In vivo imaging using fluorescent antibodies to tumor necrosis factor predicts therapeutic response in Crohn's disease

How will new and future therapies change our treatment of IBD?

Fundamental insights into the pathogenesis of inflammatory bowel diseases (IBD) have led to the development of new therapies and lots of experimental compounds in the pipeline. Our treatment of IBD is therefore constantly evolving. In this editorial, we postulate that bi- or even polyspecific therapy will be an important mainstay of future IBD treatment. Moreover, we highlight some promising new therapeutic concepts currently under investigation and point at the outstanding and growing importance of personalized medicine to assign drugs from the increasing pool of options to the individual patient.

Emerging optical methods for surveillance of Barrett's oesophagus

The rapid rise in incidence of oesophageal adenocarcinoma has motivated the need for improved methods for surveillance of Barrett's oesophagus. Early neoplasia is flat in morphology and patchy in distribution and is difficult to detect with conventional white light endoscopy (WLE). Light offers numerous advantages for rapidly visualising the oesophagus, and advanced optical methods are being developed for wide-field and cross-sectional imaging to guide tissue biopsy and stage early neoplasia, respectively. We review key features of these promising methods and address their potential to improve detection of Barrett's neoplasia. The clinical performance of key advanced imaging technologies is reviewed, including (1) wide-field methods, such as high-definition WLE, chromoendoscopy, narrow-band imaging, autofluorescence and trimodal imaging and (2) cross-sectional techniques, such as optical coherence tomography, optical frequency domain imaging and confocal laser endomicroscopy. Some of these instruments are being adapted for molecular imaging to detect specific biological targets that are overexpressed in Barrett's neoplasia. Gene expression profiles are being used to identify early targets that appear before morphological changes can be visualised with white light. These targets are detected in vivo using exogenous probes, such as lectins, peptides, antibodies, affibodies and activatable enzymes that are labelled with fluorescence dyes to produce high contrast images. This emerging approach has potential to provide a 'red flag' to identify regions of premalignant mucosa, outline disease margins and guide therapy based on the underlying molecular mechanisms of cancer progression.

From the surface to the single cell: Novel endoscopic approaches in inflammatory bowel disease

Inflammatory bowel diseases (IBD) comprise the two major entities Crohn’s disease and ulcerative colitis and endoscopic imaging of the gastrointestinal tract has always been an integral and central part in the management of IBD patients. Within the recent years, mucosal healing emerged as a key treatment goal in IBD that substantially decides about the clinical outcome of IBD patients, thereby demanding for a precise, timely and detailed endoscopic assessment of the mucosal inflammation associated with IBD. Further, molecular imaging has tremendously expanded the clinical utility and applications of modern endoscopy, now encompassing not only diagnosis, surveillance, and treatment but also the prediction of individual therapy response. Within this review we describe novel endoscopic approaches and advanced endoscopic imaging methods for the diagnosis, treatment and surveillance of IBD patients. We begin by providing an overview over novel and advanced imaging techniques such as magnification endoscopy and dye-based and dye-less chromoendoscopy, endomicroscopy and endocytoscopy. We then describe how these techniques can be utilized for the precise and ultrastructural assessment of mucosal inflammation and dysplasia development associated with IBD and outline how they have enabled the endoscopist to gain insight onto the cellular level in real-time. Finally, we provide an outlook on how molecular imaging has rapidly evolved in the recent past and can be used to make individual predictions about the therapeutic response towards biological treatment.

Response to peripheral immune stimulation within the brain: magnetic resonance imaging perspective of treatment success

Chronic peripheral inflammation in diseases such as rheumatoid arthritis leads to alterations in central pain processing and consequently to mood disorders resulting from sensitization within the central nervous system and enhanced vulnerability of the medial pain pathway. Proinflammatory cytokines such as tumor necrosis factor (TNF) alpha play an important role herein, and therapies targeting their signaling (i.e., anti-TNF therapies) have been proven to achieve good results. However, the phenomenon of rapid improvement in the patients’ subjective feeling after the start of TNFα neutralization remained confusing, because it was observed long before any detectable signs of inflammation decline. Functional magnetic resonance imaging (fMRI), enabling visualization of brain activity upon peripheral immune stimulation with anti-TNF, has helped to clarify this discrepancy. Moreover, fMRI appeared to work as a reliable tool for predicting prospective success of anti-TNF therapy, which is valuable considering the side effects of the drugs and the high therapy costs. This review, which is mainly guided by neuroimaging studies of the brain, summarizes the state-of-the-art knowledge about communication between the immune system and the brain and its impact on subjective well-being, addresses in more detail the outcome of the abovementioned anti-TNF fMRI studies (rapid response to TNFα blockade within the brain pain matrix and differences in brain activation patterns between prospective therapy responders and nonresponders), and discusses possible mechanisms for the latter phenomena and the predictive power of fMRI.

In vivo imaging with antibodies and engineered fragments

Antibodies have clearly demonstrated their utility as therapeutics, providing highly selective and effective drugs to treat diseases in oncology, hematology, cardiology, immunology and autoimmunity, and infectious diseases. More recently, a pressing need for equally specific and targeted imaging agents for assessing disease in vivo, in preclinical models and patients, has emerged. This review summarizes strategies for developing and optimizing antibodies as targeted probes for use in non-invasive imaging using radioactive, optical, magnetic resonance, and ultrasound approaches. Recent advances in engineered antibody fragments and scaffolds, conjugation and labeling methods, and multimodality probes are highlighted. Importantly, antibody-based imaging probes are seeing new applications in detection and quantitation of cell surface biomarkers, imaging specific responses to targeted therapies, and monitoring immune responses in oncology and other diseases. Antibody-based imaging will provide essential tools to facilitate the transition to truly precision medicine.

In-vivo microscopy in the diagnosis of intestinal neoplasia and inflammatory conditions

Confocal laser endomicroscopy (CLE) is a rapidly emerging tool in endoscopic imaging allowing in-vivo microscopy of examined gastrointestinal mucosa. This review will discuss the most recent advances of confocal laser endomicroscopy in the diagnosis of intestinal neoplasia and inflammatory conditions.

[Novel endoscopic techniques to image the upper gastrointestinal tract]

Novel endoscopic techniques for the analysis of the digestive wall have recently been developed to allow investigating digestive diseases beyond standard "white-light" macroscopic imaging of the mucosal surface. Among innovative techniques under clinical evaluation, confocal endomicroscopy and optical frequency domain imaging (OFDI) are the most promising. Indeed, these techniques allow performing in vivo microscopy with different levels in terms of depths and magnification, as well as functional assessment of structures. Some of these techniques, such as capsule-based OFDI, are also less invasive than traditional endoscopy and might help screening large groups of patients for specific disorders, for instance oesophageal precancerous diseases. In this review, we will focus on the results obtained with these techniques in precancerous, inflammatory and neuromuscular disorders.

Endomicroscopy Will Track Injected Mesenchymal Stem Cells in Rat Colitis Models

BACKGROUND

Mesenchymal stem cells (MSCs) have demonstrated significant potentials for the treatment of inflammatory bowel disease. Clinical feasible methods to individually document the MSC recruitment to intestinal mucosa is lacking. Here, we proposed that endomicroscopy could noninvasively track MSCs in vivo at cellular resolution.

METHOD

Isolated Sprague Dawley rat MSC was characterized, fluorescently labeled, and imaged ex vivo using an endomicroscope. Then enhanced green fluorescent protein (eGFP)-labeled MSC was tracked in vivo, and acquired images were compared with immunofluorescence, immunohistology, and fluorescent in situ hybridization results.

RESULTS

Endomicroscopy visualized clearly the eGFP-labeled or carboxyfluorescein succinimidyl ester-stained MSC ex vivo. Endomicroscopy using the FIVE1 system could track eGFP-labeled MSC with distinct in vivo features. Immunofluorescence, immunohistochemistry, and fluorescent in situ hybridization confirmed the presence of eGFP-positive cells. In vivo endomicroscopy could quantify the transplanted MSCs that homed to colonic mucosa of the recipient rat in multiple models, including the rat-to-rat allograft, human-to-rat xenograft, hypoxia-induced MSC, and busulfan immunosuppressed recipient rat models. After hypoxia induction, there was a trend of enhanced rat MSC homing to the inflamed mucosa as visualized by endomicroscopy (114.1 in hypoxia group versus 34.3 in other 3 groups combined, t = 2.14, P = 0.0644).

CONCLUSIONS

Endomicroscopy is a novel and promising tool to track transplanted MSCs to the colonic mucosa. This clinical available noninvasive cellular tracking method may provide new insight to individualize each recipient's regimen in the future.

In vitro response pattern of monocytes after tmTNF reverse signaling predicts response to anti-TNF therapy in rheumatoid arthritis

Background

Treatment with TNF inhibitors is very efficient in the majority of the patients with rheumatoid arthritis (RA), but it does not achieve a sufficient treatment response in 40–50% of the cases. Goal of the study was to assess functional ex vivo-tests of RA monocytes as prognostic parameters of the subsequent treatment response.

Methods

20 anti-TNF naïve RA patients were enrolled in a prospective, open-label trial, and Etanercept therapy was initiated. Prior to treatment, reverse signaling was induced in peripheral blood monocytes by tmTNF crosslinking via TNFR2:Ig construct Etanercept in a standardized ex vivo-assay. Released cytokine and cytokine receptor concentrations were determined as parameters of the monocyte response.

Results

Crosslinking of tmTNF and consecutive reverse signaling led to production of pro- and anti-inflammatory cytokines and of soluble cytokine decoy receptors such as sTNFR1 and sIL-1R2. Several of the measured concentrations were found to correlate with the treatment response according to the EULAR criteria. The correlation was most pronounced in sTNFR1 concentrations (r = −0.657, p = 0.0031), which also predicted a good clinical response with the highest sensitivity and specificity according to EULAR criteria.

Conclusions

Herein we propose that the tmTNF crosslinking-triggered shedding of soluble decoy receptors and production of anti-inflammatory cytokines could contribute to the clinical efficacy of TNF inhibitors, and that in vitro quantification of this secretion by RA monocytes prior to treatment can be used to predict the clinical response. Further development of such standardized tests could be a step towards personalized medicine by providing rheumatologists with a rational choice for first line biological therapy in patients with RA.

Loss of Infliximab Into Feces Is Associated With Lack of Response to Therapy in Patients With Severe Ulcerative Colitis

BACKGROUND & AIMS

It is not clear why some patients with ulcerative colitis (UC) do not respond to treatment with anti-tumor necrosis factor (TNF) agents, such as infliximab. It could be that some patients have high level of inflammation, with large quantities of TNF to be neutralized by the drug. We investigated whether loss of anti-TNF agents through ulcerated intestinal mucosa reduces the efficacy of these drugs in patients with severe UC.

METHODS

We collected fecal samples from 30 consecutive patients with moderate to severely active UC during the first 2 weeks of infliximab therapy at the University of Amsterdam hospital. Infliximab concentrations were measured in serum and supernatants of fecal samples using an enzyme-linked immunosorbent assay (Sanquin Biologicals Laboratory, Amsterdam, The Netherlands). Clinical and endoscopic responses were assessed 2 and 8 weeks and 3 months after treatment began.

RESULTS

Infliximab was detected in 129 of 195 fecal samples (66%); the highest concentrations were measured in the first days after the first infusion. Patients that were clinical nonresponders at week 2 had significantly higher fecal concentrations of infliximab after the first day of treatment than patients with clinical responses (median concentration, 5.01 μg/mL in nonresponders vs 0.54 μg/mL in responders; P = .0047). We did not observe a correlation between fecal and serum concentrations of infliximab.

CONCLUSIONS

Infliximab is lost into stools of patients with UC. High fecal concentrations of infliximab in the first days after therapy begins are associated with primary nonresponse. Additional studies are needed to determine how therapeutic antibodies are lost through the intestinal mucosa and how this process affects treatment response. Clinical trial ID: NL41310.018.12.

Characterization of lesions in the stomach: will confocal laser endomicroscopy replace the pathologist?

Confocal laser endomicroscopy (CLE) permits microscopic visualization of the mucosa during endoscopy at an approximately 1000fold magnification, permitting endoscopists to obtain microscopic analysis during gastroscopy. This can result in optimized diagnosis of diffuse alterations such as gastric atrophy and intestinal metaplasia and may limit the sampling error of untargeted biopsies. It also allows risk stratification prior to endoscopic therapy of neoplastic lesions of the stomach. In these areas, CLE represents a valuable adjunct for targeted histopathology. In addition, CLE allows on-site in vivo imaging, and by this insight into physiologic and pathophysiologic as well as molecular events of the stomach without major artifacts.

Smart imaging of acute lung injury: exploration of myeloperoxidase activity using in vivo endoscopic confocal fluorescence microscopy

The pathophysiology of acute lung injury (ALI) is well characterized, but its real-time assessment at bedside remains a challenge. When patients do not improve after 1 wk despite supportive therapies, physicians have to consider open lung biopsy (OLB) to identify the process(es) at play. Sustained inflammation and inadequate repair are often observed in this context. OLB is neither easy to perform in a critical setting nor exempt from complications. Herein, we explore intravital endoscopic confocal fluorescence microscopy (ECFM) of the lung in vivo combined with the use of fluorescent smart probe(s) activated by myeloperoxidase (MPO). MPO is a granular enzyme expressed by polymorphonuclear neutrophils (PMNs) and alveolar macrophages (AMs), catalyzing the synthesis of hypoclorous acid, a by-product of hydrogen peroxide. Activation of these probes was first validated in vitro in relevant cells (i.e., AMs and PMNs) and on MPO-non-expressing cells (as negative controls) and then tested in vivo using three rat models of ALI and real-time intravital imaging with ECFM. Semiquantitative image analyses revealed that in vivo probe-related cellular/background fluorescence was associated with corresponding enhanced lung enzymatic activity and was partly prevented by specific MPO inhibition. Additional ex vivo phenotyping was performed, confirming that fluorescent cells were neutrophil elastase(+) (PMNs) or CD68(+) (AMs). This work is a first step toward "virtual biopsy" of ALI without OLB.

MMP-13 In-Vivo Molecular Imaging Reveals Early Expression in Lung Adenocarcinoma

Introduction

Several matrix metalloproteinases (MMPs) are overexpressed in lung cancer and may serve as potential targets for the development of bioactivable probes for molecular imaging.

Objective

To characterize and monitor the activity of MMPs during the progression of lung adenocarcinoma.

Methods

K-ras^LSL-G12D mice were imaged serially during the development of adenocarcinomas using fluorescence molecular tomography (FMT) and a probe specific for MMP-2, -3, -9 and -13. Lung tumors were identified using FMT and MRI co-registration, and the probe concentration in each tumor was assessed at each time-point. The expression of Mmp2, -3, -9, -13 was quantified by qRT-PCR using RNA isolated from microdissected tumor cells. Immunohistochemical staining of overexpressed MMPs in animals was assessed on human lung tumors.

Results

In mice, 7 adenomas and 5 adenocarcinomas showed an increase in fluorescent signal on successive FMT scans, starting between weeks 4 and 8. qRT-PCR assays revealed significant overexpression of only Mmp-13 in mice lung tumors. In human tumors, a high MMP-13 immunostaining index was found in tumor cells from invasive lesions (24/27), but in none of the non-invasive (0/4) (p=0.001).

Conclusion

MMP-13 is detected in early pulmonary invasive adenocarcinomas and may be a potential target for molecular imaging of lung cancer.

Use of probe-based confocal laser endomicroscopy (pCLE) in gastrointestinal applications. A consensus report based on clinical evidence

BACKGROUND

Probe-based confocal laser endomicroscopy (pCLE) provides microscopic imaging during an endoscopic procedure. Its introduction as a standard modality in gastroenterology has brought significant progress in management strategies, affecting many aspects of clinical care and requiring standardisation of practice and training.

OBJECTIVE

This study aimed to provide guidance on the standardisation of its practice and training in Barrett's oesophagus, biliary strictures, colorectal lesions and inflammatory bowel diseases.

METHODS

Initial statements were developed by five group leaders, based on the available clinical evidence. These statements were then voted and edited by the 26 participants, using a modified Delphi approach. After two rounds of votes, statements were validated if the threshold of agreement was higher than 75%.

RESULTS

Twenty-six experts participated and, among a total of 77 statements, 61 were adopted (79%) and 16 were rejected (21%). The adoption of each statement was justified by the grade of evidence.

CONCLUSION

pCLE should be used to enhance the diagnostic arsenal in the evaluation of these indications, by providing microscopic information which improves the diagnostic performance of the physician. In order actually to implement this technology in the clinical routine, and to ensure good practice, standardised initial and continuing institutional training programmes should be established.

Endomicroscopy with Fluorescent CD105 Antibodies for "In Vivo" Imaging of Colorectal Cancer Angiogenesis

The aim of this case report was to evaluate the feasibility of in vivo acquisition of microscopic images using fluorescent CD105 antibodies for molecular imaging in human colorectal cancer. After excluding the presence of tissue autofluorescence, the antibody solution was topically administered through a spray-catheter. The targeted area was analyzed by eCLE and images were recorded. The fractal dimension of tumor vessels and the vessel density were determined using ImageJ software. Immunohistochemistry was used as a gold standard. In vivo CLE analysis of CD105 expression enabled the study of tumor vascular network, revealing a chaotic structure.

Cultured blood T-cell responses predict anti-TNF therapy response in patients with ulcerative colitis

BACKGROUND

Anti-tumour necrosis factor (TNF) therapy is used for treatment of ulcerative colitis (UC). As approximately 30% of patients with UC do not benefit from the treatment, it is of clinical interest to identify biomarkers of response before therapy is initiated.

AIM

To identify prognostic biomarkers of anti-TNF therapy response in anti-TNF therapy-naïve patients with UC.

METHODS

Peripheral blood cells were obtained from 56 patients with UC before therapy started. Thirty-four patients were included in an exploratory cohort and 22 patients in a validation cohort. Blood cells were stimulated in vitro with influenza vaccine with and without anti-TNF. T-cell surface receptor expression and cytokine release were determined (in total 17 variables). Treatment response was evaluated using the Mayo score 12-14 weeks after the first infusion.

RESULTS

In the exploratory cohort, blood cells from the patients showed stronger anti-TNF-dependent suppression of T-cell surface receptor expression and cytokine secretion among therapy responders than nonresponders. In particular, anti-TNF suppressed the expression of CD25 on T cells and secretion of interleukin 5, to a higher degree in responders than in nonresponders. These variables were used to a create model to predict therapy outcome, which was confirmed in the validation cohort. Correct classification of future therapy response was achieved in 91% of the cases in the validation cohort.

CONCLUSION

The effects of anti-TNF on cultured blood T cells, obtained before therapy started, predict treatment outcome in patients with UC.

Advances in imaging to allow personalized medicine in Crohn's disease

Crohn's disease is a destructive inflammatory bowel disease of unknown origin that may lead to various complications such as strictures, stenosis, fistulas and colitis-associated neoplasias. However, the course of the disease varies substantially among patients and disease behaviour may also change with time. At diagnosis behaviour is inflammatory in the majority of patients, while penetrating or structuring behaviour become more prominent at later time points. Thus, medication in Crohn's disease needs frequent optimization over time. Therefore, new strategies for prediction of response to therapy are urgently needed. Here, recent advantages in imaging techniques for personalized medicine in Crohn's disease are reviewed. Such advantages include ultrasonography, computed tomography, magnetic resonance imaging and new endoscopic approaches such as molecular endoscopy. It is expected that these novel techniques will lead to marked improvements in the assessment of disease behaviour and the prediction of response to clinical therapy with biologicals.

Death-associated protein kinase: A molecule with functional antagonistic duality and a potential role in inflammatory bowel disease (Review)

The cytoskeleton-associated serine/threonine kinase death-associated protein kinase (DAPK) has been described as a cancer gene chameleon with functional antagonistic duality in a cell type and context specific manner. The broad range of interaction partners and substrates link DAPK to inflammatory processes especially in the gut. Herein we summarize our knowledge on the role of DAPK in different cell types that play a role under inflammatory conditions in the gut. Besides some promising experimental data suggesting DAPK as an interesting drug target in inflammatory bowel disease there are many open questions regarding direct evidence for a role of DAPK in intestinal inflammation.

Confocal laser endomicroscopy to monitor the colonic mucosa of mice

The gastrointestinal tract is a unique organ system that provides an epithelial barrier between our underlying immune system and luminal pathogens. Disruption of gastrointestinal homeostasis, as a result of impaired barrier function, is associated with numerous pathologies including inflammatory bowel disease and colorectal cancer. In parallel to the clinical development of endoscopy technologies to monitor and diagnose these pathologies in humans, advanced mouse colonoscopy techniques are being developed. When these technologies are coupled with model systems of human disease, which are essential to our understanding of the pathophysiology of gastrointestinal diseases, the requirement for euthanasia of multiple cohorts of mice is eliminated. Here we highlight the suitability of white light endoscopy to monitor the progression of colitis in mice. We further outline the experimental power of combined standard endoscopy with confocal microendoscopy, which permits visualization of fluorescent markers in a single animal in real-time. Together, these technologies will enhance our understanding of the interplay between components of the gastrointestinal microenvironment and their role in disease.

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Monitoring of mucosal damage using white light endoscopy

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Monitoring of the epithelial barrier using confocal endomicroscopy

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Monitoring of the vasculature architecture using confocal endomicroscopy

Stratified medicine in inflammatory disorders: From theory to practice

Chronic inflammatory disorders are complex and characterized by significant heterogeneity in molecular, pathological, and clinical features. This heterogeneity poses challenges for the development of targeted molecular interventions for these disorders, as not all patients with a given clinical diagnosis have disease driven by a single dominant molecular pathway, hence not all patients will benefit equally from a given intervention. Biomarkers related to molecular manifestations of disease are increasingly being applied to enable stratified approaches to drug development. Biomarkers may be used to identify which patients are most likely to benefit from an intervention (predictive), identify patients at increased risk of disease progression (prognostic), and monitor biological responsiveness to an intervention (pharmacodynamic). Here we consider how biomarker-guided stratification of patients may increase benefit from targeted therapies for asthma, rheumatoid arthritis and inflammatory bowel diseases.

Pathogenesis of Crohn's disease

Significant progress in our understanding of Crohn's disease (CD), an archetypal common, complex disease, has now been achieved. Our ability to interrogate the deep complexities of the biological processes involved in maintaining gut mucosal homeostasis is a major over-riding factor underpinning this rapid progress. Key studies now offer many novel and expansive insights into the interacting roles of genetic susceptibility, immune function, and the gut microbiota in CD. Here, we provide overviews of these recent advances and new mechanistic themes, and address the challenges and prospects for translation from concept to clinic.

Electronic imaging to enhance lesion detection at colonoscopy

Adenoma removal prevents colorectal cancer (CRC) development. Lower adenoma detection rates correlate with increased postcolonoscopy CRC. Chromoendoscopy it is not practical for routine use. It was hoped that electronic imaging techniques would offer effective alternatives to improve detection; however, meta-analyses in average-risk patients indicate no benefit. Narrow band imaging may be of benefit for high-risk surveillance. Combining electronic imaging techniques with molecular imaging probes may highlight dysplasia at a molecular level. In future colonoscopy is likely to rely on sensitive and specific, labeled molecular probes detected by electronic endoscopic imaging to enhance detection and reduce miss rates for premalignant lesions.

Fluorescence-Raman dual modal endoscopic system for multiplexed molecular diagnostics

Optical endoscopic imaging, which was recently equipped with bioluminescence, fluorescence, and Raman scattering, allows minimally invasive real-time detection of pathologies on the surface of hollow organs. To characterize pathologic lesions in a multiplexed way, we developed a dual modal fluorescence-Raman endomicroscopic system (FRES), which used fluorescence and surface-enhanced Raman scattering nanoprobes (F-SERS dots). Real-time, in vivo, and multiple target detection of a specific cancer was successful, based on the fast imaging capability of fluorescence signals and the multiplex capability of simultaneously detected SERS signals using an optical fiber bundle for intraoperative endoscopic system. Human epidermal growth factor receptor 2 (HER2) and epidermal growth factor receptor (EGFR) on the breast cancer xenografts in a mouse orthotopic model were successfully detected in a multiplexed way, illustrating the potential of FRES as a molecular diagnostic instrument that enables real-time tumor characterization of receptors during routine endoscopic procedures.

Endoscopic imaging

OPINION STATEMENT

The most important tools are the eye and the brain. A detailed white-light high-resolution examination and ability to recognize subtle lesions provide the foundation of the ability to detect lesions in the gastrointestinal tract. Novel technologies are now available to provide additional information with the goals of detection, delineation, or classification often with a focus on neoplasia in the gastrointestinal tract. The observer using these new tools must still recognize, interpret, and then make a clinically relevant conclusion. Therefore, the assessment of these tools may focus on both the technical feasibility to use the respective equipment to obtain an image and then also the associated cognitive-based criteria for image interpretation.

Targeted localized use of therapeutic antibodies: a review of non-systemic, topical and oral applications

Therapeutic antibodies provide important tools in the "medicine chest" of today's clinician for the treatment of a range of disorders. Typically monoclonal or polyclonal antibodies are administered in large doses, either directly or indirectly into the circulation, via a systemic route which is well suited for disseminated ailments. Diseases confined within a specific localized tissue, however, may be treated more effectively and at reduced cost by a delivery system which targets directly the affected area. To explore the advantages of the local administration of antibodies, we reviewed current alternative, non-systemic delivery approaches which are in clinical use, being trialed or developed. These less conventional approaches comprise: (a) local injections, (b) topical and (c) peroral administration routes. Local delivery includes intra-ocular injections into the vitreal humor (i.e. Ranibizumab for age-related macular degeneration), subconjunctival injections (e.g. Bevacizumab for corneal neovascularization), intra-articular joint injections (i.e. anti-TNF alpha antibody for persistent inflammatory monoarthritis) and intratumoral or peritumoral injections (e.g. Ipilimumab for cancer). A range of other strategies, such as the local use of antibacterial antibodies, are also presented. Local injections of antibodies utilize doses which range from 1/10th to 1/100th of the required systemic dose therefore reducing both side-effects and treatment costs. In addition, any therapeutic antibody escaping from the local site of disease into the systemic circulation is immediately diluted within the large blood volume, further lowering the potential for unwanted effects. Needle-free topical application routes become an option when the condition is restricted locally to an external surface. The topical route may potentially be utilized in the form of eye drops for infections or corneal neovascularization or be applied to diseased skin for psoriasis, dermatitis, pyoderma gangrenosum, antibiotic resistant bacterial infections or ulcerated wounds. Diseases confined to the gastrointestinal tract can be targeted directly by applying antibody via the injection-free peroral route. The gastrointestinal tract is unusual in that its natural immuno-tolerant nature ensures the long-term safety of repeatedly ingesting heterologous antiserum or antibody materials. Without the stringent regulatory, purity and clean room requirements of manufacturing parenteral (injectable) antibodies, production costs are minimal, with the potential for more direct low-cost targeting of gastrointestinal diseases, especially with those caused by problematic antibiotic resistant or toxigenic bacteria (e.g. Clostridium difficile, Helicobacter pylori), viruses (e.g. rotavirus, norovirus) or inflammatory bowel disease (e.g. ulcerative colitis, Crohn's disease). Use of the oral route has previously been hindered by excessive antibody digestion within the gastrointestinal tract; however, this limitation may be overcome by intelligently applying one or more strategies (i.e. decoy proteins, masking therapeutic antibody cleavage sites, pH modulation, enzyme inhibition or encapsulation). These aspects are additionally discussed in this review and novel insights also provided. With the development of new applications via local injections, topical and peroral routes, it is envisaged that an extended range of ailments will increasingly fall within the clinical scope of therapeutic antibodies further expanding this market.

Differential diagnosis in inflammatory bowel disease colitis: State of the art and future perspectives

Distinction between Crohn’s disease of the colon-rectum and ulcerative colitis or inflammatory bowel disease (IBD) type unclassified can be of pivotal importance for a tailored clinical management, as each entity often involves specific therapeutic strategies and prognosis. Nonetheless, no gold standard is available and the uncertainty of diagnosis may frequently lead to misclassification or repeated examinations. Hence, we have performed a literature search to address the problem of differential diagnosis in IBD colitis, revised current and emerging diagnostic tools and refined disease classification strategies. Nowadays, the differential diagnosis is an untangled issue, and the proper diagnosis cannot be reached in up to 10% of patients presenting with IBD colitis. This topic is receiving emerging attention, as medical therapies, surgical approaches and leading prognostic outcomes require more and more disease-specific strategies in IBD patients. The optimization of standard diagnostic approaches based on clinical features, biomarkers, radiology, endoscopy and histopathology appears to provide only marginal benefits. Conversely, emerging diagnostic techniques in the field of gastrointestinal endoscopy, molecular pathology, genetics, epigenetics, metabolomics and proteomics have already shown promising results. Novel advanced endoscopic imaging techniques and biomarkers can shed new light for the differential diagnosis of IBD, better reflecting diverse disease behaviors based on specific pathogenic pathways.

The current and future role of endomicroscopy in the management of inflammatory bowel disease

Confocal laser-induced endomicroscopy (CLE), first introduced in 2003, allows the capture of images of "virtual histology" of the gastrointestinal mucosa during endoscopy, providing the opportunity to retrieve real-time visualization of the pathology of the mucosal epithelium with its cellular and subcellular structures. This new endoscopic imaging technique serves as an adjunctive diagnostic tool to the traditional ileocolonoscopy in the management of inflammatory bowel disease (IBD) patients. In multiple clinical trials, CLE has been shown to improve detection of dysplasia, assess disease activity, predict future clinical relapses, and assess potential responsiveness to anti-tumor necrosis factor therapy. This review explores in depth the current and future role of CLE in the management of IBD patients.

Novel imaging modalities for immune cell monitoring in the intestine

PURPOSE OF REVIEW

The introduction of novel molecular imaging modalities that can not only define disease states on the basis of structural changes and morphology, but also allow in-vivo visualization and characterization of molecular and biochemical alterations on a cellular level add a new dimension to our current diagnostic possibilities. The advents of innovative endoscopic devices coupled with the introduction of novel targeting ligands contribute to the recent advances made in the field of molecular imaging. The purpose of this review is to present and discuss the concepts and the potential of novel endoscopic imaging modalities for immune cell monitoring in the intestine.

RECENT FINDINGS

Recent progress concerning molecular imaging studies in animals and human patients implicates that this approach can be used to improve detection of mucosal lesions in wide-field imaging and for in-vivo characterization of the mucosa with the ultimate goal of assessing the likelihood of response to targeted therapy with biological agents. In particular, molecular endomicroscopy for assessment of mucosal immune responses ('immunoendoscopy') emerges as a novel approach for optimized endoscopic diagnosis and individualized therapy.

SUMMARY

Molecular imaging modalities in the intestine have the immediate potential to have an impact on current clinical practice and could therefore open new frontiers for clinical endoscopy and give hope for improved diagnosis and targeted therapies.

Role of programmed necrosis and cell death in intestinal inflammation

PURPOSE OF REVIEW

To critically review recent advances on the role of programmed necrosis and other cell death modalities in intestinal health and inflammatory bowel disease.

RECENT FINDINGS

Tight regulation of intestinal epithelial cell proliferation and cell death is required for intestinal physiology, and to maintain an integral barrier that restricts microbiota translocation and ensures immune tolerance. Apoptosis has long been considered as a normal part of intestinal epithelial cell turnover. However, recent studies have demonstrated that excessive cell death leads to deleterious intestinal inflammation, as is observed in inflammatory bowel disease. Additionally, a novel form of cell death dubbed programmed necrosis, or necroptosis, has been recently shown to be pathological in the gut.

SUMMARY

The role of cell death in the intestine is complex and its potential implication in intestinal diseases, and inflammatory bowel disease in particular, needs to be reevaluated.

Cytokines and mucosal immunity

PURPOSE OF REVIEW

Cytokines are integral mediators for maintaining intestinal mucosal homeostasis, as well as prominent effector molecules during chronic gut inflammatory diseases. This review focuses on recent studies of the role of specific cytokines in mucosal immunity.

RECENT FINDINGS

Dichotomous, or even opposing, functions have been described for several cytokines involved in intestinal innate immunity (most notably for members of the interleukin-1 family), which depend on the specific inflammatory conditions within the intestinal mucosa. For example, both interleukin-1α and interleukin-33 exhibit 'alarmin'-type properties that can signal tissue or cell damage, which further add to their well described proinflammatory roles. Costimulatory molecules of the tumor necrosis factor/tumor necrosis factor receptor superfamily, such as TNF-like cytokine 1A and LIGHT, are actively involved in mucosal proinflammatory pathways, but also may exert protection against infectious agents to facilitate recovery from acute inflammation. Finally, innate lymphoid cells are increasingly recognized as important cellular sources of pivotal mucosal cytokines, including the interleukin-23/T helper 17 cytokine, interleukin-22.

SUMMARY

Elucidating the complexity of cytokine signaling within the normal mucosa and during acute and chronic inflammation will be a pivotal step toward understanding the pathogenesis of immune-mediated gut diseases and developing effective therapies to treat them.

Colitis-associated neoplasia: molecular basis and clinical translation

Crohn's disease and ulcerative colitis are both associated with an increased risk of inflammation-associated colorectal carcinoma. Colitis-associated cancer (CAC) is one of the most important causes for morbidity and mortality in patients with inflammatory bowel diseases (IBD). Colitis-associated neoplasia distinctly differs from sporadic colorectal cancer in its biology and the underlying mechanisms. This review discusses the molecular mechanisms of CAC and summarizes the most important genetic alterations and signaling pathways involved in inflammatory carcinogenesis. Then, clinical translation is evaluated by discussing new endoscopic techniques and their contribution to surveillance and early detection of CAC. Last, we briefly address different types of concepts for prevention (i.e., anti-inflammatory therapeutics) and treatment (i.e., surgical intervention) of CAC and give an outlook on this important aspect of IBD.

Molecular imaging of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a kind of chronic non-specific intestinal inflammatory disease of unknown etiology. Traditional imaging is difficult for early detection of mucosal lesions and is not conducive to early treatment. Colonoscopy is a kind of invasive procedure, and its clinical use is therefore limited. Molecular imaging provides a new approach for early diagnosis of IBD. In this paper, we review recent advances in molecular imaging of IBD.

TNF and TNF-receptors: From mediators of cell death and inflammation to therapeutic giants - past, present and future

Tumor Necrosis Factor (TNF), initially known for its tumor cytotoxicity, is a potent mediator of inflammation, as well as many normal physiological functions in homeostasis and health, and anti-microbial immunity. It also appears to have a central role in neurobiology, although this area of TNF biology is only recently emerging. Here, we review the basic biology of TNF and its normal effector functions, and discuss the advantages and disadvantages of therapeutic neutralization of TNF - now a commonplace practice in the treatment of a wide range of human inflammatory diseases. With over ten years of experience, and an emerging range of anti-TNF biologics now available, we also review their modes of action, which appear to be far more complex than had originally been anticipated. Finally, we highlight the current challenges for therapeutic intervention of TNF: (i) to discover and produce orally delivered small molecule TNF-inhibitors, (ii) to specifically target selected TNF producing cells or individual (diseased) tissue targets, and (iii) to pre-identify anti-TNF treatment responders. Although the future looks bright, the therapeutic modulation of TNF now moves into the era of personalized medicine with society's challenging expectations of durable treatment success and of achieving long-term disease remission.

Beyond standard image-enhanced endoscopy confocal endomicroscopy

Endomicroscopy is a new imaging tool for gastrointestinal endoscopy. In vivo histology becomes possible at subcellular resolution during ongoing colonoscopy. Panchromoendoscopy with targeted biopsies has become the method of choice for surveillance of patients with inflammatory bowel disease. Endomicroscopy can be added after chromoendoscopy to clarify whether standard biopsies are needed. This smart biopsy concept can increase the diagnostic yield of intraepithelial neoplasia and substantially reduce the need for biopsies. Clinical acceptance is increasing because of a multitude of positive studies about the diagnostic value of endomicroscopy. Smart biopsies, functional imaging, and molecular imaging may represent the future for endomicroscopy.

Not all monoclonals are created equal - lessons from failed drug trials in Crohn's disease

The recent success of the anti-integrin antibody Vedolizumab can barely conceal the fact that the biologics armamentarium in Crohn's disease has barely evolved beyond TNF blockers so far. This contrasts with other immune-related diseases considered mechanistically and genetically closely related, such as psoriasis and rheumatoid arthritis, where approved biologics target a variety of independent biological mechanisms. Several pharmacological assets that entered clinical development have proven ineffective, or less effective than originally anticipated. While blockade of IL-17A and its receptor via Secukinumab and Brodalumab, respectively, worsened Crohn's disease, the beneficial effect of IL-12/23 p40 blockade via Ustekinumab appeared confined to a subpopulation of Crohn's disease patients who have previously failed on TNF blockers. Clinical development of the IFNγ blocker Fontolizumab was stopped despite demonstrating some clinical benefit, while the T cell co-stimulation blocker Abatacept did not exhibit any hint towards efficacy in Crohn's disease. Here I review results from these individual development programmes, and also reflect on the lack of efficacy of the TNF blocker Etanercept. I will discuss aspects of individual trials that might have confounded their interpretation and highlight the evolution in primary and secondary endpoints that have contributed to increasing robustness of results obtained in recent years. Finally, I suggest that mechanistic studies in murine genetic models combined with exploratory immunological studies incorporated in early drug development may represent the key for identifying the next generation of successful pharmacological targets in Crohn's disease.

Cytokines in inflammatory bowel disease

Cytokines have a crucial role in the pathogenesis of inflammatory bowel diseases (IBDs), such as Crohn's disease and ulcerative colitis, where they control multiple aspects of the inflammatory response. In particular, the imbalance between pro-inflammatory and anti-inflammatory cytokines that occurs in IBD impedes the resolution of inflammation and instead leads to disease perpetuation and tissue destruction. Recent studies suggest the existence of a network of regulatory cytokines that has important implications for disease progression. In this Review, we discuss the role of cytokines produced by innate and adaptive immune cells, as well as their relevance to the future therapy of IBD.