The development of immunoconjugates for targeted cancer therapy

A Comprehensive Analysis of Biopharmaceutical Products Listed in the FDA's Purple Book

Although biopharmaceuticals constitute around 10% of the drug landscape, eight of the ten top-selling products were biopharmaceuticals in 2023. This study did a comprehensive analysis of the FDA's Purple Book database. Firstly, our research uncovered market trends and provided insights into biologics distributions. According to the investigation, although biotechnology has advanced and legislative shifts have made the approval process faster, there are still challenges to overcome, such as molecular instability and formulation design. Moreover, our research comprehensively analyzed biological formulations, pointing out significant strategies regarding administration routes, dosage forms, product packaging, and excipients. In conjunction with biologics, the widespread integration of innovative delivery strategies will be implemented to confront the evolving challenges in healthcare and meet an expanding array of treatment needs.

Control of polymer-protein interactions by tuning the composition and length of polymer chains

Nanomoduling the 3D shape and chemical functionalities in a synthetic polymer may create recognition cavities for biomacromolecule binding, which serves as an attractive alternative to natural antibodies with much less cost. To obtain fundamental understanding and predict molecular design rules of the polymer antibody, we analyze the complex structure between the biomarker protein epithelial cell adhesion molecule (EpCAM) and a series of polymer ligands via molecular dynamics (MD) simulations. For monomeric ligands, strong enrichment of aromatic residues in protein binding sites is revealed, in line with the reported observations for natural antibodies. Yet, for linear polymers with a growing degree of polymerization, for the first time, a drastic change is revealed on the type of enriched protein residues and the location of protein binding sites, driven by the increasing steric hindrance effect that makes the adsorption of the polymer in the protein exterior feasible. Varying the polymer length and monomeric composition also significantly affects the ligand binding affinity. Here, we have captured three distinct dependences of the ligand binding free energy on the degree of polymerization: for NIPAm based hydrophilic polymers, TBAm dominated hydrophobic polymers and AAc dominated charged polymers. These results can be rationalized by the complex structure and the composition of protein residues at the binding interface. The entire analysis demonstrates unique binding features for polymer ligands and the possibility to modulate their binding sites and affinity by engineering the polymer structure.

Specific peptide conjugation to a therapeutic antibody leads to enhanced therapeutic potency and thermal stability by reduced Fc dynamics

Antibody-drug conjugates are powerful tools for combatting a wide array of cancers. Drug conjugation to a therapeutic antibody often alters molecular characteristics, such as hydrophobicity and effector function, resulting in quality deterioration. To develop a drug conjugation methodology that maintains the molecular characteristics of the antibody, we engineered a specific peptide for conjugation to the Fc region. We used trastuzumab and the chelator (DOTA) as model antibody and payload, respectively. Interestingly, peptide/DOTA-conjugated trastuzumab exhibited enhanced antibody-dependent cellular cytotoxicity (ADCC) and increased thermal stability. Detailed structural and thermodynamic analysis clarified that the conjugated peptide blocks the Fc dynamics like a "wedge." We revealed that (1) decreased molecular entropy results in enhanced ADCC, and (2) blockade of Fc denaturation results in increased thermal stability. Thus, we believe that our methodology is superior not only for drug conjugation but also as for reinforcing therapeutic antibodies to enhance ADCC and thermal stability.

Immunoconjugates and bispecific antibodies: Trends in therapeutic success and commercial focus

Monoclonal antibodies (mAbs) have revolutionized the selective targeting of disease, as well as changing the character of the pharmaceutical industry. Although most attention has focused on conventional antibodies, immunoconjugates and bispecific antibodies (bsAbs) are beginning to show greater potential. Herein, we identify trends in the development and approval of antibody derivatives, as well as the organizations developing these products. Whereas industry development of immunoconjugates has grown steadily over four decades, momentum behind bispecific agents has seemingly expanded only recently. Together, our findings suggest that antibody derivatives provide interesting, albeit still speculative, opportunities for targeted interventions.

Dissecting Immunotherapy Strategies for Small Cell Lung Cancer: Antibodies, Ionizing Radiation and CAR-T

Small cell lung cancer (SCLC) is a highly aggressive malignancy that accounts for about 14% of all lung cancers. Platinum-based chemotherapy has been the only available treatment for a long time, until the introduction of immune checkpoint inhibitors (ICIs) recently changed first-line standard of care and shed light on the pivotal role of the immune system. Despite improved survival in a subset of patients, a lot of them still do not benefit from first-line chemo-immunotherapy, and several studies are investigating whether different combination strategies (with both systemic and local treatments, such as radiotherapy) may improve patient outcomes. Moreover, research of biomarkers that may be used to predict patients' outcomes is ongoing. In addition to ICIs, immunotherapy offers other different strategies, including naked monoclonal antibodies targeting tumor associated antigens, conjugated antibody, bispecific antibodies and cellular therapies. In this review, we summarize the main evidence available about the use of immunotherapy in SCLC, the rationale behind combination strategies and the studies that are currently ongoing in this setting, in order to give the reader a clear and complete view of this rapidly expanding topic.

Preliminary Development and Testing of C595 Radioimmunoconjugates for Targeting MUC1 Cancer Epitopes in Pancreatic Ductal Adenocarcinoma

Mucin 1 is a transmembrane glycoprotein which overexpresses cancer-specific epitopes (MUC1-CE) on pancreatic ductal adenocarcinoma (PDAC) cells. As PDAC is a low survival and highly aggressive malignancy, developing radioimmunoconjugates capable of targeting MUC1-CE could lead to improvements in PDAC outcomes. The aim of this study was to develop and perform preliminary testing of diagnostic and therapeutic radioimmunoconjugates for PDAC using an anti-MUC1 antibody, C595. Firstly, p-SCN-Bn-DOTA was conjugated to the C595 antibody to form a DOTA-C595 immunoconjugate. The stability and binding affinity of the DOTA-C595 conjugate was evaluated using mass spectrometry and ELISA. DOTA-C595 was radiolabelled to Copper-64, Lutetium-177, Gallium-68 and Technetium-99m to form novel radioimmunoconjugates. Cell binding assays were performed in PANC-1 (strong MUC1-CE expression) and AsPC-1 (weak MUC1-CE expression) cell lines using ⁶⁴Cu-DOTA-C595 and ¹⁷⁷Lu-DOTA-C595. An optimal molar ratio of 4:1 DOTA groups per C595 molecule was obtained from the conjugation process. DOTA-C595 labelled to Copper-64, Lutetium-177, and Technetium-99m with high efficiency, although the Gallium-68 labelling was low. ¹⁷⁷Lu-DOTA-C595 demonstrated high cellular binding to the PANC-1 cell lines which was significantly greater than AsPC-1 binding at concentrations exceeding 100 nM (p < 0.05). ⁶⁴Cu-DOTA-C595 showed similar binding to the PANC-1 and AsPC-1 cells with no significant differences observed between cell lines (p > 0.05). The high cellular binding of ¹⁷⁷Lu-DOTA-C595 to MUC1-CE positive cell lines suggests promise as a therapeutic radioimmunoconjugate against PDAC while further work is required to harness the potential of ⁶⁴Cu-DOTA-C595 as a diagnostic radioimmunoconjugate.

Directing ricin-based immunotoxins with targeting affibodies and KDEL signal peptide to cancer cells effectively induces apoptosis and tumor suppression

The plant toxin ricin, especially its cytotoxic A chain (RTA), can be genetically engineered with targeting ligands to develop specific anti-cancer recombinant immunotoxins (RITs). Here, we used affibody molecules targeting two cancer biomarkers, the receptors HER2 and EGFR, along with the KDEL signal peptide to construct two cancer-specific ricin-based RITs, HER2Afb-RTA-KDEL and EGFRAfb-RTA-KDEL. The affibodies successfully provided target-specificity and subsequent receptor-mediated endocytosis and the KDEL signal peptide routed the RITs through the retrograde transport pathway, effectively delivering RTA to the cytosol as well as avoiding the alternate recycling pathway that typical cancer cells frequently have. The in vivo efficacy of RITs was enhanced by introducing the albumin binding domain (AlBD) to construct AlBD/HER2Afb/RTA-KDEL. Systemic administration of AlBD-containing RITs to tumor-bearing mice significantly suppressed tumor growth without any noticeable side-effects. Collectively, combining target-selective affibody molecules, a cytotoxic RTA, and an intracellularly designating peptide, we successfully developed cancer-specific and efficacious ricin-based RITs. This approach can be applied to develop novel protein-based “magic bullets” to effectively suppress tumors that are resistant to conventional anti-cancer drugs.

Near‐infrared‐induced drug release from antibody–drug double conjugates exerts a cytotoxic photo‐bystander effect

Ideal cancer treatments specifically target and eradicate tumor cells without affecting healthy cells. Therefore, antibody‐based therapies that specifically target cancer antigens can be considered ideal cancer therapies. Antibodies linked with small‐molecule drugs (i.e., antibody–drug conjugates [ADCs]) are widely used in clinics as antibody‐based therapeutics. However, because tumors express antigens heterogeneously, greater target specificity and stable binding of noncleavable linkers in ADCs limit their antitumor effects. To overcome this problem, strategies, including decreasing the binding strength, conjugating more drugs, and targeting tumor stroma, have been applied, albeit with limited success. Thus, further technological advancements are required to remotely control the ADCs. Here, we described a drug that is photo‐releasable from an ADC created via simple double conjugation and its antitumor effects both on target and nontarget tumor cells. Specifically, noncleavable T‐DM1 was conjugated with IR700DX to produce T‐DM1‐IR700. Although T‐DM1‐IR700 itself is noncleavable, with NIR‐light irradiation, it can release DM1‐derivatives which elicited antitumor effect in vitro mixed culture and in vivo mixed tumor model which are mimicking heterogeneous tumor‐antigen expression same as real clinical tumors. This cytotoxic photo‐bystander effect occurred in various types mixed cultures in vitro, and changing antibodies also exerted photo‐bystander effects, suggesting that this technology can be used for targeting various specific cancer antigens. These findings can potentially aid the development of strategies to address challenges associated with tumor expression of heterogeneous antigen.

Antibody-drug conjugates: beyond current approvals and potential future strategies

The recent approvals for antibody-drug conjugates (ADCs) in multiple malignancies in recent years have fuelled the ongoing development of this class of drugs. These novel agents combine the benefits of high specific targeting of oncogenic cell surface antigens with the additional cell kill from high potency cytotoxic payloads, thus achieving wider therapeutic windows. This review will summarise the clinical activity of ADCs in tumour types not covered elsewhere in this issue, such as gastrointestinal (GI) and genitourinary (GU) cancers and glioblastoma (GBM). In addition to the ongoing clinical testing of existing ADCs, there is substantial preclinical and early phase testing of newer ADCs or ADC incorporating strategies. This review will provide selected insights into such future development, focusing on the development of novel ADCs against new antigen targets in the tumour microenvironment (TME) and combination of ADCs with immuno-oncology (IO) agents.

Engineered Bifunctional Proteins for Targeted Cancer Therapy: Prospects and Challenges

Bifunctional proteins (BFPs) are a class of therapeutic agents produced through genetic engineering and protein engineering, and are increasingly used to treat various human diseases, including cancer. These proteins usually have two or more biological functions-specifically recognizing different molecular targets to regulate the related signaling pathways, or mediating effector molecules/cells to kill tumor cells. Unlike conventional small-molecule or single-target drugs, BFPs possess stronger biological activity but lower systemic toxicity. Hence, BFPs are considered to offer many benefits for the treatment of heterogeneous tumors. In this review, the authors briefly describe the unique structural feature of BFP molecules and innovatively divide them into bispecific antibodies, cytokine-based BFPs (immunocytokines), and protein toxin-based BFPs (immunotoxins) according to their mode of action. In addition, the latest advances in the development of BFPs are discussed and the potential limitations or problems in clinical applications are outlined. Taken together, future studies need to be centered on understanding the characteristics of BFPs for optimizing and designing more effective such drugs.

Antibody-Based Immunotoxins for Colorectal Cancer Therapy

Monoclonal antibodies (mAbs) are included among the treatment options for advanced colorectal cancer (CRC). However, while these mAbs effectively target cancer cells, they may have limited clinical activity. A strategy to improve their therapeutic potential is arming them with a toxic payload. Immunotoxins (ITX) combining the cell-killing ability of a toxin with the specificity of a mAb constitute a promising strategy for CRC therapy. However, several important challenges in optimizing ITX remain, including suboptimal pharmacokinetics and especially the immunogenicity of the toxin moiety. Nonetheless, ongoing research is working to solve these limitations and expand CRC patients' therapeutic armory. In this review, we provide a comprehensive overview of targets and toxins employed in the design of ITX for CRC and highlight a wide selection of ITX tested in CRC patients as well as preclinical candidates.

Extending traditional antibody therapies: Novel discoveries in immunotherapy and clinical applications

Immunotherapy has been well regarded as one of the safer and antigen-specific anti-cancer treatments compared to first-generation chemotherapy. Since Coley's discovery, researchers focused on engineering novel antibody-based therapies. Including artificial and modified antibodies, such as antibody fragments, antibody-drug conjugates, and synthetic mimetics, the variety of immunotherapy has been rapidly expanding in the last few decades. Genetic and chemical modifications to monoclonal antibody have been brought into academia, in vivo trials, and clinical applications. Here, we have looked around antibodies overall. First, we elucidate the antibody structure and its cytotoxicity mechanisms. Second, types of therapeutic antibodies are presented. Additionally, there is a summarized list of US Food and Drug Administration (FDA)-approved therapeutic antibodies and recent clinical trials. This review provides a comprehensive overview of both the general function of therapeutic antibodies and a few main variations in development, including recent advent with the proposed mechanism of actions, and we introduce types of therapeutic antibodies, clinical trials, and approved commercial immunotherapeutic drugs.

Genetics and Inflammation in Endometriosis: Improving Knowledge for Development of New Pharmacological Strategies

According to a rich body of literature, immune cell dysfunctions, both locally and systemically, and an inflammatory environment characterize all forms of endometriosis. Alterations in transcripts and proteins involved in the recruitment of immune cells, in the interaction between cytokines and their receptors, cellular adhesion and apoptosis have been demonstrated in endometriotic lesions. The objective of this narrative review is to provide an overview of the components and mechanisms at the intersection between inflammation and genetics that may constitute vanguard therapeutic approaches in endometriosis. The GWAS technology and pathway-based analysis highlighted the role of the MAPK and the WNT/β-catenin cascades in the pathogenesis of endometriosis. These signaling pathways have been suggested to interfere with the disease establishment via several mechanisms, including apoptosis, migration and angiogenesis. Extracellular vesicle-associated molecules may be not only interesting to explain some aspects of endometriosis progression, but they may also serve as therapeutic regimens per se. Immune/inflammatory dysfunctions have always represented attractive therapeutic targets in endometriosis. These would be even more interesting if genetic evidence supported the involvement of functional pathways at the basis of these alterations. Targeting these dysfunctions through next-generation inhibitors can constitute a therapeutic alternative for endometriosis.

An Engineered Arginine Residue of Unusual pH-Sensitive Reactivity Facilitates Site-Selective Antibody Conjugation

Monoclonal antibody h38C2 is a humanized catalytic antibody that has been used to generate various immunoconjugate species such as chemically programmed antibodies, antibody-drug conjugates, and antibody-siRNA conjugates. Highly efficient and specific conjugation of h38C2 occurs at its uniquely reactive lysine (Lys) residue buried inside the antibody's catalytic pocket. We recently reported the rational mutation of this Lys residue at position 99 in the heavy chain variable domain to an arginine (Arg) residue. The Lys99Arg mutation can be site-selectively conjugated with molecules containing a hapten-like triazolyl-phenylglyoxal (TPG) unit. Here we show that this conjugation is facilitated by the unusual pH-sensitive reactivity of the Arg99 residue, consistent with an indirectly measured pKa of 5.2. The Arg99/TPG conjugation holds promise to further expand the versatility of the h38C2 conjugation platform, such as for the generation of antibody conjugates with dual payloads.

Intracellular targeting of STIP1 inhibits human cancer cell line growth

BACKGROUND

Extracellular and cell-surface molecules remain the most common druggable cancer targets. However, intracellular therapeutic modalities are gaining momentum. The overexpression of stress-induced phosphoprotein 1 (STIP1), an adaptor protein that coordinates the functions of different chaperones in protein folding, has been reported in several solid malignancies. Here, we investigated the effects of intracellular STIP1 inhibition, attained either through the HEPES-mediated cytosolic delivery of anti-STIP1 antibodies or the use of a cell-penetrating signal-tagged peptide 520, in different human cancer cell lines and luciferase-expressing murine ovarian cancer cells (MOSEC/Luc) tumor-bearing C57BL/6 mice.

METHODS

The effects of STIP1 in different human cell lines were determined by cell viability, cell cytotoxicity and cell apoptosis assays. Immunoblotting was used to assess the relevant proteins found in this study and tumor xenograft mice models were also employed.

RESULTS

Intracellular targeting of STIP1 inhibited cancer cell line growth and promoted caspase 3-dependent apoptotic cell death. Moreover, the intracellular delivery of anti-STIP1 antibodies facilitated the degradation of STIP1 and two of its client proteins, lysine-specific demethylase 1 and Janus kinase 2. In vivo studies demonstrated that survival of mice bearing experimental tumors was improved by administration of anti-STIP1 antibodies.

CONCLUSIONS

Our findings demonstrate that the cytosolic inhibition of STIP1 in tumor cells is feasible and provides a solid basis for further investigation of STIP1 as an intracellular cancer target. Our findings demonstrate that cytosolic inhibition of STIP1 in tumor cells is feasible and provide a solid basis for further exploration of STIP1 as an intracellular cancer target.

Drug delivery nanocarriers and recent advances ventured to improve therapeutic efficacy against osteosarcoma: an overview

BACKGROUND

Osteosarcoma (OS) is one of the key cancers affecting the bone tissues, primarily occurred in children and adolescence. Recently, chemotherapy followed by surgery and then post-operative adjuvant chemotherapy is widely used for the treatment of OS. However, the lack of selectivity and sensitivity to tumor cells, the development of multi-drug resistance (MDR), and dangerous side effects have restricted the use of chemotherapeutics.

MAIN BODY

There is an unmet need for novel drug delivery strategies for effective treatment and management of OS. Advances in nanotechnology have led to momentous progress in the design of tumor-targeted drug delivery nanocarriers (NCs) as well as functionalized smart NCs to achieve targeting and to treat OS effectively. The present review summarizes the drug delivery challenges in OS, and how organic nanoparticulate approaches are useful in overcoming barriers will be explained. The present review describes the various organic nanoparticulate approaches such as conventional nanocarriers, stimuli-responsive NCs, and ligand-based active targeting strategies tested against OS. The drug conjugates prepared with copolymer and ligand having bone affinity, and advanced promising approaches such as gene therapy, gene-directed enzyme prodrug therapy, and T cell therapy tested against OS along with their reported limitations are also briefed in this review.

CONCLUSION

The nanoparticulate drugs, drug conjugates, and advanced therapies such as gene therapy, and T cell therapy have promising and potential application in the effective treatment of OS. However, many of the above approaches are still at the preclinical stage, and there is a long transitional period before their clinical application.

Non-genetic mechanisms of therapeutic resistance in cancer

Therapeutic resistance continues to be an indominable foe in our ambition for curative cancer treatment. Recent insights into the molecular determinants of acquired treatment resistance in the clinical and experimental setting have challenged the widely held view of sequential genetic evolution as the primary cause of resistance and brought into sharp focus a range of non-genetic adaptive mechanisms. Notably, the genetic landscape of the tumour and the non-genetic mechanisms used to escape therapy are frequently linked. Remarkably, whereas some oncogenic mutations allow the cancer cells to rapidly adapt their transcriptional and/or metabolic programme to meet and survive the therapeutic pressure, other oncogenic drivers convey an inherent cellular plasticity to the cancer cell enabling lineage switching and/or the evasion of anticancer immunosurveillance. The prevalence and diverse array of non-genetic resistance mechanisms pose a new challenge to the field that requires innovative strategies to monitor and counteract these adaptive processes. In this Perspective we discuss the key principles of non-genetic therapy resistance in cancer. We provide a perspective on the emerging data from clinical studies and sophisticated cancer models that have studied various non-genetic resistance pathways and highlight promising therapeutic avenues that may be used to negate and/or counteract the non-genetic adaptive pathways.

Allogeneic Hematopoietic Transplantation for Multiple Myeloma in the New Drugs Era: A Platform to Cure

Allogeneic hematopoietic cell transplantation (alloHCT) represents a treatment option for multiple myeloma (MM) patients. As shown in several studies, alloHCT is highly effective, but it is hampered by a high toxicity, mainly related to the graft-versus-host disease (GVHD), a complex immunological reaction ascribable to the donor’s immune system. The morbidity and mortality associated with GVHD can weaken the benefits of this procedure. On the other side, the high therapeutic potential of alloHCT is also related to the donor’s immune system, through immunological activity known as the graft-versus-myeloma effect. Clinical research over the past two decades has sought to enhance the favorable part of this balance, along with the reduction in treatment-related toxicity. Frontline alloHCT showed promising results and a potential for a cure in the past. Currently, thanks to the improved results of first-line therapies and the availability of effective second- or third-line salvage therapies, alloHCT is reserved for selected high-risk patients and is considered a clinical option. For donor lymphocyte infusion, bortezomib or lenalidomide have been used as consolidation or maintenance therapies post-transplant—none has become standard of care. For those patients who relapse, the best treatment should be evaluated considering the patient’s clinical status and the previous lines of therapy. The use of newer drugs, such as monoclonal antibodies or other immunotherapies in the post-transplant setting, deserves further investigation. However, acceptable toxicity and a synergic effect with the newer immune system could be hopefully expected.

Effect of Chain-End Chemistries on the Efficiency of Coupling Antibodies to Polymers Using Unnatural Amino Acids

Novel conjugates that incorporate strategies for increasing the therapeutic payload, such as targeted polymeric delivery vehicles, have great potential in overcoming limitations of conventional antibody therapies that often exhibit immunogenicity and limited drug loading. Click chemistry has significantly expanded the toolbox of effective strategies for developing hybrid polymer-biomolecule conjugates, however, effective systems require orthogonality between the polymer and biomolecule chemistries to achieve efficient coupling. Here, three cycloaddition-based strategies for antibody conjugation to polymeric carriers are explored and show that a purely radical-based method for polymer synthesis and subsequent biomolecule attachment has a trade-off between coupling efficiency of the antibody and the ability to synthesize polymers with controlled chemical properties. It is shown that careful consideration of both coupling chemistries as well as the potential effect of how this modulates the chemical properties of the polymer nanocarrier should be considered during the development of such systems. The strategies described offer insight into improving conjugate development for therapeutic and theranostic applications. In this system, polymerization using conventional and established reversible addition fragmentation chain transfer (RAFT) agents, followed by multiple post-modification steps, always leads to systems with more defined chemical architectures compared to strategies that utilize alkyne-functional RAFT agents.

Specific Targeting of HER2-Positive Head and Neck Squamous Cell Carcinoma Line HN5 by Idarubicin-ZHER2 Affibody Conjugate

BACKGROUND

Expression of human epidermal growth factor receptor type 2 (HER2) in head and neck squamous cell carcinoma (HNSCC) cell line HN5 can be employed with great opportunities of success for specific targeting of anti-cancer chemotherapeutic agents.

OBJECTIVE

In the current study, HER2-specific affibody molecule, ZHER2:342 (an engineered protein with great affinity for HER2 receptors) was selected for conjugation to idarubicin (an anti-neoplastic antibiotic).

METHOD

ZHER2:342 affibody gene with one added cysteine code at the its 5' end was synthesized de novo and then inserted into pET302 plasmid and transferred to E. Coli BL21 hosting system. After induction of protein expression, the recombinant ZHER2 affibody molecules were purified using Ni- NTA resin and purity was analyzed through SDS-PAGE. Affinity-purified affibody molecules were conjugated to idarubicin through a heterobifunctional crosslinker, sulfosuccinimidyl 4-(Nmaleimidomethyl) cyclohexane-1-carboxylate (Sulfo-SMCC). Specific toxicity of idarubicin-ZHER2 affibody conjugate against two HER2-positive cells, HN5 and MCF-7 was assessed through MTT assay after an exposure time of 48 hours with different concentrations of conjugate.

RESULTS

Idarubicin in the non-conjugated form showed potent toxic effects against both cell lines, while HN5 cells were significantly more sensitive compared to MCF-7 cells. Dimeric ZHER2 affibody showed a mild decreasing effect on growth of both HN5 and MCF-7 cells at optimum concentration. Idarubicin-ZHER2 affibody conjugate at an optimum concentration reduced viability of HN5 cell line more efficiently compared to MCF-7 cell line.

CONCLUSION

In conclusion, idarubicin-ZHER2 affibody conjugate in optimum concentrations can be used for specific targeting and killing of HN5 cells.

Evaluating the Combination of Radioimmunotherapy and Immunotherapy in a Melanoma Mouse Model

Immunotherapy has changed the oncology landscape during the last decade and become standard of care for several cancers. The combinations of immunotherapy with other treatment modalities are also being investigated. One of the challenges to investigate such combinations is to identify suitable mouse models for the pre-clinical experiments. In the past, we and other researchers showed that murine B16-F10 melanoma in C57Bl6 mice is refractory to treatment with immune checkpoint inhibitors. In this work we studied the suitability of an alternative syngeneic model, Cloudman S91 murine melanoma in DBA/2 mouse (DBA/2NCrl), to study the combination of immunotherapy targeting PD-1 and radioimmunotherapy targeting melanin. DBA/2 male and female mice were injected subcutaneously with 3-6 million Cloudman S91 cells. When the tumors reached ~150 mm³ volume, the animals were treated intraperitoneally with PBS (sham), h8C3 unlabeled (cold) antibody to melanin, immunotherapy with anti-PD-1 antibody, radioimmunotherapy with 213Bismuth (²¹³Bi)-labeled h8C3 antibody, or several combinations of immunotherapy and radioimmunotherapy. Treatments with immunotherapy alone produced very modest effect on the tumor size, while combination therapy resulted in significant slowing down of the tumor growth, increased animal survival, and no decrease in animal body weight. We conclude that Cloudman S91 murine melanoma in DBA/2 mouse is a suitable model to evaluate combination of immunotherapy of melanoma with tangentially targeted treatments.

Development of Human Monoclonal Antibody for Claudin-3 Overexpressing Carcinoma Targeting

Most malignant tumors originate from epithelial tissues in which tight junctions mediate cell-cell interactions. Tight junction proteins, especially claudin-3 (CLDN3), are overexpressed in various cancers. Claudin-3 is exposed externally during tumorigenesis making it a potential biomarker and therapeutic target. However, the development of antibodies against specific CLDN proteins is difficult, because CLDNs are four-transmembrane domain proteins with high homology among CLDN family members and species. Here, we developed a human IgG1 monoclonal antibody (h4G3) against CLDN3 through scFv phage display using CLDN3-overexpressing stable cells and CLDN3-embedded lipoparticles as antigens. The h4G3 recognized the native conformation of human and mouse CLDN3 without cross-reactivity to other CLDNs. The binding kinetics of h4G3 demonstrated a sub-nanomolar affinity for CLDN3 expressed on the cell surface. The h4G3 showed antibody-dependent cellular cytotoxicity (ADCC) according to CLDN3 expression levels in various cancer cells by the activation of FcγRIIIa (CD16a). The biodistribution of h4G3 was analyzed by intravenous injection of fluorescence-conjugated h4G3 which showed that it localized to the tumor site in xenograft mice bearing CLDN3-expressing tumors. These results indicate that h4G3 recognizes CLDN3 specifically, suggesting its value for cancer diagnosis, antibody-drug conjugates, and potentially as a chimeric antigen receptor (CAR) for CLDN3-expressing pan-carcinoma.

Reinforcing the primary immunotherapy modulators against acute leukemia; monoclonal antibodies in AML

Recent therapeutic advances in cancer treatment recruit immune system potentiation against malignant cells. Numerous ongoing clinical trials on immunotherapy methods, either monotherapy or combination therapy, are investigating the impeding factors on the way of acute myeloid leukemia (AML) treatment. Due to the genetic diversity in AML progenitors, combining various strategies is more likely to be useful for improving patient outcomes. This review describes the details of applying monoclonal antibodies against AML, focusing on CD33, CD123, FLT3, CD45 and CD66 targeting. Furthermore, it clarifies the importance of immunotoxins, bispecific antibodies, chimeric antigen receptor (CAR)-T cells and T cell receptor-modified cells as reinforcing agents for monoclonal antibodies.

Opportunities and Challenges for Antibodies against Intracellular Antigens

Therapeutic antibodies are one most significant advances in immunotherapy, the development of antibodies against disease-associated MHC-peptide complexes led to the introduction of TCR-like antibodies. TCR-like antibodies combine the recognition of intracellular proteins with the therapeutic potency and versatility of monoclonal antibodies (mAb), offering an unparalleled opportunity to expand the repertoire of therapeutic antibodies available to treat diseases like cancer. This review details the current state of TCR-like antibodies and describes their production, mechanisms as well as their applications. In addition, it presents an insight on the challenges that they must overcome in order to become commercially and clinically validated.

Expression, purification, and characterization of the native intracellular domain of human epidermal growth factor receptors 1 and 2 in Escherichia coli

Human epidermal growth factor receptors (EGFR) are an important target in drug discovery in terms of both protein-small-molecule interactions and protein-protein interactions. In this work, the isolation of a stable soluble protein of the tyrosine kinase domain of EGFR in Escherichia coli expression has been accomplished. This successful study presents the expression and purification conditions to obtain a stable soluble protein of the active tyrosine kinase domain of EGFR (EGFR-TK) and ErbB2 (ErbB2-TK) in a bacterial system, albeit in relatively low yields. The recombinant gene was inserted into a pColdI vector and recombinant protein was expressed at low temperature. Purification of EGFR-TK and ErbB2-TK took place under the same conditions by purified supernatant using a diethylaminoethyl sepharose column followed by anion exchange and size-exclusion chromatography columns. The final yields of purified EGFR-TK and ErbB2-TK were 8.4 and 9.5 mg per liter of culture, respectively. Determination of EGFR-TK and ErbB2-TK was performed via enzyme activity with commercial drugs. The IC₅₀ values of erlotinib and afatinib against EGFR-TK were 13.09 nM and 2.36 nM respectively, while the IC₅₀ values of lapatinib and afatinib against ErbB2-TK were 24.69 nM and 1.36 nM, respectively. These results confirmed that soluble proteins of the active intracellular domain of the HERs family were successfully expressed and purified in a bacterial system. The new protein expression and purification protocol will greatly facilitate the enzymatic inhibition and structural studies of this protein for drug discovery.

Convergent synthesis of hydrophilic monomethyl dolastatin 10 based drug linkers for antibody-drug conjugation

We report a modular approach to synthesize maleimido group containing hydrophilic dolastatin 10 (Dol10) derivatives as drug-linkers for the syntheses of antibody-drug conjugates (ADCs). Discrete polyethylene glycol (PEG) moieties of different chain lengths were introduced as part of the linker to impart hydrophilicity to these drug linkers. The synthesis process involved construction of PEG maleimido derivatives of the tetrapeptide intermediate (N-methylvaline-valine-dolaisoleucine-dolaproine), which were subsequently coupled with dolaphenine to generate the desired drug linkers. The synthetic method reported in this manuscript circumvents the use of highly cytotoxic Dol10 in its native form. By using trastuzumab (Herceptin®) as the antibody we have synthesized Dol10 containing ADCs. The presence of a discrete PEG chain in the drug linkers resulted in ADCs free from aggregation. The effect of PEG chain length on the biological activities of these Dol10 containing ADCs was investigated by in vitro cytotoxicity assays. ADCs containing PEG₆ and PEG₈ spacers exhibited the highest level of in vitro anti-proliferative activity against HER2-positive (SK-BR-3) human tumor cells. ADCs derived from Herceptin® and PEG₈-Dol10, at a dose of 10 mg kg^-1, effectively delayed the tumor growth and prolonged the survival time in mice bearing human ovarian SKOV-3 xenografts.

Generation of Reactive Oxygen Species by Photosensitizers and their Modes of Action on Proteins

In this review, we first survey the mechanisms underlying the chemical modification of amino acid residues in proteins by singlet oxygen elicited by photosensitizers. Singlet oxygen has the capacity to cause widespread chemical damage to cellular proteins. Its use in photodynamic therapy of tumors thus requires the development of methodologies for specific addressing of the photosensitizer to malignant cells while sparing normal tissue. We describe three targeting paradigms for achieving this objective. The first involves the use of a photosensitizer with a high affinity for its target protein; in this case, the photosensitizer is methylene blue for acetylcholinesterase. The second paradigm involves the use of the hydrophobic photosensitizer hypericin, which has the capacity to interact selectively with partially unfolded forms of proteins, including nascent species in rapidly dividing or virus-infected and cancer cells, acting preferentially at membrane interfaces. In this case, partially unfolded molten globule species of acetylcholinesterase serve as the model system. In the third paradigm, the photodynamic approach takes advantage of a general approach in 'state-of-the-art' chemotherapy, by coupling the photosensitizer emodin to a specific peptide hormone, GnRH, which recognizes malignant cells via specific GnRH receptors on their surface.

Evaluating the Effects of Hinge Flexibility on the Solution Structure of Antibodies at Concentrated Conditions

Employing 2 different coarse-grained models, we evaluated the effect of intramolecular domain-domain distances and hinge flexibility on the general solution structure of monoclonal antibodies (mAbs), within the context of protein-protein steric repulsion. These models explicitly account for the hinge region, and represent antibodies at either domain or subdomain levels (i.e., 4-bead and 7-bead representations, respectively). Additionally, different levels of mAb flexibility are also considered. When evaluating mAbs as rigid structures, analysis of small-angle scattering profiles showed that changes in the relative internal distances between Fc and Fab domains significantly alter the local arrangement of neighboring molecules, as well as the molecular packing of the concentrated mAb solutions. Likewise, enabling hinge flexibility in either of the mAb models led to qualitatively similar results, where flexibility increases the spatial molecular arrangement at elevated concentrations. This occurs because fluctuations in mAb quaternary structure are modulated by the close proximity between molecules at elevated concentrations (>50 mg mL^-1), yielding an increased molecular packing and osmotic compressibility. However, our results also showed that the mechanism behind this synergy between flexibility and packing strongly depends on both the level of structural detail and the number of degrees-of-freedom considered in the coarse-grained model.

Utilization of HEPES for Enhancing Protein Transfection into Mammalian Cells

The delivery of active proteins into cells (protein transfection) for biological purposes offers considerable potential for clinical applications. Herein we demonstrate that, with a readily available, inexpensive organic agent, the 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) method can be used for simple and efficient protein transfection. By mixing proteins with a pure HEPES solution before they are applied to live cells, proteins with various molecular weights (including antibodies, recombinant proteins, and peptides) were successfully delivered into the cytoplasm of different cell types. The protein transfection efficiency of the HEPES method was not inferior to that of commercially available systems that are both more expensive and time consuming. Studies using endocytotic inhibitors and endosomal markers have revealed that cells internalize HEPES-protein mixtures through endocytosis. Results that HEPES-protein mixtures exhibited a low diffusion coefficient suggest that HEPES might neutralize the charges of proteins and, thus, facilitate their cellular internalization. Upon internalization, the cytosolic antibodies caused the degradation of targeted proteins in TRIM21-expressing cells. In summary, the HEPES method is efficient for protein transfection and has potential for myriad clinical applications.

Antibody drug conjugates under investigation in phase I and phase II clinical trials for gastrointestinal cancer

INTRODUCTION

Antibody drug conjugates (ADCs) represent a developing class of anticancer therapeutics which are designed to selectively deliver a cytotoxic payload to tumors, while limiting systemic toxicity to healthy tissues. There are several ADCs which are currently in various stages of clinical development for the treatment of gastrointestinal malignancies.

AREAS COVERED

We discuss the biologic rationale and review the clinical experience with ADCs in the treatment of gastrointestinal malignancies, summarizing the pre-clinical and phase I/II clinical trial data that have been completed or are ongoing.

EXPERT OPINION

While there have been significant advances in the development of ADCs since they were first introduced, several challenges remain. These challenges include (i) the selection of an ideal antigen target which is tumor specific and internalized upon binding, (ii) selection of an antibody which has high affinity for its antigen target and low immunogenicity, (iii) selection of a potent payload which is cytotoxic at sub-nanomolar concentrations, and (iv) optimal design of a linker to confer ADC stability with limited off-site toxicity. Efforts are ongoing to address these issues and innovate the ADC technology to improve the safety and efficacy of these agents.

Half-Chain Cetuximab Nanoconjugates Allow Multitarget Therapy of Triple Negative Breast Cancer

The use of therapeutic monoclonal antibodies (mAbs) has revolutionized cancer treatment. The conjugation of mAbs to nanoparticles has been broadly exploited to improve the targeting efficiency of drug nanocarriers taking advantage of high binding efficacy and target selectivity of antibodies for specific cell receptors. However, the therapeutic implications of nanoconjugation have been poorly considered. In this study, half-chain fragments of the anti-EGFR mAb cetuximab were conjugated to colloidal nanoparticles originating stable nanoconjugates that were investigated as surrogates of therapeutic mAbs in triple negative breast cancer (TNBC). Three TNBC cell lines were selected according to EGFR expression, which regulates activation of MAPK/ERK and PI3K/Akt pathways, and to distinctive molecular profiling including KRAS, PTEN, and BRCA1 mutations normally associated with diverse sensitivity to treatment with cetuximab. The molecular mechanisms of action of nanoconjugated half-chain mAb, including cell targeting, interference with downstream signaling pathways, proliferation, cell cycle, and apoptosis, along with triggering of ADCC response, were investigated in detail in sensitive and resistant TNBC cells. We found that half-chain mAb nanoconjugation was able to enhance the therapeutic efficacy and improve the target selectivity against sensitive, but unexpectedly also resistant, TNBC cells. Viability assays and signaling transduction modulation suggested a role of BRCA1 mutation in TNBC resistance to cetuximab alone, whereas its effect could be circumvented using half-chain cetuximab nanoconjugates, suggesting that nanoconjugation not only improved the antibody activity but also exerted different mechanisms of action. Our results provide robust evidence of the potential of half-chain antibody nanoconjugates in the treatment of TNBC, which could offer a new paradigm for therapeutic antibody administration, potentially allowing improved curative efficiency and reduced minimal effective dosages in both sensitive and resistant tumors.

Natural killer cells induce distinct modes of cancer cell death: Discrimination, quantification, and modulation of apoptosis, necrosis, and mixed forms

Immune therapy of cancer is among the most promising recent advances in medicine. Whether the immune system can keep cancer in check depends on, among other factors, the efficiency of immune cells to recognize and eliminate cancer cells. We describe a time-resolved single-cell assay that reports the quality, quantity, and kinetics of target cell death induced by single primary human natural killer (NK) cells. The assay reveals that single NK cells induce cancer cell death by apoptosis and necrosis but also by mixed forms. Inhibition of either one of the two major cytotoxic pathways, perforin/granzyme release or FasL/FasR interaction, unmasked the parallel activity of the other one. Ca²⁺ influx through Orai channels is important for tuning killer cell function. We found that the apoptosis/necrosis ratio of cancer cell death by NK cells is controlled by the magnitude of Ca²⁺ entry and furthermore by the relative concentrations of perforin and granzyme B. The possibility to change the apoptosis/necrosis ratio employed by NK cells offers an intriguing possibility to modulate the immunogenicity of the tumor microenvironment.

New Mechanism for Release of Endosomal Contents: Osmotic Lysis via Nigericin-Mediated K+/H+ Exchange

Although peptides, antibodies/antibody fragments, siRNAs, antisense DNAs, enzymes, and aptamers are all under development as possible therapeutic agents, the breadth of their applications has been severely compromised by their inability to reach intracellular targets. Thus, while macromolecules can often enter cells by receptor-mediated endocytosis, their missions frequently fail due to an inability to escape their entrapping endosomes. In this paper, we describe a general method for promoting release of any biologic material from any entrapping endosome. The strategy relies on the fact that all nascent endosomes contain extracellular (Na⁺-enriched) medium, but are surrounded by intracellular (K⁺-enriched) fluid in the cytoplasm. Osmotic swelling and rupture of endosomes will therefore be facilitated if the flow of K⁺ down its concentration gradient from the cytosol into the endosome can be facilitated without allowing downhill flow of Na⁺ from the endosome into the cytosol. While any K⁺ selective ionophore can promote the K⁺ specific influx, the ideal K⁺ ionophore will also exchange influxed K⁺ for an osmotically inactive proton (H⁺) in order to prevent buildup of an electrical potential that would rapidly halt K⁺ influx. The only ionophore that catalyzes this exchange of K⁺ for H⁺ efficiently is nigericin. We demonstrate here that ligand-targeted delivery of nigericin into endosomes that contain an otherwise impermeable fluorescent dye can augment release of the dye into the cell cytosol via swelling/bursting of the entrapping endosomes. We further show that nigericin-facilitated escape of a folate-targeted luciferase siRNA conjugate from its entrapping endosomes promotes rapid suppression of the intended luciferase reporter gene. Taken together, we propose that ionophore-catalyzed entry of K⁺ into endosomal compartments can promote the release of otherwise impermeable contents from their encapsulating endosomes.

Immunoconjugates for Osteosarcoma Therapy: Preclinical Experiences and Future Perspectives

Osteosarcoma (OS) is an aggressive osteoid-producing tumor of mesenchymal origin, which represents the most common primary bone malignancy. It is characterized by a complex and frequently uncertain etiology. The current standard care for high-grade OS treatment is neoadjuvant chemotherapy, followed by surgery and post-operative chemotherapy. In order to ameliorate survival rates of patients, new therapeutic approaches have been evaluated, mainly immunotherapy with antibody-drug conjugates or immunoconjugates. These molecules consist of a carrier (frequently an antibody) joined by a linker to a toxic moiety (drug, radionuclide, or toxin). Although several clinical trials with immunoconjugates have been conducted, mainly in hematological tumors, their potential as therapeutic agents is relatively under-explored in many types of cancer. In this review, we report the immunoconjugates directed against OS surface antigens, considering the in vitro and in vivo studies. To date, several attempts have been made in preclinical settings, reporting encouraging results and demonstrating the validity of the idea. The clinical experience with glembatumumab vedotin may provide new insights into the real efficacy of antibody-drug conjugates for OS therapy, possibly giving more information about patient selection. Moreover, new opportunities could arise from the ongoing clinical trials in OS patients with unconjugated antibodies that could represent future candidates as carrier moieties of immunoconjugates.

Evaluation of TAK-264, an Antibody-Drug Conjugate in Pancreatic Cancer Cell Lines and Patient-Derived Xenograft Models

BACKGROUND

Antibody-drug conjugates (ADCs) are an emerging technology consisting of an antibody, linker, and toxic agent, which have the potential to offer a targeted therapeutic approach. A novel target recently explored for the treatment of pancreatic cancer is guanylyl cyclase C (GCC). The objective of this study was to determine the anti-tumorigenic activity of TAK-264, an investigational ADC consisting of an antibody targeting GCC linked to a monomethyl auristatin E payload via a peptide linker.

METHODS

The antiproliferative effects of TAK-264 assessed in a panel of eleven pancreatic cancer cell lines. Additionally, ten unique pancreatic ductal adenocarcinoma cancer patient-derived xenograft models were treated with TAK-264 and the efficacy was determined. Baseline levels of GCC were analyzed on PDX models and cell lines. Immunoblotting was performed to evaluate the effects of TAK-264 on downstream effectors.

RESULTS

GCC protein expression was analyzed by immunoblotting in both normal and tumor tissue; marked increase in GCC expression was observed in tumor tissue. The in vitro experiments demonstrated a range of responses to TAK-264. Eight of the ten PDAC PDX models treated with TAK-264 demonstrated a statistically significant tumor growth inhibition. Immunoblotting demonstrated an increase in phosphorylated-HistoneH3 in both responsive and less responsive cell lines and PDAC PDX models treated with TAK-264. There was no correlation between baseline levels of GCC and response in either PDX or cell line models.

CONCLUSION

TAK-264 has shown suppression activity in pancreatic cancer cell lines and in pancreatic PDX models. These findings support further investigation of ADC targeting GCC.

Consistent expression of guanylyl cyclase-C in primary and metastatic gastrointestinal cancers

BACKGROUND

The transmembrane receptor guanylate cyclase-C (GCC) has been found to be expressed in colorectal cancers. However, limited data are available on GCC protein expression in non-colorectal gastrointestinal tumors and few studies have reported whether GCC protein expression was consistently preserved in synchronous primary and metastatic cancer tissues.

METHODS

GCC protein status was assessed by immunohistochemistry in tumor specimens from individuals (n = 627) with gastrointestinal tumors, including esophageal (n = 130), gastric (n = 276), pancreatic (n = 136), and colorectal (n = 85) primary and metastatic tumors. Tissue specimens consisted of tissue microarrays containing esophageal, gastric, pancreatic tumors, and whole-slide tissue sections from colorectal cancer patients with matching primary and metastatic tumors.

RESULT

Among the evaluated esophageal, gastric, and pancreatic tumors, the frequency of GCC positivity at the protein level ranged from 59% to 68%. GCC was consistently expressed in primary and matched/synchronous metastatic lesions of colorectal cancer tissues derived from the same patients.

CONCLUSION

This observational study demonstrated the protein expression of GCC across various gastrointestinal malignancies. In all cancer histotypes, GCC protein localization was observed predominantly in the cytoplasm compared to the membrane region of tumor cells. Consistent immunohistochemistry detection of GCC protein expression in primary colorectal cancers and in their matched liver metastases suggests that the expression of GCC is maintained throughout the process of tumor progression and formation of metastatic disease.

Treatment of Relapsed/Refractory Acute Lymphoblastic Leukemia in Adults

Patients with relapsed and refractory acute lymphoblastic leukemia (ALL) have a dismal prognosis with less than 10 % of patients surviving 5 years. Most such patients cannot be rescued with currently available therapies, whatever the initial treatment they receive. Therefore, there is an urgent need for novel treatment options. Fortunately, over the past several years, an improved understanding of the biology of the disease has allowed the identification of rational molecular targets for therapeutic endeavors and the emergence of novel therapies has sparked great interest. This review will discuss the current treatment landscape for adult patients with relapsed and/or refractory ALL.

Therapeutic potential of an anti-HER2 single chain antibody-DM1 conjugates for the treatment of HER2-positive cancer

Antibody-drug conjugates (ADCs) take the advantage of monoclonal antibodies to selectively deliver highly potent cytotoxic drugs to tumor cells, which have become a powerful measure for cancer treatment in recent years. To develop a more effective therapy for human epidermal growth factor receptor 2 (HER2)-positive cancer, we explored a novel ADCs composed of anti-HER2 scFv-HSA fusion antibodies conjugates with a potent cytotoxic drug DM1. The resulting ADCs, T-SA1-DM1 and T-SA2-DM1 (drug-to-antibody ratio in the range of 3.2-3.5) displayed efficient inhibition in the growth of HER2-positive tumor cell lines and the half-maximal inhibitory concentration on SKBR-3 and SKOV3 cells were both at the nanomolar levels in vitro. In HER2-positive human ovarian cancer xenograft models, T-SA1-DM1 and T-SA2-DM1 also showed remarkable antitumor activity. Importantly, three out of six mice exhibited complete remission without regrowth in the high-dose group of T-SA1-DM1. On the basis of the analysis of luminescence imaging, anti-HER2 scFv-HSA fusion antibodies, especially T-SA1, showed strong and rapid tumor tissue penetrability and distribution compared with trastuzumab. Collectively, the novel type of ADCs is effective and selective targeting to HER2-positive cancer, and may be a promising antitumor drug candidate for further studies.

Advances in the development of aptamer drug conjugates for targeted drug delivery

A key goal of modern medicine is target-specific therapeutic intervention. However, most drugs lack selectivity, resulting in 'off-target' side effects. To address the requirements of 'targeted therapy,' aptamers, which are artificial oligonucleotides, have been used as novel targeting ligands to construct aptamer drug conjugates (ApDC) that can specifically bind to a broad spectrum of targets, including diseased cells. Accordingly, the application of aptamers in targeted drug delivery has attracted broad interest due to their impressive selectivity and affinity, low immunogenicity, easy synthesis with high reproducibility, facile modification, and relatively rapid tissue penetration with no toxicity. Functionally, aptamers themselves can be used as macromolecular drugs, and they are also commonly used in biomarker discovery and targeted drug delivery. In this review, we will highlight the most recent advances in the development of aptamers and aptamer conjugates, and discuss their potential in targeted therapy. WIREs Nanomed Nanobiotechnol 2017, 9:e1438. doi: 10.1002/wnan.1438 For further resources related to this article, please visit the WIREs website.

Phase II study of the antibody-drug conjugate TAK-264 (MLN0264) in patients with metastatic or recurrent adenocarcinoma of the stomach or gastroesophageal junction expressing guanylyl cyclase C

Background The first-in-class antibody-drug conjugate TAK-264 (formerly MLN0264) consists of an antibody targeting guanylyl cyclase C (GCC) conjugated to monomethyl auristatin E (MMAE) via a peptide linker. This phase II study evaluated the efficacy and safety of TAK-264 in patients with adenocarcinoma of the stomach or gastroesophageal junction expressing GCC, who had progressed on ≥1 line of prior therapy. Methods This study used a two-stage design, with an interim analysis conducted after stage I to determine whether to continue to stage II or discontinue on the grounds of futility. Adult patients with gastric and gastroesophageal junction adenocarcinoma expressing low, intermediate, or high GCC levels received TAK-264 1.8 mg/kg as a 30-min intravenous infusion once every 21 days, for up to 1 year. The primary endpoint was objective response rate. Radiographic assessments of tumor burden were performed every 2 cycles (6 weeks). Results A total of 38 patients participated in the study. Patients received a median of 2 (range 1-14) cycles; 8 (21%) received at least 6 cycles. The most common adverse events were nausea (53%), fatigue (32%), and decreased appetite (29%). Grade ≥3 events including anemia, diarrhea, and neutropenia were seen in 14 (37%) patients. Systemic exposure to TAK-264 was maintained throughout each treatment cycle. Two patients (6%) with intermediate GCC expression had objective responses. Conclusions TAK-264 demonstrated a manageable safety profile in this patient population. The stage I interim analysis did not support continuation to stage II of the study.

Adenylyl cyclase signalling complexes - Pharmacological challenges and opportunities

Signalling pathways involving the vital second messanger, cAMP, impact on most significant physiological processes. Unsurprisingly therefore, the activation and regulation of cAMP signalling is tightly controlled within the cell by processes including phosphorylation, the scaffolding of protein signalling complexes and sub-cellular compartmentalisation. This inherent complexity, along with the highly conserved structure of the catalytic sites among the nine membrane-bound adenylyl cyclases, presents significant challenges for efficient inhibition of cAMP signalling. Here, we will describe the biochemistry and cell biology of the family of membrane-bound adenylyl cyclases, their organisation within the cell, and the nature of the cAMP signals that they produce, as a prelude to considering how cAMP signalling might be perturbed. We describe the limitations associated with direct inhibition of adenylyl cyclase activity, and evaluate alternative strategies for more specific targeting of adenylyl cyclase signalling. The inherent complexity in the activation and organisation of adenylyl cyclase activity may actually provide unique opportunities for selectively targeting discrete adenylyl cyclase functions in disease.

Antibody-drug conjugate directed against the guanylyl cyclase antigen for the treatment of gastrointestinal malignancies

Antibody-directed cancer chemotherapy in the form of antibody-drug conjugates (ADCs) may improve the therapeutic index with the potential to enhance efficacy and decrease systemic toxicity. ADCs consist of three key components including an antibody that specifically binds to the target, a toxic agent and a linker which releases the toxic agent inside tumor cells. A novel ADC, MLN0264 (TAK-264) was recently investigated in patients with gastrointestinal (GI) malignancies. TAK-264 is an anti- guanylyl cyclase C (GCC) antibody conjugated via a protease-cleavable linker to the potent anti-microtubule agent monomethyl auristatin E (MMAE) (linker and toxin licensed from Seattle Genetics). Following binding to GCC, the ADC is internalized and transported to lysosomes where MMAE is released to bind to tubulin, leading to cell cycle arrest and apoptosis. This GCC targeting ADC has been evaluated in clinical studies in patients with advanced gastrointestinal malignancies. The early findings from Phase 1 study have shown preliminary activity signals in gastric, gastroesophageal, and pancreatic cancer. Results from two phase II studies in pancreatic and gastoesophageal adenocarcinoma showed only limited activity. Antibody-drug-conjugates offer a promising therapeutic modality aimed at providing target-directed cancer chemotherapy. Herein we discuss the GCC target and gastrointestinal malignancies where GCC based targeted therapies could further evolve and offer a significant clinical benefit.

Recent Advances in the Development of Antineoplastic Agents Derived from Natural Products

Through years of evolutionary selection pressures, organisms have developed potent toxins that coincidentally have marked antineoplastic activity. These natural products have been vital for the development of multiagent treatment regimens currently employed in cancer chemotherapy, and are used in the treatment of a variety of malignancies. Therefore, this review catalogs recent advances in natural product-based drug discovery via the examination of mechanisms of action and available clinical data to highlight the utility of these novel compounds in the burgeoning age of precision medicine. The review also highlights the recent development of antibody-drug conjugates and other immunotoxins, which are capable of delivering highly cytotoxic agents previously deemed too toxic to elicit therapeutic benefit preferentially to neoplastic cells. Finally, the review examines natural products not currently used in the clinic that have novel mechanisms of action, and may serve to supplement current chemotherapeutic protocols.

High throughput cytotoxicity screening of anti-HER2 immunotoxins conjugated with antibody fragments from phage-displayed synthetic antibody libraries

Immunotoxins are an important class of antibody-based therapeutics. The potency of the immunotoxins depends on the antibody fragments as the guiding modules targeting designated molecules on cell surfaces. Phage-displayed synthetic antibody scFv libraries provide abundant antibody fragment candidates as targeting modules for the immunoconjugates, but the discovery of optimally functional immunoconjugates is limited by the scFv-payload conjugation procedure. In this work, cytotoxicity screening of non-covalently assembled immunotoxins was developed in high throughput format to discover highly functional synthetic antibody fragments for delivering toxin payloads. The principles governing the efficiency of the antibodies as targeting modules have been elucidated from large volume of cytotoxicity data: (a) epitope and paratope of the antibody-based targeting module are major determinants for the potency of the immunotoxins; (b) immunotoxins with bivalent antibody-based targeting modules are generally superior in cytotoxic potency to those with corresponding monovalent targeting module; and (c) the potency of the immunotoxins is positively correlated with the densities of the cell surface antigen. These findings suggest that screening against the target cells with a large pool of antibodies from synthetic antibody libraries without the limitations of natural antibody responses can lead to optimal potency and minimal off-target toxicity of the immunoconjugates.