San Diego-based cAMPfield Therapeutics reported that prifemilast (HY1999), a once-daily preferential PDE4B inhibitor, achieved superiority over Amgen's Otezla (apremilast), an approved oral PDE4 inhibitor, on both co-primary endpoints in a head-to-head Phase III trial in adults with moderate-to-severe plaque psoriasis. Results from this study, a separate placebo-controlled Phase III trial, and an earlier Phase II study were presented at the 2026 Fall Clinical Dermatology Conference. All three trials were conducted in China by cAMPfield's partner, Newsoara BioPharma.
In the 607-participant trial, prifemilast 20 mg once daily achieved a PASI 75 response rate of 64.6% versus 35.3% for apremilast 30 mg twice daily at Week 16, and a rate of clear or almost clear skin (sPGA 0/1) of 55.6% versus 31.3% (both P<0.0001). Serious adverse events occurred in 4.0% of prifemilast-treated patients versus 2.5% on apremilast; discontinuations due to adverse events were 2.0% versus 1.5%, with the company describing both as low and similar between arms.
In a separate placebo-controlled Phase III trial involving more than 500 participants, prifemilast demonstrated superior efficacy over placebo, with responses observed as early as Week 2 and maintained through Week 52. An earlier Phase II dose-ranging trial involving 123 participants showed that 67.7% of patients receiving prifemilast 20 mg achieved clear or almost clear skin at Week 12, compared with 6.7% on placebo. Across the development program, more than 1,000 participants have received prifemilast, including over 250 treated for 52 weeks.