Alseres Pharmaceuticals is developing an 123I-labelled imaging agent, Altropane®, as a diagnostic aid in Parkinson's disease and other movement disorders. Altropane is a molecular-imaging agent that specifically binds to the dopamine transporter (DAT) protein found on the surface of dopamine-producing neurons, making it visible during SPECT imaging. Since most forms of Parkinsonian Syndromes result in a decreased number of dopamine-producing cells, it would be expected that these patients also have fewer DATs than do patients without PS. Thus, it is believed that altropane used in conjunction with SPECT imaging could be a useful test to distinguish Parkinsonian Syndrome tremors from non-Parkinsonian tremor: non-Parkinsonian patients would have more altropane-binding visible in the SPECT image, while Parkinsonian patients would have less. The E isomer of (123)I-2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-(1-iodoprop-1-en-3-yl)nortropane (Altropane(R)) shows high affinity (IC(50) = 6.62 +/- 0.78 nmol) and selectivity (DA/5-HT = 25) for DAT sites in the striatum. Altropane is presently in Phase III clinical development for the diagnosis of Parkinson's disease.