Analogs of the decapeptide GnRH which include two significantly modified amino acids at positions 5 and 6 inhibit the secretion of gonadotropins by the pituitary gland and inhibit the release of steroids by the gonads. Administration of an effective amount of such GnRH antagonists prevents ovulation of female mammalian eggs and/or the release of steroids by the gonads and may be used to treat steroid-dependent tumors. Particularly effective peptides which are soluble in water at physiologic pH and which have a low tendency to gel when administered in vivo have the following formula: Ac-.beta.-D-2NAL-(4Cl)D-Phe-D-3PAL-Ser-Aph(Q.sub.1)(3-amino-1,2,4 triazole)-D-Aph(Q.sub.2)(3-amino 1,2,4-triazole)-Leu-Lys (isopropyl)-Pro-D-Ala-NH.sub.2, where Q.sub.1 and Q.sub.2 are amino acids, such as Gly, .beta.-Ala, Ala, D-Ala, Ser, Aib, Ahx and Gab. Examples of other GnRH antagonists include Ac-.beta.-D-2NAL-(4Cl)D-Phe-D-3PAL-Ser-Aph(Atz)-D-Aph(Ac)-Leu-Lys(isopropyl )-Pro-D-Ala-NH.sub.2, Ac-.beta.-D-2NAL-(4Cl)D-Phe-D-3PAL-Ser-Aph(.beta.-Ala)(3-amino-1,2,4 triazole)-D-Aph(.beta.-Ala)(3-amino-1,2,4 triazole)-Leu-Lys(isopropyl)-Pro-D-Ala-NH.sub.2, Ac-.beta.-D-2NAL-(4Cl)D-Phe-D-3PAL-Ser-Aph(Ac-D-Ser)-D-Aph(Ac-D-Ser)-Leu-Ly s(isopropyl)-Pro-D-Ala-NH.sub.2, and Ac-.beta.-D-2NAL-(4Cl)D-Phe-D-3PAL-Ser-Aph(Ac)-D-Aph(Ac)-Leu-Lys(isopropyl) -Pro-D-Ala-NH.sub.2.
包括在5和6号位点有两个显著改变的
氨基酸的GnRH十肽类似物抑制垂体腺分泌
促性腺激素并抑制性腺激素的释放。给予足够剂量的这种GnRH拮抗剂可以防止哺乳动物雌性卵子的排卵和/或性腺激素的释放,并可用于治疗依赖于类
固醇的肿瘤。在生理pH下可溶于
水且在体内注射时具有低凝胶倾向的特别有效的肽具有以下公式:Ac-.beta.-D-2NAL-(4Cl)D-Phe-D-3PAL-Ser-Aph(Q.sub.1)(3-amino-1,2,4 triazole)-D-Aph(Q.sub.2)(3-amino 1,2,4-triazole)-Leu-Lys (isopropyl)-Pro-D-Ala-NH.sub.2,其中Q.sub.1和Q.sub.2是
氨基酸,例如Gly,.beta.-Ala,Ala,D-Ala,Ser,Aib,Ahx和Gab。其他GnRH拮抗剂的例子包括Ac-.beta.-D-2NAL-(4Cl)D-Phe-D-3PAL-Ser-Aph(Atz)-D-Aph(Ac)-Leu-Lys(isopropyl )-Pro-D-Ala-NH.sub.2,Ac-.beta.-D-2NAL-(4Cl)D-Phe-D-3PAL-Ser-Aph(.beta.-Ala)(3-amino-1,2,4 triazole)-D-Aph(.beta.-Ala)(3-amino-1,2,4 triazole)-Leu-Lys(isopropyl)-Pro-D-Ala-NH.sub.2,Ac-.beta.-D-2NAL-(4Cl)D-Phe-D-3PAL-Ser-Aph(Ac-D-Ser)-D-Aph(Ac-D-Ser)-Leu-Ly s(isopropyl)-Pro-D-Ala-NH.sub.2和Ac-.beta.-D-2NAL-(4Cl)D-Phe-D-3PAL-Ser-Aph(Ac)-D-Aph(Ac)-Leu-Lys(isopropyl) -Pro-D-Ala-NH.sub.2。