(T0930-12-81) Long-Acting Drug Delivery System for Subcutaneous, Intravitreal, and Intra-articular Administration using Hyaluronic Acid-Based In Situ Gelling Nanosuspension Formulation of Water-Insoluble Drugs

Purpose: Long-acting injectable formulations are in high demand in the market due to their beneficial attributes in terms of decreasing dosing frequency, reducing side effects, and improving patient adherence. However, certain challenges such as time-consuming manufacturing processes, initial burst release and dose limitations restrict their broad application. In our research group, we have developed cholesterol-modified hyaluronic acid (CHHA) that forms nano-sized hydrogels (HA nanogels, branded as Sonanos^TM) in water. The nanogels possess versatile encapsulation properties for small-sized molecules, middle-sized molecules, peptides (including cyclic peptides), and proteins. Furthermore, the HA nanogels exhibit a unique colloidal property in which nanogel-clustering precipitates are formed in response to high ionic strength in the body. This salt-responsive behavior enables in situ gelation, leading to sustained release of substances such as recombinant human growth hormone (rhGH) and cyclic peptides in rats for up to one week¹⁾. We designed a dual-drug delivery system for long-acting formulations. The system consists of a dissolution-controlled drug release system based on poorly water-soluble nanocrystals and an in situ gelation drug release system using HA nanogels. Previous studies have demonstrated that combining HA nanogels with nanocrystals can suppress the initial burst release after subcutaneous administration and maintain blood concentrations for one month. In this study, we conducted additional experiments to validate the prolonged release capability following subcutaneous administration. Moreover, we investigated the sustained release in both the vitreous body and joint cavity.

Methods: Cyclosporine A (CyA) was dispersed in an aqueous solution containing 10 mg/mL Polysorbate 80 and milled using zirconium oxide beads with a diameter of 0.2 mm for 11 days. The suspension was washed twice with water using centrifugation. The particle size and concentration of the nanocrystals were analyzed with DLS RP-HPLC. The in situ gelling nanosuspensions were prepared by dispersing the desired amounts of nanocrystal into the HA nanogel (Mw of HA: 35k, Degree of substitution of cholesterol: 19%) with 9% sucrose. Subsequently, the in situ gelling nanosuspensions with HA nanogel, nanosuspensions with Poloxamer 388, and nanosuspensions without HA nanogel were subcutaneously injected into 6-week-old male Sprague-Dawley rats using a 25-gauge needle at a dose of 22 mg/kg as CyA. Blood samples were collected from the jugular vein, and CyA levels in plasma were determined using LC-MS/MS. For intravitreal administration, a 40 mg/mL CyA in 0.02 mL (0.01 mL in the right eye and 0.01 mL in the left eye) was administered to male Sprague-Dawley rats using a 28-gauge needle. CyA levels in plasma were measured using LC-MS/MS. Similarly, for intra-articular administration, a 40 mg/mL CyA equivalent in 0.02 mL (0.01 mL in the right knee and 0.01 mL in the left knee) was administered to rats using a 28-gauge needle, and plasma concentrations were measured using LC-MS/MS.

Results: After bead milling, CyA nanocrystals with a diameter of 171 nm were successfully formulated. In situ gelling nanosuspensions containing 10 mg/mL CyA were prepared by simply dispersing the nanocrystals into 5 mg/mL HA nanogel solutions. These formulations were milk-like colloidal suspensions and could pass through a 31G needle. The pharmacokinetic (PK) profile of CyA after subcutaneous administration is shown in Figure 1. The in situ gelling nanosuspension formulations maintained plasma CyA concentrations within a narrow range over a period of 3 months without initial burst, in contrast to the nanosuspension formulations containing Poloxamer 388 or without HA nanogel, which exhibited an initial burst release. The PK profiles of CyA after intravitreal administration are shown in Figure 2. The in situ gelling nanosuspension formulations containing HA nanogel also suppressed the initial burst release. Similarly, for intra-articular administration, the in situ gelling nanosuspension formulations containing HA nanogel suppressed the initial burst release (Figure 3). However, in intra-articular administration, the maximum plasma concentration exhibited higher values compared to intravitreal administration.

Conclusion: Based on the results above, we have concluded that the formulation of in situ gelling nanosuspension with HA nanogel has tremendous potential to suppress the initial burst and enhance the sustained release of drugs over a prolonged period, not only after subcutaneous administration but also after intravitreal and intra-articular administration. We believe that this dual-drug delivery system utilizing HA nanogel can realize long-acting injectable formulations and have a significant impact on the lives of patients and their families.

References: 1) Macromol Biosci. 2012 Apr;12(4):475-83.

PK profiles of in situ gelling nanosuspension of CyA after subcutaneous administration.

PK profiles of in situ gelling nanosuspension of CyA after intravitreal administration.

PK profiles of in situ gelling nanosuspension of CyA after intra-articular administration.