Real-time IR700 Fluorescence Imaging During Near-infrared Photoimmunotherapy Using a Clinically-approved Camera for Indocyanine Green

Real-Time Fluorescence Monitoring System for Optimal Light Dosage in Cancer Photoimmunotherapy

Background/Objectives: Near-infrared photoimmunotherapy (NIR-PIT) was recently approved for the treatment of unresectable locally advanced or recurrent head and neck cancers in Japan; however, only one clinical dose has been validated in clinical trials, potentially resulting in excessive or insufficient dosing. Moreover, IRDye700X (IR700) fluorescence intensity plateaus during treatment, indicating a particular threshold for the antitumor effects. Therefore, we investigated the NIR laser dose across varying tumor sizes and irradiation methods until the antitumor effects of the fluorescence decay rate plateaued. Methods: Mice were subcutaneously transplanted with A431 xenografts and categorized into control, clinical dose (cylindrical irradiation at 100 J/cm², frontal irradiation at 50 J/cm²), and evaluation groups. The rate of tumor IR700 fluorescence intensity decay to reach predefined rates (-0.05%/s or -0.2%/s) until the cessation of light irradiation was calculated using a real-time fluorescence imaging system. Results: The evaluation group exhibited antitumor effects comparable to those of the clinical dose group at a low irradiation dose. Similar results were observed across tumor sizes and irradiation methods. Conclusions: In conclusion, the optimal antitumor effect of NIR-PIT is achieved when the fluorescence decay rate reaches a plateau, indicating the potential to determine the appropriate dose for PIT using a real-time fluorescence monitoring system.

The role of interventional radiology and molecular imaging for near infrared photoimmunotherapy

Near infrared photoimmunotherapy (NIR-PIT) is a recently approved cancer therapy for recurrent head and neck cancer. It involves the intravenous administration of an antibody-photoabsorber (IRDye700DX: IR700) conjugate (APC) to target cancer cells, followed 24 h later by exposure to near infrared light to activate cell-specific cytotoxicity. NIR-PIT selectively targets cancer cells for destruction and activates a strong anticancer host immunity. The fluorescent signal emitted by IR700 enables the visualization of the APC in vivo using fluorescence imaging. Similarly, the activation of IR700 during therapy can be monitored by loss of fluorescence. NIR-PIT can be used with a variety of antibodies and therefore, a variety of cancer types. However, in most cases, NIR-PIT requires direct light exposure only achieved with interstitial diffuser light fibers that are placed with image-guided interventional needle insertion. In addition, the unique nature of NIR-PIT cell death, means that metabolic molecular imaging techniques such as PET and diffusion MRI can be used to assess therapeutic outcomes. This mini-review focuses on the potential implications of NIR-PIT for interventional radiology and therapeutic monitoring.

The chemical basis of cytotoxicity of silicon-phthalocyanine-based near infrared photoimmunotherapy (NIR-PIT) and its implications for treatment monitoring

Near infrared photoimmunotherapy (NIR-PIT) is a new cancer therapy based on the photo-induced ligand release reaction of a silicon-phthalocyanine derivative, IRDye700DX (IR700), that causes rapid cell death. Following exposure to an antibody-IR700-conjugate, cells exposed to NIR light within minutes undergo rapid swelling, blebbing, and finally, bursting. The photo-induced ligand release reaction also induces immediate loss of IR700 fluorescence due to dimerization or aggregation of the antibody-IR700 conjugate allowing for real time monitoring of NIR-PIT therapy.

Trastuzumab-based near-infrared photoimmunotherapy in xenograft mouse of breast cancer

Near-infrared photoimmunotherapy (NIR-PIT) is a novel form of cancer treatment using conjugates of antibody against overexpressed antigens in cancers and photoabsorber IRDye700DX. HER2 is overexpressed in various cancers, for which molecular targeted therapy such as trastuzumab has been developed. The present study investigated the efficacy potential of HER2-targeted NIR-PIT using trastuzumab-IRDye700DX conjugate (Tra-IR700) in HER2-positive breast cancer. We first examined the reactivity of Tra-IR700 and the cytotoxicity of NIR-PIT in vitro. HER2-positive BT-474 and SK-BR-3 cells and HER2-negative BT-20 cells were used. Tra-IR700 fluorescence was only observed in HER2-positive breast cancer cell lines, and the fluorescence was localized to the cell surface. Furthermore, HER2-positive breast cancer cell lines treated with NIR-PIT showed swelling and blebbing shortly after irradiation, and eventually increased PI-positive dead cells. Next, tumor accumulation of Tra-IR700 and tumor damage by NIR-PIT were examined in vivo. Tra-IR700 was administered intravenously to a xenograft model in which BT-474 cells were implanted subcutaneously in BALB/c nude mice. Tra-IR700 fluorescence was the highest in tumor tissue 1 day after administration, and the fluorescence was localized to the cell membrane of tumor cells. At this time point, NIR-PIT resulted in diffuse necrosis of tumor tissues 1 day after irradiation. These results suggest that NIR-PIT with Tra-IR700 induces a highly selective therapeutic effect in a HER2-positive breast cancer model. NIR-PIT using Tra-IR700 is expected to be a novel treatment for HER2-positive cancers, including breast cancer.

Near-infrared photoimmunotherapy: design and potential applications for cancer treatment and beyond

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer treatment modality based on a target-specific photosensitizer conjugate (TSPC) composed of an NIR phthalocyanine photosensitizer and an antigen-specific recognition system. NIR-PIT has predominantly been used for targeted therapy of tumors via local irradiation with NIR light, following binding of TSPC to antigen-expressing cells. Physical stress-induced membrane damage is thought to be a major mechanism underlying NIR-PIT-triggered photokilling. Notably, NIR-PIT can rapidly induce immunogenic cell death and activate the adaptive immune response, thereby enabling its combination with immune checkpoint inhibitors. Furthermore, NIR-PIT-triggered “super-enhanced permeability and retention” effects can enhance drug delivery into tumors. Supported by its potential efficacy and safety, NIR-PIT is a rapidly developing therapeutic option for various cancers. Hence, this review seeks to provide an update on the (i) broad range of target molecules suitable for NIR-PIT, (ii) various types of receptor-selective ligands for designing the TSPC “magic bullet,” (iii) NIR light parameters, and (iv) strategies for enhancing the efficacy of NIR-PIT. Moreover, we review the potential application of NIR-PIT, including the specific design and efficacy in 19 different cancer types, and its clinical studies. Finally, we summarize possible NIR-PIT applications in noncancerous conditions, including infection, pain, itching, metabolic disease, autoimmune disease, and tissue engineering.

Optimal Light Dose for hEGFR-Targeted Near-Infrared Photoimmunotherapy

Simple Summary

Near-infrared photoimmunotherapy (NIR-PIT) is a cancer therapy that selectively destroys target cells by first injecting monoclonal antibodies conjugated with a photon absorber (IRDye700DX) into the subject and then activating it at the tumor site by applying nonthermal doses of NIR light at 690 nm. NIR-PIT causes immediate immunogenic cell death but also induces a slightly delayed activation of anti-tumor host immunity which can result in complete responses. The immediate therapeutic effect of NIR-PIT can be enhanced by increasing the dose of near-infrared light irradiation; however, this can cause local side effects such as edema. Since the activation of host immunity also adds to the anti-tumor effect it might be possible to reduce the light dose to avoid immediate side effects while maintaining efficacy of the therapy. In this study, we varied the light dose needed to achieve the maximum therapeutic effect in an immunocompetent mouse model. We show that higher-than-needed light doses caused significant local transient edema that could be avoided with lower but still effective light doses. Here, we present our strategy for optimizing the light dose for NIR-PIT.

Abstract

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer therapy that targets cancer cells using a monoclonal antibody-photon absorber conjugate (APC) that is bound to the target cell surface. Subsequent application of low levels of NIR light results in immediate cancer cell death. The anti-tumor effect of NIR-PIT in immunocompromised mice depends on immediate cancer cell death; therefore, the efficacy increases in a light-dose-dependent manner. However, NIR-PIT also induces a strong anti-tumor immune activation in immunocompetent mice that begins soon after therapy. Thus, it may be possible to reduce the light dose, which might otherwise cause local edema while maintaining therapeutic efficacy. In this study, we determined the optimal dose of NIR light in NIR-PIT based on a comparison of the therapeutic and adverse effects. Either one of two monoclonal antibodies (mAbs) against human epidermal growth factor receptor (hEGFR), Cetuximab or Panitumumab, were conjugated with a photo-absorbing chemical, IRDye700DX (IR700), and then injected in hEGFR-expressing mEERL (mEERL-hEGFR) tumor-bearing C57BL/6 immunocompetent mice or A431-GFP-luc tumor-bearing athymic immunocompromised mice. NIR light was varied between 0 to 100 J/cm² one day after administration of APC. In an immunocompromised mouse model, tumor growth was inhibited in a light-dose-dependent manner, yet extensive local edema and weight loss were observed at 100 J/cm². On the other hand, in an immunocompetent mouse model using the mEERL-hEGFR cell line, maximal tumor response was achieved at 50 J/cm², with a commensurate decrease in local edema. In this study, we show that a relatively low dose of NIR light is sufficient in an immunocompetent mouse model and avoids side effects seen with higher light doses required in immunocompetent mice. Thus, light dosing can be optimized in NIR-PIT based on the expected immune response.

Near-Infrared Photoimmunotherapy for Thoracic Cancers: A Translational Perspective

The conventional treatment of thoracic tumors includes surgery, anticancer drugs, radiation, and cancer immunotherapy. Light therapy for thoracic tumors has long been used as an alternative; conventional light therapy also called photodynamic therapy (PDT) has been used mainly for early-stage lung cancer. Recently, near-infrared photoimmunotherapy (NIR-PIT), which is a completely different concept from conventional PDT, has been developed and approved in Japan for the treatment of recurrent and previously treated head and neck cancer because of its specificity and effectiveness. NIR-PIT can apply to any target by changing to different antigens. In recent years, it has become clear that various specific and promising targets are highly expressed in thoracic tumors. In combination with these various specific targets, NIR-PIT is expected to be an ideal therapeutic approach for thoracic tumors. Additionally, techniques are being developed to further develop NIR-PIT for clinical practice. In this review, NIR-PIT is introduced, and its potential therapeutic applications for thoracic cancers are described.

Evaluation of Fluorescence Intensity and Antitumor Effect Using Real-Time Imaging in Photoimmunotherapy

Photoimmunotherapy (PIT) is a promising tumor-selective treatment method that uses light-absorbing dye-conjugated antibodies and light irradiation. It has been reported that IR700 fluorescence changes with light irradiation. The purpose of this study was to investigate the fluorescence intensity and antitumor effect of PIT using real-time fluorescence observation of tumors and predict the required irradiation dose. The near-infrared camera system LIGHTVISION was used to image IR700 during PIT treatment. IR700 showed a sharp decrease in fluorescence intensity in the early stage of treatment and almost reached a plateau at an irradiation dose of 40 J/cm. Cetuximab-PIT for A431 xenografts was performed at multiple doses from 0-100 J/cm. A significant antitumor effect was observed at 40 J/cm compared to no irradiation, and there was no significant difference between 40 J/cm and 100 J/cm. These results suggest that the rate of decay of the tumor fluorescence intensity correlates with the antitumor effect by real-time fluorescence imaging during PIT. In addition, when the fluorescence intensity of the tumor plateaued in real-time fluorescence imaging, it was assumed that the laser dose was necessary for treatment.

Imaging modalities for monitoring acute therapeutic effects after near-infrared photoimmunotherapy in vivo

Near-infrared photoimmunotherapy (NIR-PIT) induces immediate cell death after irradiation with near-infrared (NIR) light. Acute therapeutic effects caused by NIR-PIT before the change of tumor size is essential to be monitored by imaging modalities. We summarized and compared the imaging modalities for evaluating acute therapeutic effects after NIR-PIT, and aimed to provide a better understanding of advantages and disadvantages of each modality for evaluation in clinical applications. Fluorescence imaging and fluorescence lifetime, with high resolution, remains high accumulation of fluorescence dyes in the normal organs. High resolution and noninvasiveness are the major advantages of magnetic resonance imaging, while ¹⁸ F-fluorodeoxyglucose positron emission tomography provides information about the glucose metabolism. Optical coherence tomography provided more information about the blood vessels. Thus, all of the imaging modalities play an important role in evaluating acute therapeutic effects after NIR-PIT. Clinicians should choose suitable modality according to specific purpose and conditions in clinical application.

Near infrared photoimmunotherapy for cancers: A translational perspective

Near-infrared photoimmunotherapy (NIR-PIT) is a newly-developed, highly-selective cancer treatment, which utilizes a monoclonal antibody conjugated to a photoabsorbing dye, IRDye700DX (IR700). The antibody conjugate is injected into the patient and accumulates in the tumour. Within 24 h of injection the tumour is exposed to NIR light which activates the conjugate and causes rapid, selective cancer cell death. A global phase III clinical trial of NIR-PIT in recurrent head and neck squamous cell cancer (HNSCC) patients is currently underway. Conditional clinical approval for NIR-PIT in recurrent HNSCC has been granted in Japan as of September 2020. Not only does NIR-PIT induce highly selective and immediate cancer cell killing, but it also stimulates highly active anti-tumour immunity. While monotherapy with NIR-PIT has proven effective it is likely that combinations with immune-checkpoint inhibitors or additional NIR-PIT targeting immune suppressive cells in the tumour microenvironment will further improve results. In this review, we discuss the translational aspects of NIR-PIT especially in HNSCC, and potential future applications.