The guselkumab group received 100-mg injections at week 0, week 4, and then every 8 weeks through week 44; the placebo group received injections at weeks 0, 4, 12, and 20, followed by 100 mg of guselkumab at weeks 24, 28, 36, and 44. Patients with less than 5% improvement from baseline in both tender and swollen joint counts at week 16 qualified for early escape to “initiate or increase the dose of one permitted concomitant medication up to the maximum allowed dose at the physician’s discretion.” Ultimately, 88% of patients in the guselkumab arm and 83% of the placebo arm completed the study.
At 24 weeks, more than 44% of the guselkumab group achieved a 20% or greater improvement in American College of Rheumatology criteria (ACR20), compared with just under 20% of the placebo group, a difference of nearly 25% (95% confidence interval, 14.1%-35.2%; multiplicity-adjusted P < .001). At 48 weeks, nearly 58% of the guselkumab group had achieved ACR20; of the 51 patients in the placebo arm who started taking guselkumab at week 24, 55% achieved ACR20 by week 48.
Through 24 weeks, 80 patients in the guselkumab group (42%) and 46 patients in the placebo group (48%) experienced adverse events; only 3.7% and 3.1% developed serious adverse events, respectively. The most common adverse events in the guselkumab group at that point included nasopharyngitis (5%) and upper respiratory tract infection (4%), which occurred at a similar frequency (5% and 3%) in the placebo group.
The authors acknowledge their study’s limitations, including imbalances in baseline characteristics such as gender and weight, as well as the COSMOS study being restricted to European patients and thus potentially limiting diversity. In addition, while the COVID-19 pandemic may have increased major protocol deviations near the end of the study, the authors note that “most were related to timing of study visits and did not impact efficacy.”
The study was funded by Janssen, and six authors reported being employees of the company. The authors also acknowledge numerous potential conflicts of interest, including receiving consulting fees and research grants from various pharmaceutical companies, including Janssen. Dr. Ruderman is a consultant for AbbVie, Bristol-Myers Squibb, Eli Lilly, Novartis, Pfizer, and Janssen and served on the data safety monitoring committee for two other phase 3 guselkumab trials.
A version of this article first appeared on Medscape.com.