MON-297 Withdrawal from Long-Acting Somatostatin Receptor Ligand Injections in Adult Patients with Acromegaly: Results from the Phase 3, Randomized, Double-Blind, Placebo-Controlled CHIASMA OPTIMAL Study

Data on the impact of withdrawal from long-acting somatostatin receptor ligand (SRL) injections on disease activity in patients with acromegaly are limited. The phase 3 Octreotide capsules versus Placebo Treatment In MultinationAL centers (OPTIMAL) study assessed the efficacy and safety of oral octreotide capsules in adult patients with acromegaly responding to injectable SRL therapy. The placebo-controlled arm of this study allowed for assessment of acromegaly biochemical and disease activity in patients after withdrawal from SRL treatment. A multinational, randomized, placebo-controlled study was conducted in 56 adult patients with active acromegaly. Patients were ≥ 18 years of age, had evidence of active disease (defined as IGF-I ≥1.3 x ULN after last pituitary surgery), and an average IGF-I ≤ 1.0 x ULN in response to a stable dose of SRL injection. Patients were randomized, 1 month following their last injection, to octreotide capsule or placebo for 36 weeks, with an option to enroll in an open-label extension. The primary aim was to determine the proportion of patients maintaining biochemical response, defined as IGF-I ≤1.0 x ULN (average of week 34 and 36). The trial met the primary endpoint, with 58% (16/28) of patients receiving octreotide capsules maintaining IGF-I response vs 19% (5/28) receiving placebo (P=0.008). The median time to loss of response (2 criteria evaluated: IGF-I >1.0 and ≥ 1.3 x ULN for 2 consecutive visits) was 16 weeks in the placebo group, while it was not reached in the octreotide capsule group. Of the 5 patients in the placebo group who maintained their biochemical response at 36 weeks, only 2 (7% of placebo group) did not meet loss of response criteria. When IGF-I values for any 2 consecutive visits were analyzed for patients receiving placebo, 93% (26/28) lost response based on IGF-I > 1 x ULN and 79% (22/28) lost response based on IGF-I ≥ 1.3 x ULN. Irrespective of biochemical control of acromegaly, 26/28 patients receiving placebo experienced active disease-related symptoms reported as AEs of special interest (AESIs). Most common AESIs (≥ 5%) included arthralgia/arthritis (60.7%), soft tissue swelling (35.7%), headache (32.1%), hyperhidrosis (25%), carpal tunnel (14.3%), musculoskeletal pain (14.3%), weight increased (7.1%) and tongue disorders (7.1%). The 5 patients receiving placebo with controlled IGF-I at 36 weeks received active medical treatment in the open label extension by decision of their study PIs, as they were deemed to have either lost their response during the study or had continuing active acromegaly symptoms. 93% of patients receiving placebo lost response following withdrawal of injectable SRLs, with a median duration of 16 weeks. All 5 patients receiving placebo who met the primary endpoint criteria at the end of the study were assessed clinically to have active disease and were continued on oral SRL treatment in the open label extension.