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Psoriasis is an autoimmune disorder disease with abnormally activated T lymphocytes and thickening of the epidermis. The mechanism of the action of tacrolimus and paclitaxel are matched with the two only known pathogenesis of psoriasis. However, there has been no report on tacrolimus combined with paclitaxel in the treatment of psoriasis until now. The O/O ointment was prepared for the topical application to overcome poor solubility, poor skin penetration, and erratic absorption of the two drugs. A high-speed shearing method was adopted to prepare the ointment, in which propylene carbonate was used to solve tacrolimus and paclitaxel completely. The ointment showed excellent stability, slow release of the drugs, better retention in psoriatic skin, and good skin tolerance. The therapeutic efficacy of ointment was evaluated with imiquimod induced psoriatic model, and the level of expression of psoriatic biochemical markers was evaluated using the PASI score and immunohistochemistry. The cumulative PASI score was 10.8 for the imiquimod induced group, 7.8 for the tacrolimus ointment group, 8.3 for the paclitaxel ointment and 5.3 for the tacrolimus-paclitaxel (1:1) ointment group, respectively. Ointment group with tacrolimus and paclitaxel indicated a significant improvement in the phenotypic features of the psoriatic skin treated. Compared with the imiquimod group, tacrolimus-paclitaxel (1:1) ointment group was significantly reduced the level of IL-17. The results confirm that tacrolimus and paclitaxel co-loaded ointment can be an effective strategy for the treatment of psoriasis., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Psoriasis is an autoimmune disorder disease with pink-colored plaques and excessive proliferation which is hard to be cured completely. The study focuses on the anti-psoriatic efficacy of O/O paclitaxel ointment which can promote the assembly of microtubules and lead to death of overproliferation cells of the psoriasis epidermal. A high-speed shearing method was adopted in preparing the ointment, in which propylene carbonate was used as the internal oil phase to solve paclitaxel completely. It was characterized by the appearance, particle size, rheological behavior, and in vitro release. The amount of paclitaxel retained in normal skin and psoriatic skin was 1.00 ± 0.50 versus 1.53 ± 0.48 μg/g for 0.03% PTX ointment, 1.30 ± 0.39 versus 2.77 ± 0.49 μg/g for 0.1% PTX ointment, and 2.22 ± 0.92 versus 6.65 ± 0.87 μg/g for 0.3% PTX ointment, respectively, which implied that paclitaxel could better retain in inflamed skin than in normal skin; also the amount of drug retained in the skin was proportional to drug content. Paclitaxel ointment displayed good topical tolerance after repeated application on normal mice skin. The therapeutic efficacy of paclitaxel ointment was evaluated with an imiquimod-induced psoriatic model. A significant improvement has been shown both in the phenotypic and histopathological features of psoriatic skin treated with the ointment. There was also a significant reduction in the epidermal thickness compared to the imiquimod group. The findings confirm that the O/O PTX ointment without any surfactant appears to be a promising approach for the treatment of psoriasis.