Clinical experience with the novel levodopa formulation entacapone + levodopa + carbidopa (Stalevo®)

Levodopa is the main pharmacologic treatment for Parkinson's disease. However, the long-term administration of levodopa is associated with the development of motor complications which can seriously compromise patient function. Increasing evidence indicates that such problems are related to abnormal pulsatile stimulation of striatal dopamine receptors and that treatments providing more continuous stimulation reduce the risk of motor complications. It is possible that administering levodopa with a reversible catechol-O-methyl transferase inhibitor at frequent intervals might reduce the risk of these complications. Stalevo (Orion) combines levodopa, the dopa-decarboxylase inhibitor carbidopa and the catechol-O-methyl transferase inhibitor entacapone in a single tablet. This review provides an overview of the initial clinical experience gained with Stalevo during clinical trials, including several case studies.

Recent advances in Parkinson’s disease therapy: use of monoamine oxidase inhibitors

Monoamine oxidase inhibitors inhibit dopamine metabolism and are therefore effective in treating Parkinson's disease, a condition associated with progressive striatal dopamine deficiency secondary to degeneration of dopaminergic neurons in the substantia nigra. Selegiline is currently the most widely used monoamine oxidase-B inhibitor for Parkinson's disease, but has a low and variable bioavailability, and is metabolized to L-methamphetamine and L-amphetamine that carry a risk for potential neurotoxicity. There are two new approaches that circumvent these potential disadvantages. First, selegiline orally disintegrating tablets provide a novel delivery form of selegiline, avoiding first pass metabolism by rapid absorption through the oral mucosa, thus leading to significantly lower plasma concentrations of L-metamphetamine and L-amphetamine. Selegiline orally disintegrating tablets prove to be clinically effective and safe in patients with moderately advanced Parkinson's disease. Second, rasagiline is a new monoamine oxidase inhibitor, without known neurotoxic metabolites. In large clinical trials, rasagiline proves effective as monotherapy in early Parkinson's disease, as well as adjunctive therapy to levodopa in advanced disease. Clinical data suggest, in addition, a disease-modifying effect of rasagiline that may correlate with neuroprotective activity of monoamine oxidase-B inhibitors in animal models of Parkinson's disease.

Pramipexole in the treatment of Parkinson’s disease: new developments

The nonergot dopamine agonist pramipexole is an efficient and safe drug for the treatment of Parkinson's disease. Clinicians may favor pramipexole over other dopamine agonists because of its suggested higher tolerability with respect to peripheral dopaminergic side effects. Importantly, nonergot dopamine agonists such as pramipexole may not cause restrictive valvular heart disease and may therefore represent the first choice in patients with valvular lesions under treatment with ergot dopamine agonists. However, particular caution has to be exercised in younger Parkinson's disease patients with a shorter disease duration regarding the occurrence of sudden onset of sleep. In light of cost-effectiveness and quality-of-life issues, its final significance for the initial treatment of patients with early Parkinson's disease remains to be determined.

[Levodopa: the story continues]

The history of development of the drug levodopa is described. It is emphasized that the conception of continuous dopaminergic stimulation in treatment of Parkinson's disease is of great importance. Special attention is drawn to the studies on efficacy and safety of levodopa-carbidopa intestinal gel, quality of life of patients treated with this drug as well as to the experience of long-term treatment.

The use of bifunctional NOP/mu and NOP receptor selective compounds for the treatment of pain, drug abuse, and psychiatric disorders

The NOP receptor, the fourth receptor in the opioid receptor family, is found throughout the brain and is involved in a variety of CNS systems and pathways. The endogenous ligand for NOP receptors, nociceptin/orphanin FQ (now called N/OFQ), was originally thought to increase a painful stimulus since intracerebroventricular (i.c.v.) administration of this heptadecapeptide led to a decrease in tail-flick and hot-plate latency in mice. Further studies suggested that N/OFQ blocks opiate analgesia when administered i.c.v. but potentiates opiate analgesia and has antinociceptive activity when administered intrathecally. I.c.v. administration of N/OFQ has other beneficial actions including inhibition of reward induced by several different abused drugs, as well as anti-anxiety activity. Recent work has demonstrated that individual small molecules that activate both NOP and mu receptors possess mu-mediated antinociceptive activity with reduced reward, as determined by conditioned place preference tests. Furthermore, selective NOP receptor agonists appear to be active in certain chronic pain models and reduce both drug craving and anxiety. NOP receptor antagonists may also have therapeutic benefits since both peptide and small molecule antagonists have anti-depressant activity in two different animal models. Therefore, both selective NOP receptor compounds and non-selective compounds, with both NOP receptor and mu opioid receptor activity, appear to have potential for clinical use for several neurological and psychiatric disorders including acute and chronic pain, drug abuse, anxiety and depression.

Levodopa microparticles for pulmonary delivery: photodegradation kinetics and LC stability-indicating method

Levodopa, (S)-2-amino-3-(3,4-dihydroxyphenyl) propanoic acid, is still considered the gold standard treatment for Parkinson's disease. However, oral levodopa shows poor pharmacokinetics and its efficacy becomes problematic with the progression of the disease. Pulmonary delivery using the association of the polymers: chitosan, hyaluronic acid and HPMC, represents a novel approach to overcome this problem. A stability-indicating liquid chromatography method for the quantitative determination of levodopa microparticles for pulmonary delivery was developed as well as its photodegradation kinetics in solution. The developed and validated method was applied for the analyses of the novel formulation as well as for protocols of stability studies.

LC/MS/MS study for identification of entacapone degradation product obtained by photodegradation kinetics

Entacapone is indicated for clinical use as an adjunct to levodopalcarbidopa to treat patients with idiopathic Parkinson's Disease who experience the signs and symptoms of end-of-dose wearing-off. The aim of this study was to determine the photodegradation kinetics and to elucidate the structure of the main degradation product. The stability of entacapone was studied in order to investigate the degradation kinetics of this drug using LC as a stability indicator. Entacapone was subjected to accelerated photodegradation. This study was carried out with methanolic solutions, prepared from coated tablets, in quartz cells under UV light at 254 nm. The degradation process of entacapone in solutions can be described by second-order kinetics under the experimental conditions used in this study. The LC/MS/MS determinations revealed that in the above conditions the photodegraded product formed the geometric isomer of entacapone (Z-entacapone). The obtained results show the importance of appropriate light protection during the drug development process, storage, and handling.

2-Azetidinone--a new profile of various pharmacological activities

2-azetidinone, a β-lactam four member heterocyclic compound involved in research aimed to evaluate new products that possess interesting biological activities. These compounds reported for their antimicrobial and antifungal activities. Successful introduction of aztreonam as a potent inhibitor of cephalosporinase and ezetimibe as a cholesterol absorption inhibitor proved potential of 2-azetidinone moiety. Subsequently 2-azetidinones were highlighted as a potent mechanism based inhibitor of several enzymes like human tryptase, chymase, thrombin, leukocyte elastase, human cytomegalovirus protease and serine protease enzyme. These derivatives also known to possess antitubercular, anti-inflammatory, antitumor, anti-HIV, antiparkinsonian, antidiabetic and vasopressin V1a antagonist activity. The present review article focuses on the pharmacological profile of 2-azetidinones with their potential activities.

Recent progress in the discovery of adenosine A(2A) receptor antagonists for the treatment of Parkinson's disease

Antagonism of the adenosine A2A receptor has emerged as a promising non-dopaminergic approach for the potential treatment of Parkinson's disease (PD). Several pharmaceutical and academic institutions have ongoing research programs in this area, and orally efficacious A2A receptor antagonists have been advanced into clinical development. Traditionally, antagonists of the A2A receptor are classified as xanthine and non-xanthine derivatives. This review provides a detailed summary of the recent SAR development that has led to the discovery of promising non-xanthine-based A2A receptor antagonists. The current clinical status and the potential utility of A2A receptor antagonists in indications other than PD are also discussed.

Evaluation and optimization of preparative variables for controlled-release floating microspheres of levodopa/carbidopa

Levodopa, a prodrug of dopamine, is the first line drug in the treatment of Parkinson's disease. All current levodopa products are formulated in combination with aromatic amino acid decarboxylase inhibitors such as carbidopa or benserazide to prevent the peripheral metabolism of levodopa. The objective of the present investigation was to produce floating microspheres of carbidopa (CD)/levodopa (LD) to enhance their efficacy by increasing their gastric residence time, which is major technique to improve efficacy of narrow absorption window drugs. The microspheres were prepared by the o/w emulsion-solvent diffusion method using polymers hydroxypropylmethyl cellulose K15 M (HPMC K15 M) and ethyl cellulose (EC). The effects of various formulation and process variables on the particle size, in vitro floating behavior, percent drug entrapment, and in vitro drug release were studied. The size and surface morphology of prepared microspheres were characterized by optical and scanning electron microscopy, respectively. In vitro drug release studies were performed and drug release kinetics was evaluated using the linear regression analysis. The prepared microspheres exhibited prolonged drug release (approximately 10h) and remained buoyant for >12 h. Spherical and smooth-surfaced microspheres with encapsulation efficiency ranging from 43% to 80% were obtained. In vitro studies demonstrated diffusion-controlled drug release from the microspheres.

[Protecting effect of Cistanche extracts on MPP+-induced injury of the Parkinson's disease cell model]

OBJECTIVE

To investigate the potential protective role of Cistanche extracts on 1-methyl-4-phenylpyridinium ion (MPP(+))-induced Parkinson's disease (PD) cellular model, and to find out whether this effect is achieved through the regulation of growth arrest- and DNA damage-induced gene 153 (GADD153).

METHODS

MPP(+))-induced cellular injury and the protective effect of Cistanche extracts on the SH-SY5Y cell line viability treated by MPP(+)) were investigated by using methyl thiazolyl tetrazolium (MTT) assay. The mRNA of GADD153 in SH-SY5Y cell line treated by MPP(+)) and Cistanche extracts were evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR). The protein level of GADD153 in SH-SY5Y was assessed by Western blotting.

RESULTS

Cistanche extracts (100 mug/ml) increased the cell viability (P<0.01). And the mRNA of GADD153 in the Cistanche extracts pretreatment group was much less than that in the MPP(+)) group (P<0.01). The result of Western blotting showed that GADD153 had a lower level in the Cistanche extracts pretreatment group, compared with MPP(+)) group, especially in the 100 microg/ml group (P<0.01).

CONCLUSION

Cistanche extracts pretreatment has a protective effect on the MPP(+))-treated SH-SY5Y cell line, and its down-regulation of GADD153 may contribute to the effect.

Adenosine A2A receptor antagonists as novel anti-Parkinsonian agents: a review of structure-activity relationships

The adenosine A2A receptor (AA2AR) has emerged as an attractive target for the treatment of Parkinson's disease. Evidence suggests that antagonists of the AA2AR may be neuroprotective and may help to alleviate the symptoms of Parkinson's disease. During last decade, many efforts have been accomplished searching potent and selective AA2AR antagonists. In this field, various xanthines and non-xanthine heterocyclic compounds of monocyclic, bicyclic and tricyclic nucleus possessing very good affinity with a broad range of selectivity have been proposed. The aim of this article is to summarize available data on different chemical classes of AA2AR antagonists including those in clinical development, and briefly present an overview of the structure-activity relationships found for these compounds.

Design, biometric simulation and optimization of a nano-enabled scaffold device for enhanced delivery of dopamine to the brain

This study focused on the design, biometric simulation and optimization of an intracranial nano-enabled scaffold device (NESD) for the site-specific delivery of dopamine (DA) as a strategy to minimize the peripheral side-effects of conventional forms of Parkinson's disease therapy. The NESD was modulated through biometric simulation and computational prototyping to produce a binary crosslinked alginate scaffold embedding stable DA-loaded cellulose acetate phthalate (CAP) nanoparticles optimized in accordance with Box-Behnken statistical designs. The physicomechanical properties of the NESD were characterized and in vitro and in vivo release studies performed. Prototyping predicted a 3D NESD model with enhanced internal micro-architecture. SEM and TEM revealed spherical, uniform and non-aggregated DA-loaded nanoparticles with the presence of CAP (FTIR bands at 1070, 1242 and 2926 cm(-1)). An optimum nanoparticle size of 197 nm (PdI=0.03), a zeta potential of -34.00 mV and a DEE of 63% was obtained. The secondary crosslinker BaCl(2) imparted crystallinity resulting in significant thermal shifts between native CAP (T(g)=160-170 degrees C; T(m)=192 degrees C) and CAP nanoparticles (T(g)=260 degrees C; T(m)=268 degrees C). DA release displayed an initial lag phase of 24 h and peaked after 3 days, maintaining favorable CSF (10 microg/mL) versus systemic concentrations (1-2 microg/mL) over 30 days and above the inherent baseline concentration of DA (1 microg/mL) following implantation in the parenchyma of the frontal lobe of the Sprague-Dawley rat model. The strategy of coupling polymeric scaffold science and nanotechnology enhanced the site-specific delivery of DA from the NESD.

In vitro dopaminergic neuroprotective and in vivo antiparkinsonian-like effects of Delta 3,2-hydroxybakuchiol isolated from Psoralea corylifolia (L.)

Cocktail recipes containing Psoralea corylifolia seeds (PCS) are used to empirically treat Parkinson disease. A PCS isolate Delta(3),2-hydroxybakuchiol (BU) can inhibit dopamine uptake in dopamine transporter (DAT) transfected Chinese hamster ovary (CHO) cells, and dopamine reuptake blockade may provide an alternative approach for ameliorating parkinsonism. Here, we assessed the potential dopaminergic neuroprotective, and antiparkinsonian-like activity of BU. BU sample size was increased by using a scale-up extraction paradigm. Pharmacologically, BU significantly protected SK-N-SH cells from 1-methyl-4-phenylpyridinium (MPP(+)) insult, produced striking inhibitory actions on dopamine/norepinephrine uptake and WIN35,428 binding in synaptosomes on in vivo administration, and significantly preventing poor performance on rotarod and dopaminergic loss in substantia nigra in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mice. BU acts by protecting dopaminergic neurons from MPP(+) injury and preventing against MPTP-induced behavioral and histological lesions in the Parkinson's disease (PD) model, possibly by inhibiting monoamine transporters. These findings suggest that BU could be meaningful in PD treatment.

Recent progress in the development of mGluR4 positive allosteric modulators for the treatment of Parkinson's disease

This article describes recent advances in the development and biological evaluation of small molecule mGluR4 positive allosteric modulators (PAMs), and, to a lesser extent, orthosteric agonists. Due to its expression in the basal ganglia, the Family 3 GPCR metabotropic glutamate receptor subtype 4 (mGluR4) has recently garnered a great deal of attention as a putative target for the treatment of Parkinson's disease and a variety of other CNS disorders. Until 2008, with the exception of the prototypical mGluR4 PAM (-)-PHCCC, very few small molecule tools existed to probe the role of selective activation of mGluR4. This review will focus on the explosion of novel mGluR4 PAMs reported in the past year and the further preclinical validation of mGluR4 activation as a potentially groundbreaking treatment for Parkinson's disease.

Antiparkinson prodrugs

Parkinson’s disease (PD) is a progressive, neurodegenerative disorder which involves the loss of dopaminergic neurons of the substantia nigra pars compacta. Current therapy is essentially symptomatic, and L-Dopa (LD), the direct precursor of dopamine (DA), is the treatment of choice in more advanced stages of the disease. Substitution therapy with LD is, however, associated with a number of acute problems. The peripheral conversion of LD by amino acid decarboxylase (AADC) to DA is responsible for the typical gastrointestinal (nausea, emesis) and cardiovascular (arrhythmia, hypotension) side effects. To minimize the conversion to DA outside the central nervous system (CNS) LD is usually given in combination with peripheral inhibitors of AADC (carbidopa and benserazide). In spite of that, other central nervous side effects such as dyskinesia, on-off phenomenon and end-of-dose deterioration still remain. The main factors responsible for the poor bioavailability and the wide range of inter- and intra-patient variations of plasma levels are the drug’s physical-chemical properties: low water and lipid solubility, resulting in unfavourable partition, and the high susceptibility to chemical and enzymatic degradation. In order to improve the bioavailability, the prodrug approach appeared to be the most promising and some LD prodrugs have been prepared in an effort to solve these problems. We report here a review of progress in antiparkinson prodrugs, focusing on chemical structures mainly related to LD, DA and dopaminergic agonists.

Zonisamide for the treatment of Parkinson's disease

Zonisamide is an antiepileptic drug widely used to treat seizures worldwide. In addition to epilepsy, zonisamide may have beneficial efficacy in various neurological or psychiatric diseases. This article reviews the structure, mechanism of action, pharmacokinetics and possible antiparkinsonian action of zonisamide. A multicentered, randomized, double-blind, placebo-controlled study conducted in Japan provided data suggesting that zonisamide, as an add-on treatment, has efficacy in treating motor symptoms in patients with Parkinson's disease (PD). Zonisamide may be effective in reducing the duration of 'off' time in patients with PD treated with L-DOPA. The therapeutic doses of zonisamide for the treatment of PD are 50-100 mg/day, considerably lower than those for the treatment of epilepsy (200-400 mg/day). It is expected that zonisamide will be safe and tolerated in patients with PD, as it has been used as an antiepileptic for more than 15 years; however, further studies are required to evaluate its safety and tolerability in the treatment of PD. The pharmacological mechanisms of the beneficial actions of zonisamide in PD remain unclear. Various hypotheses have been proposed, but the supporting data are not yet sufficient to draw any conclusions. Further basic research is required to advance our understanding of the antiparkinsonian mechanism of zonisamide.

Apomorphine in the treatment of Parkinson's disease

Motor fluctuations, refractory to conventional medical management, are one of the most troubling aspects of Parkinson's disease. Apomorphine is a dopaminergic agent that has been known to the medical community for more than a century, but has only recently been developed to treat such motor fluctuations. In this article, the authors review the historical background, structure, mechanism of action, pharmacologic properties, clinical trials, indications and side effects, as well as avenues of further research, of apomorphine.

Expedient five-step synthesis of SIB-1508Y from natural nicotine

Altinicline (SIB-1508Y), an anti-Parkinson's agent, was prepared in five steps from natural nicotine in 32% overall yield via a regioselective substitution of the pyridine ring of (S)-nicotine.

Quantitative determination of L-DOPA in tablets by high performance thin layer chromatography

A densitometric high performance thin-layer chromatographic (HPTLC) method was developed and validated for quantitative analysis of L-DOPA in tablets. Chromatographic separation was achieved on precoated silica gel F 254 HPTLC plates using a mixture of acetone-chloroform-n-butanol-acetic acid glacial-water (60:40:40:40:35 v/v/v/v/v) as mobile phase. Quantitative analysis was carried out at a wavelength of 497 nm. The method was linear between 100 and 500 ng/microL, with a correlation coefficient of 0.999. The intra-assay variation was between 0.26 and 0.65% and the interassay was between 0.52 and 2.04%. The detection limit was 1.12 ng/microL, and the quantification limit was 3.29 ng/microL. The accuracy ranged from 100.40 to 101.09%, with a CV not higher than 1.40%. The method was successfully applied to quantify L-DOPA in real pharmaceutical samples, including the comparison with HPLC measurements. The method was fast, specific, with a good precision, and accurate for the quantitative determination of L-DOPA in tablets.

Continuous wavelet and derivative transforms for the simultaneous quantitative analysis and dissolution test of levodopa–benserazide tablets

Simultaneous analyses and dissolution tests of levodopa-benserazide tablets were carried out by continuous wavelet transform (CWT) and classic derivative spectrophotometry (DS) without using any chemical separation step. The developed two spectrophotometric resolutions are based on the transformation of the original UV spectra. The original absorption spectra of levodopa and benserazide in the concentration range of 1-80 microg/mL and 5-240 microg/mL in USP simulated gastric juice were registered in the spectral range of 250-310 nm, respectively. Various wavelet families and different spectrophotometric derivative orders were tested to find the optimal signal processing for obtaining desirable calibration graphs and reliable determinations of the investigated drugs. Under the optimized conditions of the methods, symlets wavelet family using a=128 with sixth order (SYM6-CWT) and the first derivative transform with Deltalambda=10nm were identified as optimal signal processing methods for the determinations and dissolution tests. The calibration functions for each drug were obtained by measuring the values of the CWT and derivative amplitudes. The validation of the developed methods was confirmed by analyzing various synthetic mixtures of the investigated drugs. Mean recovery values were found between 99.1% and 104.7% for DS and 100% and 102.9% for CWT, respectively for determination of BEN and LEV in synthetic mixtures. Each developed approaches were successfully applied to the simultaneous determination and dissolution test of levodopa and benserazide in their commercial tablets and a good agreement was observed.

Synthesis and biological evaluation of 1-amino-2-phosphonomethylcyclopropanecarboxylic acids, new group III metabotropic glutamate receptor agonists

Stereoisomers of 1-amino-2-phosphonomethylcyclopropanecarboxylic acid (APCPr), conformationally restricted analogues of L-AP4 (2-amino-4-phosphonobutyric acid), have been prepared and evaluated at recombinant group III metabotropic glutamate receptors. They activate these receptors over a broad range of potencies. The most potent isomer (1S,2R)-APCPr displays a similar pharmacological profile as that of L-AP4 (EC50 0.72, 1.95, >500, 0.34 microM at mGlu4, 6, 7, 8 receptors, respectively, and no effect at group I/II mGluRs). It was characterized on native receptors located in the basal ganglia (BG) where it induced a robust and reversible inhibition of synaptic transmission. It was tested in vivo in haloperidol-induced catalepsy, a model of Parkinsonian akinesia, by direct infusion in the globus pallidus of the BG. At a dose of 0.5 nmol/microL, catalepsy was significantly antagonized. This study reveals that (1S,2R)-APCPr is a potent group III mGluR agonist and confirms that these receptors may be considered as a therapeutic target in the Parkinson's disease.

A cell-based model of alpha-synucleinopathy for screening compounds with therapeutic potential of Parkinson's disease

AIM

To develop a cell-based model by stable transfection of SH-SY5Y with mutant A53T human alpha-synuclein, recapitulating neurotoxicity of alpha -synuclein overexpression.

METHODS

The overexpression of mutant alpha -synuclein was analyzed by Western blotting, immunocytochemistry, and RT-PCR. Cell viability was processed when treated with different concentrations of 1-methyl-4-phenylpyridinium (MPP+) and exogenous dopamine (DA) for 24, 48, and 72 h by 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Early apoptosis and late apoptosis/necrosis were analyzed by flow cytometry using Annexin V and propidium iodide double staining, respectively. DNA was isolated and applied to agarose gel for electrophoresis; the typical DNA "ladder"represented severe apoptosis. We also used this model to screen 99 compounds with therapeutic potential by MTT assay.

RESULTS

One of the stably-transfected clones overexpressed exogenous genes on both the protein level and the transcriptive level. Significant differences in cytotoxicity were found between the pcDNA3.1(+) group and the pcDNA3.1(+)-hm alpha-synuclein group in the presence of the same concentration of MPP+ and DA within the same incubation time. The level of either early apoptosis or late apoptosis/necrosis was remarkably increased in transfected cells compared with the control after treatment with 100 micromol/L MPP+ for 24 h. In addition, the presence of the typical DNA "ladder" was observed in the pcDNA3.1(+)-hm alpha-synuclein group when treated with 200 micromol/L MPP+ for 48 h. After the screening experiment, 12 of the 99 compounds were found to decrease DA-induced cytotoxicity on cell viability.

CONCLUSION

We established a cell-based model which is useful for studying the function of alpha-synuclein and screening compounds with therapeutic potential. In addition, it was identified that cells overexpressing A53T mutant alpha-synuclein were significantly vulnerable against MPP+ or dopamine exposures.