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.

Abstract 3206: Host immunity following near infrared photoimmunotherapy is enhanced with PD-1 checkpoint blockade to eradicate established highly antigenic tumors

Near infrared photoimmunotherapy (NIR-PIT) is a newly developed cancer treatment that employs a targeted monoclonal antibody-photo-absorber conjugate (APC). Following antibody localization of the APC to a tumor cell surface antigen, NIR light is used to induce highly selective cytolysis. Extensive pre-clinical evidence demonstrates that NIR-PIT is effective at inducing tumor cell lysis using a number of different antibody-APC conjugates and NIR-PIT targeting EGFR with a cetuximab-APC conjugate has shown promising results in phase 2 clinical evaluation for the treatment of recurrent head and neck squamous cell carcinoma. NIR-PIT induces rapid, necrotic cell death that yields innate immune ligands that activate dendritic cells, consistent with immunogenic cell death. Yet, NIR-PIT treatment of syngeneic tumors in wild-type mice has mostly failed to induce durable regression of established tumors, suggesting the presence of one or more mechanisms of resistance to formation of meaningful anti-tumor immunity. In this study, we hypothesized that NIR-PIT could induce anti-tumor immunity that was being restricted by the PD-1/PD-L1 signaling axis, and that PD-1 could reverse innate immune resistance to induce durable, effective anti-tumor immune responses. Using a CD44-targeting APC, we demonstrated the ability of PD-1 immune checkpoint blockade to significantly enhance antigen-specific anti-tumor immunity induced by NIR-PIT in multiple syngeneic tumor models (MC38, LLC, and MOC1 cancer cell line). 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 appeared to reverse adaptive immune resistance, resulting in both enhanced pre-existing tumor antigen-specific T-cell responses and enhanced de novo T-cell responses induced by NIR-PIT. Enhanced immune responses appeared to correlate 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 anti-tumor immunity. Cured mice resisted 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 highly antigenic syngeneic models of cancer.

Citation Format: Tadanobu Nagaya, Jay Friedman, Yasuhiro Maruoka, Fusa Ogata, Shuhei Okuyama, Paul E. Clavijo, Peter L. Choyke, Clint Allen, Hisataka Kobayashi. Host immunity following near infrared photoimmunotherapy is enhanced with PD-1 checkpoint blockade to eradicate established highly antigenic tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3206.

High-fidelity detection and sorting of nanoscale vesicles in viral disease and cancer

Biological nanoparticles, including viruses and extracellular vesicles (EVs), are of interest to many fields of medicine as biomarkers and mediators of or treatments for disease. However, exosomes and small viruses fall below the detection limits of conventional flow cytometers due to the overlap of particle-associated scattered light signals with the detection of background instrument noise from diffusely scattered light. To identify, sort, and study distinct subsets of EVs and other nanoparticles, as individual particles, we developed nanoscale Fluorescence Analysis and Cytometric Sorting (nanoFACS) methods to maximise information and material that can be obtained with high speed, high resolution flow cytometers. This nanoFACS method requires analysis of the instrument background noise (herein defined as the “reference noise”). With these methods, we demonstrate detection of tumour cell-derived EVs with specific tumour antigens using both fluorescence and scattered light parameters. We further validated the performance of nanoFACS by sorting two distinct HIV strains to >95% purity and confirmed the viability (infectivity) and molecular specificity (specific cell tropism) of biological nanomaterials sorted with nanoFACS. This nanoFACS method provides a unique way to analyse and sort functional EV- and viral-subsets with preservation of vesicular structure, surface protein specificity and RNA cargo activity.

Photoimmunotherapy for cancer-associated fibroblasts targeting fibroblast activation protein in human esophageal squamous cell carcinoma

Cancer-associated fibroblasts (CAFs) are strongly implicated in tumor progression, including in the processes of tumorigenesis, invasion, and metastasis. The targeting of CAFs using various therapeutic approaches is a novel treatment strategy; however, the efficacy of such therapies remains limited. Recently, near-infrared photoimmunotherapy (NIR-PIT), which is a novel targeted therapy employing a cell-specific mAb conjugated to a photosensitizer, has been introduced as a new type of phototherapy. In this study, we have developed a novel NIR-PIT technique to target CAFs, by focusing on fibroblast activation protein (FAP), and we evaluate the treatment efficacy in vitro and in vivo. Esophageal carcinoma cells exhibited enhanced activation of fibroblasts, with FAP over-expressed in the cytoplasm and on the cell surface. FAP-IR700-mediated PIT showed induced rapid cell death specifically for those cells in vitro and in vivo, without adverse effects. This novel therapy for CAFs, designed as local control phototherapy, was safe and showed a promising inhibitory effect on FAP⁺ CAFs. PIT targeting CAFs via the specific marker FAP may be a therapeutic option for CAFs in the tumor microenvironment in the future.

Nosocomial infection by human bocavirus and human rhinovirus among paediatric patients with respiratory risks

BACKGROUND

Nosocomial infections by respiratory viruses undetected by rapid tests are not often diagnosed. For paediatric patients with background diseases, nosocomial infection could be fatal.

AIM

To determine the relationship between developing symptoms by respiratory viruses undetectable by rapid tests and respiratory risks and to improve the management of infection control.

METHODS

Two episodes of nosocomial infection by human bocavirus (HBoV) and human rhinovirus (HRV) were retrospectively investigated in a tertiary hospital paediatric ward in Japan. Viruses were identified by polymerase chain reaction to determine infection control management. When viruses of the same species were detected from different patients, the virus homology was investigated. The relationship between respiratory risks and developing symptoms was statistically investigated.

FINDINGS

Three and four patients with respiratory risks in the HBoV and HRV outbreaks, respectively, developed respiratory symptoms. The nucleotide sequences of two patients in the HBoV outbreak and all four patients in the HRV outbreak were phylogenetically close. In both outbreaks, the patients with respiratory risks developed significantly more symptoms than those without any risk (P = 0.035 and 0.018, respectively). After the patients with respiratory infection were separated from those with respiratory risks, no additional nosocomial infection occurred.

CONCLUSION

Patients with respiratory risks easily develop respiratory symptoms and acquire severe symptoms of nosocomial infection by those viruses. In a paediatric ward, we should adopt not only standard precautions but also isolation management of the patients with respiratory symptoms, even if they have negative results in rapid tests.

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.

Targeting Epidermal Growth Factor Receptor (EGFR) and Human Epidermal Growth Factor Receptor 2 (HER2) Expressing Bladder Cancer Using Combination Photoimmunotherapy (PIT)

Bladder cancer (BC) is heterogeneous and expresses various cell surface targets. Photoimmunotherapy (PIT) involves monoclonal antibodies (MAbs) conjugated to a photoabsorber (PA), IR Dye 700Dx, and then activated by near infra-red light (NIR) to specifically target tumors. We have demonstrated that tumors expressing EGFR can be targeted with PIT. However, PIT may be less effective when a tumor lacks "overwhelming" expression of a single target such as EGFR. We present a combinatorial PIT approach for targeting BC expressing EGFR and HER2, using PA- labeled panitumumab (pan) and trastuzumab (tra), respectively. Human BC tissues and cell lines were analyzed for EGFR and HER2 expression. Efficacy of PA-labeled MAbs singly and in combination was analyzed. About 45% of BC tissues stain for both EGFR and HER2. In vitro, the combination of pan IR700 and tra IR700 with NIR was more efficacious than either agent alone. Tumor xenografts treated with combination PIT showed significant tumor growth retardation. Combination PIT is a promising approach for treating BC with low/moderate expression of surface receptors. In addition, given the molecular heterogeneity of bladder cancer, targeting more than one surface receptor may allow for more effective cell death across different bladder tumors.

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.

[Near Infrared Photoimmunotherapy for Cancer]

Near infrared photoimmunotherapy(NIR-PIT)is a new molecularly-targeted cancer photo-therapy based on conjugating a near infrared silica-phthalocyanine dye, IRDye700DX(IR700), to a monoclonal antibody(mAb)targeting cell-surface molecules. NIR-PIT targetingEGFR usingthe cetuximab-IR700 conjugate is now in transition to fast-track global Phase Ⅲ clinical trial in late-stage head and neck squamous cell cancer patients. When exposed to NIR light, the conjugate induces a highlyselective necrotic/immunogenic cell death(ICD)only in target-positive, mAb-IR700-bound cancer cells. This cell death occurs as early as 1 minute after exposure to NIR light. Meanwhile, immediately adjacent target-negative cells are unharmed. ICD induced by NIR-PIT promoted maturation of immature dendritic cells(DCs)to maturated DCs that primed cytotoxic Tcells to react with cancer-related antigens released from destroyed cancer cells. Inhibition of immuno-checkpoints including PD-1/PD-L1 axis or CTLA-4 is one of several major methods for enhancingcytotoxicity of tumor-infiltratingT -cells. In this section, I will also discuss NIR-PIT combined with an immuno-checkpoint inhibitor that could treat not only local tumors but also distant untreated metastatic tumors without recurrence in some syngeneic cancer models. Additionally, NIR-PIT to a local tumor combined with local tumor-infiltratingneg ative-regulatory T-cells by CD25-targeted NIR-PIT that is another major methods for enhancingcytotoxicity of tumor-infiltratingT -cells similarly operated in different tumor models. The regimens of NIR-PIT combined with methods for enhancinghost tumor immunity could cure primary and metastatic tumor and yield vaccination effect against treated cancer cells that would be the ultimate form of NIR-PIT in oncology clinic.

Activatable Near-Infrared Fluorescence Imaging Using PEGylated Bacteriochlorin-Based Chlorin and BODIPY-Dyads as Probes for Detecting Cancer

Near infrared (NIR) fluorescent probes are attractive tools for biomedical in vivo imaging due to the relatively deeper tissue penetration and lower background autofluorescence. Activatable probes are turned on only after binding to their target, further improving target to background ratios. However, the number of available activatable NIR probes is limited. In this study, we introduce two types of activatable NIR fluorophores derived from bacteriochlorin: chlorin-bacteriochlorin energy-transfer dyads and boron-dipyrromethene (BODIPY)-bacteriochlorin energy-transfer dyads. These fluorophores are characterized by multiple narrow excitation bands with relatively strong emission in the NIR. Targeted bacteriochlorin-based antibody or peptide probes have been previously limited by aggregation after conjugation. Polyethylene glycol (PEG) chains were added to improve the hydrophilicity without altering pharmacokinetics of the targeting moieties. These PEGylated bacteriochlorin-based activatable fluorophores have potential as targeted activatable, multicolor NIR fluorescent probes for in vivo applications.

Photoinduced Ligand Release from a Silicon Phthalocyanine Dye Conjugated with Monoclonal Antibodies: A Mechanism of Cancer Cell Cytotoxicity after Near-Infrared Photoimmunotherapy

Photochemical reactions can dramatically alter physical characteristics of reacted molecules. In this study, we demonstrate that near-infrared (NIR) light induces an axial ligand-releasing reaction, which dramatically alters hydrophilicity of a silicon phthalocyanine derivative (IR700) dye leading to a change in the shape of the conjugate and its propensity to aggregate in aqueous solution. This photochemical reaction is proposed as a major mechanism of cell death induced by NIR photoimmunotherapy (NIR-PIT), which was recently developed as a molecularly targeted cancer therapy. Once the antibody-IR700 conjugate is bound to its target, activation by NIR light causes physical changes in the shape of antibody antigen complexes that are thought to induce physical stress within the cellular membrane leading to increases in transmembrane water flow that eventually lead to cell bursting and necrotic cell death.

Pitfalls on sample preparation for ex vivo imaging of resected cancer tissue using enzyme-activatable fluorescent probes

In vivo and ex vivo fluorescence imaging-assisted surgery can aid in determining the margins of tumors during surgical resection. While a variety of fluorescent probes have been proposed for this task, small molecule enzyme-activatable fluorescent probes are ideal for this application. They are quickly activated at tumor sites and result in bright signal with little background, resulting in high sensitivity. Testing in resected specimens, however, can be difficult. Enzymes are usually stable after freezing and thawing but catalytic reactions are generally temperature-dependent. Therefore, tissue sample temperature should be carefully considered. In this study two enzyme activatable probes, γ-glutamylhydroxymethyl rhodamine green (gGlu-HMRG) that reacted with γ-glutamyltransferase and SPiDER-βGal that reacted with β-galactosidase, were employed to determine the effects of temperature on fluorescence signal kinetics in both fresh and frozen and then thawed ex vivo experimental ovarian cancer tissue samples. The results suggest γ-glutamyltransferase was less sensitive to temperature than β-galactosidase. Fresh samples showed higher fluorescence signals of gGlu-HMRG compared with thawed samples likely because the freeze-thaw cycle decreased the rate of internalization of the activated probe into the lysosome. In contrast, no significant difference of SPiDER-βGal fluorescence signal was observed between fresh and frozen tissues. In conclusion, although imaging of fresh samples at 37°C is the best condition for both probes, successful imaging with gGlu-HMRG could be achieved even at room temperature with thawed samples. We demonstrate that temperature regulation and tissue handling of resected tissue are two pitfalls that may influence ex vivo imaging signals with enzyme-activatable fluorescent probes.

Cross-Sectional Inverse Association of Regular Soy Intake with Insulin Resistance in Japanese Elderly

Levels of isoflavones, biomarkers of soy intake, in 24-hour urine (24U) were inversely related to coronary heart disease (CHD) mortality in the World Health Organization's Cardiovascular Disease and Alimentary Comparison Study. Considering 24 U isoflavone levels were highest and CHD mortality was lowest in the Japanese, who maintained the world's longest life expectancy, the association of regular soy intake with cardiometabolic risk was investigated in Japanese adults (20-49 years old) and elderly (50-79 years old). In multivariate analysis adjusted for age, sex, and drug treatments, mean 24 U isoflavone excretion was significantly inversely associated with insulin resistance in the elderly and significantly associated with blood folate and potassium in the elderly, but also positively associated with 24 U salt in the elderly. These findings indicate that low-salt soy should be recommended to improve glucose metabolism in elderly Japanese.

Immunohistochemical Analysis of Human Lung Cancers with Anti-ras p21 Monoclonal Antibodies

The expression of ras oncogene product p21 in human malignant pleurisy and primary lung cancer was studied immunocyto-histochemically with monoclonal antibodies (MoAbs) rp-28 and rp-35 against ras p21. In pleural effusion cells, cancer cells revealed more intensively positive reaction with MoAb rp-35 than with MoAb rp-28, especially in the plasma membrane, and no positive reaction was obtained in any kind of inflammation cells with the exception of faintly positive reaction in the cytoplasm of macrophages.

In primary lung cancers, well or moderately differentiated adenocarcinoma tissues showed higher reactivity with MoAb rp-28 than those of poorly differentiated adenocarcinoma or any other histological subtype of lung cancer. With MoAb rp-35, intensively positive reaction was obtained in most of cases with all different histological subtypes of lung cancer. The staining in cancer cells was usually localized intensively to the plasma membrane and weakly to the cytoplasm with both MoAbs. Normal bronchial epithelial and glandular tissues showed only cytoplasmic staining. These two MoAbs, especially MoAb rp-35, may be useful in clinicopathological applications for the diagnosis of malignant pleurisy and primary lung cancer.