Effectiveness and safety of different catechol-o-methyl transferase inhibitors for patients with parkinson's disease: Systematic review and network meta-analysis

BACKGROUND

Levodopa treatment requires the addition of other drugs, such as catechol-O-methyl transferase (COMT) inhibitors, to alleviate motor fluctuations in advanced parkinson's disease (PD). However, the optimal strategy, including the type and dose of COMT inhibitors remains unknown. This systematic review and network meta-analysis aimed to assess the efficacy and safety of different COMT inhibitors and for treating PD patients.

METHODS

PubMed, Embase, Cochrane Library and Web of Science were screened up to November 20, 2022. Randomized controlled trials (RCTs) of COMT inhibitors (entacapone, opicapone, tolcapone) for PD patients were included. Eligible outcomes were total ON-time, rate of ON-time >1 h, total daily dose of levodopa therapy, mean change from baseline to final follow up in Unified Parkinson's Disease Rating Scale (UPDRS) part III scores, adverse events and dyskinesia. Network meta-analyses integrated direct and indirect evidence with placebo as a common comparator.

RESULTS

We identified 18 studies with 7564 patients. Opicapone, entacapone, and tolcapone could increase total ON-time when compared with placebo. However, opicapone (25 mg, MD 4.0, 95%CrI: 1.1-7.5) and opicapone (50 mg, MD 5.1, 95%CrI: 2.2-8.7) statistically significant increase the total ON-time. opicapone and entacapone could increase the rate of ON-time >1 h when compared with placebo. Only opicapone (5 mg) showed no statistically significant with placebo (OR 1.4, 95%CrI: 0.74-2.4). We found that opicapone (50 mg, SURCA, 0.796) is the best option compared with other treatments. TOL (200 mg) was ranked highest in the rank probability test for total daily dose of levodopa therapy, followed by OPI (50 mg), TOL (400 mg) and TOL (100 mg) in order. SUCRA rankings identified TOL (200 mg) as the most likely therapy for increasing adverse events (SUCRA 27.19%), followed by TOL (400 mg, SUCRA 27.20%) and OPI (5 mg, SUCRA 30.81%). The SUCRA probabilities were 91.6%, 75.2%, 67.9%, 59.3%, 45.6%, 41.1%, 35.1%, 24.6% and 9.4% for PLA, TOL (400 mg), ENT (100 mg), ENT (200 mg), OPI (5 mg), TOL (100 mg), OPI (25 mg), OPI (50 mg), and TOL (200 mg) respectively.

CONCLUSION

In conclusion, opicapone (50 mg) may be a better choice for treatment PD when compared with other COMT inhibitors.

A molecular basis for tetramer destabilization and aggregation of transthyretin Ala97Ser

Transthyretin (TTR)-related amyloidosis (ATTR) is a syndrome of diseases characterized by the extracellular deposition of fibrillar materials containing TTR variants. Ala97Ser (A97S) is the major mutation reported in Taiwanese ATTR patients. Here, we combine atomic resolution structural information together with the biochemical data to demonstrate that substitution of polar Ser for a small hydrophobic side chain of Ala at residue 97 of TTR largely influences the local packing density of the FG-loop, thus leading to the conformational instability of native tetramer, the increased monomeric species, and thus the enhanced amyloidogenicity of apo-A97S. Based on calorimetric studies, the tetramer destabilization of A97S can be substantially altered by interacting with native stabilizers via similarly energetic patterns compared to that of wild-type (WT) TTR; however, stabilizer binding partially rearranges the networks of hydrogen bonding in TTR variants while FG-loops of tetrameric A97S still remain relatively flexible. Moreover, TTR in complexed with holo-retinol binding protein 4 is slightly influenced by the structural and dynamic changes of FG-loop caused by A97S substitution with an approximately five-fold difference in binding affinity. Collectively, our findings suggest that the amyloidogenic A97S mutation destabilizes TTR by increasing the flexibility of the FG-loop in the monomer, thus modulating the rate of amyloid fibrillization.

Micro- and Nano-Systems Developed for Tolcapone in Parkinson’s Disease

To date there is no cure for Parkinson’s disease (PD), a devastating neurodegenerative disorder with levodopa being the cornerstone of its treatment. In early PD, levodopa provides a smooth clinical response, but after long-term therapy many patients develop motor complications. Tolcapone (TC) is an effective adjunct in the treatment of PD but has a short elimination half-life. In our work, two new controlled delivery systems of TC consisting of biodegradable PLGA 502 (poly (D,L-lactide-co-glycolide acid) microparticles (MPs) and nanoparticles (NPs) were developed and characterized. Formulations MP-TC4 and NP-TC3 were selected for animal testing. Formulation MP-TC4, prepared with 120 mg TC and 400 mg PLGA 502, exhibited a mean encapsulation efficiency (EE) of 85.13%, and zero-order in vitro release of TC for 30 days, with around 95% of the drug released at this time. Formulation NP-TC3, prepared with 10 mg of TC and 50 mg of PLGA 502, exhibited mean EE of 56.69%, particle size of 182 nm, and controlled the release of TC for 8 days. Daily i.p. (intraperitoneal) doses of rotenone (RT, 2 mg/kg) were given to Wistar rats to induce neurodegeneration. Once established, animals received TC in saline (3 mg/kg/day) or encapsulated within formulations MP-TC4 (amount of MPs equivalent to 3 mg/kg/day TC every 14 days) and NP-TC3 (amount of NPs equivalent to 3 mg/kg/day TC every 3 days). Brain analyses of Nissl-staining, GFAP (glial fibrillary acidic protein), and TH (tyrosine hydroxylase) immunohistochemistry as well as behavioral testing (catalepsy, akinesia, swim test) showed that the best formulation was NP-TC3, which was able to revert PD-like symptoms of neurodegeneration in the animal model assayed.

Formulation of Sustained Release Hydrophilic Matrix Tablets of Tolcapone with the Application of Sedem Diagram: Influence of Tolcapone's Particle Size on Sustained Release

Hydrophilic matrix tablets are a type of sustained release dosage form characterized by distributing a drug in a matrix that is usually polymeric. Tolcapone is a drug that inhibits the enzyme catechol-O-methyl transferase. In recent years, it has been shown that tolcapone is a potent inhibitor of the amyloid aggregation process of the transthyretin protein, and acts by stabilizing the structure of the protein, reducing the progression of familial amyloid polyneuropathy. The main objective of this study was to obtain a sustained release tablet of tolcapone for oral administration with a preferred dosage regimen of 1 administration every 12 or 24 h and manufactured, preferably, by direct compression. The SeDeM Diagram method has been used for the formulation development of hydrophilic matrix tablets. Given the characteristics of tolcapone, the excipient selected for the formation of the polymeric matrix was a high viscosity hydroxypropylmethylcellulose (Methocel^® K100M CR). A decrease in the particle size of tolcapone resulted in a slower dissolution release of the formulation when the concentration of the polymer Methocel^® K100M CR was below 29%. These surprising and novel results have given rise to patent number WO/2018/019997.

Benzophenone: a ubiquitous scaffold in medicinal chemistry

The benzophenone scaffold represents a ubiquitous structure in medicinal chemistry because it is found in several naturally occurring molecules which exhibit a variety of biological activities, such as anticancer, anti-inflammatory, antimicrobial, and antiviral. In addition, various synthetic benzophenone motifs are present in marketed drugs. They also represent important ingredients in perfumes and can act as photoinitiators. This review will provide an overview of benzophenone moieties with medicinal aspects synthesized in the last 15 years and will cover the most potent molecule in each report. In this review, only benzophenones with substitutions on their aryl rings, i.e. diphenyl ketone analogues, have been covered.

Multidirectional Efficacy of Biologically Active Nitro Compounds Included in Medicines

The current concept in searching for new bioactive products, including mainly original active substances with potential application in pharmacy and medicine, is based on compounds with a previously determined structure, well-known properties, and biological activity profile. Nowadays, many commonly used drugs originated from natural sources. Moreover, some natural materials have become the source of leading structures for processing further chemical modifications. Many organic compounds with great therapeutic significance have the nitro group in their structure. Very often, nitro compounds are active substances in many well-known preparations belonging to different groups of medicines that are classified according to their pharmacological potencies. Moreover, the nitro group is part of the chemical structure of veterinary drugs. In this review, we describe many bioactive substances with the nitro group, divided into ten categories, including substances with exciting activity and that are currently undergoing clinical trials.

RepTB: a gene ontology based drug repurposing approach for tuberculosis

Tuberculosis (TB) is the world’s leading infectious killer with 1.8 million deaths in 2015 as reported by WHO. It is therefore imperative that alternate routes of identification of novel anti-TB compounds are explored given the time and costs involved in new drug discovery process. Towards this, we have developed RepTB. This is a unique drug repurposing approach for TB that uses molecular function correlations among known drug-target pairs to predict novel drug-target interactions. In this study, we have created a Gene Ontology based network containing 26,404 edges, 6630 drug and 4083 target nodes. The network, enriched with molecular function ontology, was analyzed using Network Based Inference (NBI). The association scores computed from NBI are used to identify novel drug-target interactions. These interactions are further evaluated based on a combined evidence approach for identification of potential drug repurposing candidates. In this approach, targets which have no known variation in clinical isolates, no human homologs, and are essential for Mtb’s survival and or virulence are prioritized. We analyzed predicted DTIs to identify target pairs whose predicted drugs may have synergistic bactericidal effect. From the list of predicted DTIs from RepTB, four TB targets, namely, FolP1 (Dihydropteroate synthase), Tmk (Thymidylate kinase), Dut (Deoxyuridine 5′-triphosphate nucleotidohydrolase) and MenB (1,4-dihydroxy-2-naphthoyl-CoA synthase) may be selected for further validation. In addition, we observed that in some cases there is significant chemical structure similarity between predicted and reported drugs of prioritized targets, lending credence to our approach. We also report new chemical space for prioritized targets that may be tested further. We believe that with increasing drug-target interaction dataset RepTB will be able to offer better predictive value and is amenable for identification of drug-repurposing candidates for other disease indications too.

Toxicology and safety of COMT inhibitors

The development of catechol-O-methyltransferase (COMT) inhibitors for the adjunct treatment to levodopa and aromatic L-amino acid decarboxylase (AADC) inhibitors in Parkinson's disease started in the late 1950s. The first-generation inhibitors were associated with toxic properties: they induced convulsions, or they were toxic to the liver. None of them was taken into clinical use. The second-generation inhibitors entacapone and tolcapone have now been in clinical use for over a decade, and some new inhibitors are under development. The main adverse events in the use of entacapone and tolcapone are dopaminergic and dependent of the concomitant use of levodopa, but the symptoms are generally moderate or mild. Among the non-dopaminergic adverse events, diarrhea is the most prominent one induced by both entacapone and tolcapone. In clinical use, entacapone has been safe, but tolcapone is under strict regulations on liver enzyme monitoring, since in the early years, a few hepatotoxicity cases appeared, three of them with fatal outcome. The mechanism behind tolcapone-induced liver toxicity has been evaluated both in vitro and in vivo, but no clear answer exists at the moment. In the regulatory animal studies, both inhibitors have been safe with no reported toxicity. Also nebicapone, the latest of the second-generation inhibitors in clinical trials has shown some liver enzyme elevations in human subjects. New inhibitors with a structure differing from nitrocatechols are under development. No safety concerns have been reported connected to COMT inhibiton as such. COMT knockout mice are fertile without any pathologies due to the total COMT inhibition.

Tolcapone: review of its pharmacology and use as adjunctive therapy in patients with Parkinson's disease

Levodopa has been the gold standard therapy for the motor symptoms of Parkinson’s disease for more than three decades. Although it remains the most effective treatment, its long-term use is associated with motor fluctuations and dyskinesias that can be disabling for patients and difficult for physicians to manage medically. In the last 10 years, the catechol-O-methyltransferase (COMT) inhibitor tolcapone has been studied for its efficacy as an adjunctive treatment to levodopa plus a dopa decarboxylase inhibitor. Adjunctive therapy with tolcapone can significantly reduce the dose of levodopa required. Moreover, treatment with tolcapone significantly reduces wearing off and on-off periods in fluctuating patients and improves ‘on’ time in patients with stable disease. Tolcapone has assumed a new place in the arsenal of medications for Parkinson’s disease. This paper reviews the pharmacology, safety and efficacy of tolcapone in patients with advanced Parkinson’s disease. After some initial concerns about its safety, tolcapone has been shown to be safe if used and monitored according to guidelines regarding liver function. Tolcapone produces expected dopaminergic side effects, including headache, nausea, insomnia, as well as diarrhea; however, these side effects are generally mild and as a rule do not result in discontinuation of therapy.

Physiological and pathological role of alpha-synuclein in Parkinson's disease through iron mediated oxidative stress; the role of a putative iron-responsive element

Parkinson’s disease (PD) is the second most common progressive neurodegenerative disorder after Alzheimer’s disease (AD) and represents a large health burden to society. Genetic and oxidative risk factors have been proposed as possible causes, but their relative contribution remains unclear. Dysfunction of alpha-synuclein (α-syn) has been associated with PD due to its increased presence, together with iron, in Lewy bodies. Brain oxidative damage caused by iron may be partly mediated by α-syn oligomerization during PD pathology. Also, α-syn gene dosage can cause familial PD and inhibition of its gene expression by blocking translation via a newly identified Iron Responsive Element-like RNA sequence in its 5’-untranslated region may provide a new PD drug target.