Tapinarof directly binds to the AhR pathway to initiate it. AhR nuclear translocation is dose-dependently induced by tapinarof in immortalized keratinocytes (HaCaT) (EC50=0.16 nM)[1].

In mice treated with IMQ, tapinarof reduces inflammation by acting through AhR. In C57Bl/6 background, AhR-sufficient mice show a lower clinical score following treatment with 6-formylindolo(3,2-b)carbazole (FICZ) or Tapinarof. Conversely, Tapinarof's anti-inflammatory actions had little effect on AhR KO mice. These experiments use FICZ as a comparator, and the results are similar: wild-type mice, but not AhR KO mice, have significantly lower inflammatory responses[1].

Kinetic binding experiments (fluorescence-based assay)[1]
Intrinsic fluorescence signals of 100 nM compound were monitored using the BioTek Synergy 4 microplate reader (310 nm excitation/400 nm emission) in black 96-well plates. Increasing concentrations of human or mouse AHR-ARNT protein complexes were mixed with 100 nM compound in 20 mM Tris (pH 8.0), 400 mM NaCl buffer. Fluorescence was measured and Kd values were calculated by fitting the curves in GraphPad Prism 6.

Tapinarof (GSK2894512) is a naturally derived topical treatment with demonstrated efficacy for patients with psoriasis and atopic dermatitis, although the biologic target and mechanism of action had been unknown. We demonstrate that the anti-inflammatory properties of tapinarof are mediated through activation of the aryl hydrocarbon receptor (AhR). We show that tapinarof binds and activates AhR in multiple cell types, including cells of the target tissue-human skin. In addition, tapinarof moderates proinflammatory cytokine expression in stimulated peripheral blood CD4+ T cells and ex vivo human skin, and impacts barrier gene expression in primary human keratinocytes; both of these processes are likely to be downstream of AhR activation based on current evidence. That the anti-inflammatory properties of tapinarof derive from AhR agonism is conclusively demonstrated using the mouse model of imiquimod-induced psoriasiform skin lesions. Topical treatment of AhR-sufficient mice with tapinarof leads to compound-driven reductions in erythema, epidermal thickening, and tissue cytokine levels. In contrast, tapinarof has no impact on imiquimod-induced skin inflammation in AhR-deficient mice. In summary, these studies identify tapinarof as an AhR agonist and confirm that its efficacy is dependent on AhR.[1]

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Mice[1] Female BALB/c mice (BALB/cByJRj) are used. Studies are performed using 100 μL of Tapinarof (1%) or FICZ (0.01%, at the limit of solubility) in 60% ethanol: 40% water[1].

Absorption, Distribution and Excretion
No accumulation was observed with repeat topical application. Plasma concentration of tapinarof was below the quantifiable limits (BQL) of the assay (lower limit of quantification was 50 pg/mL) in 68% of the pharmacokinetic samples. On Day 1, mean ± SD values of Cmax and AUC0-last were 0.90 ± 1.4 ng/mL and 4.1 ± 6.3 ng.h/mL, respectively, following a mean daily dose of 5.23 g applied to a mean body surface area involvement of 27.2% (range 21 to 46%) in 21 subjects with moderate to severe plaque psoriasis. On Day 29, the mean ± SD Cmax and AUC0-last were 0.12 ± 0.15 ng/mL and 0.61 ± 0.65 ng.h/mL, respectively.
The Vss of tapinarof is estimated to be from 1270 to 1500 mL/kg.

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Metabolism / Metabolites
Tapinarof is metabolized in the liver by multiple pathways including oxidation, glucuronidation, and sulfation in vitro.CYP1A2 and CYP3A4 appears to be the major enzyme involved in the hepatic metabolism of tapinarof, while CYP2C9, CYP2C19, and CYP2D6 play a minor role.

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Biological Half-Life
Due to the insufficient data about the elimination phase, the terminal half-life of tapinarof cannot be determined.

Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
Tapinarof has not been studied during breastfeeding. Because it is poorly absorbed after topical application, it is considered a low risk to the nursing infant. Do not apply tapinarof directly to the nipple and areola and ensure that the infant's skin does not come into direct contact with the areas of skin that have been treated.
◉ Effects in Breastfed Infants
Relevant published information was not found as of the revision date.
◉ Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.

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Protein Binding
Human plasma protein binding of tapinarof is approximately 99% in vitro.

[1]. Tapinarof Is a Natural AhR Agonist that Resolves Skin Inflammation in Mice and Humans. J Invest Dermatol. 2017 Oct;137(10):2110-2119.

Benvitimod is a stilbenoid.
Tapinarof is a novel, first-in-class, small-molecule AhR agonist that is indicated for the treatment of adult psoriasis. It is available as a topical cream to be applied to the affected area once daily. Tapiranof was first discovered as a metabolite (3,5-dihydroxy-4-isopropylstilbene) produced in Photorhabdus luminescens, a gram-negative bacillus that lives symbiotically with the Heterorhabditis nematodes. In 1959, it was noticed that Heterorhabditis with a high amount of 3,5-dihydroxy-4-isopropylstilbene did not putrefy once dead, thus suggesting its potential anti-inflammatory activity. Tapinarof received initial approval from the FDA in 2022.
Tapinarof is an Aryl Hydrocarbon Receptor Agonist. The mechanism of action of tapinarof is as an Aryl Hydrocarbon Receptor Agonist.
3,5-Dihydroxy-4-isopropylstilbene has been reported in Photorhabdus luminescens with data available.

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Drug Indication
Tapinarof is indicated for the topical treatment of plaque psoriasis in adults.

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Mechanism of Action
Tapinarof is a therapeutic aryl hydrocarbon receptor-modulating agent (TAMA) that binds to and activates the aryl hydrocarbon receptor (AhR). AhR is a ligand-dependent transcription factor that regulates gene expression in a variety of cell types, including macrophages, T-cells, antigen-presenting cells, fibroblasts, and keratinocytes. Upon binding to its ligand, AhR heterodimerizes with AhR nuclear translocator (ARNT) to form a complex with a high affinity for DNA binding. The AhR-ligand/ARNT complex can then bind to the specific DNA recognition sites to transcribe AhR-responsive genes. Additionally, AhR also exerts its effect through other transcription factors such as the nuclear factor κB and nuclear factor erythroid 2-related factor 2 (Nrf2), a downstream product of AhR-induced transcription that has antioxidant properties. Dysregulation of AhR is one of the hallmarks of psoriasis, as psoriasis patients have a higher serum concentration of AhR compared to healthy individuals. Treatment of AhR ligands in vitro also results in a gene expression profile that is implicated in the pathogenesis of psoriasis. For instance, AhR activation causes the expansion and differentiation of Th17 and Th22, two major T cells responsible for releasing inflammatory cytokines IL-17 and IL-22.. Additionally, AhR activation also recruits persistent skin resident memory T cells, thus contributing to the chronicity of psoriasis. However, the specific binding of tapinarof to AhR modulates a unique set of genes that are dysregulated in psoriasis, distinctive from other AhR ligands. Further, tapinarof also induces barrier protein expression, such as filaggrin, hornerin, and involucrin, to restore the skin barrier and epidermal function and decrease oxidative stress. It is currently unknown why AhR ligands like tapinarof can reduce psoriatic inflammations in one setting but upregulate inflammatory genes in another setting. It is possible that the anti-inflammatory effect of tapinarof as an AhR agonist might be due to Nrf2. Although Nrf2 is a known downstream effector of AhR, not all AhR agonists activate this pathway. For instance, 2,3,7,8-tetrachlorodibenzo-p-dioxin, an AhR agonist, does not show any antioxidant activity after AhR activation. Therefore, it is hypothesized that the dual AhR/Nrf2 action of tapinarof is essential to the effect of tapinarof in treating psoriasis.

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Pharmacodynamics
The pharmacodynamics of tapinarof are unknown.

C17H18O2

254.32362

254.131

C, 80.28; H, 7.13; O, 12.58

79338-84-4

6439522

White to light yellow solid powder

1.158

4.391

2

2

3

19

280

0

C(/C1C=C(O)C(C(C)C)=C(O)C=1)=C\C1C=CC=CC=1

ZISJNXNHJRQYJO-CMDGGOBGSA-N

InChI=1S/C17H18O2/c1-12(2)17-15(18)10-14(11-16(17)19)9-8-13-6-4-3-5-7-13/h3-12,18-19H,1-2H3/b9-8+

3,5-Dihydroxy-4-isopropylstilbene

GSK-2894512; WB-1001; tapinarof; WBI-1001; WB1001; WBI 1001; GSK 2894512; GSK2894512; 3,5-DH4IS; 3,5-Dihydroxy-4-isopropylstilbene; Vtama

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: This product requires protection from light (avoid light exposure) during transportation and storage.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~100 mg/mL (~393.21 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (9.83 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (9.83 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (9.83 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)