Calvacin is a potent, antitumor mucoprotein which is cumulative in effect and which causes a prolonged intoxication characterized by anorexia and extreme weight loss. It induces a wide spectrum of lesions in experimental mammals. The more prominent include hepatic necrosis, biliary obstruction, renal tubular necrosis, fibrinoid degeneration, myofibrillar necrosis in cardiac and skeletal muscle, and pulmonary hemorrhages. Calvacin is a complex mixture of antigenic substances. Sensitization has been demonstrated in rabbits, guinea pigs, and dogs; and drug tolerance, associated with serum precipitins, has been shown in rats. Clinical trials may be complicated by the antigenic properties of the agent. In particular the development of hypersensitivity must be considered a possible hazard.

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Aided by CCNSC Contract No. SA-43-p4-2445 from the National Cancer Institute, U.S.P.H.S.

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