The Pharmaceutical Journal
Vol 270 No 7253 p821
14 June 2003

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Fusion inhibition "major but costly step forward"

"A major but costly step forward" in HIV treatment is how American physicians welcome the first fusion inhibitor, enfuvirtide, expected to be launched soon in the United Kingdom for use in combination therapy of HIV/AIDS (PJ, May 10, p 642).

The drug, made by Roche and Trimeris, prevents the HIV virus binding with the surface of T-cells.

Doctors writing in the New England Journal of Medicine highlight the cost of the new treatment, which is likely to be $20,000 (£12,100) per year — more than twice that of the next most expensive antiretroviral agent. The high cost is attributed to a complex manufacturing process involving 106 steps, compared with eight to 12 steps for other HIV medicines. Only 15,000 patients will be able to receive the drug worldwide during the next 12 months.

"High cost and limited availability will limit the use of this drug to a small subgroup of the 5 per cent of the world's HIV infected persons who live in industrialised nations," say Karen Tashima and Charles Carpenter of Miriam Hospital, Rhode Island.

Roche says that it will undertake to ensure the widest possible access to enfuvirtide for patients with drug-resistant HIV.

The authors of the NEJM editorial warn that if other drugs in the patient's antiviral regimen are not effective, viral resistance to enfuvirtide develops rapidly. However, mutations conferring resistance to the new agent do not overlap with those that confer resistance to protease inhibitors or reverse-transcriptase inhibitors. They also highlight potential side effects, particularly an increased frequency of pneumonia, the reason for which is not known. Injection site reactions occurred in almost all patients in trials but less than 3 per cent withdrew from studies because of these effects.

The Rhode Island doctors welcome the efficacy of the new agent which, they believe, could be useful in patients whose options are "severely constrained by extensive resistance mutations against the available antiretroviral drugs".

Robert Steinbrook, an NEJM correspondent, comments that combination of enfuvirtide with other antiviral agents and other medicines could lead to annual drug costs of $30,000 per patient.

He notes that the success of combination therapies for HIV infection increases the financial challenge of paying for them (2003;348:2171 and 2249).