Wednesday, February 08, 2006

Lundbeck - "evergreen" Lexapro fails to lift the mood

Poor Danish drugmaker Lundbeck. They have slashed their financial targets for 2006 on the back of weaker than expected sales of Lexapro, an antidepressant, in the USA.

Shares in the company closed down more than 8% at 133.25 kroner yesterday, after issuing a statement that the US licensee for Lexapro (escitalopram), Forest Laboratories, had reduced its inventory levels for the product, indicating slower than expected sales.

Escitalopram is one of the isomeric forms of the drug citalopram. The manufacturers conveniently found that citalopram actually consisted of two versions of the same molecule, with one apparently more active than the other. They refined this ‘more active’ version into a new medicine just before the old drug came off patent, a process commonly known as "evergreening".

The promotional material supporting escitalopram includes a trial that put it head-to-head with citalopram in patients with major depression (i.e. not routine primary care patients). The trial looked at reduction in MADRAS Depression score (a validated scale).

At the end of the trial period of 8 weeks escitalopram was statistically better than citalopram. However, on closer examination of the paper the statistical difference may not equate to a clinical difference. The difference in MADRAS scores between the two drugs was 2 points with confidence intervals on each estimate of approximately 12.

Clinically a difference of 2 points measured on a scale of 60 is not going to be noticeable. Furthermore, although the paper demonstrates statistical difference the confidence intervals on the point estimates overlap massively and therefore the findings are not conclusive.

So, could this just be a case of evergreening? If so, it looks like it's not going to work.

Hat tip: Prescribing Advice for GPs