Pfizer has presented data which demonstrates that a high dose of tofacitinib, already marketed as Xeljanz for rheumatoid arthritis, appears to be an effective treatment for psoriasis, but a lower dose seems to be less so.

The drugs giant announced top-line results from the first two of five Phase III trials of tofacitinib, its oral Janus kinase (JAK) inhibitor as a treatment of adults with moderate-to-severe chronic plaque psoriasis. The first study compared tofacitinib 5mg and 10mg twice-daily with a 50mg twice-weekly dose of Pfizer's own blockbuster Enbrel (etanercept) and showed that the former met the primary endpoint of non-inferiority to high-dose Enbrel at the 10mg BID dose, but not at the 5mg BID dose.

The second trial, a 56-week study, demonstrated that a greater proportion of patients continuing tofacitinib treatment maintained their response during the treatment withdrawal phase compared to patients who switched to placebo. Additionally, among patients who lost an adequate response, many were able to recapture it upon retreatment with the Pfizer drug.

Steven Romano, head of the Medicines Development Group for Pfizer Specialty Care, said the studies "provide information that is consistent with our expectations based on the Phase II data in psoriasis". He added that "we look forward to the results of our remaining Phase III trials in order to fully evaluate tofacitinib in psoriasis and how it may fit into clinical practice".

Tofacitinib is sold for RA in the USA as Xeljanz but it is only approved for the 5mg dose. This summer advisors to the European Medicines Agency again rejected the drug for RA due to "outstanding concerns on safety, including serious infections".