Evaluation of a Stable Gonadotropin-Releasing Hormone Analog in Mice for the Treatment of Endocrine Disorders and Prostate Cancer

Abstract

Gonadotropin-releasing hormone (GnRH) receptor agonists have wide clinical applications including the treatment of prostate cancer and endocrine disorders. However, such agonists are characterized by poor pharmacokinetic properties, often requiring repeated administration or special formulations. Therefore, the development of novel peptide analogs with enhanced in vivo stability could potentially provide therapeutic alternatives. The pharmacological evaluation of a bioactive peptide [Des-Gly 10 ,Tyr 5 (OMe),D-Leu 6 ,Aze-NHEt 9 ]GnRH, analog 1, is presented herein and compared with leuprolide. Peptide stability was evaluated using mouse kidney membrane preparations, followed by a liquid chromatography-tandem mass spectrometry-based approach that afforded identification and quantification of its major metabolites. The analog was significantly more stable in vitro in comparison with leuprolide. In vitro and in vivo stability results correlated well, encouraging us to develop a clinically relevant pharmacokinetic mouse model, which facilitated efficacy measurements using testosterone as a biomarker. Analog 1, an agonist of the GnRH receptor with a binding affinity in the nanomolar range, caused testosterone release in mice that was acutely dose-dependent, an effect blocked by the GnRH receptor antagonist cetrorelix. Repeated dosing studies in mice demonstrated that analog 1 was well tolerated and had potency similar to that of leuprolide, based on plasma and testis testosterone reduction and histopathological findings. Analog 1 also shared with leuprolide similar significant antiproliferative activity on androgen-dependent prostate cancer (LNCaP) cells. On the basis of pharmacokinetic advantages, we expect that analog 1 or analogs based on this new design will be therapeutically advantageous for the treatment of cancer and endocrine disorders.

Evaluation of the Biological Properties and the Enzymatic Stability of Glycosylated Luteinizing Hormone-Releasing Hormone Analogs

“…The glycosylated LHRH compounds were shown to be less stable against metabolizing enzymes in the kidney compared to that of the liver. This was in line with the previous studies showing that the kidney plays an important role in the metabolism of LHRH derivatives (39,40). The native LHRH is degraded rapidly in blood and has a short half-life of 3-4 min (36).…”

GnRH-Gemcitabine Conjugates for the Treatment of Androgen-Independent Prostate Cancer: Pharmacokinetic Enhancements Combined with Targeted Drug Delivery

“…Cells were plated in 96-well plates (5,000 cells/well) and incubated for 72 h with either GnRH-gemcitabine conjugates or gemcitabine at selected concentrations. IC 50 values shown represent means of three experiments performed in triplicates ± SD. [D -Lys 6 ]-GnRH treatment had no effect in the selected concentrations.…”

Peptide–Drug Conjugate GnRH–Sunitinib Targets Angiogenesis Selectively at the Site of Action to Inhibit Tumor Growth

“…SAN1GSC contains the potent [D-Lys 6 ]-GnRH agonist peptide, and it is possible that it exerts an additional central effect through the pituitary in the described dosing scheme, leading to the lowering of gonadal hormone levels (31).…”

“…4A) is presented in the Supplementary Information section (Supplementary Information Sections S1 and S3). All molecules were analyzed by mass spectrometry (MS) to obtain the key spectral features necessary for their quantification in blood and tissue as described previously (7,31). Total polar surface area and clogP values were predicted by Chemdraw Ultra (v10, PerkinElmer Informatics).…”