Long-term safety and treatment outcomes of pegvisomant in Japanese patients with acromegaly: results from the post-marketing surveillance

This post-marketing surveillance is to investigate the long-term safety and effectiveness of the growth hormone receptor antagonist pegvisomant, which is used in patients with acromegaly in routine clinical practice. This surveillance included all cases treated with pegvisomant during the study period from the start of marketing (June 5, 2007) to December 2015. Data for 251 patients with acromegaly treated with pegvisomant were collected from 119 institutions nationwide in Japan. Eighty-five patients received pegvisomant monotherapy throughout their treatment, while 165 patients were treated with somatostatin analogue or dopamine agonist in combination with pegvisomant. Mean dose of pegvisomant was 10.6 ± 6.1 mg/day in the entire treatment period (except for initial loading dose). The incidence of adverse drug reactions was 35.6% (89/250). No new safety concerns related to long-term treatment were observed. The major investigation items of incidence of abnormal liver function and tumor enlargement were 16.0% (40/250), and 5.2% (13/250) respectively. Efficacy at the final evaluation point was 96.4% (217/225) based on the overall clinical judgement of attending physicians, and efficacy in each observation period was over 94%. Improvement in IGF-I levels and clinical symptoms scores were also observed by comparing the data at baseline with each observation point during treatment. IGF-I normalization rate was 68.2% at 5 years. Pegvisomant monotherapy showed similar improvement here as well. These results suggest that long-term treatment with pegvisomant is effective in clinical practice.