Intraventricular dopamine infusion alleviates motor symptoms in a primate model of Parkinson's disease.

BACKGROUND: Continuous compensation of dopamine represents an ideal symptomatic treatment for Parkinson's disease (PD). The feasibility in intracerebroventricular administration (i.c.v.) of dopamine previously failed because of unresolved dopamine oxidation. OBJECTIVES: We aim to test the feasibility, safety margins and efficacy of continuous i.c.v. of anaerobic-dopamine (A-dopamine) with a pilot translational study in a non-human primate model of PD. METHODS: Continuous and circadian i.c.v. of A-dopamine was administered through a micro-pump connected to a subcutaneous catheter implanted into the right frontal horn of 8 non-human primates treated with 1-methyl-4- phenyl-1,2,3,6-tetrahydropyridine (MPTP). A-dopamine was assessed at acute doses previously reported for dopamine as well as evaluating the long term therapeutic index of A-dopamine in comparison to anaerobically prepared L-dopa or methyl ester L-dopa. RESULTS: Over 60 days of a continuous circadian i.c.v. of A-dopamine improved motor symptoms (therapeutic index from 30 to 70 mg/day) without tachyphylaxia. No dyskinesia was observed even with very high doses. Death after 1 to 10 days (without neuronal alteration) was only observed with doses in excess of 160 mg whereas L-dopa i.c.v. was not effective at any dose. The technical feasibility of the administration regimen was confirmed for an anaerobic preparation of dopamine and for administration of a minimal infusion volume by micro-pump at a constant flow that prevented obstruction. CONCLUSION: Continuous circadian i.c.v. of A-dopamine appears to be feasible and shows efficacy without dyskinesia with a safe therapeutic index.

Exploring the functional impact of mutational drift in LRRK2 gene and identification of specific inhibitors for the treatment of Parkinson disease.

Parkinson's disease (PD) is a disorder of the central nervous system that is caused due to the death of the dopaminergic neurons in the region of the brain called substantia nigra. Mutations in LRRK2 genes are associated with disease condition and it's been reported as crucial factor for drug resistance. Identification of deleterious mutations and studying the structural and functional impact of such mutations may lead to the identification of potential selective inhibitors. In this study, we analyzed 52 PD associated mutations, among that 20 were identified as highly deleterious. The deleterious mutations G2019S and I2020T in the kinase domain were playing a key role in causing resistance to drug levedopa. Molecular docking analyses have been performed to understand the binding affinity of levodapa with LRRK2 in wild and mutant condition. Molecular docking results show that levedopa binds differentially and obtained less number of hydrogen bonds in compared with wild type LRRK2. In addition, molecular dynamics simulations were performed to study the efficacy of docked complexes and it was observed that the efficacy of the mutant complexes (G2019S-Levodopa and I2020T-Levodopa) affected in the presence of mutation. Finally, through virtual screening approach specific inhibitors SCHEMBL6473053 and SCHEMBL1278779 have been identified that could potentially inhibit LLRK2 mutants G2019S and I2020T respectively. Over all this computational investigation correlates the impact of genotypic modulation in structure and function of drug target which enhanced in the identification of precision medicine to treat PD.

l-Dopa and dopamine conjugated naphthalenediimides modulate amyloid ß toxicity.

The process of protein misfolding and aggregation to form neurotoxic species is strongly implicated in most of the neurodegenerative disorders. In particular, amyloid beta (Aß) misfolding and aggregation is central to pathophysiological processes of Alzheimer's disease. The development of aggregation modulators has enormous implications in the discovery of effective therapeutic agents for Alzheimer's disease. Herein, we report the design and synthesis of a series of natural amino acid, l-dopa and dopamine appended derivatives of naphthalenediimide (NDI) to identify efficient aggregation modulators. Furthermore, the molecular docking studies revealed the possible binding sites and binding mode of NDI-conjugates to Aß aggregates. Among the designed NDI-conjugates, l-dopa and dopamine derivatives (NLD and NDP, respectively) showed excellent aggregation modulation efficiency (inhibition and dissolution), as shown by the thioflavin T (ThT) binding assays, dot blot analysis and in cellulo studies. The docking results from in silico studies are in good agreement with the experimental data. In addition to their significant modulation efficiency towards Aß aggregation, NLD and NDP possess antioxidant activity conducive to the development of disease-modifying therapeutic agents for the treatment of Alzheimer's disease.

Novel post-translational oligomerization of peptidyl dehydrodopa model compound, 1,2-dehydro-N-acetyldopa methyl ester.

Post-translational modification of peptidyl tyrosine to peptidyl dopa is widely observed in different marine organisms. While peptidyl dopas are oxidatively converted to dehydrodopa derivatives, nothing is known about the further fate of dehydrodopyl compounds. To fill this void, we studied the oxidation chemistry of a peptidyl dehydrodopa mimic, 1,2-dehydro-N-acetyldopa methyl ester with mushroom tyrosinase. We employed both routine biochemical studies and reversed phase liquid chromatography mass spectrometry to investigate the course of the reaction. Tyrosinase catalyzed the oxidation of 1,2-dehydro-N-acetyldopa methyl ester readily generating its typical o-quinone as the transient two-electron oxidation product. This quinone was extremely unstable and rapidly reacted with the parent compound forming benzodioxan type oligomeric products. Reaction mixture containing chemically made o-benzoquinone and 1,2-dehydro-N-acetyldopa methyl ester generated a mixed adduct of benzoquinone and 1,2-dehydro-N-acetyldopa methyl ester. Based on this finding, we propose that peptidyl dehydrodopa also exhibits a similar transformation accounting partially for the adhesive and cementing properties of dopyl proteins in nature.

Early L-dopa, but not pramipexole, restores basal ganglia activity in partially 6-OHDA-lesioned rats.

The most appropriate time for the initiation of dopaminergic symptomatic therapy in Parkinson's disease remains debatable. It has been suggested that early correction of basal ganglia pathophysiological abnormalities may have long-term beneficial effects. To test this hypothesis, we investigated the early and delayed actions of L-dopa and pramipexole, using a delayed-start protocol of treatment. The effects of early and delayed administration of these drugs on motor response, development of dyskinesias, neurogenesis and molecular markers in basal ganglia were studied in rats with a unilateral and partial 6-hydroxydopamine-induced nigrostriatal lesion. Ten days after lesioning, rats received treatment with: a) L-dopa methyl ester (25mg/kg with 6.25mg/kg of benserazide, i.p., twice a day); b) pramipexole (0.5mg/kg, sc, twice a day) or c) saline for 4weeks. Four weeks after treatment initiation, rats from the saline group were distributed in three groups that then received the following treatments: d) L-dopa, e) pramipexole or f) saline, for 4weeks more. Three animals in each treatment arm received 5-bromo-2-deoxyuridine injections (200mg/kg) 3days before starting treatment. When compared with delayed-start L-dopa, early-start L-dopa treatment induced a lower rotational response (p<0.01), an improvement in limb akinesia (p<0.05), a lower level of dyskinesia (p<0.01) and a normalization of lesion-induced molecular changes in basal ganglia. When compared with delayed-start pramipexole, early-start pramipexole induced a higher rotational response (p<0.01), but did not improve limb akinesia, induce dyskinesia nor normalize lesion-induced molecular changes. Neither significant modifications of striatal dopamine D1-D3 receptor heteromerization nor subventricular zone neurogenesis was found after any L-dopa or pramipexole treatments. Our data support a possible restoration of basal ganglia physiological mechanisms by early-start L-dopa therapy.

Pharmacokinetic evaluation of formulated levodopa methyl ester nasal delivery systems.

The objective of this study was to investigate the pharmacokinetic characteristics of levodopa (L-dopa) from nasal powder formulations using highly water-soluble levodopa methyl ester hydrochloride (LDME). In vivo pharmacokinetic studies were carried out with formulated LDME nasal powders. After oral and intravenous administration of L-dopa and carbidopa and intranasal administration LDME to the rat, L-dopa concentrations were determined in plasma and the brain using high-performance liquid chromatography. The absolute bioavailabilities of nasal preparations with and without Carbopol were 82.4 and 66.7 %, respectively, which were much higher than that of oral delivery (16.2 %). The drug-targeting efficiencies [area under the curve (AUC) in brain/AUC in plasma] of L-dopa in the nasal formulations (0.98-1.08) were much higher than that of oral preparation (0.69). These results suggest that LDME nasal powder formulations would be useful delivery systems of L-dopa to the brain.

Multipart copolyelectrolyte adhesive of the sandcastle worm, Phragmatopoma californica (Fewkes): catechol oxidase catalyzed curing through peptidyl-DOPA.

Tube-building sabellariid polychaetes have major impacts on the geology and ecology of shorelines worldwide. Sandcastle worms, Phragmatopoma californica (Fewkes), live along the western coast of North America. Individual sabellariid worms build tubular shells by gluing together mineral particles with a multipart polyelectrolytic adhesive. Distinct sets of oppositely charged components are packaged and stored in concentrated granules in separate cell types. Homogeneous granules contain sulfated macromolecules as counter-polyanion to polycationic Pc2 and Pc5 proteins, which become major components of the fully cured glue. Heterogeneous granules contain polyphosphoproteins, Pc3A/B, paired with divalent cations and polycationic Pc1 and Pc4 proteins. Both types of granules contain catechol oxidase that catalyzes oxidative cross-linking of L-DOPA. Co-secretion of catechol oxidase guarantees rapid and spatially homogeneous curing with limited mixing of the preassembled adhesive packets. Catechol oxidase remains active long after the glue is fully cured, perhaps providing an active cue for conspecific larval settlement.

Mass spectrometric studies shed light on unusual oxidative transformations of 1,2-dehydro-N-acetyldopa.

RATIONALE: Lamellarins are a group of over 70 plus bioactive marine natural compounds possessing a 6,7-dihydroxycoumarin moiety. Although they appear to derive from 3,4-dihydroxyphenylalanine (dopa), practically nothing is known about the metabolic fate of these compounds. Biochemical considerations indicate that they could arise from a N-acetyl-1,2-dehydrodopa precursor through oxidative cyclization reaction. METHODS: To assess the above hypothesis, we synthesized N-acetyl-1,2-dehydrodopa and conducted oxidation studies with commercially available mushroom tyrosinase and evaluated the course of the reaction with reversed-phase liquid chromatography/mass spectrometry (LC/MS). RESULTS: Mushroom tyrosinase readily oxidized N-acetyl-1,2-dehydrodopa - not to the normally expected quinone - but to an unstable quinone methide isomer, which rapidly cyclized to produce the dihydroxycoumarin product, 3-aminoacetyl esculetin. Interestingly, 3-aminoacetyl esculetin was further oxidized to a second quinone methide derivative that exhibited an addition reaction with the parent dihydroxycoumarin generating dimeric and other oligomeric products in the reaction mixture. CONCLUSIONS: LC/MS analysis of the N-acetyl-1,2-dehydrodopa oxidation reaction reveals not only a possible novel oxidative cyclization route for the biosynthesis of coumarin-type dehydrodopa compounds in marine organisms, but also unusual oxidative transformations of dehydro dopa derivatives.

Design, synthesis and biological evaluation of peptide derivatives of L-dopa as anti-parkinsonian agents.

A series of dipeptide derivatives of L-dopa were synthesized and investigated for their pharmacological activity using the unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rat as an experimental model of Parkinson's disease. Among them, (S)-isopropyl 2-(2-amino-2-methylpropanamido)-3-(3,4-dihydroxyphenyl)propanoate (4 g) was found to be the most active compound, with 106% AUC activity and 149% peak activity of L-dopa after oral administration.

Molecular mechanism underlying the cerebral effect of Gly-Pro-Glu tripeptide bound to L-dopa in a Parkinson's animal model.

Oxidative stress is a critical contributing factor to neurodegenerative disorders. Therefore, the inhibition of ROS formation, responsible for chronic detrimental neuroinflammation, is an important strategy for preventing the neurodegenerative disease and for neuroprotective therapy. Gly-Pro-Glu (GPE) is the N-terminal tripeptide of insulin-like growth factor-I, which is naturally cleaved in the plasma and brain tissues. GPE has neuroprotective effects since it crosses the blood-CSF and the functional CSF-brain barriers and binds to glial cells. It has been shown that GPE improves motor behaviour in rats after 6-OHDA lesion, although it does not rescue dopaminergic neurons. Thus, we hypothesized that the GPE therapeutic efficacy in a Parkinson model might be improved by combining GPE to L: -dopa. Here, we used an animal model that represents a progressive chronic Parkinson's disease (PD) model, characterized by high levels of oxidative stress and inflammation. We showed that the co-drug, in which L: -dopa is covalently linked to the GPE tripeptide, by down-regulating the expression of inflammatory genes, decreases the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced inflammatory response and, by up-regulating tyrosine hydroxylase, reduces MPTP-induced neurotoxicity. Furthermore, by determining the nuclear translocation/activation of Nrf2 and NF-κB, we showed that systemic administration of the co-drug activates Nrf2-induced antioxidant response while suppressing NF-κB inflammatory pathway. Data suggest that the binding of L: -dopa to GPE tripeptide might represent a promising strategy to supply L: -dopa to parkinsonian patients.

Impact of COVID-19 pandemic on acute heart failure admissions and mortality: a multicentre study (COV-HF-SIRIO 6 study).

AIMS: The coronavirus disease-2019 (COVID-19) pandemic has changed the landscape of medical care delivery worldwide. We aimed to assess the influence of COVID-19 pandemic on hospital admissions and in-hospital mortality rate in patients with acute heart failure (AHF) in a retrospective, multicentre study. METHODS AND RESULTS: From 1 January 2019 to 31 December 2020, a total of 101 433 patients were hospitalized in 24 Cardiology Departments in Poland. The number of patients admitted due to AHF decreased by 23.4% from 9853 in 2019 to 7546 in 2020 (P < 0.001). We noted a significant reduction of self-referrals in the times of COVID-19 pandemic accounting 27.8% (P < 0.001), with increased number of AHF patients brought by an ambulance by 15.9% (P < 0.001). The length of hospital stay was overall similar (7.7 ± 2.8 vs. 8.2 ± 3.7 days; P = not significant). The in-hospital all-cause mortality in AHF patients was 444 (5.2%) in 2019 vs. 406 (6.5%) in 2020 (P < 0.001). A total number of AHF patients with concomitant COVID-19 was 239 (3.2% of AHF patients hospitalized in 2020). The rate of in-hospital deaths in AHF patients with COVID-19 was extremely high accounting 31.4%, reaching up to 44.1% in the peak of the pandemic in November 2020. CONCLUSIONS: Our study indicates that the COVID-19 pandemic led to (i) reduced hospital admissions for AHF; (ii) decreased number of self-referred AHF patients and increased number of AHF patients brought by an ambulance; and (iii) increased in-hospital mortality for AHF with very high mortality rate for concomitant AHF and COVID-19.

Ion channel inhibition with amiodarone or verapamil in symptomatic hospitalized nonintensive-care COVID-19 patients: The ReCOVery-SIRIO randomized trial.

BACKGROUND: Ion channel inhibition may offer protection against coronavirus disease 2019 (COVID-19). Inflammation and reduced platelet count occur during COVID-19 but precise quantification of risk thresholds is unclear. The Recov ery-SIRIO study aimed to assess clinical effects of amiodarone and verapamil and to relate patient phenotypes to outcomes. METHODS: RECOVERY-SIRIO is a multicenter open-label 1:1:1 investigator-initiated randomized trial with blinded event adjudication. A sample of 804 symptomatic hospitalized nonintensive-care COVID-19 patients, follow-up for 28 days was initially planned. RESULTS: The trial was stopped when a total of 215 patients had been randomized to amiodarone (n = 71), verapamil (n = 72) or standard care alone (n = 72). At 15 days, the hazard ratio (hazard ratio [HR], 95% confidence interval [CI]) for clinical improvement was 0.77 (0.52-1.14) with amiodarone and 0.97 (0.81-1.17) with verapamil as compared to usual care. Clinically relevant associations were found between mortality or lack of clinical improvement and higher peak C-reactive protein (CRP) levels or nadir platelet count at 7, 10 and 15 days. Mortality rate increased by 73% every 5 mg/dL increment in peak CRP (HR 1.73, 95% CI 1.27-2.37) and was two-fold higher for every decrement of 100 units in nadir platelet count (HR 2.19, 95% CI 1.37-3.51). By cluster analysis, thresholds of 5 mg/dL for peak CRP and 187 × 103/mcL for nadir platelet count identified the phenogroup at greatest risk of dying. CONCLUSIONS: In this randomized trial, neither amiodarone nor verapamil were found to significantly accelerate short-term clinical improvement. Peak CRP and nadir platelet counts were associated with increased mortality both in isolation and by cluster analysis.

Daily motor performance after switching levodopa to melevodopa: an open-label on advanced Parkinson's disease with "delayed-on" and/or"wearing-off".

AIM: Aim of the present study was to evaluate the clinical efficacy, tolerability and quality-of-life measures to melevodopa in advanced Parkinson's disease (PD) with motor fluctuations (MFs). METHODS: A total of 37 patients with advanced PD and MFs participated in the study. Patients were switched from standard l-dopa/carbidopa to melevodopa and were treated for 10 weeks. RESULTS: Assessment of "On-Day" time demonstrated improvement to about 0.7 hour in the melevodopa treatment. The benefit was greater in patients with "delayed-on" (P=0.002) and especially in those with both "delayed-on" and "wearing-off" (P<0.001). Most patients showed a significant improvement in PDQ-39 total score (P=0.002) and PSI distress domain (P<0.001). Instead, not significant difference was observed in patients with only wearing-off. CONCLUSION: These data show that melevodopa is an effective agent for improving daily motor performance and quality-of-life in PD with "delayed-on", also in association with "wearing-off".

Impact of an Augmented Reality Navigation System (SIRIO) on Bone Percutaneous Procedures: A Comparative Analysis with Standard CT-Guided Technique.

(1) Background: The purpose of this study is to evaluate the impact of an augmented reality navigation system (SIRIO) for percutaneous biopsies and ablative treatments on bone lesions, compared to a standard CT-guided technique. (2) Methods: Bioptic and ablative procedures on bone lesions were retrospectively analyzed. All procedures were divided into SIRIO and Non-SIRIO groups and in <2 cm and >2 cm groups. Number of CT-scans, procedural time and patient's radiation dose were reported for each group. Diagnostic accuracy was obtained for bioptic procedures. (3) Results: One-hundred-ninety-three procedures were evaluated: 142 biopsies and 51 ablations. Seventy-four biopsy procedures were performed using SIRIO and 68 under standard CT-guidance; 27 ablative procedures were performed using SIRIO and 24 under standard CT-guidance. A statistically significant reduction in the number of CT-scans, procedural time and radiation dose was observed for percutaneous procedures performed using SIRIO, in both <2 cm and >2 cm groups. The greatest difference in all variables examined was found for procedures performed on lesions <2 cm. Higher diagnostic accuracy was found for all SIRIO-assisted biopsies. No major or minor complications occurred in any procedures. (4) Conclusions: The use of SIRIO significantly reduces the number of CT-scans, procedural time and patient's radiation dose in CT-guided percutaneous bone procedures, particularly for lesions <2 cm. An improvement in diagnostic accuracy was also achieved in SIRIO-assisted biopsies.

Ocular Penetrance and Safety of the Dopaminergic Prodrug Etilevodopa.

Purpose: Animal models have demonstrated the role of dopamine in regulating axial elongation, the critical feature of myopia. Because frequent delivery of dopaminergic agents via peribulbar, intravitreal, or intraperitoneal injections is not clinically viable, we sought to evaluate ocular penetration and safety of the topically applied dopaminergic prodrug etilevodopa. Methods: The ocular penetration of dopamine and dopaminergic prodrugs (levodopa and etilevodopa) were quantified using an enzyme-linked immunosorbent assay in enucleated porcine eyes after a single topical administration. The pharmacokinetic profile of the etilevodopa was then assessed in rats. A four-week once-daily application of etilevodopa as a topical eye drop was conducted to establish its safety profile. Results: At 24 hours, the studied prodrugs showed increased dopaminergic derivatives in the vitreous of porcine eyes. Dopamine 0.5% (P = 0.0123) and etilevodopa 10% (p = 0.370) achieved significant vitreous concentrations. Etilevodopa 10% was able to enter the posterior segment of the eye after topical administration in rats with an intravitreal half-life of eight hours after single topical administration. Monthly application of topical etilevodopa showed no alterations in retinal ocular coherence tomography, electroretinography, caspase staining, or TUNEL staining. Conclusions: At similar concentrations, no difference in ocular penetration of levodopa and etilevodopa was observed. However, etilevodopa was highly soluble and able to be applied at higher topical concentrations. Dopamine exhibited both high solubility and enhanced penetration into the vitreous as compared to other dopaminergic prodrugs. Translational Relevance: These findings indicate the potential of topical etilevodopa and dopamine for further study as a therapeutic treatment for myopia.

ANalgesic Efficacy and safety of MOrphiNe versus methoxyflurane in patients with acute myocardial infarction: the rationale and design of the ANEMON-SIRIO 3 study: a multicentre, open-label, phase II, randomised clinical trial.

INTRODUCTION: The unfavourable influence of morphine on the pharmacokinetics of ticagrelor resulting in weaker and retarded antiplatelet effect in patients with acute coronary syndrome (ACS) has been previously shown. Replacing morphine with methoxyflurane, a potent, non-opioid analgesic agent, that does not weaken or delay the effect of antiplatelet agents may improve the clinical efficacy of treatment of patients with ACS. METHODS: The ANEMON-SIRIO 3 study was designed as a multicentre, open-label, phase II, randomised clinical trial aimed to test the analgesic efficacy and safety of methoxyflurane in patients with ACS. The study population will comprise patients with ST-elevation myocardial infarction or non-ST-elevation ACS admitted to the study centres with typical chest pain requiring analgesic treatment. Before percutaneous coronary intervention (PCI) for the patients with index ACS will be randomly assigned in 1:1 ratio to receive methoxyflurane administered by inhalation, or to obtain morphine administered intravenously. Analgesic treatment will be followed by 300 mg loading dose of aspirin and 180 mg loading dose of ticagrelor. Patients will be assessed with regard to pain intensity according to the Numeric Pain Rating Scale at baseline, 3 min after study drug administration and immediately after PCI. Moreover, patients will be actively monitored with regard to the occurrence of side effects of evaluated therapies, as well as adverse events that may be related to insufficient platelet inhibition (no-reflow phenomenon assessed immediately after PCI, administration of GPIIb/IIIa inhibitors during PCI, acute stent thrombosis). ETHICS AND DISSEMINATION: The study will be conducted in six Polish clinical centres from the beginning of in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. TRIAL REGISTRATION DETAILS: ClinicalTrials.gov, NCT04476173.

Pharmacological analysis demonstrates dramatic alteration of D1 dopamine receptor neuronal distribution in the rat analog of L-DOPA-induced dyskinesia.

We have associated behavioral, pharmacological, and quantitative immunohistochemical study in a rat analog of l-DOPA-induced dyskinesia to understand whether alterations in dopamine receptor fate in striatal neurons may be involved in mechanisms leading to movement abnormalities. Detailed analysis at the ultrastructural level demonstrates specific alterations of dopamine D(1) receptor (D(1)R) subcellular localization in striatal medium spiny neurons in l-DOPA-treated 6-hydroxydopamine-lesioned rats with abnormal involuntary movements (AIMs). This includes exaggerated D(1)R expression at the plasma membrane. However, D(1)R retains ability of internalization, as a challenge with the potent D(1)R agonist SKF-82958 induces a strong decrease of labeling at membrane in animals with AIMs. Since a functional cross talk between D(1)R and D(3)R has been suggested, we hypothesized that their coactivation by dopamine derived from l-DOPA might anchor D(1)R at the membrane. Accordingly, cotreatment with l-DOPA and the D(3)R antagonist ST 198 restores normal level of membrane-bound D(1)R. Together, these results demonstrate that AIMs are related to abnormal D(1)R localization at the membrane and intraneuronal trafficking dysregulation, and suggest that strategies aiming at disrupting the D(1)R-D(3)R cross talk might reduce l-DOPA-induced dyskinesia by reducing D(1)R availability at the membrane.

Melevodopa/carbidopa effervescent formulation in the treatment of motor fluctuations in advanced Parkinson's disease.

Melevodopa hydrochloride plus carbidopa in effervescent tablets (M/C) is a readily soluble antiparkinsonian tablet formulation. A total of 221 patients with Parkinson's disease and motor fluctuations entered a randomized, double-blind, double-dummy, controlled parallel group study, which compared the effectiveness of oral M/C effervescent tablets with standard oral formulation levodopa/carbidopa tablets (L/C; Sinemet) in reducing total daily OFF time. The difference of total daily OFF time (intention-to-treat population) between the two groups was not statistically significant (P = 0.07): -39.4 minutes (95%CI: -67.08 to -11.73) in M/C group vs. +3.5 minutes (95%CI: -36.19 to +43.26) in the L/C group. In the intragroup analysis, M/C significantly reduced the baseline daily OFF, which remained unchanged in the L/C group. There were no unexpected adverse events in either treatment arms, and discontinuation rates due to adverse events did not differ between the two groups [M/C: 2 patients (1.3%); L/C: 1 patient (1.4%)]. This study failed to meet the primary endpoint (P = 0.07); however, there was a trend in favour of the M/C preparation, which deserves further attention.

L-Dopa methyl ester: prolongation of survival of neuroblastoma-bearing mice after treatment.

L-Dopa has has been shown to demonstrate enhanced toxicity toward melanoma cells in vitro. Since melanocytes arise from the neural crest embryologically, the effect of L-dopa methyl ester, a soluble analog, on the murine C1300 neuroblastoma was studied. There was significant antitumor activity against the neuroblastoma, which was enhanced by combination with a dopa decarboxylase inhibitor, Ro4-4602. In vitro studies suggested inhibition of DNA synthesis as the principal site of action. A mechanism involving sulfhydryl compound scavenging is postulated.

Presynaptic dopamine function measured with [18F]fluorodopa and L-DOPA effects on impulsive choice.

We previously reported that L-DOPA effects on reward-based decision-making in a randomized, placebo-controlled, double-blind, crossover study were consistent with an inverted U-shaped function whereby both low and high extremes of dopamine signaling are associated with high-impulsive choice. To test this hypothesis, we performed [18F]DOPA positron emission tomography in 60 of the 87 participants in that study, and measured the effective distribution volume ratio (EDVR) of [18F]DOPA influx rate to [18F]dopamine washout rate, an index of presynaptic dopaminergic function. Participants with higher baseline EDVR self-reported lower impulsivity, and discounted rewards as a function of delay more strongly after receiving L-DOPA, whereas the opposite was detected for those with lower baseline EDVR. Our findings support a relationship of striatal dopaminergic activity to trait impulsivity, and the view that there is a non-linear, possibly inverted U-shaped relationship of striatal dopaminergic function with delay discounting. Individuals with optimal dopamine signaling would become more impulsive when receiving dopamine-enhancing drugs, whereas those with suboptimal dopaminergic signaling would benefit and exhibit less impulsive choice. Consideration of differences in endogenous dopamine signaling and possibly also other neurotransmitter activity may be crucial to advance understanding of the neurobiochemical mechanisms of impulsive decision-making and related mental disorders.