(T1130-06-34) In Vitro Topical and Transdermal Delivery of 4-Phenylbutyric Acid Emulsome Loaded Foam Formulation for the Treatment of Chemical Warfare Agent-Induced Skin Injury

Purpose: Chemical warfare agents represent a significant public health threat upon incidental exposure, with Lewisite being particularly hazardous. This arsenical compound induces severe burning and erythema, rapidly progressing to persistent and painful blistering. Recent research highlights 4-phenylbutyric acid (4-PBA) as a novel and effective agent for mitigating Lewisite-induced skin injuries and alleviating subsequent pain and inflammation. Although 4-PBA is already FDA-approved for urea cycle disorders, studies have demonstrated its ability to block unfolded protein response (UPR) signaling pathways, thereby reducing endoplasmic reticulum (ER) stress and promoting skin healing. This study aimed to develop a 4-PBA-loaded emulsome incorporated into a topical foam (F30) for sustained delivery of 4-PBA. This innovative formulation ensures efficient and prolonged release of the active compound, optimizing its therapeutic effects. The emulsome formulation enhances the stability and bioavailability of 4-PBA, providing an advanced delivery system capable of mitigating skin injuries caused by arsenicals. Additionally, the foam facilitates effective decontamination by adhering to skin surfaces and spreading easily. This feature is crucial for promptly removing phenylarsine oxide (PAO), a lewisite surrogate from the skin, thereby reducing exposure and minimizing potential harm. The non-greasy residue of the foam ensures comfort during application, making it suitable for treating sensitive or inflamed skin resulting from chemical exposure. By integrating emulsomes into the formulation, the study not only improves therapeutic outcomes but also enhances patient compliance in emergency response situations.

Methods: Emulsomes (E1-E10) were formed using the thin film hydration method. Various ratios of drug, stearic acid, cholesterol, and soya lecithin are initially solubilized in chloroform as shown in  Table 1. This solution is then subject to vacuum for approximately 1 hour to form the thin film. The film of nanoparticles obtained after evaporation of the organic phase was then hydrated using phosphate buffer(PBS) overnight. The formed emulsomes are then filtered, lyophilized, and evaluated for drug loading, particle size, polydispersity index (PDI), entrapment efficiency. E2 emulsome was then chosen for additional studies. E2 emulsomes were then embedded into a topical foam (F30) comprised of 5% v/v of oleic acid, 10% v/v ethanol, 20% v/v sodium lauryl ether sulfate (SLES), 70% v/v of propylene glycol. The continued assesment of E2 loaded foam formulations included in vitro permeation testing (IVPT). IVPTs were conducted using vertical Franz diffusion cells and dermatomed human skin (n=4). E2 incorporated in F30 and PBS were applied to the skin at an infinite does of 200µL (1.5mg/mL) and evaluated against unecapsulated drug in similar vehicles as a control. 300uL receptor samples taken up to 24h at predetermined times and skin samples were then analyzed for 4-PBA using a previously validated HPLC method.

Results: Emulsomes were prepared according to the process outlined in Figure 1 and were subsequently characterized. Among these formulations, E2 exhibited promising characteristics including desirable drug loading(17%), zeta potential (~-40mV), particle size (mean diameter: 212 ± 26 nm, n=10), and good drug yield leading to further characterization. 4-PBA inherently has high permeability across the skin due to the moderate lipophilicity of the drug itself, therefore 4-PBA in the foam served as the control in this study. The intention of this study was to sustain the delivery of 4-PBA via encapsulation in a biocompatible nanoparticle. The total delivery of 4-PBA in F30 was observed to have significantly higher total delivery (206.64± 14 µg/cm²)(p=0.0395) compared to the 4-PBA encapsulated emulsome in F30 (151.6± 10 µg/cm²). The emulsome shows a significantly lower delivery as compared to the control shown in Figure 2A. When looking at the release profile of 4-PBA in foam, the control depicted an average release of up to 78.87±6.56% after 24h while E2 showed 29.76±4.56% release, demonstrating the sustained release of the emulsome shown in Figure 3D. Decontamination efficiency was also evaluated in this study. The decontamination for the nanoparticle containing foam formulation showed to have no significant difference in comparison to the blank foam shown in Figure 2B. This suggests that the foam maintains its decontamination efficiency and while the emulsome improves the decontamination efficiency it is not a significant difference. The foam continued to maintain its ease of application, and avoidance of excessive rubbing on irritated skin for effective delivery.

Conclusion: 4-PBA loaded emulsomes were successfully formulated characterized, and incorporated into a topical foam (F30). The emulsomes demonstrated sustained delivery of 4-PBA across dermatomed human skin for up to 24 hours. The foam was demonstrated to be unchanged with the addition of emulsomes, and capable of being a preferred vehicle for avoiding skin irritation as the rubbing motion is not needed for delivery. As shown, this study indicates the viability of developing a 4-PBA emulsome loaded foam formulation for the sustained delivery of 4-PBA in order to alleviate arsenical-induced skin injury.

References: 1. Dandekar A, Vora D, Yeh JS, Srivastava RK, Athar M, Banga AK. Enhanced Transdermal Delivery of N-acetylcysteine and 4-phenylbutyric acid for Potential Use as Antidotes to Lewisite AAPS PharmSciTech. AAPS PharmSci Tech. 2023
2. Vora D, Dandekar AA, Srivastava RK, Athar M, Banga AK. Development and Evaluation of a Topical Foam Formulation for Decontamination of Warfare Agents. Mol Pharm. 2022
3. Li C, Srivastava R, Weng Z, Croutch C, Agarwal A, Elmets C, Afaq F, Athar M. Molecular Mechanism Underlying Pathogenesis of Lewisite-Induced Cutaneous Blistering and Inflammation: Chemical Chaperones as Potential Novel Antidotes. AJOP. 2016.

Acknowledgements: This project was supported by NIH/NIAMS U01AR078544 to M.A.

Table 1. Formulation matrix for 4-PBA loaded emulsome

Figure 1. Schematic for emulsome formulation and characterization

Figure 2. A- Total delivery of 4-PBA loaded emulsome delivered into and across the skin. B- Decontamination efficiency of blank F30, 4-PBA in F30, and E2 in F30. C- 24h permeation profile of 4-PBA loaded emulsome, D- The release profile of 4-PBA emulsome compared to the control, E2 shows sustained release.