An evaluation of pegvisomant as long-term monotherapy in acromegalic patients from the global safety surveillance study ACROSTUDY reported increases or increases/decreases in the tumor sizes in 12 of 542 subjects (2.2%).7 Another study reviewed the efficacy of pegvisomant as a monotherapy for acromegaly over a 10-year period, and showed 6 of 64 (9.4%) cases with tumor growth.123 Pegvisomant has also been evaluated in a combination therapy with SRL, particularly with respect to normalizing the IGF1 concentration in acromegalic patients who have failed SRL monotherapy. The gene discussed is IGF1; the disease is acromegaly.