definiens: means a polypeptide molecule with the fonnula : Acetyl - D-3-(2 ' -naphtyl)­alanine - D-4 - chlorophenylalanine- D-3 -(3 ' -pyridyl ) -alanine- L - serine- L - tyros ine - D - ci truline - L­leucine - L - arginine - L - proline - D - alanine - amide, and the molecular weight of 1431.06, calculated as the anhydrous free base . The structural fonnula of the acetate salt is as follows : ( Ac - D - Nal(2 ) I - D - Cpa ( 4)2 - D - Pal(3)3 -Ser4 - Tyr5 - D - Cit6 - Leu7 - Arg8- Pro9 - D - Alal O - NH2 X AcOH ) means Cetrorelix and any phannaceutically acceptable salt, ester, or ether thereof