The problem of resistance has also become apparent in the chemotherapy of leprosy. New and more potent therapeutic agents must therefore be found in order to overcome this.<br>We have developed several new agents and some of the most promising will be introduced here.<br>a) DDS Acetate1)<br>The presence of the acetate of DDS in the urine and blood following administ-ration of DDS in man and rabbit was verified by paper electrophoresis and studies were carried out as to whether the mono- and diacetate, which are the detoxifying form, had a therapeutic effect. It was observed that deacetylation takes place in the body and the relationship between acetylation and deacetylation shown in Fig. 2 was found to be present. This compound (diacetate) was named Acetamin and clinical tests were conducted. The following results were obtained.<br>Of a total of 14 cases treated, the agent was effective in 8, somewhat effective in 3 and ineffective in 2 cases. There were no side effects. An effect was also noted in cases no longer responding to DDS and Promin and this agent may be used in patients hypersensitive to the latter two compounds.<br>b) Thiozamin (4-amino-4'-aldehyde-thiosemicarbazone dipheny-sulfone) 2) In this compound, the -NH2 of DDS was replaced by the effective side chain of Tibion (Fig. 3), and the influence on the therapeutic effect of DDS was examined. This compound was named Thiozamin and pharmacological and clinical tests conducted. The following results were obtained.<br>Of a total of 19 cases of the lepromatous type, there were 8 effective, 6 somewhat effective, 2 ineffective and 3 exacerbated cases. In 3 cases of the neural type, it was effective in 3 cases. The rate of efficacy was therefore 73.6% and there were almost no side effects.<br>c) DOT (4-dimethylaminobenzaldehyde-4'-oxyphenyl-thiosemicarbazone) and its derivatives3)<br>From the structure (Fig. 4) it can be seen, that is compound belongs to the thiosemi-carbazone group and the nucleus is similar to Ciba 1906. A potent antibacterial action against the tubercle bacillus is found in vitro. The toxicity is quite low and clinical tests were carried out since it was believed that it could be given safely in man. It was found that though there was a marked improvement in the symptoms in some cases, ENL developed. Clinical tests are therefore being continued on the dosage and other problems.<br>d) Pyrazine Derivatives4)<br>The chemical structure is shown in Fig. 5. PBS-1 and PBS-2 show a pronounced suppressive action against the tubercle bacillus in vitro. Toxicity is also low suggest-ing the possibility of clinical use. Pharmacological tests are being carried out at present.