Health and Prostate

Brand Name:  Trelstar Depot
Active Ingredient: triptorelin pamoate
Indication: Palliative treatment of advanced prostate cancer in patients in whom orchiectomy or estrogen administration is not indicated or is unacceptable
Company Name: Pharmacia & Upjohn
Availability: Approved by FDA on June 15, 2000

Introduction

In June 2000 the FDA approved Pharmacia & Upjohn’s Trelstar Depot (triptorelin pamoate for injection) for the palliative treatment of advanced prostate cancer. Triptorelin pamoate is a synthetic decapeptide agonist analogue of luteinizing hormone (LH)-releasing hormone. Trelstar Depot is administered as a dose of 3.75 mg in a single intramuscular injection given once a month.

Trelstar Depot: How It Works

Triptorelin is a potent inhibitor of gonadotropin secretion when given continuously and in therapeutic doses. Following the first administration, there is a transient surge in circulating levels of luteinizing hormone, follicle-stimulating hormone (FSH), testosterone, and estradiol. After chronic and continuous administrations, usually 2-4 weeks after initiation of therapy, a sustained decrease in luteinizing hormone and follicle-stimulating hormone secretion and marked reduction of testicular and ovarian steroidogenesis is observed. In men, a reduction of serum testosterone concentration to a level typically seen in surgically castrated men is obtained. Consequently, tissues and functions that depend on these hormones for maintenance become quiescent. These effects are usually reversible after cessation of therapy.

Trelstar Depot: Clinical Study Results

Trelstar Depot was evaluated in a randomized, active controlled trial of 277 men with advanced prostate cancer, ages 47-89 years. Patients received either Trelstar Depot or an approved GnRH agonist monthly for 9 months. The primary efficacy endpoints were both achievement of castration by day 29 and maintenance of castration from day 57 through day 253.

Castration levels of serum testosterone (no more than 1.735 nmol/L) were achieved in 91.2% of Trelstar Depot patients at day 29 and in 97.7% of patients at day 57. Maintenance of castration levels of serum testosterone from days 57-253 was observed in 96.4% of Trelstar Depot patients.

Kuhn et al compared the efficacy of Trelstar Depot to leuprolide in 67 patients with prostate cancer who were deemed not suitable for surgery. Thirty-three patients received 3.75 mg Trelstar Depot at 4-week intervals for 3 months, and 34 patients were treated with 3.75 mg subcutaneous leuprolide at the same rhythm of administration for 3 months. During treatment, prostate-specific antigen levels dropped similarly in both groups. By month 2, testosterone was less than 1.0 nmol/l in 77% and 48% of patients treated with Trelstar Depot and leuprolide, respectively. Twenty-four and 72 hours after injection, 77% of the Trelstar Depot patients and 56% of the leuprolide patients had testosterone less than 1.0 nmol/l.

Trelstar Depot: What the Patient Should Know

Like other drugs in its class, Trelstar Depot causes a transient increase in serum testosterone levels, resulting in a worsening of signs and symptoms of prostate cancer during the first weeks of treatment. Patients may experience bone pain, neuropathy, hematuria, or urethral or bladder outlet obstruction. Cases of spinal cord compression, which may contribute to paralysis with or without fatal complications, have been reported with LNRH agonists. Patients with metastatic vertebral lesions or urinary obstruction should be closely observed during the first few weeks of treatment with Trelstar Depot.

The most commonly observed side effect in patients receiving Trelstar Depot is hot flushes.

Hyperprolactinemic drugs should not be prescribed concomitantly with Trelstar Depot because hyperprolactinemia reduces the number of pituitary GnRH receptors.