Thorough QT/QTc Study Evaluating the Effect of Macimorelin on Cardiac Safety Parameters in Healthy Participants.

Macimorelin is an orally active growth hormone secretagogue indicated for the diagnosis of adult growth hormone deficiency. The primary objective of this study was to evaluate the effect of macimorelin on the baseline and placebo-corrected mean QT interval using Fridericia's formula (ΔΔQTcF). Secondary objectives were to determine QTcF for moxifloxacin; evaluate the effects of macimorelin on other cardiac intervals (PR, QRS, RR), heart rate, and electrocardiogram morphology parameters; characterize pharmacokinetics; and assess safety of macimorelin. The phase 1 thorough QT/QTc study, designed according to the International Council for Harmonisation E14 guideline, was a randomized, placebo-controlled, double-blind, 3-way complete crossover study comparing the effect of macimorelin 2.0 mg/kg with placebo and moxifloxacin 400 mg (positive control). Data were collected over a 3-month span from male (n=36) and female participants (n=24) aged 18 to 55 years with body mass index between 18.5 and 30.0 kg/m2 . Fifty-six participants received all 3 treatments. The ΔΔQTcF for macimorelin showed a prolongation with a maximum mean value of 9.61 milliseconds (2-sided 90% confidence interval, 7.81 milliseconds and 11.41 milliseconds) at 4 hours after dosing. The 2-sided 90% confidence interval of this value also exceeded the 10 millisecond threshold at 3 hours after dosing. Assay sensitivity was confirmed with moxifloxacin. Other electrocardiogram parameters evaluated were not influenced by macimorelin. Macimorelin did not raise other safety concerns and was well tolerated. In summary, a single supratherapeutic dose of macimorelin prolonged cardiac repolarization according to the regulatory guideline.

Safety, tolerability, pharmacokinetics, and pharmacodynamics of macimorelin in healthy adults: Results of a single-dose, randomized controlled study.

OBJECTIVE: Macimorelin is an orally active ghrelin receptor agonist indicated for the diagnosis of adult growth hormone (GH) deficiency in the United States. This phase 1 study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of single ascending doses of macimorelin (including a supratherapeutic dose to be used in a thorough QT trial) in healthy adults. DESIGN: Participants were randomized to receive macimorelin 0.5, 1.0, or 2.0 mg/kg or placebo in 1 of 3 sequential ascending-dose cohorts. Blood samples for pharmacokinetic and pharmacodynamic assays were collected pre-dose and at specified time points over a 24-h period. Pharmacokinetic parameters assessed included area under the concentration-time curve (AUC), maximum concentration (Cmax) of macimorelin in plasma, time to Cmax (tmax), and terminal elimination half-life (t1/2). Pharmacodynamic assessments evaluated levels of GH, adrenocorticotropic hormone, thyroid-stimulating hormone, cortisol, and prolactin. Safety was assessed based on treatment-emergent adverse events (TEAEs), vital signs, 12­lead electrocardiograms, and laboratory parameters. RESULTS: A total of 28 healthy adults were enrolled and completed the study. Macimorelin AUC and Cmax showed less than dose-proportional increases following administration of 0.5 and 1.0 mg/kg. Mean t1/2 was 3.51 h for macimorelin 0.5 and 1.0 mg/kg and 8.29 h for macimorelin 2.0 mg/kg; median tmax occurred at 0.5 to 0.75 h. GH levels increased after dosing, with a tmax of 0.75 h to 1.0 h. Mean GH Cmax was similar with the macimorelin 0.5- and 1.0-mg/kg doses (31.9 and 37.8 ng/mL, respectively) and was ~50% lower with macimorelin 2.0 mg/kg (18.4 ng/mL). Transient increases were observed in adrenocorticotropic hormone, cortisol, and prolactin, which were not dose related. A total of 19 TEAEs were reported in 35.7% (10/28) of participants; all TEAEs were mild or moderate and resolved. A total of 12 drug-related TEAEs were reported in 8 participants. Headache was the most common drug-related TEAE. All doses of macimorelin prolonged mean QTcF by 10 to 11 ms. There were no clinically meaningful changes in vital signs or laboratory parameters. CONCLUSIONS: Single-dose administration of macimorelin 0.5 to 2.0 mg/kg was well tolerated. Macimorelin exposure was less than dose-proportional over the dose range studied. Administration of macimorelin stimulated GH production, with the greatest increases observed in the macimorelin 0.5- and 1.0-mg/kg groups.

Macimorelin as a Diagnostic Test for Adult GH Deficiency.

Purpose: The diagnosis of adult GH deficiency (AGHD) is challenging and often requires confirmation with a GH stimulation test (GHST). The insulin tolerance test (ITT) is considered the reference standard GHST but is labor intensive, can cause severe hypoglycemia, and is contraindicated for certain patients. Macimorelin, an orally active GH secretagogue, could be used to diagnose AGHD by measuring stimulated GH levels after an oral dose. Materials and Methods: The present multicenter, open-label, randomized, two-way crossover trial was designed to validate the efficacy and safety of single-dose oral macimorelin for AGHD diagnosis compared with the ITT. Subjects with high (n = 38), intermediate (n = 37), and low (n = 39) likelihood for AGHD and healthy, matched controls (n = 25) were included in the efficacy analysis. Results: After the first test, 99% of macimorelin tests and 82% of ITTs were evaluable. Using GH cutoff levels of 2.8 ng/mL for macimorelin and 5.1 ng/mL for ITTs, the negative agreement was 95.38% (95% CI, 87% to 99%), the positive agreement was 74.32% (95% CI, 63% to 84%), sensitivity was 87%, and specificity was 96%. On retesting, the reproducibility was 97% for macimorelin (n = 33). In post hoc analyses, a GH cutoff of 5.1 ng/mL for both tests resulted in 94% (95% CI, 85% to 98%) negative agreement, 82% (95% CI, 72% to 90%) positive agreement, 92% sensitivity, and 96% specificity. No serious adverse events were reported for macimorelin. Conclusions: Oral macimorelin is a simple, well-tolerated, reproducible, and safe diagnostic test for AGHD with accuracy comparable to that of the ITT. A GH cutoff of 5.1 ng/mL for the macimorelin test provides an excellent balance between sensitivity and specificity.

Effects of hepatic dysfunction on the single-dose pharmacokinetics of fesoterodine.

Fesoterodine, a new antimuscarinic for the treatment of overactive bladder, is rapidly and extensively hydrolyzed by nonspecific esterases to its principal active moiety, 5-hydroxymethyl tolterodine (5-HMT). The elimination of 5-HMT involves metabolism and renal excretion. The plasma and urinary pharmacokinetics of 5-HMT and its inactive carboxy (SPM 5509), N-desisopropyl (SPM 7789), and carboxy-N-desisopropyl (SPM 7790) metabolites were investigated after a single oral dose of 8 mg of fesoterodine in 8 male subjects with moderate hepatic cirrhosis (Child-Turcotte-Pugh class B) and 8 matched healthy controls. The estimated mean ratios (95% confidence interval) of the area under the curve extrapolated to infinity after dosing (AUC(0-∞)), cumulative urinary excretion up to 48 hours after dosing (Ae(0-48)), maximum observed concentration (C(max)), and apparent terminal disposition half-life (t(1/2)) of 5-HMT for cirrhotic and healthy subjects were 2.2 (1.5-3.1), 2.5 (1.7-3.8), 1.4 (1.0-1.9), and 1.1 (0.8-1.3), respectively. In subjects with hepatic cirrhosis, AUC(0-∞) and Ae(0-48) of 5-HMT increased approximately 2-fold; the increase in C(max) was smaller, and t(1/2) was unaffected. AUC and C(max) of the inactive carboxy metabolites, SPM 5509 and SPM 7790, were reduced reciprocally by about 50%, whereas exposure to the dealkylated metabolite, SPM 7789, increased about 2-fold. Fesoterodine 8 mg was equally well tolerated in both groups. The results indicate that moderate hepatic cirrhosis reduces 5-HMT clearance, with an apparent effect on the carboxylation pathway and not on dealkylation.

Evaluation of drug-drug interactions with fesoterodine.

PURPOSE: To assess drug-drug interactions of fesoterodine with cytochrome P450 (CYP) 3A4 inhibitor (ketoconazole), inducer (rifampicin), and substrates (ethinylestradiol and levonorgestrel). METHODS: Effects of ketoconazole 200 mg twice daily and rifampicin 600 mg twice daily on fesoterodine 8 mg once daily were investigated in CYP2D6 extensive metabolizers (EMs) and poor metabolizers (PMs) based on 5-hydroxymethyl tolterodine (5-HMT) pharmacokinetics (principal active fesoterodine metabolite and CYP3A4 substrate). Effects of fesoterodine 8 mg versus placebo once daily on ethinylestradiol and levonorgestrel were investigated based on oral contraceptive pharmacokinetics and on pharmacodynamic effects on progesterone, luteinizing hormone, follicle-stimulating hormone, and estradiol plasma levels. RESULTS: Compared with fesoterodine alone, coadministration of fesoterodine with ketoconazole resulted in increases in mean 5-HMT maximum concentration in plasma (C(max); from 3.0 to 6.0 ng/mL in EMs and from 6.4 to 13.4 ng/mL in PMs) and mean area under the plasma concentration time curve (AUC; from 38.2 to 88.3 ng h/mL in EMs and 88.3 to 217.2 ng h/mL in PMs). Coadministration of festerodine with rifampicin resulted in decreases in mean 5-HMT C(max) (from 5.2 to 1.5 ng/mL in EMs and from 6.8 to 1.9 ng/mL in PMs) and mean AUC (from 62.4 to 14.4 ng h/mL in EMs and from 87.8 to 19.6 ng h/mL in PMs). Fesoterodine did not affect oral contraceptive pharmacokinetics or pharmacodynamics or the suppression of ovulation. CONCLUSIONS: Fesoterodine dosage should not exceed 4 mg once daily when taken concomitantly with potent CYP3A4 inhibitors. Coadministration of CYP3A4 inducers with fesoterodine may produce subtherapeutic 5-HMT exposures. No dose adjustment is necessary for concomitant use of fesoterodine with oral contraceptives.

Assessment of the effects of renal impairment on the pharmacokinetic profile of fesoterodine.

The effects of renal impairment on the pharmacokinetics of a single 4-mg oral dose of fesoterodine are assessed in 8 healthy subjects and 8 subjects each with mild, moderate, or severe renal impairment. Compared with findings in healthy subjects, the maximum concentration in plasma of 5-hydroxymethyl tolterodine (5-HMT), the principal active moiety of fesoterodine, increases by 1.4-, 1.5-, and 2.0-fold and area under the curve increases by 1.6-, 1.8-, and 2.3-fold in subjects with mild, moderate, and severe renal impairment, respectively. There is a clear correlation between the renal clearance of 5-HMT and creatinine clearance. The median time of observed maximum drug concentration (5-6 hours) and mean terminal half-life (6-7 hours) of 5-HMT are unaffected by renal impairment. The unbound fraction of 5-HMT in plasma (0.43-0.54 ng/mL) is comparable across all groups. In conclusion, because of the involvement of both metabolic and renal elimination pathways, only modest increases in 5-HMT exposures are observed in patients with renal impairment.