Background: Respiratory impairment is a major concern in amyotrophic lateral sclerosis (ALS), shortening survival and lowering quality of life. One therapy with promise to delay respiratory decline in ALS is acute intermittent hypoxia (AIH), consisting of alternating periods of breathing mildly hypoxic (9%-12% O2) and normoxic (21% O2) gas. AIH stimulates spinal, serotonin-dependent neuroplasticity in rodent models, conferring functional benefits in diverse physiological systems without detectable pathology. However, in rodent models, AIH-induced neuroplasticity is constrained by distinct signaling cascades initiated by spinal adenosine.
Objective: We propose to investigate a therapeutic strategy to delay breathing compromise in those living with ALS by combining a selective adenosine 2A (A2A) receptor inhibitor (istradefylline) with AIH. The fundamental hypothesis guiding this proposal is that a single AIH trial after pretreatment with istradefylline enhances respiratory neuroplasticity versus AIH or sham intervention.
Methods: We propose to evaluate resting breathing, respiratory strength, and participant-reported symptoms in adults living with ALS after combined istradefylline plus AIH. A mixed within- and between-participant study design incorporates 4 test sessions, separated by approximately 2 weeks (±5 days). Testing conditions include single sessions of AIH + istradefylline, AIH + placebo, sham AIH (ie, normoxia) + placebo, and sham AIH + istradefylline. Safety and feasibility will be characterized using the rate of adverse events, changes in vital signs, and participant-reported breathing sensations (Aim 1). Neuroplasticity of breathing and motor function will be evaluated as changes in resting breathing, voluntary respiratory strength, respiratory control, and maximal pinch force (Aim 2).
Results: As of January 2025, with a target sample of 16 participants in each group, 10 participants with ALS and 5 control participants completed study procedures. Recruiting is ongoing, and the final participant will complete the study by December 2025. Publication of results is expected by the end of 2026.
Conclusions: These aims will provide crucial data regarding the preliminary safety and feasibility of this paired intervention and help optimize therapeutic AIH as a rehabilitation strategy, thereby guiding further research concerning this novel treatment for ALS.
Trial registration: ClinicalTrials.gov NCT05377424; https://clinicaltrials.gov/study/NCT05377424.
International registered report identifier (irrid): DERR1-10.2196/76105.
Keywords: acute intermittent hypoxia; adenosine A2A receptor; amyotrophic lateral sclerosis; neuronal plasticity; respiration.
©Priscila Sales de Campos, May Smith-Hublou, Wendy L Olsen, Wagner Souza Leite, James P Wymer, Nicholas J Napoli, Alicia K Vose, Michael T Pulley, Gordon S Mitchell, Barbara K Smith. Originally published in JMIR Research Protocols (https://www.researchprotocols.org), 07.11.2025.