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Mechanism-Based Therapy With Ampreloxetine for Neurogenic Orthostatic Hypotension in Multiple System Atrophy: A
Roy Freeman1, Horacio Kaufmann2, Italo Biaggioni3
1Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA.
Background And Objectives:
Degeneration of the central autonomic network with relative sparing of peripheral autonomic neurons underlies neurogenic orthostatic hypotension in patients with multiple system atrophy (MSA). Ampreloxetine, a novel, selective, norepinephrine (NE) reuptake inhibitor, allows once-daily dosing to precisely target residual peripheral autonomic neurons. Based on the hypothesis that patients with MSA would be most responsive and the substantial unmet need for symptomatic therapy in this population, an MSA subgroup analysis was prespecified.
Methods:
We conducted a run-in 4-week, parallel-group, randomized controlled trial (SEQUOIA), followed by a pivotal enriched randomized withdrawal (RW) trial with 16-week open-label treatment and 6 weeks of 1:1 RW (REDWOOD). Inclusion criteria for the MSA subgroup included (1) probable or possible MSA, (2) 3-minute orthostatic blood pressure (BP) fall >20/10 mm Hg, and (3) dizziness or lightheadedness score >4 points. Outcome measures included self-reported symptom burden captured on the 10-item OH Questionnaire (OHQ). Differences were analyzed using logistic regression and mixed-model repeated measures analysis.
Results:
Seventy-three patients with MSA entered the program (mean age 63 years old [range: 43-80], 52% male). Both SEQUOIA and REDWOOD did not meet their primary endpoints. In REDWOOD, 40 (61%) fulfilled enrichment criteria and were randomized. After 16-week open-label, OHQ symptom assessment (OHSA) composite domain scores improved 2.6 ± (SD = 2.1) points from pretreatment. The proportion of participants with treatment failure at week 6 of RW treatment period was 40% in the placebo arm and 15% in the ampreloxetine arm (p = 0.11). In secondary endpoints, at week 6 of RW, symptoms remained stable in the ampreloxetine group, but worsened on placebo (mean difference OHSA composite: -1.6 points ± 0.5; p = 0.0056, minimal clinically important worsening = 0.7-1.1 points). Standing for a short time favored ampreloxetine (-2.0 points ± 0.8; p = 0.015). Standing BP remained unchanged from open-label in the ampreloxetine group (systolic: 5.6 ± 4.1; diastolic: 3.7 ± 2.9 [SE] mm Hg) but fell after placebo withdrawal (systolic: -10.0 ± 4.5; diastolic: -6.0 ± 3.1 mm Hg). The catecholamine profile was consistent with NE transporter inhibition. There were no observed increases in supine BP.
Discussion:
In a prespecified subgroup analysis of MSA participants in the REDWOOD trial, patients randomized to placebo worsened, whereas those who were randomized to treatment maintained their open-label level of function.
Trial Registration Information:
REDWOOD trial, NCT03829657; first submitted to registry January 10, 2019; first participant enrolled February 22, 2019. SEQUOIA trial, NCT03750552; first submitted to registry November 20, 2018; first participant enrolled January 24, 2019. See ClinicalTrials.gov for full-protocol and statistical analysis plan.
Classification Of Evidence:
This study provides Class III evidence that in patients with MSA who had symptomatic benefit on orthostatic hypotension with ampreloxetine, there was no difference in the odds of treatment failures between those maintained on ampreloxetine and those withdrawn to placebo.
