Effectiveness of first-line pegvisomant monotherapy in acromegaly: an ACROSTUDY analysis.

OBJECTIVE: To examine the effectiveness and safety of primary pegvisomant monotherapy.

DESIGN: Retrospective analysis of data extracted from ACROSTUDY (global observational outcomes study of patients with acromegaly treated with pegvisomant).

METHODS: The earliest time to insulin-like growth factor 1 (IGF-1) normalization on pegvisomant monotherapy was determined. Both the proportion of patients who achieved IGF-1 normalization and the time to IGF-1 normalization on pegvisomant monotherapy were assessed.

RESULTS: Eligible patients included 28 subjects on primary medical therapy (PT) and 176 controls on adjunctive pegvisomant therapy treated postoperatively, including 43 who were naïve to medical therapy (NMT) and 133 who were previously treated medically and were washed out (WASH). IGF-1 normalization occurred in 76.9% (PT), 85.2% (NMT) and 78.3% (WASH) patients (P = NS). Median times to IGF-1 normalization were 0.5 year (PT), 0.7 year (NMT) and 0.6 year (WASH), P = NS. On survival analysis, the fraction of patients controlled on pegvisomant monotherapy was not different between groups. Higher baseline IGF-1 levels, obtained at study entry, predicted a lower likelihood of IGF-1 normalization on monotherapy (P = 0.012). Safety data include low prevalence of skin rashes, injection site reactions and reversible transaminase elevations. There was one patient (NMT) with a verified increase in tumor size.

CONCLUSIONS: Pegvisomant monotherapy, administered either as primary medical therapy or as adjunctive therapy according to local practice, led to IGF-1 normalization in >75% of patients. Pegvisomant monotherapy had a favorable safety profile, consistent with previous observations. Prospective data are needed to further evaluate the role of primary pegvisomant monotherapy in acromegaly.