Efficacy and safety of second photodynamic therapy for local failure after salvage photodynamic therapy for esophageal cancer.

OBJECTIVES: Photodynamic therapy (PDT) is an optional salvage treatment for local failure of esophageal squamous cell carcinoma (ESCC) after chemoradiotherapy; however, local failure after PDT sometimes occurs. In such cases, second PDT is sometimes attempted, but its outcomes remain unclear. This study aimed to evaluate the efficacy and safety of second PDT. METHODS: We enrolled patients who underwent PDT for local failure of ESCC after chemoradiotherapy. We retrospectively evaluated local-complete response (L-CR) rate and clinical outcomes of first and second PDT. The indications for PDT were lesions within the muscle layer, <3 cm in size, and <3/4 of the esophageal circumference; not suitable for salvage surgery; and absence of metastasis. Second PDT was avoided when lesions were apparently refractory to first PDT, e.g. persistence of submucosal tumor-like protruded component or rapid regrowth of tumor at the ulceration after first PDT. L-CR was defined as endoscopic disappearance of tumor and post-PDT ulcer and absence of cancer cells histologically. RESULTS: Among 82 patients who underwent first PDT, 27 underwent second PDT. The L-CR rates with first and second PDT were 63.0% and 40.7%, respectively. The 2-year overall survival rates after second PDT in patients with L-CR and local-nonCR were 79.5% and 40.5%, respectively. Five of 11 patients with L-CR survived without any recurrence. No grade ≥3 adverse events occurred. CONCLUSIONS: Second PDT demonstrated excellent safety and acceptable efficacy; therefore, it could be a useful treatment for local failure after first PDT.

Spatiotemporal metabolic dynamics of the photosensitizer talaporfin sodium in carcinoma and sarcoma.

Photodynamic therapy (PDT) using the photosensitizer talaporfin sodium (talaporfin) is a new mode of treatment for cancer. However, the metabolic mechanism of talaporfin has not been clarified. Thus, we investigated the uptake, transportation, and elimination mechanisms of talaporfin in carcinoma and sarcoma. The results showed that talaporfin co-localized in early endosomes and lysosomes. Talaporfin uptake was via clathrin- and caveolae-dependent endocytosis and a high amount of intracellular ATP was essential. Inhibition of lysosomal enzymes maintained intracellular talaporfin levels. Inhibition of K-Ras signaling reduced talaporfin uptake in carcinoma and sarcoma cell lines. Talaporfin was taken up by clathrin- and caveolae-dependent endocytosis, translocated from early endosomes to lysosomes, and finally degraded by lysosomes. We also demonstrated that ATP is essential for the uptake of talaporfin and that activation of K-Ras is involved as a regulatory mechanism. These results provide new insights into the metabolism of talaporfin in cancer cells for the enhancement of PDT for carcinoma and sarcoma.

Efficient photodynamic therapy against drug-resistant prostate cancer using replication-deficient virus particles and talaporfin sodium.

To enhance the potency of photosensitizer, we developed a novel photosensitizer, Laserphyrin®-HVJ-E (L-HVJ-E), by incorporating talaporfin sodium (Laserphyrin®, Meiji Seika Pharma) into hemagglutinating virus of Japan envelope (HVJ-E). In this study, we examined the optimal Laserphyrin® concentration for preparation of Laserphyrin®-HVJ-E which had photocytotoxicity and maintained direct cytotoxicity derived from HVJ-E. Then, potency of Laserphyrin®-HVJ-E and Laserphyrin® were compared in vitro using castration-resistant prostate cancer cell line (PC-3). A laser diode (L660P120, Thorlabs, USA) with a wavelength of 664 nm was used for light activation of Laserphyrin®, which corresponds to an absorption peak of Laserphyrin® and provides a high therapeutic efficiency. The photocytotoxicity and direct cytotoxicity of Laserphyrin®-HVJ-E prepared using various Laserphyrin® concentrations were evaluated using PC-3 cell in vitro. We categorized the treatment groups as Group 1: 50 µL of D-MEM treatment group, Group 2: HVJ-E treatment group, Group 3: Laserphyrin®-HVJ-E treatment group, and Group 4: Laserphyrin® treatment group. Group 3 was subjected to different concentrations of Laserphyrin®-HVJ-E suspension, and all groups were subjected to different incubation periods (24, 48 h), (30 min, 1 h, or 3 h,) respectively, without and after PDT. Laserphyrin®-HVJ-E prepared using 15 mM Laserphyrin® had high photocytotoxicity and maintained HVJ-E's ability to induce direct cytotoxicity. Therapeutic effect of Laserphyrin®-HVJ-E was substantially equivalent to that of Laserphyrin® alone even at half Laserphyrin® concentration. By utilizing Laserphyrin®-HVJ-E, PDT could be performed with lower Laserphyrin® concentration. In addition, Laserphyrin®-HVJ-E showed higher potency than Laserphyrin® by combining cytotoxicities of HVJ-E and PDT.

Evaluation of the efficacy and safety of salvage photodynamic therapy by talaporfin sodium for cervical esophageal cancers and lesions larger than 3 cm.

BACKGROUND: Salvage photodynamic therapy with talaporfin sodium has a high local control rate for esophageal cancer after definitive chemoradiotherapy. The eligibility criteria for photodynamic therapy include the absence of invasion to the cervical esophagus and a 3 cm maximum longitudinal lesion length. There is little evidence regarding the efficacy and safety of lesions outside the eligibility criteria. This retrospective cohort study evaluated the efficacy and safety of photodynamic therapy of such lesions. METHODS: Patients with consecutive lesions between February 2016 and May 2020 (n = 36) were enrolled. The local complete response rates and adverse events were compared between patients with cervical and non-cervical lesions and those with lesions larger and smaller than 3 cm. RESULTS: The local complete response rate was 77.8% and was significantly lower in cervical than in non-cervical lesions (20.0% vs 80.6%, p = 0.005). Esophageal stricture, laryngeal pain, and fever were significantly higher in the cervical than in the non-cervical lesion group; however, the detected adverse events were up to grade 2. Laser exposure dose was high in lesions larger than 3 cm (median, 650 vs 400 J; p < 0.001). No significant differences in local complete response rates and adverse effects were noted. One case involving a lesion larger than 3 cm needed balloon dilations for esophageal stricture. CONCLUSIONS: Although salvage esophageal photodynamic therapy was effective for local control with acceptable safety after definitive chemoradiotherapy failure, photodynamic therapy toward cervical lesions had a statistically lower local complete response rate. Lesions larger than 3 cm may be considered treatable.

Advantages of salvage photodynamic therapy using talaporfin sodium for local failure after chemoradiotherapy or radiotherapy for esophageal cancer.

BACKGROUND: Photodynamic therapy (PDT) is a salvage treatment for local failure following chemoradiotherapy (CRT) for esophageal cancer. This study aimed to evaluate the efficacy and safety of salvage PDT using the second-generation photosensitizer, talaporfin sodium (L-PDT), and compare L-PDT to PDT using porfimer sodium (P-PDT). METHODS: We retrospectively analyzed clinical outcomes of patients treated with L-PDT and P-PDT. Patients with histologically proven local failure limited to the shallow muscularis propria layer (T2) after CRT or radiotherapy (RT) for esophageal cancer were enrolled. RESULTS: A total of 121 patients were enrolled in this study. L-PDT and P-PDT groups consisted of 44 and 77 patients, respectively. The overall local complete response (L-CR) rate was 62.1% (95% confidence interval [CI], 52.6-70.9), and the L-PDT group showed a better L-CR rate than did the P-PDT group (69.0% [95% CI 52.9-82.4] vs. 58.1% [95% CI 46.1-69.5]). The common complications of skin phototoxicity, esophageal stricture, and esophageal fistula were all less frequent in the L-PDT group than in the P-PDT group. The only treatment-related death in this study was in the P-PDT group. With a median follow-up period of 15.8 months (interquartile range 7.1-37.4) in all 121 patients, overall survival rate at 1 year was significantly higher among patients who achieved L-CR (91.2% [95% CI 80.2-96.3]) than among those who could not achieve L-CR with PDT (50.8% [95% CI 33.6-65.6]). CONCLUSIONS: L-PDT represented better short-term outcomes than P-PDT as a salvage treatment for local failure following CRT or RT for esophageal cancer.

Excellent antitumor effects for gastrointestinal cancers using photodynamic therapy with a novel glucose conjugated chlorin e6.

BACKGROUND: Photodynamic therapy (PDT) exploits the reaction between photosensitizer and irradiated light to generate potentially therapeutic reactive oxygen species such as singlet oxygen in cancer cells. We have reported several sugar-conjugated chlorins that express stronger antitumor effects in PDT than talaporfin sodium (TS), a second-generation photosensitizer clinically used in Japan. In this study, we developed a novel glucose-conjugated chlorin e6 (G-chlorin e6) and evaluated its antitumor effects. METHODS: G-chlorin e6 was synthesized with a core photosensitizer chlorin e6 conjugated to glucose. We measured the half maximal inhibitory concentration (IC50) to compare the PDT effects of G-chlorin e6 and TS, and flow cytometry was performed to examine the accumulation of G-chlorin e6 in cancer cells. We also compared the accumulation of G-chlorin e6 between normal immortalized esophageal epithelial cells and esophageal cancer cells. Antitumor effects of G-chlorin e6 PDT were finally analyzed in allograft tumor mouse models. RESULTS: PDT in vitro using G-chlorin e6 elicited 9, 000-34,000 times stronger antitumor effects than TS, and there was 70-190 times more G-chlorin e6 accumulated than TS by flow cytometry. G-chlorin e6 accumulated more selectively in esophageal cancer cells than in esophageal immortalized epithelial cells, and in an allograft model, PDT with G-chlorin e6 showed very strong antitumor effects and a 40% complete response (CR) rate. CONCLUSIONS: G-chlorin e6 showed excellent tumor selectivity, and PDT using G-chlorin e6 revealed the strongest anti-tumor effects among all sugar-conjugated chlorins that we have studied. G-chlorin e6 is considered to be the best photosensitizer for next-generation PDT.

Effect of a photosensitization reaction performed during the first 3 min after exposure of rat myocardial cells to talaporfin sodium in vitro.

To better understand the mechanism of photodynamic cardiac ablation, we studied the effects of a photosensitization reaction (PR) performed during the first 3 min after rat myocardial cells were exposed to talaporfin sodium. A 3-mm-square microelectrode array with 64 electrodes was used to continuously measure the action potentials of the myocardial cells. A 30 µg/mL talaporfin sodium solution, a chlorine photosensitizer, was used, along with a 663-nm red diode laser (86 mW/cm2 for up to 600 s). The first trough of the measured action potential waveform corresponding to Na+ dynamics decreased exponentially with increasing PR duration. The average decay time of the exponential function from PR onset was 20.1 s. Marked morphological changes in the myocardial cells was observed after the PR. These results indicated that the behavior of the action potential waveform measured by the microelectrode array might be used as a less invasive method to evaluate the electrophysiological effects of a PR on myocardial cells.

Electrical superior vena cava isolation using photodynamic therapy in a canine model.

AIMS: With the new era of multi-tip radiofrequency or balloon ablation catheters replacing the point-to-point ablation strategy, we aimed to determine the feasibility of a ring-laser catheter ablation technology to electrically isolate the superior vena cava (SVC) by exploring the advantages of the limitless catheter tip size possibly with the photodynamic therapy (PDT)-mediated ablation. METHODS AND RESULTS: We developed a first-generation prototype of a circular-laser-mapping catheter by fitting a 7 cm plastic optical fibre onto a circular variable-loop Lasso™ mapping catheter. Following SVC venography, both the laser catheter and another ring catheter for monitoring the SVC potentials were placed at the SVC. After the systemic infusion of a photosensitizer (talaporfin sodium), we initiated the irradiation with an output of 1 W in three canines and 0.3 W in four. The creation of electrical isolation as well as occurrence of phrenic nerve injury, sinus node injury, and SVC stenosis were evaluated before, immediately after, and 1 month after the procedure. A PDT-mediated SVC isolation was successfully performed in all seven canines. The isolation was completed with a laser irradiation of 70.4 ± 71.4 J/cm under 30.9 ± 5.0 µg/mL of a photosensitizer without any sinus node injury, phrenic nerve palsy, or SVC stenosis in both the acute and chronic evaluations. The minimum isolation time of 270 s was not correlated with the laser input power or the photosensitizer concentration. CONCLUSION: The electrical SVC isolation was successfully and instantly achieved using the PDT laser-ring catheter without any complications.

Optimal conditions for cardiac catheter ablation using photodynamic therapy.

AIMS: Photodynamic therapy (PDT) is based on non-thermal injury mediated by singlet oxygen species and is used clinically in cancer therapy. In our continuing efforts to apply this technology to cardiac catheter ablation, we clarified the optimal condition for creating PDT-mediated lesions using a laser catheter. METHODS AND RESULTS: In a total of 35 canines, we applied a laser directly to the epicardium of the beating heart during open-chest surgery at 15 min after administration of a photosensitizer, talaporfin sodium. We evaluated the lesion size (depth and width) using hematoxylin-eosin staining under varying conditions as follows: laser output (5, 10, 20 W/cm(2)), irradiation time (0-60 s), photosensitizer concentration (0, 2.5, 5 mg/kg), blood oxygen concentration (103.5 ± 2.1 vs. 548.0 ± 18.4 torr), and contact force applied during irradiations (low: <20 g, high: >20 g). A laser irradiation at 20 W/cm(2) for 60 s under 5 mg/kg (29 µg/mL) of photosensitizer induced a lesion 8.7 ± 0.8 mm deep and 5.2 ± 0.2 mm wide. The lesion size was thus positively correlated to the laser power, irradiation time, and photosensitizer concentration, and was independent of the applied contact force and oxygen concentration. In addition, the concentration of the photosensitizer strongly correlated with the changes in the pulse oximetry data and fluorescence of the backscattering laser, suggesting that a clinically appropriate condition could be estimated in real time. CONCLUSION: Photodynamic therapy-mediated cardiac lesions might be controllable by regulating the photosensitizer concentration, laser output, and irradiation time.

Fluorescence characteristics and lifetime images of photosensitizers of talaporfin sodium and sodium pheophorbide a in normal and cancer cells.

Fluorescence spectra and fluorescence lifetime images of talaporfin sodium and sodium-pheophorbide a, which can be regarded as photosensitizers for photodynamic therapy, were measured in normal and cancer cells. The reduction of the fluorescence intensity by photoirradiation was observed for both photosensitizers in both cells, but the quenching rate was much faster in cancer cells than in normal cells. These results are explained in terms of the excessive generation of reactive oxygen species via photoexcitation of these photosensitizers in cancer cells. The fluorescence lifetimes of both photosensitizers in cancer cells are different from those in normal cells, which originates from the different intracellular environments around the photosensitizers between normal and cancer cells.

Clinical Impact of the Charlson Comorbidity Index on the Efficacy of Salvage Photodynamic Therapy Using Talaporfin Sodium for Esophageal Cancer.

Introduction Photodynamic therapy (PDT) is a salvage treatment for local failure after chemoradiotherapy for esophageal cancer. Salvage PDT is the treatment available for vulnerable patients with various comorbidities at risk of salvage esophagectomy. This study assessed the impact of the Charlson comorbidity index (CCI) on the outcomes of salvage PDT using talaporfin sodium (TS) for esophageal cancer. Metohds Consecutive patients with esophageal cancer who underwent salvage TS-PDT from 2016 to 2022 were included in this retrospective study. We investigated the local complete response (L-CR), progression-free survival (PFS) and overall survival (OS) and evaluated the relationship between the CCI and therapeutic efficacy. Results In total, 25 patients were enrolled in this study. Overall, 12 patients (48%) achieved an L-CR, and the 2-year PFS and OS rates were 24.9% and 59.4%, respectively. In a multivariate analysis, a CCI ≥1 (p=0.041) and deeper invasion (p=0.048) were found to be significant independent risk factors for not achieving an L-CR. To evaluate the efficacy associated with comorbidities, we divided the patients into the CCI=0 group (n=11) and the CCI ≥1 group (n=14). The rate of an L-CR (p=0.035) and the 2-year PFS (p=0.029) and OS (p=0.018) rates in the CCI ≥1 group were significantly lower than those in the CCI=0 group. Conclusion This study found that the CCI was negatively associated with the efficacy of salvage TS-PDT for esophageal cancer.

The Safety of Intraoperative Photodynamic Diagnosis Using 5-Aminolevulinic Acid Combined with Talaporfin Sodium Photodynamic Therapy in Recurrent High-Grade Glioma.

BACKGROUND: Intraoperative photodynamic diagnosis (PDD) using 5-aminolevulinic acid (5-ALA) is a widely adopted technique to enhance the extent of resection during high-grade glioma (HGG) surgery. Recent updates to the package insert for 5-ALA in Japan now allow its use in combination with drugs that may induce photosensitivity, such as talaporfin sodium (TS). TS is employed in intraoperative photodynamic therapy (PDT) and has been shown to improve overall survival. The combination of 5-ALA with TS is expected to offer further benefits. However, the safety of this combination had not been established. This study reports on the safety of 5-ALA-PDD with TS-PDT in the treatment of recurrent HGG. METHODS: 7 patients with recurrent HGG underwent tumor resection using a combination of 5-ALA-PDD and TS-PDT. The incidence of photosensitivity as an adverse effect associated with 5-ALA and TS was evaluated as described in the package insert. Adverse events were assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. RESULTS: Tumor-specific fluorescence intensity was strong in 4 cases and weak in 3. Photosensitivity occurred in only 1 patient (14.3%). Three patients exhibited CTCAE grade 1 or 2 abnormal liver function, and 1 patient experienced CTCAE grade 1 γ-GTP elevation. All abnormalities improved during follow-up. CONCLUSIONS: The combined use of 5-ALA-PDD and TS-PDT for HGG surgery did not increase the risk of serious adverse events in our study. Further investigations with a larger number of cases are needed for a more accurate assessment of its safety and efficacy.

Induction of ferroptosis by photodynamic therapy and enhancement of antitumor effect with ferroptosis inducers.

BACKGROUND: Photodynamic therapy (PDT) is an effective tumor treatment that involves the administration of a photosensitizer to generate cytotoxic 1O2 [reactive oxygen species (ROS)] from molecular oxygen that is produced from energy absorption following tumor irradiation at specific wavelengths. Ferroptosis is induced by the disruption of the glutathione peroxidase 4 (GPX4) antioxidant system, leading to lipid peroxidation. We hypothesized that talaporfin sodium-photodynamic therapy (TS-PDT)-generated ROS would lead to ferroptosis via accumulation of lipid peroxidation. METHODS: Cell viability assay in TS-PDT-treated cells in combination with a ferroptosis inhibitor (ferrostatin-1: Fer-1) or ferroptosis inducers (imidazole ketone erastin: IKE, Ras-selective lethal 3: RSL3) was performed. Accumulation of lipid peroxidation, GPX4 antioxidant system and cystine/glutamate antiporter (system xc-) activity in TS-PDT-treated cells was investigated. In xenograft mice, the antitumor effect of TS-PDT in combination with ferroptosis inducers (IKE or sorafenib) was examined. RESULTS: TS-PDT-induced cell death was partly suppressed by Fer-1 and accompanied by lipid peroxidation. TS-PDT combined with IKE or RSL3 enhanced the induction of cell death. TS-PDT inhibited cystine uptake activity via system xc-. In vivo, the combination of TS-PDT and ferroptosis inducers (IKE or sorafenib) reduced tumor volume. CONCLUSION: This study found that the mechanism underlying TS-PDT-induced ferroptosis constitutes direct lipid peroxidation by the generated ROS, and the inhibition of system xc-, and that the combination of a ferroptosis inducer with TS-PDT enhances the antitumor effect of TS-PDT. Our findings suggest that ferroptosis-inducing therapies combined with PDT may benefit cancer patients.

Efficacy of interstitial photodynamic therapy using talaporfin sodium and a semiconductor laser for a mouse allograft glioma model.

To investigate the therapeutic potential of photodynamic therapy (PDT) for malignant gliomas arising in unresectable sites, we investigated the effect of tumor tissue damage by interstitial PDT (i-PDT) using talaporfin sodium (TPS) in a mouse glioma model in which C6 glioma cells were implanted subcutaneously. A kinetic study of TPS demonstrated that a dose of 10 mg/kg and 90 min after administration was appropriate dose and timing for i-PDT. Performing i-PDT using a small-diameter plastic optical fiber demonstrated that an irradiation energy density of 100 J/cm2 or higher was required to achieve therapeutic effects over the entire tumor tissue. The tissue damage induced apoptosis in the area close to the light source, whereas vascular effects, such as fibrin thrombus formation occurred in the area slightly distant from the light source. Furthermore, when irradiating at the same energy density, irradiation at a lower power density for a longer period of time was more effective than irradiation at a higher power density for a shorter time. When performing i-PDT, it is important to consider the rate of delivery of the irradiation light into the tumor tissue and to set irradiation conditions that achieve an optimal balance between cytotoxic and vascular effects.

Long-term outcomes of PDT for centrally-located early lung cancers with tumor diameters > 2.0 cm.

BACKGROUND: Photodynamic therapy (PDT) is used for the treatment of centrally-located early lung cancers (CLELCs) and is recommended for tumors ≤ 1.0 cm in diameter. We previously reported that PDT using talaporfin sodium, second-generation photosensitizer, for tumors > 1.0 cm but ≤ 2.0 cm in diameter was able to achieve a therapeutic outcome comparable to that of tumors with a diameter of ≤ 1.0 cm. However, the effectiveness of PDT using talaporfin sodium for tumors > 2.0 cm in diameter remains unclear. We conducted a retrospective analysis of cases in which PDT was performed for flat-type CLELCs with tumor diameters of > 2.0 cm. METHODS: We retrospectively analyzed seven cases (eight lesions) with tumor diameters > 2.0 cm and no evidence of extracartilaginous invasion or lymph node metastasis. RESULTS: All the patients underwent multiple PDT sessions. The PDT treatment results over the study period were partial response in one case (14.3 %), stable disease (SD) in three cases (42.9 %), and progressive disease (PD) in three cases (42.9 %). At the time of writing this report, five of seven cases (71.4 %) are still undergoing treatment. The duration of SD-the time from the start of treatment until the criteria for PD were met (SD or better maintained)-ranged from 7 to 52 months (mean, 25.3 months). CONCLUSIONS: "Maintenance PDT" for CLELCs > 2.0 cm in diameter has the potential to inhibit tumor progression in the long term while maintaining quality of life, rather than simply aiming only for a quick radical cure.

Photodynamic therapy using talaporfin sodium for non-totally resectable malignant glioma.

BACKGROUND: For malignant glioma, intraoperative photodynamic therapy (PDT) using talaporfin sodium is a powerful tool for local tumor control, when gross total removal is performed. However, the efficacy of PDT for non-totally resectable malignant glioma has not been clearly confirmed. Therefore, the purpose of this study was to clarify the usefulness of PDT using talaporfin sodium for non-totally resectable malignant glioma. METHODS: Eighteen patients with malignant glioma (16 new onset, 2 recurrent) in whom gross total removal was judged to be difficult from the images obtained before surgery were evaluated. Fifteen patients had glioblastoma (14 newly diagnosed, 1 recurrent), and 3 patients had anaplastic oligodendroglioma (2 newly diagnosed, 1 recurrent). The whole resection cavity was subjected to PDT during the surgery. For newly diagnosed glioblastoma, postoperative therapy involved the combined use of radiation and temozolomide. Bevacizumab treatment was also started at an early stage after surgery. RESULTS: In some patients, reduction of the residual tumor was observed at an early stage of chemoradiotherapy after the surgery, suggesting the positive effect of PDT. Recurrence occurred in 15 of the 18 patients during the course of treatment. Distant recurrence occurred in 8 of these 15 patients, despite good local tumor control. In the 14 patients with newly diagnosed glioblastoma, the median progression-free survival was almost 10.5 months, and the median overall survival was almost 16.9 months. CONCLUSIONS: PDT for malignant glioma is expected to slightly improve local tumor control for non-totally resectable lesions.

Photodynamic therapy with talaporfin sodium for endoscopically unresectable gastric cancer using a novel simultaneous light-emitting method.

We describe a case of gastric cancer treated by photodynamic therapy (PDT) with talaporfin sodium using a novel simultaneous light-emitting method. An 82-year-old man was diagnosed with gastric cancer near the cardia with suspected deep submucosal invasion. Surgical resection was deemed high-risk owing to an underlying pulmonary disease. After ruling out endoscopic procedures due to intense fibrosis resulting from the scarring, PDT with talaporfin sodium was chosen. PDT was successfully conducted using an endoscope with simultaneous light emission. The patient experienced a complete response to the treatment and showed no signs of recurrence during follow-up. This case highlights the potential of PDT with talaporfin sodium as a viable alternative for challenging cases, particularly in patients unsuitable for surgery and endoscopic resection. Furthermore, the novel simultaneous light-emitting method may improve the efficiency of the procedure. This case demonstrates the potential of PDT in gastric cancer treatment, especially for high-risk patients.

Detailed in vitro study of the photosensitization reaction of extracellular Talaporfin sodium in rat myocardial cells.

BACKGROUND AND OBJECTIVE: We proposed a new non-thermal treatment for tachyarrhythmia that employs an extracellular photosensitization reaction. Oxygen depletion may easily occur in in vitro studies of this reaction because the photosensitizing agent is often highly concentrated in such studies. The aim of the current study was to examine the progress of the extracellular photosensitization reaction and the photocytotoxicity of extracellular Talaporfin sodium on myocardial cells for application in tachyarrhythmia therapy. MATERIALS AND METHODS: Photosensitization reactions were performed in single wells of 96-well plates; Talaporfin sodium solution concentrations from 5 to 40 µg/ml, radiant exposures up to 40 J/cm(2) , and irradiance of 0.29 W/cm(2) from a continuous wave (CW) red diode laser (wavelength: 663 nm) were used. We measured transient changes of temperature, photosensitizer fluorescence, dissolved oxygen pressure, and photosensitizer solution absorbance to monitor the progress of the photosensitization reaction in the system during laser irradiation. Rat myocardial cells were cultured in 96-well plates, and the drug-light interval was set to 15 minutes. We used a WST assay to measure cell lethality 2 hours after laser irradiation. RESULTS: A strong photosensitization reaction occurred several seconds after initiation of laser irradiation; this initial reaction depended upon dissolved oxygen. A gentler continuous photosensitization reaction followed the initial reaction, and was associated with temperature increases of less than 10°C. The oxygen pressure was kept in approximately 40 mmHg of the myocardial tissue oxygen pressure in the gentle photosensitization reaction phase. At radiant exposures from 10 to 40 J/cm(2) , a photosensitizer concentration of approximately 15 µg/ml was the threshold for myocardial cell necrosis in this in vitro system. The dependencies of photocytotoxicity on radiant exposure were separated into two distinct groups based on the molecular density ratio between Talaporfin sodium and albumin. CONCLUSIONS: This in vitro system for the extracellular photosensitization reaction may reflect the situation in live myocardial tissue. We found that the extracellular photosensitization reaction progressed in two distinctive phases; the first phase depended upon dissolved oxygen, and the second upon the molar density ratio between Talaporfin sodium and albumin. Cell lethality due to the extracellular photosensitization reaction was influenced by both of these factors in our in vitro system. We suggest that a photosensitizer concentration of 25 µg/ml might be necessary to treat myocardial tissue with therapies involving the extracellular photosensitization reaction.

A study of laser dose in photodynamic therapy with talaporfin sodium for malignant central airway stenosis.

Photodynamic therapy (PDT) has been shown to be effective and safe in the treatment of malignant central airway stenosis. However, the laser dose for talaporfin PDT is unclear. We herein review cases where talaporfin PDT was used to treat malignant central airway stenosis. A total of 17 lesions were treated with talaporfin PDT at laser doses of 50-150 J/cm2. Improvement of airway stenosis was observed in all cases except for 1 lesion treated with a dose of 50 J/cm2. The results show that talaporfin PDT with 100 J/cm2 of laser dose is a feasible treatment for malignant central airway stenosis. (This is a secondary publication from the Journal of Japan Society for Laser Surgery and Medicine 2022; 43(1): 9-12.).

First Clinical Report of the Intraoperative Macro- and Micro-Photodiagnosis and Photodynamic Therapy Using Talaporfin Sodium for a Patient with Disseminated Lumbar Medulloblastoma.

Photodiagnosis (PD) and photodynamic therapy (PDT) using the second-generation photosensitizer talaporfin sodium together with an exciting laser for primary intracranial malignant tumors is well recognized in Japan, and many medical institutions are introducing this new therapeutic option. In particular, intraoperative PDT using talaporfin sodium for infiltrating tumor cells in the cavity walls after the resection of malignant glioma is now covered by health insurance after receiving governmental approvement, and this method has been recommended in therapeutic guidelines for primary malignant brain tumors in Japan. On the other hand, experimental and clinical studies on the development of novel therapeutic strategies for malignant spinal cord tumors have not been reported to date, although their histological features are almost identical to those of intracranial malignant tumors. Therefore, the clinical outcomes of malignant spinal cord tumors have been less favorable than those of malignant brain tumors. In this report, we performed the PD and PDT using talaporfin sodium on a patient with a metastatic lumbar lesion that was detected on magnetic resonance image (MRI) 50 months after the resection of cerebellar medulloblastoma who presented with lumbago and sciatica. We were able to detect the target lesion in the conus medullaris using a surgical microscope, and detected the disseminated medulloblastoma cells floating in the cerebrospinal fluid using a compact fluorescence microscope. Furthermore, we performed PDT to the resected lumbar lesion with the adjuvant platinum-based chemotherapy, and the patient survived a meaningful life for more than 2 years after the lumbar surgery. This report describes the first case of a human patient in whom the efficacy of PD and PDT was demonstrated for a malignant spinal cord tumor.