Objective: Understand key efficacy outcomes used to assess adjunctive treatments to carbidopa/levodopa (CD/LD) for Parkinson’s disease (PD).

Background: CD/LD is widely considered the most effective treatment to address the motor symptoms of PD. Adjunctive treatments (eg, dopamine agonists, monoamine oxidase-B [MAO-B] inhibitors, catechol-o-methyl transferase [COMT] inhibitors, etc) are commonly used to improve motor function after OFF episodes develop in patients treated with CD/LD.

Method: A systematic literature review was conducted using Embase, MEDLINE, and Cochrane CENTRAL through Ovid to identify randomized controlled trials of adjunctive treatments for PD from January 1, 2006, to present. Drugs of interest included dopamine agonists, MAO-B inhibitors, COMT inhibitors, istradefylline, and amantadine. Two independent reviewers conducted screening and data extraction. Two levels of screening of search results were performed: level 1—title/abstract screening; level 2—full-text review. Alignment was obtained at each level before articles were excluded. Article exclusion rules included no patients with PD, incomplete trial, drugs of interest not used/use was not adjunctive to CD/LD, no safety/efficacy outcome (excludes phase 1 studies), not in English, no abstract, pediatric trial, characteristics/outcomes not reported by trial arm, and duplicate article.

Results: Among 103 records identified for title and abstract screening, 47 were eligible for full-text review and 28 were subsequently included for data extraction (23 original and 5 post hoc analyses), covering 12 different drugs. Ropinirole, rasagiline, and istradefylline were the most studied adjunctive treatments with 7, 6, and 4 publications, respectively. Three studies were not placebo controlled. The primary outcome was reported as change in OFF/ON time or Unified Parkinson’s Disease Rating Scale (UPDRS; Part II, Part III, or total) scores for 15 and 6 publications, respectively. Three studies of amantadine assessed change in the Unified Dyskinesia Rating Scale (UDysRS) as the primary outcome. Assessment periods for change in OFF/ON time, UPDRS, and UDysRS were variable and ranged from 8 weeks to 6 months.

Conclusion: Early assessment of the relative comparability of these randomized controlled trials suggests that it will be feasible to perform future indirect treatment comparative analyses across adjunctive treatments in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/systematic-literature-review-of-key-outcomes-used-to-assess-adjunctive-treatments-for-parkinsons-disease/