Abstract
Injectable somatostatin receptor ligands (iSRL) are the most frequently utilized medical therapy in patients with acromegaly; however, satisfaction rates are suboptimal. Injections can result in local erythema, discomfort and subcutaneous nodule formation, encompassed with the inconvenience of attending either primary or secondary care medical facilities for injections every 4 weeks. Some patients also note breakthrough of acromegaly-related symptoms towards the end of the injection cycle. To improve acceptance and ultimately improve wellbeing of these individuals, two oral SRLs, oral octreotide capsules (OOC) and paltusotine, have been developed. The OOC combines an enteric coating to allow delivery to the small intestines and a transient permeability enhancer to enable oral bioavailability. Comparable octreotide levels are obtained with twice-daily OOC and subcutaneous octreotide 100 µg. Phase III studies show OOC to maintain equivalent biochemical control in at least 60% of patients previously receiving a stable dose of iSRL. In longer-term studies, the response to OOC was durable up to 3 years. Paltusotine is a novel potent orally available non-peptidyl somatostatin receptor subtype-2 ligand. Studies in healthy volunteers show dose-dependent suppression of growth hormone-releasing hormone-induced growth hormone secretion and suppression of insulin-like growth factor-I (IGF-I) with repeat doses. In the recent phase II study, patients with acromegaly who were partial responders (IGF-I 1.0 - 2.5 x upper limit of normal) to monotherapy with iSRL when switched to once-daily paltusotine maintained control of IGF-I within 20% of baseline or lower in 87% after 13 weeks. Adverse events with both OOC and paltusotine were reflective of those recognized with iSRL and occurred at a similar frequency. OOC and paltusotine are well-received additions to the therapeutic armamentarium in medical therapy for the management of acromegaly; however, further data on efficacy, tumour control and shrinkage are required to allow positioning of this medication within the management algorithm for acromegaly.