In two of the trials (UNCOVER-1 and -2), patients who had responded to ixekizumab treatment in the first 12 weeks (sPGA 0, 1) were randomised to ixekizumab or placebo for a further 48 weeks. At the end of these extension studies, 74.6% of the 181 patients who had originally responded to fortnightly ixekizumab injections continued to respond to ixekizumab given every four weeks. This compared with only 7.4% of the 203 patients who were switched to placebo.
The most common adverse events with ixekizumab were mild–moderate injection-site reactions which occurred in 16.8% of those receiving fortnightly treatment. This was followed by upper respiratory tract infection (14%), nausea (2%), oropharyngeal pain (1.4%) and tinea infection (1.5%). Oral and vaginal candidiasis were also reported, as was neutropenia. As there is an increased risk of infection, caution is urged if ixekizumab is given to people with chronic or active infection. Patients should be tested for tuberculosis before treatment and live vaccines are not recommended.
Patients can have hypersensitivity reactions to ixekizumab, and 9–17% of patients developed antibodies to treatment. However, most of these cases were not associated with reduced efficacy.
Crohn’s disease and ulcerative colitis, including exacerbations, were more common with ixekizumab than with placebo (0.1–0.2% vs 0%). People with inflammatory bowel disease should therefore be monitored closely.
There have been no drug interaction studies with ixekizumab and it has not been assessed in pregnant or breastfeeding women. In studies on monkeys, the drug crossed the placenta but did not appear to be toxic to the fetus. It was also excreted at low levels in the breastmilk of lactating monkeys. It is not known if ixekizumab affects fertility.
The recommended regimen for ixekizumab is a 160 mg loading dose as two subcutaneous injections. This should be followed by a single 80 mg injection every two weeks until week 12, then every four weeks.
Ixekizumab seems to be very effective for people with moderate–severe plaque psoriasis in the short term.
It also appeared to be relatively safe but, because of its effects on the immune system, patients need to be monitored for infections. As ixekizumab probably needs to be continued indefinitely, it will be important to find out what the long-term safety of this drug is and how it compares to other biological drugs for psoriasis such as secukinumab, ustekinumab, adalimumab and infliximab. Ixekizumab has also shown efficacy in psoriatic arthritis.4