Endocrinology · Medical Literature
Reduced breakthrough symptom exacerbations in patients with biochemically controlled acromegaly switched from injected depot somatostatin receptor ligands to once-daily oral paltusotine in the PATHFNDR-1 clinical trial.
Abstract
To evaluate the hypothesis that breakthrough acromegaly symptom exacerbation frequency would be reduced after switching biochemically controlled patients from depot somatostatin receptor ligand (SRL) injections to once-daily oral paltusotine. Biochemical disease control (insulin-like growth factor 1 [IGF-I]) and Acromegaly Symptom Diary (ASD) data were analyzed from PATHFNDR-1, a 36-week, randomized, placebo-controlled, double-blind, phase 3 trial of paltusotine in patients with acromegaly biochemically controlled (IGF-I ≤ 1.0× ULN) with SRLs. The ASD measured the daily severity of 7 core and 2 exploratory acromegaly symptoms, each rated on a scale from 0 to 10 based on 24-hour recall. Breakthrough acromegaly symptom exacerbations were defined as ≥ 2-point increases for any individual symptom score, comparing a 2-day average with the prior 2-day average. Despite no significant changes in IGF-I levels or overall core symptom severity scores, mean (SE) symptom exacerbation frequencies declined progressively after switching to paltusotine, from 30.2% (5.6%) of days during screening (SRL treatment) to 6.2% (1.6%) of days (n = 22, p < 0.0001). The reduction in individual symptom exacerbation frequencies with paltusotine treatment was consistent across all acromegaly symptoms assessed. IGF-I levels did not correlate significantly with symptom severity scores or symptom variability. In patients with acromegaly biochemically controlled with injected SRLs, switching to once-daily oral paltusotine was associated with stable biochemical control, stable symptom severity, and a significantly reduced frequency of symptom exacerbations. A simple daily symptom assessment tool provided important information pertaining to acromegaly disease control that was not apparent from IGF-I measurements.
Clinical relevance
This article addresses a clinically underrecognized phenomenon in biochemically controlled acromegaly: breakthrough symptom exacerbations that occur despite normalized IGF-I on depot SRL injections, likely attributable to the pharmacokinetic variability inherent to monthly injectable formulations. The study targets patients already on SRL therapy who achieve biochemical control but continue to experience symptomatic fluctuations, a population for whom oral paltusotine represents a mechanistically distinct therapeutic option. Clinicians managing acromegaly should attend to this finding now given the recent availability of oral SRL agents and the demonstrated dissociation between IGF-I levels and symptom burden.
Key findings
1. Breakthrough symptom exacerbation frequency declined significantly after switching from injected depot SRLs to once-daily oral paltusotine, from a mean (SE) of 30.2% (5.6%) of days during SRL-based screening to 6.2% (1.6%) of days on paltusotine (n = 22, p < 0.0001). 2. The reduction in symptom exacerbation frequency was consistent across all 7 core and 2 exploratory acromegaly symptoms assessed by the Acromegaly Symptom Diary (ASD), indicating a broad symptomatic benefit rather than improvement in isolated domains. 3. Despite the marked reduction in exacerbation frequency, overall core symptom severity scores did not change significantly, suggesting paltusotine reduces intra-patient symptom variability without necessarily altering mean symptom burden. 4. IGF-I levels remained stable during the 36-week trial, confirming that switching from injectable to oral SRL maintained biochemical disease control (IGF-I ≤ 1.0× ULN) in this controlled population. 5. IGF-I levels did not correlate significantly with symptom severity scores or symptom variability, highlighting that biochemical markers alone are insufficient surrogates for patient-reported symptomatic disease control. 6. The ASD — a daily 0–10 scale diary capturing 24-hour recall of symptom severity with exacerbations defined as ≥2-point increases over a 2-day rolling average — detected clinically meaningful disease fluctuation that was not apparent from IGF-I measurements alone.
Practice implications
Endocrinologists should consider transitioning biochemically controlled acromegaly patients who report symptomatic fluctuations or injection-related quality-of-life burden from depot SRL injections to once-daily oral paltusotine, as this switch appears to stabilize symptom variability while maintaining IGF-I control. IGF-I monitoring alone is insufficient to capture the full therapeutic response in acromegaly; incorporation of validated patient-reported outcome tools such as the ASD into routine clinical follow-up should be considered to detect breakthrough symptom exacerbations that may otherwise go unrecognized. Patient selection for oral SRL therapy should focus on those with confirmed biochemical control on injectable SRLs, as the PATHFNDR-1 trial specifically enrolled IGF-I–controlled patients, and extrapolation to uncontrolled disease requires further evidence.