Temoporfin targets tumor cells through its accumulation in neoplastic tissues and activation by light. Upon exposure to light at 652 nm, temoporfin generates reactive oxygen species (ROS), including singlet oxygen and free radicals, which cause oxidative damage to cellular membranes, mitochondria, and DNA. This leads to tumor cell necrosis and apoptosis, as well as vascular shutdown in the tumor microvasculature.

Studies using confocal fluorescence microscopy on adenocarcinomas have revealed that temoporfin is mostly found in the Golgi apparatus and endoplasmic reticulum, with limited localization in lysosomes and mitochondria [1].
In vitro, temoporfin is a potent photosensitizer that generates reactive oxygen species upon light activation. Its activity is assessed by measuring ROS production, cellular uptake, and phototoxicity in cancer cell lines. The compound shows selective accumulation in tumor cells and high phototoxic activity, with minimal dark toxicity. Its efficacy is dependent on light dose and oxygen availability.

After 4 hours, the amount of temoporfin (0.1–0.3 mg/kg) in the liver tissue dropped off quickly, however 48 hours later, the amount in the tumor tissue stayed high.
In vivo, temoporfin is used clinically for photodynamic therapy of head and neck cancers under the brand name Foscan. The compound is administered intravenously and accumulates preferentially in tumor tissues. After a drug-light interval of 4-6 days, the tumor is irradiated with laser light at 652 nm, activating the photosensitizer and inducing tumor necrosis. Clinical studies have demonstrated efficacy in palliative and curative settings.

In vitro enzyme/receptor binding assays are not applicable for temoporfin as it is a photosensitizer rather than an enzyme inhibitor. The compound's mechanism is based on photochemical generation of reactive oxygen species rather than receptor binding. Its photophysical properties, including absorption spectrum, singlet oxygen quantum yield, and fluorescence quantum yield, are characterized by spectroscopic methods.

In vitro cell-based assays for temoporfin assess its phototoxic activity in cancer cell lines. Cells are incubated with serial dilutions of the compound, allowed to accumulate the photosensitizer, and then irradiated with light at 652 nm. Cell viability is measured using MTT or other assays. Dark toxicity is assessed in non-irradiated cells. ROS production is measured using fluorescent probes.

In vivo animal models for temoporfin include mouse xenograft models of head and neck cancer and other tumor types. The compound is administered intravenously, and after a drug-light interval, the tumor is irradiated with laser light at 652 nm. Tumor growth, necrosis, and survival are evaluated. Pharmacokinetic studies measure drug distribution and clearance.

Absorption, Distribution and Excretion
Peak time (Tmax) is reached 2–4 hours after intravenous administration. Plasma concentration initially decreases rapidly, then slowly rises to peak serum concentration. Limited data are available regarding human elimination. Animal data show that temopofen is eliminated solely by the liver, with its two conjugated metabolites excreted via bile. Enterohepatic circulation of these metabolites has not been observed. Volume of distribution is 0.34–0.46 L/kg. Temopofen is known to distribute in tissues and preferentially accumulate in tumor tissue. The clearance of temopofen is 3.9–4.1 mL/h/kg. Metabolisms/Metabolites The exact metabolic response of temopofen is unknown. Drug metabolites have been identified as conjugates, but specific information is unavailable. Biological Half-Life The terminal plasma half-life is 65 hours. Temopofen exhibits a double exponential decay in elimination, with an initial half-life of 30 hours and a terminal half-life of 61-88 hours.
Temoporfin has a molecular formula of C44H32N4O4 and a molecular weight of 680.75. It is a synthetic chlorin derivative and a second-generation photosensitizer. The compound is activated by light at 652 nm. It is administered intravenously and accumulates preferentially in tumor tissues. Pharmacokinetic parameters including half-life, clearance, and tissue distribution are documented in clinical studies.

Protein Binding
Temopofen binds to plasma proteins at a rate of 85-88%. Temopofen initially binds to and aggregates with an unknown high-density lipoprotein (HDL). After administration, approximately 70% of the drug binds to this protein. The remaining drug binds to plasma lipoproteins, with 22% binding to HDL, 4% to LDL, and 4% to VLDL. Within 24 hours of administration, temopofen redistributes to lipoproteins, with approximately 73% binding to HDL, 8% to LDL, and 3% to VLDL. After redistribution, only 17% of the drug remains bound to the unknown HDL.
The toxicity profile of temoporfin includes photosensitivity reactions, which require patients to avoid light exposure for a period after treatment. Other adverse effects include pain at the treatment site, edema, and necrosis of normal tissues. The compound is contraindicated in patients with porphyria or known hypersensitivity to porphyrins. The compound is for research use only and not for human use.

[1]. Temoporfin (Foscan®, 5,10,15,20-tetra(m-hydroxyphenyl)chlorin)--a second-generation photosensitizer. Photochem Photobiol. 2011 Nov-Dec;87(6):1240-96.

[2]. Effective treatment of liver metastases with photodynamic therapy, using the second-generation photosensitizer meta-tetra(hydroxyphenyl)chlorin (mTHPC), in a rat model. Br J Cancer. 1999 Oct;81(4):600-8.

[3]. Photodynamic therapy with conventional and PEGylated liposomal formulations of mTHPC (temoporfin): comparison of treatment efficacy and distribution characteristics in vivo. Int J Nanomedicine. 2013;8:3817-31.

Temopofen belongs to the chlorine derivative class of compounds and is a photosensitizer. Temopofen is a photosensitizer used to treat squamous cell carcinoma of the head and neck. It first received marketing authorization from the European Medicines Agency in October 2001. It is currently marketed under the brand name Foscan. Temopofen is a synthetic photosensitizing chlorine compound with photodynamic activity. After systemic administration, temopofen is distributed throughout the body and absorbed by tumor cells. Under non-thermal laser irradiation (wavelength 652 nm) in the presence of oxygen, temopofen generates highly reactive, short-lived singlet oxygen and other reactive oxygen free radicals, leading to localized damage to tumor cells. This may kill tumor cells and shrink tumor volume. Drug Indications: For the treatment of patients with advanced squamous cell carcinoma of the head and neck who have not responded to standard therapy and are not eligible for radiotherapy, surgery, or systemic chemotherapy. FDA Label: Foscan is indicated for the palliative treatment of patients with advanced squamous cell carcinoma of the head and neck who have not responded to prior therapy and are not eligible for radiotherapy, surgery, or systemic chemotherapy.

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Mechanism of Action
Temopofen is excited from its ground state to the first excited singlet state under 652 nm light irradiation. Subsequently, it is thought to undergo intersystem crossing, entering a longer-lived excited triplet state capable of interacting with surrounding molecules. Afterward, it is thought to produce cytotoxic substances through type I or type II reactions commonly used in photodynamic therapy. Type I reactions involve the excited-state photosensitizer transferring hydrogen atoms or electrons to the substrate molecule, thereby generating free radicals or free radical ions. Type II reactions involve similar reactions, but with oxygen as the substrate, producing reactive oxygen species (ROS). These reactive products cause oxidative damage to cancer cells, ultimately leading to cell death. There is evidence that temopofen photodynamic therapy can activate macrophages and enhance their phagocytic activity. These activated macrophages also produce more tumor necrosis factor-α (TNF-α) and nitric oxide (NO). It is believed that enhanced macrophage activity improves therapeutic efficacy by phagocytizing cancer cells and enhancing TNF-α-mediated cell death signaling. Increased NO production may promote oxidative damage through reactive nitrogen species.

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Pharmacodynamics
Temopofen is a photosensitizer. After entering cancer cells, it is activated by light to produce reactive oxygen species, thereby destroying the cancer cells.

Temoporfin is a second-generation photosensitizer used in photodynamic therapy (PDT) for the treatment of head and neck cancers. It is also known as m-THPC and marketed as Foscan. The compound is activated by light at 652 nm, generating reactive oxygen species that induce tumor cell death. Temoporfin accumulates preferentially in tumor tissues and is activated after a drug-light interval of 4-6 days. It is used for research purposes.

C44H32N4O4

680.75

680.242

122341-38-2

60751

Purple to black solid powder

1.4±0.1 g/cm3

1.735

9.17

6

6

4

52

1090

0

LYPFDBRUNKHDGX-UHFFFAOYSA-N

InChI=1S/C44H32N4O4/c49-29-9-1-5-25(21-29)41-33-13-15-35(45-33)42(26-6-2-10-30(50)22-26)37-17-19-39(47-37)44(28-8-4-12-32(52)24-28)40-20-18-38(48-40)43(36-16-14-34(41)46-36)27-7-3-11-31(51)23-27/h1-17,19,21-24,46-47,49-52H,18,20H2

3-[10,15,20-tris(3-hydroxyphenyl)-2,3,22,24-tetrahydroporphyrin-5-yl]phenol

EF 9; mTHPC; m-THPC

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: (1). This product requires protection from light (avoid light exposure) during transportation and storage.  (2). Please store this product in a sealed and protected environment (e.g. under nitrogen), avoid exposure to moisture.

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

DMSO : ~20.83 mg/mL (~30.60 mM)

Solubility in Formulation 1: ≥ 1 mg/mL (1.47 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 10.0 mg/mL clear DMSO stock solution to 400 μL of PEG300 and mix evenly; then add 50 μL of Tween-80 to the above solution and mix evenly; then add 450 μL of 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: ≥ 1 mg/mL (1.47 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 10.0 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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 (Please use freshly prepared in vivo formulations for optimal results.)