Viadur: Treatment of Advanced Prostate Cancer
Brand Name: Viadur
Active Ingredient: leuprolide acetate implant
Indication: Palliative treatment of advanced prostate cancer
Company Name: ALZA Corporation
Availability: Approved by FDA on March 3, 2000
Introduction
Testosterone suppression or hormonal therapy is commonly used for the palliative treatment of patients with advanced prostate cancer. Reduction of testosterone levels results in a therapeutic response in some patients, including reduced or halted growth of prostate cancer cells and relief of symptoms such as pain and urinary difficulties. The most common means of achieving such as decrease has been via frequent injections with leuprolide.
ALZA Corporation is now producing Viadur, an implant that delivers leuprolide steadily for up to one year. The FDA approved Viadur on March 3 2000. Viadur is implanted in the patient’s inner upper arm once a year in his doctor’s office, and provides continuous 12-month testosterone suppression. After the first year of therapy, the implant is removed and a new one inserted.
Viadur: How It Works
Viadur is a small titanium implant filled with 72 mg of leuprolide acetate (65 mg leuprolide free base), an agent in the class of drugs known as luteinizing hormone-releasing agonists. Leuprolide acetate acts as a potent inhibitor of gonadotropin secretion, resulting in a reduction in the amount of testosterone produced by the body.
ALZA’s DUROS implants are miniature titanium cylinders designed to provide continuous, osmotically-driven delivery of leuprolide for up to one year. Titanium, a material with excellent tolerability to human tissue, has long been used in implantable medical devices. The cylinder protects the drug from degradation in the body.
Viadur: Clinical Study Results
The efficacy of Viadur was established in two open-label, multicenter clinical studies of 131 patients with advanced prostate cancer who were treated with Viadur and evaluated for up to two years. Two-thirds of the patients had stage C or less advanced disease. Serum testosterone levels were evaluated in patients who had received either one or two implants. Following the initial insertion of the implant, mean serum testosterone levels increased from 422 ng/dl at baseline to 690 ng/dl on day 3, and then decreased to below baseline by the second week. Serum testosterone decreased below the 50 ng/dl castrate threshold by week 4 in 99% of patients. Once serum testosterone suppression was achieved, it remained below the castrate threshold for the duration of the treatment phase.
Most patients (118) had a new implant inserted for a second year of therapy following the removal of the first implant after one year. No patients experienced a clinically significant increase in serum testosterone following removal of the first implant and insertion of the second.
Serum prostate-specific antigen (PSA) was monitored as a secondary endpoint in the clinical studies of Viadur. Serum prostate-specific antigen decreased in all patients after they began treatment with Viadur. At six months, prostate-specific antigen concentrations decreased from baseline by at least 90% in 74.2% of 97 evaluable patients.
Viadur: What the Patient Should Know
The most common side effects associated with Viadur were those expected with other drugs in its class, including vasodilation (67.9%), asthenia (7.6%), gynecomastia (6.9%), depression (5.3%), and sweating (5.3%). Local reactions at the implantation site included bruising (34.8%) and burning (5.6%). Most implantation site reactions began and resolved in the first two weeks. Patients should avoid heavy lifting and physical activity for 48 hours after the implantation.
Patients may experience a worsening of symptoms when serum testosterone increases at the beginning of treatment. Such symptoms may include bone pain, neuropathy, hematuria, or ureteral or bladder outlet obstruction.