P093 IDENTIFICATION OF PATIENTS AT RISK OF SUBTHERAPEUTIC DRUG EXPOSURE PRIOR TO INITIATION OF CERTOLIZUMAB PEGOL THERAPY FOR THE TREATMENT OF CROHN’S DISEASE

Certolizumab pegol (CZP) is effective treatment for moderately-to-severely active Crohn’s disease (CD)^{1, 2} at approved subcutaneous doses of 400 mg on weeks 0, 2 and 4 (induction) and every 4 weeks thereafter (maintenance). Prior research has demonstrated a relationship between CZP drug exposure and outcomes, with higher plasma CZP concentrations during induction and maintenance therapy associated with more favorable clinical, endoscopic and biologic (C-reactive protein [CRP], fecal calprotectin [FC]) disease outcomes.³ Increased drug clearance is the driver of subtherapeutic CZP concentrations, although the identification of patients at risk for accelerated clearance prior to therapy initiation has not previously been possible.

A population pharmacokinetic model⁴ was used to estimate baseline CZP clearance (i.e., at the time of therapy initiation) using baseline clinical variables (i.e., gender, body weight, albumin and CRP concentration) available from patients with CD previously included in nine randomized, controlled, phase 2 and 3 trials (N=2157). Baseline CZP clearance was compared between patients who achieved observed Week 6 CZP plasma concentrations previously associated with meaningful clinical (>36 μg/mL for Crohn’s Disease Activity Index [CDAI] ≤ 150), biologic (>44 μg/mL for FC ≤ 250 μg/g) and composite clinical and biologic (>48 μg/mL for CDAI ≤ 150 and FC ≤ 250 μg/g) outcomes at Week 6. Receiver operating characteristic curve analysis identified baseline CZP clearance thresholds associated with effective CZP concentrations at Week 6.

Baseline CZP clearance was significantly higher in patients not achieving effective Week 6 CZP plasma concentration thresholds of 36 μg/mL, 44 μg/mL and 48 μg/mL compared to patients who achieved these thresholds (Figure 1; p<0.0001 for all comparisons). Baseline CZP CL of ≥ 0.5 L/day was associated with subtherapeutic observed Week 6 CZP plasma concentrations. The sensitivity, specificity, likelihood ratios and area under the concentration curves for the association between baseline CZP clearance and observed Week 6 CZP concentration thresholds are shown in Table 1.

Figure 1.

Mean baseline CZP clearance values in patients who did or did not achieve effective Week 6 CZP concentration thresholds.

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Table 1.

Receiver operating characteristic curve analysis of baseline CZP clearance and observed Week 6 CZP concentration thresholds.

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Patients with CD who have accelerated baseline CZP clearance are at risk of subtherapeutic CZP concentrations. Clearance can be calculated using baseline clinical variables and would allow for identification of patients for whom therapeutic CZP concentrations may be achieved with current approved dosing. Implementing therapeutic drug monitoring may increase the likelihood of achieving therapeutic drug exposure during induction as well as treatment success.

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• 20 Schreiber S et al. N Engl J Med 2007;357:239.

• 21 Vande Casteele N et al. Aliment Pharmacol Ther 2018;47:229.

• 22 Vande Casteele N et al. Clin Pharmacokinet 2017;56:1513.