Flouret G, Mahan K, Majewski T
Department of Physiology, Northwestern University Medical School, Chicago, Illinois 60611.
J Med Chem. 1992 Feb 21;35(4):636-40. doi: 10.1021/jm00082a004.
We report analogues of N-Ac-D-Nal-D-Cpa-D-Pal-Ser-Lys(Pic)-D-Lys(Pic)-Leu-Ilys-Pro-D-Ala- NH2, the parent antagonist (PA), which is a potent antagonist of LHRH. To simplify future radioactive labeling we prepared N-Ac-D-Nal-D-Cpa-D-Pal-Ser-Lys(Pic)-D-Lys(Pic)-Leu-Arg-Pro-D-Ala-NH2 (4), [Arg8]PA, which had good activity in the antiovulatory assay (AOA). Other analogues were designed at first by substituting with Arg at positions 5, 6, 7, 9, and 10, and Trp or Leu at position 8. Subsequent analogues were prepared in attempts to improve the AOA of the initial ones. Substitutions with Arg9 or Arg10 led to analogues 1-3 with no AOA activity at 5 micrograms/rat. However, substitution with Arg7 gave 9, [Arg7,Leu8]PA, with significant activity in the AOA at 5 micrograms/rat and borderline activity at 2.5 micrograms/rat, and substitution with Ilys7 gave 13, [Ilys7,Leu8]PA, with borderline activity at 2 micrograms/rat, both analogues showing much weaker activity than PA in the histamine release assay (HRA) and therefore being potentially safer. Substitutions with D-Arg6 or Arg5 led to analogues with either good AO activity at 5 micrograms/rat (analogue 7) or with borderline activity at 5 micrograms/rat (analogue 8), although both were more potent than 6 in the HRA. Combinations of Ilys or Arg at positions 7 and 8 led to 10 and 11, both of which were tested at 2 micrograms/rat and found to have either good AO activity (analogue 10) or borderline activity (analogue 11) but unsuitably potent in HR. Substitutions using Ilys7 and neutral amino acids at position 8 led to 14-17 which were inactive in the AOA. Of great significance is the substitution with Arg7 yielding analogue 9, which was much safer in the HRA than analogue 4, [Arg8]PA. Analogues 9 and 13, featuring substitutions with the Arg7-Leu8 or Ilys7-Leu8 sequences were even safer than PA or 6 in the HRA. Analogue 12, [D-Trp3,Tyr5,D-Arg6,Arg7,Leu8]PA, featuring the Arg7-Leu8 sequence, had much lower potency in the HRA than [D-Trp3,Tyr5,D-Arg6,Leu7,Arg8]PA, which has the normal Leu7-Arg8 sequence. Ilys7 together with neutral amino acids at position 8 led to analogues 14-17 which were also very weak (safer) in the HRA, with the smaller amino acids Ala8 and Abu8 being the weakest of all analogues prepared.(ABSTRACT TRUNCATED AT 400 WORDS)
我们报道了N-乙酰基-D-萘丙氨酸-D-对氯苯丙氨酸-D-苯基丙氨酸-丝氨酸-赖氨酸（苦味酸盐）-D-赖氨酸（苦味酸盐）-亮氨酸-异亮氨酸-脯氨酸-D-丙氨酸-NH₂的类似物，其母体拮抗剂（PA）是促黄体生成素释放激素（LHRH）的强效拮抗剂。为简化未来的放射性标记，我们制备了N-乙酰基-D-萘丙氨酸-D-对氯苯丙氨酸-D-苯基丙氨酸-丝氨酸-赖氨酸（苦味酸盐）-D-赖氨酸（苦味酸盐）-亮氨酸-精氨酸-脯氨酸-D-丙氨酸-NH₂（4），即[精氨酸⁸]PA，它在抗排卵试验（AOA）中具有良好活性。最初通过在第5、6、7、9和10位用精氨酸取代，以及在第8位用色氨酸或亮氨酸取代来设计其他类似物。随后制备了后续类似物以试图提高最初类似物的AOA活性。用精氨酸⁹或精氨酸¹⁰取代得到类似物1 - 3，在5微克/大鼠剂量下无AOA活性。然而，用精氨酸⁷取代得到9，即[精氨酸⁷，亮氨酸⁸]PA，在5微克/大鼠剂量下在AOA中有显著活性，在2.5微克/大鼠剂量下有临界活性，用异亮氨酸⁷取代得到13，即[异亮氨酸⁷，亮氨酸⁸]PA，在2微克/大鼠剂量下有临界活性，这两种类似物在组胺释放试验（HRA）中显示出比PA弱得多的活性，因此可能更安全。用D-精氨酸⁶或精氨酸⁵取代得到的类似物，在5微克/大鼠剂量下要么具有良好的AO活性（类似物7），要么具有临界活性（类似物8），尽管两者在HRA中都比6更有效。在第7和8位同时存在异亮氨酸或精氨酸的组合得到10和11，两者均在2微克/大鼠剂量下进行测试，发现要么具有良好的AO活性（类似物10），要么具有临界活性（类似物11），但在HR中效力不合适。用异亮氨酸⁷和第8位的中性氨基酸取代得到14 - 17，它们在AOA中无活性。具有重要意义的是用精氨酸⁷取代得到类似物9，它在HRA中比类似物4，即[精氨酸⁸]PA安全得多。具有精氨酸⁷ - 亮氨酸⁸或异亮氨酸⁷ - 亮氨酸⁸序列取代的类似物9和13在HRA中甚至比PA或6更安全。类似物12，即[D-色氨酸³，酪氨酸⁵，D-精氨酸⁶，精氨酸⁷，亮氨酸⁸]PA，具有精氨酸⁷ - 亮氨酸⁸序列，在HRA中的效力比具有正常亮氨酸⁷ - 精氨酸⁸序列的[D-色氨酸³，酪氨酸⁵，D-精氨酸⁶，亮氨酸⁷，精氨酸⁸]PA低得多。异亮氨酸⁷与第8位的中性氨基酸一起得到类似物14 - 17，它们在HRA中也非常弱（更安全），较小的氨基酸丙氨酸⁸和氨基丁酸⁸是所有制备的类似物中最弱的。（摘要截断于400字）
