<span>The present invention relates to the production of a new composition of matter of high immunosuppressive activity. Niridazole, i.e. 1-(5-nitro-2-thiazolyl)-2-imidazolidinone has been employed widely as an anti-parasitic drug. An article by Mahmoud et al in Journal of Immunology Vol. 114 (1975) pages 279 ff reports on the discovery by the instant applicants that in patients undergoing prolonged treatment with niridazole there have been observed suppressed inflammations. Pursuing this, in tests on experimental animals niridazole administration has resulted in suppression of inflammation related to delayed hypersensitivity including retardation of allograft rejection. Human studies by Webster et al then corroborated the suppression of delayed hypersensitivity-type reactions by niridazole. It was speculated in both articles that the active material might have been a metabolite of niridazole rather than niridazole per se.The instant applicants have since carried these researches further and have established that the active immunosuppressive agent is either a metabolite or is synthesized in the body in response to niridazole administration and they have provided processes whereby this active agent can be recovered, purified and concentrated, and compounded in a form suitable form administration. They have also provided a process for its chemical synthesis in the laboratory. Specifically, they have found that the urine of mammals to which niridazole has </span><span>been administered exhibit the desired immunosuppressive activity even long after the niridazole per se has been metabolized. They have therefore obtained the active material from the urine of mammals which have received niridazole by mixing the urine with an aqueous lower alkanol, separating solids from the liquid, drying said liquid, extracting said dried material with a lower alkyl ketone, drying the extract, subjecting the dried extract to chromatography, and collecting a fraction high in immunosuppressive activity. Desirably the aqueous lower alkanol has a concentration of lower alkanol of about 30 to 70% by volume and is employed in about 50 to 200% by volume of the initial urine. Advantageously the lower alkyl ketone contains up to about 25% by volume of a lower alkanol, and/or other hydrophilic solvents, the dried material is subjected to a plurality of extractions with the lower ketone until substantially all the colored material is extracted from the dried material, and the extracts are combined and then dried. The dried extracts are then dissolved, preferably in water, the solution passed over a chromatographic absorbent and eluted with an aqueous acid, e.g. butanol: acetic acid: water. The eluate includes fractions of high immunosuppressive activity, e.g. at least about 2. DELTA. Log [Antigen] units as measured by the direct MIF assay, which fractions are suited for intravenous administration.http://www.google.com/patents?vid=USPAT4168316</span>
