Protein Design Labs announced Monday that it has started thethird clinical trial of the Smart Anti-Tac humanized antibody.

The multiple-dose study will be conducted in North Americaand Europe in graft vs. host disease.

The Mountain View, Calif., company's Smart Anti-Tac isintended to suppress the immune system by blocking bindingof Interleuken 2 to activated T cells. Only 5 percent to 10percent of all T cells are activated by the presence of foreigncells to take part in the immune response that culminates ingraft rejection. Current immunosuppressive drugs suppressmost or all T cells, leaving the body more susceptible toinfection and certain malignancies.

In a Phase I single-dose study for steroid-resistant acute GvHD,SMART Anti-Tac did not produce appreciable side effects inany of 20 patients, did not elicit a human anti-mouse antibodyresponse, and showed preliminary indications of activity.

Hoffmann-La Roche Inc. has exclusive worldwide rights tomanufacture and market SMART Anti-Tac and is responsiblefor the clinical trials. Future studies will include prevention andtreatment of organ transplant rejection and treatment ofcertain autoimmune diseases and blood cancers.

PDL has retained rights to commercialize the company'sRecombinant Anti-Tac immunotoxin. In January, Roche decidednot to exercise an option it had been granted to acquire anexclusive license to this molecule, which genetically combines abacterial toxin and the Anti-Tac antibody.

Protein Design Labs' stock (NASDAQ:PDLI) was up 75 cents ashare on Monday, closing at $9.63.

-- Nancy Garcia Associate Editor

(c) 1997 American Health Consultants. All rights reserved.

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