(W0930-07-39) Development and Characterization of Cannabidiol and Rho Kinase Inhibitor Combination Formulations for Ophthalmic Use

Purpose: Glaucoma, a leading cause of irreversible blindness, is a degenerative disease of the retinal ganglion cells through oxidative stress, excitotoxicity, and other mechanisms. Elevated intraocular pressure (IOP) is an important clinical presentation causing blockade of neurotrophic factors and the only addressed modifiable risk factor to prevent disease progression. Netarsudil dimesylate (NM), a rho kinase inhibitor, exerts its IOP-lowering effect by causing relaxation of the trabecular meshwork and is approved as a 0.02% w/v ophthalmic solution. Cannabidiol (CBD), one of the major cannabinoids, produces neuroprotective activity by blocking nitrotyrosine formation which is a downstream excitotoxicity and oxidative damage event. It also shows anti-inflammatory, antioxidant, and antinociceptive activity¹. Also, IOP reduction was achieved with CBD nanoemulsions (1% w/v) in normotensive pigmented Dutch-belted rabbits². NM is susceptible to hydrolytic degradation, and CBD, to oxidation and photodegradation. This work aims to formulate NM-CBD-loaded nanoemulsions (NM-CBD NEs).

Methods: NM-CBD NEs were prepared by hot homogenization-probe sonication using sesame oil (5%, lipid) stabilized by Tween^® 80 (2%, surfactant) and Poloxamer 407 NF (0.2%, co-surfactant)³ or using sesame oil (2.5%, lipid) and Gelucire^® 50/13 (2.5%, lipid/surfactant); composition indicated in Table 1. The aqueous phase comprising NM, Tween^® 80, Poloxamer 407 NF, d-α, and glycerin (2.25%, tonicity agent) in milli-Q water was added dropwise to the lipid phase comprising CBD, sesame oil, and Gelucire^® 50/13 under magnetic stirring (2000 rpm, 5 min, 70 ± 2° C), homogenized (10000 rpm, 5 min, 65 ± 2° C), and probe sonicated (10 min, pulse: 10s on-10s off, Amp 40%) to form the nanoemulsions and adjusted to pH 5 using sodium hydroxide if needed. The osmolality, droplet size (DS), polydispersity index (PDI), and drug content of NM and CBD of the NEs were characterized for 1 month (last time-point tested) in refrigerated (4° C), and accelerated conditions (25 and 40° C).

Results: The aqueous saturation solubility of NM was >30 mg/mL at pH 2-5, and < 0.01µg/mL at pH 6 and 7. The octanol-water Log D at pH 3, 4, 5, 6, and 7 were -0.07, 1.51, 2.59, 3.58, and 3.57, respectively. The osmolality of the NM-CBD NEs ranged from 260-340 mOsm/kg, within the prescribed range of 171-1711 mOsm/kg in USP-NF for ophthalmic formulations⁴. The DS and PDI for Tween^® 80 stabilized NEs F1 and F2 were 160-171 nm and 0.168-0.234, respectively, whereas for Gelucire^® 50/13 stabilized NEs F3 and F4 were 96-109 nm and 0.225-0.517, respectively (Fig. 1). The DLS intensity-size distribution of F3 and F4 suggested the presence of two droplet systems, possibly the Gelucire^® 50/13-sesame oil globules and Gelucire^® 50/13 micelles. The NEs maintained physical stability for 1 month. CBD remained stable in all formulations for 1 month under all test conditions. NM, however, was stable only in F3 for 1 month at 4° C, but significant ( >40%) degradation was observed in the remaining NEs at all temperatures within 15 days (Fig. 2).

Conclusion: Physically stable NM-CBD NEs were successfully prepared. Sesame oil-Gelucire^® 50/13-based NEs need further optimization as a vehicle for the combination of NM and CBD. Based on the physicochemical characterization of NM, the prevention of hydrolytic degradation by controlling its lipid partitioning could be investigated with appropriate lipids and pH of the aqueous phase. Future studies include optimization of the NEs for droplet size, PDI, and drug stability. In vitro release and transcorneal permeation and distribution studies will help understand the availability of the drug in ocular tissue. Further, in vivo IOP studies are needed to understand the effect of the combination on the IOP and anti-inflammatory activity in an appropriate animal model.

References: 1. Aebersold, A., Duff, M., Sloan, L. & Song, Z.-H. Cannabidiol Signaling in the Eye and Its Potential as an Ocular Therapeutic Agent. Cell Physiol Biochem 55, 1–14 (2021).
2. Senapati, S. et al. Cannabidiol Loaded Topical Ophthalmic Nanoemulsion Lowers Intraocular Pressure in Normotensive Dutch-Belted Rabbits. Pharmaceutics 14, 2585 (2022).
3. Sweeney, C. et al. Impact of mucoadhesive agent inclusion on the intraocular pressure lowering profile of Δ9-tetrahydrocannabinol-valine-hemisuccinate loaded nanoemulsions in New Zealand white rabbits. International Journal of Pharmaceutics 616, 121564 (2022).
4. USP-NF 〈771〉 Ophthalmic Products—Quality Tests. https://online.uspnf.com/uspnf/document/1_GUID-5C58E1A2-6BE7-4011-9776-64687B306810_5_en-US?source=Search%20Results&highlight=osmolarity%20ocular.

Table 1. Composition of NM-CBD Nanoemulsions.

Figure 1. Mean droplet size (d. nm) and polydispersity index of NM-CBD nanoemulsions in the stability study.

Figure 2. Drug content of netarsudil mesylate and cannabidiol (% w/v) in NM-CBD nanoemulsions in the stability study.