Effect of opicapone and entacapone upon levodopa pharmacokinetics during three daily levodopa administrations

Levodopa Dose Equivalency in Parkinson's Disease: Updated Systematic Review and Proposals

BACKGROUND

To compare drug regimens across clinical trials in Parkinson's disease (PD) conversion formulae between antiparkinsonian drugs have been developed. These are reported in relation to levodopa as the benchmark drug in PD pharmacotherapy as 'levodopa equivalent dose' (LED). Currently, the LED conversion formulae proposed in 2010 by Tomlinson et al. based on a systematic review are predominantly used. However, new drugs with established and novel mechanisms of action and novel formulations of longstanding drugs have been developed since 2010. Therefore, consensus proposals for updated LED conversion formulae are needed.

OBJECTIVES

To update LED conversion formulae based on a systematic review.

METHODS

The MEDLINE, CENTRAL, and Embase databases were searched from January 2010 to July 2021. Additionally, in a standardized process according to the GRADE grid method, consensus proposals were issued for drugs with scarce data on levodopa dose equivalency.

RESULTS

The systematic database search yielded 3076 articles of which 682 were eligible for inclusion in the systematic review. Based on these data and the standardized consensus process, we present proposals for LED conversion formulae for a wide range of drugs that are currently available for the pharmacotherapy of PD or are expected to be introduced soon.

CONCLUSIONS

The LED conversion formulae issued in this Position Paper will serve as a research tool to compare the equivalence of antiparkinsonian medication across PD study cohorts and facilitate research on the clinical efficacy of pharmacological and surgical treatments as well as other non-pharmacological interventions in PD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Opicapone Pharmacokinetics and Effects on Catechol- O -Methyltransferase Activity and Levodopa Pharmacokinetics in Patients With Parkinson Disease Receiving Carbidopa/Levodopa

OBJECTIVES

Levodopa (LD) administered with dopa decarboxylase inhibitor is predominantly metabolized in the periphery by catechol- O -methyltransferase (COMT) to 3- O -methyldopa (3-OMD). Catechol- O -methyltransferase inhibition can improve treatment outcomes by decreasing variability in circulating LD concentrations. Opicapone is a once-daily COMT inhibitor approved in the US adjunctive to carbidopa (CD)/LD in patients with Parkinson disease experiencing "OFF" episodes. This study aimed to evaluate the pharmacokinetics and pharmacodynamics of once-daily opicapone 50 mg adjunctive to CD/LD in patients with stable Parkinson disease.

METHODS

Once-daily opicapone 50 mg was administered the evenings of days 1 to 14. Participants were randomized to receive CD/LD (25/100 mg) every 3 or 4 hours (Q3H or Q4H). Participants received Q3H or Q4H CD/LD on days 1, 2, and 15 and their usual CD/LD regimen on other days. Serial blood samples were collected to determine plasma opicapone, LD, and 3-OMD concentrations and erythrocyte soluble COMT (S-COMT) activity. The effects of opicapone on S-COMT, LD, and 3-OMD were assessed. Mean (SD) values are presented.

RESULTS

Sixteen participants were enrolled. At steady-state (day 14), opicapone Cmax (peak plasma concentration) and AUC 0-last (area under the curve-time curve) were 459 ± 252 ng/mL and 2022 ± 783 ng/mL·h, respectively. Maximum COMT inhibition was 83.4 ± 4.9% of baseline on day 14. After opicapone administration, LD total AUC, peak concentration, and trough concentration increased; peak-to-trough fluctuation index decreased. Correspondingly, 3-OMD total AUC, peak concentration, and trough concentration decreased.

CONCLUSIONS

Adding once-daily opicapone 50 mg to LD resulted in marked and extended COMT inhibition, which increased systemic exposure to LD. These changes translated into higher trough concentrations and decreased peak-to-trough fluctuations for LD.

Effect of Opicapone on Levodopa Pharmacokinetics in Patients with Fluctuating Parkinson's Disease

BACKGROUND

Inhibiting catechol-O-methyltransferase extends the plasma half-life of levodopa, potentially allowing physicians to optimize the levodopa regimen in patients with Parkinson's disease (PD) experiencing motor fluctuations.

OBJECTIVES

To evaluate the effects of once-daily opicapone on levodopa plasma pharmacokinetics and motor response when added to two different levodopa dosing regimens.

METHODS

A total of 24 patients with PD and motor fluctuations were enrolled in an exploratory, open-label, modified cross-over trial. Participants first received levodopa/carbidopa 500/125 mg (five intakes) for 2 weeks and were then randomly assigned (1:1) to levodopa/carbidopa 400/100 mg given over either four or five daily intakes plus opicapone 50 mg for an additional 2 weeks. Levodopa 12-hour pharmacokinetics was the primary outcome (ie, excluding the effect of last/evening levodopa/carbidopa intake), with motor complications evaluated as secondary outcomes.

RESULTS

Over 12-hour pharmacokinetics and compared with five-intake levodopa/carbidopa 500/125 mg without opicapone, maximal levodopa concentrations were similar or nonsignificantly higher on both levodopa/carbidopa 400/100 mg regimens plus opicapone. Despite a 100 mg lower total levodopa/carbidopa daily dose, adding opicapone 50 mg at least doubled the levodopa plasma half-life and minimal concentrations, with a significant ≈30% increase in total exposure. The levodopa fluctuation index was only significantly lower for the five intakes plus opicapone regimen (difference of -71.8%; P < 0.0001). Modifications to levodopa pharmacokinetics were associated with decreased off time and increased on time.

CONCLUSIONS

Combining opicapone 50 mg with a 100 mg lower daily dose of levodopa provides higher levodopa bioavailability with avoidance of trough levels. Despite the lower levodopa dose, modifying the levodopa pharmacokinetic profile with opicapone was associated with decreased off time and increased on time. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Evaluating Opicapone as Add-on Treatment to Levodopa/DDCI in Patients with Parkinson's Disease

COMT (catechol-O-methyltransferase) inhibitors are key therapeutic agents in the management of motor fluctuations (MF) in patients with Parkinson's disease (PD). As levodopa/DDCI add-on therapy, their main benefit lies in increasing ON-time and reducing OFF-time for PD patients in the middle stages of the disease. Two of the three available COMT inhibitors, tolcapone and entacapone, have been approved for over two decades. Opicapone, a third-generation COMT inhibitor approved in 2016, was designed with the aim of overcoming specific challenges of the earlier generation compounds, specifically hepatotoxicity and short effect duration. This review aims at highlighting the specific properties and characteristics of opicapone, namely combining efficacy with good tolerability as demonstrated in the registration studies and since then confirmed under real-world conditions. Opicapone has been shown to be effective in patients with early, as well as late motor fluctuations. Whilst patients in the earlier Hoehn and Yahr stages benefit more than patients in later stages, the incidence of dyskinesia in patients with recent onset MF is around half that of patients with more established fluctuations. With the added advantage of a once-daily administration, this particular COMT inhibitor provides a simple, yet effective therapy for patients with Parkinson's disease and MF.

Opicapone as an Add-on to Levodopa in Patients with Parkinson's Disease Without Motor Fluctuations: Rationale and Design of the Phase III, Double-Blind, Randomised, Placebo-Controlled EPSILON Trial

Introduction

Levodopa remains the cornerstone treatment for Parkinson’s disease (PD) but its use is associated with the development of ‘wearing-off’ fluctuations and other motor and non-motor complications over time. Adding a catechol-O-methyltransferase (COMT) inhibitor to levodopa/dopa decarboxylase (DDC) inhibitor therapy reduces fluctuations in the profile of plasma levodopa levels following oral dosing, and can therefore be beneficial for the management of motor complications. The objective of the EPSILON study is to investigate the efficacy of opicapone (OPC; a third-generation, once-daily COMT inhibitor) in enhancing the clinical benefit of levodopa in patients in earlier stages of PD, without end-of-dose motor fluctuations.

Methods

EPSILON is a phase III, double-blind, randomised, placebo-controlled and parallel-group study, designed to evaluate the efficacy and safety of OPC as add-on to levodopa/DDC inhibitor therapy in patients with early PD who do not exhibit signs of motor complications. Eligible patients will be randomised (1:1) to receive OPC 50 mg or placebo, in addition to their existing levodopa/DDC inhibitor therapy, over a 24-week, double-blind treatment period, after which they will have the option of entering an additional 1-year, open-label extension period, during which all patients will receive OPC 50 mg.

Planned Outcomes

The primary efficacy endpoints are change in Movement Disorders Society Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) Part III total score from baseline to the end of the double-blind period (double-blind phase) and change in MDS-UPDRS Part IV total score from open-label baseline to the end of the open-label period (open-label phase). Secondary outcomes during the double-blind phase will include other measures of PD symptoms, including quality of life, non-motor symptoms, and development of motor fluctuations. Safety assessments will include evaluation of treatment-emergent adverse events, laboratory safety parameters, suicidality and impulse control disorders.

Trial Registration

European Union Drug Regulating Authorities Clinical Trials Database (number 2020-005011-52).

Effects of One-Day Application of Levodopa/Carbidopa/Entacapone versus Levodopa/Carbidopa/Opicapone in Parkinson’s Disease Patients

The catechol-O-methyltransferase inhibitors entacapone and opicapone prolong the efficacy of conventional oral levodopa/dopa decarboxylase inhibitor formulations through an increase in levodopa plasma bioavailability. Catechol-O-methyltransferase inhibitors influence the homocysteine metabolism associated with levodopa/dopa decarboxylase application. The objectives of this study were to compare the impact of additional single-day entacapone or opicapone intake on the pharmacokinetic plasma behaviour of levodopa, 3-O-methyldopa and total homocysteine in 15 Parkinson’s disease patients, with concomitant scoring of motor symptoms, under standardized conditions. The patients received opicapone plus two doses of 100 mg levodopa/carbidopa and, one week later, two doses of levodopa/carbidopa/entacapone or vice versa. Levodopa, 3-O-methyldopa and total homocysteine were determined with reversed-phase high-performance liquid chromatography. Levodopa bioavailability and its maximum concentration were higher with opicapone. The computed peak-to-trough difference was lower after the second levodopa administration with entacapone. The fluctuation index of levodopa did not differ between both conditions. 3-O-methyldopa decreased on both days. Homocysteine levels did not significantly vary between both conditions. A significant homocysteine decrease occurred with entacapone, but not with opicapone. Motor behaviour improved with entacapone, but not with opicapone. Opicapone baseline scores were significantly better, and thus the potential for the improvement in motor symptoms was lower compared with the entacapone condition. The higher levodopa bioavailability with opicapone suggests that it is more efficacious than entacapone for the amelioration of “off” phenomena in fluctuating patients when co-administered with a levodopa/dopa decarboxylase inhibitor regimen. Both compounds prevented an increase in homocysteine, which is a metabolic marker for an impaired capacity in the performance of methylation processes.

COMT Inhibitors in the Management of Parkinson's Disease

Levodopa treatment remains the gold standard for Parkinson's disease, but shortcomings related to the pharmacological profile, notably, oral administration and the consequent occurrence of motor complications, have led to the development of several add-on levodopa treatments or to research to improve the method of delivery. Motor fluctuations, and to a lesser extent non-motor fluctuations, concern half of the patients with Parkinson's disease after 5 years of disease and patients identified them as one of their most bothersome symptoms. Catechol-O-methyl transferase inhibitors (COMT-Is) are one of the recommended first-line levodopa add-on therapies for the amelioration of end-of dose motor fluctuations in patient with advanced Parkinson's disease. Currently, two peripheral COMT-Is are considered as first-line choices - entacapone (ENT), which was approved by the US Food and Drug Administration in 1999 and the European Committee in 1998; and opicapone (OPC), which was approved by the European Committee in 2016. A second-line COMT-I that requires regular hepatic monitoring, tolcapone (TOL), was approved by the Food and Drug Administration in 1998 and the European Committee in 1997. Of note, OPC also received Food and Drug Administration approval in 2021, but it is still only marketed in a few countries, including Germany, UK, Spain, Portugal, Italy, Japan, and USA, while ENT and TOL have a wider market. Our narrative review summarizes the pharmacokinetic/pharmacodynamic properties, clinical efficacy in terms of motor fluctuations, motor/non-motor symptoms, quality of life, and safety data of these three COMT-Is, as evidenced by randomized clinical trials, as well as by real-life observational studies. Overall, a phase III non-inferiority trial showed a similar effect between ENT and OPC on off-time (-60.8 min/day and -40.3 min/day, vs placebo, respectively), with a possible additional off-time reduction of 39 min/day, obtained when there is a switch from ENT to OPC. Concomitantly, TOL can reduce off-time by an average of 98 min/day. A significant though discrete concomitant reduction on the Unified Parkinson's Disease Rating Scale motor section (2-3 points) is obtained with all three drugs vs placebo. Data on quality of life are fewer and more heterogeneous, with positive results obtained especially in open-label studies. Effects on non-motor symptoms were investigated as secondary outcome only in a few studies, frequently by means of non-specific scales and a benefit was observed in open-label studies. Dopaminergic adverse effects were the most frequent, dyskinesia being the most common for the three drugs eventually requiring levodopa dose reductions. No urine discoloration and a very low incidence of diarrhea were found with OPC compared with ENT and TOL. Regular hepatic monitoring is needed only for TOL. A combination of COMT-Is with new formulations of levodopa, including the subcutaneous, intrajejunal, or new extended-release formulation, merits further exploration to improve the management of both mild and severe motor fluctuations.

[Relevance of COMT inhibitors in the treatment of motor fluctuations]

Catechol O‑methyltransferase (COMT) inhibitors have been established in the treatment of Parkinson's disease for more than 20 years. They are considered the medication of choice for treating motor fluctuations. The available COMT inhibitors, entacapone, opicapone and tolcapone, differ pharmacokinetically in terms of their half-lives with implications for the dose frequency, in their indication requirements and in their spectrum of side effects, including diarrhea and yellow discoloration of urine. Many patients with motor fluctuations are currently not treated with COMT inhibitors and are, therefore, unlikely to receive individually optimized drug treatment. This manuscript summarizes the results of a working group including several Parkinson's disease experts, in which the value of COMT inhibitors was critically discussed.

Dammarane triterpenes targeting α-synuclein: biological activity and evaluation of binding sites by molecular docking

Parkinson's disease (PD) is a neurodegenerative disorder that affects adult people whose treatment is palliative. Thus, we decided to test three dammarane triterpenes 1, 1a, 1b, and we determined that 1 and 1a inhibit β-aggregation through thioflavine T rather than 1b. Since compound 1 was most active, we determined the interaction between α-synuclein and 1 at 50 µM (Kd) through microscale thermophoresis. Also, we observed differences in height and diameter of aggregates, and α-synuclein remains unfolded in the presence of 1. Also, aggregates treated with 1 do not provoke neurites' retraction in N2a cells previously induced by retinoic acid. Finally, we studied the potential sites of interaction between 1 with α-synuclein fibrils using molecular modelling. Docking experiments suggest that 1 preferably interact with the site 2 of α-synuclein through hydrogen bonds with residues Y39 and T44.

Redefining the strategy for the use of COMT inhibitors in Parkinson's disease: the role of opicapone

INTRODUCTION

Levodopa remains the gold-standard Parkinson's disease (PD) treatment, but the inevitable development of motor complications has led to intense activity in pursuit of its optimal delivery.

AREAS COVERED

Peripheral inhibition of dopa-decarboxylase has long been considered an essential component of levodopa treatment at every stage of illness. In contrast, only relatively recently have catechol-O-methyltransferase (COMT) inhibitors been utilized to block the other major pathway of degradation and optimize levodopa delivery to the brain. First and second-generation COMT inhibitors were deficient because of toxicity, sub-optimal pharmacokinetics or a short duration of effect. As such, they have only been employed once 'wearing-off' has developed. However, the third-generation COMT inhibitor, opicapone has overcome these difficulties and exhibits long-lasting enzyme inhibition without the toxicity observed with previous generations of COMT inhibitors. In clinical trials and real-world PD studies opicapone improves the levodopa plasma profile and results in a significant improvement in ON time in 'fluctuating' disease, but it has not yet been included in the algorithm for early treatment.

EXPERT OPINION

This review argues for a shift in the positioning of COMT inhibition with opicapone in the PD algorithm and lays out a pathway for proving its effectiveness in early disease.

Opicapone and Levodopa-Carbidopa Intestinal Gel Infusion: The Way Forward Towards Cost Savings for Healthcare Systems?

Combined catechol-O-methyl-transferase-inhibition and Levodopa-Carbidopa intestinal gel (LCIG) infusion has the potential to reduce LCIG daily dose and the costs of this therapy. In this retrospective analysis, we report on Parkinson's disease (PD) patients on LCIG with concomitant Opicapone. In 11 patients, the introduction of Opicapone led to LCIG daily dose being reduced by 24.8% (p = 0.05) without any significant worsening of dyskinesia. Three patients withdrew from Opicapone due to side effects or inefficacy. LCIG daily dose reduction could lead to cost savings of £142,820.63/year in the United Kingdom while maintaining clinical care.

Opicapone for the treatment of Parkinson's disease: a review

Purpose: Levodopa formulations are the workhorses of the labor against motor symptoms management in Parkinson's disease (PD). Progression of PD on levodopa inevitably leads to motor fluctuations. It is important to understand the safety and efficacy of opicapone, the most recent addition to the clinician's armamentarium against these fluctuations.Materials and methods: We review the development of COMT inhibitors in the treatment of PD as well as the efficacy and safety data reported in the currently published literature of opicapone in PD. The "currently published literature" is defined as all published, PubMed indexed trials including the word "opicapone." Finally, we compare opicapone to the competitor pharmaceuticals on the market to treat symptom fluctuations in PD and share our opinion of opicapone's place in clinical practice.Results: From the reported results of phase 3 and 4 trials of opicapone in PD, it is a safe and efficacious option to combat motor fluctuations for our PD patients taking levodopa. A reduction of "off" time by up to 1 h per day can be expected, increasing "on" time with fewer dyskinesias. Opicapone is not generally hepatotoxic, and the most reported side-effects-dyskinesia, dry mouth, dizziness, diarrhea, and constipation-were seen in only 1.4% of the OPTIPARK (a large phase 4 clinical trial) study population.Conclusions: One should consider utilizing opicapone, perhaps in combination with other augmenting medications with different mechanisms of action, to help treat motor and non-motor fluctuations in PD.

Clinical Utility of Opicapone in the Management of Parkinson's Disease: A Short Review on Emerging Data and Place in Therapy

Parkinson’s disease (PD) is a prevalent neurodegenerative disorder, and levodopa (L-dopa) remains the most efficacious drug treatment for PD and a gold-standard for symptom control. Nonetheless, a significant majority of PD patients develop motor fluctuations over their disease course, with a significant impact on quality-of-life, meaning control of such complications translates into a fundamental clinical need. Catechol-O-methyl transferase (COMT) inhibitors (COMT-i) are used as first-line adjuvant therapy to L-dopa for end-of-dose (EoD) motor fluctuations, since they increase L-dopa availability in the brain by inhibiting its peripheral metabolism. Opicapone (OPC), a once-daily, long-acting COMT-i, is the most recent and potent of its class, having been licensed in Europe in 2016 as an add-on to preparations of L-dopa/DOPA decarboxylase inhibitors in PD patients with EoD motor fluctuations. More recently, it has also received approval in the USA and Japan in 2020. Two high-quality positive efficacy studies (double-blind Phase III clinical trials) established OPC efficacy with significant reduction in OFF time (average 60 minutes vs placebo), without concomitant increase of distressing dyskinesias during ON time. These beneficial effects were sustained in open-label extension studies, without unexpected safety issues or adverse events, with dyskinesia having been the most frequent complaint. OPC also avoids liver toxicity and gastrointestinal issues compared with previous COMT-i. In this review, we aimed to cover OPC’s lifecycle (synthesis to commercialization), its clinical pharmacological data, safety, tolerability and pharmacovigilance evidence, and discuss its role in the management of motor fluctuations in PD as well as its emerging place in international recommendations.

Opicapone for Parkinson's disease: clinical evidence and future perspectives

Since 2016, opicapone (OPC), a potent third-generation, long-acting, once-daily, peripheral catechol-O-methyltransferase inhibitor, is approved as an add-on to levodopa in Parkinson's disease patients with motor fluctuations. OPC 50 mg has showed to be able in reducing OFF time by an average of about 60 min daily compared with placebo, to further reduce OFF-time of about 39 min, when switched from ENT to OPC and to be safe. These beneficial effects of OPC were maintained for 1 year. Recently, several post hoc analysis and few pilot observational open-label studies, have suggested its efficacy and wider applicability for different phenotypes of motor complications and for Parkinson's disease stages. Here we review OPC applicability and perspectives, in the light of the more recently published analysis.

Opicapone: A Review in Parkinson's Disease

Oral opicapone (Ongentys^®), a potent third-generation, peripheral catechol-O-methyltransferase (COMT) inhibitor, is approved as adjunctive therapy to preparations of levodopa/dopa-decarboxylase inhibitor (L-dopa/DDCI) in adults with Parkinson's disease (PD) and end-of dose (EoD) motor fluctuations. In pivotal global trials (BIPARK 1 and BIPARK 2; 14-15 weeks' duration), open-label extensions (OLEs) of BIPARK, and in the real-world setting (OPTIPARK; 3-6 months), opicapone 50 mg once daily was an effective and generally well tolerated adjunctive therapy to L-dopa/DDCI plus other PD therapy in adults with PD and EoD motor fluctuations. Adjunctive opicapone provided better efficacy than placebo for improvements in ON- and OFF-state time and fulfilled noninferiority to adjunctive entacapone for improvements in OFF time in BIPARK 1. These beneficial effects of adjunctive opicapone on motor fluctuations were maintained during 1 year of treatment in OLE studies. Given its efficacy and safety profile, adjunctive opicapone remains an important option in the management of adults with PD and EoD motor fluctuations who cannot be stabilized on preparations of L-dopa/DDCI.

Therapeutic Strategies to Treat or Prevent Off Episodes in Adults with Parkinson's Disease

Parkinson's disease is a chronic, neurodegenerative disease, which manifests with a mixture of motor, cognitive and behavioural symptoms. Levodopa is the most effective antiparkinsonian treatment to date, although chronic use engenders a mixture of complications in a substantial proportion of patients. Amongst these is the occurrence of episodes of worsening symptoms-'off' phenomena. These episodes can manifest with either motor or non-motor symptoms or a combination of these features and have been found to have profound impacts on patients' quality of life. Although preventative measures are poorly evidenced, avoiding excessive total daily levodopa intake in selected populations that are deemed to be of a higher risk for developing these episodes warrants further exploration. Methods to improve levodopa bioavailability and delivery to the brain are currently available and are of value in addressing these episodes once they have become established. These include modifications to levodopa formulations as well as the use of complimentary agents that improve levodopa bioavailability. The deployment of device-assisted approaches is a further dimension that can be considered in addressing these debilitating episodes. This review summarises the clinical manifestations of 'off' phenomena and the current approaches to treat them. Although we briefly discuss clinical advances on the horizon, the predominant focus is on existing, established treatments.

EQUIDopa: A responsive web application for the levodopa equivalent dose calculator

BACKGROUND AND OBJECTIVE

Levodopa/carbidopa intestinal gel infusion is a treatment option for patients of advanced stage of Parkinson's disease. This treatment requires the time-consuming and error-prone conversion of orally taken antiparkinson drugs into an equivalent replacing dose of levodopa/carbidopa, which is delivered via pump. In order to facilitate and speed up this conversion process, we developed a specific user-friendly application that would be available online or as a standalone mobile application. Such an application has now been written and designed in collaboration with a computer scientist and physician, who is also intended to be the final user.

METHODS

The levodopa equivalent dose calculations are based on previous studies and data reported in the literature. Two related on-line conversion applications were analyzed and evaluated. The primary objectives of the application were determined, and basic functionalities were outlined. The application was implemented using modern development tools and frameworks.

RESULTS

The application has proven to be effective and easy to use in our clinical setting. It can serve as a control for manual calculations made by medical staff. It can also be applied as a useful tool in levodopa/carbidopa intestinal gel infusion courses for the advanced treatment of Parkinson's disease.

CONCLUSION

The presented application could replace the tedious and error-prone levodopa equivalent dose conversion of antiparkinson drugs efficiently. In comparison to related on-line conversion applications, this specific application provides more functionality, reduces the risk of user errors, and can be run on a variety of devices. The conversion value provided by the application is only an estimate. The effect of the drugs is specific for each individual patient, which could not be considered in the calculations. Therefore, the responsibility of using the results of the application rests with the clinical judgment of the user. Nevertheless, the application can give us a good starting point for the initial pump setting, which would be adjusted further during the titration period, according to the patient's response.

Opicapone Efficacy and Tolerability in Parkinson's Disease Patients Reporting Insufficient Benefit/Failure of Entacapone

BACKGROUND

Opicapone, a recently introduced catechol-o-methyl transferase (COMT) inhibitor has the advantage of being administered once daily, and has pharmacokinetic data to indicate it offers a greater degree of COMT inhibition than entacapone. Although trial data indicate it is non-inferior to entacapone, there are no data to indicate whether it offers any clinical advantages.

METHODS

In this audit, we present data from 57 individuals prescribed opicapone at the National Hospital for Neurology and Neurosurgery, Queen Square who had either not tolerated or reported insufficient benefit following previous prescription of entacapone.

RESULTS

A total of 20 of 57 patients switched directly from entacapone to opicapone ("entacapone switchers") whereas 37 of 57 patients had previously discontinued entacapone because of lack of benefit or adverse events ("entacapone failures"). A total of 21 of 57 (37%) patients stopped opicapone prior to 6 months. A total of 7 of 20 (35%) "entacapone switchers" experienced adverse events with opicapone of which 5 stopped the drug prior to the 6 month evaluation of efficacy. A total of 23 of 37 (62%) "entacapone failures" reported adverse events of which 16 stopped the drug. Among 36 of 57 (63%) patients who continued to use opicapone at 6 months, there was an improvement in OFF time of ~2 hours per day as measured by interview.

CONCLUSIONS

We conclude that opicapone can be an effective additional treatment for wearing off in Parkinson's disease (PD) in a subgroup of patients. The use of opicapone in our cohort with prior entacapone exposure, however, was associated with higher rates of adverse effects and treatment discontinuation than reported in published trial data of COMT inhibitor naïve patients.

Randomized, Controlled Study of Opicapone in Japanese Parkinson's Patients with Motor Fluctuations

Objectives

This placebo‐controlled, randomized study evaluated the efficacy and safety of opicapone 25‐mg and 50‐mg tablets in Japanese levodopa‐treated patients with Parkinson's disease and motor fluctuations.

Methods

Japanese adults (n = 437, age 39–83 years) with Parkinson's disease (United Kingdom Parkinson's Disease Society criteria) received opicapone 25‐mg (n = 145), opicapone 50‐mg (n = 145), or placebo (n = 147) tablets over the double‐blind treatment period (14–15 weeks). The primary efficacy assessment was change in OFF‐time; secondary efficacy assessments included OFF/ON‐time responders (≥1 hour change from baseline), total ON‐time, ON‐time with and without troublesome dyskinesia, and Unified Parkinson's Disease Rating Scale.

Results

The least squares mean (standard error) change in OFF‐time from baseline to the last visit was −0.42 (0.21) hour for the placebo group, −1.16 (0.22) hour for the opicapone 25 mg group, and −1.04 (0.21) hour for the opicapone 50 mg group. The percentage of ON‐time responders, changes in total ON‐time/ON‐time without troublesome dyskinesia, and Unified Parkinson's Disease Rating Scale II (at OFF) all showed statistically significant improvements versus placebo for both opicapone tablet doses (P < 0.05). Unified Parkinson's Disease Rating Scale III (at ON) was improved versus placebo in patients who received opicapone 50 mg (P < 0.05). Adverse events were more common in patients treated with opicapone 25 mg (60.0%) or opicapone 50 mg (54.5%) versus placebo (48.3%). The most commonly reported adverse event was dyskinesia (placebo, 2.7%; opicapone 25 mg, 9.0%; opicapone 50 mg, 12.4%).

Conclusions

In Japanese patients, both opicapone 25 and 50 mg were significantly more effective than placebo with no dose‐dependent difference in efficacy, and both doses were well tolerated. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Medical Management and Prevention of Motor Complications in Parkinson's Disease

Levodopa is the most effective medication for the treatment of the motor symptoms of Parkinson's disease. However, over time, the clinical response to levodopa becomes complicated by a reduction in the duration and reliability of motor improvement (motor fluctuations) and the emergence of involuntary movements (levodopa-induced dyskinesia). Strategies that have been attempted in an effort to delay the development of these motor complications include levodopa sparing and continuous dopaminergic therapy. Once motor complications occur, a wide array of medical treatments is available to maximize motor function through the day while limiting dyskinesia. Here, we review the clinical features, epidemiology, and risk factors for the development of motor complications, as well as strategies for their prevention and medical management.

Prospecting for new catechol-O-methyltransferase (COMT) inhibitors as a potential treatment for Parkinson's disease: a study by molecular dynamics and structure-based virtual screening

Parkinson's disease (PD) is a neurodegenerative, chronic, and progressive disease, common in the elderly. The catechol-O-methyltransferase (COMT) is a monomeric enzyme involved in dopamine (DA) degradation, the neurotransmitter in deficit in patients with PD. The reference treatment of PD consists of levodopa (L-dopa) administration, which is the precursor of DA. The inhibition of COMT is an adjuvant treatment in PD since it keeps DA levels constant. The goal of this study was to identify drug candidates capable of inhibiting COMT for the treatment of PD and identify important fragments of these molecules. Initially, we analyzed the flexibility of COMT and defined its main conformations in solution regarding the absence (system I) and presence of the S-adenosyl-L-methionine (SAM) cofactor (system II) through molecular dynamics (MD) simulations. Two regions in these structures were selected for molecular docking, firstly the entire cavity where the cofactor and substrates are bound and secondly the specific biding region of the enzyme substrates. Based on the conformations of the MD, the virtual screening (VS) was performed against FDA Approved and Zinc Natural Products databases aiming at the selection of the best compounds. Subsequently, the absorption, distribution, metabolization, excretion, and toxicity (ADMET) properties, as well as drug-score and drug-likeness indexes of the most promising compounds were analyzed. After a detailed analysis of the compounds selected by structure-based VS, it was possible to highlight the fragments most frequently involved in their stability: 2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole, 9H-Benz(c)indole(3,2,1-ij)(1,5)naphthyridin-9-one and (10R,13S)-10,13-dimethyl-1,2,6,7,8,9,11,12,14,15,16,17dodecahydrocyclopenta[a]phenanthren-3-one. The identification of these potential fragments is essential for the prospection of more specific inhibitors against COMT using the technique of Fragment-based lead discovery (FBLD). Besides, this study allowed us to identify the potential COMT inhibitors through a complete understanding of molecular-level interactions based on the flexibility of this protein.Communicated by Ramaswamy H. Sarma.

The preclinical discovery and development of opicapone for the treatment of Parkinson's disease

INTRODUCTION

Opicapone (OPC) is a well-established catechol-O-methyltransferase (COMT) inhibitor that is approved for the treatment of Parkinson's disease (PD) associated with L-DOPA/L-amino acid decarboxylase inhibitor (DDI) therapy allowing for prolonged activity due to a more continuous supply of L-DOPA in the brain. Thus, OPC decreases fluctuation in L-DOPA plasma levels and favors more constant central dopaminergic receptor stimulation, thus improving PD symptomatology.

AREAS COVERED

This review evaluates the preclinical development, pharmacology, pharmacokinetics and safety profile of OPC. Data was extracted from published preclinical and clinical studies published on PUBMED and SCOPUS (Search period: 2000-2019). Clinical and post-marketing data are also evaluated.

EXPERT OPINION

OPC is a third generation COMT inhibitor with a novel structure. It has an efficacy and tolerability superior to its predecessors, tolcapone (TOL) and entacapone (ENT). It also provides a safe and simplified drug regimen that allows neurologists to individually adjust the existing daily administration of L-DOPA. OPC is indicated as an adjunctive therapy to L-DOPA/DDI in patients with PD and end-of-dose motor fluctuations who cannot be stabilized on those combinations.

Effect of Opicapone Tablets on Levodopa and 3-O-Methyldopa Pharmacokinetics in Healthy Japanese Subjects: Phase 1 Study

This study evaluated the effect of a small-tablet formulation of opicapone for use in clinical trials in Japan on the pharmacokinetics of levodopa (l-dopa) and 3-O-methyldopa (3-OMD). In an open-label, 3-period, single-sequence crossover phase 1 study in 80 healthy Japanese males (aged 20-45 years; body mass index, 18.5 to <30.0 kg/m² ), 10 mg of l-dopa/carbidopa 100 was administered 3 times daily on day 0 (period 1) and day 12 (period 3), and opicapone tablets (5, 10, 25, or 50 mg; n = 20 each group) were administered once daily for 11 days (period 2). During periods 1 and 3, plasma concentrations of l-dopa and 3-OMD were measured and pharmacokinetic parameters (maximum observed plasma concentration, time at which maximum concentration was observed, area under the plasma concentration-time curve from time 0 to 5 hours [AUC_5h ] and from time 0 to 24 hours [AUC_24h ] following each dose, terminal half-life) of plasma l-dopa and 3-OMD were determined along with the geometric mean ratio (period 3/period 1) of AUC_24h for l-dopa and 3-OMD. Maximum concentration of l-dopa for the first, second, or third doses of l-dopa/carbidopa did not significantly increase with increasing opicapone dose. The AUC of l-dopa increased with increasing opicapone dose but tended toward a peak plateau with opicapone doses of 25 mg and higher. Geometric mean ratios (90% confidence intervals) of AUC_24h were 5 mg, 1.16 (1.10-1.21); 10 mg, 1.26 (1.23-1.30); 25 mg, 1.51 (1.44-1.57); 50 mg, 1.60 (1.54-1.66). Opicapone tablets were well tolerated. In Japanese healthy subjects, increases in plasma exposure to l-dopa appear to level off with opicapone doses of 25 mg and higher, which may be relevant for optimal dosing among Japanese patients with Parkinson disease.

Effectiveness and safety of opicapone in Parkinson's disease patients with motor fluctuations: the OPTIPARK open-label study

BACKGROUND

The efficacy and safety of opicapone, a once-daily catechol-O-methyltransferase inhibitor, have been established in two large randomized, placebo-controlled, multinational pivotal trials. Still, clinical evidence from routine practice is needed to complement the data from the pivotal trials.

METHODS

OPTIPARK (NCT02847442) was a prospective, open-label, single-arm trial conducted in Germany and the UK under clinical practice conditions. Patients with Parkinson's disease and motor fluctuations were treated with opicapone 50 mg for 3 (Germany) or 6 (UK) months in addition to their current levodopa and other antiparkinsonian treatments. The primary endpoint was the Clinician's Global Impression of Change (CGI-C) after 3 months. Secondary assessments included Patient Global Impressions of Change (PGI-C), the Unified Parkinson's Disease Rating Scale (UPDRS), Parkinson's Disease Questionnaire (PDQ-8), and the Non-Motor Symptoms Scale (NMSS). Safety assessments included evaluation of treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs).

RESULTS

Of the 506 patients enrolled, 495 (97.8%) took at least one dose of opicapone. Of these, 393 (79.4%) patients completed 3 months of treatment. Overall, 71.3 and 76.9% of patients experienced any improvement on CGI-C and PGI-C after 3 months, respectively (full analysis set). At 6 months, for UK subgroup only (n = 95), 85.3% of patients were judged by investigators as improved since commencing treatment. UPDRS scores at 3 months showed statistically significant improvements in activities of daily living during OFF (mean ± SD change from baseline: - 3.0 ± 4.6, p < 0.0001) and motor scores during ON (- 4.6 ± 8.1, p < 0.0001). The mean ± SD improvements of - 3.4 ± 12.8 points for PDQ-8 and -6.8 ± 19.7 points for NMSS were statistically significant versus baseline (both p < 0.0001). Most of TEAEs (94.8% of events) were of mild or moderate intensity. TEAEs considered to be at least possibly related to opicapone were reported for 45.1% of patients, with dyskinesia (11.5%) and dry mouth (6.5%) being the most frequently reported. Serious TEAEs considered at least possibly related to opicapone were reported for 1.4% of patients.

CONCLUSIONS

Opicapone 50 mg was effective and generally well-tolerated in PD patients with motor fluctuations treated in clinical practice.

TRIAL REGISTRATION

Registered in July 2016 at clinicaltrials.gov (NCT02847442).

From medications to surgery: advances in the treatment of motor complications in Parkinson's disease

Motor complications are responsible for the large burden of disability and poor quality of life in Parkinson’s disease (PD). The pulsatile nature of stimulation with oral dopaminergic therapies due to relatively short pharmacokinetic profiles and dysfunctional gastrointestinal absorption have been attributed to the development of PD motor complications. In this review, we will provide an overview of the pharmacologic and surgical therapies currently available and under investigation for the treatment of motor fluctuations and dyskinesia.

Opicapone for the treatment of Parkinson's disease: A review of a new licensed medicine

Catechol-O-methyl transferase inhibitors are currently used as first-line add-on therapy to levodopa for the treatment of end-of-dose motor fluctuations in Parkinson's disease patients, as they increase levodopa bioavailability. Several factors hamper the use of current available catechol-O-methyl transferase inhibitors, that is, the moderate efficacy and multiple dosing for entacapone and the risk of liver toxicity with tolcapone. Opicapone, a new long-acting, peripherally selective, once-daily catechol-O-methyl transferase inhibitor, was recently licensed in Europe. Two phase 3 double-blind clinical trials demonstrated opicapone efficacy in reducing OFF time by an average of about 60 minutes daily compared with placebo, without increasing ON time with troublesome dyskinesias. These effects were also maintained during a subsequent open-label extension consisting of 1-year follow-up. Opicapone showed a good safety profile. From June 2016, Opicapone received the approval for marketing authorization from the European Commission as adjunctive therapy to levodopa/DOPA decarboxylase inhibitors in patients with PD and end-of-dose motor fluctuations. We aimed to review the clinical pharmacological data of opicapone, summarize its clinical efficacy and safety issues, and discuss its potential role in the management of Parkinson's disease. © 2018 International Parkinson and Movement Disorder Society.

Opicapone for the management of end-of-dose motor fluctuations in patients with Parkinson's disease treated with L-DOPA

INTRODUCTION

Opicapone is a third generation, highly potent and effective catechol O‑methyltransferase (COMT) inhibitor that optimizes the pharmacokinetics and bioavailability of L-DOPA therapy. Areas covered: In this review, the authors describe the preclinical and clinical development of opicapone. In PD patients with motor fluctuations, once daily opicapone administration was well-tolerated and consistently reduced OFF-time and increased ON-time without increasing the frequency of troublesome dyskinesia, and these benefits were maintained over at least a year of continued open-label therapy. Expert commentary: With its convenient once-daily regimen, adjunct opicapone should be considered as an effective option for use in L-DOPA treated PD patients experiencing motor fluctuations.

Opicapone: A Review in Parkinson's Disease

Oral opicapone (Ongentys(®)), a potent, third-generation, long-acting, peripheral catechol-O-methyltransferase (COMT) inhibitor, is approved as adjunctive treatment to levodopa (L-Dopa)/dopa-decarboxylase inhibitor (DDCI) therapy in adults with Parkinson's disease (PD) and end-of-dose motor fluctuations who cannot be stabilized on those combinations. In 14- to 15-week, double-blind, multinational trials and in 1-year, open-label extension studies in this patient population, opicapone was an effective and generally well tolerated adjunctive therapy to L-Dopa plus a DDCI and other PD therapy. During the double-blind phase, adjunctive opicapone 50 mg once daily provided significantly greater improvements in motor fluctuations than placebo, with these improvements noninferior to those with entacapone. These beneficial improvements in motor fluctuations with opicapone were maintained in patients who continued adjunctive opicapone during the extension studies, with patients who switched from placebo or entacapone to opicapone experiencing significant improvements in motor fluctuations during this year. No new unexpected safety concerns were identified after ≈1.4 years' treatment with opicapone, with no serious cases of hepatotoxicity reported in clinical trials. With its convenient once-daily regimen, oral opicapone is an emerging COMT inhibitor option for use as adjunctive therapy to L-Dopa/DDCI therapy in adults with PD and end-of dose motor fluctuations who cannot be stabilized on those combinations.

Old and new challenges in Parkinson's disease therapeutics

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the degeneration of dopaminergic neurons and/or loss od neuronal projections, in several dopaminergic networks. Current treatments for idiopathic PD rely mainly on the use of pharmacologic agents to improve motor symptomatology of PD patients. Nevertheless, so far PD remains an incurable disease. Therefore, it is of utmost importance to establish new therapeutic strategies for PD treatment. Over the last 20 years, several molecular, gene and cell/stem-cell therapeutic approaches have been developed with the aim of counteracting or retarding PD progression. The scope of this review is to provide an overview of PD related therapies and major breakthroughs achieved within this field. In order to do so, this review will start by focusing on PD characterization and current treatment options covering thereafter molecular, gene and cell/stem cell-based therapies that are currently being studied in animal models of PD or have recently been tested in clinical trials. Among stem cell-based therapies, those using MSCs as possible disease modifying agents for PD therapy and, specifically, the MSCs secretome contribution to meet the clinical challenge of counteracting or retarding PD progression, will be more deeply explored.

Effect of opicapone multiple-dose regimens on levodopa pharmacokinetics

AIMS

To compare the levodopa/carbidopa (LC) and levodopa/benserazide (LB) pharmacokinetic profiles following repeated doses of opicapone (OPC) administered apart from levodopa.

METHODS

Two randomized, double blind, sex-balanced, placebo-controlled studies in four groups of 12 or 18 healthy subjects each. In each group, enrolled subjects received a once-daily morning (5, 15 and 30 mg) or evening (5, 15 and 50 mg) administration of OPC or placebo for up to 28 days. On the morning of Day 11, 12 h after the OPC or placebo evening dose, or the morning of Day 21, 1 h after the OPC or placebo dose, a single dose of immediate-release 100/25 mg LC was administered. Similarly, on Day 18 morning, 12 h after the OPC or placebo evening dose, or Day 28 morning, 1 h after the OPC or placebo dose, a single dose of immediate-release 100/25 mg LB was administered.

RESULTS

All OPC treatments, in relation to the placebo group, presented a higher extent of exposure (AUC) to levodopa following either LC or LB doses. A relevant but not dose-dependent increase in the levodopa AUC occurred with all OPC dose groups in relation to placebo. All active treatments significantly inhibited both peak (Emax ) and extent (AUEC) of the catechol-O-methyltransferase activity in relation to placebo. The tolerability profile was favourable.

CONCLUSION

Opicapone, as once-daily oral evening regimen and/or 1 h apart from levodopa therapy, increases the bioavailability of levodopa associated with its pronounced, long-lasting and sustained catechol-O-methyltransferase inhibition. The tolerability profile was favourable and similar between OPC and placebo.

Spotlight on opicapone as an adjunct to levodopa in Parkinson's disease: design, development and potential place in therapy

Parkinson's disease (PD) is a progressive, chronic, neurodegenerative disease characterized by rigidity, tremor, bradykinesia and postural instability secondary to dopaminergic deficit in the nigrostriatal system. Currently, disease-modifying therapies are not available, and levodopa (LD) treatment remains the gold standard for controlling motor and nonmotor symptoms of the disease. LD is extensively and rapidly metabolized by peripheral enzymes, namely, aromatic amino acid decarboxylase and catechol-O-methyltransferase (COMT). To increase the bioavailability of LD, COMT inhibitors are frequently used in clinical settings. Opicapone is a novel COMT inhibitor that has been recently approved by the European Medicines Agency as an adjunctive therapy to combinations of LD and aromatic amino acid decarboxylase inhibitor in adult PD patients with end-of-dose motor fluctuations. We aimed to review the biochemical properties of opicapone, summarize its preclinical and clinical trials and discuss its future potential role in the treatment of PD.

Clinical pharmacology review of opicapone for the treatment of Parkinson's disease

Two catechol-O-methyl transferase inhibitors are currently used as add-on therapy to levodopa for the amelioration of end-of-dose motor fluctuations in Parkinson's disease patients: entacapone, which has moderate efficacy and requires multiple dosing, and tolcapone, which has a poor safety profile. Opicapone (OPC) is a novel, long-acting, peripherally selective, once daily, third-generation catechol-O-methyl transferase inhibitor. Two Phase III clinical trials demonstrated OPC efficacy in reducing OFF-time by an average of about 60 min daily compared with placebo, without increasing ON-time with troublesome dyskinesias, with a good drug safety profile. In June 2016, the European Commission granted a marketing authorization valid throughout the European Union for OPC, indicated as adjunctive of levodopa decarboxylase inhibitors in adult patients with Parkinson's disease and end-of-dose motor fluctuations.

Advances in understanding genomic markers and pharmacogenetics of Parkinson's disease

INTRODUCTION

The inheritance pattern of Parkinson's disease (PD) is likely multifactorial (owing to the interplay of genetic predisposition and environmental factors). Many pharmacogenetic studies have tried to establish a possible role of candidate genes in PD risk. Several studies have focused on the influence of genes in the response to antiparkinsonian drugs and in the risk of developing side-effects of these drugs.

AREAS COVERED

This review presents an overview of current knowledge, with particular emphasis on the most recent advances, both in case-control association studies on the role of candidate genes in the risk for PD as well as pharmacogenetic studies on the role of genes in the development of side effects of antiparkinsonian drugs. The most reliable results should be derived from meta-analyses of case-control association studies on candidate genes involving large series of PD patients and controls, and from genome-wide association studies (GWAS).

EXPERT OPINION

Prospective studies of large samples involving several genes with a detailed history of exposure to environmental factors in the same cohort of subjects, should be useful to clarify the role of genes in the risk for PD. The results of studies on the role of genes in the development of side-effects of antiparkinsonian drugs should, at this stage, only be considered preliminary.

Effect of 3 Single-Dose Regimens of Opicapone on Levodopa Pharmacokinetics, Catechol-O-Methyltransferase Activity and Motor Response in Patients With Parkinson Disease

This study determined the effects of single doses of opicapone (OPC), a novel third-generation catechol-O-methyltransferase (COMT) inhibitor, on levodopa and 3-O-methyl-levodopa (3-OMD) pharmacokinetics (PK), COMT activity and motor fluctuations in patients with Parkinson disease (PD). Subjects received, in a double-blind manner, 25, 50, and 100 mg OPC or placebo (PLC) in 4 separate treatment periods. The washout period between doses was at least 10 days. During each period, the OPC/PLC capsules were to be coadministered with the morning dose of 100/25 mg levodopa/carbidopa (LC) or levodopa/benserazide (LB) on day 3. In relation to PLC, levodopa exposure increased 3.7%, 16.4%, and 34.8% following 25, 50, or 100 mg OPC, respectively. Maximum S-COMT inhibition (Emax ) ranged from 67.8% (25 mg OPC) to 100% (100 mg OPC). Peak and extent of S-COMT inhibition were dose-dependent. Maximum decrease in the plasma 3-OMD was observed following administration of 100 mg OPC. Opicapone administered concomitantly with standard-release 100/25 mg LC or LB improved motor performance. Treatments were generally well tolerated and safe. It was concluded that OPC is a new COMT inhibitor that significantly decreased COMT activity and increased systemic exposure to levodopa in PD patients with motor fluctuations.

Evaluation of opicapone on cardiac repolarization in a thorough QT/QTc study

Opicapone, a novel third-generation catechol-O-methyltransferase inhibitor for use as adjunctive therapy in levodopa-treated Parkinson's disease patients, was investigated on cardiac repolarization in healthy adult volunteers. This was a single-center, randomized, double-blind, placebo-controlled, open-label active-controlled, 4-period crossover study conducted in 64 subjects. In each period, subjects received a single oral dose of 50 mg opicapone, 800 mg opicapone, placebo, or 400 mg moxifloxacin and 24-hour 12-lead Holter monitoring was performed on day -1 (baseline) and after each single dose. After a single oral administrations of 50 and 800 mg opicapone, opicapone was the major entity in the circulation, with a median tmax of 1.5-2.0 hours. Opicapone was rapidly eliminated, with an elimination half-life of 1-2 hours. There was no clinically relevant effect of 50 and 800 mg opicapone versus placebo on cardiac depolarization or repolarization. All upper bounds of the 1-sided 95% confidence interval (CI) were below 10 milliseconds, confirming that opicapone has no QT-prolonging effect. Moxifloxacin caused an increase in the QTcI, with a lower bound of the 2-sided 95% CI always higher than 5 milliseconds, around the tmax of peak concentration, demonstrating assay sensitivity. In conclusion, administration of opicapone at therapeutic (50 mg) and supratherapeutic (800 mg) doses did not induce a clinically significant prolongation of the QTc interval.

Pharmacological profile of opicapone, a third-generation nitrocatechol catechol-O-methyl transferase inhibitor, in the rat

BACKGROUND AND PURPOSE

Catechol-O-methyltransferase (COMT) is an important target in the levodopa treatment of Parkinson's disease; however, the inhibitors available have problems, and not all patients benefit from their efficacy. Opicapone was developed to overcome those limitations. In this study, opicapone's pharmacological properties were evaluated as well as its potential cytotoxic effects.

EXPERIMENTAL APPROACH

The pharmacodynamic effects of opicapone were explored by evaluating rat COMT activity and levodopa pharmacokinetics, in the periphery through microdialysis and in whole brain. The potential cytotoxicity risk of opicapone was explored in human hepatocytes by assessing cellular ATP content and mitochondrial membrane potential.

KEY RESULTS

Opicapone inhibited rat peripheral COMT with ED50 values below 1.4 mg⋅kg(-1) up to 6 h post-administration. The effect was sustained over the first 8 h and by 24 h COMT had not returned to control values. A single administration of opicapone resulted in increased and sustained plasma levodopa levels with a concomitant reduction in 3-O-methyldopa from 2 h up to 24 h post-administration, while tolcapone produced significant effects only at 2 h post-administration. The effects of opicapone on brain catecholamines after levodopa administration were sustained up to 24 h post-administration. Opicapone was also the least potent compound in decreasing both the mitochondrial membrane potential and the ATP content in human primary hepatocytes after a 24 h incubation period.

CONCLUSIONS AND IMPLICATIONS

Opicapone has a prolonged inhibitory effect on peripheral COMT, which extends the bioavailability of levodopa, without inducing toxicity. Thus, it exhibits some improved properties compared to the currently available COMT inhibitors.

Improving L-dopa therapy: the development of enzyme inhibitors

The introduction of levodopa produced a monumental change in the treatment of Parkinson's disease (PD). Limitations in its bioavailability and tolerability led to the search for drugs that could improve its pharmacokinetics and safety profile. Dopa-decarboxylase inhibitors were the first such drugs that were developed, and their use in combination with L-dopa has become standard practice. Increasing knowledge on the metabolism of L-dopa allowed the identification of additional targets for intervention in an attempt to improve the symptomatic efficacy of L-dopa. Monoamineoxidase inhibitors, enhancing the central bioavailability of dopamine by blocking its metabolism, were the next step, and despite controversies regarding their efficacy, they have remained as valuable adjuncts to l-dopa in the treatment of PD. More recently, the introduction of potent, selective catechol-O-methyl transferase inhibitors have found their place in the therapeutic armamentarium of PD and are prescribed in combination with l-dopa to prolong the duration of its action.

Medicinal chemistry of catechol O-methyltransferase (COMT) inhibitors and their therapeutic utility

Catechol O-methyltransferase (COMT) is the enzyme responsible for the O-methylation of endogenous neurotransmitters and of xenobiotic substances and hormones incorporating catecholic structures. COMT is a druggable biological target for the treatment of various central and peripheral nervous system disorders, including Parkinson's disease, depression, schizophrenia, and other dopamine deficiency-related diseases. The purpose of this perspective is fourfold: (i) to summarize the physiological role of COMT inhibitors in central and peripheral nervous system disorders; (ii) to provide the history and perspective of the medicinal chemistry behind the discovery and development of COMT inhibitors; (iii) to discuss how the physicochemical properties of recognized COMT inhibitors are understood to exert influence over their pharmacological properties; and (iv) to evaluate the clinical benefits of the most relevant COMT inhibitors.