Interneuron Pharmaceuticals Inc. said Monday that it receivedits first-ever orphan drug designation, covering L-threosine asa proposed treatment for a rare neurological disease.

Interneuron of Lexington, Mass., said it aims to start by late1993 clinical trials of L-threonine to treat familial SpasticParaparesis, of which there are believed to be more than 5,000cases in the United States. Symptoms include rigid and spasticmovements that affect the ability to walk smoothly.

L-threosine is a natural amino acid that has been shown inanimal studies to be a precursor of glycine, a neurotransmitterfound in the spinal fluid and believed related to musclemovement.

In a physician-directed clinical trial involving 18 individualsat Massachusetts General Hospital, an oral form of L-threosinewas found to significantly reduce signs of spasticity inpatients with the disease. The findings of the FDA-sponsoredstudy conducted John Growden of MGH were reported last yearin the journal Clinical Neuropharmacology, according to thecompany.

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