Kinase experiment:

Membranes are prepared from HEK293 cells (ATCC) stably transfected with the human GHS-R1a receptor cDNA in the plasmid pcDNA3.1neo. Competition radioligand binding assays are performed in 96-well format with GF/C filters pre-soaked in 0.3% polyethyleneimine. Assays are performed at room temperature for 1 h in duplicate using 50 pM [125I]-ghrelin and 1 μg membrane per well in 50 mM HEPES, pH 7.4, 10 mM MgCl2, 0.2% bovine serum albumin and the following protease inhibitors: 100 μg/mL bacitracin, 100 μg/mL benzamidine, 5 μg/mL aprotinin, 5 μg/mL leupeptin. The membranes are harvested and washed three times with ice-cold ish buffer containing 50 mM HEPES, pH 7.4 and 10 mM MgCl2. IC50 and Ki values are determined using Prism by GraphpadTM. The Kd of [125I]-ghrelin at membranes expressing human GHS receptors is calculated to be 0.2 nM.

Animal experiment:

The study tested capromorelin flavored oral solution with 30 mg/mL of capromorelin compared to a matched placebo flavored oral solution treatment (which contains all the ingredients of the formulation without capromorelin) administered for 4 days. Dogs are randomized into two groups, with Group 1 receiving placebo (0.1 mL/kg) and Group 2 receiving 3.0 mg/kg. Both groups are treated once a day at approximately 9 AM each day. The first day of dosing is considered Day 0. The placebo and test drug are administered by a syringe placed in the corner of the mouth. The Day 0 weight is used for dose calculations.

Capromorelin Tartrate is an orally active, potent growth hormone secretagogue receptor (GHSR) agonist, with Ki of 7 nM for hGHS-R1a.

Capromorelin stimulates GH release in rat pituitary cell cultures with EC50 of 3 nM[2].

Dogs receiving capromorelin (30 mg/mL) have food consumption that is significantly greater than dogs treated with placebo. All dogs in the capromorelin group gain weight by 0.52 kg, more than that of placebo group[1]. Capromorelin shows enhanced intestinal absorption in rodent models and exhibits superior pharmacokinetic properties, including high bioavailabilities in two animal species [F(rat)=65%, F(dog)=44%][2]. Capromorelin stimulates GH release in anesthesized rat model, with ED50 of 0.05 mg/kg iv[2].

References:
[1]. Zollers B, et al. Capromorelin oral solution (ENTYCE®) increases food consumption and body weight when administered for 4 consecutive days to healthy adult Beagle dogs in a randomized, masked, placebo controlled study. BMC Vet Res. 2017 Jan 5;13(1):10.
[2]. Carpino PA, et al. Pyrazolinone-piperidine dipeptide growth hormone secretagogues (GHSs). Discovery of capromorelin. Bioorg Med Chem. 2003 Feb 20;11(4):581-90.