A proactive approach to therapeutic drug monitoring during maintenance therapy with infliximab in the treatment of inflammatory bowel diseases (IBDs) and other chronic immune-mediated inflammatory diseases significantly improves sustained disease control, compared with standard care, which was defined as no therapeutic drug monitoring, new research shows.
“This trial showed that therapeutic drug monitoring improved infliximab [maintenance] treatment by preventing disease flares without increasing drug consumption,” reported the authors of the study published in JAMA.
Infliximab and other tumor necrosis factor (TNF)–inhibitor drugs offer significant benefits in the treatment of IBDs and other chronic inflammatory diseases; however, up to 50% of patients become nonresponsive to the therapy within the first years of treatment, posing risks of disease worsening and possible organ damage.
Dr. Silje W. Syversen
To address the problem, therapeutic drug monitoring has been recommended, more so with IBD guidelines than rheumatoid arthritis; these have included measures such as dose adjustment or drug switching when there is evidence that disease control is not being maintained.
However, with low serum drug concentrations and the development of antidrug antibodies believed to be key indicators of a waning response, there is growing interest in a more proactive monitoring approach, involving scheduled assessments of serum and antibody levels, performed regardless of any signs of disease activity changes, and the provision of dosing adjustments, if needed.
In the earlier Norwegian Drug Monitoring (NORDRUM) A trial, first author Silje Watterdal Syversen, MD, PhD, of the division of rheumatology and research, Diakonhjemmet Hospital, Oslo, Norway, and colleagues evaluated the effects of the proactive drug monitoring approach during the initiation phase of infliximab treatment, but found no significant improvement in the study of 411 patients in terms of the primary outcome of remission rates.
For the current NORDRUM B trial, they sought to instead determine if benefits of the proactive therapeutic drug monitoring may be more apparent during the maintenance phase of infliximab treatment.
The trial involved 458 adults at 20 hospitals in Norway who had immune-mediated inflammatory diseases (IMIDs), including rheumatoid arthritis (n = 80), spondyloarthritis (n = 138), psoriatic arthritis (n = 54), ulcerative colitis (n = 81), Crohn’s disease (n = 68), or psoriasis (n = 37), and who were undergoing maintenance therapy with infliximab.
The patients, who had a median of about 40 weeks’ prior infliximab therapy, were randomized 1:1 to receive either proactive therapeutic drug monitoring, consisting of scheduled monitoring of serum drug levels and antidrug antibodies and adjustments in dose and intervals as needed according to a trial algorithm (n = 228), or standard infliximab therapy, without the regular drug and antibody level monitoring (n = 230).
Over a 52-week follow-up, the primary outcome of sustained disease control without disease worsening was significantly higher in the proactive therapeutic drug monitoring group (73.6%; n = 167) versus standard care (55.9%; n = 127; P < .001). The risk of disease worsening was meanwhile significantly greater with standard care versus proactive drug monitoring (hazard ratio, 2.1).
Serum infliximab levels remained within the therapeutic range throughout the study period in 30% of patients receiving proactive therapeutic drug monitoring, compared with 17% in the standard care group, and low serum infliximab levels (≤2 mg/L) occurred at least once during the study period among 19% and 27% of the two groups, respectively.
Clinically significant levels of antidrug antibodies (≥50 mcg/L) occurred in 9.2% of the therapeutic drug monitoring patients and 15.0% of the standard care group.
About 55% of patients were also using concomitant immunosuppressive therapy, and the findings were consistent among those who did and did not use the drugs. There no significant differences in adverse events between the therapeutic drug-monitoring (60%) and standard care groups (63%).
Importantly, while the mean dose of infliximab during the trial was 4.8 mg/kg in both groups, an increase in dosage after disease worsening was more common in the standard therapy group (51%) than in the therapeutic drug monitoring group (31.6%), underscoring the improved dose control provided with the proactive therapeutic drug monitoring, the authors note.
The findings suggest “proactive therapeutic drug monitoring might be more important during maintenance therapy, a period during which low drug levels could be an important risk factor for therapeutic failure,” the authors conclude.
In commenting to this news organizatin, Dr. Syversen noted that, despite the variety of IMIDs, there were no significant differences with IBDs or other disorders.
“Our data show consistent findings across all diseases included,” she said.
Furthermore, “in the present study, and [prior research] using the same definition of disease worsening, IBD patients in general had a comparable flare rate as compared to inflammatory arthritis.”
