Therapeutic Drug Monitoring of Biologics in Patients With Inflammatory Bowel Disease: A Real World Experience

Abstract

Introduction: Therapeutic drug monitoring (TDM) is recommended by the American Gastroenterological Association to guide treatment changes with anti-TNF agents in patients (pts) with inflammatory bowel disease (IBD). Studies have shown that changes in treatment regimen of biologics in response to TDM are beneficial in achieving clinical remission. We examined utilization of TDM for various biologics and assessed clinical remission after therapeutic changes in IBD pts treated at a large private practice. Methods: We conducted a retrospective chart review of IBD pts, who had TDM during maintenance therapy on adalimumab (ADA), certolizumab pegol (CZP), infliximab (IFX), or vedolizumab (VDZ) between 03/2016 and 03/2018. Data included demographics, disease characteristics, serum drug concentrations and anti-drug antibodies (ADAbs). Study design is shown in Figure 1. Target concentrations for ADA, CZP, IFX, and VDZ were ≥7.5mg/mL, ≥20mg/mL, ≥5mg/mL and ≥12mg/mL, respectively. Clinical remission was assessed 6 months (mo) post TDM intervention using Harvey-Bradshaw Index less than 5 for Crohn's disease (CD) and partial Mayo score less than 2 for ulcerative colitis (UC). Categorical data were analyzed with frequency distributions, continuous variables with mean±SD and interquartile range [IQR].740_A Figure 1 No Caption available.Results: A total of 141 IBD pts (60% CD, 40% UC, mean age 45±15 years) had TDM on various biologics (1 ADA, 2 CZP, 120 IFX, 18 VDZ). Proactive TDM was performed in 32% and reactive TDM in 68%. Pts were divided into 3 groups for analysis: those with therapeutic drug level (25%, n=35), sub-therapeutic drug level but no ADAbs (57%, n=80) and sub-therapeutic drug level with ADAbs (18%, n=26). TDM resulted in therapy changes in 106 pts (75%). Interventions were shortened interval (33%, n=35), increased dosage (32%, n=34), changes in both interval and dosage (8%, n=8) and discontinuation of biologic (27%, n=29). Clinical remission rates for pts with continued biologics are noted in Table 1. Overall, TDM-guided changes of biologic regimens resulted in a 57% clinical remission at 6 mo. Among pts not responding to TDM changes, 12 discontinued their current biologic after a median of 3.6 mo [IQR 2.9-4.1] due to progressive disease (n=9) and adverse events (n=3). Further TDM was performed in 51% of pts, who had changes made to their biologic. Conclusion: This real-world study demonstrates benefits in achieving clinical remission following TDM-guided management of biologics in IBD pts.740_B Figure 2 No Caption available.