SUN-159 ORAL NANOCAPSULE FORMULATION FOR POLYCYSTIC KIDNEY DISEASE

Abstract

Nanomaterials are promising drug delivery tools, but few have been successful for oral administration. Oral delivery has the highest patient compliance and is optimal for chronic diseases like polycystic kidney disease (PKD). PKD affects 12.5 million individuals, where diseased tubule cells produce cysts that destroy kidney function1. Drug candidates to slow cyst growth require high dosages, leading to side effects. For example, the only FDA-approved PKD drug, Tolvaptan, showed a 23% dropout during clinical trials due to nausea and abdominal pain2. To limit toxicity, we previously developed self-assembled kidney targeting micelles, (KM) and found they accumulated in the kidneys3. To augment this for oral delivery, herein, we load KMs and metformin (met) into chitosan nanocapsules, which have been reported to overcome the barriers of the gastrointestinal (GI) tract. Metformin is an FDA-approved drug for diabetes which can also slow cyst growth. We hypothesize that chitosan nanocapsules deliver met across the GI tract to show efficacy in PKD mice. Furthermore, we characterize KMs loaded into chitosan nanocapsules to serve as a platform for oral delivery of nanotherapeutics. Capsules were synthesized as previously described in literature4. Briefly, 2 mg/ml of chitosan was added dropwise to a 1 mg/ml solution of poly-glutamic acid crosslinker. Met was loaded into our chitosan nanocapsules (CS-NP met) by mixing with the crosslinker. To assess oral delivery performance, we administered 300 mg/kg met loaded in CS-NP or free met to Pkd1fl/fl;Pax8 rtTA;Tet-O cre mice. Pups were IP injected with doxycycline on P10-11 to induce a cystic phenotype. Mice were orally gavaged every three days starting on P12 until P22. Kidneys were excised to assess kidney to body weight ratio and stained with haemotoxylin and eosin (H&E) to compare cystic index. To confirm the feasibility of loading KMs into chitosan nanocapsules, diameter analysis was performed by dynamic light scattering (DLS, Wyatt) with the following: KMs loaded into chitosan nanocapsules (CS-KM), KMs mixed with unloaded chitosan nanocapsules, free chitosan nanocapsules (CS-NP), and free KM. DLS of unloaded CS-NP showed diameters of 148.5±0.3 nm, while KMs are 14.9±1.5 nm (Fig. 1Ai, ii). Nanoparticles of this size have been reported to pass through intestinal Peyer's patches, then into systemic circulation5. DLS results of the mixed condition shows both particle populations (Fig. 1Aiii), whereas loading KMs within CS-NPs removes free KMs (Fig. 1Aiv), demonstrating encapsulation within CS-NPs. TEM micrographs of KMs and CS-NP (Fig. 1B,1C) show spherical morphology. Kidney sections from PKD mice show smaller kidney size in the CS-NP group compared to free met (Fig. 1D). A lower reduction of kidney to body weight and cystic index was seen in CS-NP met groups compared to free met (Fig. 1E). This may be due to the reported intestinal permeation effects of chitosan5. These initial studies show promise that KMs can be loaded within CS-NPs to be an orally delivered nanotherapeutic. Oral gavage of CS-NP met showed higher efficacy in a PKD mouse model compared to free met. Currently, studies confirming KM morphology preservation within CS-NPs are being conducted and future studies will test CS-KM in diseased PKD mouse models. To our knowledge, our studies represent the first nanomedicine strategy for PKD.