Pharmacokinetics of Inhaled Levodopa Administered With Oral Carbidopa in the Fed State in Patients With Parkinson's Disease

Clinical Use of On-Demand Therapies for Patients with Parkinson's Disease and OFF Periods

On-demand therapies for Parkinson's disease (PD) provide rapid, reliable relief for patients experiencing OFF periods; however, practical guidelines on the use of these therapies are not generally available. This paper reviews the use of on-demand treatments. Motor fluctuations occur in nearly all patients with PD after long-term use of levodopa. As the goal of PD treatment is to provide good ON time, on-demand treatments that have a more rapid reliable onset than the slower-acting oral medications provide rapid relief for OFF periods. All current on-demand treatments bypass the gastrointestinal tract, providing dopaminergic therapy directly into the blood stream by subcutaneous injection, through the buccal mucosa, or by inhalation into the pulmonary circulation. On-demand treatments are fast acting (10- to 20-min onset), with maximum, reliable, and significant responses reached within 30 min after administration. Oral medications pass through the gastrointestinal tract and thus have slower absorption owing to gastroparesis and competition with food. On-demand therapies, by providing fast-acting relief, can have a positive impact on a patient's quality of life when patients are experiencing OFF periods.

Inhaled levodopa for threatening impending OFF episodes in managing Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder that leads to the degeneration of dopaminergic neurons resulting in a widespread pathology of motor and non-motor symptoms. Oral levodopa remains the most effective symptomatic treatment of PD, but motor complications such as Off episodes occur over time. The spectrum of manifestation of OFF episodes varies, e.g., early morning akinesia, end-of-dose wearing OFF, delayed ON, suboptimal ON and dose failure. The functional disability substantially impacts the quality of life for PD patients. An innovative on-demand therapy to treat Off episodes was approved for patients receiving oral levodopa/dopa deacarboxylase inhibitor: inhaled levodopa powder (Inbrija®). The pulmonary delivery of inhaled levodopa powder provides a predictable and fast treatment effect, independent of gastrointestinal dysfunctions or food intake, which could affect levodopa absorption. Levodopa is administered with a breath-actuated inhaler device and the approved dose is 84 mg per Off episode. During the pivotal SPAN-PD phase III trial, significant improvement in Unified Parkinson Disease Rating Scale III score was measured 30 min post-dose at week 12. Improvement was already seen for the first measured time point 10 min post-dose. No differences in pulmonary function was observed when using inhaled levodopa powder regularly for up to 12 months. Inhaled levodopa powder was also approved for early morning Off episodes. The aim of this review article is to give an overview of the different clinical studies of the innovative inhaled levodopa powder, a new on-demand therapy to treat Off episodes in PD.

Drugs to the Rescue: Comparison of On-Demand Therapies for OFF Symptoms in Parkinson's Disease

Patients with Parkinson's disease often suffer from OFF symptoms disrupting their daily routines and adding to disabilities. Despite polypharmacy and adjustments to medication schedules, they often do not experience consistent relief from their motor symptoms. As the disease progresses, impaired gastric emptying may evolve, making it even more challenging for dopaminergic drugs to provide consistent results. This review focuses on a group of drugs that have the pharmacokinetic advantage of a much earlier onset of action by virtue of their non-oral routes of absorption. We compare the current marketed options: subcutaneous apomorphine, sublingual apomorphine, and inhaled levodopa. Subcutaneous apomorphine is the speediest to take effect, whereas sublingual apomorphine offers the longest clinical effect. Inhaled levodopa has the most favorable side effect profile among the three options. An inhaled form of apomorphine is currently under development, having passed safety and efficacy studies. Each of these drugs has unique characteristics for the user, including different side effect profiles and onset of action. The best choice for a patient will depend on individual needs and circumstances. In this review, we explore those nuances to allow clinicians to select the best option for their patients.

The Clinical Development of Levodopa Inhalation Powder

ABSTRACT

Oral levodopa is the most effective treatment for Parkinson disease, but OFF periods emerge over time. Gastrointestinal dysfunction and food effects impact levodopa absorption, contributing to unpredictable control of OFF periods. Inhaled levodopa powder (Inbrija) is approved for on-demand treatment of OFF periods in patients receiving oral levodopa-dopa decarboxylase inhibitors. The 84-mg dose is administered via a breath-actuated inhaler. It provides pulmonary delivery of levodopa to the systemic circulation and is taken when a patient has an OFF period in between doses of regular oral levodopa medication. The pivotal SPAN-PD trial in patients experiencing OFF periods on oral dopaminergic therapy showed that levodopa inhalation powder 84 mg produced significant improvement in Unified Parkinson Disease Rating Scale Part III score, as measured 30 minutes postdose at week 12, and improvement was seen as early as 10 minutes. More patients in the levodopa inhalation powder group turned ON within 60 minutes of treatment and remained ON at 60 minutes than in the placebo group. Levodopa inhalation powder can also be used to treat early-morning OFF periods and, when used for up to 12 months, produced no clinically significant differences in pulmonary function compared with an untreated cohort. Levodopa inhalation powder 84 mg increased plasma levodopa concentration rapidly and with less variability than oral levodopa/carbidopa (25/100 mg). Most common adverse event associated with levodopa inhalation powder is cough, found in ~15% of patients in the SPAN-PD trial; otherwise, reported adverse events were consistent with those known to be associated with oral levodopa.

The microbiome-gut-brain axis in Parkinson disease - from basic research to the clinic

Evidence for a close bidirectional link between the brain and the gut has led to a paradigm shift in neurology, especially in the case of Parkinson disease (PD), in which gastrointestinal dysfunction is a prominent feature. Over the past decade, numerous high-quality preclinical and clinical publications have shed light on the highly complex relationship between the gut and the brain in PD, providing potential for the development of new biomarkers and therapeutics. With the advent of high-throughput sequencing, the role of the gut microbiome has been specifically highlighted. Here, we provide a critical review of the literature on the microbiome-gut-brain axis in PD and present perspectives that will be useful for clinical practice. We begin with an overview of the gut-brain axis in PD, including the potential roles and interrelationships of the vagus nerve, α-synuclein in the enteric nervous system, altered intestinal permeability and inflammation, and gut microbes and their metabolic activities. The sections that follow synthesize the proposed roles of gut-related factors in the development and progression of, in responses to PD treatment, and as therapeutic targets. Finally, we summarize current knowledge gaps and challenges and delineate future directions for the field.

Recent advances in drug delivery to the central nervous system by inhalation

INTRODUCTION

Drugs need to enter the systemic circulation efficiently before they can cross the blood-brain barrier and reach the central nervous system. Although the respiratory tract is not a common route of administration for delivering drugs to the central nervous system, it has attracted increasing interest in recent years for this purpose.

AREAS COVERED

In this article, we compare pulmonary delivery to three other common routes (parenteral, oral, and intranasal) for delivering drugs to the central nervous system, followed by summarising the devices used to aerosolise neurological drugs. Recent studies delivering drugs for different neurological disorders via inhalation are then discussed to illustrate the strengths of pulmonary delivery.

EXPERT OPINION

Recent studies provide strong evidence and rationale to support inhaling neurological drugs. Since inhalation can achieve improved pharmacokinetics and rapid onset of action for multiple drugs, it is a non-invasive and efficient method to deliver drugs to the central nervous system. Future research should focus on delivering other small and macro-molecules via the lungs for different neurological conditions.

Does Ethnicity Influence Recruitment into Clinical Trials of Parkinson's Disease?

BACKGROUND

Lack of participation of black and minority ethnic communities (BAME) in registered clinical trials is a concern as data emerging from these studies are used to licence new drugs or other interventions, even though findings made in such selected study populations have limited external validity in the aforesaid ethnic groups.

OBJECTIVE

We used Parkinson's disease (PD), the fastest rising neurodegenerative disorder in the world, as an exemplar condition to test our hypothesis that participants from BAME communities are underrepresented in clinical trials.

METHODS

A systematic search of clinical trials registered on a Clinicaltrials.gov database which queried for PD with racial distribution data from 2017 to 2021.

RESULTS

Out of 266 trials considered, 54 trials were published in peer reviewed journals. Among these, only 23 (42.65%) publications reported data regarding the racial distribution of the participants. Out of these, five studies involved mixed racial participation and two trials included black subjects.

CONCLUSION

We found that inclusion of under-represented BAME groups in recently published clinical trials is low, at only 21.57%, and is not even considered in most studies. Out of the reviewed trials, only 5 (21.75%) studies reported detailed demographic categories with black minorities enrolment. This constitutes a severe under-representation when compared to the proportion of Black or African American in the UK population (3%). Results of this study identified the need for better reporting of racial composition in clinical trials. We strongly recommend that future studies should consider ethnicity and other issues around diversity when designing and implementing the clinical trials, not only in the PD field but also beyond.

Safety and pharmacokinetics of multiple dosing with inhalable apomorphine (AZ-009), and its efficacy in a randomized crossover study in Parkinson's disease patients

INTRODUCTION

Apomorphine is used to treat OFF periods in Parkinson's disease (PD) patients. AZ-009 is a novel apomorphine formulation that delivers a thermally-generated aerosol to the deep lung via inhalation with a single breath.

METHODS

Part A was a randomized, placebo-controlled, double-blind study investigating the safety and pharmacokinetics of multiple ascending doses of AZ-009. PD patients (n = 24) received placebo or 2, 3 or 4 mg AZ-009 once daily for 5 days, followed by three times daily for 2 days with 2 h between doses. Part B was a double-blind crossover study in 8 PD patients who experience OFF periods. During an OFF state, patients received 4 mg AZ-009 and placebo on two consecutive days in a randomized order. MDS-UPDRS III and ON/OFF state were assessed pre- and post-dose.

RESULTS

Three times daily dosing with 2, 3 and 4 mg AZ-009 was relatively well tolerated with no apparent accumulation or changes in safety profile. Mild and transient throat irritation and cough were reported most often. AZ-009 was rapidly absorbed with median T_max between 1 and 2 min. When corrected for placebo response, the maximum effect of 4 mg AZ-009 based on MDS-UPDRS III scores was observed at 10 and 30 min post-dose with mean (SD) reductions of 6.8 (9.4) and 6.1 (9.1) points respectively. Whereas 0% of patients turned ON after placebo, 50% turned ON 10 min after 4 mg AZ-009 treatment.

CONCLUSION

AZ-009 is rapidly systemically absorbed and safe to dose three times daily. AZ-009 could provide a faster-acting and easier to use formulation than currently available therapies.

Inhaled Levodopa (CVT-301) for the Treatment of Parkinson Disease: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Purpose

of Review: To investigate the efficacy and safety of CVT-301 for motor fluctuation in Parkinson’s disease (PD).

Recent Findings:

This study demonstrated that the CVT-301 group had a higher proportion of patients achieving an ON state than the placebo group (OR=2.68; 95% CI: 1.86-3.86; p<0.00001). Moreover, CVT-301 had also shown to improve motor function by UPDRS-III score (SMD=3.83; 95% CI: 2.44-5.23; p<0.00001) and promote an overall improvement of PD by PGIC self-rating (OR=2.95; 95% CI: 1.78-4.9; p<0.00001). The most common adverse events encountered were respiratory symptoms (OR=12.18; 95% CI: 5.01-29.62; p<0.00001) and nausea (OR=3.95; 95% CI: 1.01-15.41; p=0.05).

Summary:

CVT-301 had the potential to be an alternative or even a preferred treatment for motor fluctuation in PD patients.

Optimizing Spray-Dried Porous Particles for High Dose Delivery with a Portable Dry Powder Inhaler

This manuscript critically reviews the design and delivery of spray-dried particles for the achievement of high total lung doses (TLD) with a portable dry powder inhaler. We introduce a new metric termed the product density, which is simply the TLD of a drug divided by the volume of the receptacle it is contained within. The product density is given by the product of three terms: the packing density (the mass of powder divided by the volume of the receptacle), the drug loading (the mass of drug divided by the mass of powder), and the aerosol performance (the TLD divided by the mass of drug). This manuscript discusses strategies for maximizing each of these terms. Spray drying at low drying rates with small amounts of a shell-forming excipient (low Peclet number) leads to the formation of higher density particles with high packing densities. This enables ultrahigh TLD (>100 mg of drug) to be achieved from a single receptacle. The emptying of powder from capsules is directly proportional to the mass of powder in the receptacle, requiring an inhaled volume of about 1 L for fill masses between 40 and 50 mg and up to 3.2 L for a fill mass of 150 mg.

A technology evaluation of CVT-301 (Inbrija): an inhalable therapy for treatment of Parkinson's disease

Introduction: The most widely used pharmacological treatment for Parkinson's disease is levodopa, the precursor for dopamine formation in the brain. Over time, the effectiveness of levodopa declines, and patients experience motor fluctuations, or OFF periods. A levodopa formulation administered via a capsule-based oral inhaler provides a new delivery mechanism for levodopa that provides rapid relief of OFF periods.Areas covered: CVT-301 is a dry powder formulation designed to supply levodopa to the systemic circulation via pulmonary absorption. The technology, pharmacokinetics, efficacy, and safety data of this formulation are presented.Expert opinion: Oral inhalation is a novel method of administration for levodopa that bypasses the gastrointestinal tract, allowing levodopa to enter the systemic circulation rapidly and more reliably than oral medications. Gastrointestinal dysfunction, a common feature of Parkinson's disease, can lead to impaired absorption of oral medications. Pulmonary delivery rapidly elevates levodopa plasma concentrations to provide relief of OFF periods for patients receiving oral levodopa.

On demand therapy for Parkinson's disease patients: Opportunities and choices

Levodopa is the most effective symptomatic treatment for Parkinson's disease (PD), but a major treatment challenge is that over time, many patients experience periods of return of PD symptoms intermittently through the day, known as OFF periods. OFF periods typically manifest as a return of motor symptoms but can also involve non-motor symptoms and these periods can disrupt good control despite optimization of the oral levodopa regimen. OFF periods emerge in large measure due to a shortening of the duration of clinical benefit from oral levodopa, thought to be related to a progressive loss of dopamine neurons and their ability to store and release levodopa-derived dopamine over many hours. The problem is further compounded by impaired absorption of oral levodopa due to gastroparesis and other factors limiting its uptake in the small intestine, including competition for uptake by meals and their protein content. On-demand therapies are now available for the treatment of OFF episodes in PD and are administered intermittently, on an as-needed basis, on top of the patient's maintenance medication regimen. To be useful, an on-demand medication should take effect more rapidly and reliably than oral levodopa. Options for on-demand therapy for OFF periods have recently increased with the approval of levodopa inhalation powder and sublingual apomorphine as alternatives to the older option of subcutaneous apomorphine injection, each of which avoids the gastrointestinal tract and its potential for absorption delay. On-demand therapy is now available for patients experiencing episodic or intermittent need for rapid and reliable onset of benefit. On-demand therapy may also provide an alternative to more invasive treatment such as infusion of levodopa/carbidopa intestinal gel and for patients whose OFF episodes are not controlled despite deep brain stimulation.

An evaluation of the efficacy and value of CVT-301 for the treatment of Parkinson's disease

Introduction: Levodopa is the most effective drug in the treatment of Parkinson's disease, but its chronic treatment is linked to the occurrence of motor complications with fluctuations of motor performance and dyskinesia. Unpredictable OFF episodes can be severe and disabling and current rescue medications cannot always be used safely. Rescue therapy is characterized by a rapid and predictable ON response and the safety profile of levodopa will represent a major advantage for patients affected by unresponsive OFF episodes.Areas covered: CVT-301 is a new inhaled formulation of LD recently developed as a self-administered treatment for OFF periods. Herein, the pharmacodynamic and pharmacokinetic properties, efficacy, and safety of CVT-301 are reviewed.Expert opinion: CVT-301 may offer several potential advantages including increased systemic bioavailability through pulmonary absorption, rapid onset of action, avoidance of first-pass drug metabolism, and less plasma level variability. It should be noted that the delivery device used has been described as relatively simple to use, but the few steps required to prepare and self-administer the dose can be challenging for PD patients during their OFF state. Additionally, resolution of an OFF episode requires the administration of two capsules of CVT-301, which further complicates the use of the device.