Pyrazolinone-piperidine dipeptide growth hormone secretagogues (GHSs)

Novel pyrazolinone-piperidine dipeptide derivatives were synthesized and evaluated as growth hormone secretagogues (GHSs). Two analogues, capromorelin (5, CP-424391-18, hGHS-R1a Ki=7 nM, rat pituicyte EC50=3 nM) and the des-methyl analogue 5c (hGHS-R1a Ki=17 nM, rat pituicyte EC50=3 nM), increased plasma GH levels in an anesthesized rat model, with ED50 values less than 0.05 mg/kg iv. Capromorelin showed enhanced intestinal absorption in rodent models and exhibited superior pharmacokinetic properties, including high bioavailabilities in two animal species [F(rat)=65%, F(dog)=44%]. This short-duration GHS was orally active in canine models and was selected as a development candidate for the treatment of musculoskeletal frailty in elderly adults.