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12:00 AM
 | 
Aug 17, 2009
 |  BioCentury  |  Regulation

DaT's good enough

By backing DaTSCAN ioflupane I123 injection from GE Healthcare last week, an FDA panel indicated that a molecular imaging agent that allows physicians to see abnormal changes in the brain has clinical value, and that the hurdle for such agents should be different than the hurdle for those seeking claims for the diagnosis of specific diseases.

FDA's Peripheral and Central Nervous System Drugs Advisory Committee voted 11-2, with one abstention, that the risk-benefit profile of DaTSCAN supports its use as an adjunct to clinical assessment for evaluation of patients with symptoms or signs suggestive of dopaminergic neurodegeneration.

The panel largely shrugged off FDA's concerns about GE's Phase III program and instead expressed comfort with the totality of the preclinical and clinical evidence, including postmarketing experience in Europe.

The data

DaTSCAN is designed to allow visualization of the striatum using single photon emission computed tomography (SPECT) to detect abnormal distribution of dopaminergic neurons. The product consists of an iobenguane I123 radiolabel attached to ioflupane, an analog of cocaine that binds to the dopamine transported (DaT) neuronal membrane protein located on the surface of dopaminergic neurons. DaT proteins assist in the reuptake of dopamine into neurons.

In Europe, where it has been approved since 2000, DaTSCAN's label states that the agent can help differentiate between Parkinsonian syndromes and essential tremor, or between probable dementia with Lewy bodies (DLB) and Alzheimer's disease. But the label notes it cannot discriminate between dementia related to Parkinson's disease (PD) and DLB.

Parkinsonian syndromes and DLB are associated with the loss of functional dopaminergic neurons. Patients presenting with essential tremor or AD, on the other hand, may display many of the same symptoms as Parkinson's or DLB, but neither of these conditions is characterized by a dopaminergic deficit.

There is no other marketed agent that can make this distinction.

The NDA submission was supported by data from the same three Phase III trials used for European approval, although the proposed indication in the U.S. is focused on detecting neurodegeneration rather than differentiating between specific diseases. The NDA seeks approval of DaTSCAN to detect the loss of functional nigrostriatal dopaminergic neurons by SPECT imaging in patients presenting with symptoms or signs suggestive of dopaminergic neurodegeneration.

David Brooks, a neurology professor at Imperial College London and an industry presenter, told the panel that DaTSCAN images are read based largely on anatomical appearance of the striata, which show up...

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