Optimized nanosuspensions enhanced the solubility and in vivo efficacy of a multi-functional prodrug for treating nitrogen mustard skin burns
Creators: name: Roldan, Tomas
Publisher: name: No Publisher Supplied
Year: 2024

description: In response to chemical threats, the development of effective countermeasures is a critical field of research. Sulfur mustard (SM), also known as mustard gas, has been used in a vast array of chemical attacks on civilians and soldiers and has been deployed as recently as the past decade. Nitrogen mustard (NM) is commonly used as an analog for SM due to their shared toxicity mechanisms. Both agents cause cytotoxic, mutagenic, and blistering effects on skin, and severely damage ocular and respiratory systems. NM has never been used in combat but was stockpiled by various countries during the 20th century. Many countries have since destroyed these reserves under the Chemical Weapons Convention (CWC) treaty. However, confirming the eradication of these reserves is difficult due to possible CWC non-compliance and hidden or undeclared stockpiles. NM is famously employed as a chemotherapeutic agent and is therefore synthesized and stored in pharmaceutical and experimental facilities. NM related injuries due to stockpile disassembly and pharmaceutical accidents have caused severe dermal, ocular, and pulmonary damage. There is a specific need to develop countermeasures for NM not only as a surrogate for SM, but also as a unique threat to human health. The first part of this investigation explored the shared toxicological pathways of NM and SM, with a particular focus on dermatological injuries, NM skin burn modeling, and treatment strategies. To address the inconsistency of burn development in an in-house NM skin burn model, this dissertation developed a highly reproducible and clinically relevant “depilatory double-disc” (DDD) NM mouse model. Previous NM skin burn models used organic solvents in the administration vehicle, which can increase drug dermal permeability and thus complicate interpretation of healing efficacy studies. The DDD model was the first in the scientific literature to provide clinically-relevant superficial partial-thickness burns without the use of organic solvents, thereby minimizing the number of confounding variables when screening for countermeasures. The efficacy of this model was validated through a four-times-daily (QID) dosing regimen of a lanolin/PEG400 formulation of 1% w/v NDH-4338, a highly lipophilic prodrug comprised of cyclooxygenase and acetylcholinesterase inhibitors. This validation demonstrated that the NM burns were not too severe to heal, establishing the model's utility in evaluating potential pharmacotherapy countermeasures. To address the frequent dosing regimen and suspected low dermal NDH-4338 permeability and dissolution from the viscous lanolin/PEG400 vehicle, a new formulation was designed with a higher dose concentration (2% w/v) to be administered twice daily (BID). For treating NM or SM burns in humans, a reduced dosing regimen could improve patient compliance and the overall treatment experience. This optimized NDH-4338 formulation was achieved using a design of experiments (DOE) approach, focusing on reducing the size of nanosuspensions (NSs) to enhance dissolution and NM skin burn healing. Nanosuspensions are nano-sized particles suspended in a dispersion medium that can be used to enhance the solubility of highly lipophilic compounds like NDH-4338 through an increased surface area. After an initial screening analysis to determine the primary factors that control particle size reduction, a Box-Behnken design (BBD) was constructed. After synthesizing the formulations dictated by the BBD, a predictive model was evaluated for quality by various diagnostic metrics. Two optimization approaches were applied to the model and compared to select the optimized NS parameters that resulted in a balance of the smallest particle size and lowest defect rate from the 10-50 nm specification limits. To determine the DOE's efficacy in diminishing particle size to improve dissolution, stability, and NM skin burn healing, the optimized NS was evaluated against the original NS formulation developed before the DOE. By comparing the NS formulation before and after the DOE process, it was demonstrated that the optimization process enhanced physical stability, in vitro dissolution, and NM skin burn healing efficacy using the DDD model. Improving the formulation of NDH-4338 from the lanolin/PEG400 vehicle previously used by our team allowed for significant NM skin burn healing 24 hours after vesicant administration, with a less frequent dosing regimen (BID). Given NDH-4338's unique properties for treating NM and SM skin burns and the optimized NS's enhancements in dose concentration, dissolution, and edema reduction, this optimized NS formulation could be an effective countermeasure for NM and SM skin burns in humans.