Localized modulation of RPE P-gp/MRP activity for back-of-the-eye drug delivery

描述（由申请人提供）：由RPE基底外侧膜上表达的P-糖蛋白（P-gp）和多药耐药蛋白（MRP）介导的外排使得药物递送至后房成为一项具有挑战性的任务。目前，直接玻璃体内给药是眼后部疾病最有效的药物递送模式。然而，这种给药途径与许多风险相关，如视网膜脱落、继发性感染等。（作为滴眼剂）P-gp和/或MRP底物和/或抑制剂可以调节在视网膜色素上皮（RPE）上表达的外排蛋白P-gp和/或MRP的活性，从而改变全身/玻璃体内共同施用的底物的眼部药代动力学。该应用基于以下假设：局部应用的P-gp/MRP底物可以与RPE基底外侧膜上表达的P-gp/MRP相互作用，并调节它们的外排活性。局部滴注后，P-gp/MRP底物可通过沿着角膜-巩膜交界处的侧向扩散或通过渗透穿过结膜进入巩膜而到达巩膜。巩膜和下面的脉络膜对药物扩散不构成显著的屏障。因此，局部施用的药剂的一部分可以渗透到RPE，并潜在地与在RPE的基底外侧膜上表达的P-gp/MRP相互作用并影响其流出活性。因此，局部应用的P-gp/MRP底物可以影响RPE相对于P-gp/MRP底物的屏障性质。因此，可以显著增强药物从体循环渗透到眼后部。相反，局部应用P-gp/MRP底物可能会减少玻璃体内给药底物的消除，从而延长其在眼后部眼部组织中的保留。初步研究表明，玻璃体内给药奎尼丁的玻璃体消除半衰期在局部共同给药红霉素的存在下增加了近2.5倍。本申请中提出的新研究将描述局部施用的P-gp/MRP底物对麻醉兔模型中全身或玻璃体内施用的底物的眼部药代动力学的影响。奎尼丁是P-gp/MRP的底物，已证实其与RPE P-gp的相互作用，将在这些探索性研究中用作标记化合物。红霉素和泼尼松龙是常用的局部药物，也是P-gp和/或MRP的既定底物，将局部给药。因此，本申请试图评价局部施用红霉素和泼尼松龙（各3剂）对（a）玻璃体内和（B）全身施用奎尼丁的眼部药代动力学的影响。预期基于来自本研究的发现，可以开发用于局部调节RPE的P-gp和/或MRP的外排活性的新方法并用于眼后药物递送。由视网膜色素上皮上表达的P-糖蛋白（P-gp）和多药耐药蛋白（MRP）介导的外排使得药物递送至后房眼组织或眼后部成为一项具有挑战性的任务。目前，直接玻璃体内给药是用于眼后部疾病的药物递送的优选模式。然而，这种给药途径与许多风险相关。本申请中提出的研究将探索局部抑制P-gp和MRP外排活性的非侵入性策略，这可能导致在全身或玻璃体内给药后，在眼后部眼组织中产生或维持增强的药物浓度。因此，该研究项目的结果可能会改善后房眼病的治疗结果，如眼内炎、糖尿病视网膜病变、黄斑变性、视网膜母细胞瘤和其他眼内肿瘤。

DESCRIPTION (provided by applicant): Efflux mediated by P-glycoprotein (P-gp) and multidrug resistance protein (MRP) expressed on the basolateral membrane of the RPE makes drug delivery to the posterior ocular chamber a challenging task. Currently, direct intravitreal administration is the most effective mode of drug delivery for back-of-the-eye diseases. This route of administration, however, is associated with a number of risks such as retinal detachment, secondary infections etc. The objective of this proposal is to elucidate whether topically applied (as eye drops) P-gp and/or MRP substrates and/or inhibitors can modulate the activity of the efflux proteins, P- gp and/or MRP, expressed on the retinal pigmented epithelium (RPE), and thus alter ocular pharmacokinetics of systemically/intravitreally co-administered substrates. This application is based on the hypothesis that topically applied P-gp/MRP substrates can interact with P-gp/MRP expressed on the basolateral membrane of the RPE and modulate their efflux activity. P-gp/MRP substrates, following topical instillation, may reach the sclera either by lateral diffusion along the corneal-scleral junction, or by permeating across the conjunctiva into the sclera. The sclera and the underlying choroid do not pose a significant barrier to drug diffusion. Thus, a fraction of the topically applied agent can penetrate to the RPE and potentially interact with and influence the efflux activity of P-gp/MRP expressed on the basolateral membrane of the RPE. Topically applied P-gp/MRP substrates could thus affect RPE's barrier properties with respect to P-gp/MRP substrates. Consequently, drug penetration into the back-of-the-eye from the systemic circulation could be significantly enhanced. Conversely, topically applied P-gp/MRP substrates may decrease elimination of intravitreally administered substrates, and could thus prolong their retention in the back-of-the eye ocular tissues. Preliminary studies indicate that the vitreal elimination half-life of intravitreally administered quinidine is increased almost 2.5-folds in the presence of topically co-administered erythromycin. The novel studies proposed in this application will delineate the effect of topically applied P-gp/MRP substrates on ocular pharmacokinetics of systemically or intravitreally administered substrates in an anesthetized rabbit model. Quinidine, a substrate of P-gp/MRP, and, whose interaction with RPE P-gp has been demonstrated, will be employed as a marker compound in these exploratory studies. Erythromycin and prednisolone, commonly employed topical agents and established substrates of P-gp and/or MRP, will be administered topically. Thus, this application seeks to evaluate the effect of topically administered erythromycin and prednisolone (3 doses each) on ocular pharmacokinetics of (a) intravitreally and (b) systemically administered quinidine. It is expected that based on the findings from this study a novel approach for localized modulation of the efflux activities of RPE's P-gp and/or MRP can be developed and utilized for back-of-the-eye drug delivery. /Relevance Efflux mediated by P-glycoprotein (P-gp) and multidrug resistance proteins (MRP) expressed on the retinal pigmented epithelium makes drug delivery to the posterior chamber ocular tissues, or back-of-the-eye, a challenging task. Currently, direct intravitreal administration is the preferred mode of drug delivery for back-of- the-eye diseases. This route of administration, however, is associated with a number of risks. The studies proposed in this application will explore a noninvasive strategy for localized inhibition of the efflux activities of P-gp and MRP, which could lead to the generation or maintenance of enhanced drug concentrations in back- of-the-eye ocular tissues, following systemic or intravitreal administration. Results from this research project may thus improve treatment outcomes for posterior chamber ocular diseases such as endophthalmitis, diabetic retinopathy, macular degeneration, retinoblastoma and other intraocular tumors.