Bridget Butler

A Novel Non-Peptidyl Growth Hormone Secretagogue

Direct screening of preselected compounds in a rat primary pituitary cell culture assay, followed by chemical modification of selected pharmacophores led to the identification of a novel non-peptidyl class of GH secretagogues (substituted benzolactams). The prototype compound of this class, L-692,429, stimulated GH release from rat primary pituitary cells in a time- and dose-dependent manner with an EC50 value of 60 nM. Under the same conditions, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (GH-releasing peptide, GHRP-6) and GH-releasing factor (GRF) had EC50 values of 10(-8) and 5 x 10(-10) M, respectively. L-692,428, the S-enantiomer, of L-692,429, was inactive at a concentration as high as 2 microM. GH release induced by L-692,429 was inhibited by somatostatin as well as by GHRP-6 and substance P antagonists but not by GRF or opiate antagonists. L-692,400, which is structurally related to L-692,429 but biologically inactive, inhibited GH response not only to L-692,429 but also GHRP-6. Like GHRP-6, L-692,429 alone had no effect on intracellular cAMP levels; however, it synergized with GRF to further increase both the accumulation of cAMP and the release of GH. Maximal effects of L-692,429 and GHRP-6 on GH release were comparable. Interestingly, when presented together in maximal concentrations, L-692,429 and GHRP-6 did not cause an additional GH release when compared with either secretagogue alone. L-692,429 had a small effect on prolactin release but not adrenocorticotropin.(ABSTRACT TRUNCATED AT 250 WORDS)

Potent nonpeptide GnRH receptor antagonists derived from substituted indole-5-carboxamides and -acetamides bearing a pyridine side-chain terminus

A pyridine side-chain terminus has been incorporated into the indole-5-carboxamide and indole-5-acetamide series of GnRH antagonists. Potent activity was observed in binding and functional assays. Certain branched or cyclic tertiary amides were identified as preferred in each series. Alkylation of the side-chain secondary amine had generally unfavorable effects. Variations of the gem-dialkyl substituents in the indole-5-acetamide series were also investigated.

Structure-activity relationships in the amino acid sidechain of L-692,429

Abstract Development of L-692,429, the prototype compound of a novel class of growth hormone (GH) secretagogues1, focused on defining the structure-activity relationships in the amino acid sidechain. Modification of the dimethyl-β-alanine group revealed the basic amine as an essential pharmacophore for GH releasing activity. Evaluation of a variety of amino-substittued derivatives led to the identification of analogs with improved potency.

Synthesis and biological activities of phenyl piperazine-based peptidomimetic growth hormone secretagogues.

A new class of potent, orally active phenyl piperazine-based GH secretagogues have been discovered from attempts to mimic the arrangement of the phenyl substituent in the spiroindanyl piperidine and spiroindoline sulfonamide privileged structures of 4 and 1, respectively. The best of these compounds, 18 (EC50 = 2.8 nM) is nearly as potent as MK-0677 for releasing GH from rat pituitary cells.

Synthesis and biological activities of spiroheterocyclic growth hormone secretagogues

The synthesis and biological activities of a series of spiroheterocyclic growth hormone secretagogues are reported. Modification of the spiroindane part-structure of the prototypal secretagogue L-162,752 revealed that the spiroindane could be replaced with spirobenzodihydrothiophen derivatives to enhance not only in vitro potency but also oral activity. In this study non-aromatic D-2-amino-4-cyclohexylbutanoic analogs (8a-8d) were also identified to be active secretagogues.

Analogs of the orally active growth hormone secretagogue L-162,752

Abstract A series of spiroindane growth hormone secretagogues that vary in their amino side chains is reported. Variations in these side chains markedly affect growth hormone release in vitro and in vivo . The best side chain in this series of secretagogues is α-methylalanine. L-162,752 not only stimulated GH release from rat pituitary cells, but also induced GH release in dogs upon i.v. and p.o. administration.

Growth hormone releasing peptides: a comparison of the growth hormone releasing activities of GHRP-2 and GHRP-6 in rat primary pituitary cells.

In the present study, the effect of GHRP-2 on GH release was evaluated in rat primary pituitary cells, and the results were compared with those elicited by GHRP-6. In the rat system, GHRP-2, like GHRP-6, acts synergistically with GRF to release GH. Co-administration of GHRP-2 and GHRP-6 at maximal concentrations had no further effect on GH release than either one alone. The GHRPs were able to desensitize cells to each other, but not to GRF. The effect of GHRP-2 was inhibited by Peptide Antagonist, but was not affected by a GRF antagonist. In conclusion, GHRP-2 was found to stimulate GH release from rat pituitary cells via the same receptor and mechanism as GHRP-6, despite the structural difference between the peptides.

BENZOLACTAM GROWTH HORMONE SECRETAGOGUES : CARBOXAMIDES AS REPLACEMENTS FOR THE 2'-TETRAZOLE MOIETY OF L-692,429

Abstract A variety of 2′-carboxamides was investigated as replacements for the 2′-tetrazole moiety of L-692,429. Investigation of the structure-activity relationships of the carboxamide series determined that primary and secondary carboxamides are potent growth hormone secretagogues in vitro . L-700,653 ( 11 ) was identified as an orally active GH secretagogue in dogs.

The synthesis and activity of spiroindane growth hormone secretagogues

Abstract The synthesis and activities of a series of spiroindane growth hormone secretagogues is reported. Modification of the benzylic position of the spiroindane has resulted in a dramatic increase in potency resulting in subnanomolar peptidomimetic growth hormone secretagogues. In vivo data demonstrating the good oral activity of these analogs is reported.

Structure-activity relationships of the non-peptidyl growth hormone secretagogue L-692,429

Abstract Systematic investigation of the amino acid sidechain of L-692,429, the prototype of a novel class of benzolactam growth hormone (GH) secretagogues, has led to the preparation of L-692,585, a 2(R)-hydroxypropyl amino analog, which is twenty times more potent in vitro than L-692,429. Additional amino modifications reported here further define the structure-activity profile for L-692,429.