Concentration of the drug ustekinumab in the blood four weeks after injection, is linked to how well moderate‐to‐severe psoriasis responds to treatment

Psoriasis is a chronic inflammatory skin disease causing red, itchy and scaly patches of skin. It affects about 2-3% of the Western population. In moderate-to-severe cases, patients are treated with drugs called biologicals, including ustekinumab. Although these drugs have been shown to improve patients’ symptoms, there are still individuals that do not respond to treatment, meaning they do not see any improvement, or lose response over time, meaning the improvement lessens. One reason for the loss of response is that the drug concentration in the blood of the patient is too low. Therefore, it might be interesting to measure drug concentrations to shed light on what is happening with the drug in the patient. However, measuring drug concentrations is only useful if the drug concentration is associated with what happens to the skin disease. This study, performed in Belgium, aimed to find out if the concentration of the drug ustekinumab was associated with clinical response (whether or not the symptoms improved). Therefore, ustekinumab concentrations were measured in the blood of 49 patients with moderate-to-severe psoriasis, four weeks after ustekinumab injection. The authors found that patients with higher ustekinumab concentrations had a better clinical response than patients with a lower concentration. Moreover, they identified the minimal ustekinumab blood concentration needed at week four to achieve the best response. With this information, the dermatologist can measure drug concentrations to identify patients who do not adequately respond to treatment because of insufficient drug concentrations. In that case, the patient's dose can be adapted to achieve a better response and consequently improve the quality of life. This summary relates to the study: Clinical response correlates with 4-week postinjection ustekinumab concentrations in patients with moderate-to-severe psoriasis