay program for carcinogenic hazards of cancer chemotherapeutic agents

Various compounds and combinations thereof, of promise in the treatment of neoplastic diseases, were tested for possible carcinogenicity in Swiss mice and Sprague-Dawley rats. Some of the compounds were fairly active carcinogens, while others showed little or no evidence of carcinogenicity. The carcinogenicity of the drug combinations was generally less than that of the individual components.

The carcinogenicity of anticancer drugs: a hazard in man

The carcinogenic potential of anticancer drugs is discussed in the light of selected basic principles of chemical carcinogenesis. Anticancer drugs which act by alkylation and/or by binding tightly to DNA frequently cause cancer in experimental animals and may be carcinogenic in man. In addition, certain anticancer drugs act as cocarcinogens in experimental systems and augment the tumorigenicity of chemical carcinogens. Host determinants are important in chemical carcinogenesis. Many chemical carcinogens and anticancer drugs require metabolic activation by microsomal enzymes. Studies in twins have shown interindividual variation of drug metabolism in man is greater than intraindividual variation caused by exogenous factors. Therefore, certain individuals may be unusually susceptible to the carcinogenicity of anticancer drugs on a pharmacogenetic basis. Age is also a host determinant. At a given total dose level, age at first exposure to chemical carcinogens has been shown to be an important risk factor in experimental studies and in some epidemiologic investigations in man. Therefore, children may be especially susceptible to the carcinogenicity of anticancer drugs. These treated children have the potential of a normal lifespan; the latency period between initial exposure to a carcinogen and clinical evidence of cancer in man is long, usually 2-5 decades. The problems involved in extrapolating data of carcinogenicity in experimental animals to man are discussed. A single drug may have multiple consequences in experimental studies; for example, actinomycin D can act as an anticancer drug, an anticarcinogen, and a carcinogen. These uncertainities and the clinical results concerning second neoplasms following cancer therapy in both children and adults clearly indicate the need to follow carefully long-term survivors who have received cancer therapy.