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New Type of Antiretroviral Agent Approved for HIV Treatment

Cheryl A. Thompson

Enfuvirtide, a peptide that inhibits the fusion of the human immunodeficiency virus (HIV) with its target, was recently approved for marketing in the United States and will be sold under the brand name Fuzeon (PDF). The fusion inhibitor will initially be distributed exclusively by a company that specializes in services for patients with chronic conditions.

According to the product's labeling, the drug is to be used as part of combination therapy to treat HIV infection in patients as young as 6 years old who are not fully responding to antiretroviral agents.

The recommended dosage for adults and children weighing at least 94 pounds is 90 mg administered twice daily by subcutaneous injection into the upper arm, the front part of the thigh, or the abdomen. For children at least 6 years old, the recommended dosage is 2 mg/kg twice daily but not more than 90 mg per dose. The product's labeling includes a table of patient-weight ranges and corresponding drug dose and injection volume. Use of the drug in children less than 6 years old is not recommended.

When prepared according to the instructions in the product's labeling, the drug solution has a pH of 9. At least one incident of a local reaction at the injection site was reported by 98 percent of the adults who participated in the two Phase III studies and received enfuvirtide. These local reactions usually consisted of mild to moderate pain, redness and hardening of the skin, and the formation of nodules or cysts.

The drug solution is prepared by reconstituting the drug powder with 1.1 mL of sterile water for injection. When properly prepared, the vial contains about 1.2 mL of a 90-mg/mL solution, although no more than 1 mL should be administered per dose. The drug powder does not immediately dissolve in water; the instructions suggest gently rolling the vial between one's hands to speed dissolution, which might otherwise take up to 45 minutes. Once reconstituted, the drug may be stored at 2–8 degrees C for no more than 24 hours but should be brought to room temperature before withdrawing the solution into a syringe.

Fuzeon will be supplied in a 30-day kit containing the following items: 60 vials of drug, 60 vials of sterile water for injection, 60 3-cc syringes for mixing the drug solution, 60 1-cc syringes for administering the doses, alcohol pads, a patient package insert (PDF), and instructions on injection.

Trimeris Inc. and Hoffmann–La Roche Inc. jointly developed enfuvirtide, with the latter taking on the responsibility for manufacture and distribution in the United States. They described the drug this morning as "the most complex pharmaceutical molecule ever manufactured on a large scale" and expected initial demand to exceed the supply.

Because of this expected supply problem, the companies decided to establish a "progressive distribution plan" for the United States.

Chronimed Inc. announced this morning that it had contracted with Roche to be the exclusive U.S. distributor of Fuzeon for the first year. The product, which is expected to be available before the end of March, will be distributed mainly by Chronimed's mail-service operation, with some support provided by the company's 27-city network of community-based specialty pharmacies known as StatScript.

Trimeris and Roche, in announcing their distribution plan today, said prescriptions for Fuzeon will be processed on a first-come, first-served basis. The enrollment and prescription form (PDF) are available online. Supplies for patients in the Veterans Affairs health system are being handled through a separate program.