- In a clinical trial for Xenoport's XP23829, being developed for treatment of psoriasis, 22% to 40% of treated patients experienced diarrhea, compared with 15% of placebo-treated patients.
- Psoriasis is a difficult-to-treat autoimmune disease that affects 2% to 2.6% of the population in the U.S. It is characterized by itchy or sore patches of thick, red skin, with silvery scales.
- Compared with Celgene's Otezla (apremilast), XP23829 has a poor profile.
The therapeutic class for treating psoriasis is becoming crowded with new entrants, including not only Celgene's Otezla, which was approved last year, but also a recently approved injectable from Novartis---Cosentyx. In addition, Eli Lilly is developing Ixekizumab, an injectable.
Xenoport's candidate has shown efficacy in treating the symptoms of psoriasis, with both 400-mg and 800-mg doses reducung the severity of psoriasis in clinical trials. One positive feature of XP23829 is that it's an oral treatment; however, that positive feature is overshadowed by the high rate of gastrointestinal side effects in clinical trials, especially diarrhea.
At this point, it's not clear if a dose adjustment is in order, or if there are other ways to mitigate the severe GI effects of XP23829. But Xenoport's shares have fallen sharply (nearly 10%) since the adverse event news came out.