Sequential immunotherapy regimens-expect the unexpected

A Listeria-based vaccine targeting ISG15 exerts anti-tumor efficacy in renal cell carcinoma

Renal cell carcinoma (RCC) is the deadliest form of urological cancer and is projected to be the fourth most common neoplasm in the USA in males by 2040. In addition to the current poor prognosis with 5-year survival rates hardly reaching 15%, the prevalence of resistance to currently available systemic therapies has also established an urgent need to develop new treatment regimen(s) for advanced RCC. Interferon-stimulated gene 15 (ISG15) is the first identified ubiquitin-like modifier and has been intensively studied for its central role in innate immunity against intracellular pathogens. However, in this study, we identified ISG15 as a novel tumor-associated antigen and prognostic marker in RCC. Further, we therapeutically targeted elevated ISG15 expression by means of a Listeria monocytogenes (Lm)-based vaccine, designated Lm-LLO-ISG15, in both subcutaneous and orthotopic RCC mouse models. Treatment with Lm-LLO-ISG15 resulted in an influx of tumor-infiltrating effector T cells and significant anti-tumor efficacy in both subcutaneous and orthotopic RCC tumor models. Treatment with Lm-LLO-ISG15 also generated a robust interferon-gamma response and attracted a larger pool of polyfunctional T cells into the tumor microenvironment. Importantly, the therapeutic efficacy of Lm-LLO-ISG15 in RCC is comparable to that of anti-PD-1 and sunitinib, the current frontline therapies for RCC patients. Collectively, our work illustrates that targeting ISG15 in RCC with a CTL-based immunotherapy such as Lm-LLO-ISG15 is a promising and potentially translatable therapeutic strategy to enhance survival in RCC patients.

Drug-Induced Liver Injury: Highlights and Controversies in the Recent Literature

Drug-induced liver injury (DILI) remains an important, yet challenging diagnosis for physicians. Each year, additional drugs are implicated in DILI and this year was no different, with more than 1400 articles published on the subject. This review examines some of the most significant highlights and controversies in DILI-related research over the past year and their implications for clinical practice. Several new drugs were approved by the US Food and Drug Administration including a number of drugs implicated in causing DILI, particularly among the chemotherapeutic classes. The COVID-19 pandemic was also a major focus of attention in 2020 and we discuss some of the notable aspects of COVID-19-related liver injury and its implications for diagnosing DILI. Updates in diagnostic and causality assessments related to DILI such as the Roussel Uclaf Causality Assessment Method are included, mindful that there is still no single biomarker or diagnostic tool to unequivocally diagnose DILI. Glutamate dehydrogenase received renewed attention as being more specific than alanine aminotransferase. There were a few new reports of previously unrecognized hepatotoxins, including immune modulators and novel gene therapy drugs that we highlight. Updates and new developments of previously described hepatotoxins, such as immune checkpoint inhibitors and anti-tuberculosis drugs are reviewed. Finally, novel technologies such as organoid culture systems to better predict DILI preclinically may be coming of age and determinants of hepatocyte loss, such as calculating P_ALT are poised to improve our current means of estimating DILI severity and the risk of acute liver failure.

Liver toxicity as a limiting factor to the increasing use of immune checkpoint inhibitors

Immune checkpoint inhibitors (ICIs) improve clinical outcomes in patients suffering from different types of cancer. Liver toxicity is one of the immune-related adverse events associated with immunotherapy; although not common, its management is challenging as it is extremely heterogeneous in terms of presentation and severity. Differences in the development and evolution of ICI-related toxicity in healthy or cirrhotic livers have not yet been elucidated. Assessing causality is key to diagnosing ICI-induced liver toxicity; liver biopsies can assist not only in the differential diagnosis but also in assessing the severity of histological liver damage. The current classification of severity overestimates the grade of liver injury and needs to be revised to reflect the views of hepatologists. Spontaneous improvements in ICI-related liver toxicity have been reported, so corticosteroid therapy should probably be individualised not systematic. The reintroduction of ICIs in a patient with previous immune-mediated hepatitis may be possible, but the risk/benefit ratio should be considered, as the risk factors for hepatitis recurrence are currently unclear. The management of these patients, requiring a balance between efficacy, toxicity and specific treatments, necessitates multidisciplinary collaboration. The incidence of immune-related liver toxicity will continue to rise based on the increasing use of ICIs for most cancers, mandating improved understanding and management of this complication.

A QSP Model for Predicting Clinical Responses to Monotherapy, Combination and Sequential Therapy Following CTLA-4, PD-1, and PD-L1 Checkpoint Blockade

Over the past decade, several immunotherapies have been approved for the treatment of melanoma. The most prominent of these are the immune checkpoint inhibitors, which are antibodies that block the inhibitory effects on the immune system by checkpoint receptors, such as CTLA-4, PD-1 and PD-L1. Preclinically, blocking these receptors has led to increased activation and proliferation of effector cells following stimulation and antigen recognition, and subsequently, more effective elimination of cancer cells. Translation from preclinical to clinical outcomes in solid tumors has shown the existence of a wide diversity of individual patient responses, linked to several patient-specific parameters. We developed a quantitative systems pharmacology (QSP) model that looks at the mentioned checkpoint blockade therapies administered as mono-, combo- and sequential therapies, to show how different combinations of specific patient parameters defined within physiological ranges distinguish different types of virtual patient responders to these therapies for melanoma. Further validation by fitting and subsequent simulations of virtual clinical trials mimicking actual patient trials demonstrated that the model can capture a wide variety of tumor dynamics that are observed in the clinic and can predict median clinical responses. Our aim here is to present a QSP model for combination immunotherapy specific to melanoma.

Developing combination strategies using PD-1 checkpoint inhibitors to treat cancer

More than 3000 clinical trials are evaluating the clinical activity of the PD-1 checkpoint inhibitors as monotherapies and in combinations with other cancer therapies [1]. The PD-1 checkpoint inhibitors are remarkable for their clinical activities in shrinking tumors across a wide range of tumor types, in causing durable responses, and in their tolerability. These attributes position them as favorable agents in clinical combinations. Historically, approaches to cancer therapy combinations focused on agents with orthogonal activities to avoid shared resistance mechanisms and shared toxicities. Although CTLA-4/PD-1 combinations have progressed based on possible immune interactions, additional approaches have used more orthogonal treatments such as standard of care chemotherapies and anti-angiogenesis inhibitors. Using the concept of independent activity pioneered by Bliss [2], examples of these approaches were compared. Both standard of care chemotherapy and anti-angiogenesis combinations show promising clinical activity above that predicted by the independent contributions of the agents tested on their own. In contrast, the combinations of CTLA4/PD-1 checkpoint inhibitors in renal cancer and melanoma show no more activity than that predicted by the independent contributions of the monotherapies. This update on approaches to the development of clinical combination therapies highlights the potential importance of combining PD-1 checkpoint inhibitors with a broad range of clinically active partners.

Modulation of the tumor microenvironment by intratumoral administration of IMO-2125, a novel TLR9 agonist, for cancer immunotherapy

The objective of cancer immunotherapy is to prime the host's immune system to recognize and attack malignant tumor cells. IMO‑2125, a Toll‑like receptor 9 (TLR9) agonist, exhibited potent antitumor effects in the murine syngeneic A20 lymphoma and the CT26 colon carcinoma models. IMO‑2125 exhibited superior A20 antitumor activity when injected intratumorally (i.t.) compared with equivalent subcutaneous doses. In mice bearing dual CT26 grafts, the i.t. injection of right flank tumors elicited infiltration of cluster of differentiation (CD)3+ T lymphocytes into tumors, resulting in the regression of injected and uninjected left flank tumors. Depletion of CD8+, but not CD4+, T‑cells abrogated the IMO‑2125‑mediated antitumor response, suggesting that CD8+ lymphocytes are required for the antitumor activity. In mice harboring right flank CT26 and left flank β‑galactosidase (β‑gal)‑expressing CT26.CL25 grafts, the i.t. administration of IMO‑2125 to the CT26 graft resulted in potent and dose‑dependent antitumor activity against the two grafts. Splenic T‑cells isolated from these mice responded to AH1 antigen (present in the two tumors) and β‑gal antigen (present only in CT26.CL25) in an interferon γ enzyme‑linked immunospot assay, suggesting the clonal expansion of T‑cells directed against antigens from the two tumors. Mice with ablated CT26 tumors by previous IMO‑2125 treatment rejected re‑implanted CT26 tumor cells, but not A20 tumor cells, demonstrating that the initial IMO‑2125 treatment created a long‑lived tumor‑specific immune memory of CT26 antigens. A quantitative increase in CD3+ T lymphocytes in injected A20 tumors and an upregulation of selected checkpoint genes, including indoleamine 2,3‑dioxygenase (IDO)‑1, IDO‑2, programmed cell death protein-1 (PD-1); programmed cell death protein ligand 1 (PD-L1), carcinoembryonic antigen‑related cell adhesion molecule 1, tumor necrosis factor receptor superfamily member 4 (OX40), OX40 ligand, T‑cell immunoglobulin and mucin‑domain‑containing 3 protein, lymphocyte‑activation gene 3, cytotoxic T‑lymphocyte‑associated protein 4, were observed following IMO‑2125 treatment. IMO‑2125 also increased immune checkpoint gene expression in injected and uninjected contralateral CT26 tumors, suggesting that the co‑administration of anti‑CTLA‑4, anti‑PD‑1 or anti‑PD‑L1 therapies with IMO‑2125 may provide additional therapeutic efficacy.