General Information

Saizen (somatropin) injection is a recombinant human growth hormone.

Saizen is specifically indicated for the treatment of children with growth failure due to growth hormone deficiency (GHD) and adults with either adult onset or childhood onset GHD. 

Saizen is supplied as an injection for subcutaneous use. Injection sites should always be rotated to avoid lipoatrophy. The recommended dosing is as follows:

Pediatric GHD:

0.18 mg/kg/week, divided into equal doses given either on 3 alternate days, 6 times per week or daily

Adult GHD:

Either a non-weight based or a weight based dosing regimen may be followed, with doses adjusted based on treatment response and IGF-1 concentrations

• Non-weight-based dosing: A starting dose of approximately 0.2 mg/day (range, 0.15-0.30 mg/day) may be used without consideration of body weight, and increased gradually every 1 to 2 months by increments of approximately 0.1 to 0.2 mg/day 
• Weight-based dosing: The recommended initial dose is not more than 0.005 mg/kg/day; the dose may be increased as tolerated to not more than 0.01 mg/kg/day after 4 weeks

Mechanism of Action

Somatropin (as well as endogenous growth hormone) binds to dimeric growth hormone receptors located within the cell membranes of target tissue cells resulting in intracellular signal transduction and a host of pharmacodynamic effects. Some of these pharmacodynamic effects are primarily mediated by IGF-1 produced in the liver and also locally (e.g., skeletal growth, protein synthesis), while others are primarily a consequence of the direct effects of somatropin (e.g., lipolysis).

Side Effects

Adverse effects associated with the use of Saizen may include, but are not limited to, the following:

• injection site reactions (such as pain, numbness, redness, and swelling)
• fluid retention
• peripheral edema
• arthralgia
• myalgia
• paresthesia
• headache

Clinical Trial Results

Adult Growth Hormone Deficiency (GHD)

A multicenter, randomized, double-blind, placebo-controlled clinical trial was conducted in 115 adults with growth hormone deficiency comparing the effects of Saizen and placebo on body composition. Patients in the active treatment arm were treated with Saizen at an initial dose of 0.005 mg/kg/day for one month which was increased to 0.01 mg/kg/day if tolerated for the remaining five months of the study. The primary endpoint was the change from baseline in lean body mass measured by dual energy X-ray absorptiometry (DXA) after 6 months. Treatment with Saizen produced significant (p<0.001) increases from baseline in LBM compared to placebo.