For patients with Crohn’s disease, therapeutic drug monitoring helped identify early primary nonresponders to induction with ustekinumab, according to researchers. The report is in Clinical Gastroenterology and Hepatology.
At week 8, median trough levels of ustekinumab were 6.0 mcg per mL (interquartile range, 3.1-8.0) among patients who achieved a primary response to induction at week 16, versus 1.3 mcg/mL (IQR, 0.9-5.6 ) among primary nonresponders (P = .03). An 8-week ustekinumab trough level cutoff of 2.0 mcg/mL distinguished week 16 responders from nonresponders with an area under the receiver operating curve (AUROC) of 0.75, wrote Ninon Soufflet of University Claude Bernard Lyon 1 in France, and associates. The researchers recommended “dedicated studies” to assess whether escalating the dose of ustekinumab can benefit patients with lower trough levels at week 8.
Few studies have explored biomarkers for response to ustekinumab induction therapy. Hence, the researchers assessed the relative utility of ustekinumab trough levels, C-reactive protein (CRP) levels, and fecal calprotectin levels for predicting early primary nonresponse. All 51 study participants had active luminal Crohn’s disease and received body weight–based intravenous infusions of ustekinumab at baseline, followed by subcutaneous injections of 90 mg. Primary nonresponders did not achieve steroid-free clinical and biochemical remission at week 16, defined as a Harvey-Bradshaw Index (HBI) of 4 points or less, a CRP level under 5 mg/L, and a fecal calprotectin level under 250 mcg/g. Week 16 was chosen to account for any delayed responders, the researchers noted.
A total of 32 patients (63%) achieved remission to ustekinumab induction therapy by week 16. An 8-week trough level of 2.0 mcg/mL was found to be optimal and distinguished primary nonresponders from responders with a sensitivity of 87%, a specificity of 66%, a positive predictive value of 82%, and a negative predictive value of 75%. In prior studies, optimal thresholds exceeded 3.3 mcg/mL for achieving remission and 4.5 mcg/mL at week 26 for achieving endoscopic response, the researchers noted. They said that this discrepancy might reflect different time points for evaluation, assays for measuring ustekinumab, patient populations, and a lack of endoscopic data in their study. “The relatively small sample size and the short period of follow-up evaluation [were] substantial limitations” they acknowledged.
