Category: Formulation and Quality
Purpose: Upregulation of multi-drug resistance protein (MRP1) expression in ocular tumors limits the efficacy of anticancer drugs. Hence, the goal of the current study was to investigate the co-administration of specific MRP inhibitors (MK571 (MK) or Probenecid (PB)), administered in a topical ophthalmic film, and systemic administration of the substrate Fluorescein (FL), as a new strategy to improve therapeutic outcomes in ocular tumors.
Methods: Fluorescein (FL) solution (1 mg/mL) was made with equal volumes of ethanol and saline. The inhibitor MK or PB films were prepared using POLYOX™ WSR N10, by melt cast technology. Inhibitor and polymer compatibility studies were performed using Fourier transmission infrared spectroscopy (FTIR) and Differential scanning calorimetry (DSC). Films of 1mm x 2mm x 0.2mm dimensions were used for the in vitro studies. Content uniformity was determined using four separate sections of 2 mg each, randomly cut from a single 13 mm film, and analyzed for inhibitor content. The in vitro transport studies were carried out by using corneal and sclera-choroid-retinal tissues isolated from New Zealand White rabbit eyes. The transport studies were conducted for 3h time periods to understand the permeation of the inhibitors across the ocular tissues. Electroretinography (ERG) studies were performed to identify whether coadministration of MK or PB (topically administered)-FL (IV injection) induced any toxic effects on the structures and functions of retina in the wild type (WT) Sprague Dawley (SD) male albino rats. Ocular biodistribution studies were carried out in male SD WT rats using 10% w/w inhibitor loaded films placed in the conjunctival sacs 30 minutes prior to a 1mg/kg tail vein injection of FL solution. The rats were euthanized at predetermined time points. Prior to euthanization, a blood sample was collected under deep anesthesia, following which the animals were euthanized. The eyes were enucleated and the AH and VH were carefully extracted. The extracts were quantified for FL using UHPLC-TQ-MS system.
Results: The drug solution was stable at room temperature for 30 days with an assay of 98%. The content uniformity (CU) of MK in the films was 104.0 ± 5.5% with an assay of 105.1 ± 4.2% for films with PEO. The CU of PB in the films made with PEO alone was 98.8 ± 2.4% with an assay of 98.4 ± 3.2%. FTIR and DSC studies confirmed compatibility between the inhibitors and polymers. The in vitro transport studies of inhibitors across the membrane showed good transocular membrane permeability. Transcorneal flux of PB (0.20 ± 0.07 µg/ml.cm2) and MK (0.64 ± 0.11 µg/ml.cm2) was similar to that of the trans-SCR flux of PB (0.68 ± 0.19 µg/ml.cm2) and MK (0.12 ± 0.07 µg/ml.cm2). The ERG studies confirmed the lack of any toxic effect in the retina as a result of the inhibitor-FL coadministration. Ocular biodistribution studies showed higher levels of MK within the VH compared to the AH. However, when FL was co-administered with the inhibitor (MK or PB) loaded films, a significantly higher amount of FL was seen in the AH of WT rats; AH – 0.1 ng/mL and VH – 0.04 ng/mL with MK and AH- 0.37 ng/mL and VH-0.02 ng/mL with PB. The MK levels in AH (0.6 ng/mL) and in the VH (5.2 ng/mL) at the 12 h time point, suggested that the inhibitors effectively modulated the MRP activity in the blood-ocular barriers and improved the blood-ocular penetration of FL.
Conclusion: The co-administration of topical ocular films containing specific MRP inhibitors improves blood-ocular penetration of systemically administered anti-cancer drugs and is a potential approach to improve efficacy in ocular cancer therapy.
Karthik Yadav Janga– Graduate student, Department of Pharmaceutics and Drug Delivery, School of Pharmacy, The University of Mississippi. Oxford, MS, University, Mississippi
Akshaya Tatke– Graduate student, Department of Pharmaceutics and Drug Delivery, School of Pharmacy, The University of Mississippi. Oxford, MS, Oxford, Mississippi
Bhavik Soneta– Masters student, Department of Pharmaceutics and Drug Delivery, School of Pharmacy, The University of Mississippi. Oxford, MS, University, Mississippi
Narendar Dudhipala– Postdoctoral research fellow, University of Mississippi, University, Mississippi
Monica Jablonski– Memphis, Tennessee
Soumyajit Majumdar– Professor and Associate Dean, Department of Pharmaceutics and Drug Delivery, School of Pharmacy, The University of Mississippi. Oxford, MS, University, Mississippi
XiangDi Wang– Research scientist, Department of Ophthalmology, Hamilton Eye Institute, The University of Tennessee and Health Science Center. Memphis, TN, Memphis, Tennessee