The main aim of this study is to assess the efficacy of the co-administration of lanreotide Autogel 120 mg (administered via deep sub-cutaneous injections every 28 days) and pegvisomant (administered at 40 to 120 mg per week via sub-cutaneous injection given once or twice a week) on IGF-1 levels over 28 weeks in acromegalic patients. The primary endpoint will be the percentage of acromegalic patients with normalised (age and sex adjusted) IGF-1 level at the end of the co-treatment period.