Development and Evaluation of a Fluorescent Antibody-Drug Conjugate for Molecular Imaging and Targeted Therapy of Pancreatic Cancer

Elucidating Critical Factors of Internalization and Drug Release of Antibody-Drug Conjugates (ADCs) Using Kinetic Parameters Evaluated by a Novel Tool Named TORCH

During the past decade, antibody-drug conjugates (ADCs) have emerged as new drugs in cancer therapy with 15 ADCs already approved such as Kadcyla, Enhertu, and Adcetris. ADCs contain a cytotoxic drug that is linked to an antibody, allowing for specific delivery of the warhead to tumor cells. Typically, the antibody targets a tumor-specific antigen expressed on the cell surface. After the internalization of ADCs into cells, the linker is often cleaved by enzymes in the lysosomal compartment of the cell, releasing the warhead and thereby allowing for its interaction with, for example, the DNA or the tubulin cytoskeleton, which finally leads to cell death. Consequently, binding, internalization, and drug release are key attributes for the efficacy of ADCs. Here, we describe a novel molecule named TORCH (Turn On after Release by CatHepsins) that contains a fluorescence quencher system that is separated by a cathepsin B-cleavable linker. When conjugated to an antibody, the TORCH molecule allows one to gain valuable insights on the internalization and drug release of ADCs. While we cannot exclude the influence of other factors such as receptor recycling, we have found that the receptor density is directly related to the amount of payload released intracellularly, meaning that the internalization per receptor is very similar for all investigated antibodies and cell lines.

NIR-II aza-BODIPY Platform for the Development of a Fluorescent Antibody Drug Conjugate

Real-time imaging of antibody-drug conjugates (ADCs) offers valuable insights for assessing tumor targeting specificity, monitoring therapeutic efficacy, and detecting off-target accumulation that may cause adverse effects. To enable precise tracking, we developed a versatile fluorescent platform based on an NIR-II emitting aza-BODIPY dye, which can be site-specifically grafted onto an IgG1 antibody to generate well-defined fluorescent ADCs. As a proof of concept, we synthesized an HER2-targeting trastuzumab immunoconjugate bearing a NIR-II aza-BODIPY fluorophore. The cytotoxic monomethyl auristatin E (MMAE) payload was introduced in the final step, resulting in a trackable and homogeneous ADC suitable for both in vitro and in vivo investigations. The resulting Trastu-azaNIRII-MMAE selectively accumulated in HER2-positive subcutaneous tumors, significantly reducing the tumor growth. Using NIR-II optical imaging, a single injection of the NIR-II-ADC allowed for the detection of the conjugate over a period of more than one month, highlighting its potential for long-term tracking and therapeutic applications.

Antibody conjugates in neuroblastoma: a step forward in precision medicine

Neuroblastoma (NB) is a pediatric cancer that often manifests in a high-risk form and is characterized by frequent relapses and resistance to conventional therapies. This underscores the urgent need for more effective and targeted treatment strategies. One promising avenue has been the identification of unique or overexpressed surface antigens on neoplastic cells, which has facilitated the development of antibody conjugates and related technologies. These include antibody-drug conjugates (ADCs) and immunotoxins (ITs), which deliver cytotoxic agents directly to tumor cells, as well as antibody-fluorophore conjugates (AFCs), which bind to surface antigens with high specificity to target malignant tumors. Additionally, radioimmunotherapy (RIT) allows the precise delivery of radioactive isotopes linked to a monoclonal antibody directly to the tumor cells. ADCs, ITs, and RIT represent a novel class of anti-cancer agents offering precision therapy with reduced systemic toxicity, enabling longer and potentially more effective treatment regimens. Meanwhile, AFCs are valuable tools in diagnostics, aiding in detecting and characterizing malignant tissues. Despite advancements in antibody conjugates for NB, significant challenges persist, including optimizing payload delivery, mitigating off-target effects, and addressing tumor heterogeneity. Future research should also prioritize refining and integrating these technologies into multimodal treatment protocols to improve outcomes for pediatric NB patients.

Antibody-drug conjugates: prospects for the next generation

The concept of a 'magic bullet' was first introduced by Paul Ehrlich in the early 1900s, he foresaw the advent of targeted therapies and the specific killing of harmful cells and/or microorganisms. However, these therapies were only used in the clinic after the second half of the 20th century with the development of specific monoclonal antibodies. To date, 13 antibody-drug conjugates (ADCs) are commercially available. Many advances have been made by modifying one or several of the three main components of an ADC, namely the antibody, the cleavable or non-cleavable linker or the payload, and by integrating conjugation chemistry. Despite these efforts, some problems have emerged and thus limit their effectiveness. New strategies could overcome these problems and identify the next generation of ADC.

Antibody drug conjugates: hitting the mark in pancreatic cancer?

Pancreatic cancer is one of the most common causes of cancer-related death, and the 5-year survival rate has only improved marginally over the last decade. Late detection of the disease means that in most cases the disease has advanced locally and/or metastasized, and curative surgery is not possible. Chemotherapy is still the first-line treatment however, this has only had a modest impact in improving survival, with associated toxicities. Therefore, there is an urgent need for targeted approaches to better treat pancreatic cancer, while minimizing treatment-induced side-effects. Antibody drug conjugates (ADCs) are one treatment option that could fill this gap. Here, a monoclonal antibody is used to deliver extremely potent drugs directly to the tumor site to improve on-target killing while reducing off-target toxicity. In this paper, we review the current literature for ADC targets that have been examined in vivo for treating pancreatic cancer, summarize current and on-going clinical trials using ADCs to treat pancreatic cancer and discuss potential strategies to improve their therapeutic window.

Trifunctional Dibromomaleimide Reagents Built Around A Lysine Scaffold Deliver Site-selective Dual-modality Antibody Conjugation

We describe the synthesis and application of a selection of trifunctional reagents for the dual-modality modification of native, solvent accessible disulfide bonds in trastuzumab. The reagents were developed from the dibromomaleimide (DBM) platform with two orthogonal clickable functional groups built around a lysine core. We also describe the development of an aryl diselenide additive which enables antibody disulfide reduction in 4 minutes and a rapid overall reduction-bridging-double click sequence.

Synthesis and biological evaluation of theranostic Trastuzumab–SN38 conjugate for Near-IR fluorescence imaging and targeted therapy of HER2+ breast cancer

Here, we report on the design, synthesis, and biological evaluation of a new theranostic antibody drug conjugate (ADC), Cy5-Ab-SS-SN38, that consists of the HER2-specific antibody trastuzumab (Ab) connected to the near infrared (NIR) pentamethine cyanine dye Cy5 and SN38, which is a bioactive metabolite of the anticancer drug irinotecan. SN38 is bound to an antibody through a glutathione-responsive self-immolative disulfide carbamate linker. For the first time, we explored this linker in ADC and found that it to reduce the drug release rate, which is important for safe drug delivery. The developed ADC exhibited specific accumulation and nanomolar anti-breast cancer activity on HER2-positive (HER2+) cell lines but no effect on HER2-. Animals treated with this ADC exhibited good tolerance. In vivo studies have shown that the ADC had good targeting ability for HER2+ tumors with much higher anticancer potency than trastuzumab itself or a mixture of trastuzumab with SN38. Side-by-side HER2+/HER2-xenograft at the 10 mg/kg dose exhibited specific accumulation and reduction of HER2+ tumor but not accumulation or growth inhibition of HER2-counterpart. The self-immolative disulfide linker implemented in this study was proven to be successful, broadening its utilization with other antibodies for targeted anticancer therapy in general. We believe that the theranostic ADCs comprising the glutathione-responsive self-immolative disulfide carbamate linker are applicable for the treatment and fluorescent monitoring of malignancies and anticancer drug delivery.

One-Step Conversion of NHS Esters to Reagents for Site-Directed Labeling of IgG Antibodies

Antibody conjugates are extensively used for diagnostics and therapeutics, and as a tool for molecular biology. To prepare such conjugates N-hydroxysuccinimide (NHS) esters are most often used due to the straightforward experimental procedure and the commercial accessibility of the reagents. Such conjugates are however highly heterogeneous, since only the reactivity of the lysines determines the distribution of labels. This has inspired the development of methods that experimentally are as facile but produce conjugates of higher quality. Herein, we report the development of a reagent that can, in one step, be activated with an NHS ester of choice and subsequently can be directly used for site-directed labeling of antibodies. The reagent can be prepared in three synthetic steps and produces conjugates with similar ease as for NHS esters, however in a site-directed manner. We show that the reagent is quantitatively activated by a variety of NHS esters, and we use these to functionalize IgG1, IgG2, and IgG4 antibodies.

Antibody-Based Approaches to Target Pancreatic Tumours

Pancreatic cancer is an aggressive cancer with a dismal prognosis. This is due to the difficulty to detect the disease at an early and curable stage. In addition, only limited treatment options are available, and they are confronted by mechanisms of resistance. Monoclonal antibody (mAb) molecules are highly specific biologics that can be directly used as a blocking agent or modified to deliver a drug payload depending on the desired outcome. They are widely used to target extracellular proteins, but they can also be employed to inhibit intracellular proteins, such as oncoproteins. While mAbs are a class of therapeutics that have been successfully employed to treat many cancers, they have shown only limited efficacy in pancreatic cancer as a monotherapy so far. In this review, we will discuss the challenges, opportunities and hopes to use mAbs for pancreatic cancer treatment, diagnostics and imagery.

Development of Photoremovable Linkers as a Novel Strategy to Improve the Pharmacokinetics of Drug Conjugates and Their Potential Application in Antibody-Drug Conjugates for Cancer Therapy

Although there have been extensive research and progress on the discovery of anticancer drug over the years, the application of these drugs as stand-alone therapy has been limited by their off-target toxicities, poor pharmacokinetic properties, and low therapeutic index. Targeted drug delivery, especially drug conjugate, has been recognized as a technology that can bring forth a new generation of therapeutics with improved efficacy and reduced side effects for cancer treatment. The linker in a drug conjugate is of essential importance because it impacts the circulation time of the conjugate and the release of the drug for full activity at the target site. Recently, the light-triggered linker has attracted a lot of attention due to its spatiotemporal controllability and attractive prospects of improving the overall pharmacokinetics of the conjugate. In this paper, the latest developments of UV- and IR-triggered linkers and their application and potential in drug conjugate development are reviewed. Some of the most-well-researched photoresponsive structural moieties, such as UV-triggered coumarin, ortho-nitrobenzyl group (ONB), thioacetal ortho-nitrobenzaldehyde (TNB), photocaged C40-oxidized abasic site (PC4AP), and IR-triggered cyanine and BODIPY, are included for discussion. These photoremovable linkers show better physical and chemical stabilities and can undergo rapid cleavage upon irradiation. Very importantly, the drug conjugates containing these linkers exhibit reduced off-target toxicity and overall better pharmacokinetic properties. The progress on photoactive antibody-drug conjugates, such as antibody-drug conjugates (ADC) and antibody-photoabsorber conjugate (APC), as precision medicine in clinical cancer treatment is highlighted.

Antibody-Drug Conjugate Targets, Drugs and Linkers

Antibody-drug conjugates offer the possibility of directing powerful cytotoxic agents to a malignant tumor while sparing normal tissue. The challenge is to select an antibody target expressed exclusively or at highly elevated levels on the surface of tumor cells and either not all or at low levels on normal cells. The current review explores 78 targets that have been explored as antibody-drug conjugate targets. Some of these targets have been abandoned, 9 or more are the targets of FDA-approved drugs, and most remain active clinical interest. Antibody-drug conjugates require potent cytotoxic drug payloads, several of these small molecules are discussed, as are the linkers between the protein component and small molecule components of the conjugates. Finally, conclusions regarding the elements for the successful antibody-drug conjugate are discussed.

The Use of Fluorescent Anti-CEA Antibodies to Label, Resect and Treat Cancers: A Review

A major barrier to the diagnosis and effective treatment of solid-tumor cancers is the difficulty in detection and visualization of tumor margins in primary and metastatic disease. The use of fluorescence can augment the surgeon's ability to detect cancer and aid in its resection. Several cancer types express carcinoembryonic antigen (CEA) including colorectal, pancreatic and gastric cancer. Antibodies to CEA have been developed and tagged with near-infrared fluorescent dyes. This review article surveyed the use of CEA antibodies conjugated to fluorescent probes for in vivo studies since 1990. PubMed and Google Scholar databases were queried, and 900 titles and abstracts were screened. Fifty-nine entries were identified as possibly meeting inclusion/exclusion criteria and were reviewed in full. Forty articles were included in the review and their citations were screened for additional entries. A total of 44 articles were included in the final review. The use of fluorescent anti-CEA antibodies has been shown to improve detection and resection of tumors in both murine models and clinically. The cumulative results indicate that fluorescent-conjugated anti-CEA antibodies have important potential to improve cancer diagnosis and surgery. In an emerging technology, anti-CEA fluorescent antibodies have also been successfully used for photoimmunotherapy treatment for cancer.

Tissue biodistribution and tumor targeting of near-infrared labelled anti-CD38 antibody-drug conjugate in preclinical multiple myeloma

Daratumumab (DARA) is an FDA-approved high-affinity monoclonal antibody targeting CD38 that has shown promising therapeutic efficacy in double refractory multiple myeloma (MM) patients. Despite the well-established clinical efficacy of DARA, not all heavily pretreated patients respond to single-agent DARA, and the majority of patients who initially respond eventually progress. Antibody-drug conjugates (ADCs) combine the highly targeted tumor antigen recognition of antibodies with the cell killing properties of chemotherapy for effective internalization and processing of the drug. In this study, we evaluated the anti-tumor efficacy of DARA conjugated to the maytansine derivative, mertansine (DM1), linked via a non-cleavable bifunctional linker. The ADC was labelled with the near-infrared (NIR) fluorophore IRDye800 (DARA-DM1-IR) to evaluate its stability, biodistribution and pharmacokinetics in vitro and in vivo. We demonstrated the conjugation of: 1) DM1 enhanced tumor-killing efficacy of the native DARA and 2) IRDye800 allowed for visualization of uptake and tumor targeting ability of the ADC. With the advent of other classes of immunoconjugates for use in MM, we reasoned that such imaging techniques can be utilized to evaluate other promising conjugates in preclinical MM models on a whole-body and cellular level.

Imaging cancer cells with nanostructures: Prospects of nanotechnology driven non-invasive cancer diagnosis

The application of nanostructured materials in medicine is a rapidly evolving area of research that includes both the diagnosis and treatment of various diseases. Metals, metal oxides and carbon-based nanomaterials have shown much promise in medical technological advancements due to their tunable physical, chemical and biological properties. The nanoscale properties, especially the size, shape, surface chemistry and stability makes them highly desirable for diagnosing and treating various diseases, including cancers. Major applications of nanomaterials in cancer diagnosis include in vivo bioimaging and molecular marker detection, mainly as image contrast agents using modalities such as radio, magnetic resonance, and ultrasound imaging. When a suitable targeting ligand is attached on the nanomaterial surface, it can help pinpoint the disease site during imaging. The application of nanostructured materials in cancer diagnosis can help in the early detection, treatment and patient follow-up . This review aims to gather and present the information regarding the application of nanotechnology in cancer diagnosis. We also discuss the challenges and prospects regarding the application of nanomaterials as cancer diagnostic tools.

Visualization of Intratumor Pharmacokinetics of [fam-] Trastuzumab Deruxtecan (DS-8201a) in HER2 Heterogeneous Model Using Phosphor-integrated Dots Imaging Analysis

PURPOSE

We assessed the intratumor pharmacokinetics of [fam-] trastuzumab deruxtecan, T-DXd (known as DS-8201a), a novel HER2-targeted antibody-drug conjugate, using phosphor-integrated dots (PID)-imaging analysis to elucidate its pharmacologic mechanism.

EXPERIMENTAL DESIGN

We used two mouse xenograft models administered T-DXd at the concentration of 4 mg/kg: (i) a heterogeneous model in which HER2-positive and HER2-negative cell lines were mixed, and (ii) a homogeneous model in which both cell types were transplanted separately into the same mouse. PID imaging involved immunostaining using novel high-intensity fluorescent nanoparticles. The distribution of T-DXd was assessed by PID imaging targeting the parent antibody, trastuzumab, and the payload, DXd, in serial frozen sections, respectively.

RESULTS

After T-DXd administration in the heterogeneous model, HER2 expression tended to decrease in a time-dependent manner. The distribution of trastuzumab and DXd was observed by PID imaging along the HER2-positive area throughout the observation period. A detailed comparison of the PID distribution between trastuzumab and DXd showed that trastuzumab matched almost perfectly with the HER2-positive area. In contrast, DXd exhibited widespread distribution in the surrounding HER2-negative area as well. In the HER2-negative tumor of the homogeneous model, the PID distribution of trastuzumab and DXd remained extremely low throughout the observation period.

CONCLUSIONS

Our results suggest that T-DXd is distributed to tumor tissues via trastuzumab in a HER2-dependent manner and then to adjacent HER2-negative areas. We successfully visualized the intratumor distribution of T-DXd and its mechanism of action, the so-called "bystander effect."

Therapeutic Application of Monoclonal Antibodies in Pancreatic Cancer: Advances, Challenges and Future Opportunities

Pancreatic cancer remains as one of the most aggressive cancer types. In the absence of reliable biomarkers for its early detection and more effective therapeutic interventions, pancreatic cancer is projected to become the second leading cause of cancer death in the Western world in the next decade. Therefore, it is essential to discover novel therapeutic targets and to develop more effective and pancreatic cancer-specific therapeutic agents. To date, 45 monoclonal antibodies (mAbs) have been approved for the treatment of patients with a wide range of cancers; however, none has yet been approved for pancreatic cancer. In this comprehensive review, we discuss the FDA approved anticancer mAb-based drugs, the results of preclinical studies and clinical trials with mAbs in pancreatic cancer and the factors contributing to the poor response to antibody therapy (e.g. tumour heterogeneity, desmoplastic stroma). MAb technology is an excellent tool for studying the complex biology of pancreatic cancer, to discover novel therapeutic targets and to develop various forms of antibody-based therapeutic agents and companion diagnostic tests for the selection of patients who are more likely to benefit from such therapy. These should result in the approval and routine use of antibody-based agents for the treatment of pancreatic cancer patients in the future.

Exploring a model-based analysis of patient derived xenograft studies in oncology drug development

Purpose

To assess whether a model-based analysis increased statistical power over an analysis of final day volumes and provide insights into more efficient patient derived xenograft (PDX) study designs.

Methods

Tumour xenograft time-series data was extracted from a public PDX drug treatment database. For all 2-arm studies the percent tumour growth inhibition (TGI) at day 14, 21 and 28 was calculated. Treatment effect was analysed using an un-paired, two-tailed t-test (empirical) and a model-based analysis, likelihood ratio-test (LRT). In addition, a simulation study was performed to assess the difference in power between the two data-analysis approaches for PDX or standard cell-line derived xenografts (CDX).

Results

The model-based analysis had greater statistical power than the empirical approach within the PDX data-set. The model-based approach was able to detect TGI values as low as 25% whereas the empirical approach required at least 50% TGI. The simulation study confirmed the findings and highlighted that CDX studies require fewer animals than PDX studies which show the equivalent level of TGI.

Conclusions

The study conducted adds to the growing literature which has shown that a model-based analysis of xenograft data improves statistical power over the common empirical approach. The analysis conducted showed that a model-based approach, based on the first mathematical model of tumour growth, was able to detect smaller size of effect compared to the empirical approach which is common of such studies. A model-based analysis should allow studies to reduce animal use and experiment length providing effective insights into compound anti-tumour activity.

Drug Combination in Cancer Treatment-From Cocktails to Conjugated Combinations

It is well recognized today that anticancer drugs often are most effective when used in combination. However, the establishment of chemotherapy as key modality in clinical oncology began with sporadic discoveries of chemicals that showed antiproliferative properties and which as a first attempt were used as single agents. In this review we describe the development of chemotherapy from its origins as a single drug treatment with cytotoxic agents to polydrug therapy that includes targeted drugs. We discuss the limitations of the first chemotherapeutic drugs as a motivation for the establishment of combined drug treatment as standard practice in spite of concerns about frequent severe, dose limiting toxicities. Next, we introduce the development of targeted treatment as a concept for advancement within the broader field of small-molecule drug combination therapy in cancer and its accelerating progress that was boosted by recent scientific and technological progresses. Finally, we describe an alternative strategy of drug combinations using drug-conjugates for selective delivery of cytotoxic drugs to tumor cells that potentiates future improvement of drug combinations in cancer treatment. Overall, in this review we outline the development of chemotherapy from a pharmacological perspective, from its early stages to modern concepts of using targeted therapies for combinational treatment.

Safety and Stability of Antibody-Dye Conjugate in Optical Molecular Imaging

PURPOSE

The development of molecularly targeted tracers is likely to improve the accuracy of diagnostic, screening, and therapeutic tools. Despite the many therapeutic antibodies that are FDA-approved with known toxicity, only a limited number of antibody-dye conjugates have been introduced to the clinic. Thorough evaluation of the safety, stability, and pharmacokinetics of antibody conjugates in the clinical setting compared with their parental components could accelerate the clinical approval of antibodies as agents for molecular imaging. Here we investigate the safety and stability of a near-infrared fluorescent dye (IRDye800CW) conjugated panitumumab, an approved therapeutic antibody, and report on the product stability, pharmacokinetics, adverse events, and QTc interval changes in patients.

PROCEDURES

Panitumumab-IRDye800CW was made under good manufacturing practice (GMP) conditions in a single batch on March 26, 2014, and then evaluated over 4.5 years at 0, 3, and 6 months, and then at 6-month intervals thereafter. We conducted early phase trials in head and neck, lung, pancreas, and brain cancers with panitumumab-IRDye800CW. Eighty-one patients scheduled to undergo standard-of-care surgery were infused with doses between 0.06 to 2.83 mg/kg of antibody. Patient ECGs, blood samples, and adverse events were collected over 30-day post-infusion for analysis.

RESULTS

Eighty-one patients underwent infusion of the study drug at a range of doses. Six patients (7.4 %) experienced an adverse event that was considered potentially related to the drug. The most common event was a prolonged QTc interval which occurred in three patients (3.7 %). Panitumumab-IRDye800CW had two OOS results at 42 and 54 months while meeting all other stability testing criteria.

CONCLUSIONS

Panitumumab-IRDye800CW was safe and stable to administer over a 54-month window with a low rate of adverse events (7.4 %) which is consistent with the rate associated with panitumumab alone. This data supports re-purposing therapeutic antibodies as diagnostic imaging agents with limited preclinical toxicology studies.

Heterogeneity of CEACAM5 in breast cancer

CEACAM5 is overexpressed in many primary breast carcinomas. However, the exact role of CEACAM5 in breast cancer tumorigenesis remains unresolved. Here, we examined a repository of 110 cryopreserved primary breast carcinomas by immunohistochemistry to assess the distribution of CEACAM5 in tumor subtypes. The majority of estrogen receptor-positive and HER2-overexpressing tumors were CEACAM5-positive, whereas most of Triple-negative tumors were negative. Assessing sample sets of paired primary breast cancers and corresponding lymph node lesions from a total of 59 patients revealed a high correlation between primary tumor and lymph node with regard to CEACAM5-status. However, a notable subset of sample sets demonstrated intratumoral heterogeneity in the primary tumor, the metastatic lesion or both, suggesting that both CEACAM5-positive and –negative cells can play a role in tumor dissemination. When examining the consequence of expression of CEACAM5 in breast cancer cell lines in culture assays we found that CEACAM5-expressing cells were less invasive. In survival analysis, using cohort studies of breast cancer, expression of CEACAM5 predicted different clinical outcomes depending on molecular subtypes. Altogether, our analysis suggests that CEACAM5 plays a context-dependent role in breast cancer that warrants further investigation.

To What Extent Do Fluorophores Bias the Biological Activity of Peptides? A Practical Approach Using Membrane-Active Peptides as Models

The characterization of biologically active peptides relies heavily on the study of their efficacy, toxicity, mechanism of action, cellular uptake, or intracellular location, using both in vitro and in vivo studies. These studies frequently depend on the use of fluorescence-based techniques. Since most peptides are not intrinsically fluorescent, they are conjugated to a fluorophore. The conjugation may interfere with peptide properties, thus biasing the results. The selection of the most suitable fluorophore is highly relevant. Here, a comprehensive study with blood-brain barrier (BBB) peptide shuttles (PepH3 and PepNeg) and antimicrobial peptides (AMPs) (vCPP2319 and Ctn[15-34]), tested as anticancer peptides (ACPs), having different fluorophores, namely 5(6)-carboxyfluorescein (CF), rhodamine B (RhB), quasar 570 (Q570), or tide fluor 3 (TF3) attached is presented. The goal is the evaluation of the impact of the selected fluorophores on peptide performance, applying routinely used techniques to assess cytotoxicity/toxicity, secondary structure, BBB translocation, and cellular internalization. Our results show that some fluorophores significantly modulate peptide activity when compared with unlabeled peptides, being more noticeable in hydrophobic and charged fluorophores. This study highlights the need for a careful experimental design for fluorescently labeled molecules, such as peptides.

Advancing Aptamers as Molecular Probes for Cancer Theranostic Applications-The Role of Molecular Dynamics Simulation

Theranostics cover emerging technologies for cell biomarking for disease diagnosis and targeted introduction of drug ingredients to specific malignant sites. Theranostics development has become a significant biomedical research endeavor for effective diagnosis and treatment of diseases, especially cancer. An efficient biomarking and targeted delivery strategy for theranostic applications requires effective molecular coupling of binding ligands with high affinities to specific receptors on the cancer cell surface. Bioaffinity offers a unique mechanism to bind specific target and receptor molecules from a range of non-targets. The binding efficacy depends on the specificity of the affinity ligand toward the target molecule even at low concentrations. Aptamers are fragments of genetic materials, peptides, or oligonucleotides which possess enhanced specificity in targeting desired cell surface receptor molecules. Aptamer-target binding results from several inter-molecular interactions including hydrogen bond formation, aromatic stacking of flat moieties, hydrophobic interaction, electrostatic, and van der Waals interactions. Advancements in Systematic Evolution of Ligands by Exponential Enrichment (SELEX) assay has created the opportunity to artificially generate aptamers that specifically bind to desired cancer and tumor surface receptors with high affinities. This article discusses the potential application of molecular dynamics (MD) simulation to advance aptamer-mediated receptor targeting in targeted cancer therapy. MD simulation offers real-time analysis of the molecular drivers of the aptamer-receptor binding and generate optimal receptor binding conditions for theranostic applications. The article also provides an overview of different cancer types with focus on receptor biomarking and targeted treatment approaches, conventional molecular probes, and aptamers that have been explored for cancer cells targeting.

Fluorescent delivery vehicle containing cobalt oxide-umbelliferone nanoconjugate: DNA/protein interaction studies and anticancer activity on MF7 cancer cell line

Fluorescent labeling is limited to certain molecules and alters biomolecule functionality. A new class of nanomaterial with anticancer activity and fluorescence properties has been designed and prepared. This nanotherapeutic conjugate of natural molecules has a selective binding site in cancer cell lines. Natural drug umbelliferone was taken with cobalt metal ions in a one pot assembly in the presence of tannic acid which yields new fluorescent nanoparticles of umbelliferone cobalt oxide nanoconjugate. Umbelliferone has high fluorescent properties and also has coordination ability to bind with central metal ions. The nanoconjugate was synthesized and characterized by using TEM, EDX analysis, SEM, XRD, and FTIR spectroscopy. TEM shows that the average size of the particles formed with umbelliferone is ∼20 nm. The solubility of the drug nanoparticles in water showed compatibility with cancer cells and provided a favorable environment to investigate the mechanism of action on the MCF-7 cell line. The nanoconjugate is microcrystalline in nature and gives a clear suspension in water. The nanocobalt conjugate was loaded on TiO2 nanoparticles by ultrasonication, and the solution was digested overnight. The conjugate of the drug with a TiO2 drug carrier was stable in solution and maintained the nanostructure ∼34.6 nm. A comparative study with nano-vehicle TiO2 and the nanoconjugate was performed. TiO2 was used to compare the anti-cancer activity of the nanoconjugate at low dose in vitro. It was observed that the nanoconjugate with TiO2 is capable of reaching the specific target like the TiO2 nanoparticle and enhance the chemotherapeutic impact. Hence, the nanoconjugate can also be used like nano-TiO2, as the drug and carrier. The ct-DNA and HSA protein binding studies were done and validated by docking studies.

PDL-1 Antibody Drug Conjugate for Selective Chemo-Guided Immune Modulation of Cancer

Targeting immune checkpoint molecules such as programmed death ligand-1 (PDL1) is an emerging strategy for anti-cancer therapy. However, transient expression of PDL1 and difficulty in tumor stroma penetration has limited the utility of anti-PDL1 therapy. To overcome these limitations, we report a new conjugate between the clinically approved PDL1 antibody (PDL1 AB) and drug Doxorubicin (Dox), named PDL1-Dox. We conjugated PDL1-Dox through a hydrazone linker containing a polyethylene glycol (PEG) spacer, which allows it to dissociate in a tumor environment and improves solubility. The purpose of using Dox is to disrupt the tumor extracellular environment so that PDL-1 antibody can penetrate the tumor core. PDL1-Dox demonstrates significant cell killing, disruption of tumor spheroid and induction of apoptosis in a breast cancer cell line. Significant release of IFN-γ suggests PDL1-Dox can upmodulate T cell activation. Optical imaging of dye conjugate supports the selective tumor targeting ability and core penetration of the construct.

A theranostic agent for cancer therapy and imaging in the second near-infrared window

Theranostic nanoparticles are integrated systems useful for simultaneous diagnosis and imaging guided delivery of therapeutic drugs, with wide ranging potential applications in the clinic. Here we developed a theranostic nanoparticle (~ 24 nm size by dynamic light scattering) p-FE-PTX-FA based on polymeric micelle encapsulating an organic dye (FE) fluorescing in the 1,000-1,700 nm second near-infrared (NIR-II) window and an anti-cancer drug paclitaxel. Folic acid (FA) was conjugated to the nanoparticles to afford specific binding to molecular folate receptors on murine breast cancer 4T1 tumor cells. In vivo, the nanoparticles accumulated in 4T1 tumor through both passive and active targeting effect. Under an 808 nm laser excitation, fluorescence detection above 1,300 nm afforded a large Stokes shift, allowing targeted molecular imaging tumor with high signal to background ratios, reaching a high tumor to normal tissue signal ratio (T/NT) of (20.0 ± 2.3). Further, 4T1 tumors on mice were completed eradicated by paclitaxel released from p-FE-PTA-FA within 20 days of the first injection. Pharmacokinetics and histology studies indicated p-FE-PTX-FA had no obvious toxic side effects to major organs. This represented the first NIR-II theranostic agent developed.

Surfactants Improve Live Cell Imaging of Human Pancreatic Islets

OBJECTIVES

Newport Green is a zinc-specific fluorescent dye developed to monitor cellular zinc transport. In pancreatic islets with zinc-rich β-cells, Newport Green is expected to be useful as an islet-specific indicator for live imaging. However, the low penetration of Newport Green into islets hinders clear detection. The aim of this study was to develop a practical method of live islet imaging by using surfactants to enhance the penetration efficiency.

METHODS

Surfactants (F127, Tween 20, and Triton X-100) were co-incubated with Newport Green for fluorescent imaging of live isolated human islet and nonislet tissues. Toxicity, enhancement of Newport Green fluorescence, and effects on specificity to islets were examined.

RESULTS

Newport Green fluorescent intensity was increased after co-incubation with all surfactants tested (0.2-3.2 mM); however, surfactants were toxic to islets at high concentrations. Within the nontoxic range, high specificity to islets was observed when co-incubated with Tween 20 at 0.2-0.4 mM, compared with F127 and Triton X-100. This optimized range successfully distinguished islets from nonislet tissues using statistically calculated cutoff value of Newport Green fluorescent intensity.

CONCLUSIONS

Surfactants, particularly Tween 20 in the optimized range, effectively and selectively enhanced Newport Green fluorescence in live islets without increasing islet toxicity.

Fluorescent-guided surgery for sentinel lymph node detection in gastric cancer and carcinoembryonic antigen targeted fluorescent-guided surgery in colorectal and pancreatic cancer

Sentinel lymph node procedures for gastric cancer resections using indocyanine green (ICG) linked to Nanocoll outperformed normal ICG but did not provide information on possible lymph node metastasis. Carcinoembryonic antigen targeted fluorescent imaging using SGM‐101 was successful in both pancreatic and colorectal cancer. A large phase III multicentre trial will soon be initiated in colorectal cancer patients.

Self-stabilized, hydrophobic or PEGylated paclitaxel polymer prodrug nanoparticles for cancer therapy

Facile derivatization of paclitaxel (Ptx) and subsequent “drug-initiated” synthesis of well-defined Ptx-polymer prodrugs was performed from nitroxide-mediated polymerization or reversible addition–fragmentation chain transfer polymerization.

Correlation Between Preoperative Serum Carcinoembryonic Antigen Levels and Expression on Pancreatic and Rectal Cancer Tissue

Carcinoembryonic antigen (CEA)-targeted imaging and therapeutic agents are being tested in clinical trials. If CEA overexpression in malignant tissue corresponds with elevated serum CEA, serum CEA could assist in selecting patients who may benefit from CEA-targeted agents. This study aims to assess the relationship between serum CEA and CEA expression in pancreatic (n = 20) and rectal cancer tissues (n = 35) using histopathology. According to local laboratory standards, a serum CEA >3 ng/mL was considered elevated. In pancreatic cancer patients a significant correlation between serum CEA and percentage of CEA-expressing tumor cells was observed (P = .04, ρ = .47). All 6 patients with homogeneous CEA expression in the tumor had a serum CEA >3 ng/mL. Most rectal cancer tissues (32/35) showed homogeneous CEA expression, independent of serum CEA levels. This study suggests that selection of pancreatic cancer patients for CEA-targeted agents via serum CEA appears adequate. For selection of rectal cancer patients, serum CEA levels are not informative.

Development of Fluorophore-Labeled Thailanstatin Antibody-Drug Conjugates for Cellular Trafficking Studies

As the antibody-drug conjugate (ADC) field grows increasingly important for cancer treatment, it is vital for researchers to establish a firm understanding of how ADCs function at the molecular level. To gain insight into ADC uptake, trafficking, and catabolism-processes that are critical to ADC efficacy and toxicity-imaging studies have been performed with fluorophore-labeled conjugates. However, such labels may alter the properties and behavior of the ADC under investigation. As an alternative approach, we present here the development of a "clickable" ADC bearing an azide-functionalized linker-payload (LP) poised for "click" reaction with alkyne fluorophores; the azide group represents a significantly smaller structural perturbation to the LP than most fluorophores. Notably, the clickable ADC shows excellent potency in target-expressing cells, whereas the fluorophore-labeled product ADC suffers from a significant loss of activity, underscoring the impact of the label itself on the payload. Live-cell confocal microscopy reveals robust uptake of the clickable ADC, which reacts selectively in situ with a derivatized fluorescent label. Time-course trafficking studies show greater and more rapid net internalization of the ADCs than the parent antibody. More generally, the application of chemical biology tools to the study of ADCs should improve our understanding of how ADCs are processed in biological systems.

Detection and Specific Elimination of EGFR+ Ovarian Cancer Cells Using a Near Infrared Photoimmunotheranostic Approach

PURPOSE

Targeted theranostics is an alternative strategy in cancer management that aims to improve cancer detection and treatment simultaneously. This approach combines potent therapeutic and diagnostic agents with the specificity of different cell receptor ligands in one product. The success of antibody drug conjugates (ADCs) in clinical practice has encouraged the development of antibody theranostics conjugates (ATCs). However, the generation of homogeneous and pharmaceutically-acceptable ATCs remains a major challenge. The aim of this study is to detect and eliminate ovarian cancer cells on-demand using an ATC directed to EGFR.

METHODS

An ATC with a defined drug-to-antibody ratio was generated by the site-directed conjugation of IRDye®700 to a self-labeling protein (SNAP-tag) fused to an EGFR-specific antibody fragment (scFv-425).

RESULTS

In vitro and ex vivo imaging showed that the ATC based on scFv-425 is suitable for the highly specific detection of EGFR⁺ ovarian cancer cell, human tissues and ascites samples. The construct was also able to eliminate EGFR⁺ cells and human ascites cells with IC₅₀ values of 45-66 nM and 40-90 nM, respectively.

CONCLUSION

Our experiments provide a framework to create a versatile technology platform for the development of ATCs for precise detection and treatment of ovarian cancer cells.