Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1   Pharmacodynamic properties

Pharmacotherapeutic group: Other drugs for constipation, ATC code: A06AX05.

Mechanism of action
Prucalopride is a dihydrobenzofurancarboxamide with gastrointestinal prokinetic activities.
Prucalopride is a selective, high affinity serotonin (5-HT4) receptor agonist, which is likely to explain its prokinetic effects. In vitro, only at concentrations exceeding its 5-HT4 receptor affinity by at least 150-fold, affinity for other receptors was detected. In rats, prucalopride in vivo, at doses above 5 mg/kg (at and above 30-70 times the clinical exposure), induced hyperprolactinaemia caused by an antagonistic action at the D2 receptor.

In dogs, prucalopride alters colonic motility patterns via serotonin 5-HT4 receptor stimulation: it stimulates proximal colonic motility, enhances gastroduodenal motility and accelerates delayed gastric emptying. Furthermore, giant migrating contractions are induced by prucalopride. These are equivalent to the colonic mass movements in humans, and provide the main propulsive force to defecation. In dogs, the effects observed in the gastrointestinal tract are sensitive to blockade with selective 5-HT4 receptor antagonists illustrating that the observed effects are exerted via selective action on 5-HT4 receptors.

These pharmacodynamic effects of prucalopride have been confirmed in human subjects with chronic constipation using manometry in an open-label, randomised, crossover, reader-blinded study investigating the effect of prucalopride 2 mg and an osmotic laxative on colon motility as determined by the number of colonic high-amplitude propagating contractions (HAPCs, also known as giant migrating contractions). Compared with a constipation treatment working through osmotic action, prokinetic stimulation with prucalopride increased colonic motility as measured by the number of HAPCs during the first 12 hours after intake of the investigational product. The clinical significance or benefit of this mechanism of action when compared with other laxatives has not been investigated.

Clinical efficacy and safety

Adult population
The efficacy of Resolor was established in three multicentre, randomised, double-blind, 12-week placebo-controlled studies in subjects with chronic constipation (n=1,279 on Resolor, 1,124 females, 155 males). The Resolor doses studied in each of these three studies included 2 mg and 4 mg once daily. The primary efficacy endpoint was the proportion (%) of subjects that reached normalisation of bowel movements defined as an average of three or more spontaneous, complete bowel movements (SCBM) per week over the 12-week treatment period.

The proportion of female patients in whom laxatives fail to provide adequate relief treated with the recommended dose of 2 mg Resolor (n=458) that reached an average of ≥3 SCBM per week was 31.0% (week 4) and 24.7% (week 12), versus 8.6% (week 4) and 9.2% (week 12) on placebo. A clinically meaningful improvement of ≥1 SCBM per week, the most important secondary efficacy endpoint, was achieved in 51.0% (week 4) and 44.2% (week 12) treated with 2 mg Resolor versus 21.7% (week 4) and 22.6% (week 12) of placebo patients.

The effect of Resolor on spontaneous bowel movements (SBM) also proved to be statistically superior to placebo for the portion of patients that had an increase of ≥1 SBM/week over the 12-week treatment period. At week 12, 68.3% of patients treated with 2 mg prucalopride had an average increase of ≥1 SBM/week versus 37.0% of placebo patients (p<0.001 vs placebo).

In all three studies, treatment with Resolor also resulted in significant improvements in a validated and disease specific set of symptom measures (PAC-SYM), including abdominal (bloating, discomfort, pain and cramps), stool (incomplete bowel movements, false alarm, straining, too hard, too small) and rectal symptoms (painful bowel movements, burning, bleeding/tearing), determined at week 4 and week 12. At week 4, the proportion of patients with an improvement of ≥1 versus baseline in the PAC-SYM abdominal, stool, and rectal symptom subscales was 41.3%, 41.6%, and 31.3% respectively in patients treated with prucalopride 2 mg compared with 26.9%, 24.4% and 22.9% in patients on placebo. Similar results were observed at Week 12: 43.4%, 42.9%, and 31.7% respectively in 2 mg Resolor patients versus 26.9%, 27.2%, and 23.4% in placebo patients (p<0.001 vs placebo).

A significant benefit on a number of Quality of Life measures, such as degree of satisfaction with treatment and with bowel habits, physical and psychosocial discomfort and worries and concerns, was also observed at both the 4 and 12 week assessment time points. At Week 4, the proportion of patients with an improvement of ≥1 versus baseline in the Patient Assessment of Constipation-Quality of Life satisfaction subscale (PAC-QOL) was 47.7% in patients treated with Resolor 2 mg compared with 20.2% in patients on placebo. Similar results were observed at Week 12: 46.9% in 2 mg Resolor patients versus 19.0% in placebo patients (p<0.001 vs placebo).

In addition, the efficacy, safety and tolerability of Resolor in male patients with chronic constipation were evaluated in a 12-week, multi-centre, randomised, double-blind, placebo– controlled study (N=370). The primary endpoint of the study was met: a statistically significantly higher percentage of subjects in the Resolor group (37.9%) had an average of ≥3 SCBMs/week compared with subjects in the placebo treatment group (17.7%) (p<0.0001) over the 12-week double-blind treatment period. The safety profile of Resolor was consistent with that seen in female patients.

Long-term study
The efficacy and safety of Resolor in patients (aged ≥18 or older) with chronic constipation, were evaluated in a 24 week multicentre, randomised, double-blind, placebo controlled study (N=361). The proportion of patients with an average weekly frequency of ≥3 Spontaneous Complete Bowel Movements (SCBMs) per week (i.e., responders) over the 24-week double-blind treatment phase was not statistically different (p=0.367) between the Resolor (25.1%) and placebo (20.7%) treatment groups. The difference between treatment groups in the average weekly frequency of ≥3 SCBMs per week was not statistically significant over Weeks 1-12 which is inconsistent with the 5 other multicentre, randomised, double-blind, 12-week placebo controlled studies demonstrating efficacy at this timepoint in adult patients.
The study is therefore considered to be inconclusive with respect to efficacy. However, the totality of the data including the other double-blind placebo controlled 12 week studies support the efficacy of Resolor. The safety profile of prucalopride in this 24 week study was consistent with that seen in the previous 12 week studies.

Resolor has been shown not to cause rebound phenomena, nor to induce dependency.

TQT study
A thorough QT study was performed to evaluate the effects of Resolor on the QT interval at therapeutic (2 mg) and supratherapeutic doses (10 mg) and compared with the effects of placebo and a positive control. This study did not show significant differences between Resolor and placebo at either dose, based on mean QT measurements and outlier analysis.
This confirmed the results of two placebo controlled QT studies. In double-blind clinical studies, the incidence of QT-related adverse events and ventricular arrhythmias was low and comparable to placebo.

Paediatric population
The efficacy and safety of Resolor in paediatric patients (aged 6 months to 18 years) with functional constipation, were evaluated in an 8-week double-blind, placebo-controlled trial (N=213), followed by a 16 week open-label comparator-controlled (Polyethylene glycol 4000) study of up to 24 weeks (N=197). The starting dose administered was 0.04 mg/kg/day titrated between 0.02 and 0.06 mg/kg/day (to a maximum of 2 mg daily) for children weighing ≤50 kg given as an oral solution of Resolor or matching placebo. Children weighing >50 kg received 2 mg/day Resolor tablets or matching placebo.

Response to the treatment was defined as having an average of ≥3 spontaneous bowel movements (SBMs) per week and an average number of faecal incontinence episodes of ≤1 per 2 weeks. The results of the study showed no difference in efficacy between Resolor and placebo with response rates of 17% and 17.8% respectively (P=0.9002). Resolor was generally well tolerated. The incidence of subjects with at least 1 treatment-emergent adverse event (TEAE) was similar between the Resolor treatment group (69.8%) and the placebo treatment group (60.7%). Overall, the safety profile of Resolor in children was the same as in adults.

Pharmacokinetic Properties

5.2   Pharmacokinetic properties

Absorption
Prucalopride is rapidly absorbed; after a single oral dose of 2 mg in healthy subjects, Cmax was attained in 2-3 hours. The absolute oral bioavailability is >90%. Concomitant intake of food does not influence the oral bioavailability of prucalopride.

Distribution
Prucalopride is extensively distributed, and has a steady-state volume of distribution (Vdss) of 567 litres. The plasma protein binding of prucalopride is about 30%.

Biotransformation
Metabolism is not the major route of elimination of prucalopride. In vitro, human liver metabolism is very slow and only minor amounts of metabolites are found. In an oral dose study with radiolabelled prucalopride in man, small amounts of seven metabolites were recovered in urine and faeces. The quantitatively most important metabolite in excreta, R107504, accounted for 3.2% and 3.1% of the dose in urine and faeces, respectively. Other metabolites identified and quantified in urine and faeces were R084536 (formed by N-dealkylation) accounting for 3% of the dose and products of hydroxylation (3% of the dose) and N-oxidation (2% of the dose). Unchanged active substance made up about 92-94% of the total radioactivity in plasma. R107504, R084536 and R104065 (formed by O-demethylation) were identified as minor plasma metabolites.

Elimination
A large fraction of the active substance is excreted unchanged (60-65% of the administered dose in urine and about 5% in faeces). Renal excretion of unchanged prucalopride involves both passive filtration and active secretion. The plasma clearance of prucalopride averages 317 ml/min. Its terminal half-life is about one day. Steady-state is reached within three to four days. On once daily treatment with 2 mg prucalopride, steady-state plasma concentrations fluctuate between trough and peak values of 2.5 and 7 ng/ml, respectively. The accumulation ratio after once daily dosing ranged from 1.9 to 2.3. The pharmacokinetics of prucalopride is dose-proportional within and beyond the therapeutic range (tested up to 20 mg). Prucalopride o.d. displays time-independent kinetics during prolonged treatment.

Special populations

Population pharmacokinetics
A population pharmacokinetic analysis showed that the apparent total clearance of prucalopride was correlated with creatinine clearance, but that age, body weight, sex or race had no influence.

Older people
After once daily dosing of 1 mg, peak plasma concentrations and AUC of prucalopride in older people were 26% to 28% higher than in young adults. This effect can be attributed to a diminished renal function in older people.

Renal impairment
Compared to subjects with normal renal function, plasma concentrations of prucalopride after a single 2 mg dose were on average 25% and 51% higher in subjects with mild (ClCR 50- 79 ml/min) and moderate (ClCR 25-49 ml/min) renal impairment, respectively. In subjects with severe renal impairment (ClCR ≤24 ml/min), plasma concentrations were 2.3 times the levels in healthy subjects (see section 4.2 and 4.4).

Hepatic impairment
Non-renal elimination contributes to about 35% of total elimination. In a small pharmacokinetic study, the Cmax and AUC of prucalopride were, on average, 10-20% higher in patients with moderate to severe hepatic impairment compared with healthy subjects (see sections 4.2 and 4.4).