Tysabri Side Effects and Uses

Tysabri
side effects, toxicity, safety, new approvals and uses
zhion JUNE 13, 2007

Tysabri
The Food and Drug Administration (FDA) approved an application for
resumed marketing of Tysabri (natalizumab) subject to a special
restricted distribution program. Tysabri is a monoclonal antibody used
to treat patients with relapsing forms of multiple sclerosis (MS) to
reduce the frequency of exacerbations (flare-ups). Tysabri is indicated
for use as monotherapy, because FDA doesn't know enough about
how its use with other immune modifying drugs could impact risk. It is
also meant for patients who have not responded adequately to, or
cannot tolerate, other treatments for multiple sclerosi.

Tysabri was initially approved by the FDA in November 2004, but was
withdrawn by the manufacturer, Biogen-Idec, in February 2005, after
three patients in the drug's clinical trials developed progressive
multifocal leukoencephalopathy (PML), a serious and rare viral
infection of the brain. Two of the cases were fatal. Based on this
information, FDA put clinical trials of the drug on hold in February
2005. FDA allowed a clinical trial of Tysabri to resume in February
2006, following a re-examination of the patients who had participated
in the previous clinical trials, confirming that there were no additional
cases of PML.

To decrease the possibility of patients developing PML in the future,
while also making Tysabri available to appropriate MS patients, FDA
consulted in March 2006 with its Peripheral and Central Nervous
Systems Drugs Advisory Committee. The Advisory Committee
recommended a risk-minimization program with mandatory patient
registration and periodic follow-up to identify as early as possible any
cases of PML that may occur, and to try to determine the reason the
infection occurs. In response, Biogen-Idec, submitted to FDA a Risk
Management Plan, called the TOUCH Prescribing Program, to help
ensure safe use of the product.

Following a thorough review of Biogen-Idec's Risk Management Plan
and proposed changes to its original marketing application, FDA
determined that Tysabri can be made available under the TOUCH
Program with the following main features:

* The drug will only be prescribed, distributed, and infused by
prescribers, infusion centers, and pharmacies registered with the
program.
* Tysabri will only be administered to patients who are enrolled in the
program.
* Prior to initiating the therapy, health care professionals are to obtain
the patient's Magnetic Resonance Imaging (MRI) scan to help
differentiate potential future multiple sclerosis symptoms from PML.
* Patients on Tysabri are to be evaluated at 3 and 6 months after the
first infusion and every 6 months after that, and their status will be
reported regularly to Biogen Idec.

Biogen Idec is the manufacturer and Elan the distributor for Tysabri.

Natalizumab (marketed as Tysabri)

What are the risks, side effects, toxicity of Tysabri?

Tysabri increases the chance of patients getting a rare brain infection
that usually causes death or severe disability. This infection is called
progressive multifocal leukoencephalopathy (PML). Multifocal
leukoencephalopathy usually happens in people with weakened
immune systems.

No one can predict who will get progressive multifocal leukoencephalopathy .
There is no known treatment, prevention, or cure for progressive multifocal
leukoencephalopathy .

A patient's chance of getting progressive multifocal leukoencephalopathy may be
higher if he or she is also being treated with other medicines that can weaken the
immune system, including other MS treatments.

Even if Tysabri is used alone to treat MS, it is not known if the chance of getting
multifocal leukoencephalopathy will be lower. It is also not known if treatment for
a long period of time with Tysabri can increase the chance of getting progressive
multifocal leukoencephalopathy .

Other serious side effects include allergic reactions, which usually occur within 2
hours of the infusion, but can happen at any time after receiving Tysabri.

Tysabri may also increase the chance of getting an unusual or serious infection.

How can consumers get the product?

Tysabri is available only through a Risk Management Plan, called the
TOUCH Prescribing Program. In order to receive Tysabri, patients
must talk to their doctor and understand the risks and benefits of
Tysabri and agree to all of the instructions in the TOUCH Prescribing
Program.

What are the main features of the Risk Management Plan?

The drug will only be prescribed, distributed, and infused by
prescribers, infusion centers and pharmacies registered with the
program.

Tysabri will only be administered to patients who are enrolled in the
program.

Prior to initiating the therapy, health care professionals are to obtain
the patientÂ’s Magnetic Resonance Imaging (MRI) scan to help
differentiate potential future multiple sclerosis symptoms from PML.

Patients on Tysabri are to be evaluated 3 and 6 months after the first
infusion and every 6 months after that, and their status will be reported
regularly to Biogen Idec.

Who will manage the program?

Biogen Idec Inc., the company that manufactures Tysabri, and Elan
Pharmaceticals Inc., the company that distributes Tysabri, will manage
the program.

How will FDA evaluate the program?

Biogen Idec and Elan Pharmaceuticals will be monitoring the conduct
of the program continuously. Periodically they will submit reports to
FDA about the functioning of the program. Biogen Idec and Elan
Pharmaceuticals will also submit to FDA proposals for any changes in
the program to help ensure safe use of the product.

SOURCE FDA Approves Resumed Marketing of Tysabri Under a Special Distribution
Program FDA News, Questions and Answers June 5, 2006