The "heartbreak of psoriasis" is a phrase that might as fittingly be extended to companies developing treatments for the disease as to patients suffering from it.

While perhaps not as difficult as sepsis and wound healing are proving to be, psoriasis isn't well understood and there are no good animal models for it. Any product brought into the clinic is more of a gamble than are products for diseases with known etiologies and good animal data.

"The one big problem with psoriasis is there's no animal model, so the predictability is poor," said David Ward, vice president of clinical development at Sphinx Pharmaceuticals Corp., which recently reported disappointing Phase II data on its psoriasis drug, Kynac. As a result, companies either use models for another dermatological disorder, contact dermatitis, or rely on in vitro studies.


"Psoriasis is a lousy disorder," said Gregory Brown, an analyst at Vector Securities International Inc. "It's an extremely tough target. It's a protean disease that has a lot of different forms of behavior and I don't think we understand the basic biology."