B-269 Development and CYP3A4 Characterization of a Population-based Urinary Buprenorphine and Norbuprenorphine Nomogram

Abstract Background Buprenorphine (Bup), routinely prescribed for opioid use disorder, metabolizes to norbuprenorphine (NBup) primarily via cytochrome P450 (CYP) 3A4. Confirmation of urinary Bup and NBup helps monitor patient adherence to therapy and potential misuse. This study aims to develop and characterize a population-based urinary NBup/Bup nomogram using pharmacogenetics (PGx) to facilitate opioid result interpretations. Methods Adult urinary Bup and NBup results between 09/01/2022 and 09/30/2023 at UNC Health were retrieved from the EMR. Results outside the clinically reportable range (CRR; 5-25,000 ng/mL) were assigned the lower or upper CRR value, respectively. A scatterplot of Bup versus NBup/Bup on logarithmic scale was generated using Excel. Buffy coats from 14 EDTA whole blood samples were extracted and isolated using EasySep buffer (StemCell) with centrifugation at 8000rpm for 10 minutes without braking and stored at -80°C until shipment to DHMC. Genomic DNA was extracted using an EZ1 DNA procedure (Qiagen) and libraries (Agilent SureSelect) were prepared by hybridization capture of a custom PGx panel. Paired-end sequencing was performed on a MiSeq prior to diplotype-metabolizer function assignments in AUGMET. 22 CYP3A4 gene hotspots were detected by NGS and analyzed for gene-drug-variant relationships. Results 3593 results from 896 patients were retrieved. The NBup/Bup nomogram revealed 3 subgroups from this population (Figure). CYP3A4 genotyping showed 13 wildtype calls and 1 CYP3A4 *1/*22 star allele genotype, with reduced enzyme activity. Wildtype results corresponded with Bup/NBup in subgroups 1(n=1), 2 (n=11) and 3 (n=1); CYP3A4 *1/*22 result corresponded with subgroup 3. Conclusions We developed a novel NBup/Bup nomogram revealing 3 subgroups in our patient population. Overlap of wildtype CYP3A4 in subgroups 1, 2 and 3 as well as CYP3A4 *1/*22 genotype in subgroup 3 suggest the NBup/Bup subgroups are independent of CYP3A4 phenotype. The characterization of population-based urinary NBup/Bup nomogram shows promise for aiding in opioid result interpretations.