Clinical Pharmacodynamic Effects of the Growth Hormone Receptor Antagonist Pegvisomant: Implications for Cancer Therapy

• Published in: Clinical cancer research Vol. 13; no. 3; pp. 1000 - 1009
• Main Authors: DONGHUA YIN, VREELAND, Franzanne, SCHAAF, Larryj, MILLHAM, Robert, DUNCAN, Barbara A, SHARMA, Amarnath
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Association for Cancer Research 01.02.2007
• Subjects: Adult; Antineoplastic agents; Antineoplastic Agents - pharmacology; Biological and medical sciences; Biomarkers, Tumor; Cohort Studies; Female; Growth Hormone Receptor Antagonist; Healthy Subjects Clinical Trial; Human Growth Hormone - analogs & derivatives; Human Growth Hormone - pharmacology; Humans; IGF-I; Insulin-Like Growth Factor Binding Protein 3 - metabolism; Insulin-Like Growth Factor I - metabolism; Insulin-Like Growth Factor II - metabolism; Male; Medical sciences; Middle Aged; Octreotide; Octreotide - pharmacology; Pegvisomant; Pharmacology. Drug treatments; Receptors, Somatotropin - antagonists & inhibitors; Signal Transduction; Time Factors; Somatropin; Pharmacodynamics; Treatment; Adenohypophyseal hormone; Pegvisomant; Neurohypophyseal hormone; Somatotropin hormone; Antagonist; Malignant tumor; Biological activity; Hormonal receptor; Cancer
• ISSN: 1078-0432; 1557-3265
• DOI: 10.1158/1078-0432.CCR-06-1910

Purpose: The present study evaluated and compared the efficacy of pegvisomant and octreotide in blocking the growth hormone (GH) axis in humans based on pharmacodynamic biomarkers associated with the GH axis. The study also evaluated the safety of pegvisomant given at high s.c. doses for 14 days. Experimental Design: Eighty healthy subjects were enrolled in five cohorts: cohorts 1 to 3, s.c. pegvisomant at 40, 60, or 80 mg once daily × 14 days ( n = 18 per cohort); cohort 4, s.c. octreotide at 200 μg thrice daily × 14 days ( n = 18); and cohort 5, untreated control ( n = 8). Serial blood samples were collected to measure plasma concentrations of total insulin-like growth factor type I (IGF-I), free IGF-I, IGF-II, IGF-binding protein 3 (IGFBP-3), and GH in all subjects and serum pegvisomant concentrations in subjects of cohorts 1 to 3. All subjects receiving treatment were monitored for adverse events (AE). Results: After s.c. dosing of pegvisomant once daily for 14 days, the mean maximum suppression values of total IGF-I were 57%, 60%, and 62%, at 40, 60, and 80 mg dose levels, respectively. The maximum suppression was achieved ∼7 days after the last dose and was sustained for ∼21 days. Pegvisomant also led to a sustained reduction in free IGF-I, IGFBP-3, and IGF-II concentrations by up to 33%, 46%, and 35%, respectively, and an increase in GH levels. In comparison, octreotide resulted in a considerably weaker inhibition of total IGF-I and IGFBP-3 for a much shorter duration, and no inhibition of IGF-II. AEs in pegvisomant-treated subjects were generally either grade 1 or 2. The most frequent treatment-related AEs included injection site reactions, headache, and fatigue. Conclusions: Pegvisomant at well-tolerated s.c. doses was considerably more efficacious than octreotide in suppressing the GH axis, resulting in substantial and sustained inhibition of circulating IGF-I, IGF-II, and IGFBP-3 concentrations. These results provide evidence in favor of further testing the hypothesis that pegvisomant, through blocking the GH receptor–mediated signal transduction pathways, could be effective in treating tumors that may be GH, IGF-I, and/or IGF-II dependent, such as breast and colorectal cancer.