Photodynamic therapy: a new approach to the treatment of choroidal neovascularization secondary to age-related macular degeneration

Recent Emergence of Rhenium(I) Tricarbonyl Complexes as Photosensitisers for Cancer Therapy

Photodynamic therapy (PDT) is emerging as a significant complementary or alternative approach for cancer treatment. PDT drugs act as photosensitisers, which upon using appropriate wavelength light and in the presence of molecular oxygen, can lead to cell death. Herein, we reviewed the general characteristics of the different generation of photosensitisers. We also outlined the emergence of rhenium (Re) and more specifically, Re(I) tricarbonyl complexes as a new generation of metal-based photosensitisers for photodynamic therapy that are of great interest in multidisciplinary research. The photophysical properties and structures of Re(I) complexes discussed in this review are summarised to determine basic features and similarities among the structures that are important for their phototoxic activity and future investigations. We further examined the in vitro and in vivo efficacies of the Re(I) complexes that have been synthesised for anticancer purposes. We also discussed Re(I) complexes in conjunction with the advancement of two-photon PDT, drug combination study, nanomedicine, and photothermal therapy to overcome the limitation of such complexes, which generally absorb short wavelengths.

DLC1 deficiency and YAP signaling drive endothelial cell contact inhibition of growth and tumorigenesis

Deleted in Liver Cancer 1 (DLC1) is a tumor suppressor gene deleted in many cancers, including angiosarcoma, an aggressive malignancy of endothelial cell derivation. DLC1-deficiency in primary endothelial cells causes the loss of cell contact inhibition of growth through incompletely defined mechanisms. We report that DLC1 is a regulator of YAP, a transcriptional coactivator of proliferation-promoting and tumor-promoting genes; when confluent, active/nuclear YAP was significantly more abundant in DLC1-deficient endothelial cells compared with control cells. We also found that YAP is a required effector of the loss of cell contact inhibition of growth manifested by DLC1-deficient endothelial cells, as the silencing of YAP prevents this loss. Consistently, human angiosarcomas specimens contained a significantly greater proportion of DLC1^- tumor cells with nuclear YAP compared with the DLC1⁺ normal cells in the adjacent tissue. Verteporfin, an inhibitor of YAP, significantly reduced angiosarcoma growth in mice. These results identify YAP as a previously unrecognized effector of DLC1 deficiency-associated loss of cell contact growth inhibition in endothelial cells and a potential therapeutic target in angiosarcoma.

Use of Photosensitizers in Semisolid Formulations for Microbial Photodynamic Inactivation

Semisolid formulations, such as gels, creams and ointments, have recently contributed to the progression of photodynamic therapy (PDT) and microbial photodynamic inactivation (PDI) in clinical applications. The most important challenges facing this field are the physicochemical properties of photosensitizers (PSs), optimal drug release profiles, and the photosensitivity of surrounding tissues. By further integration of nanotechnology with semisolid formulations, very promising pharmaceuticals have been generated against several dermatological diseases (PDT) and (antibiotic-resistant) pathogenic microorganisms (PDI). This review focuses on the different PSs and their associated semisolid formulations currently found in both the market and clinical trials that are used in PDT/PDI. Special emphasis is placed on the advantages that the semisolid formulations bring to drug delivery in PDI. Lastly, some potential considerations for improvement in this field are also discussed.

Nanomicellar Topical Aqueous Drop Formulation of Rapamycin for Back-of-the-Eye Delivery

The objective of this study was to develop a clear, aqueous rapamycin-loaded mixed nanomicellar formulations (MNFs) for the back-of-the-eye delivery. MNF of rapamycin (0.2%) was prepared with vitamin E tocopherol polyethylene glycol succinate (TPGS) (Vit E TPGS) and octoxynol-40 (Oc-40) as polymeric matrix. MNF was characterized by various parameters such as size, charge, shape, and viscosity. Proton nuclear magnetic resonance ((1)H NMR) was used to identify unentrapped rapamycin in MNF. Cytotoxicity was evaluated in human retinal pigment epithelial (D407) and rabbit primary corneal epithelial cells (rPCECs). In vivo posterior ocular rapamycin distribution studies were conducted in male New Zealand white rabbits. The optimized MNF has excellent rapamycin entrapment and loading efficiency. The average size of MNF was 10.98 ± 0.089 and 10.84 ± 0.11 nm for blank and rapamycin-loaded MNF, respectively. TEM analysis revealed that nanomicelles are spherical in shape. Absence of free rapamycin in the MNF was confirmed by (1)H NMR studies. Neither placebo nor rapamycin-loaded MNF produced cytotoxicity on D407 and rPCECs indicating formulations are tolerable. In vivo studies demonstrated a very high rapamycin concentration in retina-choroid (362.35 ± 56.17 ng/g tissue). No drug was identified in the vitreous humor indicating the sequestration of rapamycin in lipoidal retinal tissues. In summary, a clear, aqueous MNF comprising of Vit E TPGS and Oc-40 loaded with rapamycin was successfully developed. Back-of-the-eye tissue distribution studies demonstrated a very high rapamycin levels in retina-choroid (place of drug action) with a negligible drug partitioning into vitreous humor.

Phase I/II study of verteporfin photodynamic therapy in locally advanced pancreatic cancer

Background:

Patients with pancreatic cancer have a poor prognosis apart from the few suitable for surgery. Photodynamic therapy (PDT) produces localised tissue necrosis but previous studies using the photosensitiser meso-tetrahydroxyphenylchlorin (mTHPC) caused prolonged skin photosensitivity. This study assessed a shorter acting photosensitiser, verteporfin.

Methods:

Fifteen inoperable patients with locally advanced cancers were sensitised with 0.4 mg kg⁻¹ verteporfin. After 60–90 min, laser light (690 nm) was delivered via single (13 patients) or multiple (2 patients) fibres positioned percutaneously under computed tomography (CT) guidance, the light dose escalating (initially 5 J, doubling after each three patients) until 12 mm of necrosis was achieved consistently.

Results:

In all, 12 mm lesions were seen consistently at 40 J, but with considerable variation in necrosis volume (mean volume 3.5 cm³ at 40 J). Minor, self-limiting extrapancreatic effects were seen in multifibre patients. No adverse interactions were seen in patients given chemotherapy or radiotherapy before or after PDT. After PDT, one patient underwent an R0 Whipple's pancreaticoduodenectomy.

Conclusions:

Verteporfin PDT-induced tumour necrosis in locally advanced pancreatic cancer is feasible and safe. It can be delivered with a much shorter drug light interval and with less photosensitivity than with older compounds.

Photodynamic therapy using verteporfin photosensitization in the pancreas and surrounding tissues in the Syrian golden hamster

BACKGROUND/AIM

Photodynamic therapy (PDT) is a potential treatment for locally advanced pancreatic cancer. We aimed to assess the safety of interstitial PDT using verteporfin (benzoporphyrin derivative monoacid A - a novel photosensitizer with a short drug-light interval and limited cutaneous photosensitivity) in the Syrian golden hamster, and compare it to meso-tetrahydroxyphenylchlorin (mTHPC) which we have previously evaluated in preclinical and clinical studies.

METHODS

Verteporfin (2 mg/kg) was administered at laparotomy by inferior vena caval injection (n = 57), with plasma levels quantified at 5, 15, 30, 60 and 240 min, and 24 h. 15 min after photosensitization, tissues (liver, pancreas, duodenum, colon, aorta) were illuminated with 690 nm red laser light (150 mW), at a range of light doses (1-100 J/cm(2)). The PDT effects on the targeted organ and adjacent structures were assessed at post-mortem on days 3 and 21, or at the time of death.

RESULTS

The elimination half-life of verteporfin was 4-5 h. Light doses of 10, 25 and 50 J/cm(2) were safe in the hamster pancreas, liver and colon, respectively, and produced coagulative necrotic lesions of 3 (range 3-4), 10 (9-10) and 7 (7-8) mm diameter. Collagen was resistant to damage and lesions healed mainly by regeneration of normal tissue. At higher light doses, necrosis extended to the edge of organs, sometimes causing sealed duodenal perforations as seen with mTHPC.

CONCLUSION

The safety profile of verteporfin is very similar to mTHPC, with the advantages of a shorter drug-light interval and drug elimination time. Phase I clinical studies using this photosensitizer in pancreatic cancer should be feasible.

Review of first year result of photodynamic therapy on age-related macular degeneration in chinese population

PURPOSE

To evaluate the effect of verteporfin therapy (Visudyne) on age-related macular degeneration (AMD) in Chinese patients. The baseline characteristic and the visual outcome will be compared with the treatment of AMD with photodynamic therapy study (TAP) and verteporfin in photodynamic therapy study (VIP).

DESIGN

Retrospective comparative case series.

METHOD

We recruited patients >50 years old, with best-corrected visual acuity >20/200 and fluorescein angiography documenting subfoveal either predominantly classic with greatest linear dimension <5400 mum or pure occult choroidal neovascularization (CNV) secondary to AMD. We applied non-thermal laser to the lesion 15 min after visudyne infusion as described in TAP study. Patients were followed up with fluorescein angiography every 3 months. Additional treatment would be offered if there was evidence of recurrence of CNV.

OUTCOME MEASURE

Baseline characteristic and visual outcome.

RESULT

In all, 46 eyes of 42 patients were enrolled at our centre from July 2002 to June 2003. They comprised 11 eyes with predominantly classic lesions and 35 eyes with pure occult lesion. The mean number of treatment sessions given was 2.9 in the first year. At the 12-month examination, there were 63 and 29% of patients showing visual improvement in predominantly classic and occult groups, respectively, while there were only 16% of patients in the TAP study and 12% of patients in the VIP study showing visual improvement in the same period.

CONCLUSION

Verteporfin therapy for subfoveal CNV is beneficial to Chinese patients with AMD at first year. The visual result seems to be better than that observed in Caucasian patients.

Update on photodynamic therapy

To date, photodynamic therapy with verteporfin has been shown to benefit those patients with age-related molecular degeneration and choroidal neovascularization that is subfoveal and predominately classic (> 50%). As of this writing, the Food and Drug Administration is requiring additional data before verteporfin is approved for treatment of occult subfoveal choroidal neovascularization. Photodynamic therapy has also proved beneficial for subfoveal lesions secondary to high myopia. Although there is potential for patients with angioid streaks, ocular histoplasmosis syndrome, and idiopathic causes of choroidal neovascularization to benefit from photodynamic therapy, randomized clinical trials have not been performed. Photodynamic therapy has not been shown to benefit patients with minimally classic (< 50%) lesions.

Photodynamic therapy using Verteporfin (benzoporphyrin derivative monoacid ring A, BPD-MA) and 630 nm laser light in canine esophagus

BACKGROUND AND OBJECTIVE

Verteporfin is a new photosensitizer with short-term skin photosensitivity. The objective of this preclinical study was to find the light dose that effectively ablates canine esophageal mucosa when delivered 30 minutes after Verteporfin injection.

STUDY DESIGN/MATERIALS AND METHODS

Verteporfin was administered intravenously (0.75 mg/kg). 630 nm light from KTP/Dye laser was delivered using an esophageal Photodynamic therapy (PDT) balloon. In Phase I study, animals were treated 30 minutes after drug injection using 40, 60, and 80 J/cm to find the desired light dose. Using results from phase I and application of reciprocity principle (light dose vs. plasma concentration of drug), additional light doses were calculated for delivery at other times. In phase II, animals were treated at 15, 60, and 120 minutes, using the calculated light doses of 60, 145, and 200 J/cm, respectively. Animals were followed for 2 days to 4 weeks.

RESULTS

In Phase I, 80 J/cm at 30 minutes induced total mucosal ablation. In Phase II, light doses of 60, 145, and 200 J/cm induced similar mucosal injuries when delivered at 15, 60, and 120 minutes, respectively.

CONCLUSIONS

Effective mucosal ablation in canine esophagus was achieved using Verteporfin and 630 nm light doses of 60, 80, 145, and 200 J/cm when delivered at 15, 30, 60, and 120 minutes after the drug injection, respectively.

Photodynamic therapy with verteporfin in mallatia leventinese

OBJECTIVE

To describe a case of a patient with documented genetic mallatia leventinese who developed a classic choroidal neovascular membrane and underwent photodynamic therapy (PDT) with verteporfin (Visudyne; CIBA Vision Corp., Duluth, GA).

DESIGN

Interventional case report.

INTERVENTION

The patient underwent a complete ophthalmologic evaluation and fluorescein angiography. Photodynamic therapy with verteporfin was performed.

MAIN OUTCOME MEASURES

Clinical and angiographic records were analyzed for evidence of changes in visual acuity, clinically evident subretinal fluid and the extent of fluorescein leakage from choroidal neovascularization (CNV).

RESULTS

Three weeks after treatment, a fluorescein angiogram showed closure of the neovascular membrane, no evident subretinal fluid was seen, and visual acuity had improved from 20/60- to 20/40. Nine weeks after the application, fluorescein angiography demonstrated a microscopic hyperfluorescent spot at the site of the previously active CNV at which a small area of shallow subretinal fluid was observed, and visual acuity was 20/50. Thirty-four weeks after PDT, visual acuity was 20/60, subretinal fluid resolved, and fluorescein angiography did not show any further changes.

CONCLUSIONS

Photodynamic therapy with verteporfin may be considered as a possible treatment in patients with mallatia leventinese who develop classic CNV.

Photodynamic therapy update

Photodynamic therapy uses a photoactivating agent to selectively treat choroidal neovascularization. In April 2000, the United States Food and Drug Administration approved verteporfin photodynamic therapy for the treatment of subfoveal, predominately classic, choroidal neovascularization caused by age-related macular degeneration. The treatment of choroidal neovascularization from other causes such as myopia, angioid streaks, and idiopathy, and presumed ocular histoplasmosis syndrome is still under investigation. Other photoactivating agents are being evaluated. Photodynamic therapy has been shown to halt the progression of visual loss in patients with age-related macular degeneration who have subfoveal predominately classic choroidal neovascularization. The socio-economic impact of verteporfin approval has yet to be determined.

Antivascular treatment of solid melanoma tumors with bacteriochlorophyll-serine-based photodynamic therapy

We describe here a strategy for photodynamic eradication of solid melanoma tumors that is based on photo-induced vascular destruction. The suggested protocol relies on synchronizing illumination with maximal circulating drug concentration in the tumor vasculature attained within the first minute after administrating the sensitizer. This differs from conventional photodynamic therapy (PDT) of tumors where illumination coincides with a maximal concentration differential of sensitizer in favor of the tumor, relative to the normal surrounding tissue. This time window is often achieved after a delay (3-48 h) following sensitizer administration. We used a novel photosensitizer, bacteriochlorophyll-serine (Bchl-Ser), which is water soluble, highly toxic upon illumination in the near-infrared (lambda max 765-780 nm) and clears from the circulation in less than 24 h. Nude CD1 mice bearing malignant M2R melanotic melanoma xenografts (76-212 mm3) received a single complete treatment session. Massive vascular damage was already apparent 1 h after treatment. Changes in vascular permeability were observed in vivo using contrast-enhanced magnetic resonance imaging (MRI), with the contrast reagent Gd-DTPA, by shortening spin-spin relaxation time because of hemorrhage formation and by determination of vascular macromolecular leakage. Twenty-four hours after treatment a complete arrest of vascular perfusion was observed by Gd-DTPA-enhanced MRI. Histopathology performed at the same time confirmed primary vascular damage with occlusive thrombi, hemorrhage and tumor necrosis. The success rate of cure of over 80% with Bchl-Ser indicates the benefits of the short and effective treatment protocol. Combining the sensitizer administration and illumination steps into one treatment session (30 min) suggests a clear advantage for future PDT of solid tumors.