Abstract: Human CYP2A6 has been recognized as being involved in the mutagenic activation of promutagens such as the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) Methoxsalen (8-methoxypsoralen) was reported to inhibit CYP2A6 In the present study, the inhibitory effects of methoxsalen on NNK-induced lung tumorigenesis in female A/J mice were examined Female A/J mice were treated with methoxsalen at doses of 50 or 125 mg/kg body weight, given by stomach tube, daily for 3 days One h after the final treatment, NNK was injected ip at a dose of 2 mg/mouse The experiments were terminated 16 weeks after the first methoxsalen treatment, and lung adenomas were analyzed Pretreatment of methoxsalen significantly reduced tumor incidence from 938% to 167% (50 mg/kg) and 200% (125 mg/kg), and tumor multiplicity from 597 to 023 (50 mg/kg) and 025 (125 mg/kg) tumors/mouse These results clearly demonstrated that methoxsalen, a potent human CYP2A6 inhibitor, is a strong chemopreventive agent against NNK-induction of lung tumorigenesis

Abstract: Nicotine is metabolized to the inactive metabolite cotinine by cytochrome P450 2A6. NNK, or 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, is a potent procarcinogen shown to be activated to a reactive mutagenic metabolite by the enzyme CYP2A6. We studied the effect of inhibiting CYP2A6 on smoking behavior and metabolism of the procarcinogen NNK. In study 1, abstinent smokers (n=7) received methoxsalen (a potent CYP2A6 inhibitor), 30-50 mg orally, one-half hour before three subcutaneous nicotine injections (31 microg/kg) were given at hourly intervals. Methoxsalen increased mean plasma nicotine by 47% (p<.01) and mean nicotine area under the curve (AUC) by 63% (p<.0001); and decreased nicotine clearance by 39% (p<.0001), relative to placebo. In study 2, smokers (n=11) were told to maintain their same number of cigarettes smoked while receiving methoxsalen, 10 mg orally three times daily for 3 days. On day 3 of methoxsalen treatment, a 29% increase in plasma nicotine/expired-air CO (an index of smoke exposure) (p=0.03) was observed. Urinary levels of trans 3'-hydroxycotinine (metabolized by CYP2A6 from cotinine) also were decreased (p<.0001), and significantly more NNK was metabolized to the inactive NNAL-glucuronide (1.04+/-0.54 pmol/mg on day 1 to 1.37+/-0.74 pmol/mg on day 4, p<.01) relative to placebo. Thus, treatment with the CYP2A6 inhibitor methoxsalen in vivo increases the routing of NNK to the inactive NNAL-glucuronide and decreases smoking. CYP2A6 inhibition may have potential as an exposure reduction or cessation strategy in tobacco dependence.

Abstract: We compared the characteristics of psoralen and ultraviolet A (PUVA) erythema in skin photosensitized by bath or oral methoxsalen in 20 subjects. Erythema was assessed visually and with a reflectance instrument at 24 h intervals for 7 days. In addition, narrowband ultraviolet B (TL-01 UVB) erythema was examined in 19 of these subjects at 4, 8, 12, 24, 48 and 72 h and in another nine subjects at 12, 15, 18, 21 and 24 h. Both bath and oral PUVA exhibited broad erythemal peaks beyond 72 h. For topical PUVA the lowest minimal phototoxic dose (MPD) occurred at 120 and 144 h (P = 0.01 and 0.03 compared with 72 h). Oral PUVA erythema peaked earlier at 96 h: the MPD was significantly lower at 96, 120 and 144 h compared with 72 h (P = 0.001, 0.01 and 0.02, respectively). At 120 h, bath PUVA had a significantly steeper slope compared with oral PUVA. The TL-01 UVB minimal erythema dose was significantly lower at 12 h compared with 24 h (P = 0.019). The majority of subjects were at maximal erythema at 12 h (22 of 28) and 15 h (eight of nine). Our results suggest that peak erythema for bath PUVA, oral PUVA and TL-01 UVB occurs at 120, 96 and 12-15 h, respectively.

Abstract: Background: Limited data exist in the literature concerning the characteristics of erythema following psoralen UV-A (PUVA) treatment using topical methoxsalen. To optimize the phototherapeutic regimen and reduceshort-andlong-termrisks,knowledgeofsuchbasic information is essential. Observations: The characteristics of PUVA erythema following 15- and 5-minute immersion in methoxsalen was determined. The PUVA erythema after 15-minute methoxsalenimmersionexhibitedabroadpeak,withthe lowest median minimal phototoxic dose (MPD) at 96, 120, and 144 hours after UV-A irradiation. Seventythree percent of subjects experienced peak erythema at 120 hours compared with only 45% at 72 hours. From the dose-response data, an increase in the erythema index of 0.025 (equivalent to the MPD) was significantly lower when determined at 120 hours after UV-A irradiation than at 72 hours (P=.03). The median maximum slope of the dose-response curve occurred at 144 hours. After 5-minute immersion, PUVA erythema displayed a broad peak from 72 hours. Erythema summation scores followed a trend similar to that of 15-minute immersion, but the intensity was significantly reduced. Conclusions:Methoxsalen–UV-Aerythemaexhibiteda broadplateaubetween96and144hours,withmostsubjectsatpeakerythemaat120hours.Reductionofmethoxsalen immersion time significantly lowered the erythemal intensity. Minimum phototoxic dose reading at 72 hours underestimates the phototoxic effect of topical methoxsalen PUVA, and a change in the MPD assessment time should be considered.

Abstract: Photopheresis (extracorporeal photochemotherapy) is an immunomodulatory therapy that entails the reinfusion of peripheral blood mononuclear cells after exposure to the photoreactive agent methoxsalen and ultraviolet A (UVA) radiation. Currently available at approximately 150 treatment centers worldwide, photopheresis is approved by the US FDA for advanced-stage cutaneous T-cell lymphoma (CTCL) and has also shown promise in treating nonmalignant immune-related conditions such as organ transplant rejection, acute and chronic graft-versus-host disease, and autoimmune disorders. The precise mechanism by which photopheresis evokes clinical responses is unknown, although this modality seems capable of modulating T-cell and monocyte activity. Clinical and laboratory findings suggest that the reinfusion of peripheral blood mononuclear cells after exposure to UVA-activated methoxsalen engenders an immune response against proliferating T-cell clones. Methoxsalen is a naturally occurring furocoumarin that is biologically inert until exposed to UVA radiation at the proper wavelength, at which time it irreversibly cross-links DNA thymine bases and arrests cell proliferation. T cells isolated from the peripheral blood of patients after photopheresis demonstrate significantly increased levels of apoptosis, whereas macrophages and dendritic cells exhibit the ability to phagocytize the apoptotic T cells. It is surmised that photopheresis enhances the uptake, processing, and presentation of distinctive antigens from apoptotic pathogenic T cells by macrophages and dendritic cells leading to the induction of an anticlonotypic response by cytotoxic T cells. Induction by photopheresis of apparently opposite immune processes (i.e. upregulation of an antitumor response and downregulation of allogeneic or autoimmune responses) can be explained by its ability to target either a single malignant T-cell clone (as in CTCL) or multiple activated T-cell clones (as in organ transplant rejection, graft-versus-host disease, or autoimmune disease). Because acute inflammation and T-cell activation may be important in the pathogenesis of restenosis following percutaneous transluminal coronary angioplasty (PTCA), photopheresis was used for the first time at our center to prevent restenosis. A total of 78 patients with single-vessel coronary artery disease amenable to PTCA with or without stent deployment were enrolled, 41 in the control group and 37 in the photopheresis group. Clinical restenosis occurred in significantly less photopheresis patients than control patients (8 vs 27%; p = 0.04), with a relative risk of 0.30 (95% confidence interval, 0.09-1.00). A multicenter clinical trial following a US FDA-recommended protocol is currently underway to better determine what, if any, impact photopheresis has in preventing restenosis.

Abstract: The topical photochemotherapy of dermatoses with psoralens (PUVA therapy) requires an adequate drug level at the target site (basal epidermis) at the time of UVA radiation. The aim of this work was to enhance 5-methoxypsoralen transport to the basal epidermis, with the goal to shorten the delay between drug application and UVA irradiation. 5-Methoxypsoralen transport through rabbit skin was studied in vitro from topical formulations (water solution, gel, and emulsion). The results obtained show that the use of the emulsion increased the flux through rabbit ear skin, even if partitioning was not favorable. Additionally, the time lag was sensibly reduced, compared with the gel and solution. Furthermore, drug accumulation in human skin in vitro was determined using the thin slicing technique. Human skin accumulation profile was significantly higher for the emulsion, compared with the gel, indicating that the delay between psoralen application and UVA irradiation can be shortened.

Abstract: A synthesis method for preparation of psoralen, wherein the condensed ring system includes the compound in which the oxygen atoms are the only ring hetero atoms. The invention relates to a medicinal methoxsalen, in particular the method for preparing furocoumarin compounds, wherein methoxsalen is obtained by using meta-dihydroxybenzene as initiation raw material through five-step interactive catalytic processes.

Abstract: Cyclosporine forms the cornerstone of therapy to prevent rejection after organ transplantation. However, the clinical use of the drug is compromised by a narrow therapeutic window and a wide interand intra-individual variation in metabolism. Cyclosporine is metabolised by the CYP3A4 isoenzymes in both the liver and intestine, while it has been reported that the metabolism of the drug can be inhibited by certain furocoumarin derivatives in grapefruit juice. Methoxsalen (8-methoxypsoralen) is a furocoumarin and a potent inhibitor of the cytochrome P450 system in both the liver and intestine. The study was conducted to investigate the possibility whether methoxsalen may inhibit the metabolism of cyclosporine and thereby increase the bioavailability of the drug. The interaction is of clinical relevance since both drugs are used in the treatment of psoriases. The study, conducted in 12 healthy male volunteers, was a three-way comparative bioavailability study with a wash out period of one week between treatments. The patients received 40 mg methoxsalen, 200 mg cyclosporine or a combination of the two on three separate occasions. Blood samples of 10 ml were collected by venupuncture at the following times: 0, 0.5, 1, 1.5, 2, 2.5, 3.4, 5,6, 8, 12 and 24 hours after drug administration. Methoxsalen was analysed by a high pressure liquid chromatograph method (HPLC) with UV detection (LOQ = 10 qgtml), while cyclosporine was analysed using a fluorescence polarisation immunoassay (FPIA) technique. The results were as follows: Cyclosporine and Cyclosporinehlethoxsalen combination. L I I I I *P-value = Paired t-test. *%'-value =Clinical Significant test *** = Statistical significant. I Methoxsalen and the Methoxsalen/Cyclosporine combination. There was a statistical significant difference in AUCo, and C& ' for cyclosporine when methoxsalen was added to the drug regimen. When the methoxsalen levels were compared with those in the presence of cyclosporine, the levels were lower, although the difference was not statistical significant. We conclude that methoxsalen increase the levels of cyclosporine by inhibiting the P450 system enzymes in the liver and intestine. However, the absorption of methoxsalen is highly variable in the same individual which needs to be considered before this interaction can be regarded as being of any clinical relevance.