Anamorelin HCl (ONO-7643), a novel ghrelin receptor agonist, for the treatment of cancer anorexia-cachexia syndrome: preclinical profile

Abstract

Background: Anamorelin HCl (ANAM) is a novel, orally active, ghrelin receptor agonist in clinical development for the treatment of cancer cachexia. We report in vitro and in vivo studies evaluating the preclinical pharmacologic profile of ANAM.

Methods: Fluorescent imaging plate reader and binding assays in HEK293 and baby hamster kidney cells determined the agonist and antagonist activity of ANAM, and its affinity for the ghrelin receptor. Rat pituitary cells were incubated with ANAM to evaluate its effect on growth hormone (GH) release. In vivo, rats were treated with ANAM 3, 10, or 30 mg/kg, or control orally, once daily for 6 days to evaluate the effect on food intake (FI) and body weight (BW), and once to assess GH response. In pigs, single (3.5 mg/kg) or continuous (1 mg/kg/day) ANAM doses were administered to assess GH and insulin-like growth factor (IGF-1) response.

Results: ANAM showed significant agonist and binding activity on the ghrelin receptor, and stimulated GH release in vitro. In rats, ANAM significantly and dose-dependently increased FI and BW at all dose levels compared with control, and significantly increased GH levels at 10 or 30 mg/kg doses. Increases in GH and IGF-1 levels were observed following ANAM administration in pigs.

Conclusion: ANAM is a potent and highly specific ghrelin receptor agonist with significant appetite-enhancing activity, leading to increases in FI and BW, and a stimulatory effect on GH secretion. These results support the continued investigation of ANAM as a potential treatment of cancer anorexia-cachexia syndrome.

Fig. 1

Chemical structure of anamorelin

Fig. 2

a Concentration-response curve of ghrelin and ANAM in the HEK293/GRLN FLIPR assay. Data are shown as the mean ± SE (n = 3). b Concentration-response curve of ghrelin and ANAM in the binding assay using HEK293/GRLN membrane preparations and [¹²⁵I] ghrelin. Data are shown as the mean ± SE (n = 3). c The effect of ANAM in rat pituitary cell assay in doses ranging from 0.01 nM to 10 μM (n = 4). ANAM anamorelin; FLIPR fluorescent imaging plate reader; GH growth hormone; RLUs relative light units; SE standard error

Fig. 3

a Increasing effect of ANAM on food intake and body weight following repeated oral administration in rats. Data are shown as the mean ± SE. b Cumulative effect of ANAM on food intake and body weight following 7 days of repeated oral administration in rats. Data are shown as the mean ± SE; *P < 0.05 compared to control group. ANAM anamorelin; SE standard error

Fig. 4

Stimulatory effect of ANAM on growth hormone secretion following a single oral administration in rats. Data are shown as the mean ± SE; *P < 0.05 compared to control group. ANAM anamorelin; AUC _0–6h area under the GH concentration curve from 0 to 6 h; GH growth hormone; SE standard error

Fig. 5

a Acute GH release following a single dose of ANAM (3.5 mg/kg) in pigs. b GH response on Day 1 and on Day 7 following repeated daily ANAM dosing (1.5 mg/kg/day) in pigs. ANAM anamorelin; GH growth hormone

Fig. 6

Mean IGF-1 plasma concentrations in pigs during repeated dosing with ANAM (1 mg/kg/day) or control for 7 days. Pigs were either first treated with ANAM from Days 1–7 and then crossed over to control from Days 8–14 (solid symbols), or vice versa (open symbols). The change in mean IGF-1 levels in the individual animals is shown and the mean ± SE in the ANAM or control periods is represented by the gray diamonds. ANAM anamorelin; IGF-1 insulin-like growth factor 1; SE standard error