Phototherapy of cancer and atheromatous plaque with texaphyrins

Photodynamic Therapy and Cardiovascular Diseases

Cardiovascular diseases are the third most common cause of death in the world. The most common are heart attacks and stroke. Cardiovascular diseases are a global problem monitored by many centers, including the World Health Organization (WHO). Atherosclerosis is one aspect that significantly influences the development and management of cardiovascular diseases. Photodynamic therapy (PDT) is one of the therapeutic methods used for various types of inflammatory, cancerous and non-cancer diseases. Currently, it is not practiced very often in the field of cardiology. It is most often practiced and tested experimentally under in vitro experimental conditions. In clinical practice, the use of PDT is still rare. The aim of this review was to characterize the effectiveness of PDT in the treatment of cardiovascular diseases. Additionally, the most frequently used photosensitizers in cardiology are summarized.

Photodynamic Therapy for Atherosclerosis

Atherosclerosis, which currently contributes to 31% of deaths globally, is of critical cardiovascular concern. Current diagnostic tools and biomarkers are limited, emphasizing the need for early detection. Lifestyle modifications and medications form the basis of treatment, and emerging therapies such as photodynamic therapy are being developed. Photodynamic therapy involves a photosensitizer selectively targeting components of atherosclerotic plaques. When activated by specific light wavelengths, it induces localized oxidative stress aiming to stabilize plaques and reduce inflammation. The key advantage lies in its selective targeting, sparing healthy tissues. While preclinical studies are encouraging, ongoing research and clinical trials are crucial for optimizing protocols and ensuring long-term safety and efficacy. The potential combination with other therapies makes photodynamic therapy a versatile and promising avenue for addressing atherosclerosis and associated cardiovascular disease. The investigations underscore the possibility of utilizing photodynamic therapy as a valuable treatment choice for atherosclerosis. As advancements in research continue, photodynamic therapy might become more seamlessly incorporated into clinical approaches for managing atherosclerosis, providing a blend of efficacy and limited invasiveness.

Pyrrole-based photosensitizers for photodynamic therapy — a Thomas Dougherty award paper

Photodynamic therapy (PDT) is a therapeutic modality that uses light to treat malignant or benign diseases. A photosensitizer, light, and oxygen are the three main components needed to generate a cytotoxic effect. Pyrrole-based photosensitizers have been widely used for PDT. Many of the photosensitizers within this class are macrocyclic. This is particularly true for systems that have received regulatory approval or been the subject of clinical trials. However, in recent years, a number of boron dipyrromethanes (BODIPY) have been studied as photosensitizers. Herein, we review examples of some of the most relevant pyrrole-based photosensitizers.

An update in clinical utilization of photodynamic therapy for lung cancer

Lung cancer is one of the leading causes of cancer-related death worldwide, with nearly 1.8 million-diagnosis and 1.59 million deaths. Surgery, radiotherapy, and chemotherapy in individual or combination are commonly used to treat lung cancers. Photodynamic therapy (PDT) is a highly selective method for the destruction of cancer cells by exerting cytotoxic activity on malignant cells. PDT has been the subject of numerous clinical studies and has proven to be an effective strategy for cancer therapy. Clinical studies revealed that PDT could prolong survival in patients with inoperable cancers and significantly improve quality of life. For inoperable lung cancer cases, PDT could be an effective therapy. Despite the clinical success reported, PDT is still currently underutilized to treat lung cancer and other tumors. PTD is still a new treatment approach for lung cancer mainly due to the lack of enough clinical research evaluating its' effectiveness and side effects. In this review, we discuss the current prospects and future potentials of PDT in lung cancer treatment.

Applications of inorganic nanoparticles in the diagnosis and therapy of atherosclerosis

Atherosclerosis is a chronic progressive disease, which may result in serious clinical outcomes, such as acute heart events or stroke with high mortality. At present, the clinical problems of atherosclerosis mainly consist of the difficulty in confirming the plaques or identifying the stability of the plaques in the early phase and the shortage of valid treatments. Fortunately, with the development of nanotechnology, various inorganic nanoparticles with imaging enhancement and noninvasive therapy functions have been studied in the imaging and treatment of atherosclerosis, which has brought new hope to patients. This review focuses on the recent progress in the use of inorganic nanoparticles in the diagnosis and therapy of atherosclerosis, including the key processes in the development of atherosclerosis and the mainly involved cells, inorganic nanoparticle-based dual-mode imaging methods classified by the types of targeting cells, and inorganic nanoparticle-based therapeutic approaches, such as photothermal therapy (PTT), photodynamic therapy (PDT), sonodynamic therapy (SDT), drug delivery, gene therapy and imaging-guided therapy for atherosclerosis. Finally, this review discusses the challenges and directions of inorganic nanoparticles in potential clinical translation of anti-atherosclerosis in future. We believe this review will enable readers to systematically understand the progress of the inorganic nanoparticle-based imaging and therapy of atherosclerosis and therefore promote the further development of anti-atherosclerosis.

Exogenous imaging contrast and therapeutic agents for intravascular photoacoustic imaging and image-guided therapy

Intravascular photoacoustic (IVPA) imaging has been developed in recent years as a viable imaging modality for the assessment of atherosclerotic plaques. Exogenous imaging contrast and therapeutic agents further enhance this imaging modality and provide significant benefits. Imaging contrast agents can significantly increase photoacoustic signal, resulting in enhanced plaque detection and characterization. The ability to use these particles to molecularly target markers of disease progression makes it possible to determine patient-specific levels of risk and plan treatments accordingly. With improved diagnosis, clinicians will be able to use therapeutic agents that are synergistic with IVPA imaging to treat atherosclerotic patients. Pre-clinical and clinical studies with relevance to IVPA imaging have shown promise in the area of diagnosis and therapeutics. In this review, we present a variety of imaging contrast agents that are either designed for or are compatible with IVPA imaging, cover uses of therapeutic agents that compliment this imaging modality, and discuss future directions of research in the field.

Some activities of PorphyChem illustrated by the applications of porphyrinoids in PDT, PIT and PDI

Photodynamic therapy is an innovative approach to treat diverse cancers and diseases that involves the use of photosensitizing agents along with light of an appropriate wavelength to generate cytotoxic reactive oxygen species.

Photodynamic therapy for the treatment of atherosclerotic plaque: Lost in translation?

Acute coronary syndrome is a life-threatening condition of utmost clinical importance, which, despite recent progress in the field, is still associated with high morbidity and mortality. Acute coronary syndrome results from a rupture or erosion of vulnerable atherosclerotic plaque with secondary platelet activation and thrombus formation, which leads to partial or complete luminal obstruction of a coronary artery. During the last decade, scientific evidence demonstrated that when an acute coronary event occurs, several nonculprit plaques are in a "vulnerable" state. Among the promising approaches, several investigations provided evidence of photodynamic therapy (PDT)-induced stabilization and regression of atherosclerotic plaque. Significant development of PDT strategies improved its therapeutic outcome. This review addresses PDT's pertinence and major problems/challenges toward its translation to a clinical reality.

Evaluation of Antimicrobial Photodynamic Therapy against Streptococcus mutans Biofilm in situ

AIM

This study investigated the effect of antimicrobial photo-dynamic therapy (aPDT) over Streptococcus mutans biofilm.

MATERIALS AND METHODS

Eighteen (n = 18) patients were selected and one palatine device with dental blocks was used. The biofilm was treated by curcumin and Photogem® with a LED and the effect was analyzed by CFU/ml.

RESULTS

Although, statistical analysis showed significant reductions for aPDT mainly with Photogem® (p = 0.02), these were low.

CONCLUSION

The results suggest a low antimicrobial effect of aPDT over S. mutans biofilm. Some parameters used need to be improved.

CLINICAL SIGNIFICANCE

This technique can be a promising in Dentistry.

Photodynamic therapy: current status and future directions

Photodynamic therapy (PDT) is a minimally invasive therapeutic modality used for the management of a variety of cancers and benign diseases. The destruction of unwanted cells and tissues in PDT is achieved by the use of visible or near-infrared radiation to activate a light-absorbing compound (a photosensitizer, PS), which, in the presence of molecular oxygen, leads to the production of singlet oxygen and other reactive oxygen species. These cytotoxic species damage and kill target cells. The development of new PSs with properties optimized for PDT applications is crucial for the improvement of the therapeutic outcome. This review outlines the principles of PDT and discusses the relationship between the structure and physicochemical properties of a PS, its cellular uptake and subcellular localization, and its effect on PDT outcome and efficacy.

Photosensitization of in vitro biofilms formed on denture base resin

STATEMENT OF PROBLEM

Proper sterilization or disinfection of removable prostheses and surgical guides has been problematic in dental practice because of the absence of simple and low-cost techniques that do not cause damage to acrylic resins.

PURPOSE

The purpose of this study was to study the effect of photodynamic therapy against Streptococcus mutans, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans biofilms formed on acrylic resin specimens.

MATERIAL AND METHODS

The specimens were sterilized in ethylene oxide gas and submitted to in vitro biofilm growth. The photodynamic therapy consisted of the application of 0.05% methylene blue (P+) conjugated to irradiation with a light-emitting-diode of 630 nm and 150 mW (L+). The specimens were randomly divided into groups (n=5): negative control (P-L-); stained and irradiated at 10 J/cm(2) (P+L+ 10); stained and irradiated at 30 J/cm(2) (P+L+ 30); stained and not irradiated (P+L-); not stained and irradiated at 10 J/cm(2) (P-L+ 10); not stained and irradiated at 30 J/cm(2) (P-L+ 30); and gold standard (GS), sterilized. Afterward, the specimens were submitted to contact with culture medium agar for 10 minutes in petri plates, which were incubated for 48 hours at 37°C. The number of colony-forming units was obtained, and the data were expressed according to scores (1=0; 2=1-10; 3=11-100; 4=101-1000) and analyzed by the Friedman and Dunn tests (α=.05).

RESULTS

Streptococcus mutans was sensitized by (P+L-); P aeruginosa and C albicans were also sensitized by the dye but showed a slight microbial reduction with (P+L+ 30), as did S aureus (P>.05); E coli presented an initial score of 3 and achieved a bacterial reduction to score 2 with (P+L+ 30) (P=.039).

CONCLUSIONS

Photodynamic therapy was effective in reducing E coli counts on biofilms formed on acrylic resin specimens. The inhibition of microorganism growth tended to be directly proportional to the amount of energy provided by the light-emitting diode.

Effect of molecular characteristics on cellular uptake, subcellular localization, and phototoxicity of Zn(II) N-alkylpyridylporphyrins

Tetra-cationic Zn(II) meso-tetrakis(N-alkylpyridinium-2 (or -3 or -4)-yl)porphyrins (ZnPs) with progressively increased lipophilicity were synthesized to investigate how the tri-dimensional shape and lipophilicity of the photosensitizer (PS) affect cellular uptake, subcellular distribution, and photodynamic efficacy. The effect of the tri-dimensional shape of the molecule was studied by shifting the N-alkyl substituent attached to the pyridyl nitrogen from ortho to meta and para positions. Progressive increase of lipophilicity from shorter hydrophilic (methyl) to longer amphiphilic (hexyl) alkyl chains increased the phototoxicity of the ZnP PSs. PS efficacy was also increased for all derivatives when the alkyl substituents were shifted from ortho to meta, and from meta to para positions. Both cellular uptake and subcellular distribution of the PSs were affected by the lipophilicity and the position of the alkyl chains on the periphery of the porphyrin ring. Whereas the hydrophilic ZnPs demonstrated mostly lysosomal distribution, the amphiphilic hexyl derivatives were associated with mitochondria, endoplasmic reticulum, and plasma membrane. A comparison of hexyl isomers revealed that cellular uptake and partition into membranes followed the order para > meta > ortho. Varying the position and length of the alkyl substituents affects (i) the exposure of cationic charges for electrostatic interactions with anionic biomolecules and (ii) the lipophilicity of the molecule. The charge, lipophilicity, and the tri-dimensional shape of the PS are the major factors that determine cellular uptake, subcellular distribution, and as a consequence, the phototoxicity of the PSs.

The changing face of vascular interventional radiology: the future role of pharmacotherapies and molecular imaging

Interventional radiology has had to evolve constantly because there is the ever-present competition and threat from other specialties within medicine, surgery, and research. The development of new technologies, techniques, and therapies is vital to broaden the horizon of interventional radiology and to ensure its continued success in the future. In part, this change will be due to improved chronic disease prevention altering what we treat and in whom. The most important of these strategies are the therapeutic use of statins, Beta-blockers, angiotensin-converting enzyme inhibitors, and substances that interfere with mast cell degeneration. Molecular imaging and therapeutic strategies will move away from conventional techniques and nano and microparticle molecular technology, tissue factor imaging, gene therapy, endothelial progenitor cells, and photodynamic therapy will become an important part of interventional radiology of the future. This review looks at these new and exciting technologies.

3.0-T MR imaging of intracoronary local delivery of motexafin gadolinium into coronary artery walls

PURPOSE

To develop a technique with clinical 3.0-T magnetic resonance (MR) imaging to delineate local contrast agent distribution in coronary artery walls for potential molecular MR imaging-guided local gene or drug therapy of atherosclerotic coronary artery disease.

MATERIALS AND METHODS

This animal protocol was approved by the institutional animal care and use committee and was in compliance with the Guide for the Care and Use of Laboratory Animals. For in vitro confirmation, human arterial smooth muscle cells (SMCs) were used to determine capability of SMCs in uptake of motexafin gadolinium (MGd) and its optimal dose. For ex vivo evaluation, a 2-mL mixture of MGd and trypan blue was locally infused into coronary artery walls of six cadaveric pig hearts with MR monitoring and an MR imaging guidewire, surface coils, or both. For in vivo validation, the balloon catheter was placed into coronary arteries of seven living pigs, and the MGd and trypan blue mixture was infused into arterial walls with MR guidance. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of coronary artery walls were recorded by using different coils between pre- and postcontrast infusion, with subsequent histologic confirmation. Paired Student t tests were used to compare average SNRs and CNRs of arterial walls before and after contrast agent infusion with different coils.

RESULTS

SMCs could take up MGd with the optimal concentration at 150 µmol/L. Average SNR with the MR imaging guidewire and surface coil combination was significantly higher than that with the MR imaging guidewire only or with surface coils only (P < .05), and average SNR and CNR of postinfusion MR imaging was significantly higher than that of preinfusion MR imaging (P < .05). Histologic analysis was used to confirm successful intracoronary infiltration of MGd and trypan blue within coronary artery walls.

CONCLUSION

MR imaging can be used to delineate locally infused contrast agent distribution in coronary artery walls. This establishes groundwork for development of molecular MR imaging-guided intracoronary therapy.

Texaphyrins: a new approach to drug development

The texaphyrins are prototypical metal-coordinating expanded porphyrins. They represent a burgeoning class of pharmacological agents that show promise for an array of medical applications. Currently, two different water-soluble lanthanide texaphyrins, namely motexafin gadolinium ( Gd-Tex , 1) and motexafin lutetium ( Lu-Tex , 2), are involved in multi-center clinical trials for a variety of indications. The first of these agents, XCYTRIN® (motexafin gadolinium) Injection, is being evaluated as a potential X-ray radiation enhancer in a randomized Phase III clinical trial in patients with brain metastases. The second, in various formulations, is being evaluated as a photosensitizer for use in: (i) the photodynamic treatment of recurrent breast cancer (LUTRIN® Injection; now in Phase IIb clinical trials); (ii) photoangioplastic reduction of atherosclerosis involving peripheral and coronary arteries (ANTRIN® Injection; now in Phase II and Phase I clinical trials, respectively); and (iii) light-based age-related macular degeneration (OPTRIN™ Injection; currently under Phase II clinical evaluation), a vision-threatening disease of the retina. In this article, these developments, along with fundamental aspects of the underlying chemistry are reviewed.

Effects of photodynamic exposure on endothelial cells in vitro

Experiments on cultured human umbilical vein endotheliocytes showed that accumulation of photosensitive dye (aluminum phthalocyanin; PHOTOSENSE) in cells and laser exposure alone were inessential for the viability of endothelial cells. Contrary to this, exposure of the cells which have accumulated aluminum phthalocyanin (an average of 111.1 ng/mg protein) to low-intensity laser (λ=675 nm) led to a dose-dependent reduction of endotheliocyte viability. Hence, cultured endothelial cells can be used for screening of various photosensitizers and preliminary optimization of photodynamic therapy.

Waterproof AlInGaP optoelectronics on stretchable substrates with applications in biomedicine and robotics

Inorganic light-emitting diodes and photodetectors represent important, established technologies for solid-state lighting, digital imaging and many other applications. Eliminating mechanical and geometrical design constraints imposed by the supporting semiconductor wafers can enable alternative uses in areas such as biomedicine and robotics. Here we describe systems that consist of arrays of interconnected, ultrathin inorganic light-emitting diodes and photodetectors configured in mechanically optimized layouts on unusual substrates. Light-emitting sutures, implantable sheets and illuminated plasmonic crystals that are compatible with complete immersion in biofluids illustrate the suitability of these technologies for use in biomedicine. Waterproof optical-proximity-sensor tapes capable of conformal integration on curved surfaces of gloves and thin, refractive-index monitors wrapped on tubing for intravenous delivery systems demonstrate possibilities in robotics and clinical medicine. These and related systems may create important, unconventional opportunities for optoelectronic devices.

Photosensitizing action of isomeric zincN-methylpyridylporphyrins in human carcinoma cells

The success of photodynamic therapy (PDT), as a minimally invasive approach, in treating both neoplastic and non-neoplastic diseases has stimulated the search for new compounds with potential application in PDT. We have previously reported that Zn(II) N-alkylpyridylporphyrins (ZnTM-2(3,4)-PyP(4+) and ZnTE-2-PyP(4+)) can act as photosensitizers and kill antibiotic-resistant bacteria. This study investigated the photosensitizing effects of the isomers of ZnTMPyP(4+) (ZnTM-2(3,4)-PyP(4+)) and respective ligands on a human colon adenocarcinoma cell line. At 10 microM and 30 min of illumination the isomeric porphyrins completely inhibited cell growth, and at 20 microM killed approximately 50% of the cancer cells. All these effects were entirely light-dependent. The isomers of the ZnTMPyP(4+) and the respective ligands show high photosensitizing efficiency and no toxicity in the dark. Their efficacy as photosensitizers is comparable to that of hematoporphyrin derivative (HpD).

Designing photosensitizers for photodynamic therapy: strategies, challenges and promising developments

Photodynamic therapy (PDT) and photodynamic antimicrobial chemotherapy (PACT) are techniques that combine the effects of visible light irradiation with subsequent biochemical events that arise from the presence of a photosensitizing drug (possessing no dark toxicity) to cause destruction of selected cells. Despite its still widespread clinical use, Photofrin® has several drawbacks that limit its general clinical use. Consequently, there has been extensive research into the design of improved alternative photosensitizers aimed at overcoming these drawbacks. While there are many review articles on the subject of PDT and PACT, these have focused on the photosensitizers that have been used clinically, with little emphasis placed on how the chemical aspects of the molecule can affect their efficacy as PDT agents. Indeed, many of the PDT/PACT agents used clinically may not even be the most appropriate within a given class. As such, this review aims to provide a better understanding of the factors that have been investigated, while aiming at improving the efficacy of a molecule intended to be used as a photosensitizer. Recent publications, spanning the last 5 years, concerning the design, synthesis and clinical usage of photosensitizers for application in PDT and PACT are reviewed, including 5-aminolevulinic acid, porphyrins, chlorins, bacteriochlorins, texaphyrins, phthalocyanines and porphycenes. It has been shown that there are many important considerations when designing a potential PDT/PACT agent, including the influence of added groups on the lipophilicity of the molecule, the positioning and nature of these added groups within the molecule, the presence of a central metal ion and the number of charges that the molecule possesses. The extensive ongoing research within the field has led to the identification of a number of potential lead molecules for application in PDT/PACT. The development of the second-generation photosensitizers, possessing shorter periods of photosensitization, longer activation wavelengths and greater selectivity for diseased tissue provides hope for attaining the ideal photosensitizer that may help PDT and PACT move from laboratory investigation to clinical practice.

Photodynamic therapy with ATX-S10.Na(II) inhibits synovial sarcoma cell growth

Photodynamic therapy (PDT) is an effective cancer treatment modality that allows selective destruction of malignant tumor cells. We asked whether PDT could inhibit in vivo and in vitro growth of synovial sarcoma cells. We analyzed PDT using ATX-S10.Na(II) and a diode laser for a synovial sarcoma cell line (SYO-1). Photodynamic therapy with ATX-S10.Na(II) showed an in vitro cytotoxic effect on the cultured SYO-1 cells. The in vitro effect of PDT depended on the treatment concentration of ATX-S10.Na(II) and the laser dose of irradiation. ATX-S10.Na(II) was detected in the tumor tissue specimens that were excised from nude mice bearing SYO-1 within 6 hours after intravenous injection, but it was eliminated from the tumor 12 hours after injection. Photodynamic therapy suppressed the tumor growth of nude mice bearing SYO-1, and high-dose irradiation induced no viable tumor cells in histologic specimens. Photodynamic therapy performed after marginal resection of the tumor of nude mice bearing SYO-1 reduced the rate of local recurrence of the tumor. Our results suggest PDT using ATX-S10.Na(II) and laser irradiation may be a potentially useful treatment for synovial sarcoma, especially to reduce the surgical margin and preserve critical anatomic structures adjacent to the tumor.

Sensitizer-mediated photooxidation of histidine residues: evidence for the formation of reactive side-chain peroxides

Exposure of proteins to visible light in the presence of a sensitizer results in the oxidation of Met, Trp, Tyr, Cys, and His side chains. These reactions are only partially understood, particularly with His. In this study, the oxidation of free His, His derivatives, and His-containing peptides has been examined using visible light and a range of sensitizers. It is shown that photooxidation gives rise to unstable peroxides, in a light-, illumination time-, and sensitizer-dependent manner. The yield of these materials is increased when reactions are carried out in solutions prepared with D2O, which prolongs the lifetime of 1O2, and decreased in the presence of the potent 1O2 scavenger azide, consistent with the involvement of this excited state. These peroxides have half-lives of hours, though the rate of decomposition is enhanced by elevated temperatures, reductants, and metal ions. Reducing metal ions catalyze the formation of radicals, which have been detected by EPR spin trapping. Structural analysis of His photo-products using NMR spectroscopy has provided evidence for the formation of oxygenated and cyclized compounds (e.g., 6a-hydroxy-2-oxo-octahydro-pyrollo[2,3-d]imidazole-5-carboxylic acid) and cross-linked materials. The latter materials may be partly responsible for the high yield of aggregated materials detected on photooxidation of His-containing proteins.

Inhibition of in-stent restenosis in rabbit iliac arteries with photodynamic therapy

OBJECTIVES

Photodynamic therapy (PDT, the combination of light with a photosensitising drug in the presence of oxygen) inhibits restenosis after angioplasty without stenting. This study assesses the potential of PDT for prevention of in-stent re-stenosis.

DESIGN AND METHODS

Normal rabbits were given the photosensitising agent 5-aminolaevulinic acid (ALA) 60 mg/kg, 3 h prior to endovascular illumination of the iliac artery (635 nm at 50 J/cm(2)) either immediately before or after deployment of an oversized (3 mm diameter) stent. PDT treated arteries were retrieved 3 or 28 days later and assessed for cell counts and vascular morphometry. Control arteries (stent but no PDT) were examined at 28 days.

RESULTS

There were no adverse events and all vessels were patent at the end of the study. At 3 days there was almost complete medial cell ablation when light was delivered before stent deployment (17+/-1 cells/hpf), with little effect when illumination followed stent deployment (184+/-17 cells/hpf, p<0.0001). Twenty-eight days after PDT, the neointimal areas were 1.41+/-0.52 mm(2) (stent with no PDT), 1.24+/-0.54 mm(2) (light after stent) and 0.60+/-0.21 mm(2) (light before stent) (p=0.004).

CONCLUSIONS

PDT before stent deployment caused almost complete medial cell ablation at 3 days with inhibition of in-stent restenosis at 28 days. PDT is worthy of further study as an adjuvant to percutaneous intervention in patients with vascular disease.

Necrosis Avid Contrast Agents

Two categories of necrosis-avid contrast agents (NACAs), namely porphyrin- and nonporphyrin-based complexes, have thus far been discovered as necrosis-targeting markers for noninvasive magnetic resonance imaging (MRI) identification of acute myocardial infarction, assessment of tissue or organ viability, and therapeutic evaluation after interventional therapies. In addition to necrosis labeling, other less-specific functions, such as first-pass perfusion, blood pool contrast effect, hepatobiliary contrast enhancement (CE), adrenal and spleen CE, and renal functional imaging, also are demonstrated with NACAs. Despite various investigations with a collection of clues in favor of certain hypotheses, the mechanisms of such a unique targetability for NACAs still remain to be elucidated. However, a few things have become clear that porphyrin-like structures are not necessary for necrosis avidity and the albumin binding is not the supposed driving force but only a parallel nonspecific feature shared by both NACAs and non-NACA substances. Although the research and development of NACAs still remain in preclinical stage at a relatively small scale, their significance rests upon striking enhancement effects, which may warrant their eventual versatile clinical applications. The present review article is intended to summarize the cumulated facts about the evolving research on this topic, to demonstrate experimental observations for better understanding of the mechanisms, to trigger broader public interests and more intensive research activities, and to advocate, toward both academics and industries, further promotion of preclinical and clinical development of this unique and promising class of contrast agents.

A review of progress in clinical photodynamic therapy

Photodynamic therapy (PDT) has received increased attention since the regulatory approvals have been granted to several photosensitizing drugs and light applicators worldwide. Much progress has been seen in basic sciences and clinical photodynamics in recent years. This review will focus on new developments of clinical investigation and discuss the usefulness of various forms of PDT techniques for curative or palliative treatment of malignant and non-malignant diseases.

Effects of photodynamic therapy on tumor stroma

Photodynamic therapy (PDT) is a treatment that combines a photosensitizer with light to generate oxygen-dependent photochemical destruction of diseased tissue. This modality has been approved worldwide since 1993 for the treatment of several oncological and nononcological disorders. PDT continues to be interested in both preclinical and clinical research, with more than 500 publications each year during the past 5 years. This minireview focuses on the effects of PDT on tumor stroma. A tumor consists of two fundamental elements: parenchyma (neoplastic cells) and stroma. The stroma is composed of vasculature, cellular components, and intercellular matrix and is necessary for tumor growth. All the stromal components can be targeted by PDT. Although the exact mechanism of PDT is unknown, emerging evidence has indicated that effective PDT of tumor requires destruction of both parenchyma and stroma. Further, damage to subendothelial zone of vasculature, in addition to endothelium, also appears to be a crucial factor. The PDT-generated immune response as a way of vaccination for treatment and prevention of metastatic tumors remains to be exploited.

Free radical attenuation prevents thrombosis and enables photochemical inhibition of vein graft intimal hyperplasia

OBJECTIVE

Photodynamic therapy (PDT) inhibits post-interventional stenosis in balloon-injured arteries, but causes thrombosis when applied to vein grafts. This may result from added free radicals produced during the hypoxia-reperfusion injury of vein graft implantation. The purposes of this study were to determine whether a free radical scavenger could inhibit vein graft thrombosis, enabling PDT to inhibit intimal hyperplasia; and to investigate the role of neutrophils, also a source of radicals, in this setting.

METHODS

Jugular vein bypass grafts of the common carotid artery were performed in rats. PDT was administered in situ to the vein graft and artery in the presence or absence of deferoxamine (DFX), an OH- scavenger.

RESULTS

PDT alone induced thrombosis in all untreated vein grafts. DFX administration or inhibition of neutrophil adhesion to the graft prevented PDT-induced vein graft thrombosis. Moreover, DFX given together with PDT significantly decreased vein graft intimal hyperplasia (0.010 mm2 +/- 0.005 mm2; P<.002) as compared with DFX alone (0.113 mm2 +/- 0.009 mm2) or untreated control animals (0.112 +/- 0.007 mm2).

CONCLUSIONS

OH- radicals and neutrophils both have key roles in PDT-induced vein graft thrombosis. By inhibiting free radical production or neutrophil adhesion to the graft, adequate PDT can be administered for successful inhibition of vein graft intimal hyperplasia.

Effects of texaphyrins on the oxygenation of EMT6 mouse mammary tumors

PURPOSE

To investigate the effects of texaphyrins on the oxygenation of EMT6 mouse mammary tumors in Balb/c Rw mice. Texaphyrins are synthetic, porphyrin-like molecules capable of stably coordinating lanthanide and nonlanthanide metals. Metallotexaphyrin compounds containing gadolinium (MGd), lutetium (MLu), europium (Eu-Tex), dysprosium (Dy-Tex), and manganese (Mn-Tex) were evaluated.

METHODS

Tumor oxygenation was measured using an Eppendorf pO2 histograph when tumors, implanted intradermally in the rear dorsum, reached 150-200 mm3. Oxygen measurements were also made in the leg muscle of tumor-bearing mice, to determine whether changes in oxygenation occurred in nontumor tissue.

RESULTS

Motexafin gadolinium (Xcytrin, MGd) seems to be an effective modulator of tumor oxygen tension. The mean of the median tumor pO2 6 hours after injection of MGd was 8.0 +/- 2.4 mm Hg. The control value was 1.5 +/- 0.4 mm Hg. The oxygen levels within EMT6 tumors were shifted significantly toward higher oxygen tensions 6-8 hours after i.v. injection of 40 micromol/kg MGd, thereby reducing the percentage of severely hypoxic readings (MGd, 6 hours: 44.6 +/- 4.3% <2.5 mm Hg;

CONTROL

69.4 +/- 3.0% <2.5 mm Hg). There was no significant change in the oxygenation of the leg muscle after MGd treatment. Eu-Tex and Mn-Tex increased the tumor oxygenation to a much lesser degree than MGd. MLu, Dy-Tex, and the vehicle (a 5% mannitol solution) did not modulate tumor oxygenation.

CONCLUSIONS

MGd is an effective modulator of tumor oxygenation. The central metal composition of texaphyrin compounds is an important determinant of the effect of the texaphyrins on tumor oxygenation.

Biodistribution Assessment of a Lutetium(III) Texaphyrin Analogue in Tumor-bearing Mice Using NIR Fourier-transform Raman Spectroscopy¶

The use of near-infrared (NIR)-excited Fourier-transform (FT) Raman spectroscopy as a technique for evaluating the extent of photosensitizer localization in tumor (human pancreatic adenocarcinomas)-bearing mice has been tested using lutetium(III) texaphyrin analogue Lu-T2B2Tex. The complex was injected subcutaneously in the form of three injections given during the course of 3 days. The kinetics of biodistribution were then followed over a time scale of 1-6 days. The NIR-FT-Raman spectra of tissue samples obtained from the xenographic tumor, muscle, heart, brain, liver, spleen, kidney and blood were recorded and used to identify the presence of Lu-T2B2Tex in these tissues. Five Raman sensitizer markers were used to estimate the relative content of Lu-T2B2Tex in tumor at various postinjection times. UV-Visible (Vis) absorption spectroscopic detection of this sensitizer in tissue extracts was applied as a conventional method. Both spectroscopic methods were in good agreement with each other and confirm that Lu-T2B2Tex localizes well in tumor tissue. Maximal drug content was observed 3 days after the final injection. This time delay seems to be optimal for tumor irradiation in photodynamic therapy.

Phase I drug and light dose-escalation trial of motexafin lutetium and far red light activation (phototherapy) in subjects with coronary artery disease undergoing percutaneous coronary intervention and stent deployment: procedural and long-term results

BACKGROUND

Motexafin lutetium (MLu; Antrin) is a photosensitizer that is taken up by atherosclerotic plaque and concentrated within macrophages and vascular smooth muscle cells. After photoactivation with far red light, MLu facilitates production of cytotoxic oxygen radicals that mediate apoptosis. We assessed the safety and tolerability of phototherapy (PT) with MLu in patients undergoing percutaneous coronary intervention with stent deployment.

METHODS AND RESULTS

An open-label, phase I, drug and light dose-escalation clinical trial of MLu PT enrolled 80 patients undergoing de novo coronary stent deployment. MLu was administered to 79 patients by intravenous infusion 18 to 24 hours before procedure, and photoactivation was performed after balloon predilatation and before stent deployment. Clinical evaluation, serial quantitative angiography, and intravascular ultrasound were performed periprocedurally and at 6 months follow-up. MLu PT was well tolerated without serious dose-limiting toxicities, and side effects (paresthesia and rash) were minor. No adverse angiographic outcomes were attributed to phototherapy.

CONCLUSIONS

This study demonstrates that coronary MLu PT seems safe, and the maximum well-tolerated MLu dose and range of tolerated light doses were identified. These data can be used in phase II efficacy trials of MLu PT for the treatment of coronary atherosclerosis or vulnerable plaque.

Tissue-specific MR contrast agents

The purpose of this review is to outline recent trends in contrast agent development for magnetic resonance imaging. Up to now, small molecular weight gadolinium chelates are the workhorse in contrast enhanced MRI. These first generation MR contrast agents distribute into the intravascular and interstitial space, thus allowing the evaluation of physiological parameters, such as the status or existence of the blood-brain-barrier or the renal function. Shortly after the first clinical use of paramagnetic metallochelates in 1983, compounds were suggested for liver imaging and enhancing a cardiac infarct. Meanwhile, liver specific contrast agents based on gadolinium, manganese or iron become reality. Dedicated blood pool agents will be available within the next years. These gadolinium or iron agents will be beneficial for longer lasting MRA procedures, such as cardiac imaging. Contrast enhanced lymphography after interstitial or intravenous injection will be another major step forward in diagnostic imaging. Metastatic involvement will be seen either after the injection of ultrasmall superparamagnetic iron oxides or dedicated gadolinium chelates. The accumulation of both compound classes is triggered by an uptake into macrophages. It is likely that similar agents will augment MRI of atheriosclerotic plaques, a systemic inflammatory disease of the arterial wall. Thrombus-specific agents based on small gadolinium labeled peptides are on the horizon. It is very obvious that the future of cardiovascular MRI will benefit from the development of new paramagnetic and superparamagnetic substances. The expectations for new tumor-, pathology- or receptor-specific agents are high. However, is not likely that such a compound will be available for daily routine MRI within the next decade.

In vitro interaction of macrocyclic photosensitizers with intact mitochondria: a spectroscopic study

Six water-soluble macrocyclic photosensitizers, the members of two groups of expanded porphyrins (metallotexaphyrins and free-base sapphyrins) containing hydrophilic substituents and meso-tetra(4-sulfonatophenyl)-porphyrin, were tested by UV-Vis absorption and resonance Raman spectroscopy in the in vitro binding experiments with intact mitochondria isolated from swine liver. Studied macrocycles showed markedly different affinity to mitochondria. The highest uptake was observed for sapphyrin-sugar conjugate and metallotexaphyrins. Sapphyrin-polyamine conjugates exhibit something less affinity to mitochondria, while the porphyrin of anionic character showed very low mitochondrial uptake. Obtained spectroscopic results confirm that the binding process altered the self-aggregation degree of expanded porphyrins.

Dynamic enhancement features of gadophrin-2 on magnetic resonance imaging: an experimental model of VX2 carcinoma and bacterial abscess in rabbit thigh

RATIONALE AND OBJECTIVES

To determine the dynamic enhancement features of malignant tumor and bacterial abscess in rabbits on magnetic resonance imaging (MRI) after injection of gadolinium mesoporphyrin (gadophrin-2) and to correlate them with histopathologic findings.

METHODS

Six VX2 carcinomas and six bacterial abscesses were experimentally induced in either thigh of six rabbits. Dynamic T1-weighted MRI was performed before and 1, 3, 5, 10, 30 minutes and 16, 21, 72 hours after intravenous injection of gadophrin-2 (0.05 mmol/kg). The enhancement ratios of lesions were calculated for each time point. All tumors and abscesses were sectioned along the same plane of MR images for a detailed MRI-histopathologic correlation.

RESULTS

In tumors and abscesses, peripheral-rim enhancement appeared on MRI at 1, 3, 5, 10, 30 minutes after injection of gadophrin-2. The lesions showed peripheral enhancement with irregular central enhancement or diffuse enhancement after 16 and 21 hours, and there was diffuse enhancement of the entire lesion after 72 hours. Enhancement ratios in tumor-necrosis mixed area and the pure necrotic area in VX2 carcinoma and the central cavity in bacterial abscess were significantly lower than that in the compact cellular portion in VX2 carcinoma and the wall of abscess at early phase (P < 0.01). On delayed phase MRI, there was no statistical significance in enhancement ratio of three histologic parts of VX2 carcinoma (P > 0.05) and two histologic parts of abscess (P > 0.05). Rapid enhancement at early phase with diminishing signal intensity at delayed phase is indicative of viable compact tumor and delayed strong enhancement is indicative of necrosis.

CONCLUSION

It is difficult to distinguish an abscess from a tumor on gadophrin-2 enhanced MRI especially when intratumoral necrosis is prominent. However, the trend and degree of enhancement by gadophrin-2 could be helpful in discrimination between viable tumor and tumor necrosis.

Photodynamic therapy: applications in atherosclerotic vascular disease with motexafin lutetium

Photodynamic therapy (PDT) has been approved as a tissue-specific light-activated cytotoxic therapy for many diseases. The ability of PDT to destroy target tissues selectively is especially appealing for atherosclerotic plaque. Biotechnology has developed a new generation of selective photosensitizers and catheter-based technological advances in light delivery have allowed the introduction of PDT into the vasculature. The largest experience to date is with motexafin lutetium (MLu, Antrin), an expanded porphyrin (texaphyrin) that accumulates in plaque. The combination of the motexafin lutetium and endovascular illumination, or Antrin phototherapy, has been shown to reduce plaque in animal models. Antrin phototherapy generates cytotoxic singlet oxygen that has been shown to induce apoptosis in macrophages and smooth muscle cells. The safety, tolerability, and preliminary efficacy of Antrin phototherapy has been assessed in a phase 1 dose-ranging clinical trial in subjects with peripheral artery disease and is currently being examined in a phase 1 study in subjects with lesions of the native coronary arteries undergoing stent implantation. The preliminary results suggest that Antrin phototherapy is safe, well tolerated, and nontraumatic.

Photodynamic therapy with motexafin lutetium (Lu-Tex) reduces experimental graft coronary artery disease

BACKGROUND

Motexafin lutetium (Lu-Tex) is a photodynamic therapy (PDT) agent that localizes in atheromatous plaque in which it can be activated by far-red light. Lu-Tex biolocalization was examined in graft coronary artery disease (GCAD) with a rodent allograft model. After photoactivation, the effect on intimal proliferation was assessed.

METHODS

A PVG to ACI rat heterotopic heart transplantation model was used. Lu-Tex (10 mg/kg) was intravenously administered 90 days after transplantation. Photoactivation was performed 24 hr after Lu-Tex administration. A light-emitting diode, central wavelength of 742 nm, was used to illuminate the intraperitoneally placed allografts via a laparotomy (light fluence of 75 J/cm2 at a power density of 75 mW/cm2). Animals were divided into four groups according to postoperative treatments: PDT with Lu-Tex injection and light illumination (n=21), Lu-Tex injection and laparotomy (n=14), laparotomy with light only (n=14), and laparotomy only (n=16). GCAD was quantitatively assessed 14 days after treatments.

RESULTS

Lu-Tex localized in atherosclerotic plaque in vessels with GCAD. PDT significantly reduced both the percent of affected vessels and intimal proliferation compared to all other control study groups. alpha-Smooth muscle cell actin and anti-rat macrophage antibody-positive areas were significantly reduced within the neointima in allografts treated with PDT compared to all other study groups.

CONCLUSIONS

PDT significantly reduced atherosclerotic lesions of GCAD. Lu-Tex-mediated PDT may, therefore, be a potential method for treating accelerated atherosclerosis associated with transplantation.

Photodynamic Therapy With Motexafin Lutetium Induces Redox-Sensitive Apoptosis of Vascular Cells

Abstract —Motexafin lutetium is a photosensitizer that accumulates in atherosclerotic plaque and, after activation by far-red light, produces cytotoxic singlet oxygen. The combination of photosensitizer and illumination, known as photodynamic therapy (PDT), has been shown to reduce atheroma formation in animal models and is under clinical investigation. However, the effects of PDT with motexafin lutetium on isolated vascular cells are unknown. This study was designed to characterize the effects of PDT on vascular cell viability and to define the cell-death pathway for this agent. Fluorescence microscopy of RAW macrophages and human vascular smooth muscle cells revealed time-dependent uptake of motexafin lutetium. Illumination of motexafin lutetium–loaded cells with 732-nm light (2 J/cm 2 ) impaired cellular viability and growth (IC 50 5 to 20 μmol/L). Depletion of intracellular glutathione potentiated ( P =0.035) and the addition of antioxidant N -acetylcysteine attenuated ( P =0.002) cell death, suggesting that the intracellular redox state influences motexafin lutetium action. PDT was associated with the loss of mitochondrial membrane potential, mitochondrial release of cytochrome c , and caspase activation. PDT promoted phosphatidylserine externalization and induced apoptotic DNA fragmentation, with the number of apoptotic cells increasing from 7±2% to 34±3% of total cells. Reducing plaque cellularity by the induction of apoptosis may be one mechanism by which PDT reduces plaque burden, possibly modulates plaque vulnerability, and inhibits restenosis in vivo.

Photodynamic therapy using motexafin lutetium in allograft coronary artery disease

Graft coronary artery disease (GCAD) limits long-term patient survival following heart transplantation. There are few treatment options. Exploration into less invasive diagnostic techniques and attenuation of allograft coronary disease is warranted. The selectivity of Antrin®Injection (a motexafin lutetium sensitizer, Lu-Tex) and illumination with far-red light, approximately 732 nm, has been evaluated in several preclinical atherosclerosis models. Lu-Tex, using fluorescence microscopy, was found to partition into distinct punctate cytoplasmic compartments in cultured human bypass coronary smooth muscle cells (SMCs). Using specific organelle probes the chief subcellular localization sites were lysosomes and endoplasmic reticulum. The inhibitory effect of Lu-Tex-mediated photoactivation was demonstrated using SMCs; many cells died via an apoptotic pathway. Following illumination, fluorescence microscopy revealed sensitizer redistribution with fluorescence being observed in the mitochondria. The distribution of Lu-Tex was evaluated in a rat model of heterotopic cardiac allografts 60 days after transplantation. Lu-Tex was retained in the cardiac allograft, exhibiting a five-fold increase in retention between the allograft and native heart. These results encourage further exploration of Lu-Tex for diagnosis, and possible amelioration of chronic graft vascular disease using photodynamic therapy.

Sensitive high-performance liquid chromatographic assay for motexafin gadolinium and motexafin lutetium in human plasma

We present new HPLC methods for the quantitation in human plasma of two investigative metallotexaphyrin agents, motexafin gadolinium (Gd-Tex) and motexafin lutetium (Lu-Tex). Each assay uses: the other texaphyrin analogue as an internal standard; protein precipitation with acetonitrile:methanol (50:50, v/v); an ODS reversed-phase column; an isocratic mobile phase of 100 mM ammonium acetate, pH 4.3:acetonitrile:methanol (59:21:20, v/v/v); and absorbance detection at 470 nm. The Gd-Tex assay has a lower limit of quantitation (LLOQ) of 0.01 microM and is linear between 0.01 and 30 microM. The Lu-Tex assay has an LLOQ of 0.1 microM and is linear between 0.1 and 30 microM. The assays are suited for in vivo preclinical studies and clinical trials because they require minimal amounts of plasma, are sensitive, and involve a 30-mm run time. These assays are important tools for evaluating the potential of Gd-Tex and Lu-Tex as a radiation enhancer and photosensitizer, respectively.

Photoangioplasty for human peripheral atherosclerosis: results of a phase I trial of photodynamic therapy with motexafin lutetium (Antrin)

BACKGROUND

In photoangioplasty, light activation of a photosensitive drug offers the potential for treatment of long segments of vascular disease. This is a brief description of a study designed to evaluate the safety and tolerability of a new photosensitizer, Antrin (motexafin lutetium), in the endovascular treatment of atherosclerosis.

METHODS AND RESULTS

An open-label, single-dose, escalating drug- and light-dose study was performed in patients with atherosclerotic peripheral arterial insufficiency. Clinical evaluation, serial quantitative angiography, and intravascular ultrasonography were performed. Therapy was well tolerated, and only minor side effects were observed. Treatment produced no deleterious vascular effects. Although this study was not designed to examine clinical efficacy, several secondary end points suggested a favorable therapeutic effect.

CONCLUSIONS

This phase I study demonstrates that photoangioplasty with motexafin lutetium is well tolerated and safe. Preliminary efficacy data suggest a future role for the treatment of flow-limiting atherosclerosis.