Laura Serafina Cerasa

New drug delivery strategies for improved Parkinson's disease therapy

Increasing interest has been addressed toward the introduction of new therapeutic approaches to obtaining continuous dopaminergic stimulation (CDS). The goal of this therapeutic strategy is to reduce the occurrence and severity of L-DOPA (LD)-associated motor fluctuations and dyskinesia, and provide good long-term safety and tolerability. CDS can be achieved by the administration of oral dopamine (DA) agonists with a long half-life, transdermal or subcutaneous delivery of DA agonists, or intestinal LD infusion. To allow higher concentrations of LD to reach the brain and to reduce peripheral side effects, the therapeutic approach provides the concomitant administration of LD, carbidopa and entacapone that have been developed in tablet form, standard LD/carbidopa, LD/benserazide, LD/entacapone, LD/tolcapone associations or long-acting controlled release formulations, LD/carbidopa and LD/benserazide. Alternatively to solid formulations, LD/carbidopa liquid forms have been developed. Furthermore, the authors examine a series of new LD codrugs and non-dopaminergic drugs for Parkinsons disease treatment, together with a variety of experimental delivery strategies including transdermal therapeutic systems, liposomes, solid lipid nanoparticles and biocompatible microparticles. This review provides an overview of progress in anti-Parkinson therapy, mainly focused on delivery strategies and codrug approach for treatment of this neurological disorder.

Codrugs linking L-dopa and sulfur-containing antioxidants: new pharmacological tools against Parkinson's disease.

A series of multifunctional codrugs (1-6) were synthesized to overcome the pro-oxidant effect associated with L-dopa (LD) therapy. Target compounds release LD and dopamine (DA) in human plasma after enzymatic hydrolysis, displaying an antioxidant effect superior to that of N-acetylcysteine (NAC). After intracerebroventricular injection of codrug 4, the levels of DA in the striatum were higher than those in LD-treated groups, indicating that this compound has a longer half-life in brain than LD.

New L‐Dopa Codrugs as Potential Antiparkinson Agents

This paper reports the synthesis and preliminary evaluation of new L‐dopa (LD) conjugates (1 and 2) obtained by joining LD with two different natural antioxidants, caffeic acid and carnosine, respectively. The antioxidant efficacy of compounds 1 and 2 was assessed by evaluating plasmatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) in the rat. Rat striatal concentration of LD and dopamine (DA), and central nervous effects were evaluated after oral administration of the codrugs 1 and 2. The results suggest that, though our codrugs are devoid of significant antioxidant activity, they are able to induce sustained delivery of DA in rat striatum and can improve LD and DA release in the brain.

(R)‐α‐Lipoyl‐Glycyl‐L‐Prolyl‐L‐Glutamyl Dimethyl Ester Codrug as a Multifunctional Agent with Potential Neuroprotective Activities

The (R)‐α‐lipoyl‐glycyl‐L‐prolyl‐L‐glutamyl dimethyl ester codrug (LA‐GPE, 1) was synthesized as a new multifunctional drug candidate with antioxidant and neuroprotective properties for the treatment of neurodegenerative diseases. Physicochemical properties, chemical and enzymatic stabilities were evaluated, along with the capacity of LA‐GPE to penetrate the blood–brain barrier (BBB) according to an in vitro parallel artificial membrane permeability assay for the BBB. We also investigated the potential effectiveness of LA‐GPE against the cytotoxicity induced by 6‐hydroxydopamine (6‐OHDA) and H2O2 on the human neuroblastoma cell line SH‐SY5Y by using the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) reduction assay. Our results show that codrug 1 is stable at both pH 1.3 and 7.4, exhibits good lipophilicity (log P=1.51) and a pH‐dependent permeability profile. Furthermore, LA‐GPE was demonstrated to be significantly neuroprotective and to act as an antioxidant against H2O2‐ and 6‐OHDA‐induced neurotoxicity in SH‐SY5Y cells.

Synthesis of a novel cyclic prodrug of S-allyl-glutathione able to attenuate LPS-induced ROS production through the inhibition of MAPK pathways in U937 cells.

A novel cyclic prodrug of S-allyl-glutathione (CP11), obtained by using an acyloxy-alkoxy linker, was estimated for its pharmacokinetic and biological properties. The stability of CP11 was evaluated at pH 1.2, 7.4, in simulated fluids with different concentrations of enzymes, and in human plasma. The anti-inflammatory ability of CP11 was assessed in U937 cells, an immortalized human monocyte cell line. Results showed that CP11 is stable at acidic pH showing a possible advantage for oral delivery due to the longer permanence in the stomach. Having a permeability coefficient of 2.49 × 10(-6) cm s(-1), it was classified as discrete BBB-permeable compound. Biological studies revealed that CP11 is able to modulate inflammation mediated by LPS in U937 cells preventing the increase of ROS intracellular levels through interaction with the MAPK pathway.

L-Dopa Prodrugs: An Overview of Trends for Improving Parkinsons Disease Treatment

L-Dopa is the mainstay of Parkinsons disease therapy; this drug is usually administered orally, but it is extensively metabolized in the gastrointestinal tract, so that relatively little arrives in the bloodstream as intact L-Dopa. The peripheral conversion of L-Dopa by amino acid decarboxylase to dopamine is responsible for the typical gastrointestinal and cardiovascular side effects. To minimize the conversion to dopamine outside the central nervous system, L-Dopa is usually given in combination with peripheral inhibitors of amino acid decarboxylase. 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 are the drugs physical-chemical properties: low water and lipid solubility, resulting in unfavorable partition, and the high susceptibility to chemical and enzymatic degradation. Starting from these considerations the prodrug approach has been applied to L-Dopa in order to overcome its metabolism problems and to improve its bioavailability. The goal of this paper is to provide the reader with a critical overview on L-Dopa prodrugs here classified according to the nature of the main chemical modification on L-Dopa backbone that led to the formation of the desired derivative.

Transdermal donepezil on the treatment of Alzheimer's disease

Alzheimer’s disease (AD) is the most common type of senile dementia, characterized by cognitive deficits related to degeneration of cholinergic neurons. The first anti-Alzheimer drugs approved by the Food and Drug Administration were the cholinesterase inhibitors (ChEIs), which are capable of improving cholinergic neurotransmission by inhibiting acetylcholinesterase. The most common ChEIs used to treat cognitive symptoms in mild to moderate AD are rivastigmine, galantamine, and donepezil. In particular, the lattermost drug has been widely used to treat AD patients worldwide because it is significantly less hepatotoxic and better tolerated than its predecessor, tetrahydroaminoacridine. It also demonstrates high selectivity towards acetylcholinesterase inhibition and has a long duration of action. The formulations available for donepezil are immediate release (5 or 10 mg), sustained release (23 mg), and orally disintegrating (5 or 10 mg) tablets, all of which are intended for oral-route administration. Since the oral donepezil therapy is associated with adverse events in the gastrointestinal system and in plasma fluctuations, an alternative route of administration, such as the transdermal one, has been recently attempted. The goal of this paper is to provide a critical overview of AD therapy with donepezil, focusing particularly on the advantages of the transdermal over the oral route of administration.

Ibuprofen and Lipoic Acid Diamide as Co-Drug with Neuroprotective Activity: Pharmacological Properties and Effects in β-Amyloid (1–40) Infused Alzheimer's Disease Rat Model

Both oxidative stress and inflammation are elevated in brains of Alzheimers disease patients, but their pathogenic significance still remains unclear. Current evidence support the hypothesis that non-steroidal anti-inflammatory drugs (NSAIDs) and antioxidant therapy might protect against the development of Alzheimers disease, and ibuprofen has the strongest epidemiological support. In the present work our attention was focused on (R)-α-lipoic acid considered as a potential neuroprotective agent in Alzheimers disease therapy. In particular, we investigated a new co-drug (1) obtained by joining (R)-α-lipoic acid and ibuprofen via a diamide bond, for evaluating its potential to antagonize the deleterious structural and cognitive effects of β-amyloid (1–40) in an infused Alzheimers disease rat model. Our results indicated that infusion of β-amyloid (1–40) impairs memory performance through a progressive cognitive deterioration; however, ibuprofen and co-drug 1 seemed to protect against behavioural detriment induced by simultaneous administration of β-amyloid (1–40) protein. The obtained data were supported by the histochemical findings of the present study: β-amyloid protein was less expressed in 1-treated than in ibuprofen and (R)-α-lipoic acid alone-treated cerebral cortex. Taken together, the present findings suggest that co-drug 1 treatment may protect against the cognitive dysfunction induced by intracerebroventricular infusion of β-amyloid (1–40) in rats. Thus, co-drug 1 could prove useful as a tool for controlling Alzheimers disease-induced cerebral amyloid deposits and behavioural deterioration.

Design, synthesis, and preliminary pharmacological evaluation of new imidazolinones as L-DOPA prodrugs.

L-DOPA, the immediate biological precursor of dopamine, is still considered the drug of choice in the treatment of Parkinsons disease. However, therapy with L-DOPA is associated with a number of acute problems. With the aim to increase the bioavailability after oral administration, we designed a multi-protected L-DOPA prodrugs able to release the drug by both spontaneous chemical or enzyme catalyzed hydrolysis. The new compounds have been synthesized and preliminarily evaluated for their water solubility, log P, chemical stability, and enzymatic stability. The results indicate that the incorporation of the amino acidic moiety of L-DOPA into an imidazoline-4-one ring provides prodrugs sufficiently stable to potentially cross unchanged the acidic environment of the stomach, and to be absorbed from the intestine. They also might be able to release L-DOPA in human plasma after enzymatic hydrolysis. The ability of prodrugs 6a-b to increase basal levels of striatal DA, and influence brain neurochemistry associated with dopaminergic activity following oral administration, as well as the radical-scavenging activity against DPPH for compounds 6a-b and 15a are also reported.

CNS delivery of l-dopa by a new hybrid glutathione–methionine peptidomimetic prodrug

Parkinson’s disease (PD) is a neurodegenerative disorder associated primarily with loss of dopamine (DA) neurons in the nigrostriatal system. With the aim of increasing the bioavailability of l-dopa (LD) after oral administration and of overcoming the pro-oxidant effect associated with LD therapy, we designed a peptidomimetic LD prodrug (1) able to release the active agent by enzyme catalyzed hydrolysis. The physicochemical properties, as well as the chemical and enzymatic stabilities of the new compound, were evaluated in order to check both its stability in aqueous medium and its sensitivity towards enzymatic cleavage, providing the parent LD drug, in rat and human plasma. The radical scavenging activities of prodrug 1 was tested by using both the DPPH–HPLC and the DMSO competition methods. The results indicate that the replacement of cysteine GSH portion by methionine confers resistance to oxidative degradation in gastric fluid. Prodrug 1 demonstrated to induce sustained delivery of DA in rat striatal tissue with respect to equimolar LD dosages. These results are of significance for prospective therapeutic application of prodrug 1 in pathological events associated with free radical damage and decreasing DA concentration in the brain.