High molecular weight derivative of salmon calcitonin with prolonged hypocalcemic activity

A new method preparing a long-acting formula of salmon calcitonin, which possesses high specific activity, has been developed. This method consists of two processes: (a) preparation of a high molecular weight derivative of salmon calcitonin and (b) preparation of a zinc suspension of the derivative. The derivative was prepared by the incubation of reduced salmon calcitonin with bovine serum albumin. Although it retained almost the same biological activity as the original calcitonin, it was not longer acting. Addition of zinc to the solution of the derivative resulted in a suspension with biological activity significantly longer than the original calcitonin. This procedure is described for obtaining a sustained-release preparation of salmon calcitonin, which might be useful for other peptide drugs.