Polymeric micelles for cutaneous delivery of the hedgehog pathway inhibitor TAK-441: Formulation development and cutaneous biodistribution in porcine and human skin.

TAK-441 is a potent inhibitor of the hedgehog pathway (IC50 4.4 nM) developed for the treatment of basal cell carcinoma that is active against the vismodegib-resistant Smoothened receptor D473H mutant. The objective of this study was to develop a micelle-based formulation of TAK-441 using D-α-Tocopherol polyethylene glycol 1000 succinate (TPGS) and to investigate its cutaneous delivery and biodistribution. The micelles were prepared using solvent evaporation and incorporation of TAK-441 in the TPGS micelles increased aqueous solubility ∼40-fold. The optimal formulation, a 3% HPMC hydrogel of TAK-441 loaded TPGS micelles, retained ∼92% of the initial TAK-441 content (2.5 mgTAK-441/g) after storage at 4 °C for 6 months. Finite dose experiments using human skin demonstrated that this formulation resulted in significantly greater cutaneous deposition of TAK-441 after 12 h than a non-micelle control formulation, (0.40 ± 0.11 µg/cm2 and 0.05 ± 0.02 µg/cm2, respectively) - no transdermal permeation was observed. The cutaneous biodistribution profile demonstrated that TAK-441 was predominantly delivered to the viable epidermis and upper dermis. Delivery from the HPMC hydrogel formulation resulted in TAK-441 epidermal concentrations that were several thousand-fold higher than the IC50, with almost negligible transdermal permeation, thereby decreasing the risk of systemic side effects in vivo.

Effect of mRNA Delivery Modality and Formulation on Cutaneous mRNA Distribution and Downstream eGFP Expression.

In vitro transcribed messenger ribonucleic acid (mRNA) constitutes an emerging therapeutic class with several clinical applications. This study presents a systematic comparison of different technologies-intradermal injection, microneedle injection, jet injection, and fractional laser ablation-for the topical cutaneous delivery of mRNA. Delivery of Cy5 labeled mRNA and non-labeled enhanced green fluorescent protein (eGFP) expressing mRNA was investigated in a viable ex vivo porcine skin model and monitored for 48 h. Forty 10 µm-thick horizontal sections were prepared from each skin sample and Cy5 labeled mRNA or eGFP expression visualized as a function of depth by confocal laser scanning microscopy and immunohistochemistry. A pixel-based method was used to create a semi-quantitative biodistribution profile. Different spatial distributions of Cy5 labeled mRNA and eGFP expression were observed, depending on the delivery modality; localization of eGFP expression pointed to the cells responsible. Delivery efficiencies and knowledge of delivery sites can facilitate development of efficient, targeted mRNA-based therapeutics.