T20 is cost effective for UK purchasers

One of the controversial aspects of T20 (enfuvirtide, Fuzeon), the new entry inhibitor recently approved in both the US and Europe, is its cost. At over £14,000 per year it costs more than three times that of the most expensive currently available antiretrovirals.

Prior to licensing, the cost as much as the need to take the drug by twice-daily subcutaneous injection, had the potential to limit widespread use of T20, even among patients with drugs resistant virus for whom it could effectively contribute to sustained virological suppression.

Since licensing, use of T20 has been more limited and certainly much less than predicted by Roche. In support of the treatment a cost-economics model has been developed to demonstrate that additional costs of T20 as a life-saving therapy are still well below that of many other National Health Service treatments that are routinely prescribed.

The model used estimated costs of NHS therapy and healthcare together with efficacy results from 24-week results from the TORO Phase 3 studies. Wider benefits such as increased productivity from HIV-patients using T20 were not included.

The incremental cost per year of life and cost per quality adjusted life year (QALY) gained were estimated using the formula:

C/E represents the incremental cost-effectiveness ratio and for T20+optimised background regimen (B) and optimised background alone (A), TC represents the total discounted cost of the intervention and Q represents the effectiveness measure (either life expectancy or QALY).

Projected longer life from using T20 plus optimised background therapy and reduced risk of new AIDS defining events produced cost-effectiveness per life year gained of £18,859 and per QALY gained of £23, 200.

In a sub-group analysis based on genotypic sensitivity score (GSS) for number of susceptible additional drugs used in the regimen, cost per QALY gained was £36,128, £24,094 and £14,949 for a patient with GSS score of 0, 1 and >/=2 drugs respectively.

Comment

The London Commissioners Group has already issued guidance for prescribing T20 for doctors, health trusts and patients, based on recommendations in the July 2003 BHIVA guidelines. [2]

This recommends that all patients currently receiving T20 as part of an active combination should continue to do so. Also that patients with high risk of short term disease progression with CD4 counts <50 cells/mm3 should be able to use T20, even without optimal sensitive background therapy.

In order to optimise the chance of long-term benefit, and minimise the risk of resistance, all other patients are recommended only to use T20 supported by one or two drugs to which their virus is still sensitive. Highly treatment experienced patients with multiple drug resistance who are virologically and immunologically stable with little risk of short-term disease progression, are advised to wait until they have sufficient sensitive drugs to use alongside T20, perhaps waiting until tipranavir is available.

This strategy will limit the risk of developing resistance to T20 and T1249, the pipeline successor, which can occur in as little as six months when T20 is used as virtual monotherapy.

Within the annual NHS budget, the additional costs for a limited number of people using T20 are dwarfed in comparison to the increased budget required for standard HAART and routine monitoring for the increasing number of newly diagnosed individuals.