Should continuous dopaminergic stimulation be a standard of care in advanced Parkinson's disease?

The standard of care is a term that refers to the level of care, skill, and treatment that a healthcare provider should offer to a patient based on the current scientific evidence and the level of medical knowledge available in the field. For Parkinson's disease (PD), the standard care is mostly considered to be oral treatment with dopaminergic drugs, particularly levodopa which remains the 'gold standard'. However, effective management with levodopa during the later stages of the disease becomes increasingly challenging due to the ongoing neurodegenerative process, the consequences of its pulsatile dopaminergic stimulation, and the gastrointestinal barriers to effective drug absorption. As a result, the concept of applying continuous dopaminergic stimulation has emerged with infusion therapies (continuous subcutaneous apomorphine, levodopa-carbidopa intestinal gel, and levodopa-entacapone-carbidopa intestinal gel infusion). These therapies seek to provide continuous stimulation of striatal dopamine receptors that is efficient not only in alleviating clinical symptoms, but also in delaying, reducing, and possibly preventing the onset of levodopa-related motor (fluctuations, dyskinesia) and non-motor complications; and they are also associated with clinically relevant side effects. Clinical studies and real-life experience support the notion that infusion therapies should be accepted as part of the standard of care for patients with advanced PD who have refractory, severe, and disabling motor complications that affect their quality of life. However, they should be considered based on the needs of individualized patients and the access to these advanced therapies needs to be made more accessible to the general PD population.

Why do 'OFF' periods still occur during continuous drug delivery in Parkinson's disease?

Continuous drug delivery (CDD) is used in moderately advanced and late-stage Parkinson’s disease (PD) to control motor and non-motor fluctuations (‘OFF’ periods). Transdermal rotigotine is indicated for early fluctuations, while subcutaneous apomorphine infusion and levodopa-carbidopa intestinal gel are utilised in advanced PD. All three strategies are considered examples of continuous dopaminergic stimulation achieved through CDD. A central premise of the CDD is to achieve stable control of the parkinsonian motor and non-motor states and avoid emergence of ‘OFF’ periods. However, data suggest that despite their efficacy in reducing the number and duration of ‘OFF’ periods, these strategies still do not prevent ‘OFF’ periods in the middle to late stages of PD, thus contradicting the widely held concepts of continuous drug delivery and continuous dopaminergic stimulation. Why these emergent ‘OFF’ periods still occur is unknown. In this review, we analyse the potential reasons for their persistence. The contribution of drug- and device-related involvement, and the problems related to site-specific drug delivery are analysed. We propose that changes in dopaminergic and non-dopaminergic mechanisms in the basal ganglia might render these persistent ‘OFF’ periods unresponsive to dopaminergic therapy delivered via CDD.

Use of levodopa-carbidopa intestinal gel to treat patients with multiple system atrophy

BACKGROUND

Levodopa-carbidopa intestinal gel (LCIG) is an effective treatment for late-stage Parkinson's disease (PD) but had not been evaluated in levodopa-responsive patients with the parkinsonian variant of multiple system atrophy (MSA-P) and motor fluctuations. We aimed to assess the safety of LCIG in MSA-P patients.

METHODS

In a retrospective, single-center study, we analyzed clinical and treatment-related data for all patients with MSA-P or PD treated with LCIG between December 2004 and November 2017. Adverse events (AEs) were classified into three classes: AEs related to gastrointestinal effects or to the PEG-J procedure, AEs related to the device, and AEs related to the pharmacological effect of LCIG.

RESULTS

7 MSA-P and 63 PD patients had been treated with LCIG for a median [interquartile range] period of 31 [16;43] and 19 [8;45] months, respectively. There were no significant intergroup differences in safety. Enteral nutrition was introduced at the same time as LCIG treatment in 4 (57%) MSA-P patients. In the MSA-P and PD groups, LCIG was associated with a better Global Clinical Impression score and discontinuation of oral anti-parkinsonian drugs (in 43% and 27% of cases, respectively).

CONCLUSIONS

LCIG treatment is feasible in MSA-P patients with severe motor complications. The safety profile is similar to that seen in PD.

Continuous dopaminergic stimulation counteracts L-DOPA-induced overactivity of Ca2+ in 6-OHDA-lesioned rats

In the clinical treatment of Parkinson's disease (PD), the emergence of L-DOPA-induced dyskinesia (LID) and other motor symptoms remains a restrictive factor for the use of levodopa (L-DOPA). Our objective was to test the effect of continuous dopaminergic stimulation (CDS) on LID and the mechanism of its effect on the calcium (Ca²⁺) signaling pathway. 6-OHDA (6-hydroxydopamine)-treated rats were administered 1% CMC-Na, L-DOPA, rotigotine behenate (RGTB), and L-DOPA + RGTB, respectively, for 28 days. During the treatment, the abnormal involuntary movement (AIM) scores were conducted on days 1, 5, 10, 14, 19, 23 and 28 after the first dose. Subsequently, the number of tyrosine hydroxylase (TH)-positive neurons was detected by immunohistochemistry. Additionally, the changes in Ca²⁺ were detected using a laser confocal technique, and the related proteins, such as neuronal NOS (nNOS), BAX, BCL2, CaMKII, P-CaMKII, and PSD-95, were measured by Western blot. Transmission electron microscopy (TEM) was used to investigate the changes in synaptic structure. The data showed that CDS reduced the AIM scores, increased the expression of TH in the substantia nigra (SN), decreased the expression of nNOS and BAX/BCL2ratio in the striatum, reduced the Ca²⁺ influx induced by L-DOPA and inhibited the Ca²⁺ signaling pathways of dopamine neurons in the striatum. Moreover, the overactivity of synapses induced by L-DOPA was inhibited by CDS. These data further support the hypothesis that continuous delivery of a dopamine agonist reduces the risk of LID induction. Moreover, RGTB could be a promising treatment for PD by simulating CDS.

Current Practices for Outpatient Initiation of Levodopa-Carbidopa Intestinal Gel for Management of Advanced Parkinson's Disease in the United States

In 2015, the US Food and Drug Administration approved levodopa-carbidopa intestinal gel (LCIG; also known as carbidopa-levodopa enteral suspension in the US) for the treatment of motor fluctuations in patients with advanced Parkinson's disease. LCIG provides a continuous infusion of levodopa and carbidopa by means of a portable pump and percutaneous endoscopic gastrojejunostomy tube. The delivery system has a two-fold pharmacokinetic advantage over orally administered carbidopa/levodopa. First, levodopa is delivered in a continuous rather than intermittent, pulsatile fashion. Second, delivery to levodopa's site of absorption in the jejunum bypasses the stomach, thereby avoiding issues with erratic gastric emptying. In blinded prospective clinical trials and observational studies, LCIG has been shown to significantly decrease "off" time, increase "on" time without troublesome dyskinesia, and reduce dyskinesia. Consistent with procedures in previous studies, LCIG initiation and titration in the pivotal US clinical trial were performed in the inpatient setting and followed a standardized protocol. In clinical practice, however, initiation and titration of LCIG have a great degree of flexibility and, in the US, almost always take place in the outpatient setting. Nonetheless, there remains a significant amount of clinician uncertainty regarding titration in outpatient clinical practice. This review aims to shed light on and provide guidance as to the current methods of titration in the outpatient setting, as informed by the medical literature and the authors' experiences. FUNDING: AbbVie, Inc. Plain language summary available for this article.

Preparation and evaluation of rotigotine-loaded implant for the treatment of Parkinson's disease and its evolution study

Purpose

To develop rotigotine-loaded implants (RI) to achieve continuous release of rotigotine for long duration for the treatment of Parkinson’s disease (PD).

Methods

RI was prepared by hot-melt extrusion method using poly (lactide-co-glycolide) (PLGA) as the matrix. In vitro drug release was optimized by drug loading, melting temperature during preparing process and additives. The surface and internal morphology of RI was imaged by SEM. The in vivo release profile of RI was investigated on rat.

Results

RI prepared with PLGA 7525 5A showed sustained release of 40 days while suffering a lag phase, which was significantly shortened by blending 5050 2A and mannitol in the matrix. RI prepared by 7525 5A/5050 2A/mannitol = 55:10:5 (rotigotine 30%) showed a 40-day sustained release in vivo with no lag phase. The drug release from RI was also affected by drug loading and melting temperature probably due to the drug state existed in the implant. The evolution of implants during release process was correlated well with the drug release kinetics.

Conclusion

RI could achieve sustained drug release for 40 days which could supply an alternative of continuous dopaminergic stimulation (CDS) for the treatment of PD.

Protection of MPTP-induced neuroinflammation and neurodegeneration by rotigotine-loaded microspheres

AIMS

The aim of the study is to evaluate the neuroprotective effects of continuous dopaminergic stimulation (CDS) by rotigotine-loaded microspheres (RoMS) in a mouse model of MPTP-induced Parkinson's disease (PD) and to elucidate the potential mechanism underlying these effects.

MAIN METHODS

Male C57BL/6 mice were treated either intramuscularly once with RoMS or twice daily for two weeks with rotigotine, and from the 9th day, MPTP (30 mg/kg, i.p.) was injected for the last 5 days. Following treatment, Parkinsonism scores were calculated and oxidative stress-related indicators in the striatum were performed. Neuroinflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) were detected in the striatum. Expression of apoptosis-related proteins B-cell leukemia/lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (BAX) was measured in the striatum by Western blot. Nigral tyrosine hydroxylase (TH)-positive neurons and microglial cell markers, i.e., ionized calcium binding adaptor molecule-1 (Iba-1) and neuronal synaptosomes, were quantified to assess the neuroprotective efficacy of RoMS.

KEY FINDINGS

The administration of rotigotine significantly improved the Parkinsonism score, protected dopaminergic neurons with antioxidants, reduced microglial cell activation and the release of neuroinflammatory cytokines, and balanced the expression of Bcl-2 and Bax in MPTP-treated mice. Interestingly, the neuroprotective properties of rotigotine were remarkably amplified by CDS treatment with RoMS.

SIGNIFICANCE

These results suggest that CDS therapy can play a neuroprotective role in an MPTP mouse model. Neuroprotective disease-modifying therapy may have the potential benefits of early treatment by normalizing compensatory mechanisms and may also help to delay dyskinesia in the later stages of PD.