Phase III data suggests Pfizer’s arthritis drug Xeljanz is on track for an extension of its indications into psoriasis, although a lack of efficacy at a lower dose raises some concerns.
The company has yet to provide full details but said top-line results from one 12-week study show that Xeljanz (tofacitinib) was as effective as Pfizer’s own blockbuster Enbrel (etanercept) when given at a 10mg dose to patients with moderate-to-severe chronic plaque psoriasis.
A lower 5mg dose did not however meet the criteria for non-inferiority to Enbrel which could have an impact on the drug’s prospects, according to analysts at ISI Group, who suggest it may now be perceived as less effective than Enbrel and other biologics for psoriasis.
Xeljanz was approved for marketing for rheumatoid arthritis in the US just under a year ago, but only at 5mg twice-daily as the 10mg dose was not considered to have an adequate risk-to-benefit ratio. The European Medicines Agency’s Committee for Medicinal Products for Human Use took an even dimmer view of the drug, and declined to approve it for the second time in July.
A second, 56-week trial of the drug compared the efficacy and safety of withdrawal and retreatment with Xeljanz (both 5mg and 10mg) to placebo. It showed that a higher number of patients who continued Xeljanz 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 Pfizer’s drug.
The data is from two of five planned trials of tofacitinib in psoriasis that Pfizer hopes will form the basis of marketing applications of the Janus kinase (JAK) inhibitor which, if approved, could impart some much-needed sales momentum for the product.
In RA the drug added just $22m to Pfizer’s revenues in the second quarter, so it has a long way to go before it starts to help Pfizer recoup the ground lost by generic competition to its Lipitor (atorvastatin) blockbuster for elevated cholesterol.
Analyst predictions around the launch of tofacitinib last year suggested peak sales of the drug could reach $2bn a year, with around half of that total coming from psoriasis and psoriatic arthritis.