STAT6 Variants Associate With Relapse of Eosinophilic Esophagitis in Patients Receiving Long-term Proton Pump Inhibitor Therapy.

BACKGROUND & AIMS: Based on histologic features, variants in STAT6 are associated with a poor initial response to proton pump inhibitor (PPI) therapy in pediatric patients with eosinophilic esophagitis (EoE). We investigated whether these genetic variants are associated with a poor long-term response in children with EoE who initially responded to PPI therapy. METHODS: We performed a prospective longitudinal cohort study of children ages 2 to 16 years who met the diagnostic criteria for EoE (≥15 eosinophils/high-power field [eos/hpf]), responded to 8 weeks of treatment with 2 mg/kg/d PPI (<15 eos/hpf), and whose dose then was reduced to 1 mg/kg/d PPI (maintenance therapy) for 1 year, at which point biopsy specimens were collected by endoscopy. Genomic DNA was isolated from formalin-fixed paraffin-embedded biopsy tissue and was genotyped for variants of STAT6. Remission of inflammation was assessed at eos/hpf thresholds of <15 and ≤5. RESULTS: Among 73 patients who received 1 mg/kg/d PPI maintenance therapy for 1 year, 13 patients (18%) had 6 to 14 eos/hpf, 36 patients (49%) had 5 or fewer eos/hpf, and 24 patients (33%) relapsed to EoE (≥15 eos/hpf). Carriage of any of 3 STAT6 variants in linkage disequilibrium (r2 ≥0.8; rs324011, rs167769, or rs12368672) was associated with a 2.3- to 2.8-fold increase in the odds of EoE relapse, and with a 2.8- to 4.1-fold increase in the odds of having 6 to 14 eos/hpf. For rs324011, the odds ratio [95% CI] for relapse was 2.77 [1.11, 6.92]; P = .029, and the odds ratio [95% CI] for having 6 to 14 eos/hpf was 3.06 [1.27, 7.36]; P = .012. CONCLUSIONS: Pediatric EoE patients who initially respond to PPI therapy and carry STAT6 variants rs324011, rs167769, or rs12368672 are at increased risk of relapse after 1 year of PPI maintenance therapy.

CYP2C19 and STAT6 Variants Influence the Outcome of Proton Pump Inhibitor Therapy in Pediatric Eosinophilic Esophagitis.

OBJECTIVE: Proton pump inhibitors (PPIs) are an effective treatment for eosinophilic esophagitis (EoE); however, only 30% to 60% of patients respond. Common genetic variants in CYP2C19 and STAT6 associate with PPI plasma concentration and magnitude of inflammatory response, respectively. Our objective was to determine if genetic variation in the genes for CYP2C19 and STAT6 influence differentiation between PPI responsive esophageal eosinophilia versus PPI nonresponsive EoE (PPI-REE, PPI-nonresponsive EoE). METHODS: Genomic DNA was isolated from 92 esophageal tissue biopsies collected from participants of a prospective clinical trial of high-dose PPI therapy for esophageal eosinophilia in children. RESULTS: Of the 92 patients examined, 57 (62%) were PPI-REE and 35 (38%) were PPI-nonresponsive EoE. Forty-six of the 92 patients were further characterized by pH probe monitoring; there was no association between reflux index and carriage of CYP2C1917 (P = 0.35). In children who received a PPI dose between ≥1.54 and ≤2.05 mg/kg/day, binary logistic regression modeling showed that carriage of CYP2C1917 associated with PPI-nonresponsive EoE (odds ratio (OR) [95% confidence interval (CI)] = 7.71 [1.21, 49.11], P = 0.031). Carriage of STAT6 allelic variant rs1059513 predicts PPI-REE (OR [95% CI] = 6.16 [1.44, 26.4], P = 0.028), whereas carriage of STAT6 rs324011 synergizes with CYP2C1917 to predict PPI-nonresponsive EoE (rs324011 OR [95% CI] = 5.56 [1.33, 20.72], P = 0.022; CYP2C1917 OR [95% CI] = 8.19[1.42, 50.57], P = 0.023). CONCLUSIONS: Common variants in CYP2C19 and STAT6 associate with a PPI-nonresponsive EoE outcome of PPI therapy for esophageal eosinophilia suggesting that response rates may be improved by adopting a genotype-guided approach to PPI dosing.

Novel Implementation of Genotype-Guided Proton Pump Inhibitor Medication Therapy in Children: A Pilot, Randomized, Multisite Pragmatic Trial.

The efficacy of proton pump inhibitor (PPI) medications is highly dependent on plasma concentrations, which varies considerably due to cytochrome P450 (CYP2C19) genetic variation. We conducted a pragmatic, pilot study of CYP2C19 genotype-guided pediatric dosing of PPI medications. Children aged 5-17 years old with gastric-acid-related conditions were randomized to receive either conventional dosing of a PPI or genotype-guided dosing for a total of 12 weeks. Sixty children (30 in each arm) were enrolled and had comparable baseline characteristics. The mean daily omeprazole equivalent dose prescribed to participants across metabolizer phenotype groups was significantly different in the genotype-guided dosing arm (P < 0.001), but not in the conventional dosing arm. Prescribers waited for the genotype result before prescribing the PPI medication for 90% of the participants in the genotype-guided dosing arm. The number of participants who reported an infection was marginally lower in genotype-guided dosing vs. conventional dosing (20% vs. 44%; P = 0.07). Sinonasal symptoms were higher in the conventional dosing arm as compared with genotype-guided dosing arm: (2.6 (2.0, 3.4) vs. 1.8 (1.0, 2.3), P = 0.031). CYP2C19 genotype-guided PPI therapy is feasible in a clinical pediatric setting, well accepted by providers, resulted in differential PPI dosing, and may reduce PPI-associated infections. A future large scale randomized clinical trial of CYP2C19 genotype-guided pediatric dosing of PPI medications in children is warranted.