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FDA Approves Prostate Cancer Drug

Cheryl A. Thompson

Praecis Pharmaceuticals Inc. and the Food and Drug Administration (FDA) announced yesterday that abarelix, also known as Plenaxis, had been approved for use in certain men with advanced prostate cancer and will be distributed to hospital pharmacies and physicians enrolled in a special program.

Abarelix is a synthetic peptide that blocks receptors for gonadotropin-releasing hormone (GnRH) in the pituitary. By blocking GnRH at its receptors, abarelix suppresses the pituitary's production of two hormones responsible for the secretion of testosterone by the testes. Reduction or elimination of testosterone secretion by the testes is one method of treating prostate cancer.

According to the product's labeling, the drug is for use in men with advanced symptomatic prostate cancer who cannot receive therapy with a luteinizing hormone-releasing hormone agonist and refuse surgical castration. Patients must also have at least one of the following conditions: risk of neurologic compromise due to metastases; obstruction of the ureter or urinary bladder outlet due to metastases or local advancement by the cancer; or severe bone pain due to metastases in the skeleton "persisting on narcotic analgesia."

Abarelix will treat the symptoms of the cancer but not cure the disease, the company said.

Because a systemic allergic reaction developed immediately in 3.7 percent of the 81 men with advanced, symptomatic prostate cancer who received abarelix during the clinical study, FDA required that Praecis develop a risk management program to ensure the drug is used only in patients whose condition meets the criteria specified in the labeling.

Praecis President William K. Heiden credited ASHP's Gary Stein and other staff members for providing "very helpful commentary" that the company used in deciding how hospital pharmacies would obtain the drug for their patients.

To obtain a supply of abarelix, a hospital pharmacy or physician must first enroll in the Plenaxis User Safety Program, or PLUS Program.

A pharmacist at the hospital pharmacy must complete the "Hospital Pharmacy's Acceptance of Responsibilities" form and submit it to Praecis. Heiden said the pharmacist does not have to be the pharmacy director but does have to be someone "who will take responsibility" for ensuring that the pharmacy adheres to the risk management program. Once accepted into the PLUS Program, he said, the pharmacy may order abarelix from one of the "select distributors."

Praecis has not finalized its list of abarelix distributors, Heiden said.

By signing the enrollment form, the pharmacist agrees that the pharmacy's staff will dispense abarelix only in response to medication orders from prescribers listed in the Plenaxis Prescribers' Registry. Confirmation of a prescriber's inclusion in the registry is made via an interactive voice-response system at 866-753-6294.

Heiden said that a pharmacist's acceptance of responsibilities for the PLUS Program "does not entitle Praecis to come in and audit" the pharmacy's patient records. But FDA personnel would have the right to examine the records, he said.

Praecis, Heiden said, agreed with FDA to conduct a study in which company personnel would examine the abarelix log—a list of physician names and confirmation numbers matched with every abarelix vial dispensed by the pharmacy—at volunteer hospital pharmacies.

Heiden emphasized that hospital pharmacists are not responsible for confirming that a patient meets the criteria for abarelix therapy.

Praecis will start providing inservice educational sessions for pharmacies in January, he said. A session can be scheduled by calling 866-753-6294. The drug will not be sold to community pharmacies.

The use of abarelix is contraindicated in patients with a known hypersensitivity to the peptide or carboxymethylcellulose, a component of the product.

During the clinical study of abarelix, the most commonly reported adverse reactions to therapy with the drug were hot flushes (79 percent), sleep disturbances (44 percent), pain (31 percent), and breast enlargement (30 percent). Most of these reactions resulted from the drug's intended action—decreasing the secretion of testosterone.

The product's labeling instructs health care providers to monitor patients for at least 30 minutes after each injection of abarelix. An allergic reaction involving hypotension or syncope should be treated with supportive measures, such as elevating the legs and administering oxygen, intravenous fluids, an antihistamine, a corticosteroid, and epinephrine.

According to the product's labeling, the dosage of abarelix is 100 mg administered by intramuscular injection in the buttock on days 1, 15, 29 and every four weeks thereafter.

Plenaxis will be supplied in single-dose preservative-free vials of sterile powder containing 133 mg of abarelix. Reconstitution of the powder with 2.2 mL of 0.9 percent sodium chloride injection yields a 50-mg/mL solution that should be administered within one hour. Each Plenaxis package will also contain a single-use 10-mL vial of the diluent, a 3-mL syringe with a needle, and a "Safety Glide" needle for use in administering the dose.

Heiden said the product will be available to pharmacies early in the first quarter of 2004.