Adempas

Adempas Mechanism of Action

riociguat

Manufacturer:

Bayer

Distributor:

Zuellig
/
Four Star
Full Prescribing Info
Action
Pharmacotherapeutic group: Antihypertensives for pulmonary arterial hypertension. ATC code: C02KX05.
Pharmacology: Pharmacodynamics: Mechanism of action: Riociguat is a stimulator of soluble guanylate cyclase (sGC), an enzyme in the cardiopulmonary system and the receptor for nitric oxide (NO). When NO binds to sGC, the enzyme catalyses synthesis of the signalling molecule cyclic guanosine monophosphate (cGMP). Intra-cellular cGMP plays an important role in regulating processes that influence vascular tone, proliferation, fibrosis, and inflammation.
Pulmonary hypertension is associated with endothelial dysfunction, impaired synthesis of NO and insufficient stimulation of the NO-sGC-cGMP pathway.
Riociguat has a dual mode of action. It sensitises sGC to endogenous NO by stabilising the NO-sGC binding. Riociguat also directly stimulates sGC independently of NO.
Riociguat restores the NO-sGC-cGMP pathway and leads to increased generation of cGMP.
Pharmacodynamic effects: Riociguat restores the NO-sGC-cGMP pathway resulting in a significant improvement of pulmonary vascular haemodynamics and an increase in exercise ability.
There is a direct relationship between riociguat plasma concentration and haemodynamic parameters such as systemic and pulmonary vascular resistance, systolic blood pressure and cardiac output.
Clinical efficacy and safety: Efficacy in patients with CTEPH: A randomised, double-blind, multi-national, placebo controlled, phase III study (CHEST-1) was conducted in 261 adult patients with inoperable chronic thromboembolic pulmonary hypertension (CTEPH) (72%) or persistent or recurrent CTEPH after pulmonary endarterectomy (PEA; 28%). During the first 8 weeks riociguat was titrated every 2-weeks based on the patient's systolic blood pressure and signs or symptoms of hypotension to the optimal individual dose (range 0.5 mg to 2.5 mg three times daily) which was then maintained for a further 8 weeks. The primary endpoint of the study was the placebo adjusted change from baseline in 6-minute walk distance (6MWD) at the last visit (week 16).
At the last visit, the increase in 6MWD in patients treated with riociguat was 46 m (95% confidence interval (CI): 25 m to 67 m; p<0.0001), compared to placebo. Results were consistent in the main sub-groups evaluated (ITT analysis, see table 1).

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Improvement in exercise capacity was accompanied by improvement in multiple clinically relevant secondary endpoints. These findings were in accordance with improvements in additional haemodynamic parameters. (See Table 2.)

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Adverse Events leading to discontinuation occurred at a similar frequency in both treatment groups (riociguat individual dose titration (IDT) 1.0-2.5 mg, 2.9%; placebo, 2.3%).
Long-term treatment: An open-label extension study (CHEST-2) included 237 patients who had completed CHEST-1. In CHEST-2, all patients received an individualised riociguat dose up to 2.5 mg three times daily.
The mean change in 6MWD from baseline to week 12 (last observation until week 12) in CHEST-2 (28 weeks on-study for CHEST-1 + CHEST-2) was 57 m in the former 1.0-2.5 mg riociguat group and 43 m in the former placebo group. Improvements in 6MWD persisted at 2 years in CHEST-2. Mean change from baseline for the overall population (N=237) was 57 m at 6 months (n=218), 51 m at 9 months (n=219), 52 m at 12 months (n=209) and 48 m at 24 months (n=193).
The probability of survival at 1 year was 97%, at 2 years 93% and at 3 years 89%. Survival in patients of WHO functional class II at baseline at 1, 2 and 3 years was 97%, 94% and 90% respectively, and for patients of WHO functional class III at baseline was 97%, 93% and 88% respectively.
Efficacy in patients with PAH: A randomised, double-blind, multi-national, placebo controlled, phase III study (PATENT-1) was conducted in 443 adult patients with PAH (riociguat individual dose titration up to 2.5 mg three times daily: n=254, placebo: n=126, riociguat "capped" dose titration (CT) up to 1.5 mg (exploratory dose arm, no statistical testing performed; n=63)). Patients were either treatment-naïve (50%) or pre-treated with ERA (43%) or a prostacyclin analogue (inhaled (iloprost), oral (beraprost) or subcutaneous (treprostinil); 7%) and had been diagnosed with idiopathic or heritable PAH (63.4%), PAH associated with connective tissue disease (25.1%) and congenital heart disease (7.9%).
During the first 8 weeks riociguat was titrated every 2-weeks based on the patient's systolic blood pressure and signs or symptoms of hypotension to the optimal individual dose (range 0.5 mg to 2.5 mg three times daily), which was then maintained for a further 4 weeks. The primary endpoint of the study was placebo-adjusted change from baseline in 6MWD at the last visit (week 12).
At the last visit the increase in 6MWD with riociguat individual dose titration (IDT) was 36 m (95% CI: 20 m to 52 m; p<0.0001) compared to placebo. Treatment-naïve patients (n=189) improved by 38 m, and pre-treated patients (n=191) by 36 m (ITT analysis, see table 3). Further exploratory subgroup analysis revealed a treatment effect of 26 m, (95% CI: 5 m to 46 m) in patients pre-treated with ERAs (n=167) and a treatment effect of 101 m (95% CI: 27 m to 176 m) in patients pre-treated with prostacyclin analogues (n=27). (See Table 3.)

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Improvement in exercise capacity was accompanied by consistent improvement in multiple clinically-relevant secondary endpoints. These findings were in accordance with improvements in additional haemodynamic parameters (see table 4).

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Riociguat-treated patients experienced a significant delay in time to clinical worsening versus placebo-treated patients (p = 0.0046; Stratified log-rank test) (see table 5).

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Patients treated with riociguat showed significant improvement in Borg CR 10 dyspnoea score (mean change from baseline (SD): riociguat -0.4 (2), placebo 0.1 (2); p = 0.0022).
Adverse Events leading to discontinuation occurred less frequently in both riociguat treatment groups than in the placebo group (riociguat IDT 1.0-2.5 mg, 3.1%; riociguat CT 1.6%; placebo, 7.1%).
Long-term treatment: An open-label extension study (PATENT-2) included 396 patients who had completed PATENT-1 at the cut-off-date. In PATENT-2, all patients received an individualised riociguat dose up to 2.5 mg three times daily. The mean change in 6MWD from baseline to week 12 (last observation until week 12) in PATENT-2 (24 weeks on-study for PATENT-1 + PATENT-2) was 52 m in the former 1.0-2.5 mg riociguat group, 45 m in the former placebo group and 52 m in the former 1.0-1.5 mg riociguat group. Improvements in 6MWD persisted at 2 years in PATENT-2. Mean change from baseline for the overall population (N=396) was 53 m at 6 months (n=366), 52 m at 9 months (n=354), 50 m at 12 months (n=351) and 46 m at 24 months (n=316).
The probability of survival at 1 year was 97%, at 2 years 93% and at 3 years 88%. Survival in patients of WHO functional class II at baseline at 1, 2 and 3 years was 98%, 96% and 93% respectively, and for patients of WHO functional class III at baseline was 96%, 91% and 84% respectively.
Patients with pulmonary hypertension associated with idiopathic interstitial pneumonias (PH-IIP): A randomised, double blind, placebo-controlled phase II study (RISE-IIP) to evaluate the efficacy and safety of riociguat in patients with symptomatic pulmonary hypertension associated with idiopathic interstitial pneumonias (PH-IIP) was terminated early due to an increased risk of mortality and serious adverse events in patients treated with riociguat and a lack of efficacy. More patients taking riociguat died (11% vs. 4%) and had serious adverse events (37% vs. 23%) during the main phase. In the long-term extension, more patients who switched from the placebo group to riociguat (21%) died than those who continued in the riociguat group (3%).
Riociguat is therefore contraindicated in patients with pulmonary hypertension associated with idiopathic interstitial pneumonias (see Contraindications).
Paediatric population: The European Medicines Agency has deferred the obligation to submit the results of studies with Adempas in one or more subsets of the paediatric population in the treatment of pulmonary hypertension.
See Dosage & Administration for information on paediatric use.
Pharmacokinetics: Absorption: The absolute bioavailability of riociguat is high (94%). Riociguat is rapidly absorbed with maximum concentrations (Cmax) appearing 1-1.5 hours after tablet intake. Intake with food reduced riociguat AUC slightly, Cmax was reduced by 35%.
Bioavailability (AUC and Cmax) is comparable for Adempas administered orally as a crushed tablet suspended in applesauce or in water compared to a whole tablet (see Dosage & Administration).
Distribution: Plasma protein binding in humans is high at approximately 95%, with serum albumin and alpha 1-acidic glycoprotein being the main binding components. The volume of distribution is moderate with volume of distribution at steady state being approximately 30 L.
Biotransformation: N-demethylation, catalysed by CYP1A1, CYP3A4, CYP3A5 and CYP2J2 is the major biotransformation pathway of riociguat leading to its major circulating active metabolite M-1 (pharmacological activity: 1/10th to 1/3rd of riociguat) which is further metabolised to the pharmacologically inactive N-glucuronide.
CYP1A1 catalyses the formation of riociguat's main metabolite in liver and lungs and is known to be inducible by polycyclic aromatic hydrocarbons, which, for example, are present in cigarette smoke.
Elimination: Total riociguat (parent compound and metabolites) is excreted via both renal (33-45%) and biliary/faecal routes (48-59%). Approximately 4-19% of the administered dose was excreted as unchanged riociguat via the kidneys. Approximately 9-44% of the administered dose was found as unchanged riociguat in faeces.
Based on in vitro data riociguat and its main metabolite are substrates of the transporter proteins P-gp (P-glycoprotein) and BCRP (breast cancer resistance protein). With a systemic clearance of about 3-6 L/h, riociguat can be classified as a low-clearance drug. Elimination half-life is about 7 hours in healthy subjects and about 12 hours in patients.
Linearity: Riociguat pharmacokinetics are linear from 0.5 to 2.5 mg. Inter-individual variability (CV) of riociguat exposure (AUC) across all doses is approximately 60%.
Special populations: Gender: Pharmacokinetic data reveal no relevant differences due to gender in the exposure to riociguat.
Paediatric population: No studies have been conducted to investigate the pharmacokinetics of riociguat in paediatric patients.
Elderly population: Elderly patients (65 years or older) exhibited higher plasma concentrations than younger patients, with mean AUC values being approximately 40% higher in elderly, mainly due to reduced (apparent) total and renal clearance.
Inter-ethnic differences: Pharmacokinetic data reveal no relevant inter-ethnic differences.
Different weight categories: Pharmacokinetic data reveal no relevant differences due to weight in the exposure to riociguat.
Hepatic impairment: In cirrhotic patients (non-smokers) with mild hepatic impairment (classified as Child Pugh A) riociguat mean AUC was increased by 35% compared to healthy controls, which is within normal intra-individual variability. In cirrhotic patients (non-smokers) with moderate hepatic impairment (classified as Child Pugh B), riociguat mean AUC was increased by 51% compared to healthy controls. There are no data in patients with severe hepatic impairment (classified as Child Pugh C).
Patients with ALT > 3 x ULN and bilirubin > 2 x ULN were not studied (see Precautions).
Renal impairment: Overall, mean dose- and weight- normalised exposure values for riociguat were higher in subjects with renal impairment compared to subjects with normal renal function. Corresponding values for the main metabolite were higher in subjects with renal impairment compared to healthy subjects. In non-smoking individuals with mild (creatinine clearance 80-50 mL/min), moderate (creatinine clearance <50-30 mL/min) or severe (creatinine clearance <30 mL/min) renal impairment, riociguat plasma concentrations (AUC) were increased by 53%, 139% or 54%, respectively.
Data in patients with creatinine clearance <30 mL/min are limited and there are no data for patients on dialysis.
Due to the high plasma protein binding riociguat is not expected to be dialysable.
Toxicology: Preclinical safety data: Non-clinical data revealed no specific hazard for humans based on conventional studies of safety pharmacology, single dose toxicity, phototoxicity, genotoxicity and carcinogenicity.
Effects observed in repeat-dose toxicity studies were mainly due to the exaggerated pharmacodynamic activity of riociguat (haemodynamic and smooth muscle relaxing effects).
In growing, juvenile and adolescent rats, effects on bone formation were seen. In juvenile rats, the changes consisted of thickening of trabecular bone and of hyperostosis and remodeling of metaphyseal and diaphyseal bone, whereas in adolescent rats an overall increase of bone mass was observed. No such effects were observed in adult rats.
In a fertility study in rats, decreased testes weights occurred at systemic exposure of about 7-fold of human exposure, whereas no effects on male and female fertility were seen. Moderate passage across the placental barrier was observed. Developmental toxicity studies in rats and rabbits have shown reproductive toxicity of riociguat. In rats, an increased rate of cardiac malformation was observed as well as a reduced gestation rate due to early resorption at maternal systemic exposure of about 7-fold of human exposure (2.5 mg three times daily). In rabbits, starting at systemic exposure of about 3-fold of human exposure (2.5 mg three times daily) abortion and foetal toxicity were seen.
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