Near infrared photoimmunotherapy with an anti-mesothelin antibody

Rapid nanobody-based imaging of mesothelin expressing malignancies compatible with blocking therapeutic antibodies

Introduction

Mesothelin (MSLN) is overexpressed in a wide variety of cancers with few therapeutic options and has recently emerged as an attractive target for cancer therapy, with a large number of approaches currently under preclinical and clinical investigation. In this respect, developing mesothelin specific tracers as molecular companion tools for predicting patient eligibility, monitoring then response to mesothelin-targeting therapies, and tracking the evolution of the disease or for real-time visualisation of tumours during surgery is of growing importance.

Methods

We generated by phage display a nanobody (Nb S1) and used enzymatic approaches were used to site-directed conjugate Nb S1 with either ATTO 647N fluorochrome or NODAGA chelator for fluorescence and positron emission tomography imaging (PET) respectively.

Results

We demonstrated that Nb S1 displays a high apparent affinity and specificity for human mesothelin and demonstrated that the binding, although located in the membrane distal domain of mesothelin, is not impeded by the presence of MUC16, the only known ligand of mesothelin, nor by the therapeutic antibody amatuximab. In vivo experiments showed that both ATTO 647N and [68Ga]Ga-NODAGA-S1 rapidly and specifically accumulated in mesothelin positive tumours compared to mesothelin negative tumours or irrelevant Nb with a high tumour/background ratio. The ex vivo biodistribution profile analysis also confirmed a significantly higher uptake of Nb S1 in MSLN-positive tumours than in MSLNlow tumours.

Conclusion

We demonstrated for the first time the use of an anti-MSLN nanobody as PET radiotracer for same day imaging of MSLN+ tumours, targeting an epitope compatible with the monitoring of amatuximab-based therapies and current SS1-derived-drug conjugates.

Near Infrared Photoimmunotherapy: A Review of Recent Progress and Their Target Molecules for Cancer Therapy

Near infrared photoimmunotherapy (NIR-PIT) is a newly developed molecular targeted cancer treatment, which selectively kills cancer cells or immune-regulatory cells and induces therapeutic host immune responses by administrating a cancer targeting moiety conjugated with IRdye700. The local exposure to near-infrared (NIR) light causes a photo-induced ligand release reaction, which causes damage to the target cell, resulting in immunogenic cell death (ICD) with little or no side effect to the surrounding normal cells. Moreover, NIR-PIT can generate an immune response in distant metastases and inhibit further cancer attack by combing cancer cells targeting NIR-PIT and immune regulatory cells targeting NIR-PIT or other cancer treatment modalities. Several recent improvements in NIR-PIT have been explored such as catheter-driven NIR light delivery, real-time monitoring of cancer, and the development of new target molecule, leading to NIR-PIT being considered as a promising cancer therapy. In this review, we discuss the progress of NIR-PIT, their mechanism and design strategies for cancer treatment. Furthermore, the overall possible targeting molecules for NIR-PIT with their application for cancer treatment are briefly summarised.

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.

The Potential of Antibody Technology and Silver Nanoparticles for Enhancing Photodynamic Therapy for Melanoma

Melanoma is highly aggressive and is known to be efficient at resisting drug-induced apoptotic signals. Resection is currently the gold standard for melanoma management, but it only offers local control of the early stage of the disease. Metastatic melanoma is prone to recurrence, and has a poor prognosis and treatment response. Thus, the need for advanced theranostic alternatives is evident. Photodynamic therapy has been increasingly studied for melanoma treatment; however, it relies on passive drug accumulation, leading to off-target effects. Nanoparticles enhance drug biodistribution, uptake and intra-tumoural concentration and can be functionalised with monoclonal antibodies that offer selective biorecognition. Antibody–drug conjugates reduce passive drug accumulation and off-target effects. Nonetheless, one limitation of monoclonal antibodies and antibody–drug conjugates is their lack of versatility, given cancer’s heterogeneity. Monoclonal antibodies suffer several additional limitations that make recombinant antibody fragments more desirable. SNAP-tag is a modified version of the human DNA-repair enzyme, O6-alkylguanine-DNA alkyltransferase. It reacts in an autocatalytic and covalent manner with benzylguanine-modified substrates, providing a simple protein labelling system. SNAP-tag can be genetically fused with antibody fragments, creating fusion proteins that can be easily labelled with benzylguanine-modified payloads for site-directed delivery. This review aims to highlight the benefits and limitations of the abovementioned approaches and to outline how their combination could enhance photodynamic therapy for melanoma.

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.

Endoscopic Applications of Near-Infrared Photoimmunotherapy (NIR-PIT) in Cancers of the Digestive and Respiratory Tracts

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed and promising therapy that specifically destroys target cells by irradiating antibody-photo-absorber conjugates (APCs) with NIR light. APCs bind to target molecules on the cell surface, and when exposed to NIR light, cause disruption of the cell membrane due to the ligand release reaction and dye aggregation. This leads to rapid cell swelling, blebbing, and rupture, which leads to immunogenic cell death (ICD). ICD activates host antitumor immunity, which assists in killing still viable cancer cells in the treated lesion but is also capable of producing responses in untreated lesions. In September 2020, an APC and laser system were conditionally approved for clinical use in unresectable advanced head and neck cancer in Japan, and are now routine in appropriate patients. However, most tumors have been relatively accessible in the oral cavity or neck. Endoscopes offer the opportunity to deliver light deeper within hollow organs of the body. In recent years, the application of endoscopic therapy as an alternative to surgery for the treatment of cancer has expanded, providing significant benefits to inoperable patients. In this review, we will discuss the potential applications of endoscopic NIR-PIT, especially in thoracic and gastrointestinal cancers.

Hurdles for the wide implementation of photoimmunotherapy

Near infrared photoimmunotherapy (NIR-PIT) is a molecularly targeted treatment for cancers achieved by injecting a conjugate of IRDye700DX^® (IR700), a water-soluble silicon phthalocyanine derivative in the near infrared, and a monoclonal antibody that targets cancer cell antigens. NIR-PIT is a highly specific treatment with few side effects that results in rapid immunogenic cell death. Despite it being a very effective and innovative therapy, there are a few challenges preventing full implementation in clinical practice. These include the limits of near infrared light penetration, selection of targets, concerns about tumor lysis syndrome and drug costs. However, NIR-PIT has been approved by the regulatory authorities in Japan, allowing for exploration of how to mitigate challenges while maximizing the benefits of this treatment modality.

Near infrared photoimmunotherapy of cancer; possible clinical applications

Near-infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that uses an antibody-photo-absorber conjugate (APC) composed of a targeting monoclonal antibody conjugated with a photoactivatable phthalocyanine-derivative dye, IRDye700DX (IR700). APCs injected into the body can bind to cancer cells where they are activated by local exposure to NIR light typically delivered by a NIR laser. NIR light alters the APC chemical conformation inducing damage to cancer cell membranes, resulting in necrotic cell death within minutes of light exposure. NIR-PIT selectivity kills cancer cells by immunogenic cell death (ICD) with minimal damage to adjacent normal cells thus, leading to rapid recovery by the patient. Moreover, since NIR-PIT induces ICD only on cancer cells, NIR-PIT initiates and activates antitumor host immunity that could be further enhanced when combined with immune checkpoint inhibition. NIR-PIT induces dramatic changes in the tumor vascularity causing the super-enhanced permeability and retention (SUPR) effect that dramatically enhances nanodrug delivery to the tumor bed. Currently, a worldwide Phase 3 study of NIR-PIT for recurrent or inoperable head and neck cancer patients is underway. In September 2020, the first APC and accompanying laser system were conditionally approved for clinical use in Japan. In this review, we introduce NIR-PIT and the SUPR effect and summarize possible applications of NIR-PIT in a variety of cancers.

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.

Antibody-Based Targeted Interventions for the Diagnosis and Treatment of Skin Cancers

BACKGROUND

Cutaneous malignancies most commonly arise from skin epidermal cells. These cancers may rapidly progress from benign to a metastatic phase. Surgical resection represents the gold standard therapeutic treatment of non-metastatic skin cancer while chemo- and/or radiotherapy are often used against metastatic tumors. However, these therapeutic treatments are limited by the development of resistance and toxic side effects, resulting from the passive accumulation of cytotoxic drugs within healthy cells.

OBJECTIVE

This review aims to elucidate how the use of monoclonal Antibodies (mAbs) targeting specific Tumor Associated Antigens (TAAs) is paving the way to improved treatment. These mAbs are used as therapeutic or diagnostic carriers that can specifically deliver cytotoxic molecules, fluorophores or radiolabels to cancer cells that overexpress specific target antigens.

RESULTS

mAbs raised against TAAs are widely in use for e.g. differential diagnosis, prognosis and therapy of skin cancers. Antibody-Drug Conjugates (ADCs) particularly show remarkable potential. The safest ADCs reported to date use non-toxic photo-activatable Photosensitizers (PSs), allowing targeted Photodynamic Therapy (PDT) resulting in targeted delivery of PS into cancer cells and selective killing after light activation without harming the normal cell population. The use of near-infrared-emitting PSs enables both diagnostic and therapeutic applications upon light activation at the specific wavelengths.

CONCLUSION

Antibody-based approaches are presenting an array of opportunities to complement and improve current methods employed for skin cancer diagnosis and treatment.

Near Infrared Photoimmunotherapy; A Review of Targets for Cancer Therapy

Simple Summary

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer treatment that uses an antibody-photoabsorber (IRDye700DX) conjugate (APC) that is activated by NIR light irradiation. A major benefit of NIR-PIT is that only APC-bound cancer cells that are exposed to NIR light are killed by NIR-PIT; thus, minimal damage occurs in adjacent normal cells. NIR-PIT has now been applied to many cancers expressing various cell-surface target proteins using monoclonal antibodies designed to bind to them. Moreover, NIR-PIT is not limited to tumor antigens but can also be used to kill specific host cells that create immune-permissive environments in which tumors grow. Moreover, multiple targets can be treated simultaneously with NIR-PIT using a cocktail of APCs. NIR-PIT has great potential to treat a wide variety of cancers by targeting appropriate tumor cells, immune cells, or both, and can be augmented by other immunotherapies.

Abstract

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer treatment that uses an antibody-photoabsorber (IRDye700DX) conjugate (APC) that is activated by NIR light irradiation. In September 2020, the first APC and laser system were conditionally approved for clinical use in Japan. A major benefit of NIR-PIT is that only APC-bound cancer cells that are exposed to NIR light are killed by NIR-PIT; thus, minimal damage occurs in adjacent normal cells. These early trials have demonstrated that in addition to direct cell killing, there is a significant therapeutic host immune response that greatly contributes to the success of the therapy. Although the first clinical use of NIR-PIT targeted epidermal growth factor receptor (EGFR), many other targets are suitable for NIR-PIT. NIR-PIT has now been applied to many cancers expressing various cell-surface target proteins using monoclonal antibodies designed to bind to them. Moreover, NIR-PIT is not limited to tumor antigens but can also be used to kill specific host cells that create immune-permissive environments in which tumors grow. Moreover, multiple targets can be treated simultaneously with NIR-PIT using a cocktail of APCs. NIR-PIT can be used in combination with other therapies, such as immune checkpoint inhibitors, to enhance the therapeutic effect. Thus, NIR-PIT has great potential to treat a wide variety of cancers by targeting appropriate tumor cells, immune cells, or both, and can be augmented by other immunotherapies.

Nanomedicine in cancer therapy: promises and hurdles of polymeric nanoparticles

The limitations of current cancer treatments have stimulated the application of nanotechnology to develop more effective and safer cancer therapies. Remarkable progress has been made in the development of nanomedicine to overcome issues associated with conventional cancer treatment, including low drug solubility, insufficient targeting, and drug resistance. The modulation of nanoparticles allows the improvement of drug pharmacokinetics, leading to improved targeting and reduced side effects. In addition, nanoparticles can be conjugated to ligands that specifically target cancer cells. Furthermore, strategies that exploit tumor characteristics to locally trigger drug release have shown to increase targeted drug delivery. However, although some clinical successes have been achieved, most nanomedicines fail to reach the clinic. Factors that hinder clinical translation vary from the complexity of design, incomplete understanding of biological mechanisms, and high demands during the manufacturing process. Clinical translation might be improved by combining knowledge from different disciplines such as cell biology, chemistry, and tumor pathophysiology. An increased understanding on how nanoparticle modifications affect biological systems is pivotal to improve design, eventually aiding development of more effective nanomedicines. This review summarizes the key successes that have been made in nanomedicine, including improved drug delivery and release by polymeric nanoparticles as well as the introduction of strategies that overcome drug resistance. In addition, the application of nanomedicine in immunotherapy is discussed, and several remaining challenges addressed.

Near-infrared photoimmunotherapy targeting human-EGFR in a mouse tumor model simulating current and future clinical trials

Background

near-infrared photoimmunotherapy (NIR-PIT) is a cancer treatment that uses antibody-photoabsorber (IRDye700DX, IR700) conjugates (APCs) which bind to target cells and are photoactivated by NIR light inducing rapid necrotic cell death. NIR-PIT targeting human epidermal growth factor receptor (hEGFR) has been shown to destroy hEGFR expressing human tumor cells and to be effective in immunodeficient mouse models. NIR-PIT can also be targeted to cells in the tumor microenvironment, for instance, CD25-targeted NIR-PIT can be used to selectively deplete regulatory T cells (Tregs) within a tumor. The aim of this study was to evaluate the combined therapeutic efficacy of hEGFR and CD25-targeted NIR-PIT in a newly established hEGFR expressing murine oropharyngeal cell line (mEERL-hEGFR).

Methods

panitumumab conjugated with IR700 (pan-IR700) was used as the cancer cell-directed component of NIR-PIT and anti-CD25-F(ab′)₂-IR700 was used as the tumor microenvironment-directed component of NIR-PIT. Efficacy was evaluated using tumor-bearing mice in four groups: (1) non-treatment group (control), (2) pan-IR700 based NIR-PIT (pan-PIT), (3) anti-CD25-F(ab′)₂-IR700 based NIR-PIT (CD25-PIT), (4) combined NIR-PIT with pan-IR700 and anti-CD25- F(ab′)₂-IR700 (combined PIT).

Findings

the combined PIT group showed the greatest inhibition of tumor growth. Destruction of cancer cells likely leads to an immune response which is amplified by the loss of Tregs in the tumor microenvironment.

Interpretation

combined hEGFR and CD25-targeted NIR-PIT is a promising treatment for hEGFR expressing cancers in which Treg cells play an immunosuppressive role.

Near-infrared photoimmunotherapy of cancer: a new approach that kills cancer cells and enhances anti-cancer host immunity

Near-infrared photoimmunotherapy (NIR-PIT) is a recently developed hybrid cancer therapy that directly kills cancer cells as well as producing a therapeutic host immune response. Conventional immunotherapies, such as immune-activating cytokine therapy, checkpoint inhibition, engineered T cells and suppressor cell depletion, do not directly destroy cancer cells, but rely exclusively on activating the immune system. NIR-PIT selectively destroys cancer cells, leading to immunogenic cell death that initiates local immune reactions to released cancer antigens from dying cancer cells. These are characterized by rapid maturation of dendritic cells and priming of multi-clonal cancer-specific cytotoxic T cells that kill cells that escaped the initial direct effects of NIR-PIT. The NIR-PIT can be applied to a wide variety of cancers either as monotherapy or in combination with conventional immune therapies to further activate anti-cancer immunity. A global Phase 3 clinical trial (https://clinicaltrials.gov/ct2/show/NCT03769506) of NIR-PIT targeting the epidermal growth factor receptor (EGFR) in patients with recurrent head and neck cancer is underway, employing RM1929/ASP1929, a conjugate of anti-EGFR antibody (cetuximab) plus the photo-absorber IRDye700DX (IR700). NIR-PIT has been given fast-track recognition by regulators in the USA and Japan. A variety of imaging methods, including direct IR700 fluorescence imaging, can be used to monitor NIR-PIT. As experience with NIR-PIT grows, additional antibodies will be employed to target additional antigens on other cancers or to target immune-suppressor cells to enhance host immunity. NIR-PIT will be particularly important in patients with localized and locally advanced cancers and may help such patients avoid side-effects associated with surgery, radiation and chemotherapy.

Near-Infrared Photoimmunotherapy for Cancers of the Gastrointestinal Tract

BACKGROUND

Cancers of the gastrointestinal (GI) tract are the common leading cause of cancer-related death in the world. Recent advances in cancer therapies such as intensive multidrug chemotherapy and molecular targeted treatment have improved therapeutic efficacy; however, the outcomes are not satisfied. Moreover, these therapies also cause severe side effects. New type of cancer therapies is urgently needed to improve the outcomes and to reduce side effects of GI tract cancers.

SUMMARY

This account is a comprehensive review article on the newly developed, photochemistry-based cancer therapy named as near-infrared photoimmunotherapy (NIR-PIT). NIR-PIT is a highly selective tumor treatment that employs an antibody-photoabsorber conjugate, which is activated by near-infrared light. A world-wide phase 3 clinical trial of NIR-PIT against recurrent head and neck cancer patients is currently underway. NIR-PIT differs from conventional cancer therapies such as surgery, chemotherapy, and radiation in its selectivity for killing cancer cells and cells treated with NIR-PIT leading to immunogenic cell death. Preclinical research in animals with combining cancer-targeting NIR-PIT and other cancer immunotherapies could lead to responses not only in local tumor but also in distant metastases. NIR-PIT also leads to an immediate and dramatic increase in vascular permeability after therapy. From these aspects, NIR-PIT appears to be a promising new form of cancer therapy. NIR-PIT could be readily translated into clinical use for virtually any cancers in the near future provided suitable humanized antibodies are available. Here, we describe the specific advantages and applications of NIR-PIT in the GI tract. Key Messages: We believe that NIR-PIT with NIR excitation light, which can be delivered via a fiber optic diffuser through endoscopes, is a promising method for a new treatment of GI cancers.

Cadherin-17 Targeted Near-Infrared Photoimmunotherapy for Treatment of Gastrointestinal Cancer

In cancer photodynamic therapy (PDT), a photosensitizer taken up by cancer cells can generate reactive oxygen species upon near-infrared light activation to induce cancer cell death. To increase PDT potency and decrease its adverse effect, one approach is to conjugate the photosensitizer with an antibody that specifically targets cancer cells. In the present study, IR700, a hydrophilic phthalocyanine photosensitizer, was conjugated to the humanized monoclonal antibody ARB102, which binds specifically cadherin-17 (CDH17 aka CA17), a cell surface marker highly expressed in gastrointestinal cancer to produce ARB102-IR700. Photoimmunotherapy (PIT) of gastrointestinal cancer cell lines was conducted by ARB102-IR700 treatment and near-infrared light irradiation. The results showed that ARB102-IR700 PIT could induce cell death in CDH17-positive cancer cells with high potency. In a co-culture model, CDH17-negative and CDH17-overexpressing SW480 cells were labeled with distinct fluorescent dyes and cultured together prior to PIT treatment. The results confirmed that ARB102-IR700 PIT could kill CDH17-positive cells specifically, while leaving the adjacent CDH17-negative cells unaffected. An in vivo efficacy study was conducted using a pancreatic adenocarcinoma AsPC-1 xenograft tumor model in nude mice. Fluorescence scanning indicated that ARB102-IR700 accumulated specifically in the tumor sites. To perform PIT, at 24 and 48 h postinjection, mice were irradiated with a 680 nm laser at the tumor site to activate the photosensitizer. It was shown that ARB102-IR700 PIT could inhibit tumor growth significantly. In summary, this study demonstrated that the novel ARB102-IR700 is a promising agent for PIT in gastrointestinal cancers.

Antibody-Based Immunotherapy: Alternative Approaches for the Treatment of Metastatic Melanoma

Melanoma is the least common form of skin cancer and is associated with the highest mortality. Where melanoma is mostly unresponsive to conventional therapies (e.g., chemotherapy), BRAF inhibitor treatment has shown improved therapeutic outcomes. Photodynamic therapy (PDT) relies on a light-activated compound to produce death-inducing amounts of reactive oxygen species (ROS). Their capacity to selectively accumulate in tumor cells has been confirmed in melanoma treatment with some encouraging results. However, this treatment approach has not reached clinical fruition for melanoma due to major limitations associated with the development of resistance and subsequent side effects. These adverse effects might be bypassed by immunotherapy in the form of antibody–drug conjugates (ADCs) relying on the ability of monoclonal antibodies (mAbs) to target specific tumor-associated antigens (TAAs) and to be used as carriers to specifically deliver cytotoxic warheads into corresponding tumor cells. Of late, the continued refinement of ADC therapeutic efficacy has given rise to photoimmunotherapy (PIT) (a light-sensitive compound conjugated to mAbs), which by virtue of requiring light activation only exerts its toxic effect on light-irradiated cells. As such, this review aims to highlight the potential clinical benefits of various armed antibody-based immunotherapies, including PDT, as alternative approaches for the treatment of metastatic melanoma.

Near Infrared Light Triggered Photo/Immuno-Therapy Toward Cancers

Nanomaterials-based phototherapies, mainly including photothermal therapy (PTT), photodynamic therapy (PDT) and photoimmunotherapy (PIT), present high efficacy, minimal invasion and negligible adverse effects in cancer treatment. The integrated phototherapeutic modalities can enhance the efficiency of cancer immunotherapy for clinical application transformation. The near-infrared (NIR) light source enables phototherapies with the high penetration depth in the biological tissues, less toxic to normal cells and tissues and a low dose of light irradiation. Mediated via the novel NIR-responsive nanomaterials, PTT and PDT are able to provoke cancer cells apoptosis from the generated heat and reactive oxygen species, respectively. The released cancer-specific antigens and membrane damage danger signals from the damaged cancer cells trigger immune responses, which would enhance the antitumor efficacy via a variety of immunotherapy. This review summarized the recent advances in NIR-triggered photo-/immune-therapeutic modalities and their synergistic mechanisms and applications toward cancers. Furthermore, the challenges, potential solutions and future directions of NIR-triggered photo-/immunotherapy were briefly discussed.

Targeted Phototherapy for Malignant Pleural Mesothelioma: Near-Infrared Photoimmunotherapy Targeting Podoplanin

Malignant pleural mesothelioma (MPM) has extremely limited treatment despite a poor prognosis. Moreover, molecular targeted therapy for MPM has not yet been implemented; thus, a new targeted therapy is highly desirable. Near-infrared photoimmunotherapy (NIR-PIT) is a recently developed cancer therapy that combines the specificity of antibodies for targeting tumors with toxicity induced by the photoabsorber after exposure to NIR-light. In this study, we developed a new phototherapy targeting podoplanin (PDPN) for MPM with the use of both NIR-PIT and an anti-PDPN antibody, NZ-1. An antibody–photosensitizer conjugate consisting of NZ-1 and phthalocyanine dye was synthesized. In vitro NIR-PIT-induced cytotoxicity was measured with both dead cell staining and luciferase activity on various MPM cell lines. In vivo NIR-PIT was examined in both the flank tumor and orthotopic mouse model with in vivo real-time imaging. In vitro NIR-PIT-induced cytotoxicity was NIR-light dose dependent. In vivo NIR-PIT led to significant reduction in both tumor volume and luciferase activity in a flank model (p < 0.05, NIR-PIT group versus NZ-1-IR700 group). The PDPN-targeted NIR-PIT resulted in a significant antitumor effect in an MPM orthotopic mouse model (p < 0.05, NIR-PIT group versus NZ-1-IR700 group). This study suggests that PDPN-targeted NIR-PIT could be a new promising treatment for MPM.

The Effect of Antibody Fragments on CD25 Targeted Regulatory T Cell Near-Infrared Photoimmunotherapy

Regulatory T (Treg) cells play a major role in immune suppression permitting tumors to evade immune surveillance. Depletion of intratumoral Treg cells can result in tumor regression. However, systemic depletion of Tregs may also induce autoimmune adverse events. Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cell-specific cancer therapy that locally kills specific cells in the tumor. Antibody-photoabsorber (IRDye700DX) conjugates (APC) are injected and bind to the tumor, and subsequent administration of NIR light to the tumor results in rapid cell death only in targeted cells. CD25-targeted NIR-PIT has been shown to induce spatially selective depletion of tumor-associated Treg cells. In this study, we compared the efficacy of an antibody fragment, anti-CD25-F(ab')₂, and a full antibody, anti-CD25-IgG, as agents for NIR-PIT. Tumor-bearing mice were divided into four groups: (1) no treatment; (2) anti-CD25-IgG-IR700 i.v. only; (3) anti-CD25-F(ab')₂-IR700 i.v. with NIR light exposure; and (4) anti-CD25-IgG-IR700 i.v. with NIR light exposure. Although both CD25-targeted NIR-PITs resulted in significant tumor growth inhibition, the anti-CD25-F(ab')₂-IR700 based NIR-PIT was superior to the anti-CD25-IgG-IR700 NIR-PIT. The anti-CD25-F(ab')₂-IR700 demonstrated faster clearance from the body than the anti-CD25-IgG-IR700. Sustained circulation of anti-CD25-IgG-IR700 may block IL-2 binding on the activated effector T-cells decreasing immune response. In conclusion, anti-CD25-F(ab')₂ based NIR-PIT was more effective in reducing tumor growth than anti-CD25-IgG based NIR-PIT. Absence of the Fc portion of the APC leads to faster clearance and therefore promotes a superior activated T cell response in tumors.

Near-Infrared Photoimmunotherapy of Cancer

This Account is the first comprehensive review article on the newly developed, photochemistry-based cancer therapy near-infrared (NIR) photoimmunotherapy (PIT). NIR-PIT is a molecularly targeted phototherapy for cancer that is based on injecting a conjugate of a near-infrared, water-soluble, silicon-phthalocyanine derivative, IRdye700DX (IR700), and a monoclonal antibody (mAb) that targets an expressed antigen on the cancer cell surface. Subsequent local exposure to NIR light turns on this photochemical "death" switch, resulting in the rapid and highly selective immunogenic cell death (ICD) of targeted cancer cells. ICD occurs as early as 1 min after exposure to NIR light and results in irreversible morphologic changes only in target-expressing cells based on the newly discovered photoinduced ligand release reaction that induces physical changes on conjugated antibody/antigen complex resulting in functional damage on cell membrane. Meanwhile, immediately adjacent receptor-negative cells are totally unharmed. Because of its highly targeted nature, NIR-PIT carries few side effects and healing is rapid. Evaluation of the tumor microenvironment reveals that ICD induced by NIR-PIT results in rapid maturation of immature dendritic cells adjacent to dying cancer cells initiating a host anticancer immune response, resulting in repriming of polyclonal CD8⁺T cells against various released cancer antigens, which amplifies the therapeutic effect of NIR-PIT. NIR-PIT can target and treat virtually any cell surface antigens including cancer stem cell markers, that is, CD44 and CD133. A first-in-human phase 1/2 clinical trial of NIR-PIT using cetuximab-IR700 (RM1929) targeting EGFR in inoperable recurrent head and neck cancer patients successfully concluded in 2017 and led to "fast tracking" by the FDA and a phase 3 trial ( https://clinicaltrials.gov/ct2/show/NCT03769506 ) that is currently underway in 3 countries in Asia, US/Canada, and 4 countries in EU. The next step for NIR-PIT is to further exploit the immune response. Preclinical research in animals with intact immune systems has shown that NIT-PIT targeting of immunosuppressor cells within the tumor, such as regulatory T-cells, can further enhance tumor-cell-selective systemic host-immunity leading to significant responses in distant metastatic tumors, which are not treated with light. By combining cancer-targeting NIR-PIT and immune-activating NIR-PIT or other cancer immunotherapies, NIR-PIT of a local tumor, could lead to responses in distant metastases and may also inhibit recurrences due to activation of systemic anticancer immunity and long-term immune memory without the systemic autoimmune adverse effects often associated with immune checkpoint inhibitors. Furthermore, NIR-PIT also enhances nanodrug delivery into tumors up to 24-fold superior to untreated tumors with conventional EPR effects by intensively damaging cancer cells behind tumor vessels. We conclude by describing future advances in this novel photochemical cancer therapy that are likely to further enhance the efficacy of NIR-PIT.

Near infrared photoimmunotherapy using a fiber optic diffuser for treating peritoneal gastric cancer dissemination

BACKGROUND

Peritoneal dissemination (PD) of abdominal malignancies is a common form of metastasis and its presence signals a poor prognosis. New treatment is required for patients with PD. Near infrared photoimmunotherapy (NIR-PIT) is a highly selective tumor treatment that employs an antibody-photo-absorber conjugate (APC). In this study, we investigate in vitro and in vivo efficacy of trastuzumab (tra)-IR700DX NIR-PIT on a human epidermal growth factor receptor type 2 (HER2)-positive gastric cancer cell line.

METHODS

NIR-PIT effects were investigated in vitro and in vivo. Disseminated peritoneal implants mice were separated into 5 groups: (1) no treatment; (2) tra-IR700 i.v. only; (3) NIR light only; (4) NIR-PIT; (5) repeated NIR-PIT. The peritoneal cavity was irradiated with NIR light using a fiber optic diffuser delivered through the catheter.

RESULTS

Specific binding and cell-specific killing was observed after NIR-PIT in vitro. In the in vivo study, fluorescence endoscopy showed high tumor accumulation of tra-IR700 within tumors. Significantly prolonged survival was achieved in the three treatment groups (tra-IR700 i.v. only, NIR-PIT, and repeated NIR-PIT groups) compared with control and NIR light only group (p < 0.05 for tra-IR700 i.v. only, p < 0.01 for NIR-PIT, and p < 0.0001 for repeated NIR-PIT). Moreover, most prolonged survival was shown for the repeated NIR-PIT group (p < 0.0001 vs tra-IR700 i.v. only, p < 0.01 vs NIR-PIT).

CONCLUSION

NIR-PIT using a fiber optic diffuser to deliver light is a promising candidate for the treatment of disseminated peritoneal metastases and could be readily translated to humans.

Host Immunity Following Near-Infrared Photoimmunotherapy Is Enhanced with PD-1 Checkpoint Blockade to Eradicate Established Antigenic Tumors

Near-infrared photoimmunotherapy (NIR-PIT) induces immunogenic cell death but has mostly failed to induce durable antitumor responses in syngenic tumor mouse models. We hypothesized that adaptive immune resistance could be limiting durable responses after treatmemt with NIR-PIT. We investigated the effects of combining NIR-PIT targeting cell-surface CD44 and PD-1 blockade in multiple syngeneic tumor models. In two of three models, NIR-PIT monotherapy halted tumor growth, enhanced dendritic cell tumor infiltration, and induced de novo tumor antigen-specific T-cell responses absent at baseline. The addition of PD-1 blockade reversed adaptive immune resistance, resulting in both enhanced preexisting tumor antigen-specific T-cell responses and enhanced de novo T-cell responses induced by NIR-PIT. Enhanced immune responses correlated with shared tumor antigen expression, suggesting that antigenicity is a major determinant of response to combination NIR-PIT and PD-1 blockade. Combination treatment induced complete rejection of MC38 tumors treated with NIR-PIT, as well as untreated, distant tumors. Accordingly, tumor antigen-specific T-cell responses were measured in both treated and untreated tumors, validating the development of systemic antitumor immunity. Mice that cleared tumors resisted subsequent tumor challenge, indicating the presence of systemic immune memory. Cumulatively, these results demonstrate reversal of adaptive immune resistance following induction of innate and adaptive immunity by NIR-PIT, resulting in high rates of tumor rejection and/or significant tumor growth control in antigenic syngeneic models of cancer.

Targeted Photodynamic Therapy: A Novel Approach to Abolition of Human Cancer Stem Cells

Cancer is a global burden that has prompted extensive research into prevention and treatment, over many decades. Scientific studies have shown that subset of cells within a tumour, known as cancer stem cells (CSCs), are responsible for tumourigenesis, metastasis, drug resistance, and recurrences. CSCs have characteristic features of enhanced self-renewal, proliferation, and limited but multidirectional differentiation capacity. The discovery of CSCs has initiated extensive research into novel cancer treatment regimes. Evidence indicates that CSCs are resistant to conventional chemo- and radiation therapy leading to treatment failures, cancer metastasis, secondary cancer formation, and relapse. Because of the observed phenomena in the course of cancer prognosis, a need for treatment modalities targeting CSCs is important. Photodynamic therapy (PDT) is a clinically approved, minimally invasive, therapeutic procedure that can exert a selective cytotoxic activity toward cancerous cells while reducing toxicity to normal cells. It uses a photosensitizer (PS) that becomes excited when subjected to light at a specific wavelength, and the PS forms reactive oxygen species (ROS) killing malignant cells. Currently, PDT is being investigated as a target specific treatment for CSCs by the addition of carrier molecules and antibody conjugates bound to the PS. Targeted PDT (TPDT) may be able to not only eradicate the tumour mass but kill CSCs as well.

Endoscopic near infrared photoimmunotherapy using a fiber optic diffuser for peritoneal dissemination of gastric cancer

Near infrared photoimmunotherapy (NIR‐PIT) is a highly selective tumor treatment that employs an antibody‐photo‐absorber conjugate (APC) which is activated by near infrared light. Here, we describe the efficacy of endoscopic NIR‐PIT using the APC trastuzumab‐IR700DX (tra‐IR700) in the setting of human epidermal growth factor 2 positive (HER2 + ) gastric carcinoma with peritoneal disseminations. In this in vivo study, fluorescence endoscopy showed high tumor accumulation of tra‐IR700 within disseminated peritoneal implants. Mice with disseminated peritoneal gastric cancer were separated into 4 groups: (i) control (no treatment); (ii) tra‐IR700 i.v. only; (iii) NIR light only; and (iv) endoscopic NIR‐PIT. NIR light irradiation was carried out through a fiber optic diffuser under endoscopic guidance. In vivo bioluminescence images showed significantly greater therapeutic effect in the endoscopic NIR‐PIT group than that in the control groups (P < .01 vs other control groups). Histological analysis showed diffuse cancer cell death in NIR‐PIT‐treated tumors. In conclusion, NIR‐PIT with NIR light delivered via an endoscopic fiber optic diffuser is a promising method for the treatment of peritoneal dissemination of gastric cancer. Moreover, this technique could be readily used in other types of cancers with peritoneal dissemination provided that suitable antibodies could be found.

3D mesoscopic fluorescence tomography for imaging micro-distribution of antibody-photon absorber conjugates during near infrared photoimmunotherapy in vivo

As a novel low-side-effect cancer therapy, photo-immunotherapy (PIT) is based on conjugating monoclonal antibody (mAb) with a near-infrared (NIR) phthalocyanine dye IRDye700DX (IR 700). IR700 is not only fluorescent to be used as an imaging agent, but also phototoxic. When illuminating with NIR light, PIT can induce highly-selective cancer cell death while leaving most of tumor blood vessels unharmed, leading to an effect termed super-enhanced permeability and retention (SUPR), which can significantly improve the effectiveness of anti-cancer drug. Currently, the therapeutic effects of PIT are monitored using 2D macroscopic fluorescence reflectance imager, which lacks the resolution and depth information to reveal the 3D distribution of mAb-IR700. In the study, we applied a multi-modal optical imaging approach including high-resolution optical coherence tomography (OCT) and high-sensitivity fluorescence laminar optical tomography (FLOT), to provide 3D tumor micro-structure and micro-distribution of mAb-IR700 in the tumor simultaneously during PIT in situ and in vivo. The multi-wavelength FLOT can also provide the blood vessels morphology of the tumor. Thus, the 3D FLOT reconstructed images allow us to evaluate the IR700 fluorescence distribution change with respect to the blood vessels and at different tumor locations/depths non-invasively, thereby enabling evaluation of the therapeutic effects in vivo and optimization of treatment regimens accordingly. The mAb-IR700 can access more tumor areas after PIT treatment, which can be explained by increased vascular permeability immediately after NIR-PIT. Two-photon microscopy was also used to record the mAb-IR700 on the tumor surface near the blood vessels to verify the results.

Near infrared photoimmunotherapy targeting bladder cancer with a canine anti-epidermal growth factor receptor (EGFR) antibody

Anti-epidermal growth factor receptor (EGFR) antibody therapy is used in EGFR expressing cancers including lung, colon, head and neck, and bladder cancers, however results have been modest. Near infrared photoimmunotherapy (NIR-PIT) is a highly selective tumor treatment that employs an antibody-photo-absorber conjugate which is activated by NIR light. NIR-PIT is in clinical trials in patients with recurrent head and neck cancers using cetuximab-IR700 as the conjugate. However, its use has otherwise been restricted to mouse models. This is an effort to explore larger animal models with NIR-PIT. We describe the use of a recombinant canine anti-EGFR monoclonal antibody (mAb), can225IgG, conjugated to the photo-absorber, IR700DX, in three EGFR expressing canine transitional cell carcinoma (TCC) cell lines as a prelude to possible canine clinical studies. Can225-IR700 conjugate showed specific binding and cell-specific killing after NIR-PIT on EGFR expressing cells in vitro. In the in vivo study, can225-IR700 conjugate demonstrated accumulation of the fluorescent conjugate with high tumor-to-background ratio. Tumor-bearing mice were separated into 4 groups: (1) no treatment; (2) 100 µg of can225-IR700 i.v. only; (3) NIR light exposure only; (4) 100 µg of can225-IR700 i.v., NIR light exposure. Tumor growth was significantly inhibited by NIR-PIT treatment compared with the other groups (p < 0.001), and significantly prolonged survival was achieved (p < 0.001 vs. other groups) in the treatment groups. In conclusion, NIR-PIT with can225-IR700 is a promising treatment for canine EGFR-expressing cancers, including invasive transitional cell carcinoma in pet dogs, that could provide a pathway to translation to humans.

Near-infrared photoimmunotherapy: a comparison of light dosing schedules

Near infrared photoimmunotherapy (NIR-PIT) is a newly-developed cancer therapy in which a monoclonal antibody is conjugated to a near-infrared photoabsorber, IR700 to form an antibody photoabsorber conjugate (APC). After the APC binds to cancer cells expressing the cognate antigen, exposure to NIR light results in rapid, highly selective necrotic cell death of the cancer cells with minimal off-target effects. Several hours after NIR-PIT, the tumor vessels become supraphysiologically permeable and circulating APC can therefore readily leak into the already-treated tumor space where it can bind with viable cancer cells that is called super-enhanced permeability and retention effect. The presence of the SUPR effect after NIR-PIT has prompted regimens in which there is a repeat exposure of NIR light 24 hours after the initial NIR-PIT to take advantage of the leakage of additional APC deeper into the tumor. However, this post-treatment APC penetration was fully induced within 3 hours, therefore, it is possible that repeated exposures of NIR light could be administered much earlier than 24 hours and still produce the same effects. To test this idea, we compared several modes of delivering additional doses of light after initial NIR-PIT. We found that repeated exposures of NIR light starting 3 hours after initial NIR-PIT produced equal or superior results to more delayed exposures of NIR light. This finding has practical implications of an easy-to-perform regimen as repeated light exposures could be performed during a single day rather than extending the procedure over two days which is the current recommendation.

A Review of Photodynamic Therapy for Neoplasms of the Head and Neck

Photodynamic therapy (PDT) involves the use of a phototoxic drug which is activated by low powered laser light to destroy neoplastic cells. Multiple photosensitizers have been studied and tumors have been treated in a variety of head and neck sites over the last 30 years. PDT can effectively treat head and neck tumors, particularly those of the superficial spreading type, and the classic application of this technology has been in the patient with a wide field of dysplastic change and superficial carcinomatosis. Interstitial treatment has been used to treat more invasive cancer. Data is available from case series and institutional experiences, but very little randomized data is available. We review the mechanisms of action, historical development, available data, and current knowledge regarding PDT for the various head and neck subsites, and discuss possible future directions, with an emphasis on clinical application.

Near-infrared photoimmunotherapy with galactosyl serum albumin in a model of diffuse peritoneal disseminated ovarian cancer

Near-infrared photoimmunotherapy (NIR-PIT) is a highly cell-selective cancer therapy based on an armed antibody conjugated with a phthalocyanine-based photo-absorber, IRDye700DX (IR700). NIR-PIT can quickly kill target cells that express specific proteins on the cellular membrane but only when the antibody-IR700 conjugate binds to the cell membrane and is then exposed to NIR light. NIR-PIT is highly selective based on the specificity of the antibody. Galactosyl serum albumin (GSA) is composed of albumin decorated with galactose molecules conjugated to the carboxyl groups of albumin. GSA binds to beta-D-galactose receptors, a surface lectin, which are overexpressed on the cell surface of many cancers, including ovarian cancers and is quickly internalized after binding. Here, we demonstrate the feasibility of NIR-PIT in a model of disseminated peritoneal ovarian cancer (SHIN3 cells) using GSA-IR700 that binds to beta-D-galactose receptors. GSA-IR700 bound quickly to SHIN3 cells, then accumulated in the endo-lysosomes. Cell-specific killing was observed in vitro, yet a relatively large dose of NIR light exposure was required for cell killing compared to antibody-IR700 conjugates. To evaluate in vivo therapeutic effects of GSA-IR700 NIR-PIT, peritoneal disseminated SHIN3 tumor-bearing mice were separated into four groups: no treatment; NIR light only; GSA-IR700 only; and GSA-IR700 NIR-PIT. Repeated NIR-PIT showed significant suppression of tumor based on bioluminescence compared to the other groups (p < 0.05). Thus, repeated NIR-PIT using GSA-IR700 can achieve efficient antitumor effects, although GSA-IR700 NIR-PIT was less effective than antibody-IR700 NIR-PIT conjugates likely due to the rapid internalization of GSA-IR700.

Near Infrared Photoimmunotherapy with Combined Exposure of External and Interstitial Light Sources

Near infrared photoimmunotherapy (NIR-PIT) is a new target-cell-specific cancer treatment that induces highly selective necrotic/immunogenic cell death after systemic administration of a photoabsorber antibody conjugate and subsequent NIR light exposure. However, the depth of NIR light penetration in tissue (approximately 2 cm) with external light sources limits the therapeutic effects of NIR-PIT. Interstitial light exposure using cylindrical diffusing optical fibers can overcome this limitation. The purpose in this study was to compare three NIR light delivery methods for treating tumors with NIR-PIT using a NIR laser system at an identical light energy; external exposure alone, interstitial exposure alone, and the combination. Panitumumab conjugated with the photoabsorber IRDye-700DX (pan-IR700) was intravenously administered to mice with A431-luc xenografts which are epithelial growth factor receptor (EGFR) positive. One and 2 days later, NIR light was administered to the tumors using one of three methods. Interstitial exposure alone and in combination with external sources showed the greatest decrease in bioluminescence signal intensity. Additionally, the combination of external and interstitial NIR light exposure showed significantly greater tumor size reduction and prolonged survival after NIR-PIT compared to external exposure alone. This result suggested that the combination of external and interstitial NIR light exposure was more effective than externally applied light alone. Although external exposure is the least invasive means of delivering light, the combination of external and interstitial exposures produces superior therapeutic efficacy in tumors greater than 2 cm in depth from the tissue surface.

Near infrared photoimmunotherapy with avelumab, an anti-programmed death-ligand 1 (PD-L1) antibody

Near Infrared-Photoimmunotherapy (NIR-PIT) is a highly selective tumor treatment that employs an antibody-photo-absorber conjugate (APC). Programmed cell death protein-1 ligand (PD-L1) is emerging as a molecular target. Here, we describe the efficacy of NIR-PIT, using fully human IgG1 anti-PD-L1 monoclonal antibody (mAb), avelumab, conjugated to the photo-absorber, IR700DX, in a PD-L1 expressing H441 cell line, papillary adenocarcinoma of lung. Avelumab-IR700 showed specific binding and cell-specific killing was observed after exposure of the cells to NIR in vitro. In the in vivo study, avelumab-IR700 showed high tumor accumulation and high tumor-background ratio. Tumor-bearing mice were separated into 4 groups: (1) no treatment; (2) 100 μg of avelumab-IR700 i.v.; (3) NIR light exposure only, NIR light was administered; (4) 100 μg of avelumab-IR700 i.v., NIR light was administered. Tumor growth was significantly inhibited by NIR-PIT treatment compared with the other groups (p < 0.001), and significantly prolonged survival was achieved (p < 0.01 vs other groups). In conclusion, the anti-PD-L1 antibody, avelumab, is suitable as an APC for NIR-PIT. Furthermore, NIR-PIT with avelumab-IR700 is a promising candidate of the treatment of PD-L1-expressing tumors that could be readily translated to humans.

Fluorescence-Guided Surgery

Surgical resection of cancer remains an important treatment modality. Despite advances in preoperative imaging, surgery itself is primarily guided by the surgeon’s ability to locate pathology with conventional white light imaging. Fluorescence-guided surgery (FGS) can be used to define tumor location and margins during the procedure. Intraoperative visualization of tumors may not only allow more complete resections but also improve safety by avoiding unnecessary damage to normal tissue which can also reduce operative time and decrease the need for second-look surgeries. A number of new FGS imaging probes have recently been developed, complementing a small but useful number of existing probes. In this review, we describe current and new fluorescent probes that may assist FGS.

Syngeneic Mouse Models of Oral Cancer Are Effectively Targeted by Anti-CD44-Based NIR-PIT

Oral cavity squamous cell carcinoma (OSCC) is considered one of the most aggressive subtypes of cancer. Anti-CD44 monoclonal antibodies (mAb) are a potential therapy against CD44 expressing OSCC; however, to date the therapeutic effects have been disappointing. Here, a new cancer treatment is described, near-infrared photoimmunotherapy (NIR-PIT), that uses anti-CD44 mAbs conjugated to the photoabsorber IR700DX. This conjugate is injected into mice harboring one of three CD44 expressing syngeneic murine oral cancer cell (MOC) lines, MOC1 (immunogenic), MOC2 mKate2 (moderately immunogenic), and MOC2-luc (poorly immunogenic). Binding of the anti-CD44-IR700 conjugate was shown to be specific and cell-specific cytotoxicity was observed after exposure of the cells to NIR light in vitro The anti-CD44-IR700 conjugate, when assessed in vivo, demonstrated deposition within the tumor with a high tumor-to-background ratio. Tumor-bearing mice were separated into four cohorts: no treatment; 100 μg of anti-CD44-IR700 i.v. only; NIR light exposure only; and 100 μg of anti-CD44-IR700 i.v. with NIR light exposure. NIR-PIT therapy, compared with the other groups, significantly inhibited tumor growth and prolonged survival in all three cell model systems. In conclusion, these data reveal that anti-CD44 antibodies are suitable as mAb-photoabsorber conjugates for NIR-PIT in MOC cells.Implications: This study using syngeneic mouse models, which better model the disease in humans than conventional xenografts, suggests that NIR-PIT with anti-CD44-IR700 is a potential candidate for the treatment of OSCC. Mol Cancer Res; 15(12); 1667-77. ©2017 AACR.

Human Antibody Fusion Proteins/Antibody Drug Conjugates in Breast and Ovarian Cancer

Considerable research efforts have been dedicated to understanding ovarian and breast cancer mechanisms, but there has been little progress translating the research into effective clinical applications. Hence, personalized/precision medicine has emerged because of its potential to improve the accuracy of tumor targeting and minimize toxicity to normal tissue. Targeted therapy in both breast and ovarian cancer has focused on antibodies, antibody drug conjugates (ADCs), and very recently the introduction of human antibody fusion proteins. Small molecule inhibitors and monoclonal antibodies (mAbs) are used in conjunction with chemotherapeutic drugs as a form of treatment but problems arise from a board expression of the target antigen in healthy tissues. Also, insufficient tumor penetration due to tight binding affinity and macromolecular size of mAbs compromise the efficacy of these ADCs. A more targeted approach is thus needed, and ADCs were designed to meet this need. However, in ADCs the method of conjugation of drug to antibody is >1, altering the structure of the drug which leads to off-target effects. Random conjugation also causes the drug to affect the pharmokinetics and biodistribution of the antibody and may cause nonspecific binding and internalization. Recombinant therapeutic proteins achieve controlled conjugation reactions and combine cytotoxicity and targeting in one molecule. They can also be engineered to extend half-life, stability and mechanism of action, and offer novel delivery routes. SNAP-tag fusion proteins are an example of a theranostic recombinant protein as they provide a unique antibody format to conjugate a variety of benzyl guanine modified labels, e.g. fluorophores and photosensitizers in a 1:1 stoichiometry. On the one hand, SNAP tag fusions can be used to optically image tumors when conjugated to a fluorophore, and on the other hand the recombinant proteins can induce necrosis/apoptosis in the tumor when conjugated to a photosensitizer upon exposure to a changeable wavelength of light. The dual nature of SNAP-tag fusions as both a diagnostic and therapeutic tool reinforces its significant role in cancer treatment in an era of precision medicine.

Near-Infrared Photoimmunotherapy Targeting Prostate Cancer with Prostate-Specific Membrane Antigen (PSMA) Antibody

Prostate-specific membrane antigen (PSMA) is a membrane protein that is overexpressed manifold in prostate cancer and provides an attractive target for molecular therapy. Near-infrared photoimmunotherapy (NIR-PIT) is a highly selective tumor treatment that employs an antibody-photoabsorber conjugate (APC). Here, we describe the efficacy of NIR-PIT, using a fully human IgG₁ anti-PSMA monoclonal antibody (mAb), conjugated to the photoabsorber, IR700DX, in a PSMA-expressing PC3 prostate cancer cell line. Anti-PSMA-IR700 showed specific binding and cell-specific killing was observed after exposure of the cells to NIR light in vitro In the in vivo study, anti-PSMA-IR700 showed high tumor accumulation and high tumor-background ratio. Tumor-bearing mice were separated into 4 groups: (i) no treatment; (ii) 100 μg of anti-PSMA-IR700 i.v.; (iii) NIR light exposure; (iv) 100 μg of anti-PSMA-IR700 i.v., NIR light exposure was administered. These were performed every week for up to 3 weeks. Tumor growth was significantly inhibited by NIR-PIT treatment compared with the other control groups (P < 0.001), and significantly prolonged survival was achieved (P < 0.0001 vs. other control groups). More than two thirds of tumors were cured with NIR-PIT. In conclusion, the anti-PSMA antibody is suitable as an APC for NIR-PIT. Furthermore, NIR-PIT with the anti-PSMA-IR700 antibody is a promising candidate of the treatment of PSMA-expressing tumors and could be readily translated to humans.Implications: NIR-infrared photoimmunotherapy (NIR-PIT) using a fully human anti-PSMA-IR700 conjugate showed potential therapeutic effects against a PSMA-expressing prostate cancer that is readily translated to humans. Mol Cancer Res; 15(9); 1153-62. ©2017 AACR.

Tyrosine kinase inhibitor induced growth factor receptor upregulation enhances the efficacy of near-infrared targeted photodynamic therapy in esophageal adenocarcinoma cell lines

Esophageal carcinoma (EC) is a global health problem, with disappointing 5-year survival rates of only 15-25%. Near-infrared targeted photodynamic therapy (NIR-tPDT) is a novel strategy in which cancer-targeted phototoxicity is able to selectively treat malignant cells. In this in vitro report we demonstrate the applicability of antibody-based NIR-tPDT in esophageal adenocarcinoma (EAC), using the phototoxic compounds cetuximab-IRDye700DX and trastuzumab-IRDye700DX, targeting respectively epidermal growth factor receptor 1 (EGFR) and 2 (HER2). Furthermore, we demonstrate that NIR-tPDT can be made more effective by tyrosine kinase inhibitor (TKI) induced growth receptor upregulation. Together, these results unveil a novel strategy for non-invasive EAC treatment, and by pretreatment-induced receptor upregulation its future clinical application may be optimized.

Protein Nanocage Mediated Fibroblast-Activation Protein Targeted Photoimmunotherapy To Enhance Cytotoxic T Cell Infiltration and Tumor Control

Carcinoma-associated fibroblasts (CAFs) are found in many types of cancer and play an important role in tumor growth and metastasis. Fibroblast-activation protein (FAP), which is overexpressed on the surface of CAFs, has been proposed as a universal tumor targeting antigen. However, recent studies show that FAP is also expressed on multipotent bone marrow stem cells. A systematic anti-FAP therapy may lead to severe side effects and even death. Hence, there is an urgent need of a therapy that can selectively kill CAFs without causing systemic toxicity. Herein we report a nanoparticle-based photoimmunotherapy (nano-PIT) approach that addresses the need. Specifically, we exploit ferritin, a compact nanoparticle protein cage, as a photosensitizer carrier, and we conjugate to the surface of ferritin a FAP-specific single chain variable fragment (scFv). With photoirradiation, the enabled nano-PIT efficiently eliminates CAFs in tumors but causes little damage to healthy tissues due to the localized nature of the treatment. Interestingly, while not directly killing cancer cells, the nano-PIT caused efficient tumor suppression in tumor-bearing immunocompetent mice. Further investigations found that the nano-PIT led to suppressed C-X-C motif chemokine ligand 12 (CXCL12) secretion and extracellular matrix (ECM) deposition, both of which are regulated by CAFs in untreated tumors and mediate T cell exclusion that prevents physical contact between T cells and cancer cells. By selective killing of CAFs, the nano-PIT reversed the effect, leading to significantly enhanced T cell infiltration, followed by efficient tumor suppression. Our study suggests a new and safe CAF-targeted therapy and a novel strategy to modulate tumor microenvironment (TME) for enhanced immunity against cancer.

Near Infrared Photoimmunotherapy in a Transgenic Mouse Model of Spontaneous Epidermal Growth Factor Receptor (EGFR)-expressing Lung Cancer

Near infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that combines the specificity of antibodies for targeting tumors with the toxicity induced by a sensitive photoabsorber following exposure to NIR light. Most studies of NIR-PIT have been performed in xenograft models of cancer. The purpose of this study was to evaluate the therapeutic effects of NIR-PIT in a transgenic model of spontaneous lung cancer expressing human EGFR (hEGFR-TL). Mice were separated into 3 groups for the following treatments: (1) no treatment (control); (2) 150 μg of photoabsorber, IR700, conjugated to panitumumab, an antibody targeting EGFR [antibody-photoabsorber conjugate (APC)] intravenously (i.v.) only; (3) 150 μg of APC i.v. with NIR light administration. Each treatment was performed every week up to three weeks. MRI was performed 1 day before and 3, 6, 13, 20, 27, and 34 days after first NIR-PIT. The relative volume of lung tumors was calculated from the tumor volume at each MRI time point divided by the initial volume. Steel test for multiple comparisons was used to compare the tumor volume ratio with that of control. Tumor volume ratio was inhibited significantly in the NIR-PIT group compared with control group (P < 0.01 at all time points). In conclusion, NIR-PIT effectively treated a spontaneous lung cancer in a hEGFR-TL transgenic mouse model. MRI successfully monitored the therapeutic effects of NIR-PIT. Mol Cancer Ther; 16(2); 408-14. ©2016 AACR.

Near infrared photoimmunotherapy of B-cell lymphoma

Near infrared photoimmunotherapy (NIR-PIT) is a new, highly-selective cancer theranostics that employs an antibody-photo absorber conjugate (APC). NIR-PIT has successfully treated preclinical tumor models with APCs and is now in the first-in-human phase 1 clinical trial for head and neck cancer patients against EGFR. CD20 is highly expressed in many B-cell lymphomas and is emerging as a molecular target for this disease. Here, we describe the use of the anti-CD20 monoclonal antibody (mAb), rituximab-IR700 APC for NIR-PIT of B-cell lymphoma in two CD20-expressing lymphoma mouse models. CD20 expressing B-cell lymphoma cell lines (Daudi and Ramos) were used in this study. Rituximab-IR700, rituximab conjugated with IRDye700DX, showed specific binding, and cell-specific killing only after exposure of NIR light to both cells in vitro. To evaluate effects of NIR-PIT in vivo, tumor-bearing mice were separated into 4 groups: (1) control; (2) APC i.v. only; (3) NIR light exposure only; (4) APC and NIR light (NIR-PIT). These were performed every week for up to 3 weeks. Rituximab-IR700 showed high tumor accumulation and high target-to-background ratio in vivo. Tumor growth was significantly inhibited by NIR-PIT in comparison with the other groups (p < 0.001 for both tumors), and survival was significantly prolonged in both tumors (p < 0.001 for Daudi tumors and p < 0.0001 for Ramos tumors vs other groups). More than half of tumors were cured with this single regimen of NIR-PIT. In conclusion, anti-CD20 rituximab-IR700 works as a highly effective APC for NIR-PIT against B-cell lymphoma.