Interaction studies of RX-10045 (Resolvin E1 Analog) with Efflux TransportersInteraction studies of RX-10045 (Resolvin E1 Analog) with Efflux Transporters

Abstract

 

Purpose

 

Resolvin E1 analog (RX-10045) was originally formulated as an aqueous solution and tested for the treatment of dry eye with topical drop application. RX-10045 was highly efficacious in murine models of dry eye syndrome. However, in Phase II clinical trials,RX-10045, though safe and well tolerated, produced equivocal efficacy results. Disposition across the human cornea and conjunctiva may be limited due to efflux transporters expressed on the ocular surface. Therefore, we aimed to screen interactions of RX-10045 with efflux transporters (P-gp, MRP2 and BCRP).

 

Methods

 

Madin-Darby canine kidney cells transfected with P-gp, MRP2 and BCRP gene were selected for this study. [3H]Digoxin, [3H]Vinblastine and [3H]Abacavir were selected as model substrates for P-gp, MRP2 and BCRP. Uptake and permeability studies in both apical to basal (AP−BL) and BL−AP of these substrates were conducted in presence of specific efflux pump inhibitors and RX-10045. Cell viability studies were conducted with increasing concentrations of RX-10045.

 

Results

 

Uptake studies showed higher accumulation in the presence of inhibitors (GF120918 and ketoconazole for P-gp; MK571 for MRP2 and β-estradiol for BCRP) as well as RX-10045. Similarly, dose dependent inhibition studies demonstrated higher accumulation of various substrates ([3H]-Digoxin, [3H]-Vinblastine and [3H]-Abacavir) in the presence of RX-10045. IC₅₀ values of dose dependent inhibition of RX-10045 for P-gp, MRP2 and BCRP were 239 ±11.2 µM, 291 ± 79.2 µM and 300 ± 42 µM, respectively. Cell viability assay indicated no apparent toxicity at 350 µM concentration. Enhanced permeability for model substrates was observed in presence of RX-10045. Uptake studies in HCEC cells suggest RX-10045 is a strong inhibitor of organic cationic transporter-1 (OCT-1).

 

Conclusions

 

In summary, the resolvin analog (RX-10045) was identified as substrate/inhibitor for efflux transporters. Also, RX-10045 appears to be a strong inhibitor of OCT-1. Novel formulation strategies such as nanoparticles, nanomicelles and liposomes for circumventing efflux barriers and deliver higher drug concentrations leading to higher therapeutic efficacy may be employed.  

 

Fig 1. Apical to basal apparent permeability of [3H] vinblastine (MRP2 substrate) in the presence of inhibitor (MK571) and RX-10045 with [3H] vinblastine as control.