Long Acting Testosterone Undecanoate Therapy in Men With Hypogonadism: Results of a Pharmacokinetic Clinical Study

Purpose: We determined the pharmacokinetics and safety of 750 mg long acting testosterone undecanoate given intramuscularly at 0, 4 and 14 weeks to men with hypogonadism. Materials and Methods: A 24-week, single arm, open label, multicenter trial in 130 hypogonadal men 18 years or older who were screened for serum total testosterone less than 300 ng/dl was performed at 31 research sites in the United States between March and November 2007. Testosterone undecanoate (750 mg) was administered at baseline, and at weeks 4 and 14. Serum testosterone samples were collected on days 4, 7, 11, 14, 21, 28, 42, 56 and 70 following injection 3. Safety was assessed, eg biochemical markers and adverse events, secondary to testosterone undecanoate treatment. Results: Of the 130 patients 116 with a mean +/- SE age of 54.2 +/- 0.90 years completed the 24-week trial. Following the week 14 injection mean +/- SD average serum testosterone was 494.9 +/- 141.46 ng/dl during the 70-day dosing interval and mean +/- SD maximum serum testosterone was 890.6 +/- 345.11 ng/dl with a mean concentration within the young healthy adult male range (300 to 1,000 ng/dl) in 94% of patients and a mean maximum concentration of below 1,500 ng/dl in 92%. Mean +/- SE hematocrit and hemoglobin increased from baseline to week 24 (43.3% +/- 0.32% to 45.7% +/- 0.35% and 14.6 +/- 0.11 to 15.5 +/- 0.13 gm/dl, respectively). Mean +/- SE prostate specific antigen increased from baseline to 24 weeks (1.0 +/- 0.08 to 1.3 +/- 0.10 ng/ml). No prostate cancer or gynecomastia was observed during this 24-week study. Conclusions: This 24-week clinical study demonstrated that 750 mg testosterone undecanoate depot injection administered intramuscularly at 0, 4 and 14 weeks achieves serum testosterone levels in the normal range during a 10-week dosing interval.