O-methyltransferase Inhibitors Research Articles

Addressing the Ethnicity Gap in Catechol O-Methyl Transferase Inhibitor Trials in Parkinson's Disease: A Review of Available Global Data.

Catechol-O-methyltransferase inhibitors (COMT-Is) have significantly improved the quality of life and symptom management for those at advanced stages of Parkinson's Disease (PD). Given that PD is one of the fastest-growing neurodegenerative diseases worldwide, there is a need to establish a clear framework for the systematic distribution of COMT-Is, considering inter-individual and intra-individual variations in patient response. One major barrier to this is the underrepresentation of ethnic minority participants in clinical trials investigating COMT-Is. To investigate this, we performed a narrative review. We searched PubMed for clinical trials investigating COMT-Is in patients with PD and examined the ethnic diversity of cohorts. A total of 63 articles were identified, with 34 trials found to match our inclusion criteria. Among the 34 trials meeting our inclusion criteria, only 8 reported participants' ethnic backgrounds. Our findings reveal a consistent underrepresentation of ethnic minority groups in trials investigating COMT-Is in PD cohorts-a trend that reflects broader concerns across clinical research. In this review, we explore potential reasons for the underrepresentation of ethnic minorities in clinical trials and propose strategies to address this issue.

IPX203 vs Immediate-Release Carbidopa-Levodopa for the Treatment of Motor Fluctuations in Parkinson Disease

Levodopa has a short half-life and a limited window of opportunity for absorption in the proximal small intestine. IPX203 is an oral, extended-release formulation of carbidopa-levodopa developed to address these limitations. To assess the efficacy and safety of IPX203 vs immediate-release carbidopa-levodopa in patients with Parkinson disease who are experiencing motor fluctuations. RISE-PD was a 20-week, randomized, double-blind, double-dummy, active-controlled, phase 3 clinical trial. The study was conducted between November 6, 2018, and June 15, 2021, at 105 academic and clinical centers in the US and Europe. Patients with Parkinson disease taking a total daily dose of 400 mg or more of levodopa and experiencing an average of 2.5 hours or more daily off-time were included in the study. A total of 770 patients were screened, 140 were excluded (those taking controlled-release carbidopa-levodopa apart from a single daily bedtime dose, Rytary (Amneal Pharmaceuticals), additional carbidopa or benserazide, or catechol O-methyl transferase inhibitors or who had a history of psychosis within the past 10 years), and 630 were enrolled in the trial. Following open-label immediate-release carbidopa-levodopa dose adjustment (3 weeks) and conversion to IPX203 (4 weeks), patients were randomized in a 1:1 ratio to double-blind, double-dummy treatment with immediate-release carbidopa-levodopa or IPX203 for 13 weeks. The primary end point was mean change in daily good on-time (ie, on-time without troublesome dyskinesia) from baseline to the end of the double-blind treatment period. A total of 630 patients (mean [SD] age, 66.5 [8.95] years; 396 [62.9%] men) were enrolled, and 506 patients were randomly assigned to receive IPX203 (n = 256) or immediate-release carbidopa-levodopa (n = 250). The study met its primary end point, demonstrating statistically significant improvement in daily good on-time for IPX203 compared to immediate-release carbidopa-levodopa (least squares mean, 0.53 hours; 95% CI, 0.09-0.97; P = .02), with IPX203 dosed a mean 3 times per day vs 5 times per day for immediate-release carbidopa-levodopa. Good on-time per dose increased by 1.55 hours with IPX203 compared to immediate-release carbidopa-levodopa (95% CI, 1.37-1.73; P < .001). IPX203 was well tolerated. The most common adverse events in the double-blind phase (IPX203 vs immediate-release carbidopa-levodopa) were nausea (4.3% vs 0.8%) and anxiety (2.7% vs 0.0%). In this study, IPX203 provided more hours of good on-time per day than immediate-release carbidopa-levodopa, even as IPX203 was dosed less frequently. ClinicalTrials.gov Identifier: NCT03670953.

Off-time Treatment Options for Parkinson's Disease.

Motor fluctuations (MF) are deemed by patients with Parkinson's disease (PD) as the most troublesome disease feature resulting from the increasing impairment in responsiveness to dopaminergic drug treatments. MF are characterized by the loss of a stable response to levodopa over the nychthemeron with the reappearance of motor (and non-motor) parkinsonian clinical signs at various moments during the day and night. They normally appear after a few years of levodopa treatment and with a variable, though overall increasing severity, over the disease course. The armamentarium of first-line treatment options has widened in the last decade with new once-a-daily compounds, including a catechol O-methyltransferase inhibitor - Opicapone-, two MAO-B inhibitors plus channel blocker - Zonisamide and Safinamide and one amantadine extended-release formulation - ADS5012. In addition to apomorphine injection or oral levodopa dispersible tablets, which have been available for a long time, new on-demand therapies such as apomorphine sublingual or levodopa inhaled formulations have recently shown efficacy as rescue therapies for Off-time treatment. When the management of MF becomes difficult in spite of oral/on-demand options, more complex therapies should be considered, including surgical, i.e. deep brain stimulation, or device-aided therapies with pump systems delivering continuous subcutaneous or intestinal levodopa or subcutaneous apomorphine formulation. Older and less commonly used ablative techniques (radiofrequency pallidotomy) may also be effective while there is still scarce data regarding Off-time reduction using a new lesional approach, i.e. magnetic resonance-guided focused ultrasound. The choice between the different advanced therapies options is a shared decision that should consider physician opinion on contraindication/main target symptom, patients' preference, caregiver's availability together with public health systems and socio-economic environment. The choice of the right/first add-on treatment is still a matter of debate as well as the proper time for an advanced therapy to be considered. In this narrative review, we discuss all the above cited aspects of MF in patients with PD, including their phenomenology, management, by means of pharmacological and advanced therapies, on-going clinical trials and future research and treatment perspectives.

Ligand and Structure-Based In Silico Determination of the Most Promising SARS-CoV-2 nsp16-nsp10 2'-o-Methyltransferase Complex Inhibitors among 3009 FDA Approved Drugs.

As a continuation of our earlier work against SARS-CoV-2, seven FDA-approved drugs were designated as the best SARS-CoV-2 nsp16-nsp10 2′-o-methyltransferase (2′OMTase) inhibitors through 3009 compounds. The in silico inhibitory potential of the examined compounds against SARS-CoV-2 nsp16-nsp10 2′-o-methyltransferase (PDB ID: (6W4H) was conducted through a multi-step screening approach. At the beginning, molecular fingerprints experiment with SAM (S-Adenosylmethionine), the co-crystallized ligand of the targeted enzyme, unveiled the resemblance of 147 drugs. Then, a structural similarity experiment recommended 26 compounds. Therefore, the 26 compounds were docked against 2′OMTase to reveal the potential inhibitory effect of seven promising compounds (Protirelin, (1187), Calcium folinate (1913), Raltegravir (1995), Regadenoson (2176), Ertapenem (2396), Methylergometrine (2532), and Thiamine pyrophosphate hydrochloride (2612)). Out of the docked ligands, Ertapenem (2396) showed an ideal binding mode like that of the co-crystallized ligand (SAM). It occupied all sub-pockets of the active site and bound the crucial amino acids. Accordingly, some MD simulation experiments (RMSD, RMSF, Rg, SASA, and H-bonding) have been conducted for the 2′OMTase—Ertapenem complex over 100 ns. The performed MD experiments verified the correct binding mode of Ertapenem against 2′OMTase exhibiting low energy and optimal dynamics. Finally, MM-PBSA studies indicated that Ertapenem bonded advantageously to the targeted protein with a free energy value of −43 KJ/mol. Furthermore, the binding free energy analysis revealed the essential amino acids of 2′OMTase that served positively to the binding. The achieved results bring hope to find a treatment for COVID-19 via in vitro and in vivo studies for the pointed compounds.

Anti-Parkinson Drug from Chemical Medicines and Herbal Medicines: A Review

Parkinson's disease (PD) is a disease of the central nervous system. It is a progressive disorder, meaning it gets worse over time. PD usually characterized by tremor, rigidity, akinesia and postural autonomic instability. In addition, it may also cause a series of non-motor symptoms (NMSs). This disease affects a small area of cells in the middle of the brain. This area is called the substantia nigra (SNc). The cells slowly lose their ability to produce a chemical called dopamine. The disease usually appears in the age over 60 years. Nowadays, a lot of anti-Parkinson drugs have been found either from that of chemicals or herbs. In this essay anti-Parkinson drugs from chemical medicine and herbal medicines especially from china will be discussed. Anti-Parkinson's drugs are derived from chemical medicines include levodopa (l-dopa), dopamine agonists, MAO-B inhibitors, catechol O-methyltransferase (COMT) inhibitors, anticholinergics and amantadine. Meanwhile, anti-Parkinson drugs derived from herbal medicine include Scutellaria baicalensis Georgi, Polygonum cuspidatum Sieb. et Zucc., green tea (Camellia sinensis L.), Panax ginseng C. A. Mey., Cistanche deserticola Y. C. Ma, Panax Notoginseng Wall. var notoginseng (Burkill.) F.H. Chen, Gastrodia elata Blume and Polygala tenuifoliaWilld.. These drugs have the same effects to help ease symptoms of Parkinson’s and can increase the amount of dopamine in substantia nigra pars compacta (SNc). However, some chemical drugs have more side effects although herbal medicines are less clear, more tests need to be planned.

In silico identification of potential SARS COV-2 2′-O-methyltransferase inhibitor: fragment-based screening approach and MM-PBSA calculations

In the present era, there are many efforts trying to face the emerging and successive waves of the COVID-19 pandemic. This has led to considering new and unusual targets for SARS CoV-2. 2′-O-Methyltransferase (nsp16) is a key and attractive target in the SARS CoV-2 life cycle since it is responsible for the viral RNA protection via a cap formation process. In this study, we propose a new potential inhibitor for SARS COV-2 2′-O-methyltransferase (nsp16). A fragment library was screened against the co-crystal structure of the SARS COV-2 2′-O-methyltransferase complexed with Sinefungin (nsp16 – PDB ID: 6WKQ), and consequently the best proposed fragments were linked via a de novo approach to build molecule AP-20. Molecule AP-20 displayed a superior docking score to Sinefungin and reproduced the key interactions in the binding site of 2′-O-methyltransferase. Three molecular dynamic simulations of the 2′-O-methyltransferase apo structure and its complexed forms with AP-20 and Sinefungin were performed for 150 nano-seconds to provide insights on the dynamic nature of such setups and to assess the stability of the proposed AP-20/enzyme complex. AP-20/enzyme complex demonstrated better stability for the ligand–enzyme complex compared to Sinefungin in a respective setup. Furthermore, MM-PBSA binding free energy calculations showed a better profile for AP-20/enzyme complex compared to Sinefungin/enzyme complex emphasizing the potential inhibitory effect of AP-20 on SARS COV-2 2′-O-methyltransferase. We endorse our designed molecule AP-20 to be further explored via experimental evaluations to confront the spread of the emerging COVID-19. Also, in silico ADME profiling has ascribed to AP-20 an excellent safety and metabolic stability profile.

In silico identification of novel SARS-COV-2 2′-O-methyltransferase (nsp16) inhibitors: structure-based virtual screening, molecular dynamics simulation and MM-PBSA approaches

The novel coronavirus disease COVID-19, caused by the virus SARS CoV-2, has exerted a significant unprecedented economic and medical crisis, in addition to its impact on the daily life and health care systems all over the world. Regrettably, no vaccines or drugs are currently available for this new critical emerging human disease. Joining the global fight against COVID-19, in this study we aim at identifying a potential novel inhibitor for SARS COV-2 2′-O-methyltransferase (nsp16) which is one of the most attractive targets in the virus life cycle, responsible for the viral RNA protection via a cap formation process. Firstly, nsp16 enzyme bound to Sinefungin was retrieved from the protein data bank (PDB ID: 6WKQ), then, a 3D pharmacophore model was constructed to be applied to screen 48 Million drug-like compounds of the Zinc database. This resulted in only 24 compounds which were subsequently docked into the enzyme. The best four score-ordered hits from the docking outcome exhibited better scores compared to Sinefungin. Finally, three molecular dynamics (MD) simulation experiments for 150 ns were carried out as a refinement step for our proposed approach. The MD and MM-PBSA outputs revealed compound 11 as the best potential nsp16 inhibitor herein identified, as it displayed a better stability and average binding free energy for the ligand-enzyme complex compared to Sinefungin.

Opicapone (Ongentys): A New COMT Inhibitor for the Treatment of Parkinson's Disease.

To describe the safety and efficacy of opicapone, a newly Food and Drug Administration-approved catechol-O-methyltransferase (COMT) inhibitor, as an adjunctive treatment to levodopa/carbidopa in patients with Parkinson's disease (PD) experiencing off episodes. A literature search through PubMed and International Pharmaceutical Abstracts (January 2000 to October 2020) was conducted using the following search terms: Ongentys, opicapone, COMT inhibitor, Parkinson's disease, and Parkinson's. Articles selected included those describing preclinical and clinical studies examining the pharmacokinetics, efficacy, and/or safety of opicapone. In preclinical trials, opicapone demonstrated marked S-COMT inhibition, despite its short half-life, while maintaining an acceptable safety and efficacy profile. Results from phase 3 clinical trials further supported the safety and efficacy of opicapone as an adjunct to levodopa. In addition, opicapone, at a dose of 50 mg once daily, was shown to be superior to placebo and noninferior to entacapone in reducing time spent in the off state. Adverse effects commonly reported with opicapone include dyskinesias, constipation, hypotension/syncope, increased blood creatine kinase, and decreased weight. Additional medications, such as COMT inhibitors, become necessary adjunctive treatments as the disease progresses. Compared to other COMT inhibitors currently on the US market, opicapone offers the advantage of once-daily dosing. Opicapone is a safe and effective COMT inhibitor shown to reduce off episodes in patients with PD.

Safety Profile of Opicapone in the Management of Parkinson's Disease.

Opicapone is a catechol O-methyltransferase (COMT) inhibitor indicated for use as adjunct to levodopa therapy in patients with Parkinson's disease (PD) and motor fluctuations. To characterize the safety and tolerability of adjunct opicapone (25 and 50 mg) in a pooled population of levodopa-treated PD patients who participated in the opicapone Phase-3 clinical program. Patient-level data (placebo, opicapone 25 mg and 50 mg) from the BIPARK-1 and BIPARK-2 double-blind and open-label studies were combined. Pooled analyses included 766 patients from the double-blind studies and 848 patients from the open-label studies. In the double-blind studies, 63.3% of opicapone-treated patients reported treatment-emergent adverse events (TEAEs) versus 57.2% in the placebo group. The most common TEAEs reported in the opicapone group compared to placebo were dyskinesia, constipation and insomnia. The incidence of serious TEAEs was similar across opicapone and placebo groups (3.5% versus 4.3%, respectively). Overall, 71.3% patients treated with open-label opicapone reported at least one TEAE; most occurred within the first 2 months of the open-label studies, and then decreased thereafter. Throughout the Phase-3 clinical program, there were no serious AEs suggestive of hepatic toxicity, and the incidence of gastrointestinal disorders such as nausea and diarrhea remained low (<2%). There were no relevant changes in laboratory parameters including liver enzymes, vital signs, physical or neurological examinations, or ECG readings. Long-term use of opicapone once-daily over 1-year at doses of 25 mg or 50 mg was generally safe and well tolerated, supporting its clinical usefulness in the management of PD motor fluctuations.

Effects of Catechol O-Methyl Transferase Inhibition on Anti-Inflammatory Activity of Luteolin Metabolites.

Although luteolin is known to have potent anti-inflammatory activities, much less information has been provided on such activities of its hepatic metabolites. Luteolin was subjected to hepatic metabolism in HepG2 cells either without or with catechol O-methyl transferase (COMT) inhibitor. To identify hepatic metabolites of luteolin without (luteolin metabolites, LMs) or with COMT inhibitor (LMs+CI), metabolites were treated by β-glucuronidase and sulfatase, and found that they were composed of glucuronide and sulfate conjugates of diosmetin in LMs or these conjugates of luteolin in LMs+CI. LMs and LMs+CI were examined for their anti-inflammatory activities on LPS stimulated Raw 264.7 cells. Expression of iNOS and production of nitric oxide and pro-inflammatory cytokines such as TNF-α, IL-1β, and IL-6 were suppressed more effectively by the treatment with LMs+CI than LMs. Our data provide a new insight on possible improvement in functional properties of luteolin on target cells by modifying their metabolic pathway in hepatocytes.

Opicapone as Adjunct to Levodopa Therapy in Patients With Parkinson Disease and Motor Fluctuations

Catechol O-methyltransferase (COMT) inhibitors are an established treatment for end-of-dose motor fluctuations associated with levodopa therapy in patients with Parkinson disease (PD). Current COMT inhibitors carry a high risk for toxic effects to hepatic cells or show moderate improvement. Opicapone was designed to be effective without the adverse effects. To evaluate the efficacy and safety of 25- and 50-mg/d dosages of opicapone compared with placebo as adjunct to levodopa therapy in patients with PD experiencing end-of-dose motor fluctuations. This phase 3 international, multicenter outpatient study evaluated a 25- and a 50-mg/d dosage of opicapone in a randomized, double-blind, 14- to 15-week, placebo-controlled clinical trial, followed by a 1-year open-label phase during which all patients received active treatment with opicapone. Patients with PD who experienced signs of end-of-dose deterioration and had a mean total awake off-time (state of akinesia or decreased mobility) of at least 1.5 hours, not including morning akinesia, were enrolled. Data were collected from March 18, 2011, through June 25, 2013. Data from the evaluable population were analyzed from July 31, 2013, to July 31, 2014. The primary efficacy outcome of the double-blind phase was the change from baseline in absolute off-time vs placebo based on patient diaries. The open-label phase focused on maintenance of treatment effect in off-time. A total of 427 patients (258 men [60.4%] and 169 women [39.6%]; mean [SD] age, 63.1 [8.8] years) were randomized to a 25-mg/d (n = 129) or a 50-mg/d (n = 154) dosage of opicapone or to placebo (n = 144). Of these, 376 patients completed the double-blind phase and entered the open-label phase, of whom 286 completed 1 year of open-label treatment. At the end of the double-blind phase, the least squares mean change (SE) in off-time was -64.5 (14.4) minutes for the placebo group, -101.7 (14.9) minutes for the 25-mg/d opicapone group, and -118.8 (13.8) minutes for the 50-mg/d opicapone group. The adjusted treatment difference vs placebo was significant for the 50-mg/d opicapone group (treatment effect, -54.3 [95% CI, -96.2 to -12.4] minutes; P = .008), but not for the 25-mg/d opicapone group (treatment effect, -37.2 [95% CI, -80.8 to 6.4] minutes; P = .11). The off-time reduction was sustained throughout the open-label phase (-126.3 minutes at 1-year open-label end point). The most common adverse events in the opicapone vs placebo groups were dyskinesia, constipation, and dry mouth. Fifty-one patients (11.9%) discontinued from the study during the double-blind phase. Treatment with a 50-mg once-daily dose of opicapone was associated with a significant reduction in mean daily off-time in levodopa-treated patients with PD and motor fluctuations, and this effect is maintained for at least 1 year. Opicapone was safe and well tolerated. clinicaltrials.gov Identifier: NCT01227655.

Current treatment and future prospects of dopa-induced dyskinesias.

Levodopa-induced dyskinesias (LID) are one of the main issues in the management of Parkinson's disease (PD); once these dyskinesias are established treatment becomes difficult, so preventive strategies should be first evaluated. Although levodopa (LD) treatment has recently been related as risk factor for LID, the main strategy to delay LID is to start PD treatment with dopamine agonists, adding LD at low doses. After LID onset, approaches include reducing single LD doses, reducing or discontinuing monoamine oxidase type B/catechol O-methyltransferase (MAO-B/COMT) inhibitors and extended-release (ER) LD. Amantadine represents the best antidyskinetic tool, and ER amantadine is the most promising upcoming antidyskinetic drug. New LD formulations such as IPX-066 (able to provide continuous dopaminergic stimulation) also represent promising new approaches. The involvement of a nondopaminergic system in the pathogenesis of LID suggests that the modulation of glutamate, serotonin and adenosine could have potential as new upcoming drug targets, but the role of such drugs will still need to be confirmed in randomized controlled trials.

Concerted actions of the catechol O-methyltransferase and the cytosolic sulfotransferase SULT1A3 in the metabolism of catecholic drugs

Catecholic drugs had been reported to be metabolized through conjugation reactions, particularly methylation and sulfation. Whether and how these two Phase II conjugation reactions may occur in a concerted manner, however, remained unclear. The current study was designed to investigate the methylation and/or sulfation of five catecholic drugs. Analysis of the spent media of HepG2 cells metabolically labeled with [35S]sulfate in the presence of individual catecholic drugs revealed the presence of two [35S]sulfated metabolites for dopamine, epinephrine, isoproterenol, and isoetharine, but only one [35S]sulfated metabolite for apomorphine. Further analyses using tropolone, a catechol O-methyltransferase (COMT) inhibitor, indicated that one of the two [35S]sulfated metabolites of dopamine, epinephrine, isoproterenol, and isoetharine was a doubly conjugated (methylated and sulfated) product, since its level decreased proportionately with increasing concentrations of tropolone added to the labeling media. Moreover, while the inhibition of methylation resulted in a decrease of the total amount of [35S]sulfated metabolites, sulfation appeared to be capable of compensating the suppressed methylation in the metabolism of these four catecholic drugs. A two-stage enzymatic assay showed the sequential methylation and sulfation of dopamine, epinephrine, isoproterenol, and isoetharine mediated by, respectively, the COMT and the cytosolic sulfotransferase SULT1A3. Collectively, the results from the present study implied the concerted actions of the COMT and SULT1A3 in the metabolism of catecholic drugs.

Bioanalytical chromatographic methods for the determination of catechol- O-methyltransferase inhibitors in rodents and human samples: A review

In the past years, it has been recognised that the levodopa therapy may be improved with therapeutic regimens including a catechol- O-methyltransferase (COMT) inhibitor. At the present time, tolcapone and entacapone are the only two COMT inhibitors available in the market. However, further COMT inhibitors are under development for Parkinson's disease, namely nebicapone and opicapone (formerly known as BIA 9-1067). In addition, the nitecapone, another well-known COMT inhibitor, is also in preclinical development but for neuropathic pain. Since the 1990s different liquid chromatography methods have been developed and validated to quantify tolcapone, entacapone, nitecapone, nebicapone and some metabolites in biological samples, particularly in plasma samples obtained from rodent and human species. These bioanalytical methods have been primarily used to support pharmacokinetic assays with such COMT inhibitors in non-clinical and clinical studies. As these inhibitors present hydrophobic groups in their chemical structures, reversed-phase liquid chromatography has been used as the major approach for the determination of such compounds, especially high-performance liquid chromatography coupled to ultraviolet detection (HPLC-UV), electrochemical detection (HPLC-ECD) and mass spectrometry detection (HPLC–MS). Regarding the sample preparation, the traditional liquid–liquid extraction (LLE) and solid-phase extraction (SPE) were also the most widely used procedures for extraction of the analytes of interest prior to the analysis of samples. Thus, this review aimed to gather, for the first time, sufficient background information about the bioanalytical chromatographic methods which have been already developed and applied for the determination of tolcapone, entacapone, nitecapone, nebicapone and their metabolites. Moreover, some pharmacokinetic aspects of the COMT inhibitors with interest from a bioanalytical perspective were also addressed.

Use of antiparkinson medications among elderly Medicare beneficiaries with Parkinson's disease

Background: Antiparkinson drugs (APDs) are the mainstay in the management of Parkinson's disease (PD). However, the use of APDs has not been investigated in a nationally representative sample. Objectives: This study aimed to describe the prevalence and patterns of APD use and to identify determinants of APD use among elderly Medicare beneficiaries with PD. Methods: Data from the Medicare Current Beneficiary Survey and Medicare claims from 2000 to 2003 were used to identify beneficiaries ≥65 years of age with PD. The APDs included in the study were levodopa, dopamine agonists, monoamine oxidase-B inhibitors, amantadine, anticholinergic agents, and catechol- O-methyltransferase inhibitors. The annual prevalence of APD use was calculated; patterns of APD use were measured by drug class and type of drug regimens (monotherapy or combination therapy). Potential determinants of APD use included sociodemographic characteristics (age, sex, race, education, marital status, and annual income), self-reported health status, residential status (institution or community), prescription drug coverage, disability (functional, physical, and mental), and disease-specific factors (dementia, depression, and other comorbidities). Multivariate logistic regression analyses with generalized estimating equations were used to estimate odds ratios (ORs) of any APD use associated with the determinants. Results: The data revealed 571 beneficiaries with PD (30.1% aged ≥85 years, 55.0% female, 88.3% white), who were observed for a total of 924 person-years. The annual prevalence of APD use was 58.2% (538/924). Levodopa was the most frequently used agent, either as monotherapy or in combination with other APDs (85.5%; 460/538). Multivariate analyses found that patients 65 to 74 years of age (OR = 0.70; 95% CI, 0.49–0.99; P < 0.05) and those ≥85 years of age (OR = 0.57; 95% CI, 0.40–0.81; P < 0.01) were less likely to use APDs than were patients aged 75 to 84 years of age. Patients who had attained a high level of education (more than a high school diploma) were more likely to use APDs than were patients with a low level of education (a high school diploma or less) (OR = 1.51; 95% CI, 1.04–2.19; P < 0.05). In addition, institutionalization (OR = 1.78; 95% CI, 1.17–2.71; P < 0.01), prescription drug coverage (OR = 1.50; 95% CI, 1.15–1.94; P < 0.01), activities of daily living (ADLs) (OR = 1.47; 95% CI, 1.16–1.87; P < 0.01), and depression (OR = 1.25; 95% CI, 1.02–1.53; P < 0.05) were significantly associated with use of APDs. The probability of APD use was lower among those with dementia than among those without dementia (OR = 0.62; 95% CI, 0.48–0.80; P < 0.001). Conclusions: Almost half of the elderly Medicare beneficiaries with PD in this study did not use any APD between 2000 and 2003. Levodopa was the most frequently used APD, either as monotherapy or in combination with other APDs. The identified determinants of APD use (age, education, prescription drug coverage, ADLs, dementia, depression, and residing in an institution) may be helpful in developing interventions for this population.

Entacapone and Tolcapone, Two Catechol O-Methyltransferase Inhibitors, Block Fibril Formation of α-Synuclein and β-Amyloid and Protect against Amyloid-induced Toxicity

Parkinson disease (PD) is the second most common neurodegenerative disorder after Alzheimer disease (AD). There is considerable consensus that the increased production and/or aggregation of alpha-synuclein (alpha-syn) plays a central role in the pathogenesis of PD and related synucleinopathies. Current therapeutic strategies for treating PD offer mainly transient symptomatic relief and aim at the restitution of dopamine levels to counterbalance the loss of dopaminergic neurons. Therefore, the identification and development of drug-like molecules that block alpha-synuclein aggregation and prevent the loss of dopaminergic neurons are desperately needed to treat or slow the progression of PD. Here, we show that entacapone and tolcapone are potent inhibitors of alpha-syn and beta-amyloid (Abeta) oligomerization and fibrillogenesis, and they also protect against extracellular toxicity induced by the aggregation of both proteins. Comparison of the anti-aggregation properties of entacapone and tolcapone with the effect of five other catechol-containing compounds, dopamine, pyrogallol, gallic acid, caffeic acid, and quercetin on the oligomerization and fibrillization of alpha-syn and Abeta, demonstrate that the catechol moiety is essential for the anti-amyloidogenic activity. Our findings present the first characterization of the anti-amyloidogenic properties of tolcapone and entacapone against both alpha-synuclein and Abeta42 and highlight the potential of this class of nitro-catechol compounds as anti-amyloidogenic agents. Their inhibitory properties, mode of action, and structural properties suggest that they constitute promising lead compounds for further optimization.

Continuous Dopaminergic Stimulation in Parkinson's Disease - What Have We Learned from Positron-emission Tomography?

The hypothesis that pulsatile stimulation of striatal dopamine receptors in Parkinson's disease (PD) induces molecular and physiological changes in basal ganglia neurons and may contribute to the development of motor complications has led to the design of therapeutic strategies that provide more continuous dopaminergic stimulation. Newer agents and drug-delivery systems, such as slow-release preparations, catechol- O-methyltransferase and monoamine oxidase inhibitor agents, apomorphine and Duodopa™infusions, represent a significant step towards less pulsatile dopaminergic administration. However, their efficacy in providing steady brain levels of dopaminergic stimulation in the short and longer term has not yet been proved in patients. This article briefly reviews and discusses the findings of published positron-emission tomography (PET) studies that support or oppose the value of continuous dopaminergic stimulation in PD. The potential future value of PET for proof of mechanism in this area is also debated.

Entacapone, a catechol- O-methyltransferase inhibitor, improves the motor activity and dopamine content of basal ganglia in a rat model of Parkinson's disease induced by Japanese encephalitis virus

Levodopa is the main medication used for the treatment of Parkinson's disease. However, dyskinesia and wearing-off appear after the administration of high-dose levodopa for a long period. To combat the dyskinesia and wearing-off, levodopa is used together with a dopamine (DA) receptor agonist, and the amount of levodopa is decreased. We have reported the monoamine oxidase (MAO)-B inhibitor selegiline to be effective for treating motor dysfunction in Parkinson's disease model rats. We analyzed the improvement in motor functions and catecholamine contents in various brain regions induced by a combination of the catechol- O-methyltransferase (COMT) inhibitor entacapone and a levodopa/dopadecarboxylase inhibitor (DDCI) in Japanese encephalitis virus (JEV) induced Parkinson's disease model rats. Entacapone (10 mg/kg) was administered via a single oral administration with levodopa/DDCI (10 mg/kg). The motor functions of the JEV model rats were significantly worsened, compared with those of the healthy control rats. The motor functions in the Parkinson's disease model rats were significantly recovered to the same levels as the healthy control rats by the combined administration of entacapone and levodopa/DDCI. A significant improvement in motor function was not demonstrated in the case of the administration of levodopa/DDCI alone. The striatal DA concentrations in the model rat brains were significantly increased by using levodopa/DDCI together with entacapone. Motor function was recovered by raising the striatum DA density in the model rats. Thus, COMT inhibitors are useful for decreasing the amount of levodopa administered to Parkinson's disease patients.

NAD(P)H:quinone oxidoreductase 1 Arg139Trp and Pro187Ser polymorphisms imbalance estrogen metabolism towards DNA adduct formation in human mammary epithelial cells

Estrogens (estrone, E 1; estradiol, E 2) are oxidized in the breast first to catechols and then to form two ortho-quinones (E 1/2-3,4-Q) that react with DNA to form depurinating adducts, which lead to mutations associated with breast cancer. NAD(P)H:quinone oxidoreductase 1 (NQO1) reduces these quinones back to catechols, and thus may protect against this mechanism. We examined whether the inheritance of two polymorphic variants of NQO1 (Pro187Ser or Arg139Trp) would result in poor reduction of E 1/2-3,4-Q in normal human mammary epithelial cells (MCF-10F) and increased depurinating adduct formation. An isogenic set of stably transfected normal human breast epithelial cells (MCF-10F) that express a truncated (135Stop), the wild-type, the 139Trp variant or the 187Ser variant of human NQO1 cDNA was constructed. MCF-10F cells showed a low endogenous NQO1 activity. NQO1 expression was examined by RT-PCR and Western blotting, and catalytic activity of reducing E 2-3,4-Q to 4-hydroxyE 1/2 and associated changes in the levels of quinone conjugates (4-methoxyE 1/2, 4-OHE 1/2-2-glutathione, 4-OHE 1/2-2-Cys and 4-OHE 1/2-2- N-acetylcysteine) and depurinating DNA adducts (4-OHE 1/2-1-N3Ade and 4-OHE 1/2-1-N7Gua) were examined by HPLC with electrochemical detection, as well as by ultra-performance liquid chromatography with tandem mass spectrometry. The polymorphic variants transcribed comparably to the wild-type NQO1, but produced ∼2-fold lower levels of the protein, suggesting that the variant proteins may become degraded. E 1/2-3,4-Q toxicity to MCF-10F cells (IC50 = 24.74 μM) was increased (IC50 = 3.7 μM) by Ro41-0960 (3 μM), a catechol- O-methyltransferase inhibitor. Cells expressing polymorphic NQO1 treated with E 2-3,4-Q with or without added Ro41-0960, showed lower ability to reduce the quinone (∼50% lower levels of the free catechols and ∼3-fold lower levels of methylated catechols) compared to the wild-type enzyme. The increased availability of the quinones in these cells did not result in greater glutathione conjugation. Instead, there was increased (2.5-fold) formation of the depurinating DNA adducts. Addition of Ro41-0960 increased the amounts of free catechols, quinone conjugates and depurinating DNA adducts. NQO1 polymorphic variants (Arg139Trp and Pro187Ser) were poor reducers of estrogen-3,4-quinones, which caused increased formation of estrogen-DNA adduct formation in MCF-10F cells. Therefore, the inheritance of these NQO1 polymorphisms may favor the estrogen genotoxic mechanism of breast cancer.

Identification of metabolite profiles of the catechol- O-methyl transferase inhibitor tolcapone in rat urine using LC/MS-based metabonomics analysis

The process of drug metabolite identification is extremely important for drug efficacy, safety and pharmacokinetics. The traditional method usually involves using a drug with a radioactive labeled nuclei and/or isolating major drug metabolites by HPLC before applying MS and NMR analyses, which requires trained specialists to handle the radioactive compounds and is time consuming for offline-HPLC separation. A method using mass spectrometry-based metabonomics combined with multivariate statistical analysis was applied to rapidly identify metabolite profiles of tolcapone, a catechol- O-methyl transferase inhibitor for Parkinson's disease treatment. The tolcapone metabolites were identified based on the accurate mass measurement (<3 ppm) and MS 2 mass spectrum. In total, 16 tolcapone metabolites were detected and identified, 6 of which have not been reported previously. Our results indicate that the method has the capability to accelerate the process of identifying drug metabolites, ultimately reduce drug development costs, and make the process safer without requiring a drug with radioactive nuclei. Most importantly, the assay can detect the major and minor drug metabolites in a global view. Furthermore, since tolcapone has been associated with idiosyncratic drug induced liver toxicity the rapid detection of tolcapone-related metabolites can provide mechanistic toxicity information related to drug metabolism and the formation of reactive drug metabolites.