Semisynthetic anti-LHRH vaccine causing atrophy of the prostate.

A modified luteinizing hormone releasing hormone (LHRH) analog (D-lys)6 was synthesized and linked to epsilon-amino caproic acid at the 6th position. The free amino group thus generated was used for conjugation to diphtheria toxoid. Immunogenicity and bioefficacy studies of this conjugate vaccine were carried out in rodents. All immunized animals produced antibodies reactive with native LHRH. A gradual decline in testosterone levels accompanied the rise in anti-LHRH titers. On necropsy, after 10 weeks, a significant reduction in the relative weights of testes and accessory sex organs was noticed. Of particular significance was the marked atrophy of the prostate, indicating a possible therapeutic application of this vaccine in the treatment of androgen-dependent carcinoma of the prostate.