(W0930-06-34) Ultraflexible Liposomes Enhance Topical Delivery of ADT-007 for Potential Melanoma Therapy

Purpose: Melanoma, particularly in patients with N-RAS mutations, lacks effective topical therapies. ADT-007, a novel pan-RAS inhibitor, selectively binds nucleotide-free RAS to block GTP loading and downstream MAPK signaling in N-RAS-mutant cells. ADT-007 shows promise but suffers from systemic toxicity and low bioavailability [1]. This study aimed to develop ultraflexible liposomes (UFLs) encapsulating ADT-007 for topical delivery to enhance drug permeation, reduce toxicity to normal skin cells, and improve stability compared to traditional liposomes (TLs).

Methods: ADT-007-loaded UFLs were prepared via thin-film hydration using soybean phosphatidylcholine and sodium cholate (20% w/w), followed by extrusion [2]. TLs were formulated identically but without sodium cholate. Liposomes were characterized for size, polydispersity index (PDI), zeta potential, and encapsulation efficiency (EE). In vitro drug release via dialysis was carried out. Carbomer-based gels containing liposomes were prepared and evaluated for homogeneity, viscosity, and permeability (Strat-M membrane with Franz cell) [3]. Stability was tested at 4 °C and 25 °C for 6 months. Cytotoxicity and therapeutic indexes were determined using CellTiter-Glo 2.0 for human melanoma cell lines (SK MEL 2, SK MEL 28, WM852, A375, and Malme 3M), and human keratinocytes.

Results: UFLs loaded with ADT-007 had a mean size of 133.1 ± 2.1 nm, PDI of 0.13 ± 0.01, and zeta potential of −15.0 ± 2.1 mV. TLs loaded with ADT-007 showed a larger particle size of 252.7 ± 3.8 nm, higher PDI of 0.27 ± 0.02, and a less negative zeta potential of −2.2 ± 0.6 mV, indicating lower colloidal stability.EE was 83.6 ± 1.2% for UFLs, and 78.1 ± 0.9% for TLs. UFLs exhibited monophasic release reaching 74.1% in 5 hours versus 62.1% from TLs. Permeability of ADT-007 from UFL gels was 455.9 µg/cm² at 300 min versus 419.1 µg/cm² from TLs (p < 0.01). Free ADT-007 in carbomer gel could not permeate the membrane. Viscosity profiles of UFL- and TL-containing carbomer gels demonstrated shear-thinning behavior; these gels had better spreadability than the marketed LMX4 cream. Stability data indicated that UFLs retained size and EE better than TLs at 4 °C, remaining within FDA limits [4]. Cell viability assays showed ADT-007 UFLs had higher IC₅₀ values for keratinocytes and lower IC₅₀ values for melanoma cells, compared to TLs and free drug. The therapeutic index for UFLs was highest, suggesting superior selectivity.

Conclusion: ADT-007-loaded UFLs demonstrated enhanced encapsulation, release, permeation, and selectivity for melanoma cells with reduced toxicity toward keratinocytes. UFLs in carbomer gel represent a promising non-invasive topical strategy for targeted melanoma therapy, especially for N-RAS mutation-driven subtypes.

References: [1] Foote JB, Mattox TE, Keeton AB, et al. A Novel Pan-RAS Inhibitor with a Unique Mechanism of Action Blocks Tumor Growth in Mouse Models of GI Cancer. bioRxiv. 2024;doi:10.1101/2023.05.17.541233
[2] Sun M, Osipitan OO, Sulicz EK, Di Pasqua AJ. Preparation and Optimization of an Ultraflexible Liposomal Gel for Lidocaine Transdermal Delivery. Materials (Basel). 2022;15(14)doi:10.3390/ma15144895
[3] Uchida T, Kadhum WR, Kanai S, Todo H, Oshizaka T, Sugibayashi K. Prediction of skin permeation by chemical compounds using the artificial membrane, Strat-M. Eur J Pharm Sci. 2015;67:113-118. doi:10.1016/j.ejps.2014.11.002
[4] U.S. Department of Health and Human Services FaDA, Center for Drug Evaluation and Research (CDER). Liposome drug products: chemistry, manufacturing, and controls: human pharmacokinetics and bioavailability: and labeling documentation. Silver Spring, MD: Center for Drug Evaluation and Research.https://www.fda.gov/regulatory-information/search-fda-guidance-documents/liposome-drug-products-chemistry-manufacturing-and-controls-human-pharmacokinetics.Published April 2018. Accessed April 17, 2025.

Acknowledgements: The authors declare no competing conflict of interest. This work was funded by Massachusetts College of Pharmacy and Health Sciences, Boston, MA, USA.


Figure 1 A. Comparative drug release of ADT-007 from UFLs and TLs via dialysis membrane B. Comparative drug permeability of ADT-007 from UFL gel and TL gel through Strat-M membrane


Figure 2 A. Homogeneity profiles of ADT-007 UFL gel and ADT-007 TL gel B. Viscosity profiles of ADT-007 UFL , ADT-007 TL gel and marketed LMX4 cream


Figure 3 A. Viability of melanoma cell lines and human keratinocytes with free ADT-007 B. Viability of melanoma cell lines and human keratinocytes with ADT-007 loaded UFLs C. Viability of melanoma cell lines and human keratinocytes with ADT-007 loaded TLs D. Viability of human keratinocytes