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Biogen Idec Inc. Q2 2010 Earnings Call Transcript, July 20, 2010

I’ll be providing an update on the pipeline a bit later, but let me begin with our TYSABRI risk stratification efforts. As I’ve mentioned before, one of our goals has been to provide prescribers with tools they can identify individuals who might be at risk for PML when taking TYSABRI.

We began with a premise that only patients who’ve been affected with the JC virus are at risk of developing PML. Our hypothesis that our two-step ELISA assay that detects antibodies against JCV will be informative in estimating the risk of developing PML for patients receiving TYSABRI.

Based on testing, nearly 2000 MS patients from STRATA and TYGRIS studies, we find that approximately 50% of MS patients are still positive with our assay. We currently estimate that our assay has a false negative rate of about 2.5%. When we tested archived samples that were available from 17 patients who developed PML while on TYSABRI, all 17 tested positive with our assay.

These samples have been collected 16 months to a 180 months prior to the onset of PML for various reasons, including participation in clinical studies and national registries. With antibody status, we’re not a risk factor for developing PML, one would have expected that roughly half of these 17 patients would have been antibody positive. So we believe the finding all 17 to be positive was extremely unlikely to be due to chance.

Encouraged by these preliminary data, we have initiated two studies to test our hypothesis at the anti-JCV test that we have developed will be helpful to clinicians as risk stratification tools. These studies are STRATIFY 1 and STRATIFY 2, both of which are being conducted in the United States.

As George mentioned, STRATIFY 1 is now fully enrolled and STRATIFY 2 is off to a great start with more than 700 patients enrolled at over 90 sites around the United States. This study which will enroll a total of 8000 to 24000 patients will provide an estimate of the risk of PML in TYSABRI patients test negative in our assay. Our hypothesis is that those who test negative in our assay will have a lower risk of PML than those who test positive.

We plan to show preliminary data from STRATIFY 1 at the ECTRIMS meeting in October of this year. Also, our manuscript on the anti-JCV assay methodology and its potential use as a risk stratification tool has been accepted for publication in the Annals of Neurology and will be coming out in approximately six weeks.

We also want to update you on a change to the US TYSABRI label that we along with our partner Elan have just made. After a thorough evaluation of our post-marketing surveillance data, we have concluded that the risk of PML is increased in patients have been treated with an immunosuppressant prior to receiving TYSABRI.

This increased risk appears to be independent of treatment duration and there was a broad range in the time interval between the discontinuation of the prior immunosuppressant and the TYSABRI initiation. Recall that the original label had warned that patients receiving TYSABRI should not be treated with concomitant immunosuppressants. We have added an additional warning about the prior use of these drugs to the existing warning.

Based on data from the TYGRIS observational study, only 13% of US patients and 24% of ex-US patients have had prior immunosuppressant use, whereas about half of the PML cases had previously received these drugs. Thus, there was a disproportionately higher representation of prior immunosuppressant use in the PML cases. The new label changes were posted online as of July 15th. Overall, we continue to learn more about factors associated with the risk of PML and we’re looking forward to providing data to the MS community to help with their decision-making for treatment choices.