Maintenance of response to oral octreotide compared with injectable somatostatin receptor ligands in patients with acromegaly: a phase 3, multicentre, randomised controlled trial.

Background: Despite biochemically responding to injectable somatostatin receptor ligands (iSRLs), many patients with acromegaly experience treatment burdens. We aimed to assess maintenance of biochemical response and symptomatic control with oral octreotide capsules versus iSRLs in patients with acromegaly who previously tolerated and responded to both.

Methods: This global, open-label, randomised controlled phase 3 trial was done in 29 clinical sites in Austria, France, Germany, Hungary, Italy, Lithuania, Russia, Serbia, Spain, and the USA. Eligible patients were adults aged 18-75 years with acromegaly who were receiving iSRLs (long-acting octreotide or lanreotide autogel) for at least 6 months before baseline with a stable dose for at least 4 months, and were deemed to be biochemically responding (insulin-like growth factor I [IGF-I] <1·3 × upper limit of normal [ULN] and mean integrated growth hormone <2·5 ng/mL). In the 26-week run-in phase, all patients received oral octreotide (40 mg a day, optional titration to 60 or 80 mg a day). Eligibility for the randomised treatment phase was completion of the run-in phase as a biochemical responder (IGF-I <1·3 × ULN and mean integrated growth hormone <2·5 ng/mL at week 24) and investigator assessment of acromegaly being adequately controlled. Patients were randomly assigned (3:2) to oral octreotide capsules or iSRL at the same dose and interval as before enrolment. Randomisation and drug dispensing were conducted through a qualified randomisation service provider (eg, interactive web or voice response system). The primary endpoint was a non-inferiority assessment (margin -20 percentage points) of proportion of participants maintaining biochemical response throughout the randomised treatment phase (IGF-I <1·3 × ULN using time-weighted average; assessed by comparing the lower bound of the 2-sided 95% CI for the difference in biochemical response between groups). IGF-I was assessed once a month during the run-in and randomised treatment phases (single sample). Efficacy and safety assessments were performed on the randomised population. This trial is registered with ClinicalTrials.gov, NCT02685709.

Findings: Between Feb 11, 2016, and Aug 20, 2020, 218 patients were assessed for eligibility. 72 patients were excluded, and 146 participants were enrolled into the run-in phase. 116 patients completed the run-in phase and 30 participants discontinued treatment. 92 participants were randomly assigned to oral octreotide (n=55) or iSRL (n=37). 50 (91%) of 55 participants who received oral octreotide (95% CI 44-53) and 37 (100%) of 37 participants who received iSRLs (34-37) maintained biochemical response. The lower bound of the 2-sided 95% CI for the adjusted difference in proportions between the two treatment groups achieved the prespecified non-inferiority criterion of -20% (95% CI -19·9 to 0·5). 19 (35%) of 55 participants in the oral octreotide group and 15 (41%) of 37 participants in the iSRL group had treatment-related adverse events; the most common of which in both groups were gastrointestinal.

Interpretation: Oral octreotide was non-inferior to iSRL treatment, and might be a favourable alternative to iSRLs for many patients with acromegaly.

Funding: Chiasma.

Translation: For the Russian translation of the abstract see Supplementary Materials section.