Novel formulation technology for the sustained release naloxone to improve outcomes in the management of opioid overdose

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PROJECT SUMMARY Opioid overdose was responsible for less than 10,000 deaths in 1999 but increased to nearly 50,000 by 2019. Data reported by the Center for Diseases Control and Prevention's National Center for Health Statistics showed that the 12-month period leading up to April 2021 had more than 100,000 drug overdose deaths and over 74,000 opioid overdose deaths. Naloxone, derived from oxymorphone, decreases the effectiveness of opioids by competitively binding to µ-opioid receptors in the central nervous system. Even though naloxone has greatly helped to reduce the number of opioid overdose deaths, individuals with opioid use disorder often experience re-narcotization when treated with naloxone because of its relatively short half-life. Moreover, high or repeated doses of naloxone are needed to counteract its rapid metabolism with higher circulating naloxone levels, which can initiate precipitated opioid withdrawal symptoms in individuals with opioid addiction. This Phase I SBIR project will develop a cationic pH/temperature-sensitive hydrogel embedded with naloxone-encapsulated anionic solid lipid nanoparticles (SLNs) as an in situ gelling subcutaneous formulation for the long-lasting release of naloxone. The proposed hydrogel technology comprises a aqueous solution of a tri-block copolymer conjugated with poly(ethylene glycol) that once injected into the patient transitions to a gel under physiological conditions. Our approach will provide a double-encapsulation strategy for naloxone that would give an additional level of control over the spatial and temporal release while improving its stability. The nanoparticle-hydrogel composite will exploit the cationic nature of a stimuli-sensitive tri-block copolymer hydrogel system to achieve strong electrostatic interactions with naloxone loaded anionic SLNs, which would prolong the degradation and circulation of SLNs and therefore the activity of the loaded cargo. The first aim is the formulation and characterization of anionic naloxone-loaded SLNs dispersed in a cationic pH/temperature sensitive tri-block copolymer hydrogel system. This includes analyzing the properties of the hydrogel system such as the sol-gel phase diagram, viscosity, mechanical properties, swelling capacity, in vitro release kinetics, in vitro enzymatic degradation, and stability. The second aim evaluates the in vivo efficacy of the hydrogel system in a fentanyl- induced rat model of opioid overdose. A successful outcome will be a therapeutic candidate with sustained naloxone release which also can prevent fentanyl-induced respiratory depression and antinociception for up to 48 h following a single subcutaneous dose.