Immunotherapy in head and neck squamous cell carcinoma: An updated review

Squamous cell cancer of the head and neck (HNSCC) is the sixth most common cancer and is associated with significant morbidity and mortality. The tumor microenvironment for HNSCC is a complex interplay of immune cells, stromal cells, and cytokines amongst others. Immunotherapy acts as an effective antineoplastic agent by influencing this complex environment and includes immune checkpoint inhibitors (ICI). ICI have been approved in the frontline setting for recurrent and metastatic (R/M) HNSCC as well as platinum-refractory (second line) R/M HNSCC. However, recent clinical studies highlight that the response to immunotherapy varies, and different ICI, as well as different combination strategies play a crucial role in augmenting the efficacy of immunotherapy. An in-depth analysis and focused study of the immune contexture in patients with HNSCC receiving ICI remains critical. Many novel immunotherapies including CAR-T cell therapy, oncolytic virus therapy, and vaccines are underway. Ongoing trials are testing ICI in the neoadjuvant and adjuvant settings. Furthermore, identifying better biomarkers to target population that benefits from immunotherapy is of paramount importance. Pioneering the optimal combination regimen utilizing new novel immunotherapy has recently become a paradigm shift in the HNSCC treatment landscape. Herein, we summarize the clinical development with all ongoing clinical trials of immunotherapy in HNSCC.

Development and therapeutic manipulation of the head and neck cancer tumor environment to improve clinical outcomes

The clinical response to cancer therapies involves the complex interplay between the systemic, tumoral, and stromal immune response as well as the direct impact of treatments on cancer cells. Each individual's immunological and cancer histories are different, and their carcinogen exposures may differ. This means that even though two patients with oral tumors may carry an identical mutation in TP53, they are likely to have different pre-existing immune responses to their tumors. These differences may arise due to their distinct accessory mutations, genetic backgrounds, and may relate to clinical factors including previous chemotherapy exposure and concurrent medical comorbidities. In isolation, their cancer cells may respond similarly to cancer therapy, but due to their baseline variability in pre-existing immune responses, patients can have different responses to identical therapies. In this review we discuss how the immune environment of tumors develops, the critical immune cell populations in advanced cancers, and how immune interventions can manipulate the immune environment of patients with pre-malignancies or advanced cancers to improve therapeutic outcomes.

Strategies to Overcome Failures in T-Cell Immunotherapies by Targeting PI3K-δ and -γ

PI3K-δ and PI3K-γ are critical regulators of T-cell differentiation, senescence, and metabolism. PI3K-δ and PI3K-γ signaling can contribute to T-cell inhibition via intrinsic mechanisms and regulation of suppressor cell populations, including regulatory T-cells and myeloid derived suppressor cells in the tumor. We examine an exciting new role for using selective inhibitors of the PI3K δ- and γ-isoforms as modulators of T-cell phenotype and function in immunotherapy. Herein we review the current literature on the implications of PI3K-δ and -γ inhibition in T-cell biology, discuss existing challenges in adoptive T-cell therapies and checkpoint blockade inhibitors, and highlight ongoing efforts and future directions to incorporate PI3K-δ and PI3K-γ as synergistic T-cell modulators in immunotherapy.

The Society for Immunotherapy of Cancer consensus statement on immunotherapy for the treatment of squamous cell carcinoma of the head and neck (HNSCC)

Head and neck cancers, including those of the lip and oral cavity, nasal cavity, paranasal sinuses, oropharynx, larynx and nasopharynx represent nearly 700,000 new cases and 380,000 deaths worldwide per annum, and account for over 10,000 annual deaths in the United States alone. Improvement in outcomes are needed for patients with recurrent and or metastatic squamous cell carcinoma of the head and neck (HNSCC). In 2016, the US Food and Drug Administration (FDA) granted the first immunotherapeutic approvals - the anti-PD-1 immune checkpoint inhibitors nivolumab and pembrolizumab - for the treatment of patients with recurrent squamous cell carcinoma of the head and neck (HNSCC) that is refractory to platinum-based regimens. The European Commission followed in 2017 with approval of nivolumab for treatment of the same patient population, and shortly thereafter with approval of pembrolizumab monotherapy for the treatment of recurrent or metastatic HNSCC in adults whose tumors express PD-L1 with a ≥ 50% tumor proportion score and have progressed on or after platinum-containing chemotherapy. Then in 2019, the FDA granted approval for PD-1 inhibition as first-line treatment for patients with metastatic or unresectable, recurrent HNSCC, approving pembrolizumab in combination with platinum and fluorouracil for all patients with HNSCC and pembrolizumab as a single agent for patients with HNSCC whose tumors express a PD-L1 combined positive score ≥ 1. These approvals marked the first new therapies for these patients since 2006, as well as the first immunotherapeutic approvals in this disease. In light of the introduction of these novel therapies for the treatment of patients with head and neck cancer, The Society for Immunotherapy of Cancer (SITC) formed an expert committee tasked with generating consensus recommendations for emerging immunotherapies, including appropriate patient selection, therapy sequence, response monitoring, adverse event management, and biomarker testing. These consensus guidelines serve as a foundation to assist clinicians' understanding of the role of immunotherapies in this disease setting, and to standardize utilization across the field for patient benefit. Due to country-specific variances in approvals, availability and regulations regarding the discussed agents, this panel focused solely on FDA-approved drugs for the treatment of patients in the U.S.

Immunotherapy Approaches Beyond PD-1 Inhibition: the Future of Cellular Therapy for Head and Neck Squamous Cell Carcinoma

OPINION STATEMENT

In a span of a few years, the surprising early successes of programmed cell death 1 (PD-1) inhibitors across a vast range of tumor types have transformed our understanding of cancer immunogenicity and provided proof of principle that T cells, if manipulated, can mediate meaningful tumor regression. In head and neck cancer, only a minority of patients respond to PD-1 therapy, but these small outcomes have fueled the enthusiasm for the next generation of immunotherapy-adoptive cell therapy-which employs recent advances in genetic engineering and cell culturing methods to generate T cells with enhanced anti-tumor efficacy for infusion back into the patient. Head and neck cancer is comprised of biologically distinct cancers, HPV-positive and HPV-negative, and the clinical responses to PD-1 inhibitors in both HPV-positive and HPV-negative head and neck patients have showcased better than any other cancer type that there are distinct pathways to immunogenicity that may lend themselves to different therapeutic approaches. Thus, head and neck cancer is uniquely poised to benefit from the personalized approach of adoptive cell therapy as well as provide a valuable platform to explore contrasting T cell modalities. In this article, we will review the growing portfolio of trials of adoptive cell therapies in head and neck cancer and discuss the future directions of this emerging new field.

Tackling molecular targets beyond PD-1/PD-L1: Novel approaches to boost patients' response to cancer immunotherapy

In the new era of immunotherapy, which has changed the clinical oncology practice guidelines, there is a pressing need for finding novel approaches to tune up the clinical outcomes of immunotherapy and extend its benefits to a wider cohort of cancer patients. Several non-classical molecular immune targets beyond PD-1/PD-L1 signaling were shown to be engaged as feedback resistance circuits to shut down the antitumor immune response mediated by the classical immune checkpoint inhibitors. Those include T-cell inducible co-stimulator (ICOS), CD40, CD47, V-domain Ig suppressor of T-cell activation (VISTA), cyclin-dependent kinase (CDK)12, enhancer of Zeste homolog 2 (EZH2), toll-like receptors (TLRs) and OX-40 (CD134). Herein we critically discussed the latest studies concerned with understanding the mechanisms involved in the negative clinical response to classical immunotherapies and strategies to optimize the efficacy of cancer immunotherapy through novel combinatorial approaches.

Intratumoral generation of 2-fluoroadenine to treat solid malignancies of the head and neck

This report describes treatment of locoregional head and neck squamous cell carcinoma (HNSCC) by an innovative, experimental strategy involving generation of a robust anti-cancer agent (2-fluoroadenine [F-Ade]) following transduction by Escherichia coli purine nucleoside phosphorylase (PNP) in a small number of tumor cells. F-Ade works by a unique mechanism of action (ablation of RNA and protein synthesis) and confers tumor regressions of otherwise refractory HNSCC in human subjects. Clinical studies have now advanced to a pivotal (registration-directed) trial involving locoregional HNSCC, with plans to begin subject enrollment late in 2018. The present review is the first to summarize use of PNP in the context of HNSCC, and provides background regarding this emerging anti-cancer approach.