Safety of verteporfin for treatment of subfoveal choroidal neovascular membranes associated with age-related macular degeneration

Photodynamic therapy (PDT) is a novel treatment entity that exploits the photophysical properties of various photosensitive chemical entities which, upon light activation, results in targeted photooxidation and subsequent tissue destruction. The antiangiogenic properties of PDT have been adapted for treatment of subfoveal choroidal neovascular membranes due to disease states such as age-related macular degeneration (AMD). Historically, PDT has been limited by a lack of suitable photosensitive dyes. However, agents such as verteporfin, a second-generation benzoporphyrin derivative, appear to be free from the extensive phototoxicity that limited the success of previous agents. Verteporfin has a high affinity for choroidal neovascular membranes, typically found with exudative AMD, and upon photoactivation results in targeted microvascular damage and thrombus formation with resultant vessel occlusion. Scrutiny of diagnostic indicators for verteporfin administration, including critical angiographic evaluation of lesion size and visual acuity, is essential to treatment success. Large lesions with relatively good visual acuity (20/50 or better) may be at particular risk for marked vision loss following verteporfin administration. Lesion composition also appears to influence visual outcome with verteporfin use. The safety of verteporfin is directly dependent upon the appropriate integration of dosage, infusion and light activation required for a suitable pharmacotherapeutic outcome. When used appropriately, and with adequate patient education regarding photosensitivity, the risk–benefit of verteporfin for the medical treatment of neovascular AMD is favourable.     

Safety of verteporfin for treatment of subfoveal choroidal neovascular membranes associated with age-related macular degeneration

Photodynamic therapy (PDT) is a novel treatment entity that exploits the photophysical properties of various photosensitive chemical entities which, upon light activation, results in targeted photooxidation and subsequent tissue destruction. The antiangiogenic properties of PDT have been adapted for treatment of subfoveal choroidal neovascular membranes due to disease states such as age-related macular degeneration (AMD). Historically, PDT has been limited by a lack of suitable photosensitive dyes. However, agents such as verteporfin, a second-generation benzoporphyrin derivative, appear to be free from the extensive phototoxicity that limited the success of previous agents. Verteporfin has a high affinity for choroidal neovascular membranes, typically found with exudative AMD, and upon photoactivation results in targeted microvascular damage and thrombus formation with resultant vessel occlusion. Scrutiny of diagnostic indicators for verteporfin administration, including critical angiographic evaluation of lesion size and visual acuity, is essential to treatment success. Large lesions with relatively good visual acuity (20/50 or better) may be at particular risk for marked vision loss following verteporfin administration. Lesion composition also appears to influence visual outcome with verteporfin use. The safety of verteporfin is directly dependent upon the appropriate integration of dosage, infusion and light activation required for a suitable pharmacotherapeutic outcome. When used appropriately, and with adequate patient education regarding photosensitivity, the risk-benefit of verteporfin for the medical treatment of neovascular AMD is favourable.     

A preliminary benefit-risk assessment of verteporfin in age-related macular degeneration.

The prevalence of neovascular age-related macular degeneration (AMD) is expected to increase significantly during the next 20 years. New treatment alternatives to laser photocoagulation are on the horizon - the first of these, photodynamic therapy (PDT) with verteporfin, was approved by the US FDA in 2000. In this article we present a preliminary risk-benefit assessment of verteporfin in AMD, focusing on the landmark randomised, double-blind, placebo-controlled studies. The TAP (Treatment of Age-related macular degeneration with Photodynamic therapy) trial established the efficacy of PDT for classic subfoveal neovascularisation in AMD at 2 years follow-up. The VIP (Verteporfin in Photodynamic therapy) study concentrated on subfoveal occult-only lesions not included in the TAP study. After 2 years, treated eyes were less likely to experience visual loss. Exploratory analyses of TAP and VIP suggest that lesion size is a more significant predictor of the treatment benefit than either lesion composition or visual activity. The VIM (Visudyne in Minimally classic) trial altered the standard PDT light fluence rate in the treatment of subfoveal minimally classic lesions. This trial again demonstrated a beneficial effect for those receiving treatment with PDT. The VIO (Visudyne in Occult) trial, evaluating PDT in occult-only lesions as a confirmatory study of the VIP trial, did not achieve its primary end-point at 2 years. Further analyses are pending.PDT with verteporfin has an excellent safety profile that has been established with >1 million treatment applications. Cost-effectiveness data are limited but suggest that PDT may be a cost-effective treatment modality. Other FDA-approved treatments (pegaptanib, ranibizumab and bevacizumab) for neovascular AMD are discussed, as well as investigational substances such as anecortave acetate.     

Evaluation of verteporfin pharmakokinetics--redefining the need of photosensitizers in ophthalmology

INTRODUCTION: The benzoporphyrine derivative verteporfin has lost its importance to the treatment of the most frequent neovascular eye diseases. Nevertheless, it is still mandatory to define the remaining applications, role, and potential of verteporfin in ocular photodynamic therapy (PDT), including the dosages of administration, effectiveness, and safety profile. AREAS COVERED: Although verteporfin PDT has forfeited the first-line status and value of treating subfoveal choroidal neovascularization (CNV) due to age-related macular degeneration or pathologic myopia, the treatment remains the standard of care for choroidal haemangioma and polypoidal choroidal vasculopathy. PDT is effective in less pigmented choroidal melanoma as well as in retinal vascular proliferations and retinal angioma. Verteporfin was granted the orphan drug designation for the treatment of chronic or recurrent central serous chorioretinopathy (CSC). EXPERT OPINION: Evidence-based data regarding optimized parameters (low fluence, reduced dose, fractionated irradiation) adapted to the treated diseases (target structure, dosimetry, blood supply) are scarce. Prospective and large clinical trials are missing, although the scientific community agrees on the fact that the standard treatment protocol does not necessarily provide the optimal efficacy to the specific disease or individual patient. Within the reviewed indications, the adverse effect profile is favorable compared with other therapies.     

An update on photodynamic therapy in age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible loss of central vision in people aged > 50 years in the western world. Until recently, the only proven treatment to reduce the risk of vision loss from its more severe neovascular form was laser photocoagulation, but this treatment was suitable for only 15% of cases. Photodynamic therapy (PDT) with verteporfin was recently proposed to be effective in reducing the risk of visual loss for an estimated 20 - 30% of neovascular AMD patients. This review covers AMD epidemiology, the mechanism of PDT, the 2-year results of the two major clinical studies of PDT with verteporfin, the cost-effectiveness of PDT and the current research status of other drugs for PDT in AMD.     

An update on photodynamic therapy in age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible loss of central vision in people aged > 50 years in the western world. Until recently, the only proven treatment to reduce the risk of vision loss from its more severe neovascular form was laser photocoagulation, but this treatment was suitable for only 15% of cases. Photodynamic therapy (PDT) with verteporfin was recently proposed to be effective in reducing the risk of visual loss for an estimated 20 – 30% of neovascular AMD patients. This review covers AMD epidemiology, the mechanism of PDT, the 2-year results of the two major clinical studies of PDT with verteporfin, the cost-effectiveness of PDT and the current research status of other drugs for PDT in AMD.     

Photosensitiser delivery for photodynamic therapy. Part 2: systemic carrier platforms

Background: The treatment of solid tumours and angiogenic ocular diseases by photodynamic therapy (PDT) requires the injection of a photosensitiser (PS) to destroy target cells through a combination of visible light irradiation and molecular oxygen. There is currently great interest in the development of efficient and specific carrier delivery platforms for systemic PDT. Objective: This article aims to review recent developments in systemic carrier delivery platforms for PDT, with an emphasis on target specificity. Methods: Recent publications, spanning the last five years, concerning delivery carrier platforms for systemic PDT were reviewed, including PS conjugates, dendrimers, micelles, liposomes and nanoparticles. Results/conclusion: PS conjugates and supramolecular delivery platforms can improve PDT selectivity by exploiting cellular and physiological specificities of the targeted tissue. Overexpression of receptors in cancer and angiogenic endothelial cells allows their targeting by affinity-based moieties for the selective uptake of PS conjugates and encapsulating delivery carriers, while the abnormal tumour neovascularisation induces a specific accumulation of heavy weighted PS carriers by enhanced permeability and retention (EPR) effect. In addition, polymeric prodrug delivery platforms triggered by the acidic nature of the tumour environment or the expression of proteases can be designed. Promising results obtained with recent systemic carrier platforms will, in due course, be translated into the clinic for highly efficient and selective PDT protocols.     

Verteporfin

Verteporfin, a benzoporphyrin derivative monoacid ring A, is a photosensitising drug for photodynamic therapy (PDT) activated by low-intensity, nonheat-generating light of 689nm wavelength. Activation generates cytotoxic oxygen free radicals. The specificity and uptake of verteporfin for target cells with a high expression of low density lipoprotein (LDL) receptors, such as tumour and neovascular endothelial cells, is enhanced by the use of a liposomal formulation and its rapid uptake by plasma LDL. Verteporfin therapy (at light doses < 150 J/cm) selectively damages neovascular endothelial cells leading to thrombus formation and specific occlusion of choroidal neovascular vessels in subfoveal lesions in patients with age-related macular degeneration (AMD). Repeated applications of verteporfin therapy 6 mg/m2 improved or maintained visual acuity in the majority of patients with some classic subfoveal choroidal neovascularisation (CNV) secondary to AMD at 1 year's follow-up in 2 large multicentre, placebo-controlled, double-blind trials. Furthermore. in a subgroup of these patients with predominantly classic CNV secondary to AMD, there was a significantly more marked visual acuity (VA) benefit with 67.3% of verteporfin-treated eyes experiencing less than a 15-letter loss of VA versus 39.3% with placebo treatment. Multiple applications of verteporfin therapy were well tolerated in patients with subfoveal CNV secondary to AMD. The most common adverse events were visual disturbances, injection site reactions, photosensitivity reactions and infusion-related back pain.     

Hypocrellin B-encapsulated nanoparticle-mediated rev-caspase-3 gene transfection and photodynamic therapy on tumor cells

Gene therapy and photodynamic therapy are two kinds of important therapeutic strategies for treating malignant tumors. In order to explore the combined effects of gene therapy and PDT on tumor cells, rev-caspase-3 gene was transfected into the tumor model CNE2 cells using hypocrellin B-encapsulated nanoparticle (nano-HB) as a carrier. The transfected CNE2 cells were then irradiated by light from a LED source and the survival rate was investigated 18 h after PDT. Apoptosis was analyzed by a flow cytometer with propidium iodine (PI) staining and the active caspase-3 expression was measured using flow cytometry with phycoerythrin (PE)-conjugated anti-active caspase-3 antibody. The result from the flow cytometer showed that the level of the activated caspase-3 significantly increased up to 63.10% in the transfected CNE2 cells. The survival rate 18 h after gene transfection alone and nano-HB-mediated PDT was 96.6±2.07%, 72.6±4.15%, respectively. However, the survival rate of the transfected CNE2 cells 18 h after LED exposure significantly decreased to 50.6±5.98% under the light energy of 4 J/cm(2). Apoptotic rate 18 h after the combination of gene transfection and PDT increased up to 24.65%. Our findings demonstrated that nano-HB could significantly enhance the transfection efficiency of rev-caspase-3 gene in the CNE2 cells. LED irradiation could effectively kill the treated CNE2 cells and induce apoptosis, suggesting hypocrellin B-encapsulated nanoparticle as an efficient gene carrier and a novel photosensitizer. The combination of gene therapy and PDT using nanoparticle as a mediator can be developed for treating nasopharyngeal carcinoma.     

Photodynamic therapy combined with intravitreal injection of triamcinolone acetonide for choroidal neovascularization

The aim of this research was to evaluate the efficacy and safety of photodynamic therapy (PDT) combined with intravitreal injection of triamcinolone acetonide (TA) in the treatment of choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD) and pathological myopia. PDT combined with intravitreal injection of TA was performed on 16 eyes of 16 patients with CNV diagnosed by visual acuity, fluorescein fundus angiography (FFA) and optical coherent tomography (OCT), including 14 eyes secondary to age-related macular degeneration and two eyes secondary to pathological myopia. TA was injected intravitreally 72 h post PDT on 12 eyes and from three months to one year (mean nine months) post PDT on four eyes respectively. All the patients were followed up for 3 to 18 months (mean 18.6 months). Best-corrected visual acuity, intraocular pressure, retinal thickness and FFA were observed. The visual acuity was improved in seven eyes (43.8%) of all the 16 eyes and stable in nine eyes (56.2%), respectively. FFA revealed complete or partial closure of CNV in all patients. OCT showed that the macular edema disappeared or was alleviated. Transient intraocular pressure elevation occurred in one patient (6.25%) of all the 16 eyes and intraocular pressure returned to the normal after a transient treatment with antiglaucoma medication. The mean number of PDTs during the first year was 1.1. PDT combined with intravitreal injection of TA for CNV is safe and effective. It can reduce the risk of visual loss and the treatment frequency. __________ Translated from Chinese Journal of Ocular Fundus Diseases, 2007, 23(1): 13–16 [译自: 中华眼底病杂志]     

Surfactant-polymer nanoparticles enhance the effectiveness of anticancer photodynamic therapy

Photodynamic therapy (PDT) is a promising treatment modality for cancer. PDT is based on the concept that photosensitizers, when exposed to light of specific wavelength, generate cytotoxic reactive oxygen species (ROS) capable of killing tumor cells. The effectiveness of PDT has been limited in part by the lack of photosensitizers that accumulate sufficiently in tumor cells and poor yield of ROS from existing photosensitizers. In this report, we investigated whether aerosol OT-alginate nanoparticles can be used as a carrier to enhance the therapeutic efficacy of a model photosensitizer, methylene blue. Methylene blue loaded nanoparticles were evaluated for PDT effectiveness in two cancer cell lines, MCF-7 and 4T1. Encapsulation of methylene blue in nanoparticles significantly enhanced intracellular ROS production, and the overall cytotoxicity following PDT. It also resulted in higher incidence of necrosis. Greater effectiveness of nanoparticles could be correlated with higher yield of ROS with nanoparticle-encapsulated methylene blue. Further, treatment of tumor cells with nanoparticle-encapsulated methylene blue resulted in significant nuclear localization of methylene blue while free drug treatment resulted in its accumulation mainly in the endolysosomal vesicles. In conclusion, encapsulation of methylene blue in aerosol OT-alginate nanoparticles enhanced its anticancer photodynamic efficacy in vitro. Increased ROS production and favorable alteration in the subcellular distribution contribute to the enhanced PDT efficacy of nanoparticle-encapsulated photosensitizer.     

Advances in photosensitizer-related design for photodynamic therapy

Photodynamic therapy (PDT) is highly effective in treating tumors located near body surface, offering strong tumor suppression and low damage to normal tissue nearby. PDT is also effective for treating a number of other conditions. PDT not only provide a precise and selective method for the treatment of various diseases by itself, it can also be used in combination with other traditional therapies. Because PDT uses light as the unique targeting mechanism, it has simpler and more direct targeting capability than traditional therapies. The core material of a PDT system is the photosensitizer which converts light energy to therapeutic factors/substances. Different photosensitizers have their distinct characteristics, leading to different advantages and disadvantages. These could be enhanced or compensated by using proper PDT system. Therefore, the selected type of photosensitizer would heavily influence the overall design of a PDT system. In this article, we evaluated major types of inorganic and organic PDT photosensitizers, and discussed future research directions in the field.     

Cell death and growth arrest in response to photodynamic therapy with membrane-bound photosensitizers

Photodynamic therapy (PDT) is a treatment for cancer and for certain benign conditions that is based on the use of a photosensitizer and light to produce reactive oxygen species in cells. Many of the photosensitizers currently used in PDT localize in different cell compartments such as mitochondria, lysosomes, endoplasmic reticulum and generate cell death by triggering necrosis and/or apoptosis. Efficient cell death is observed when light, oxygen and the photosensitizer are not limiting ("high dose PDT"). When one of these components is limiting ("low dose PDT"), most of the cells do not immediately undergo apoptosis or necrosis but are growth arrested with several transduction pathways activated. This commentary will review the mechanism of apoptosis and growth arrest mediated by two important PDT agents, i.e. pyropheophorbide and hypericin.     

Pegaptanib sodium for the treatment of neovascular age-related macular degeneration

This article reviews pegaptanib sodium, a compound developed by Eyetech Pharmaceuticals Inc. and Pfizer Inc., for the treatment of neovascular age-related macular degeneration (AMD). Traditional treatment approaches to neovascular AMD have included destructive therapies such as thermal laser photocoagulation and photodynamic therapy; the use of pegaptanib sodium heralds a new treatment approach that is a non-destructive therapy based on the inhibition of vascular endothelial growth factor activity in the eye. This diminishes the neovascular drive in the pathologically hyperpermeable state of the diseased eye. Pegaptanib sodium is one of the first therapeutics belonging to the class of compounds known as aptamers. The chemistry, mechanism of action, pharmacokinetics and rationale for the clinical use of the drug are reviewed. The article highlights and summarises the results of the multi-centre, randomised, sham-controlled clinical trials with pegaptanib sodium to treat subfoveal choroidal neovascularisation in AMD. In addition, the safety profile is reviewed.     

Pegaptanib sodium for the treatment of neovascular age-related macular degeneration

This article reviews pegaptanib sodium, a compound developed by Eyetech Pharmaceuticals Inc. and Pfizer Inc., for the treatment of neovascular age-related macular degeneration (AMD). Traditional treatment approaches to neovascular AMD have included destructive therapies such as thermal laser photocoagulation and photodynamic therapy; the use of pegaptanib sodium heralds a new treatment approach that is a non-destructive therapy based on the inhibition of vascular endothelial growth factor activity in the eye. This diminishes the neovascular drive in the pathologically hyperpermeable state of the diseased eye. Pegaptanib sodium is one of the first therapeutics belonging to the class of compounds known as aptamers. The chemistry, mechanism of action, pharmacokinetics and rationale for the clinical use of the drug are reviewed. The article highlights and summarises the results of the multi-centre, randomised, sham-controlled clinical trials with pegaptanib sodium to treat subfoveal choroidal neovascularisation in AMD. In addition, the safety profile is reviewed.     

Preclinical and clinical profile of verteporfin, a potent photodynamic therapy drug for CNV secondary to AMD

Age-related macular degeneration (AMD) is the leading cause of blindness among people aged over 50 years in the western world. Verteporfin (Visudyne) is the first light-activated drug indicated for the treatment of patients with AMD caused by subfoveal choroidal neovascularization (CNV). This form of AMD is characterized by the development of abnormal blood vessels on the back of the retina that leak and cause scarring, resulting in central vision loss. Following intravenous administration, verteporfin selectively accumulates within proliferating tissue, including neovasculature, probably via low density lipoprotein receptors. The verteporfin is then activated by shining a specific wavelength of light with a nonthermal laser on the affected area in the eye. This process, called photodynamic therapy (PDT), generates reactive free radicals and highly reactive singlet oxygen in the target cells in the eye, causing damage and occlusion of the CNV and resulting in closure of the abnormal vessels and cessation of leakage. In experimentally induced CNV in animal models and in randomized, controlled clinical trials of patients with CNV due to AMD, verteporfin PDT has been shown to selectively occlude abnormal vessels without significantly altering overlying photoreceptors. Verteporfin therapy for CNV in Japanese patients had a similar or better angiographic and vision effect as that observed in Caucasian patients, with the same safety profile.     

Short incubation PDT versus 5-FU in treating actinic keratoses

The efficacy of photodynamic therapy (PDT) using broad area treatment with 5-aminolevulinic acid (ALA) has not been compared to topical 5-fluorouracil (5-FU) in the treatment of actinic keratoses (AK). The purpose of this study was to compare the efficacy and tolerability of PDT using short incubation time, broad area treatment with ALA plus activation with either blue light or laser light to topical 5-FU in the treatment of AK of the face and scalp. Thirty-six subjects with AK of either the face or scalp were randomized to receive either application of ALA for 1 hour followed by activation with blue light or pulsed dye laser or topical 5-FU. Efficacy was evaluated by grading AK lesions and photoaging signs. Tolerability was assessed by scoring crusting/erosions, erythema and stinging/burning. Treatment with PDT using ALA plus blue light was as effective as topical 5-FU in clearing AK. PDT using ALA plus laser light was the least effective treatment. All treatments made improvements in the signs of photoaging. Both PDT treatments were better tolerated than 5-FU. In conclusion, broad area PDT treatment with ALA plus activation with blue light appears to be as effective as 5-FU in the treatment of AK. ALA plus laser light is somewhat less effective than the above therapies. Efficacy could likely be improved with further study of laser parameters and incubation times.     

Photodynamic therapy in the treatment of cancer: current state of the art.

Photodynamic therapy (PDT) is a treatment modality using a photosensitising drug and light to kill cells. The clinical use of PDT requires the presence of a photosensitising agent, oxygen and light of a specific wavelength which matches the absorption characteristics of the photosensitiser. When the photosensitiser is activated by the appropriate wavelength of light, it interacts with molecular oxygen to form a toxic, short-lived species known as singlet oxygen, which is thought to mediate cellular death. The appeal of PDT in oncology is that the photosensitiser tends to be retained in tumour tissues for a longer period of time as compared with normal tissues resulting in a large therapeutic index. This potential for minimal normal tissue toxicity has prompted an interest in studying PDT as a cancer treatment. Furthermore, the use of PDT is not precluded by prior radiotherapy, chemotherapy or surgery. The development of PDT has been hampered by the limitations of the older photosensitisers, namely limited depth of tissue penetration, and extended skin phototoxicity which limits the number of applications during a course of treatment. However, newer photosensitisers are being developed which allow greater depth of tissue penetration and have minimal skin phototoxicity allowing for multiple fractionated treatments. With such advancements, PDT has great potential to become an integral part of cancer treatment in the future.     

Cancer anti-angiogenic therapy

Tumor angiogenesis affords new targets for cancer therapy, since inhibition of angiogenesis suppresses tumor growth by cutting out the supply of oxygen and nutrients. Anti-angiogenic therapy is thought to be free of the severe side effects that are usually seen with cytotoxic anticancer drugs. Furthermore, anti-angiogenic therapy is thought not only to eradicate primary tumor tissues, but also to suppress tumor metastases. However, it is uncertain whether this therapy causes tumor regression because it inhibits only angiogenic events. Recently, a novel anti-angiogenic therapy called anti-neovascular therapy (ANET) has become notable. This therapy inflicts indirect lethal damage on tumor cells by damaging newly formed blood vessels using anti-cancer drugs targeting the angiogenic vasculature, since cytotoxic anti-cancer drugs cause damage to proliferating neovascular endothelial cells as well as tumor cells. Moreover, neovascular endothelial cells would not be expected to acquire drug-resistance. Traditional chemotherapy, which directly targets tumor cells, has potential problems such as low specificity and severe side effects. On the contrary, in ANET, severe side effects may be suppressed, since traditional anti-cancer agents are delivered to the neovessels by DDS technology. Besides the usage of DDS technology, anti-neovascular scheduling of chemotherapy, or metronomic-dosing chemotherapy, has also been attempted in which anti-cancer drugs are administered on a schedule to damage neovessels. In this review, we describe traditional anti-angiogenic therapy and ANET. We also discuss anti-angiogenic cancer photodynamic therapy (PDT), since PDT is clinically applied to treat age-related macular degeneration (AMD), in which uncontrolled angiogenesis occurs.     

Promising new treatments for neovascular age-related macular degeneration

Angiogenesis, the growth of new blood vessels from existing blood vessels, is responsible for vision loss in a variety of ophthalmic diseases. In neovascular age-related macular degeneration (AMD), the leading cause for legal blindness in many industrialised countries, abnormal blood vessels grow in the macula and cause blindness. There are a number of factors important in the angiogenic cascade but VEGF-A has been implicated in recent years as the major factor responsible for neovascular and exudative diseases of the eye. Numerous antiangiogenic drugs are in development but anti-VEGF drugs have shown great promise in treating neovascular AMD and other ocular diseases, and many of these drugs have been adopted from oncology where antiangiogenic therapy is gaining wide acceptance. For the first time in neovascular AMD, anti-VEGF drugs have brought the hope of vision improvement to a significant proportion of patients. This review provides an overview on angiogenic mechanisms, potential antiangiogenic treatment strategies and different antiangiogenic drugs with special focus on neovascular AMD.