Researchers found a statistically significant association between early ustekinumab levels and 6-month Psoriasis Area and Severity Index-75 response in patients taking the drug.
“This finding suggests that adequate drug exposure early in the treatment cycle may be particularly important in determining clinical outcome with ustekinumab,” Teresa Tsakok, MA, MRCP, of St John’s Institute of Dermatology, School of Basic and Medical Biosciences, faculty of life sciences and medicine, King’s College London
and colleagues wrote.
The study included 491 adults receiving Stelara (ustekinumab, Janssen) monotherapy with serum samples and PASI scores available for the first year of treatment. Men accounted for 65.2% of the cohort.
More than half of patients (282, 57.4%) were receiving 45 mg of ustekinumab compared with 209 patients (42.6%) receiving 90 mg; 201 patients (40.9%) were biologic-naive.
PASI75 was achieved at some point within a year of beginning treatment in 348 patients (70.9%).
The median drug level was 1.19 µg/mL from 800 samples (IQR, 0.37-2.86 µg/mL; range, 0-13 µg/mL).
At 6 months, patients achieving PASI75 on average had higher early ustekinumab levels at a median of 2.78 µg/mL compared with those not achieving PASI75 at a median of 1.83 µg/mL (IQR, 1.78-4.02 µg/mL vs. 0.96-2.86 µg/mL).
The early drug level was associated with PASI75 at 6 months (OR = 1.27; 95% CI, 1.04-1.56), but this association did not hold for other PASI outcomes.
“The final model for PASI75 included drug dose, baseline PASI score and age as well as drug level and shows increasing probability of response with increasing drug level,” the researchers wrote. “The model also suggests that patients taking the higher ustekinumab dose (90 mg) have a lower probability of response for a given drug level.”
There may be a benefit to individualized dose optimization and therapeutic drug monitoring of ustekinumab, according to researchers. – by Abigail Sutton
Disclosures: Tsakok reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.