Hexaminolevulinate is an optical imaging drug. In solution form, it is instilled intravesically for use with photodynamic blue light cystoscopy as an adjunct to white light cystoscopy. After bladder instillation, hexaminolevulinate enters the bladder mucosa and is proposed to enter the intracellular space of mucosal cells where it is used as a precursor in the formation of the photoactive intermediate protoporphyrin IX (PpIX) and other photoactive porphyrins (PAPs). PpIX and PAPs are reported to accumulate preferentially in neoplastic cells as compared to normal urothelium, partly due to altered enzymatic activity in the neoplastic cells. In 2010, FDA granted approval for hexaminolevulinate hydrochloride as an optical imaging agent for cystoscopic detection of non-muscle invasive papillary cancer of the bladder for patients suspected or known to have lesion(s) on the basis of a prior cystoscopy.

Aminolevulinic Acid is the first compound in the porphyrin synthesis pathway. The metabolism of aminolevulinic acid (ALA) is the first step in the biochemical pathway resulting in heme synthesis. Aminolevulinic acid is not a photosensitizer, but rather a metabolic precursor of protoporphyrin IX (PpIX), which is a photosensitizer. The synthesis of ALA is normally tightly controlled by feedback inhibition of the enzyme, ALA synthetase, presumably by intracellular heme levels. ALA, when provided to the cell, bypasses this control point and results in the accumulation of PpIX, which is converted into heme by ferrochelatase through the addition of iron to the PpIX nucleus. Marketed under the brand name LEVULAN KERASTICK for Topical Solution plus blue light illumination using the BLU-U Blue Light Photodynamic Therapy Illuminator, it is indicated for the treatment of minimally to moderately thick actinic keratoses (Grade 1 or 2, see table 2 for definition) of the face or scalp. Aminolevulinic acid is also being studied in the treatment of other conditions and types of cancer. An orally-administered in vivo diagnostic agent, Aminolevulinic acid, is used in photodynamic diagnosis (PDD) whose aim is to help doctors visualize the tumor tissue during surgical resection of malignant glioma, it is already sold in over 20 European countries including Germany and the U.K. According to the presumed mechanism of action, photosensitization following application of aminolevulinic acid (ALA) topical solution occurs through the metabolic conversion of ALA to protoporphyrin IX (PpIX), which accumulates in the skin to which aminolevulinic acid has been applied. When exposed to light of appropriate wavelength and energy, the accumulated PpIX produces a photodynamic reaction, a cytotoxic process dependent upon the simultaneous presence of light and oxygen. The absorption of light results in an excited state of the porphyrin molecule, and subsequent spin transfer from PpIX to molecular oxygen generates singlet oxygen, which can further react to form superoxide and hydroxyl radicals. Photosensitization of actinic (solar) keratosis lesions using aminolevulinic acid, plus illumination with the BLU-UTM Blue Light Photodynamic Therapy Illuminator (BLU-U), is the basis for aminolevulinic acid photodynamic therapy (PDT).

Methoxsalen — also called xanthotoxin, marketed under the trade names Oxsoralen, Deltasoralen, Meladinine — is a drug used to treat psoriasis, eczema, vitiligo, and some cutaneous lymphomas in conjunction with exposing the skin to UVA light from lamps or sunlight. Methoxsalen modifies the way skin cells receive the UVA radiation, allegedly clearing up the disease. The dosage comes in 10 mg tablets, which are taken in the amount of 30 mg 75 minutes before a PUVA (psoralen + UVA) light treatment. Chemically, methoxsalen belongs to a class of organic natural molecules known as furanocoumarins. They consist of coumarin annulated with furan. It can also be injected and used topically. The exact mechanism of action of methoxsalen with the epidermal melanocytes and keratinocytes is not known. The best known biochemical reaction of methoxsalen is with DNA. Methoxsalen, upon photoactivation, conjugates and forms covalent bonds with DNA which leads to the formation of both monofunctional (addition to a single strand of DNA) and bifunctional adducts (crosslinking of psoralen to both strands of DNA) Reactions with proteins have also been described. Methoxsalen acts as a photosensitizer. Administration of the drug and subsequent exposure to UVA can lead to cell injury. Orally administered methoxsalen reaches the skin via the blood and UVA penetrates well into the skin. If sufficient cell injury occurs in the skin, an inflammatory reaction occurs. The most obvious manifestation of this reaction is delayed erythema, which may not begin for several hours and peaks at 48–72 hours. The inflammation is followed, over several days to weeks, by repair which is manifested by increased melanization of the epidermis and thickening of the stratum corneum. The mechanisms of therapy are not known. In the treatment of vitiligo, it has been suggested that melanocytes in the hair follicle are stimulated to move up the follicle and to repopulate the epidermis. In the treatment of psoriasis, the mechanism is most often assumed to be DNA photodamage and resulting decrease in cell proliferation but other vascular, leukocyte, or cell regulatory mechanisms may also be playing some role. Psoriasis is a hyperproliferative disorder and other agents known to be therapeutic for psoriasis are known to inhibit DNA synthesis. The most commonly reported side effect of methoxsalen alone is nausea, which occurs with approximately 10% of all patients. This effect may be minimized or avoided by instructing the patient to take methoxsalen with milk or food, or to divide the dose into two portions, taken approximately one-half hour apart. Other effects include nervousness, insomnia, and psychological depression.

Lemuteporfin is a newly introduced, light-sensitive drug for use in combination photodynamic therapy (PDT). It acts on mitochrondria to initiate the apoptotic cascade resulting in cell death (apoptosis). The photosensitizer was highly potent, killing cells at low nanomolar concentrations upon exposure to activating light. The cellular uptake of lemuteporfin was rapid with maximum levels reached within 20 min. Mitogen-activated lymphoid cells accumulated more of the lemuteporfin than their quiescent equivalents, supporting selectivity. Lemuteporfin had been in phase II clinical trials for the treatment of benign prostatic hypertrophy. It is in phase I clinical trials for the treatment of acne rosacea.

Ciaftalan Zinc (also known as Zinc(II)-phthalocyanine) is phthalocyanine and photosensitizers which showed a high activity in photodynamic therapy studies on a variety of animal tumors. Ciaftalan Zinc belongs to second generation photosensitizers that have a more intense long wavelength absorption and greater extinction coefficient compare to the first generation. The greater the extinction coefficient value associated with greater efficacy, smaller drug dosage required to induce a cytotoxic response and diminished risk of provoking systemic toxic reactions. The long absorption wavelength correlates with higher penetration depth and it is, therefore, Ciaftalan Zinc causes deep tumor necrosis in animal models. Currently, Tetra-triethyleneoxysulfonyl substituted Ciaftalan Zinc derivatives are studied as novel photodynamic therapy of cancer.

2-(1-Hexyloxyethyl)-2-devinyl pyropheophorbide-a (HPPH), a chlorin-based photosensitize, is used in photodynamic therapy. It has been shown the therapeutic potential of HPPH in phase II clinical trials for the treatment of esophageal cancer. Besides, HPPH participated in clinical trials in treating patients with advanced non-small cell lung cancer that blocks the air passages. However, these studies were terminated.

Rostaporfin (SnET2, Purlytin, REM-001), a second generation photosensitizer drug, that was developed as part of Miravant's PhotoPoint photodynamic therapy (PDT) program, for the potential treatment of wet age-related macular degeneration (AMD). It was found a red light with a wavelength of 664 nm activated the drug. It is injected into the patient, where it distributed and selectively bound to plasma lipoproteins, which were produced in high concentrations by hyperproliferating cells such as cancer cells. In January 2002, results of phase III trials indicated that rostaporfin had not met the primary efficacy endpoint for the wet form of AMD. In addition, rostaporfin has been studied in phase 2 and/or Phase 3 clinical trials in cutaneous metastatic breast cancer (CMBC). It was shown that the drug was able to reduce or eliminate a substantial number of treated CMBC tumors. On March 1, 2018, Adgero Biopharmaceuticals Holdings, Inc. announced that the U.S. Food and Drug Administration (“FDA”) has granted Orphan Drug Designation to REM-001 (rostaporfin), for the treatment of Basal Cell Carcinoma Nevus Syndrome (“BCCNS”). BCCNS is a rare but serious condition with few available therapies and many patients lack treatment options.

Methyl aminolevulinate is a prodrug that is metabolised to Protoporphyrin IX (a photosensitizer) used in photodynamic therapy. Photosensitization following application of methyl aminolevulinate cream occurs through the metabolic conversion of methyl aminolevulinate (prodrug) to photoactive porphyrins (PAP), which accumulates in the skin lesions to which the cream has been applied. When exposed to light of appropriate wavelength and energy, the accumulated photoactive porphyrins produce a photodynamic reaction, resulting in a cytotoxic process dependent upon the simultaneous presence of oxygen. The absorption of light results in an excited state of porphyrin molecules, and subsequent spin transfer from photoactive porphyrins to molecular oxygen generates singlet oxygen, which can further react to form superoxide and hydroxyl radicals. Methyl aminolevulinate is used for topical use, in combination with 570 to 670 nm wavelength red light illumination, in the treatment of non-hyperkeratotic actinic keratoses of the face and scalp in immunocompetent patients when used in conjunction with lesion preparation (debridement using a sharp dermal curette).

Talaporfin (INN, also known as aspartyl chlorin, mono-L-aspartyl chlorin e6, NPe6, or LS11) is a photosensitizer used in photodynamic therapy (PDT). Talaporfin is injected into tumors and other regret tissues where it accumulates. It’s activated with light emitting diodes (LED). It absorbs red light at 664-667 nm normally provided by a laser tuned to this wavelength. It was approved in Japan (in 2004) for PDT of lung cancer and glioma and marketed as Laserphyrin. Clinical and preclinical studies indicate that talaporfin sodium treatment may offer a powerful option to synergize current therapies, as well as an alternative monotherapy in treating cancer.