Abstract: Antide is the decapeptide, N--Ac--D--2--Nal,D--pClPhe, D--3--Pal, Ser,NicLys, D--NicLys, Leu, ILys, Pro, D--Ala,NH.sub.2 which is an antagonist of luteinizing hormone releasing hormone (LHRH). This decapeptide, like others of the present invention, has high antiovulatory activity (AOA) and releases negligible histamine. Antide is scheduled for scale-up, safety testing and evaluation in the experimental primate and in clinical medicine. Numerous other peptides having structures related to Antide were prepared and tested. These peptides had variations primarily in positions 5, 6, 7, and 8. Of these, N--Ac--D--2--Nal, D--pClPhe,D--3--Pal,Ser,PicLys,cis--DpzACAla, Leu,ILys,pro,D--Ala--NH.sub.2 was one of the most potent and had higher antiovulatory activity than Antide, i.e. 73%/0.25 ug and 100%/0.5 ug vs. 36%/0.5 ug and 100%/1.0 ug. Antide showed significant, (p<0.001) duration of action, when injected at a dose of 10 ug, 44 hours before 50 ng of the agonist, [D--3--Qal.sup.6 ]--LHRH.

Abstract: The objective of the research was the achievement of antagonists of the luteinizing hormone releasing hormone (LHRH) which would have adequate antagonistic activity to prevent ovulation, and yet would not have a pronounced structural feature to release a histamine, in vivo. Some existing antagonists of LHRH produced edema of the face and extremities in rats. This recent recognition of the edematogenic and anaphylactoid activities of an antagonist of LHRH necessitated new structural changes if such antagonists were to be considered for potential use as contraceptive agents in the human. Consequently, 57 peptides have been designed, synthesized and bioassayed toward achieving a potent antagonist which releases negligible histamine.

Abstract: The chemical structure of the luteinizing hormone releasing hormone (LHRH) was elucidatd in 1971. Since then, a very large number of international investigators synthesized more than 100 monosubstituted and about 14 disubstituted analogs of LHRH. All of these analogs were synthesized from natural amino acids having the L-configuration. Not one of these approximately 114 analogs showed agonist activity equivalent to that of LHRH. Two of the 114 were about 60% as active, and neither one has had any utility. We have investigated the six individual L-amino acids which occur in positions 5, 7, and 8 of the four naturally occurring LHRH's which exist in porcine/ovine, salmon, and chicken tissue.