Near-Infrared Photoimmunotherapy Using a Protein Mimetic for EGFR-Positive Salivary Gland Cancer.

Near-infrared photoimmunotherapy (NIR-PIT) is a novel cancer therapy based on a monoclonal antibody (mAb) conjugated to a photosensitizer (IR700Dye). The conjugate can be activated by near-infrared light irradiation, causing necrotic cell death with high selectivity. In this study, we investigated NIR-PIT using a small protein mimetic (6-7 kDa, Affibody) which has more rapid clearance and better tissue penetration than mAbs for epidermal growth factor receptor (EGFR)-positive salivary gland cancer (SGC). The level of EGFR expression was examined in vitro using immunocytochemistry and Western blotting. Cell viability was analyzed using the alamarBlue assay. In vivo, the volume of EGFR-positive tumors treated with NIR-PIT using the EGFR Affibody-IR700Dye conjugate was followed for 43 days. It was found that NIR-PIT using the EGFR Affibody-IR700Dye conjugate induced the selective destruction of EGFR-positive SGC cells and restricted the progression of EGFR-positive tumors. We expect that NIR-PIT using the EGFR Affibody-IR700Dye conjugate can efficiently treat EGFR-positive SGC and preserve normal salivary function.

Near-infrared photoimmunotherapy and anti-cancer immunity.

The activation of the anti-cancer immune system is an important strategy to control cancer. A new form of cancer phototherapy, near-infrared photoimmunotherapy (NIR-PIT), was approved for clinical use in 2020 and uses IRDye® 700DX (IR700)-conjugated antibodies and NIR light. After irradiation with NIR light, the antibody-IR700 conjugate forms water-insoluble aggregations on the plasma membrane of target cells. This aggregation causes lethal damage to the plasma membrane, and effectively leads to immunogenic cell death (ICD). Subsequently, ICD activates anti-cancer immune cells such as dendritic cells and cytotoxic T cells. Combination therapy with immune-checkpoint blockade has synergistically improved the anti-cancer effects of NIR-PIT. Additionally, NIR-PIT can eliminate immunosuppressive immune cells in light-irradiated tumors by using specific antibodies against regulatory T cells and myeloid-derived suppressor cells. In addition to cancer-cell-targeted NIR-PIT, such immune-cell-targeted NIR-PIT has shown promising results by activating the anti-cancer immune system. Furthermore, NIR-PIT can be used to manipulate the tumor microenvironment by eliminating only targeted cells in the tumor, and thus it also can be used to gain insight into immunity in basic research.

Review of RM-1929 Near-Infrared Photoimmunotherapy Clinical Efficacy for Unresectable and/or Recurrent Head and Neck Squamous Cell Carcinoma.

Head and neck squamous cell carcinoma (HNSCC) contribute to a significant global cancer burden. Developments in current therapeutic approaches have improved patient outcomes but have limited efficacy in patients with unresectable and/or recurrent HNSCC. RM-1929 near-infrared photoimmunotherapy (NIR-PIT) is an emerging treatment that is currently being investigated in a Phase III clinical trial and has been conditionally approved for the treatment of unresectable and/or recurrent HNSCC in Japan. Here, we collect a series of case reports and clinical trial data to assess the efficacy of RM-1929 NIR-PIT. Disease control rates ranged from 66.7 to 100% across these studies, and overall response rates ranged from 43.3 to 100%, suggesting positive clinical outcomes. Low-grade postoperative localized pain and edema were the most frequently reported side effects, and preliminary reports on quality of life and pain levels suggest that RM-1929 NIR-PIT does not significantly decrease quality of life and is manageable with existing pain management strategies, including opioids. These preliminary data in real-world use of RM-1929 NIR-PIT show that it is a well-tolerated therapy that has clinically meaningful outcomes for patients with unresectable and/or recurrent HNSCC.

Antibody Drug Conjugates of Near-Infrared Photoimmunotherapy (NIR-PIT) in Breast Cancers.

Worldwide, the incidence rate of breast cancer is the highest in women. Approximately 2.3 million people were newly diagnosed and 0.685 million were dead of breast cancer in 2020, which continues to grow. Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype with a higher risk of recurrence and metastasis, but disappointly, there are no effective and specific therapies clinically, especially for patients presenting with metastatic diseases. Therefore, it is urgent to develop a new type of cancer therapy for survival improvisation and adverse effects alleviation of breast cancers. Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed, photochemistry-based cancer therapy. It was drive by an antibody-photoabsorber conjugate (APC) which is triggered by near-infrared light. The key part of APC is a cancer-targeting monoclonal antibody (mAb) that can bind to receptors or antigens on the surface of tumor cells. Because of this targeted conjugate accumulation, subsequent deployment of focal NIR-light results in functional damage on the targeted cell membranes without harming the immediately adjacent receptor-negative cells and evokes a kind of photochemical, speedy, and highly specific immunogenic cell death (ICD) of cancer cells with corresponding antigens. Subsequently, immature dendritic cells adjacent to dying cancer cells will become mature, further inducing a host-oriented anti-cancer immune response, complicatedly and comprehensively. Currently, NIR-PIT has progressed into phase 3 clinical trial for recurrent head and neck cancer. And preclinical studies have illustrated strong therapeutic efficacy of NIR-PIT targeting various molecular receptors overexpressed in breast cancer cells, including EGFR, HER2, CD44c, CD206, ICAM-1 and FAP-α. Thereby, NIR-PIT is in early trials, but appears to be a promising breast cancer therapy and moving into the future. Here, we present the specific advantages and discuss the most recent preclinical studies against several transmembrane proteins of NIR-PIT in breast cancers.

Near-infrared photoimmunotherapy (NIR-PIT) of bone metastases.

The bones are a common site for metastasis arising from solid tumors such as breast and prostate cancer. Chemotherapy, including immunotherapy, is rarely curative. Radiotherapy with pain palliation can temporize bone metastases but is generally considered a short-term solution and retreatment is difficult. Surgery is often necessary, yet recovery times might exceed life expectancy. Therefore, there is a need to develop new approaches to bone metastases that are effective but minimally invasive. Near-infrared photoimmunotherapy (NIR-PIT) uses antibodies labeled with IRDye700DX (IR700) which is activated by NIR light, resulting in rapid cell membrane damage and immunogenic cell death. NIR-PIT using an anti-epidermal growth factor receptor (EGFR) antibody-IR700 conjugate in patients with recurrent head and neck cancer received qualified approval in Japan in 2020 and is now widely used there. However, no bone metastases have yet been treated. In this study, the efficacy of NIR-PIT for bone metastases was investigated using a bone metastases mouse model successfully established by caudal artery injection of a human triple-negative breast cancer cell line, MDAMB468-GFP/luc. The bone metastatic lesions were treated with NIR-PIT using the anti-EGFR antibody, panitumumab-IR700 conjugate. Bioluminescence imaging and histological evaluation showed that EGFR-targeted NIR-PIT has a therapeutic effect on bone metastatic lesions in mice. In addition, micro-CT showed that repeated NIR-PIT led to repair of metastasis-induced bone destruction and restored bone cortex continuity consistent with healing. These data suggest that NIR-PIT has the potential for clinical application in the treatment of bone metastases.

Development of a Monoclonal Antibody Targeting HTLV-1 Envelope gp46 Glycoprotein and Its Application to Near-Infrared Photoimmuno-Antimicrobial Strategy.

Human T-cell leukemia virus type 1 (HTLV-1), a retrovirus, causes adult T-cell leukemia-lymphoma, HTLV-1 associated myelopathy/tropical spastic paraparesis, and HTLV-1 uveitis. Currently, no antiretroviral therapies or vaccines are available for HTLV-1 infection. This study aimed to develop an antibody against the HTLV-1 envelope protein (Env) and apply it to a near-infrared photoimmuno-antimicrobial strategy (NIR-PIAS) to eliminate HTLV-1 infected cells. We established mouse monoclonal antibodies (mAbs) against HTLV-1 Env by immunization with a complex of liposome and the recombinant protein. Detailed epitope mapping revealed that one of the mAbs bound to the proline-rich region of gp46 and exhibited no obvious neutralizing activity to inhibit viral infection. Instead, the mAb was rarely internalized intracellularly and remained on the cell surface of HTLV-1-infected cells. The antibody conjugated to the photosensitive dye IRDye700Dx recognized HTLV-1 infected cells and killed them following NIR irradiation. These results suggest that the novel mAb and NIR-PIAS could be developed as a new targeted therapeutic tool against HTLV-1 infected cells.

Disialoganglioside GD2-Targeted Near-Infrared Photoimmunotherapy (NIR-PIT) in Tumors of Neuroectodermal Origin.

Disialoganglioside (GD2) is a subtype of glycolipids that is highly expressed in tumors of neuroectodermal origins, such as neuroblastoma and osteosarcoma. Its limited expression in normal tissues makes GD2 a potential target for precision therapy. Several anti-GD2 monoclonal antibodies are currently in clinical use and have had moderate success. Near-infrared photoimmunotherapy (NIR-PIT) is a cancer therapy that arms antibodies with IRDye700DX (IR700) and then exposes this antibody-dye conjugate (ADC) to NIR light at a wavelength of 690 nm. NIR light irradiation induces a profound photochemical response in IR700, resulting in protein aggregates that lead to cell membrane damage and death. In this study, we examined the feasibility of GD2-targeted NIR-PIT. Although GD2, like other glycolipids, is only located in the outer leaflet of the cell membrane, the aggregates formation exerted sufficient physical force to disrupt the cell membrane and kill target cells in vitro. In in vivo studies, tumor growth was significantly inhibited after GD2-targeted NIR-PIT, resulting in prolonged survival. Following GD2-targeted NIR-PIT, activation of host immunity was observed. In conclusion, GD2-targeted NIR-PIT was similarly effective to the conventional protein-targeted NIR-PIT. This study demonstrates that membrane glycolipid can be a new target of NIR-PIT.

A low molecular weight multifunctional theranostic molecule for the treatment of prostate cancer.

Rationale: Although surgery and radiation therapy in patients with low risk prostate cancer appear appropriate and effective, those with high-risk localized disease almost always become hormone refractory and then rapidly progress. A new treatment strategy is urgently needed for patients with high-risk localized prostate cancer, particularly an approach that combines two drugs with different mechanisms. Combinations of photodynamic therapy (PDT) and chemotherapy have shown synergistic effects in clinical trials, but are limited by off-target toxicity. Prostate specific membrane antigen (PSMA) is a well-established biomarker for prostate cancer. Here we describe the use of a PSMA ligand to selectively and simultaneously deliver a potent microtubule inhibiting agent, monomethyl auristatin E (MMAE), and a PDT agent, IR700, to prostate cancers. Methods: Using a bifunctional PSMA ligand PSMA-1-Cys-C6-Lys, we created a novel theranostic molecule PSMA-1-MMAE-IR700. The molecule was tested in vitro and in vivo for selectivity and antitumor activity studies. Results: PSMA-1-MMAE-IR700 showed selective and specific uptake in PSMA-positive PC3pip cells, but not in PSMA-negative PC3flu cells both in vitro and in vivo. In in vitro cytotoxicity studies, when exposed to 690 nm light, PSMA-1-MMAE-IR700 demonstrated a synergistic effect leading to greater cytotoxicity for PC3pip cells when compared to PSMA-1-IR700 with light irradiation or PSMA-1-MMAE-IR700 without light irradiation. In vivo antitumor activity studies further showed that PSMA-1-MMAE-IR700 with light irradiation significantly inhibited PC3pip tumor growth and prolonged survival time as compared to mice receiving an equimolar amount of PSMA-1-IR700 with light irradiation or PSMA-1-IR700-MMAE without light irradiation. Conclusion: We have synthesized a new multifunctional theranostic molecule that combines imaging, chemotherapy, and PDT for therapy against PSMA-expressing cancer tissues. This work may provide a new treatment option for advanced prostate cancer.

Triggering anti-GBM immune response with EGFR-mediated photoimmunotherapy.

BACKGROUND: Surgical resection followed by chemo-radiation postpones glioblastoma (GBM) progression and extends patient survival, but these tumours eventually recur. Multimodal treatment plans combining intraoperative techniques that maximise tumour excision with therapies aiming to remodel the immunologically cold GBM microenvironment could improve patients' outcomes. Herein, we report that targeted photoimmunotherapy (PIT) not only helps to define tumour location and margins but additionally promotes activation of anti-GBM T cell response. METHODS: EGFR-specific affibody molecule (ZEGFR:03115) was conjugated to IR700. The response to ZEGFR:03115-IR700-PIT was investigated in vitro and in vivo in GBM cell lines and xenograft model. To determine the tumour-specific immune response post-PIT, a syngeneic GBM model was used. RESULTS: In vitro findings confirmed the ability of ZEGFR:03115-IR700 to produce reactive oxygen species upon light irradiation. ZEGFR:03115-IR700-PIT promoted immunogenic cell death that triggered the release of damage-associated molecular patterns (DAMPs) (calreticulin, ATP, HSP70/90, and HMGB1) into the medium, leading to dendritic cell maturation. In vivo, therapeutic response to light-activated conjugate was observed in brain tumours as early as 1 h post-irradiation. Staining of the brain sections showed reduced cell proliferation, tumour necrosis, and microhaemorrhage within PIT-treated tumours that corroborated MRI T2*w acquisitions. Additionally, enhanced immunological response post-PIT resulted in the attraction and activation of T cells in mice bearing murine GBM brain tumours. CONCLUSIONS: Our data underline the potential of ZEGFR:03115-IR700 to accurately visualise EGFR-positive brain tumours and to destroy tumour cells post-conjugate irradiation turning an immunosuppressive tumour environment into an immune-vulnerable one.

Combination of Near-Infrared Photoimmunotherapy Using Trastuzumab and Small Protein Mimetic for HER2-Positive Breast Cancer.

Near-infrared photoimmunotherapy (NIR-PIT) is a promising cancer therapy based on a monoclonal antibody conjugated to a photosensitizer (IR700Dye) that is activated by near-infrared light irradiation. We previously reported on the use of NIR-PIT with a small protein mimetic, the Affibody molecule (6-7 kDa), instead of a monoclonal antibody. In this study, we investigated a combination of NIR-PIT for HER2-positive breast cancer cells (SK-BR3, MDA-MB361, and JIMT1) with HER2 Affibody-IR700Dye conjugate and trastuzumab-IR700Dye conjugate. HER2 Affibody and trastuzumab target different epitopes of the HER2 protein and do not compete. In vitro, the combination of NIR-PIT using both HER2 Affibody-IR700Dye conjugate and trastuzumab-IR700Dye conjugate induced necrotic cell death of HER2-positive breast cancer cells without damage to HER2-negative breast cancer cells (MCF7). It was more efficient than NIR-PIT using either the HER2 Affibody-IR700Dye conjugate alone or the trastuzumab-IR700Dye conjugate alone. Additionally, this combination of NIR-PIT was significantly effective against HER2 low-expressing cancer cells, trastuzumab-resistant cells (JIMT1), and brain metastatic cells of breast cancer (MDA-MB361). Furthermore, in vivo imaging exhibited the strong fluorescence intensity of both HER2 Affibody-IR700Dye conjugates and trastuzumab-Alexa488 conjugates in HER2-positive tumor, indicating that both HER2 Affibody and trastuzumab specifically bind to HER2-positive tumors without competing with each other. In conclusion, the combination of NIR-PIT using both HER2 Affibody and trastuzumab expands the targeting scope of NIR-PIT for HER2-positive breast cancer.

Phase 1/2a, open-label, multicenter study of RM-1929 photoimmunotherapy in patients with locoregional, recurrent head and neck squamous cell carcinoma.

BACKGROUND: Recurrent head and neck squamous cell carcinoma (rHNSCC) represents a significant global health burden with an unmet medical need. In this study we determined the safety and efficacy of RM-1929 photoimmunotherapy in patients with heavily pretreated rHNSCC. METHODS: RM-1929 (anti-EGFR-IR700 dye conjugate) was infused, followed by tumor illumination. We evaluated safety, tumor response, and pharmacokinetics. RESULTS: Nine patients were enrolled in Part 1 (dose-finding) and 30 patients in Part 2 (safety and efficacy). No dose-limiting toxicities were experienced in Part 1; 640 mg/m2 with fixed light dose (50 J/cm2 or 100 J/cm) was recommended for Part 2. Adverse events (AEs) in Part 2 were mostly mild to moderate but 19 (63.3%) patients had AE ≥Grade 3, including 3 (10.0%) with serious AEs leading to death (not treatment related). Efficacy in Part 2: unconfirmed objective response rate (ORR) 43.3% (95% CI 25.46%-62.57%); confirmed ORR 26.7% (95% CI 12.28%-45.89%); median overall survival 9.30 months (95% CI 5.16-16.92 months). CONCLUSIONS: Treatment was well tolerated. Responses and survival following RM-1929 photoimmunotherapy in heavily pretreated patients with rHNSCC were clinically meaningful and warrant further investigation. CLINICAL TRIAL INFORMATION: NCT02422979.

A phase I, single-center, open-label study of RM-1929 photoimmunotherapy in Japanese patients with recurrent head and neck squamous cell carcinoma.

BACKGROUND: To determine the safety, preliminary efficacy, pharmacokinetics, and immunogenicity of a single cycle of RM-1929 photoimmunotherapy, an anti-EGFR antibody cetuximab conjugated with a light-activatable dye (IRDye®700DX), in Japanese patients with recurrent head and neck squamous cell carcinoma (rHNSCC). METHODS: Patients received a single fixed dose (640 mg/m2) of RM-1929 and a fixed light treatment dose (50 J/cm2 for superficial illumination; 100 J/cm fiber diffuser length for interstitial illumination). Safety, tumor response (modified RECIST v1.1 by central radiology review), pharmacokinetics, and immunogenicity were evaluated. RESULTS: Three Japanese patients were enrolled who had failed ≥ 3 prior lines of therapy including radiation, chemotherapy, cetuximab, and immunotherapy. Target lesions were: submental lesion; right superficial cervical node lesion and oropharynx lesion; and external auditory canal lesion. All patients experienced ≥ 1 treatment-emergent adverse event (TEAE), but none were considered dose-limiting. TEAEs were mild to moderate in severity except for one grade 3 application-site pain, which was transient, resolved without sequelae within 24 h, and did not affect study treatment administration. Thirteen of 17 TEAEs reported were possibly or probably related to study treatment. Three patient reports of application-site pain and localized edema were deemed probably related to study treatment. Objective response was observed in two patients (both partial responses). The third patient had disease progression. RM-1929 concentrations and pharmacokinetic parameters were similar in all patients. No patients tested positive for anti-drug antibodies. CONCLUSIONS: RM-1929 photoimmunotherapy showed a manageable safety profile in rHNSCC. Tumor response in these heavily pre-treated patients was clinically meaningful and warrants further investigation. CLINICAL TRIAL REGISTRATION: The trial was registered with the Japanese registry of clinical trials as jRCT2031200133.

Diagnostic imaging in near-infrared photoimmunotherapy using a commercially available camera for indocyanine green.

Near-infrared photoimmunotherapy (NIR-PIT) is a new type of cancer treatment, which was recently approved in Japan for patients with inoperable head and neck cancer. NIR-PIT utilizes antibody-IRDye700DX (IR700) conjugates and NIR light at a wavelength of 690 nm. NIR light exposure leads to physicochemical changes in the antibody-IR700 conjugate cell receptor complex, inducing rapid necrotic cell death. Just as fluorescence guided surgery is useful for surgeons to resect tumors completely, real-time information of tumor locations would help clinicians irradiate NIR light more precisely. IR700 is a fluorescence dye that emits at 702 nm; however, there is no clinically available device optimized for detecting this fluorescence. On the other hand, many indocyanine green (ICG) fluorescence imaging devices have been approved for clinical use. Therefore, we investigated whether LIGHTVISION, one of the clinically available ICG cameras, could be employed for tumor detection. We hypothesized that irradiation with even low-power 690-nm laser light, attenuated by 99% with a neutral-density filter, could be detected with LIGHTVISION without fluorescence decay or therapeutic effect because of the long emission tail of IR700 beyond 800 nm (within the detection range of LIGHTVISION). We demonstrated that the LIGHTVISION camera, originally designed for ICG detection, can detect the tail of IR700 fluorescence in real time, thus enabling the visualization of target tumors.

Fluorescence Imaging of Tumor-Accumulating Antibody-IR700 Conjugates Prior to Near-Infrared Photoimmunotherapy (NIR-PIT) Using a Commercially Available Camera Designed for Indocyanine Green.

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer treatment that uses antibody-IRDye700DX (IR700) conjugates and was recently approved in Japan for patients with inoperable head and neck cancer. Exposure of the tumor with NIR light at a wavelength of 690 nm leads to physicochemical changes in the antibody-IR700 conjugate-cell receptor complex, resulting in increased hydrophobicity and damage to the integrity of the cell membrane. However, it is important that the tumor be completely exposed to light during NIR-PIT, and thus, a method to provide real-time information on tumor location would help clinicians direct light more accurately. IR700 is a fluorophore that emits at 702 nm; however, there is no clinically available device optimized for detecting this fluorescence. On the other hand, many indocyanine green (ICG) fluorescence imaging devices have been approved for clinical use in operating rooms. Therefore, we investigated whether LIGHTVISION, one of the clinically available ICG cameras, could be employed for NIR-PIT target tumor detection. Due to the limited benefits of adding IR700 molecules, the additional conjugation of IRDye800CW (IR800) or ICG-EG4-Sulfo-OSu (ICG-EG4), which has an overlapping spectrum with ICG, to trastuzumab-IR700 conjugates was performed. Conjugation of second NIR dyes did not interfere the efficacy of NIR-PIT. The dual conjugation of IR800 and IR700 to trastuzumab clearly visualized target tumors with LIGHTVISION by detecting emission light of IR800. We demonstrated that the conjugation of second NIR dyes enables us to provide a real-time feedback of tumor locations prior to NIR-PIT.

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

Background/Aim: Near-infrared photoimmuno-therapy (NIR-PIT) is a newly approved cancer phototherapy. We aim to confirm whether a clinically approved camera for indocyanine green (ICG) could monitor IR700 fluorescence in real time during exposure to therapeutic NIR light. Materials and Methods: An NIR camera, LIGHTVISION, designed to image ICG fluorescence, was used. A431-GFP/luc tumor-bearing mice were exposed to therapeutic NIR light and real-time fluorescence imaging (RT-FI) was obtained and measured with LIGHTVISION. Bioluminescence imaging (BLI) was performed to confirm cell death. Results: RT-FI during NIR-PIT revealed an initial rapid loss of fluorescence, followed by a plateau which occurred at a light dose of approximately 30 J/cm 2 . Correlation between BLI and IR700 fluorescence loss showed that loss of fluorescence was associated with increased cell death. Conclusion: The efficacy of NIR-PIT could be monitored non-invasively and in real-time using weak fluorescence at wavelengths much longer than the peak fluorescence of IR700. This technique can achieve precise light dosimetry that allows us to decide on the optimal exposure.

Regulatory approval of photoimmunotherapy: photodynamic therapy that induces immunogenic cell death.

In September 2020, the Japanese government approved cetuximab saratolacan (previously known as RM-1929, commercial name: Akalux) for the treatment of unresectable locally advanced or recurrent head and neck cancer. Cetuximab saratolacan is a chemical conjugate of the photosensitizer IR700 with cetuximab, which targets EGFR. The treatment consists in the intravenous injection of cetuximab saratolacan, which binds to head and neck cancer cells expressing high levels of EGFR, followed by illumination of the tumor with red light (690 nm) for photodynamic therapy. This approach causes immunogenic cell death in malignant tissues, thus triggering a potent anticancer immune response.

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.

Surface Modification of Liposomes Using IR700 Enables Efficient Controlled Contents Release Triggered by Near-IR Light.

Stimuli-responsive liposomes are promising drug carriers for cancer treatment because they enable controlled drug release and the maintenance of desired drug concentrations in tumor tissue. In particular, near-IR (NIR) light is a useful stimulus for triggering drug release from liposomes based on its advantages such as deep tissue penetration and safety. Previously, we found that a silicon phthalocyanine derivative, IR700, conjugated to antibodies, can induce the rupture of the cell membrane following irradiation by NIR light. Based on this finding, we constructed IR700-modified liposomes (IR700 liposomes) and evaluated their drug release properties triggered by NIR light. IR700 liposomes released substantial amounts of encapsulated calcein following irradiation by NIR light. Drug release was substantially suppressed by the addition of sodium azide, suggesting that liposomal membrane permeabilization was mediated by singlet oxygen generated from IR700. Moreover, calcein release from IR700 liposomes triggered by NIR light was promoted under conditions of deoxygenation and the presence of electron donors. Thus, membrane disruption should be induced by the physical change of IR700 from highly hydrophilic to hydrophobic as we previously described, although singlet oxygen can cause a certain level of membrane disruption under normoxia. We also observed that doxorubicin-encapsulated IR700 liposomes exhibited significant cytotoxic effects against CT-26 murine colon carcinoma cells following NIR light exposure. These results indicate that IR700 liposomes can efficiently release anti-cancer drugs following NIR light irradiation even under hypoxic conditions and, therefore, they would be useful for cancer treatment.

Near-Infrared Photoimmunotherapy Using a Small Protein Mimetic for HER2-Overexpressing Breast Cancer.

Near-infrared photoimmunotherapy (NIR-PIT) is a new and promising cancer therapy based on a monoclonal antibody conjugated to a photosensitizer which is activated by near-infrared light irradiation, causing cell death. We investigated NIR-PIT using a small protein mimetic (6-7 kDa), Affibody molecules, instead of a monoclonal antibody for HER2-overexpressing cancer. Because of its small size, the Affibody has rapid clearance, high imaging contrast, and good tumor penetration. Due to the small size of the Affibodies, which can cross the blood-brain barrier, NIR-PIT using Affibodies has the potential to extend the target cancer of NIR-PIT, including brain metastases. In vitro, NIR-PIT using HER2 Affibody-IR700Dye conjugates induced the selective destruction of HER2-overexpressing breast cancer cells without damage to control cells having low level expression of HER2. HER2-overexpressing cancer cells showed necrotic cell death and their viability maintained at low levels, even 5 days after NIR-PIT. In contrast, treatment with high concentration of HER2 Affibody-IR700Dye conjugate alone or irradiation with high dose of NIR light alone was without effect on cell viability. Affibody and IR700Dye are currently used clinically, and therefore, we would expect the current formulation to be safely and quickly transitioned into clinical trials.

Epidermal growth factor receptor (EGFR) density may not be the only determinant for the efficacy of EGFR-targeted photoimmunotherapy in human head and neck cancer cell lines.

OBJECTIVE: The aim of this study was to investigate the effects of targeted photoimmunotherapy (PIT) in vitro on cell lines with various expression levels of epidermal growth factor receptor (EGFR) using an anti-EGFR targeted conjugate composed of Cetuximab and IR700DX, phthalocyanine dye. MATERIALS AND METHODS: Relative EGFR density and cell binding assay was conducted in three human head & neck cancer cell lines (scc-U2, scc-U8, and OSC19) and one reference cell line A431. After incubation with the conjugate for 1 or 24 hours, cellular uptake and localization were investigated by confocal laser scanning microscopy and quantified by image analysis. Cell survival was determined using the MTS assay and alamarBlue assay after PIT with a 690 nm laser to a dose of 7 J.cm-2 (at 5 mW.cm-2 ). The mode of cell death was examined with flow cytometry using apoptosis/necrosis staining by Annexin V/propidium iodide, together with immunoblots of anti-apoptotic Bcl-2 family proteins Bcl-2 and Bcl-xL. RESULTS: A431 cells had the highest EGFR density followed by OSC19, and then scc-U2 and scc-U8. The conjugates were localized both on the surface and in the cytosol of the cells after 1- and 24-hour incubation. After 24-hour incubation the granular pattern was more pronounced and in a similar pattern of a lysosomal probe, suggesting that the uptake of conjugates by cells was via receptor-mediated endocytosis. The results obtained from the quantitative imaging analysis correlate with the level of EGFR expression. Targeted PIT killed scc-U8 and A431 cells efficiently; while scc-U2 and OSC19 were less sensitive to this treatment, despite having similar EGFR density, uptake and localization pattern. Scc-U2 cells showed less apoptotic cell dealth than in A431 after 24-hour targeted PIT. Immunoblots showed significantly higher expression of anti-apoptotic Bcl-2 and Bcl-xL proteins in scc-U2 cell lines compared to scc-U8. CONCLUSION: Our study suggests that the effectiveness of EGFR targeted PIT is not only dependent upon EGFR density. Intrinsic biological properties of tumor cell lines also play a role in determining the efficacy of targeted PIT. We have shown that in scc-U2 cells this difference may be caused by differences in the apoptopic pathway. Lasers Surg. Med. 50:513-522, 2018. © 2018 Wiley Periodicals, Inc.