Anti-HER2 Affibody-Conjugated Photosensitizer for Tumor Targeting Photodynamic Therapy

Efficient Tumor-Targeted Photosensitizer Based on Nanobody-Coupled Pyropheophorbide-a for Precise Photodynamic Therapy of Tumors

The use of antibody-coupled photosensitizers is a promising strategy for tumor-targeted photodynamic therapy (PDT). However, some inherent disadvantages, including poor permeability into solid tumors, a long circulation half-life and random coupling of antibodies and photosensitizers, pose problems for their clinical application. In this study, we proposed an improved design for antibody-coupled photosensitizers based on microbial transglutaminase (mTGase)-catalyzed site-specific coupling of a small-sized nanobody with a stable and easily available photosensitive moiety, pyropheophorbide-a (Pyro), to obtain the NHER2-PEG-Pyro conjugate, in which the high hydrophobicity of Pyro was alleviated by introducing a hydrophilic polyethylene glycol (PEG) chain. In vitro and in vivo experiments confirmed that NHER2-PEG-Pyro had excellent binding selectivity and photodynamic activity toward highly HER2-expressing tumor cells, strongly accumulated in highly HER2-expressing tumor tissues, and eliminated highly HER2-expressing NCI-N87 tumors at a relatively low dose (20 nmol/mouse) as a single therapy. This work demonstrated the excellent therapeutic ability of this nanobody-coupled photosensitizer and highlighted the potential of Pyro as an alternative to IRDye 700DX in the development of tumor-targeted photosensitizers. The advantages of the nanobody and Pyro, along with their site-specific conjugation, confer the conjugate with good potential for clinical application.

Anti-breast cancer activity of a novel genetically engineered fusion protein composed of HER2 affibody and proapoptotic peptide R8-KLA

HER2-positive breast cancer is an aggressive subtype with unfavorable prognoses. Although HER2-targeted agents represented by monoclonal antibodies have achieved remarkable success in the clinic, there are still a substantial number of patients with disease relapse. Recently, multifunctional fusion proteins obtained via genetic engineering technology have received much attention in targeted tumor therapy, especially in breast cancer. In this study, we genetically engineered a novel recombinant fusion protein, named HMK, which was designed as a bifunctional construct including the HER2-specific affibody ZHER2:342 for targeted receptor recognition, and a proapoptotic module featuring a cell-penetrating octa-arginine (R8) motif conjugated to an antimicrobial peptide KLA. High-purity HMK proteins were successfully obtained using E. coli expression system and Ni-Nitrilotriacetic acid affinity purification method. HMK exhibited higher cytotoxicity in HER2-positive breast cancer cells SK-BR-3 (IC50 of 8.36 ± 0.62 μM) compared to normal breast epithelial cells MCF-10A (IC50 of 32.40 ± 2.93 μM), demonstrating favorable selectivity. HMK induced apoptosis in SK-BR-3 cells via activating both endogenous and exogenous apoptotic pathways, as evidenced by the cleavage of Caspase 8, Caspase 9, Caspase 3, and PARP. Caspase inhibitor Z-VAD significantly reversed the function of HMK in SK-BR-3 cells, suggesting that caspase-dependent apoptosis was crucial for the anti-breast cancer activity of HMK. Our results suggested that HMK protein may have the potential to become a candidate molecule for HER2-positive breast cancer treatment.

Developing Chlorin/Arylaminoquinazoline Conjugates with Nanomolar Activity for Targeted Photodynamic Therapy: Design, Synthesis, SAR, and Biological Evaluation

In this report, we developed novel chlorin/arylaminoquinazoline conjugates for targeted photodynamic therapy of cancer. The synthesized photosensitizers consisted of chlorin-e6 metallocomplexes (Zn, In, or Pd) conjugated with arylaminoquinazoline ligands with high affinity for epidermal growth factor receptors (EGFR). Additionally, the selectivity and antitumor properties of the conjugates were investigated in the EGFR-expressing A431 human tumor cell line in vitro. Among the tested molecules, the In-containing conjugate effectively inhibited tumor cell proliferation at nanomolar concentrations, a rare property for conventional photosensitizers. In in vivo experiments, the conjugates rapidly accumulated at the tumor site in nude mice bearing A431 xenograft tumors. Subsequent distribution analysis among different tissues was carried out using fluorescence imaging and elemental analysis. Finally, we demonstrated that the most promising In-containing conjugate was capable of inhibiting xenograft tumor growth in mice through combinational therapy. This therapeutic approach, combined with the conjugate's confirmed safety profile, highlights its potential for effective and safe cancer treatment.

Recent advances of affibody molecules in biomedical applications

Affibody molecules are 58-amino-acid peptides with a molecular weight of about 6.5 kDa, derived from the Z domain of Staphylococcal Protein A. Since they have been used as substitutes for antibodies in biomedicine, several therapeutic affibody molecules have been developed for clinical use. Additionally, affibody molecules have been designed for a range of different applications. This review focuses on the progress made in the last five years in the field of affibody molecules and their potential uses in medical imaging, especially in oncology and cancer treatment. It covers areas such as molecular imaging, targeted delivery of toxic drugs, and their use in combination with nanoparticles. We also highlight some current biomedical applications where affibody molecules are commonly used as a "guide." Due to their many advantages, affibody molecules offer significant potential for applications in both biochemical and medical fields.

Nanostructures as Photothermal Agents in Tumor Treatment

Traditional methods of tumor treatment such as surgical resection, chemotherapy, and radiation therapy have certain limitations, and their treatment effects are not always satisfactory. As a new tumor treatment method, photothermal therapy based on nanostructures has attracted the attention of researchers due to its characteristics of minimally invasive, low side effects, and inhibition of cancer metastasis. In recent years, there has been a variety of inorganic or organic nanostructures used in the field of photothermal tumor treatment, and they have shown great application prospects. In this paper, the advantages and disadvantages of a variety of nanomaterials/nanostructures as photothermal agents (PTAs) for photothermal therapy as well as their research progress are reviewed. For the sake of clarity, the recently reported nanomaterials/nanostructures for photothermal therapy of tumor are classified into five main categories, i.e., carbon nanostructures, noble metal nanostructures, transition metal sulfides, organic polymer, and other nanostructures. In addition, future perspectives or challenges in the related field are discussed.

Phage Display Affibodies Combined with AuNPs@Ru(bpy)32+ for Ultra-Sensitive Electrochemiluminescence Detection of Abrin

Abrin is a cytotoxin with strong lethality, which is a serious threat to human health and public safety, and thus, highly sensitive detection methods are urgently needed. The phage display affibody has two major modules, among which, the affibody fragment, with small molecular weight, high affinity and easy preparation, can be used for the specific recognition of the target, and the phage shell, with numerous protein copies, can be used as a carrier for the massive enrichment of signal molecules, and thus is particularly suitable as a sensitive probe for signal amplification in high-sensitivity biosensors. In this study, with antibody-coated magnetic microspheres as capture probes, Ru(bpy)32+ and biotin dual-labeled phage display affibodies as the specific signal probes and AuNPs@Ru(bpy)32+ (Ru(bpy)32+-coated gold nanoparticles) as the signal amplification nanomaterials, a new electrochemiluminescence (ECL) biosensor with a four-level sandwich structure of “magnetic capture probe-abrin-phage display affibody-AuNPs@Ru(bpy)32+” was constructed for abrin detection. In this detection mode, AuNPs@Ru(bpy)32+, a gold nanocomposite prepared rapidly via electrical interaction, contained an extremely high density of signal molecules, and the phage display affibodies with powerful loading capacity were not only labeled with Ru(bpy)32+, but also enriched with AuNPs@Ru(bpy)32+ in large amounts. These designs greatly improved the detection capability of the sensor, ultimately achieving the ultra-sensitive detection of abrin. The limit of detection (LOD) was 4.1 fg/mL (3δ/S), and the quantification range was from 5 fg/mL to 5 pg/mL. The sensor had good reproducibility and specificity and performed well in the test of simulated samples. This study expanded the application of affibodies in the field of biosensing and also deeply explored the signal amplification potential of phage display technology, which is of high value for the construction of simple and efficient sensors with high sensitivity.

Targeted photoimmunotherapy for cancer

Photodynamic therapy (PDT) is a clinically approved procedure that can exert a curative action against malignant cells. The treatment implies the administration of a photoactive molecular species that, upon absorption of visible or near infrared light, sensitizes the formation of reactive oxygen species. These species are cytotoxic and lead to tumor cell death, damage vasculature, and induce inflammation. Clinical investigations demonstrated that PDT is curative and does not compromise other treatment options. One of the major limitations of the original method was the low selectivity of the photoactive compounds for malignant over healthy tissues. The development of conjugates with antibodies has endowed photosensitizing molecules with targeting capability, so that the compounds are delivered with unprecedented precision to the site of action. Given their fluorescence emission capability, these supramolecular species are intrinsically theranostic agents.

Photomedicine based on heme-derived compounds

Photoimaging and phototherapy have become major platforms for the diagnosis and treatment of various health complications. These applications require a photosensitizer (PS) that is capable of absorbing light from a source and converting it into other energy forms for detection and therapy. While synthetic inorganic materials such as quantum dots and gold nanorods have been widely explored for their medical diagnosis and photodynamic (PDT) and photothermal (PTT) therapy capabilities, translation of these technologies has lagged, primarily owing to potential cytotoxicity and immunogenicity issues. Of the various photoreactive molecules, the naturally occurring endogenous compound heme, a constituent of red blood cells, and its derivatives, porphyrin, biliverdin and bilirubin, have shown immense potential as noteworthy candidates for clinically translatable photoreactive agents, as evidenced by previous reports. While porphyrin-based photomedicines have attracted significant attention and are well documented, research on photomedicines based on two other heme-derived compounds, biliverdin and bilirubin, has been relatively lacking. In this review, we summarize the unique photoproperties of heme-derived compounds and outline recent efforts to use them in biomedical imaging and phototherapy applications.

Emerging strategies in developing multifunctional nanomaterials for cancer nanotheranostics

Cancer involves a collection of diseases with a common trait - dysregulation in cell proliferation. At present, traditional therapeutic strategies against cancer have limitations in tackling various tumors in clinical settings. These include chemotherapeutic resistance and the inability to overcome intrinsic physiological barriers to drug delivery. Nanomaterials have presented promising strategies for tumor treatment in recent years. Nanotheranostics combine therapeutic and bioimaging functionalities at the single nanoparticle level and have experienced tremendous growth over the past few years. This review highlights recent developments of advanced nanomaterials and nanotheranostics in three main directions: stimulus-responsive nanomaterials, nanocarriers targeting the tumor microenvironment, and emerging nanomaterials that integrate with phototherapies and immunotherapies. We also discuss the cytotoxicity and outlook of next-generation nanomaterials towards clinical implementation.

Improving Targeted Delivery and Antitumor Efficacy with Engineered Tumor Necrosis Factor-Related Apoptosis Ligand-Affibody Fusion Protein

Tumor necrosis factor-related apoptosis ligand (TRAIL) is a promising protein candidate for selective apoptosis of a variety of cancer cells. However, the short half-life and a lack of targeted delivery are major obstacles for its application in cancer therapy. Here, we propose a simple strategy to solve the targeting problem by genetically fusing an anti-HER2 affibody to the C-terminus of the TRAIL. The fusion protein TRAIL-affibody was produced as a soluble form with high yield in recombinant Escherichia coli. In vitro studies proved that the affibody domain promoted the cellular uptake of the fusion protein in the HER2 overexpressed SKOV-3 cells and improved its apoptosis-inducing ability. In addition, the fusion protein exhibited higher accumulation at the tumor site and greater antitumor effect than those of TRAIL in vivo, indicating that the affibody promoted the tumor homing of the TRAIL and then improved the therapeutic efficacy. Importantly, repeated injection of high-dose TRAIL-affibody showed no obvious toxicity in mice. These results demonstrated that the engineered TRAIL-affibody is promising to be a highly tumor-specific and targeted cancer therapeutic agent.

Gene silencing delivery systems for the treatment of pancreatic cancer: Where and what to target next?

Despite intensive research efforts and development of numerous new anticancer drugs and treatment strategies over the past decades, there has been only very limited improvement in overall patient survival and in effective treatment options for pancreatic cancer. Current chemotherapy improves survival in terms of months and death rates in pancreatic cancer patients are almost equivalent to incidence rates. It is imperative to develop new therapeutic approaches. Among them, gene silencing shows promise of effectiveness in both tumor cells and stromal cells by inhibiting tumor-promoting genes. This review summarizes potential targets for gene silencing in both pancreatic cancer cells and abundant stromal cells focusing on non-viral delivery systems for small RNAs and discusses the potential immunological implications. The review concludes with the importance of multifactorial therapy of pancreatic cancer.

Current strategies for the discovery and bioconjugation of smaller, targetable drug conjugates tailored for solid tumor therapy

Introduction: Antibody-Drug Conjugates (ADCs) have undergone a recent resurgence with 5 product approvals over the last 2 years but for those close to the field, it's been repeated cycles of setbacks and new innovations. A new wave of innovation is in the type of format used to deliver the cytotoxic payloads, with smaller bio-molecules being designed to have more optimal penetration and elimination properties tailored for solid tumors.Areas covered: In this review, the authors cover many of the recently described smaller-format drug conjugates (including formats such as diabodies, Fabs, scFvs, domain antibodies) with an emphasis on the types of conjugation technologies used to attach the chemical linker-payload.Expert opinion: Smaller formats are highly influenced by the structure of the linker-payload, arguably more-so than larger ADCs, so careful consideration is needed where solublising and pharmacokinetic modulation is required. High-quality conjugates are being developed with in vivo tumor efficacy and tolerability properties competitive with ADCs and with a few formats already in clinical development, we expect the pipeline to expand and to reach the market.

Tackling solid tumour therapy with small-format drug conjugates

The pharmacokinetic-pharmacodynamic relationship is extremely complex and tumour drug penetration is one key parameter influencing therapeutic efficacy. In the context of antibody-drug conjugates (ADCs), which has undergone many innovation cycles and witnessed many failures, this feature is being addressed by a number of alternative technologies. Immunoglobulin-based ADCs continue to dominate the industrial landscape, but smaller formats offer the promise of more-effective cytotoxic payload delivery to solid tumours, with a higher therapeutic window afforded by the more rapid clearance. To make these smaller formats viable as delivery vehicles, a number of strategies are being employed, which will be reviewed here. These include identifying the most-appropriate size to generate the larger therapeutic window, increasing the amount of functional, cytotoxic payload delivered through conjugation or half-life extending technologies or other ways of extending the dosing without inducing toxicity.

Current Targets and Bioconjugation Strategies in Photodynamic Diagnosis and Therapy of Cancer

Photodynamic diagnosis (PDD) and therapy (PDT) are emerging, non/minimally invasive techniques for cancer diagnosis and treatment. Both techniques require a photosensitizer and light to visualize or destroy cancer cells. However, a limitation of conventional, non-targeted PDT is poor selectivity, causing side effects. The bioconjugation of a photosensitizer to a tumor-targeting molecule, such as an antibody or a ligand peptide, is a way to improve selectivity. The bioconjugation strategy can generate a tumor-targeting photosensitizer conjugate specific for cancer cells, or ideally, for multiple tumor compartments to improve selectivity and efficacy, such as cancer stem cells and tumor neovasculature within the tumor microenvironment. If successful, such targeted photosensitizer conjugates can also be used for specific visualization and detection of cancer cells and/or tumor angiogenesis (an early event in tumorigenesis) with the hope of an early diagnosis of cancer. The purpose of this review is to summarize some current promising target molecules, e.g., tissue factor (also known as CD142), and the currently used bioconjugation strategies in PDT and PDD, with a focus on newly developed protein photosensitizers. These are genetically engineered photosensitizers, with the possibility of generating a fusion protein photosensitizer by recombinant DNA technology for both PDT and PDD without the need of chemical conjugation. We believe that providing an overview of promising targets and bioconjugation strategies will aid in driving research in this field forward towards more effective, less toxic, and non- or minimally invasive treatment and diagnosis options for cancer patients.