Protein Design Labs is discontinuing development of daclizumab as a treatment for ulcerative colitis following the monoclonal antibody's failure to show efficacy in a Phase II study.

"The primary efficacy endpoint in the study, the proportion of patients who achieved remission at week eight, did not meet statistical significance at either of the dose levels tested," the firm reported May 16.

"Top priority" for development of the drug is now chronic, persistent asthma. "Our current plan is to follow the positive Phase II data in this setting reported earlier this year with a follow-on study" to be initiated "by the first quarter of 2005," PDL said.

The firm also plans to begin a follow-on study in multiple sclerosis, its "second priority for daclizumab," by Q1 2005.

Colitis is at least the second potential indication for daclizumab that PDL has discontinued following poor Phase II efficacy results. In March 2002, the firm announced that it ceased development for maintenance therapy in moderate to severe psoriasis after the drug did not demonstrate a prolonged time to recurrence of psoriasis.

Daclizumab, approved in December 1997 for the prophylaxis of organ rejection in patients receiving renal transplants, is marketed by licensee Roche as Zenapax . In September 2003, PDL announced that it reacquired the rights to all indications other than organ transplant from Roche for $80 mil. PDL also gained an option for transplantation indications, effective in 2007.

Zenapax labeling was revised in August 2003 to add a warning about the potential for increased mortality when used as part of an immunosuppressive regimen including cyclosporine, mycophenolate mofetil and corticosteroids. The warning was based on results from a study in 434 cardiac transplant patients.

- Janet Coleman

Protein Design Labs Discontinues Daclizumab Development For Colitis; Asthma Is “Top Priority” Indication

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