LB-006 - EFFECTS OF ANTIOXIDANTS IN DRUGS PRODUCTS ON INTESTINAL DRUG TRANSPORTERS.

M. Koleske¹, C. Kulkarni¹, K. Alam², A. Raw², B. Rege², L. Zhao², D. Lu², L. Zhang², K. Giacomini¹, D. Kroetz¹, S. Yee¹; ¹University of California, San Francisco, San Francisco, CA, United States, ²US Food and Drug Administration, Silver Spring, MD, United States.

Background: The presence of nitrosamine impurities, which are potentially mutagenic and carcinogenic, in drug products poses a major safety risk. One strategy to mitigate the nitrosamines risk is to include antioxidants in drug formulations. The goal of our study is to evaluate the potential impact of antioxidants on three major intestinal transporters, OATP2B1, P-gp, and BCRP to predict whether there is any influence on product absorption.

Methods: Thirty-one antioxidants were screened for potential inhibition of intestinal transporters OATP2B1 (SLCO2B1), P-gp (ABCB1) and BCRP (ABCG2), using 3H-estrone sulfate, 3H-N-methyl quinidine and 3H-CCK8 as probe substrates, respectively. All antioxidants were screened at 200 µM in HEK293 Flp-In cells (OATP2B1) or in membrane vesicles (P-gp, BCRP) expressing the transporters. Inhibition potency studies (IC50) were also performed for potential inhibitors.

Results: The inhibition screen identified antioxidants that inhibited OATP2B1 (4 antioxidants), P-gp (3) and BCRP (3) by more than 50%. Three antioxidants, butylated hydroxyanisole (BHA), carnosic acid and curcumin, inhibited all three transporters, and ascorbyl palmitate (AP) inhibited OATP2B1. Inhibition potency studies were conducted for BHA and AP. IC50 value of BHA for OATP2B1, P-gp and BCRP transporters was 61 ± 18 µM, 182 ± 49 µM and 206 ± 14 µM, respectively. The IC50 value of AP for OATP2B1 was 86 ± 25 µM.

Conclusion: Initial screening revealed that IC50 values for AP and BHA on intestinal transporters are close to the estimated maximal intestinal concentrations for these antioxidants (96 µM for AP and 178 µM for BHA), indicating they may affect bioavailability of drugs that are substrates of OATP2B1, P-gp or BCRP. The clinical impact of these findings warrants further study.