Conversion to IPX066 from Standard Levodopa Formulations in Advanced Parkinson's Disease: Experience in Clinical Trials

Levodopa Dose Equivalency in Parkinson's Disease: Updated Systematic Review and Proposals

BACKGROUND

To compare drug regimens across clinical trials in Parkinson's disease (PD) conversion formulae between antiparkinsonian drugs have been developed. These are reported in relation to levodopa as the benchmark drug in PD pharmacotherapy as 'levodopa equivalent dose' (LED). Currently, the LED conversion formulae proposed in 2010 by Tomlinson et al. based on a systematic review are predominantly used. However, new drugs with established and novel mechanisms of action and novel formulations of longstanding drugs have been developed since 2010. Therefore, consensus proposals for updated LED conversion formulae are needed.

OBJECTIVES

To update LED conversion formulae based on a systematic review.

METHODS

The MEDLINE, CENTRAL, and Embase databases were searched from January 2010 to July 2021. Additionally, in a standardized process according to the GRADE grid method, consensus proposals were issued for drugs with scarce data on levodopa dose equivalency.

RESULTS

The systematic database search yielded 3076 articles of which 682 were eligible for inclusion in the systematic review. Based on these data and the standardized consensus process, we present proposals for LED conversion formulae for a wide range of drugs that are currently available for the pharmacotherapy of PD or are expected to be introduced soon.

CONCLUSIONS

The LED conversion formulae issued in this Position Paper will serve as a research tool to compare the equivalence of antiparkinsonian medication across PD study cohorts and facilitate research on the clinical efficacy of pharmacological and surgical treatments as well as other non-pharmacological interventions in PD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

GOCOVRI® (amantadine) extended-release capsules in Parkinson's disease

Amantadine is an old, antiviral compound, which moderately improves motor behavior in Parkinson's disease. Its current resurgence results from an innovative, delayed uptake and extended release amantadine hydrochloride capsule, given at bedtime once daily. It is the only approved compound for reduction of involuntary movements, so called dyskinesia, in fluctuating orally levodopa treated patients. It additionally ameliorates 'off'-intervals characterized by impaired motor behavior. These beneficial effects result from higher and more continuous brain delivery of amantadine. Future clinical research is warranted on preventive effects of this amantadine capsule combined with enzyme blockers of central monoamine oxidase B and peripheral catechol-O-methyltransferase on motor complications in orally levodopa treated patients, as all these pharmacological principles support the concept of continuous dopamine substitution.

Experimental Dopamine Reuptake Inhibitors in Parkinson's Disease: A Review of the Evidence

Parkinson’s disease (PD) is the second most chronic neurodegenerative disorder worldwide. Deficit of monoamines, particularly dopamine, causes an individually varying compilation of motor and non-motor features. Constraint of presynaptic uptake extends monoamine stay in the synaptic cleft. This review discusses possible benefits of dopamine reuptake inhibition for the treatment of PD. Translation of this pharmacologic principle into positive clinical study results failed to date. Past clinical trial designs did not consider a mandatory, concomitant stable inhibition of glial monoamine turnover, i.e. with monoamine oxidase B inhibitors. These studies focused on improvement of motor behavior and levodopa associated motor complications, which are fluctuations of motor and non-motor behavior. Future clinical investigations in early, levodopa- and dopamine agonist naïve patients shall also aim on alleviation of non-motor symptoms, like fatigue, apathy or cognitive slowing. Oral levodopa/dopa decarboxylase inhibitor application is inevitably necessary with advance of PD. Monoamine reuptake (MRT) inhibition improves the efficacy of levodopa, the blood brain barrier crossing metabolic precursor of dopamine. The pulsatile brain delivery pattern of orally administered levodopa containing formulations results in synaptic dopamine variability. Ups and downs of dopamine counteract the physiologic principle of continuous neurotransmission, particularly in nigrostriatal, respectively mesocorticolimbic pathways, both of which regulate motor respectively non-motor behavior. Thus synaptic dopamine pulsatility overwhelms the existing buffering capacity. Onset of motor and non-motor complications occurs. Future MRT inhibitor studies shall focus on a stabilizing and preventive effect on levodopa related fluctuations of motor and non-motor behavior. Their long-term study designs in advanced levodopa treated patients shall allow a cautious adaptation of oral l-dopa therapy combined with a mandatory inhibition of glial monoamine turnover. Then the evidence for a preventive and beneficial, symptomatic effect of MRT inhibition on motor and non-motor complications will become more likely.

Real-World Experience with Carbidopa-Levodopa Extended-Release Capsules (Rytary®): Results of a Nationwide Dose Conversion Survey

Background

The introduction of carbidopa-levodopa extended-release (CD-LD ER) capsules (Rytary®) did not go as smoothly as expected, largely due to difficulty around dose conversion from available immediate-release (IR) levodopa (LD) formulations. The dose conversion table in the CD-LD ER prescribing information was similar to the table used in the pivotal clinical trial and is considered by many prescribing HCPs to be less than optimal. By the end of the dose conversion period in that trial, dosing in 76% of subjects was adjusted for symptom control; roughly 60% of patients required a higher dose and about half required more frequent administration than the recommended TID dosing.

Objective

The primary objective of our nationwide (US) survey was to determine the dose conversion strategy most commonly employed by CD-LD ER frequent prescribers. The survey also aimed to explore additional features regarding CD-LD ER use in clinical practice.

Methods

A survey consisting of 21 multiple-choice questions was developed and administered to experts in the use of CD-LD ER, based on prescription volume.

Results

Of the 394 HCPs who were invited to participate, 90 (23%) HCPs completed the survey. All respondents were aware of the dose conversion table; the largest group did not find the table to be helpful and did not use it to convert patients to CD-LD ER. The most common strategy in calculating the CD-LD ER dose was based on the total daily LD IR dose, with the majority of that group initiating dose conversion by doubling the total daily LD dose from CD-LD IR and administering CD-LD ER one less time per day.

Conclusion

Overall, most survey respondents agreed that a good starting point for CD-LD ER conversion could be doubling the daily LD IR dose and administering it one time less frequently. Moreover, rapid patient follow-up after initial dose conversion to allow for further dose adjustments plays a critical role in achieving success. Gaining experience over time is important for satisfactory conversion.

Conversion of L-dopa to Extended Release L-dopa (Rytary®) in Patients with Fluctuating Parkinson's Disease: Predictors of Dose

BACKGROUND

A new extended release levodopa capsule (C/L ERC), Rytary®, has demonstrated improved "on" time in fluctuating Parkinson's disease patients, compared to optimally dosed immediate release levodopa. The milligram dosing, however, differs markedly and no empiric ratio or formula for dose conversion currently exists.

OBJECTIVE

To determine the most effective conversion strategy from C/L to C/L ERC.

METHODS

We reviewed fluctuating PD patients with problematic "off" time who were converted to C/L ERC using a semi-structured dose titration schedule, and collected data regarding basic efficacy, tolerability, and dosing, in order to determine an empirically based dose conversion formula. We collected demographics, PD historic data, and other medication use.

RESULTS

Eighty fluctuating PD patients were given C/L ERC samples, 68 took at least one dose [46 male (67.6%), age 66.6±10.3 y], and 62 had adequate data for dose convergence calculations. At a mean follow-up of 119±101 days, [Range: 24-355 days], 43/68 (63.3%) remained on C/L ERC. CGI-I of "much improved" or "very much improved" was reported by 27/62 (43.5%) and dyskinesia scores from the Movement Disorder Society Unified Parkinson's Disease Rating Scale item 4.1, (0-4 range)) tended to improve from 0.9±1.1 to 0.5±0.6, P = 0.08. The mean individual daily ratio was 2.0±0.6 : 1, [range 1.0-3.5]. A lower number of baseline daily L-dopa doses predicted a higher conversion ratio, but pre-conversion dyskinesia did not.

CONCLUSIONS

This retrospective study found that C/L ERC was generally well tolerated and preferred by many patients. The mean total daily conversion ratio is 2 : 1.

Dosing Patterns during Conversion to IPX066, Extended-Release Carbidopa-Levodopa (ER CD-LD), in Parkinson's Disease with Motor Fluctuations

Background

IPX066 is an extended-release (ER) oral formulation of carbidopa-levodopa (CD-LD). Following an initial peak at about one hour, plasma LD concentrations are maintained for about 4-5 hours.

Objective

To present dosing factors that may affect the successful conversion to ER CD-LD from other LD formulations.

Methods

Two-phase 3 studies of ER CD-LD vs. immediate-release (IR) CD-LD (ADVANCE-PD) and vs. CD-LD + entacapone (CLE; ASCEND-PD) in subjects with advanced PD included a 6-week, open-label conversion to ER CD-LD prior to treatment randomization. The “converted” daily LD dose ratio and dose frequency for ER CD-LD were compared to the prior LD treatment regimens at study entry.

Results

The average daily LD dose ratio at the end of dose conversion to ER CD-LD was approximately 2.1 for IR CD-LD and 2.8 for CLE. The final dose ratios tended to be slightly higher for participants taking lower LD doses at study entry but independent of dose frequency. ER CD-LD dose frequency increased with increasing LD dose and dose frequency at study entry. Participants on higher baseline LD doses ≥800 mg and dose frequencies ≥6 tended to have higher rates of discontinuation during conversion to ER CD-LD.

Conclusions

Converting participants from other LD formulations to ER CD-LD is based on their current LD regimen. For the most common daily doses (≤1250 mg) and dose frequencies (<7) of LD, final mean dose ratios were within tight ranges of 2.1 to 2.4 for IR CD-LD (ADVANCE-PD) and 2.4 to 2.8 for CLE (ASCEND-PD) and were generally independent of the LD dosing frequency at study entry. These trials are registered with NCT00974974, NCT01130493.

Levodopa in Parkinson's Disease: Current Status and Future Developments

BACKGROUND

Ever since the pioneering reports in the 60s, L-3,4-Dioxyphenylalanine (levodopa) has represented the gold standard for the treatment of Parkinson's Disease (PD). However, long-term levodopa (LD) treatment is frequently associated with fluctuations in motor response with serious impact on patient quality of life. The pharmacokinetic and pharmacodynamic properties of LD are pivotal to such motor fluctuations: discontinuous drug delivery, short half-life, poor bioavailability, and narrow therapeutic window are all crucial for such fluctuations. During the last 60 years, several attempts have been made to improve LD treatment and avoid long-term complications.

METHODS

Research and trials to improve the LD pharmacokinetic since 1960s are reviewed, summarizing the progressive improvements of LD treatment.

RESULTS

Inhibitors of peripheral amino acid decarboxylase (AADC) have been introduced to achieve proper LD concentration in the central nervous system reducing systemic adverse events. Inhibitors of catechol-O-methyltransferase (COMT) increased LD half-life and bioavailability. Efforts are still being made to achieve a continuous dopaminergic stimulation, with the combination of oral LD with an AADC inhibitor and a COMT inhibitor, or the intra-duodenal water-based LD/ carbidopa gel. Further approaches to enhance LD efficacy are focused on new non-oral administration routes, including nasal, intra-duodenal, intrapulmonary (CVT-301) and subcutaneous (ND0612), as well as on novel ER formulations, including IPX066, which recently concluded phase III trial.

CONCLUSION

New LD formulations, oral compounds as well as routes have been tested in the last years, with two main targets: achieve continuous dopaminergic stimulation and find an instant deliver route for LD.

Extended-release oral capsule of carbidopa-levodopa in Parkinson disease

Motor fluctuations complicate the treatment of patients with Parkinson's disease receiving levodopa. Extended-release carbidopa-levodopa has a pharmacokinetic profile that provides a more continuous levodopa serum concentration. Patients taking this formulation can expect longer duration of action and fewer doses per day, similar clinical improvement when compared to other levodopa formulations, and with a theoretically lower risk of developing motor fluctuations. Several studies, including three randomized control trials provide evidence for the efficacy, safety and tolerability of extended release carbidopa-levodopa in patients with both early and advanced Parkinson's disease are reviewed here. Also provided is guidance for dosing of and conversion to extended release carbidopa-levodopa as well as a discussion of its place in the clinical practice.

Recent advances in treating Parkinson's disease

This article summarizes (1) the recent achievements to further improve symptomatic therapy of motor Parkinson’s disease (PD) symptoms, (2) the still-few attempts to systematically search for symptomatic therapy of non-motor symptoms in PD, and (3) the advances in the development and clinical testing of compounds which promise to offer disease modification in already-manifest PD. However, prevention (that is, slowing or stopping PD in a prodromal stage) is still a dream and one reason for this is that we have no consensus on primary endpoints for clinical trials which reflect the progression in prodromal stages of PD, such as in rapid eye movement sleep behavior disorder (RBD) —a methodological challenge to be met in the future.

Treatment Strategies in Early Parkinson's Disease

The clinicians' approach to the treatment of early Parkinson's disease (PD) should take into account numerous aspects, including how to inform a patient upon diagnosis and the critical decision of what therapy to adopt and when to start it. The treatment of the motor disorder associated with early PD needs to consider several crucial factors, such as age at onset, comorbidities, and the patient's functional requirements, and cannot be summarized in a simple formula. In younger patients (i.e., before the age of 70) and in those without high functional requirements, treatment is usually initiated with dopamine agonists and/or monoamine oxidase-B enzyme inhibitors (MAO-B I). By contrast, in older patients, or in those with high functional requirements, low doses of levodopa are generally used when treatment is started. In younger patients, levodopa should be added to dopamine agonists and/or MAO-B I, as required by disease progression, whereas in older patients, when response to levodopa alone is not satisfactory, dopamine agonists or catechol-O-methyltransferase inhibitors may subsequently be added.

Optimizing extended-release carbidopa/levodopa in Parkinson disease: Consensus on conversion from standard therapy

Purpose of review:

To help clinicians optimize the conversion of a patient's Parkinson disease pharmacotherapy from immediate-release carbidopa/levodopa (IR CD/LD) to an extended-release formulation (ER CD/LD).

Recent findings:

Eleven movement disorders specialists achieved consensus positions on the modification of trial-based conversion guidelines to suit individual patients in clinical practice.

Summary:

Because the pharmacokinetics of ER CD/LD differ from those of IR CD/LD, modification of dosage and dosing frequency are to be expected. Initial regimens may be based on doubling the patient's preconversion levodopa daily dosage and choosing a division of doses to address the patient's motor complications, e.g., wearing-off (warranting a relatively high ER CD/LD dose, possibly at a lower frequency than for IR CD/LD) or dyskinesia (warranting a relatively low dose, perhaps at an unchanged frequency). Patients should know that the main goal of conversion is a steadier levodopa clinical response, even if dosing frequency is unchanged.

Novel Levodopa Formulations for Parkinson's Disease

Levodopa remains the most effective treatment for Parkinson's disease and is considered the gold standard therapy. However, disease progression and changes in the gastrointestinal tract result in a declining window of treatment response in a majority of patients. Efforts have been made recently to improve levodopa bioavailability either by developing more effective oral formulations or by innovating routes of administration (intestinal infusion, transcutaneous or inhaled levodopa). IPX066 is a novel levodopa-carbidopa (LD/CD) oral formulation combining immediate-release (IR) and extended-release (ER) LD/CD recently approved in the USA and the EU. Levodopa-carbidopa intestinal gel (LCIG) is an approved therapy consisting of a suspension of levodopa and carbidopa infused directly into the proximal jejunum via a percutaneous endoscopic gastrojejunostomy (PEG-J) tube through a portable infusion pump. Ongoing studies are evaluating the 'accordion pill' (AP09004), an ER LD/CD formulation with gastroretentive properties. ND0612 is a proprietary liquid formulation of LD/CD that enables subcutaneous administration via a small patch-pump device, and CVT-301 is a levodopa inhalation powder with rapid onset of action; both are currently in active studies. Other novel formulations have been discontinued, including DM-1992, which is a bilayer formulation containing an IR LD/CD layer and an ER LD/CD layer with gastroretentive properties, and XP21279, a novel oral levodopa prodrug that is absorbed from the small and large intestine by high-capacity nutrient transporters expressed throughout the gastrointestinal system. ODM-101 is a new oral formulation of levodopa/carbidopa/entacapone that contains a higher amount of carbidopa (65 or 105 mg), but no active studies are underway. The current review aims to summarize the pharmacokinetic aspects, clinical efficacy, and potential adverse events of novel levodopa formulations currently available or under development.

Physicians' experience with RYTARY (carbidopa and levodopa) extended-release capsules in patients who have Parkinson disease

A discussion between Dr. Dee Silver and Dr. Richard Trosch provides insight and advice for physicians considering a switch from immediate-release carbidopa-levodopa (IR CD-LD) to RYTARY as a treatment for patients with Parkinson disease (PD). The dialogue describes how they identify patients with PD who may and may not be successful switching to RYTARY, how they approach the conversion process and patient compliance, and how they address some side effects that may occur after patients begin taking RYTARY. The clinicians also discuss their experiences with how long it takes to establish a stable regimen as well as provide general advice regarding conversion from treatment with IR CD-LD to RYTARY.

Carbidopa/Levodopa ER Capsules (Rytary(®), Numient™): A Review in Parkinson's Disease

A new extended-release (ER) capsule formulation of carbidopa/levodopa (Rytary(®), Numient™, IPX066) is available for the treatment of Parkinson's disease (PD). Carbidopa/levodopa ER capsules contain beads of carbidopa and levodopa, designed to release the drugs at different rates in the gastrointestinal tract and provide constant therapeutic levodopa concentrations that are maintained for 4-5 h (after an initial peak at ≈ 1 h). In randomized phase III trials, oral carbidopa/levodopa ER was significantly more effective than placebo with regard to improving motor symptoms and activities of daily living in patients with early PD after 30 weeks' treatment, and provided significantly greater reductions in daily 'off-time' in patients with advanced PD than immediate-release (IR) carbidopa/levodopa or carbidopa/levodopa IR plus entacapone after a treatment period of 13 and 2 weeks, respectively, without increasing troublesome dyskinesia. The efficacy of carbidopa/levodopa ER was maintained during a 9-month open-label extension in patients with early or advanced PD. Carbidopa/levodopa ER was generally well tolerated in clinical trials, with the most common adverse events in the extension study being nausea and insomnia in patients with early PD and falls and dyskinesia in patients with advanced PD. Thus, carbidopa/levodopa ER is an effective and generally well-tolerated treatment option for the motor symptoms of PD, reducing periods of 'off-time' compared with carbidopa/levodopa IR without increasing troublesome dyskinesia.