The immune system employs several checkpoint pathways to regulate responses, maintain homeostasis and prevent self-reactivity and autoimmunity. Tumor cells can hijack these protective mechanisms to enable immune escape, cancer survival and proliferation. Blocking antibodies, designed to interfere with checkpoint molecules CTLA-4 and PD-1/PD-L1 and counteract these immune suppressive mechanisms, have shown significant success in promoting immune responses against cancer and can result in tumor regression in many patients. While inhibitors to CTLA-4 and the PD-1/PD-L1 axis are well-established for the clinical management of melanoma, many patients do not respond or develop resistance to these interventions. Concerted efforts have focused on combinations of approved therapies aiming to further augment positive outcomes and survival. While CTLA-4 and PD-1 are the most-extensively researched targets, results from pre-clinical studies and clinical trials indicate that novel agents, specific for checkpoints such as A2AR, LAG-3, IDO and others, may further contribute to the improvement of patient outcomes, most likely in combinations with anti-CTLA-4 or anti-PD-1 blockade. This review discusses the rationale for, and results to date of, the development of inhibitory immune checkpoint blockade combination therapies in melanoma. The clinical potential of new pipeline therapeutics, and possible future therapy design and directions that hold promise to significantly improve clinical prognosis compared with monotherapy, are discussed.

In this 13th annual installment of the annual ‘Antibodies to Watch’ article series, we discuss key events in commercial antibody therapeutics development that occurred in 2021 and forecast events that might occur in 2022. Regulatory review of antibody therapeutics that target the SARS-CoV-2 coronavirus proceeded at an unprecedented pace in 2021, resulting in both emergency use authorizations and full approvals for sotrovimab, regdanvimab, REGEN-COV2, as well as others, in numerous countries. As of November 1, a total of 11 antibody therapeutics had been granted first approvals in either the United States or European Union in 2021 (evinacumab, dostarlimab loncastuximab tesirine, amivantamab, aducanumab, tralokinumab, anifrolumab, bimekizumab, tisotumab vedotin, regdanvimab, REGEN-COV2). The first global approvals of seven products, however, were granted elsewhere, including Japan (pabinafusp alfa), China (disitamab vedotin, penpulimab, zimberelimab), Australia (sotrovimab, REGEN-COV2), or the Republic of Korea (regdanvimab). Globally, at least 27 novel antibody therapeutics are undergoing review by regulatory agencies. First actions by the Food and Drug Administration on the biologics license applications for faricimab, sutimlimab, tebentafusp, relatlimab, sintilimab, ublituximab and tezepelumab are expected in the first quarter of 2022. Finally, our data show that, with antibodies for COVID-19 excluded, the late-stage commercial clinical pipeline of antibody therapeutics grew by over 30% in the past year. Of those in late-stage development, marketing applications for at least 22 may occur by the end of 2022.

IgE antibodies are key mediators of antiparasitic immune responses, but their potential for cancer treatment via antibodydependent cell-mediated cytotoxicity (ADCC) has been little studied. Recently, tumor antigen-specific IgEs were reported to restrict cancer cell growth by engaging high-affinity Fc receptors on monocytes and macrophages; however, the underlying therapeutic mechanisms were undefined and in vivo proof of concept was limited. Here, an immunocompetent rat model was designed to recapitulate the human IgE-Fce receptor system for cancer studies. We also generated rat IgE and IgG mAbs specific for the folate receptor (FRa), which is expressed widely on human ovarian tumors, along with a syngeneic rat tumor model expressing human FRa. Compared with IgG, anti-FRa IgE reduced lung metastases. This effect was associated with increased intratumoral infiltration by TNFa þ and CD80

Antibody-drug conjugates (ADCs) are emerging as effective tools in cancer therapy, combining the antibody's exquisite specificity for the target antigen-expressing cancer cell together with the cytotoxic potency of the payload. Much success stems from the rational design of “toxic warheads”, chemically linked to antibodies, and from fine-tuning the intricate properties of chemical linkers. Here, we focus on the antibody moiety of ADCs, dissecting the impact of Fab, linkers, isotype and Fc structure on the anti-tumoral and immune-activating functions of ADCs. Novel design approaches informed by antibody structural attributes present opportunities that may contribute to the success of next generation ADCs.

IgG4 is the least abundant subclass of IgG in normal human serum, but elevated IgG4 levels are triggered in response to a chronic antigenic stimulus and inflammation. Since the immune system is exposed to tumor-associated antigens over a relatively long period of time, and tumors notoriously promote inflammation, it is unsurprising that IgG4 has been implicated in certain tumor types. Despite differing from other IgG subclasses by only a few amino acids, IgG4 possesses unique structural characteristics that may be responsible for its poor effector function potency and immunomodulatory properties. We describe the unique attributes of IgG4 that may be responsible for these regulatory functions, particularly in the cancer context. We discuss the inflammatory conditions in tumors that support IgG4, the emerging and proposed mechanisms by which IgG4 may contribute to tumor-associated escape from immune surveillance and implications for cancer immunotherapy.

Identification of mutations in the gene encoding the serine/threonine-protein kinase, BRAF, and constitutive activation of the mitogen-activated protein kinase (MAPK) pathway in around 50% of malignant melanomas have led to the development and regulatory approval of targeted pathway inhibitor drugs. A proportion of patients are intrinsically resistant to BRAF inhibitors, and most patients who initially respond, acquire resistance within months. In this review, we discuss pathway inhibitors and their mechanisms of resistance, and we focus on numerous efforts to improve clinical benefits through combining agents with disparate modes of action, including combinations with checkpoint inhibitor antibodies. We discuss the merits of combination strategies based on enhancing immune responses or overcoming tumor-associated immune escape mechanisms. Emerging insights into mechanisms of action, resistance pathways and their impact on host-tumor relationships will inform the design of optimal combinations therapies to improve outcomes for patients who currently do not benefit from recent treatment breakthroughs.

Overexpression of the chondroitin sulfate proteoglycan 4 (CSPG4) has been associated with the pathology of multiple types of such as melanoma, breast cancer, squamous cell carcinoma, mesothelioma, neuroblastoma, adult and pediatric sarcomas, and some hematological cancers. CSPG4 has been reported to exhibit a role in the growth and survival as well as in the spreading and metastasis of tumor cells. CSPG4 is overexpressed in several malignant diseases, while it is thought to have restricted and low expression in normal tissues. Thus, CSPG4 has become the target of numerous anticancer treatment approaches, including monoclonal antibody-based therapies. This study reviews key potential anti-CSPG4 antibody and immune-based therapies and examines their direct antiproliferative/metastatic and immune activating mechanisms of action.

Ion channels regulate cell proliferation, differentiation, and migration in normal and neoplastic cells through cell-cell and cell-extracellular matrix (ECM) transmembrane receptors called integrins. K + flux through the human ether-à-gogo-related gene 1 (hERG1) channel shapes action potential firing in excitable cells such as cardiomyocytes. Its abundance is often aberrantly high in tumors, where it modulates integrin-mediated signaling. We found that hERG1 interacted with the b 1 integrin subunit at the plasma membrane of human cancer cells. This interaction was not detected in cardiomyocytes because of the presence of the hERG1 auxiliary subunit KCNE1 (potassium voltage-gated channel subfamily E regulatory subunit 1), which blocked the b 1 integrin-hERG1 interaction. Although open hERG1 channels did not interact as strongly with b 1 integrins as did closed channels, current flow through hERG1 channels was necessary to activate the integrin-dependent phosphorylation of Tyr 397 in focal adhesion kinase (FAK) in both normal and cancer cells. In immunodeficient mice, proliferation was inhibited in breast cancer cells expressing forms of hERG1 with impaired K + flow, whereas metastasis of breast cancer cells was reduced when the hERG1/b 1 integrin interaction was disrupted. We conclude that the interaction of b 1 integrins with hERG1 channels in cancer cells stimulated distinct signaling pathways that depended on the conformational state of hERG1 and affected different aspects of tumor progression.