NAV-001, a high-efficacy antibody-drug conjugate targeting mesothelin with improved delivery of a potent payload by counteracting MUC16/CA125 inhibitory effects

Topoisomerase II-targeting anticancer clinical candidates and drugs: A critical analysis, unravelling molecular medicinal insights and promising research roadmap

In recent years, the USFDA-approved drug molecules are being frequently analyzed to provide perspectives and strategies for novel therapeutic discovery and development. Some of the remarkable analyses include physicochemical properties of drugs relevant to oral bioavailability, frequent presence of drug relevant-structural motifs, natural products as sources of new drugs, and synthetic approaches to new drugs. In this review article, for the first time, we present a structure-function analysis of human topoisomerase II (hTopo II) inhibitors those are currently clinically used or under clinical trials for anticancer treatment. The case studies and a critical molecular medicinal insight for their therapeutic development have been presented. The review illustrates various key aspects: the hTopo II inhibitors' molecular modulations, common pharmacophores, interactions at molecular level crucial for inhibition of enzyme at its various stages of catalytic function, and network polypharmacology of Topo II with different targets. Numerous toxicophore motifs have been identified, which provide important alerts while designing and discovering novel therapeutic agents. A range of innovative approaches including property-focused strategies, ADCs, and Click Activated Protodrugs Against Cancer (CAPAC) that have addressed challenges faced in the hTopo II-based therapeutic development have been discussed. The analysis with perspectives represents a valuable educational and research resource that will encourage hTopo II-inhibition and its network polypharmacology based drug discovery studies.

ICAM-1 Is Overexpressed by Cancers and Negatively Impacts Antibody-Based Therapies Including Antibody-Drug Conjugates

Humoral immunity utilizes antibodies and immune effector cells to mediate dysregulated cancer cell killing. These mechanisms are referred to as Humoral Immuno-Oncology (HIO). HIO immunosuppression is mediated by tumor-produced proteins called HIO factors. Using a combination of patient serum analysis and literature searches, we screened a number of samples to determine if they suppressed HIO. Herein, we identified that ICAM-1 (intercellular adhesion molecule 1) can bind IgG1-type antibodies and suppress their immune effector activity. Through a series of mutagenesis, we identified a unique motif within the IgG1CH3 domain essential for ICAM-1 binding, which inhibits antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity. Conservative amino acid substitutions within the CH3 domain were able to abrogate ICAM-1 binding and overcome ICAM-1 mediated immune effector suppression. Additionally, isogenic tumor cell lines with silenced ICAM-1 expression were more susceptible to antibody-drug conjugate (ADCs) cytotoxicity than parental cells. This effect appeared to correlate with membrane ICAM-1 binding to the IgG1 component that reduced ADC internalization, a function important for maximal target cell killing. These findings highlight a novel mechanism by which tumors can suppress the host's immune system for survival and offer new concepts for engineering antibody-based therapeutics that are refractory to ICAM-1 immunosuppression.

MUC16/CA125 in cancer: new advances

MUC16/CA125 is a common diagnostic marker for many types of cancer. However, due to the widespread expression of MUC16 in cancer, its specificity and sensitivity as a target are poor, which severely limits its clinical application. In recent years, various studies have shown that the clinical application potential of MUC16/CA125 has been greatly improved. The update of detection technology improves the accuracy and range of detection, and improves the early diagnosis rate of cancer. Targeting MUC16/CA125 is an important strategy for tumor therapy. Targeting residual amino acids, n-glycoylation structures or other targets on the surface of MUC16 cells can greatly improve the accuracy of detection and therapy. The new drug delivery method broke through the original technical shackles, targeted MUC16 positive cells more specifically and improved the drug efficacy. In this paper, the technological advances in detecting and identifying MUC16 targets and the great progress in cancer screening and treatment based on MUC16 as a target are described in detail, revealing the great potential of MUC16 as a target in cancer screening and treatment, and illustrating the potential clinical application value of MUC16.

Conjugation of anti-HIV gp41 monoclonal antibody to a drug capable of targeting resting lymphocytes produces an effective cytotoxic anti-HIV immunoconjugate

HIV-infected cells persisting in the face of suppressive antiretroviral therapy are the barrier to curing infection. Cytotoxic immunoconjugates targeted to HIV antigens on the cell surface may clear these cells. We showed efficacy in mouse and macaque models using immunotoxins, but immunogenicity blunted the effect. As an alternative, we propose antibody drug conjugates (ADCs), as used in cancer immunotherapy. In cancer, the target is a dividing cell, whereas it may not be in HIV. We screened cytotoxic drugs on human primary cells and cell lines. An anthracycline derivative, PNU-159682 (PNU), was highly cytotoxic to both proliferating and resting cells. Human anti-gp41 mAb 7B2 was conjugated to ricin A chain or PNU. The conjugates were tested in vitro for cytotoxic efficacy and anti-viral effect, and in vivo for tolerability. The specificity of killing for both conjugates was demonstrated on Env+ and Env- cells. The toxin conjugate was more potent and killed more rapidly, but 7B2-PNU was effective at levels achievable in patients. The ricin conjugate was well tolerated in mice; 7B2-PNU was toxic when administered intraperitoneally but was tolerated intravenously. We have produced an ADC with potential to target the persistent HIV reservoir in both dividing and non-dividing cells while avoiding immunogenicity. Cytotoxic anti-HIV immunoconjugates may have greatest utility as part of an "activate and purge" regimen, involving viral activation in the reservoir. This is a unique comparison of an immunotoxin and ADC targeted by the same antibody and tested in the same systems.IMPORTANCEHIV infection can be controlled with anti-retroviral therapy, but it cannot be cured. Despite years of therapy that suppresses HIV, patients again become viremic shortly after discontinuing treatment. A long-lived population of memory T cells retain the genes encoding HIV, and these cells secrete infectious HIV when no longer suppressed by therapy. This is the persistent reservoir of HIV infection. The therapies described here use anti-HIV antibodies conjugated to poisons to kill the cells in this reservoir. These poisons may be of several types, including protein toxins (immunotoxins) or anti-cancer drugs (antibody drug conjugates, ADCs). We have previously shown that an anti-HIV immunotoxin had therapeutic effects in animal models, but it elicited an anti-drug immune response. Here, we have prepared an anti-HIV ADC, which would be less likely to provoke an immune response, and show its potential for use in eliminating the persistent reservoir of HIV infection.

Emerging role of mucins in antibody drug conjugates for ovarian cancer therapy

Ovarian cancer stands as the deadliest gynecologic malignancy, responsible for nearly 65% of all gynecologic cancer-related deaths. The challenges in early detection and diagnosis, coupled with the widespread intraperitoneal spread of cancer cells and resistance to chemotherapy, contribute significantly to the high mortality rate of this disease. Due to the absence of specific symptoms and the lack of effective screening methods, most ovarian cancer cases are diagnosed at advanced stages. While chemotherapy is a common treatment, it often leads to tumor recurrence, necessitating further interventions. In recent years, antibody-drug conjugates (ADCs) have emerged as a valuable tool in targeted cancer therapy. These complex biotherapeutics combine an antibody that specifically targets tumor specific/associated antigen(s) with a high potency anti-cancer drug through a linker, offering a promising approach for ovarian cancer treatment. The identification of molecular targets in various human tumors has paved the way for the development of targeted therapies, with ADCs being at the forefront of this innovation. By delivering cytotoxic agents directly to tumors and metastatic lesions, ADCs show potential in managing chemo-resistant ovarian cancers. Mucins such as MUC16, MUC13, and MUC1 have shown significantly higher expression in ovarian tumors as compared to normal and/or benign samples, thus have become promising targets for ADC generation. While traditional markers are limited by their elevated levels in non-cancerous conditions, mucins offer a new possibility for targeted treatment in ovarian cancer. This review comprehensively described the potential of mucins for the generation of ADC therapy, highlighting their importance in the quest to improve the outcome of ovarian cancer patients.

MUC16: clinical targets with great potential

Mucin 16 (MUC16) is a membrane-bound mucin that is abnormally expressed or mutated in a variety of diseases, especially tumors, while being expressed in normal body epithelium. MUC16 and its extracellular components are often important cancer-related biomarkers. Abnormal expression of MUC16 promotes tumor progression through mesenchymal protein, PI3K/AKT pathway, JAK2/STAT3 pathway, ERK/FBW7/c-Myc, and other mechanisms, and plays an important role in the occurrence and development of tumors. In addition, MUC16 also helps tumor immune escape by inhibiting T cells and NK cells. Many drugs and trials targeting MUC16 have been developed, and MUC16 may be a new direction for future treatments. In this paper, the mechanism of action of MUC16 in the development of cancer, especially in the immune escape of tumor, is introduced in detail, indicating the potential of MUC16 in clinical treatment.

Amine-Carbamate Self-Immolative Spacers Counterintuitively Release 3° Alcohol at Much Faster Rates than 1° Alcohol Payloads

Self-immolative (SI) spacers are degradable chemical connectors widely used in prodrugs and drug conjugates to release pharmaceutical ingredients in response to specific stimuli. Amine-carbamate SI spacers are particularly versatile, as they have been used to release different hydroxy cargos, ranging from 2° and 3° alcohols to phenols and oximes. In this work, we describe the ability of three amine-carbamate SI spacers to release three structurally similar imidazoquinoline payloads, bearing either a 1°, a 2° or a 3° alcohol as the leaving group. While the spacers showed comparable efficacy at releasing the 2° and 3° alcohols, the liberation of the 1° alcohol was much slower, unveiling a counterintuitive trend in nucleophilic acyl substitutions. The release of the 1° alcohol payload was only possible using a SI spacer bearing a pyrrolidine ring and a tertiary amine handle, which opens the way to future applications in drug delivery systems.

MUC1 and MUC16: critical for immune modulation in cancer therapeutics

The Mucin (MUC) family, a range of highly glycosylated macromolecules, is ubiquitously expressed in mammalian epithelial cells. Such molecules are pivotal in establishing protective mucosal barriers, serving as defenses against pathogenic assaults. Intriguingly, the aberrant expression of specific MUC proteins, notably Mucin 1 (MUC1) and Mucin 16 (MUC16), within tumor cells, is intimately associated with oncogenesis, proliferation, and metastasis. This association involves various mechanisms, including cellular proliferation, viability, apoptosis resistance, chemotherapeutic resilience, metabolic shifts, and immune surveillance evasion. Due to their distinctive biological roles and structural features in oncology, MUC proteins have attracted considerable attention as prospective targets and biomarkers in cancer therapy. The current review offers an exhaustive exploration of the roles of MUC1 and MUC16 in the context of cancer biomarkers, elucidating their critical contributions to the mechanisms of cellular signal transduction, regulation of immune responses, and the modulation of the tumor microenvironment. Additionally, the article evaluates the latest advances in therapeutic strategies targeting these mucins, focusing on innovations in immunotherapies and targeted drugs, aiming to enhance customization and accuracy in cancer treatments.

NAV-003, a bispecific antibody targeting a unique mesothelin epitope and CD3ε with improved cytotoxicity against humoral immunosuppressed tumors

Mesothelin (MSLN) is a cell surface protein overexpressed in a number of cancer types. Several antibody- and cellular-based MSLN targeting agents have been tested in clinical trials where their therapeutic efficacy has been moderate at best. Previous studies using antibody and Chimeric Antigen Receptor-T cells (CAR-T) strategies have shown the importance of particular MSLN epitopes for optimal therapeutic response, while other studies have found that certain MSLN-positive tumors can produce proteins that can bind to subsets of IgG1-type antibodies and suppress their immune effector activities. In an attempt to develop an improved anti-MSLN targeting agent, we engineered a humanized divalent anti-MSLN/anti-CD3ε bispecific antibody that avoids suppressive factors, can target a MSLN epitope proximal to the tumor cell surface, and is capable of effectively binding, activating, and redirecting T cells to the surface of MSLN-positive tumor cells. NAV-003 has shown significantly improved tumor cell killing against lines producing immunosuppressive proteins in vitro and in vivo. Moreover, NAV-003 demonstrated good tolerability in mice and efficacy against patient-derived mesothelioma xenografts co-engrafted with human peripheral blood mononuclear cells. Together these data support the potential for NAV-003 clinical development and human proof-of-concept studies in patients with MSLN-expressing cancers.