Serostim® [somatropin (rDNA origin) for injection] is an anabolic and anticatabolic agent which exerts its influence by interacting with specific receptors on a variety of cell types including myocytes, hepatocytes, adipocytes, lymphocytes, and hematopoietic cells. Some, but not all of its effects, are mediated by insulin-like growth factor-I (IGF-I).

Human immunodeficiency virus (HIV)-associated wasting or cachexia, which commonly involves involuntary loss of lean body mass or body weight, is a metabolic disorder characterized by abnormalities of intermediary metabolism resulting in weight loss, inappropriate depletion of lean body mass (LBM), and paradoxical preservation of body fat. LBM includes primarily skeletal muscle, organ tissue, blood and blood constituents, and both intracellular and extracellular water. Depletion of LBM results in muscle weakness, organ failure, and death. Unlike nutritional intervention for HIV-associated wasting, in which supplemental calories are converted predominantly to body fat, Serostim® treatment resulted in a significant increase in LBM and a decrease in fat mass with a significant increase in body weight due to the dominant effect of LBM gain.

HIV-associated adipose redistribution syndrome (HARS) is characterized by abnormal accumulation of trunk fat, including visceral adipose tissue (VAT), in patients infected with HIV/acquired immune deficiency disorder (AIDS), the vast majority of whom have been treated with highly active antiretroviral therapy (HAART). VAT is comprised of the deep fat in the abdomen in the omental-mesenteric and retroperitoneal compartments. HARS, a subset of HIV lipodystrophy, is more specifically defined as maldistribution of body fat characterized by central fat accumulation (lipohypertrophy) with or without lipoatrophy (subcutaneous fat depletion primarily in the face and limbs). In HARS patients, fat may additionally accumulate in the upper body subcutaneous area such as the dorsocervical area (i.e., "buffalo hump"). These changes may be accompanied by metabolic disturbances including insulin resistance, glucose intolerance, and dyslipidemia, as well as belly image distress. Initial 12-week treatment with Serostim® resulted in decreases in VAT, trunk fat, and patient-reported belly appearance distress (see CLINICAL STUDIES). The clinical significance of these changes with respect to improved cardiovascular risk profile or compliance with HAART has not been studied.

Effects on Protein<, Lipid, and Carbohydrate Metabolism

A one-week study in 6 patients with HIV-associated wasting has shown that treatment with Serostim® 0.1 mg/kg/day improved nitrogen balance, increased protein-sparing lipid oxidation, and had little effect on overall carbohydrate metabolism.

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