[Testing of a cyclophosphamide metabolite on Yoshida ascites cells in vitro]

Ifosfamide - History, efficacy, toxicity and encephalopathy

In this review we trace the passage of fundamental ideas through 20^th century cancer research that began with observations on mustard gas toxicity in World War I. The transmutation of these ideas across scientific and national boundaries, was channeled from chemical carcinogenesis labs in London via Yale and Chicago, then ultimately to the pharmaceutical industry in Bielefeld, Germany. These first efforts to checkmate cancer with chemicals led eventually to the creation of one of the most successful groups of cancer chemotherapeutic drugs, the oxazaphosphorines, first cyclophosphamide (CP) in 1958 and soon thereafter its isomer ifosfamide (IFO). The giant contributions of Professor Sir Alexander Haddow, Dr. Alfred Z. Gilman & Dr. Louis S. Goodman, Dr. George Gomori and Dr. Norbert Brock step by step led to this breakthrough in cancer chemotherapy. A developing understanding of the metabolic disposition of ifosfamide directed efforts to ameliorate its side-effects, in particular, ifosfamide-induced encephalopathy (IIE). This has resulted in several candidates for the encephalopathic metabolite, including 2-chloroacetaldehyde, 2-chloroacetic acid, acrolein, 3-hydroxypropionic acid and S-carboxymethyl-L-cysteine. The pros and cons for each of these, together with other IFO metabolites, are discussed in detail. It is concluded that IFO produces encephalopathy in susceptible patients, but CP does not, by a "perfect storm," involving all of these five metabolites. Methylene blue (MB) administration appears to be generally effective in the prevention and treatment of IIE, in all probability by the inhibition of monoamine oxidase in brain potentiating serotonin levels that modulate the effects of IFO on GABAergic and glutamatergic systems. This review represents the authors' analysis of a large body of published research.

[The effect of cyclophosphamide on tumors in the sensitivity-test (author's transl)]

The sensitivity of tumors to cyclophosphamide was tested in vitro. For this purpose, the urine of cyclophosphamide-treated rats (90 min., 500 mg/kg) was used. This method of activating cyclophosphamid proved more advantageous than other methods; all cytostatically effective metabolites can be used in the test and the production of metabolites can easily be standardized. Consequently results with good reproducibility can be obtained. In various long-term and short-term test models with animal transplantation-tumors in vitro, the effects of the cyclophosphamide metabolites depended on the dose used. This test results in the various test models are comparable. In the tissue-culture of tumors (long-term test) sensitivity was evaluated by using morphological criteria as well as by counting cell numbers. In the short-term test the sensitivity of tumors was found out by influencing the nucleic acid syntheses (3-H-thymidine-, 3-H-uridine-incorporation). As the tissue-culture meets with difficulties as a routine clinical examination, the use of the short-term test is recommended. Using as model the fast proliferating WALKER-256-carcinosarcoma and a slowly proliferating rat adenocarcinoma, the results of the sensitivity-test in vitro were compared with the effects of therapy in animal tests. Tumor remissions corresponding with the results reached in vitro, which depended on dosis, could also be achieved in both transplantation-tumors. Human tumors, tested in in vitro studies (short-term-test), show a different sensitivity to cyclophosphamide.