Verteporfin PDT for non-standard indications--a review of current literature

Advances in Medicine: Photodynamic Therapy

Over the past decades, medicine has made enormous progress, revolutionized by modern technologies and innovative therapeutic approaches. One of the most exciting branches of these developments is photodynamic therapy (PDT). Using a combination of light of a specific wavelength and specially designed photosensitizing substances, PDT offers new perspectives in the fight against cancer, bacterial infections, and other diseases that are resistant to traditional treatment methods. In today's world, where there is a growing problem of drug resistance, the search for alternative therapies is becoming more and more urgent. Imagine that we could destroy cancer cells or bacteria using light, without the need to use strong chemicals or antibiotics. This is what PDT promises. By activating photosensitizers using appropriately adjusted light, this therapy can induce the death of cancer or bacterial cells while minimizing damage to surrounding healthy tissues. In this work, we will explore this fascinating method, discovering its mechanisms of action, clinical applications, and development prospects. We will also analyze the latest research and patient testimonies to understand the potential of PDT for the future of medicine.

Pseudoxanthoma elasticum - Genetics, pathophysiology, and clinical presentation

Pseudoxanthoma elasticum (PXE) is an autosomal-recessively inherited multisystem disease. Mutations in the ABCC6-gene are causative, coding for a transmembrane transporter mainly expressed in hepatocytes, which promotes the efflux of adenosine triphosphate (ATP). This results in low levels of plasma inorganic pyrophosphate (PPi), a critical anti-mineralization factor. The clinical phenotype of PXE is characterized by the effects of elastic fiber calcification in the skin, the cardiovascular system, and the eyes. In the eyes, calcification of Bruch's membrane results in clinically visible lesions, including peau d'orange, angioid streaks, and comet tail lesions. Frequently, patients must be treated for secondary macular neovascularization. No effective therapy is available for treating the cause of PXE, but several promising approaches are emerging. Finding appropriate outcome measures remains a significant challenge for clinical trials in this slowly progressive disease. This review article provides an in-depth summary of the current understanding of PXE and its multi-systemic manifestations. The article offers a detailed overview of the ocular manifestations, including their morphological and functional consequences, as well as potential complications. Lastly, previous and future clinical trials of causative treatments for PXE are discussed.

Targeting EphA2: a promising strategy to overcome chemoresistance and drug resistance in cancer

Erythropoietin-producing hepatocellular A2 (EphA2) is a vital member of the Eph tyrosine kinase receptor family and has been associated with developmental processes. However, it is often overexpressed in tumors and correlates with cancer progression and worse prognosis due to the activation of its noncanonical signaling pathway. Throughout cancer treatment, the emergence of drug-resistant tumor cells is relatively common. Since the early 2000s, researchers have focused on understanding the role of EphA2 in promoting drug resistance in different types of cancer, as well as finding efficient and secure EphA2 inhibitors. In this review, the current knowledge regarding induced resistance by EphA2 in cancer treatment is summarized, and the types of cancer that lead to the most cancer-related deaths are highlighted. Some EphA2 inhibitors were also investigated. Regardless of whether the cancer treatment has reached a drug-resistance stage in EphA2-overexpressing tumors, once EphA2 is involved in cancer progression and aggressiveness, targeting EphA2 is a promising therapeutic strategy, especially in combination with other target-drugs for synergistic effect. For that reason, monoclonal antibodies against EphA2 and inhibitors of this receptor should be investigated for efficacy and drug toxicity.

Increased risk of glaucoma development in patients with central serous chorioretinopathy: results of a 11-year population-based cohort study

PURPOSE

To investigate whether patients with central serous chorioretinopathy (CSC) have increased risk of developing glaucoma.

METHODS

Patients diagnosed with CSC between 1 January 2008 and 31 December 2018 were included in this study using data from the Taiwanese National Health Insurance Research Database (NHIRD). The CSC cohort was matched with a non-CSC cohort using the propensity score matching method, based on sex, age (in 10-year intervals), index date year, comorbidities, and steroid use, resulting in equal numbers of patients in both cohorts. Patients were followed up until 31 December 2019 or until they were withdrawn from the NHIRD. The incidence of glaucoma was compared between the two cohorts using the Cox regression model, and the risk of developing glaucoma was estimated using the Kaplan-Meier method.

RESULTS

After adjusting for sex, age, comorbidities, and steroid use, the CSC cohort showed a significantly higher risk of developing glaucoma compared to those without CSC (adjusted HR = 3.99; 95% CI = 3.44-4.62). The cumulative incidence of glaucoma in the CSC cohort was also significantly higher than in the non-CSC cohort (log-rank test, p < 0.001). Among the glaucoma subtypes, normal tension glaucoma had the highest risk (adjusted HR = 5.79; 95% CI = 3.41-9.85), followed by primary open-angle glaucoma (adjusted HR = 2.77; 95% CI = 2.12-3.62).

CONCLUSIONS

In conclusion, our study shows that CSC patients are at a higher risk of developing glaucoma, especially NTG. Awareness and regular glaucoma screenings are essential for patients with CSC.

Choroidal arteriovenous anastomoses: a hypothesis for the pathogenesis of central serous chorioretinopathy and other pachychoroid disease spectrum abnormalities

The pachychoroid disease spectrum (PDS) includes several chorioretinal diseases that share specific choroidal abnormalities. Although their pathophysiological basis is poorly understood, diseases that are part of the PDS have been hypothesized to be the result of venous congestion. Within the PDS, central serous chorioretinopathy is the most common condition associated with vision loss, due to an accumulation of subretinal fluid in the macula. Central serous chorioretinopathy is characterized by distinct risk factors, most notably a high prevalence in males and exposure to corticosteroids. Interestingly, sex differences and corticosteroids are also strongly associated with specific types of arteriovenous anastomoses in the human body, including dural arteriovenous fistula and surgically created arteriovenous shunts. In this manuscript, we assess the potential of such arteriovenous anastomoses in the choroid as a causal mechanism of the PDS. We propose how this may provide a novel unifying concept on the pathophysiological basis of the PDS, and present cases in which this mechanism may play a role.

Association of central serous chorioretinopathy with single nucleotide polymorphisms in complement factor H gene in Iranian population

OBJECTIVES

To investigate the association of two different single nucleotide polymorphisms (SNPs) in the complement factor H (CFH) gene with central serous chorioretinopathy (CSCR) in the Iranian population.

METHODS

This is a case-control study with 95 participants in each group who were stratified according to their various ethnical variations. Primers for rs1329428 and rs3753394 polymorphisms were synthesized. DNA was extracted from peripheral blood leukocytes and underwent PCR and high-resolution melt analysis.

RESULTS

The frequency of tt, ct, and cc genotypes for rs1329428 polymorphism was 22 (26.5%), 46 (55.4%), and 15 (18.1%) in acute CSCR and 5 (41.7%), 5 (41.7%), and 2 (16.7%) in chronic CSCR respectively with no significant difference between case and control groups. The frequency of tt, ct, and cc genotypes for rs3753394 polymorphism was 31 (37.3%), 14 (16.9%), and 38 (45.8%) in acute CSCR and 4 (33.3%), 3 (25%), and 5 (41.7%) in chronic CSCR respectively. There was a significant difference between patients of Persian descent and controls in rs3753394 polymorphism (P = 0.00, chi-square test). There was no statistical difference in the frequency of polymorphism between acute and chronic patients (P = 0.64 and P = 0.79 respectively, chi-square test).

CONCLUSIONS

The rs3753394 polymorphism is probably associated with CSCR in Persian ethnicity. Further studies are required to validate the implications of this finding in clinical practice.

Therapy of Pseudoxanthoma Elasticum: Current Knowledge and Future Perspectives

Pseudoxanthoma elasticum (PXE) is a rare, genetic, metabolic disease with an estimated prevalence of between 1 per 25,000 and 56,000. Its main hallmarks are characteristic skin lesions, development of choroidal neovascularization, and early-onset arterial calcification accompanied by a severe reduction in quality-of-life. Underlying the pathology are recessively transmitted pathogenic variants of the ABCC6 gene, which results in a deficiency of ABCC6 protein. This results in reduced levels of peripheral pyrophosphate, a strong inhibitor of peripheral calcification, but also dysregulation of blood lipids. Although various treatment options have emerged during the last 20 years, many are either already outdated or not yet ready to be applied generally. Clinical physicians often are left stranded while patients suffer from the consequences of outdated therapies, or feel unrecognized by their attending doctors who may feel uncertain about using new therapeutic approaches or not even know about them. In this review, we summarize the broad spectrum of treatment options for PXE, focusing on currently available clinical options, the latest research and development, and future perspectives.

Choroidal Volume Evaluation after Photodynamic Therapy Using New Optical Coherence Tomography Imaging Algorithm

To evaluate choroidal volume and thickness changes after photodynamic therapy (PDT) for chronic central serous chorioretinopathy (CSC). Chronic CSC eyes with a history of PDT were selected. Average choroidal volume, average choroidal thickness, the maximum and minimum choroidal thickness of the macula irradiated area and peripheral non-irradiated areas before and after one and three months of treatment were examined. A total of 14 patients with chronic CSC and 9 controls without any eye pathology were enrolled. The mean choroidal volume in CSC before and, and after one and three months of treatment were 2.36 (standard deviation: 0.70), 1.90 (0.69), 1.86 (0.66) mm³ for the central area, 1.25 (0.38), 1.14 (0.35), 1.13 (0.34) mm³ for superior nasal area, 1.47 (0.41), 1.28 (0.43), 1.26 (0.43) mm³ for superior temporal area, 1.07 (0.49), 0.95 (0.38), 0.93 (0.35) mm³ for inferior nasal area, 1.17 (0.38), 1.04 (0.32), 1.03 (0.33) mm³ for inferior temporal area. This study revealed the choroidal volume changes in a short period after PDT and a decrease in unirradiated choroidal volume was also shown after the treatment. The algorithm provided on the ARI Network enables to evaluate the choroidal changes quantitatively and qualitatively.

Exploring the choroidal vascular labyrinth and its molecular and structural roles in health and disease

The choroid is a key player in maintaining ocular homeostasis and plays a role in a variety of chorioretinal diseases, many of which are poorly understood. Recent advances in the field of single-cell RNA sequencing have yielded valuable insights into the properties of choroidal endothelial cells (CECs). Here, we review the role of the choroid in various physiological and pathophysiological mechanisms, focusing on the role of CECs. We also discuss new insights regarding the phenotypic properties of CECs, CEC subpopulations, and the value of measuring transcriptomics in primary CEC cultures derived from post-mortem eyes. In addition, we discuss key phenotypic, structural, and functional differences that distinguish CECs from other endothelial cells such as retinal vascular endothelial cells. Understanding the specific clinical and molecular properties of the choroid will shed new light on the pathogenesis of the broad clinical range of chorioretinal diseases such as age-related macular degeneration, central serous chorioretinopathy and other diseases within the pachychoroid spectrum, uveitis, and diabetic choroidopathy. Although our knowledge is still relatively limited with respect to the clinical features and molecular pathways that underlie these chorioretinal diseases, we summarise new approaches and discuss future directions for gaining new insights into these sight-threatening diseases and highlight new therapeutic strategies such as pluripotent stem cell‒based technologies and gene therapy.

Derivatives of Natural Chlorophylls as Agents for Antimicrobial Photodynamic Therapy

The rapid growth of drug-resistant bacteria all over the world has given rise to a major research challenge, namely a search for alternative treatments to which bacteria will be unable to develop resistance. Photodynamic therapy is an approach of this kind. It involves the use of photosensitizers in combination with visible light at a certain wavelength to excite the former and generate reactive oxygen species. Various synthetic heterocyclic compounds are used as photosensitizers. Of these, derivatives of natural chlorophylls have a special place due to their properties. This review deals with the use of such compounds in antimicrobial PDT.

Potential of Photodynamic Therapy Based on Sugar-Conjugated Photosensitizers

In 2015, the Japanese health insurance approved the use of a second-generation photodynamic therapy (PDT) using talaporfin sodium (TS); however, its cancer cell selectivity and antitumor effects of TS PDT are not comprehensive. The Warburg effect describes the elevated rate of glycolysis in cancer cells, despite the presence of sufficient oxygen. Because cancer cells absorb considerable amounts of glucose, they are visible using positron emission tomography (PET). We developed a third-generation PDT based on the Warburg effect by synthesizing novel photosensitizers (PSs) in the form of sugar-conjugated chlorins. Glucose-conjugated (tetrafluorophenyl) chlorin (G-chlorin) PDT revealed significantly stronger antitumor effects than TS PDT and induced immunogenic cell death (ICD). ICD induced by PDT enhances cancer immunity, and a combination therapy of PDT and immune checkpoint blockers is expected to synergize antitumor effects. Mannose-conjugated (tetrafluorophenyl) chlorin (M-chlorin) PDT, which targets cancer cells and tumor-associated macrophages (TAMs), also shows strong antitumor effects. Finally, we synthesized a glucose-conjugated chlorin e6 (SC-N003HP) that showed 10,000-50,000 times stronger antitumor effects than TS (IC₅₀) in vitro, and it was rapidly metabolized and excreted. In this review, we discuss the potential and the future of next-generation cancer cell-selective PDT and describe three types of sugar-conjugated PSs expected to be clinically developed in the future.

Conjugated Photosensitizers for Imaging and PDT in Cancer Research

Early cancer detection and perfect understanding of the disease are imperative toward efficient treatments. It is straightforward that, for choosing a specific cancer treatment methodology, diagnostic agents undertake a critical role. Imaging is an extremely intriguing tool since it assumes a follow up to treatments to survey the accomplishment of the treatment and to recognize any conceivable repeating injuries. It also permits analysis of the disease, as well as to pursue treatment and monitor the possible changes that happen on the tumor. Likewise, it allows screening the adequacy of treatment and visualizing the state of the tumor. Additionally, when the treatment is finished, observing the patient is imperative to evaluate the treatment methodology and adjust the treatment if necessary. The goal of this review is to present an overview of conjugated photosensitizers for imaging and therapy.

Regioselective reduction of 5-aryl-10,15,20-tris(pyridyl) porphyrin to 5-aryl-10,15,20-tris(pyridyl)dihydroporphyrin (chlorin)

Dihydroporphyrins or chlorins differ from porphyrins only by saturation of a peripheral double bond of the macrocycle. However, this small structural difference leads to a significant increase of the absorption band at approximately 650 nm, which makes them very interesting candidates for photodynamic therapy applications. The reduction of porphyrins bearing two, three or four pyridyl substituents with tin(II) chloride has been developed for the synthesis of dihydroporphyrins in yields of 15–73%. The reduction of 5-(aryl)-10,15,20-tris(2 or 4-pyridyl)porphyrin with tin(II) chloride dihydrate demonstrated good regioselectivity. Porphyrins with one meso-aryl bearing one electron-donating group (EDG) gave 5-aryl-10,15,20-tris(2- or 4-pyridyl)-17,18-dihydroporphyrins in 17–72% yield. Porphyrins with one meso-aryl bearing one or more electron-withdrawing groups (EWG) gave 5-aryl-10,15,20-tris(4-pyridyl)-17,18-dihydroporphyrins or 5-aryl-10,15,20-tris(4-pyridyl)-7,8-dihydroporphyrins in 15–21% yield and isobacteriochlorin. We have also proven the possibility of functionalizing these compounds to design new regioisomerically pure photosensitizers.

Liposomal formulations of photosensitizers

Photodynamic therapy (PDT) is a clinical ablation modality to treat cancers and other diseases. PDT involves administration of a photosensitizer, followed by irradiation of target tissue with light. As many photosensitizers are small and hydrophobic, solubilization approaches and nanoscale delivery vehicles have been extensively explored. Liposomes and lipid-based formulations have been used for the past 30 years, and in some cases have been developed into well-defined commercial PDT products. This review provides an overview of common liposomal formulation strategies for photosensitizers for PDT and also photothermal therapy. Furthermore, research efforts have examined the impact of co-loading therapeutic cargo along with photosensitizers within liposomes. Additional recent approaches including imaging, overcoming hypoxia, upconversion and activatable liposomal formulations are discussed.

Current management strategy of polypoidal choroidal vasculopathy

Polypoidal choroidal vasculopathy (PCV) is a retinal disorder commonly found in Asians presenting as neovascular age-related macular degeneration and is characterized by serous macular detachment, serous or hemorrhagic pigment epithelial detachment, subretinal hemorrhage, and occasionally visible orange-red subretinal nodular lesions. PCV is diagnosed using indocyanine green angiography (ICGA), and the lesions appear as polypoidal aneurysmal vascular lesions with or without abnormal branching vascular network. Although ICGA remains the gold standard for the diagnosis of PCV, various imaging modalities have also facilitated the diagnosis and monitoring of PCV. Recent advances in imaging technology including the use of high resolution spectral domain optical coherence tomography (OCT) and OCT angiography have provided new insights on the pathogenesis of PCV, suggesting a link between PCV and pachychoroid spectrum of macular disorders. With the evolving understanding on the pathogenesis and clinical characteristics of PCV, different therapeutic options have been proposed. These include intravitreal anti-vascular endothelial growth factor (anti-VEGF) monotherapy, combination therapy with anti-VEGF and verteporfin photodynamic therapy, and thermal laser photocoagulation. In recent years, major multi-center randomized clinical trials such as EVEREST, EVEREST II, and PLANET studies have been conducted to compare the efficacy and safety of various treatment options for PCV. This review aims to summarize the results of recent literature, clinical trials and studies to provide an update on the management options of PCV. An overall management strategy for PCV will also be proposed.

Potentiation by potassium iodide reveals that the anionic porphyrin TPPS4 is a surprisingly effective photosensitizer for antimicrobial photodynamic inactivation

We recently reported that addition of the non-toxic salt, potassium iodide can potentiate antimicrobial photodynamic inactivation of a broad-spectrum of microorganisms, producing many extra logs of killing. If the photosensitizer (PS) can bind to the microbial cells, then delivering light in the presence of KI produces short-lived reactive iodine species, while if the cells are added after light the killing is caused by molecular iodine produced as a result of singlet oxygen-mediated oxidation of iodide. In an attempt to show the importance of PS-bacterial binding, we compared two charged porphyrins, TPPS4 (thought to be anionic and not able to bind to Gram-negative bacteria) and TMPyP4 (considered cationic and well able to bind to bacteria). As expected TPPS4+light did not kill Gram-negative Escherichia coli, but surprisingly when 100mM KI was added, it was highly effective (eradication at 200nM+10J/cm² of 415nm light). TPPS4 was more effective than TMPyP4 in eradicating the Gram-positive bacteria, methicillin-resistant Staphylococcus aureus and the fungal yeast Candida albicans (regardless of KI). TPPS4 was also highly active against E. coli after a centrifugation step when KI was added, suggesting that the supposedly anionic porphyrin bound to bacteria and Candida. This was confirmed by uptake experiments. We compared the phthalocyanine tetrasulfonate derivative (ClAlPCS4), which did not bind to bacteria or allow KI-mediated killing of E. coli after a spin, suggesting it was truly anionic. We conclude that TPPS4 behaves as if it has some cationic character in the presence of bacteria, which may be related to its delivery from suppliers in the form of a dihydrochloride salt.

The Noninvasive Treatment for Sentinel Lymph Node Metastasis by Photodynamic Therapy Using Phospholipid Polymer as a Nanotransporter of Verteporfin

Aim. The usefulness of photodynamic therapy (PDT) for treating sentinel lymph node (SLN) metastasis was evaluated. Materials and Methods. Verteporfin, a hydrophobic photosensitizer, forms a soluble aggregate with poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate) (PMB). The concentrations of verteporfin were determined by measuring the fluorescence emitted at 700 nm. Seven days after the inoculation of A431 cells at the forearm of BALB/c nude mice, PMB-verteporfin was injected at dorsum manus and 75 J of light energy was delivered for 1 minute. Fifty-three mice were randomly assigned to the combination of PMB-verteporfin injection and light exposure, light exposure alone, PMB-verteporfin injection alone, and no treatment groups. Ten days after PDT, brachial lymph nodes, which were considered as SLNs, were harvested and evaluated. Results. The concentration of verteporfin in SLN was significantly higher than other organs. The combination of PMB-verteporfin injection and light exposure group significantly reduced the SLN metastasis (13%) comparing with no treatment group (52%), light exposure alone group (57%), and PMB-verteporfin injection alone group (46%). Conclusions. These data suggested that PDT using PMB as a nanotransporter of verteporfin could be a minimally invasive treatment of SLN metastasis in breast cancer and represent a potential alternative procedure to SLNB.

Novel zinc phthalocyanine as a promising photosensitizer for photodynamic treatment of esophageal cancer

Photodynamic therapy (PDT) has gathered much attention in the field of cancer treatment and is increasingly used as an alternative solution for esophageal cancer therapy. However, there is a constant need for improving the effectiveness and tolerability of the applied photosensitizers (PS). Here, we propose tetra-triethyleneoxysulfonyl substituted zinc phthalocyanine (ZnPc) as a promising PS for photodynamic treatment of esophageal cancer. ZnPc-induced phototoxicity was studied in two human esophageal cancer cell lines: OE-33 (adenocarcinoma) and Kyse-140 (squamous cell carcinoma). In vitro studies focused on the uptake and intracellular distribution of the novel ZnPc as well as on its growth inhibitory potential, reactive oxygen species (ROS) formation and the induction of apoptosis. The chicken chorioallantoic membrane assay (CAM assay) and studies on native Wistar rats were employed to determine the antineoplastic and antiangiogenic activity of ZnPc-PDT as well as the tolerability and safety of non-photoactivated ZnPc in vivo. ZnPc was taken up by cancer cells in a dose- and time-dependent manner and showed a homogeneous cytoplasmic distribution. Photoactivation of ZnPc-loaded (1-10 µM) cells led to a dose-dependent growth inhibition of esophageal adenocarcinoma and squamous cell carcinoma cells of >90%. The antiproliferative effect was based on ROS-induced cytotoxicity and the induction of mitochondria-driven apoptosis. In vivo studies on esophageal tumor plaques grown on the CAM revealed pronounced antiangiogenic and antineoplastic effects. ZnPc-PDT caused long-lasting changes in the vascular architecture and a marked reduction of tumor feeding blood vessels. Animal studies confirmed the good tolerability and systemic safety of ZnPc, as no changes in immunological, behavioral and organic parameters could be detected upon treatment with the non-photoactivated ZnPc. Our findings show the extraordinary photoactive potential of the novel ZnPc as a photosensitizer for PDT of esophageal cancer.

New photosensitizers for photodynamic therapy

Photodynamic therapy (PDT) was discovered more than 100 years ago, and has since become a well-studied therapy for cancer and various non-malignant diseases including infections. PDT uses photosensitizers (PSs, non-toxic dyes) that are activated by absorption of visible light to initially form the excited singlet state, followed by transition to the long-lived excited triplet state. This triplet state can undergo photochemical reactions in the presence of oxygen to form reactive oxygen species (including singlet oxygen) that can destroy cancer cells, pathogenic microbes and unwanted tissue. The dual-specificity of PDT relies on accumulation of the PS in diseased tissue and also on localized light delivery. Tetrapyrrole structures such as porphyrins, chlorins, bacteriochlorins and phthalocyanines with appropriate functionalization have been widely investigated in PDT, and several compounds have received clinical approval. Other molecular structures including the synthetic dyes classes as phenothiazinium, squaraine and BODIPY (boron-dipyrromethene), transition metal complexes, and natural products such as hypericin, riboflavin and curcumin have been investigated. Targeted PDT uses PSs conjugated to antibodies, peptides, proteins and other ligands with specific cellular receptors. Nanotechnology has made a significant contribution to PDT, giving rise to approaches such as nanoparticle delivery, fullerene-based PSs, titania photocatalysis, and the use of upconverting nanoparticles to increase light penetration into tissue. Future directions include photochemical internalization, genetically encoded protein PSs, theranostics, two-photon absorption PDT, and sonodynamic therapy using ultrasound.

Half-dose photodynamic therapy followed by diode micropulse laser therapy as treatment for chronic central serous chorioretinopathy: evaluation of a prospective treatment protocol

PURPOSE

To evaluate the outcome of a prospective protocol for the treatment of chronic central serous chorioretinopathy (CSC).

METHODS

Interventional prospective case series in 59 eyes (59 patients) with active chronic CSC. All patients were first treated with indocyanine green angiography (ICGA)-guided half-dose photodynamic therapy (PDT). In case of persistent serous subretinal fluid (SRF) after a follow-up period of at least 6 weeks, ICGA-guided PDT was repeated. If the SRF persisted after two PDT treatments, additional ICGA-guided high-density subthreshold diode micropulse laser (HSML) therapy was performed. Clinical evaluation included best-corrected visual acuity (BCVA), fundoscopy, OCT, fundus autofluorescence, fluorescein angiography and ICGA.

RESULTS

After a single PDT treatment, complete resolution of SRF was seen in 37 of 59 eyes. Of the 22 eyes with no complete resolution of SRF, 19 eyes received a second PDT treatment, after which seven eyes of the 19 eyes showed a complete resolution of SRF. Ten eyes underwent HSML, of which one eye had complete resolution of SRF within 7 weeks. At final follow-up a complete resolution of SRF was present in 80% of all eyes. The mean BCVA improved from 0.28 logMAR at baseline to 0.16 logMAR at final follow-up. Improvement of BCVA was highest after the first treatment (-0.12 logMAR, p < 0.001).

CONCLUSIONS

The proposed treatment strategy using half-dose PDT and HSML in active chronic CSC resulted in an anatomical success rate of 80%. The first half-dose PDT treatment has the highest likelihood of a favourable treatment response on OCT and BCVA increase.

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.

Comparing half-dose photodynamic therapy with high-density subthreshold micropulse laser treatment in patients with chronic central serous chorioretinopathy (the PLACE trial): study protocol for a randomized controlled trial

Background

Chronic central serous chorioretinopathy (cCSC) is an eye disease characterized by an accumulation of serous fluid under the retina. It is postulated that this fluid accumulation results from hyperpermeability and swelling of the choroid, the underlying vascular tissue of the eye, causing a dysfunction of the retinal pigment epithelium. This fluid accumulation causes neuroretinal detachment. A prolonged neuroretinal detachment in the macula can lead to permanent vision loss. Therefore, treatment is aimed primarily at achieving resolution of subretinal fluid, preferably within the first 4 months after diagnosis of the disease. A broad spectrum of treatment modalities has been investigated in cCSC, but no consensus exists on the optimal treatment of cCSC. Currently, photodynamic therapy (PDT) and high-density subthreshold micropulse laser treatment (HSML) are among the most frequently cited treatments in obtaining successful neuroretinal reattachment.

Methods/Design

This is a randomized, controlled, open-label, multicenter trial comparing the efficacy of half-dose PDT to HSML in treating patients with cCSC. A total of 156 patients will be recruited, 78 patients in each treatment arm, with a maximum follow-up duration of 8 months after the first treatment. A complete ophthalmological examination with vision-related quality of life (NEI VFQ-25) and stress questionnaires, will be performed at baseline, 6 to 8 weeks after the first treatment, 6 to 8 weeks after a second treatment (if necessary), and at the final follow-up visit at 7 to 8 months after the first treatment. Treatment visits will be scheduled within 3 weeks after the baseline visit, and within 3 weeks after the first control visit, if a second treatment is required.

Discussion

Both half-dose PDT and HSML may be effective treatments in cCSC, but because of the lack of prospective randomized controlled trials, which treatment should be the first choice remains unclear. The aim of this study is to compare the efficacy of half-dose PDT to HSML. The primary endpoint to evaluate efficacy will be a complete absence of subretinal fluid on optical coherence tomography after treatment. Secondary functional endpoints include change in Early Treatment Diabetic Retinopathy Study (ETDRS) best-corrected visual acuity, retinal sensitivity on microperimetry, and NEI VFQ-25 questionnaire of visual functioning.

Registration number Institutional Review Board (CMO Arnhem-Nijmegen, the Netherlands): 2013/203 NL nr.: 41266.091.13

Trial registration

ClinicalTrials.gov identifier: NCT01797861. Date of registration: 21 February 2013.

Impact of vitreomacular adhesion on ranibizumab mono- and combination therapy for neovascular age-related macular degeneration

PURPOSE

To investigate the influence of vitreomacular adhesion on the efficacy of pro re nata (PRN) ranibizumab monotherapy and verteporfin photodynamic therapy (PDT) combination therapy for neovascular age-related macular degeneration.

DESIGN

Post hoc analysis of prospective randomized 12-month multicenter clinical trial data.

METHODS

PATIENT POPULATION

Total of 255 treatment-naïve patients with subfoveal choroidal neovascularization.

OBSERVATION PROCEDURE

Assessment of the vitreomacular interface on monthly optical coherence tomography with division of patients into the following categories according to continuous 1-year grading: posterior vitreous detachment (n=154), dynamic release of vitreomacular adhesion (n=32), stable vitreomacular adhesion (n=51).

MAIN OUTCOME MEASURES

Mean best-corrected visual acuity (BCVA) letter and central retinal thickness changes at month 12 in the vitreomacular interface groups.

RESULTS

Mean BCVA changes at month 12 were +3.5 (posterior vitreous detachment), +4.3 (release of vitreomacular adhesion), and +6.3 (vitreomacular adhesion) in patients receiving monotherapy (P=.767), and +0.1 (posterior vitreous detachment), +6.6 (release of vitreomacular adhesion), and +9.2 (vitreomacular adhesion) in patients receiving combination therapy (P=.009). Mean central retinal thickness changes were -113 μm (posterior vitreous detachment), -89 μm (release of vitreomacular adhesion), and -122 μm (vitreomacular adhesion) in monotherapy (P=.725) and -121 μm (posterior vitreous detachment), -113 μm (release of vitreomacular adhesion), and -113 μm (vitreomacular adhesion) in combination therapy (P=.924). Mean ranibizumab retreatments during 12 months were 4.9 (posterior vitreous detachment), 6.6 (release of vitreomacular adhesion), and 5.3 (vitreomacular adhesion) in monotherapy (P=.018) and 4.7 (posterior vitreous detachment), 5.2 (release of vitreomacular adhesion), and 5.8 (vitreomacular adhesion) in combination therapy (P=.942).

CONCLUSION

This study adds evidence that the vitreomacular interface status impacts functional outcomes and retreatment requirements. Patients with posterior vitreous detachment achieve acceptable results with fewer injections in PRN monotherapy, but lose potential vision gain with PDT. Patients with other vitreomacular interface configurations may potentially achieve optimized vision outcomes by combination of antiangiogenic treatment and vaso-occlusive PDT.

The effect of photodynamic therapy on cisterna chyli patency in rats

OBJECTIVE

To radiographically and histologically evaluate the effects of photodynamic therapy on the cisterna chyli in rats.

STUDY DESIGN

Experimental study.

ANIMALS

Adult male Sprague-Dawley rats (n = 60).

METHODS

Cecal lymph nodes were injected with the photodynamic compound verteporfin. A 690 nm, 500 mW diode laser was then directed at the area of the cisterna chyli for either 0, 1.5, or 3 minutes. Cisterna chyli patency was evaluated using lymphography, and histologic changes were evaluated on postoperative Days 1, 3, 5, 7, and 14.

RESULTS

Histologically, minimal to marked injury to the cisternal and/or pericisternal tissues was present in all treated rats at all time periods. Radiographically, 8/20 cisternae were occluded in the 1.5-minute treatment group (including 1/4 on Day 1, 2/4 on Day 3, 3/4 on Day 5, 0/4 on Day 7, and 2/4 on Day 14), and 9/20 cisternae were occluded in the 3-minute treatment group (including 0/4 on Day 1, 1/4 on Day 3, 3/4 on Day 5, 3/4 on Day 7, and 2/4 on Day 14). There was minimal to no histologic evidence of tissue injury in control rats. All control cisternae were radiographically open.

CONCLUSIONS

Further investigations into the timing of laser application and light dose, or alternative photodynamic agents are required to limit injury to adjacent tissues and to improve the effectiveness of cisternal photoablation.

Anticancer activity of cationic porphyrins in melanoma tumour-bearing mice and mechanistic in vitro studies

Background

Porphyrin TMPyP4 (P4) and its C₁₄H₂₈-alkyl derivative (C14) are G-quadruplex binders and singlet oxygen (¹O₂) generators. In contrast, TMPyP2 (P2) produces ¹O₂ but it is not a G-quadruplex binder. As their photosensitizing activity is currently undefined, we report in this study their efficacy against a melanoma skin tumour and describe an in vitro mechanistic study which gives insights into their anticancer activity.

Methods

Uptake and antiproliferative activity of photoactivated P2, P4 and C14 have been investigated in murine melanoma B78-H1 cells by FACS, clonogenic and migration assays. Apoptosis was investigated by PARP-1 cleavage and annexin-propidium iodide assays. Biodistribution and in vivo anticancer activity were tested in melanoma tumour-bearing mice. Porphyrin binding and photocleavage of G-rich mRNA regions were investigated by electrophoresis and RT-PCR. Porphyrin effect on ERK pathway was explored by Western blots.

Results

Thanks to its higher lipophylicity C14 was taken up by murine melanoma B78-H1 cells up to 30-fold more efficiently than P4. When photoactivated (7.2 J/cm²) in B78-H1 melanoma cells, P4 and C14, but not control P2, caused a strong inhibition of metabolic activity, clonogenic growth and cell migration. Biodistribution studies on melanoma tumour-bearing mice showed that P4 and C14 localize in the tumour. Upon irradiation (660 nm, 193 J/cm²), P4 and C14 retarded tumour growth and increased the median survival time of the treated mice by ~50% (P <0.01 by ANOVA), whereas porphyrin P2 did not. The light-dependent mechanism mediated by P4 and C14 is likely due to the binding to and photocleavage of G-rich quadruplex-forming sequences within the 5′-untranslated regions of the mitogenic ras genes. This causes a decrease of RAS protein and inhibition of downstream ERK pathway, which stimulates proliferation. Annexin V/propidium iodide and PARP-1 cleavage assays showed that the porphyrins arrested tumour growth by apoptosis and necrosis. C14 also showed an intrinsic light-independent anticancer activity, as recently reported for G4-RNA binders.

Conclusions

Porphyrins P4 and C14 impair the clonogenic growth and migration of B78-H1 melanoma cells and inhibit melanoma tumour growth in vivo. Evidence is provided that C14 acts through light-dependent (mRNA photocleavage) and light-independent (translation inhibition) mechanisms.

Structure-function relationships of Nile blue (EtNBS) derivatives as antimicrobial photosensitizers

The benzophenothiazinium dye EtNBS has previously been tested as a photosensitizer to mediate photodynamic therapy (PDT). It has been employed to kill cancer cells and microbial cells in vitro and to treat tumors and infections in vivo. We synthesized a panel of derivatives substituted at the 1-position of the benzene ring with electron donating or electron withdrawing groups (amino, acetamido and nitro) and tested their production of reactive oxygen species (ROS) and light-mediated killing of two species of Gram-positive and two species of Gram-negative bacteria. All three compounds showed lower fluorescence, lower yield of ROS and less microbial killing than parent EtNBS, while the order of activity (nitro > amino > acetamido) showed that an electron withdrawing substituent was better than electron donating. To test the hypothesis that 1-substitution distorts the planar structure of the conjugated rings we compared two compounds substituted with N-ethylpropylsulfonamido either at the 1-position or at the 4-position. The 4-isomer was significantly more photoactive than the 1-isomer. We also prepared an EtNBS derivative with a guanidinium group attached to the 5-amino group. This compound had high activity against Gram-negative bacteria due to the extra positive charge. Cellular uptake of the compounds by the four bacterial species was also measured and broadly correlated with activity. These results provided three separate pieces of structure-activity relationship data for antimicrobial photosensitizers based on the EtNBS backbone.

Current status of liposomal porphyrinoid photosensitizers

The complete eradication of various targets, such as infectious agents or cancer cells, while leaving healthy host cells untouched, is still a great challenge faced in the field of medicine. Photodynamic therapy (PDT) seems to be a promising approach for anticancer treatment, as well as to combat various dermatologic and ophthalmic diseases and microbial infections. The application of liposomes as delivery systems for porphyrinoids has helped overcome many drawbacks of conventional photosensitizers and facilitated the development of novel effective photosensitizers that can be encapsulated in liposomes. The development, preclinical studies and future directions for liposomal delivery of conventional and novel photosensitizers are reviewed.

An Update on the Diagnosis and Management of Central Serous Chorioretinopathy

Central serous chorioretinopathy (CSC) is a complicated disease with still unclear causes, pathogenesis and management strategy despite active research. CSC has been traditionally considered as a self-limiting disease where spontaneous recovery occurs in 90% of the patients within a few months. This proclaimed "benign" nature of CSC, however, has been queried by increasing scientific evidence that permanent photoreceptors damage and neurosensory-cystoid degeneration of macula occur in the event of chronic CSC. CSC is probably not a benign disease. Treatments for CSC are still evolving. It is very difficult to define the proper timing for active treatment of CSC because it is not easy to define a universally accepted cut-off time point for active intervention. There is a recent suggestion that active CSC treatment should be considered if symptoms last longer than 3 months as atrophy of photoreceptors may occur as early as 4 months after initial presentation. The CSC patients may be stratified into two groups based on the initial presenting visual acuity and duration of symptom: the good visual prognosis group and the dubious visual prognosis group. The management may then be tailor-made based on the visual prognosis group. "Safety-enhanced'" photodynamic therapy (PDT) using lower doses and reduced fluence is still the mainstay of treatment. Newer treatment modalities like intravitreal anti-VEGF therapy, micropulsed diode laser treatment, and the use of corticosteroid antagonists do warrant further investigation. Combination therapies involving two or more of the above modalities of treatments may have a role to play in this actively researched area.

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.

Photodynamic therapy using an anti-EGF receptor antibody complexed with verteporfin nanoparticles: a proof of concept study

Photodynamic therapy (PDT) is a noninvasive optical treatment method in which the topical or systemic delivery of photosensitizing drugs is followed by irradiation with broadband red light. Coupling photosensitizers with a specific antibody may allow this approach to target specific cancers. This study determines the antitumor efficacy of coupling verteporfin (Visudyne(®)), a hydrophobic polyporphryin oligomer, with an antiepidermal growth factor receptor (anti-EGFR) antibody. Poly[2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate-co-p-nitrophenylcarbonyloxyethyl methacrylate] (PMBN) was conjugated with an anti-EGFR antibody and mixed with verteporfin (verteporfin-PMBN-antibody complex). Tumor-bearing mice were intravenously injected with the verteporfin-PMBN-antibody complex or verteporfin plus PMBN without the antibody. Irradiation was conducted at 640 nm with a dose of 75 J/cm(2). The fluorescence intensity in A431 cells in vitro was threefold higher after exposure to verteporfin-PMBN-antibody complex than after exposure to verteporfin-PMBN. In A431 tumor-bearing mice, the intratumor concentration of verteporfin was 9.4 times higher than that of the skin, following administration of the verteporfin-PMBN-antibody complex. Tumor size significantly decreased within 8 days in mice treated with verteporfin-PMBN-antibody complex compared with those treated with verteporfin-PMBN. PDT using a PMBN-verteporfin-antibody complex offers a promising anticancer therapy.

Vascular regrowth following photodynamic therapy in the chicken embryo chorioallantoic membrane

Photodynamic therapy (PDT) induces damage to the endothelium, which can lead to increased vascular permeability and, under intensive PDT conditions, even to platelet aggregation, vasoconstriction, and blood flow stasis. Eventually, ischemia, hypoxia, and inflammation can occur, resulting in angiogenesis. We studied the sequence of the vascular events after Visudyne^®-PDT in the chicken chorioallantoic membrane (CAM) at day 11 of development. Using epi-fluorescence microscopy, we monitored the regrowth of capillaries in the PDT treated area. Immediately after irradiation, the treatment resulted in blood flow arrest. And 24 h post PDT, sprouting of new blood vessels was observed at the edge of the PDT zone. Neovessels looping out from the edge of the PDT zone gave rise to specialized endothelial tip structures guiding the vessels towards the center of the treated area. At 48 h almost all of the treated area was repopulated with functional but morphologically altered vasculature. These observations also showed reperfusion of some of the vessels that had been closed by the PDT treatment. CAM samples were immunohistochemically stained for Ki-67 showing proliferation of endothelial cells in the PDT area. Also, several markers of immature and angiogenic blood vessels, such as αVβ3-integrin, vimentin and galectin-1, were found to be enhanced in the PDT area, while the endothelial maturation marker intercellular adhesion molecule (ICAM)-1 was found to be suppressed. These results demonstrate that the new vascular bed is formed by both neo-angiogenesis and reperfusion of existing vessels. Both the quantitative real-time RT–PCR profile and the response to pharmacological treatment with Avastin^®, an inhibitor of angiogenesis, suggest that angiogenesis occurs after PDT. The observed molecular profiling results and the kinetics of gene regulation may enable optimizing combination therapies involving PDT for treatment of cancer and other diseases.

Effects of photodynamic therapy using hematoporphyrin monomethyl ether on experimental choroidal neovascularization

Hematoporphyrin monomethyl ether (HMME) is a novel and promising second-generation porphyrin-related photosensitizer for photodynamic therapy (PDT). To study the effects of HMME PDT on choroidal neovascularization (CNV) in rats, the PDT was performed 20 min after HMME bolus injection, which was investigated prior to the PDT by fluorescence microscopy with laser-induced CNV, and delivered at an irradiance of 400, 600 and 1000 mW cm(-2) corresponding to a fluence of 36, 54, 90 J cm(-2) in PDT plan I (15 mg kg(-1) HMME). In PDT plan II (30 mg kg(-1) HMME), the laser had a constant irradiance of 600 mW cm(-2), which was delivered for 60, 90 or 150 s, to also achieve total energy doses of 36, 54 or 90 J cm(-2). CNV closure rates assessed by fluorescein angiography and histologic damage to treated areas of choroid and retina varied as a function of the dose of HMME and of the activating light energy fluence. Endothelial cell labeled by platelet/endothelial cell adhesion molecule-1 presented treated CNV lesions that were significantly reduced in size (P < 0.01). It can be concluded that PDT using HMME can effectively occlude CNV. HMME is a potentially useful photosensitizer for the reduction in CNV size of irradiated areas.