L. A. ELSON 



' Radiomimetic ' Chemicals— The inhibitory effect of certain carcinogenic 

 chemicals on the growth of rats was first described by Haddow, Scott and 

 Scott* and compared with the growth inhibition produced by X-radiation. 

 Following up the tumour-inhibiting action also shown by these substances, 

 a large number of different types of chemicals has been examined and com- 

 pounds have been developed with much more powerful growth-inhibitory 



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Figure 2. Effect of whole body X-irradiation on growth rate. Selected examples 



properties than the original carcinogens. One class of these is related 

 to the ' nitrogen mustards ' which are often described as radiomimetic because 

 of their radiation-like effects on dividing cells and on the haematopoietic 

 system. Of these a series of water-soluble nitrogen mustards (Everett, 

 Roberts and Ross^) were found to have less general toxic properties than 

 nitrogen mustard itself HNg formula CH3.N (GH2GH2C1)2 and one member 

 CB 1348 N.N-dichloroethyl-p-aminophenyl butyric acid p.COOH (CH2)3. 

 C6H4-N(CH2CH2C1)2 is undergoing clinical trials in cases of lymphoma 

 and lymphatic leukaemia. 



237 



