Getting personal in metastatic melanoma: neoantigen-based vaccines as a new therapeutic strategy

Breaking the Mold: Trailblazing Melanoma Therapy Beyond Checkpoint Through Innovative Approaches

Melanoma has long been a difficult malignancy to treat with low response rates to standard chemotherapies. In recent years, the use of immune checkpoint inhibitors have demonstrated promising results, paving the way for the use of the rapidly developing novel immune targeting therapies. In this review, we look beyond immune checkpoint inhibitor treatments and summarize several emerging treatment strategies for melanoma, including neoantigen vaccines, conventional antibody drug-conjugates, and bispecific T-cell engager therapies.

BRAFV600E Metastatic Melanoma Journey: A Perspective from a Patient and his Oncologist

BACKGROUND

This article is co-authored by a patient with BRAFV600E metastatic melanoma and his treating oncologist.

CASE DESCRIPTION

The patient describes how he coped with his diagnosis and treatment. He details the pathway of his melanoma treatment, which has spanned over 10 years, including surgical interventions, medical treatment, and participation in clinical trials. He relates his experience of living with the disease-and the adverse effects of treatment-in the long term. The clinical perspective of his treating oncologist reviews the diagnostic process and explains how the therapeutic options were selected for and with the patient. The oncologist also addresses the integration of the patient into clinical trials involving programmed death-1 (PD-1) inhibitors and BRAF/MEK inhibitors. Challenges related to the adverse effects that occurred and the personalised treatment of the patient are also discussed. Finally, the article evaluates current advances in treatment and future therapeutic approaches.

CONCLUSIONS

This case highlights the challenges of identifying which therapeutic options are most appropriate for individual patients with BRAFV600E metastatic melanoma.

Tumor Burden Dictates the Neoantigen Features Required to Generate an Effective Cancer Vaccine

Tumor neoantigens (nAg) represent a promising target for cancer immunotherapy. The identification of nAgs that can generate T-cell responses and have therapeutic activity has been challenging. Here, we sought to unravel the features of nAgs required to induce tumor rejection. We selected clinically validated Great Ape-derived adenoviral vectors (GAd) as a nAg delivery system for differing numbers and combinations of nAgs. We assessed their immunogenicity and efficacy in murine models of low to high disease burden, comparing multi-epitope versus mono-epitope vaccines. We demonstrated that the breadth of immune response is critical for vaccine efficacy and having multiple immunogenic nAgs encoded in a single vaccine improves efficacy. The contribution of each single neoantigen was examined, leading to the identification of 2 nAgs able to induce CD8+ T cell-mediated tumor rejection. They were both active as individual nAgs in a setting of prophylactic vaccination, although to different extents. However, the efficacy of these single nAgs was lost in a setting of therapeutic vaccination in tumor-bearing mice. The presence of CD4+ T-cell help restored the efficacy for only the most expressed of the two nAgs, demonstrating a key role for CD4+ T cells in sustaining CD8+ T-cell responses and the necessity of an efficient recognition of the targeted epitopes on cancer cells by CD8+ T cells for an effective antitumor response. This study provides insight into understanding the determinants of nAgs relevant for effective treatment and highlights features that could contribute to more effective antitumor vaccines. See related Spotlight by Slingluff Jr, p. 382.

Are we getting closer to a successful neoantigen cancer vaccine?

Although significant advances in immunotherapy have revolutionized the treatment of many cancer types over the past decade, the field of vaccine therapy, an important component of cancer immunotherapy, despite decades-long intense efforts, is still transmitting signals of promises and awaiting strong data on efficacy to proceed with regulatory approval. The field of cancer vaccines faces standard challenges, such as tumor-induced immunosuppression, immune response in inhibitory tumor microenvironment (TME), intratumor heterogeneity (ITH), permanently evolving cancer mutational landscape leading to neoantigens, and less known obstacles: neoantigen gain/loss upon immunotherapy, the timing and speed of appearance of neoantigens and responding T cell clonotypes and possible involvement of immune interference/heterologous immunity, in the complex interplay between evolving tumor epitopes and the immune system. In this review, we discuss some key issues related to challenges hampering the development of cancer vaccines, along with the current approaches focusing on neoantigens. We summarize currently well-known ideas/rationales, thus revealing the need for alternative vaccine approaches. Such a discussion should stimulate vaccine researchers to apply out-of-box, unconventional thinking in search of new avenues to deal with critical, often yet unaddressed challenges on the road to a new generation of therapeutics and vaccines.

Prognostic and predictive biomarkers in melanoma

Biomarkers help to inform the clinical management of patients with melanoma. For patients with clinically localised primary melanoma, biomarkers can help to predict post-surgical outcome (including via the use of risk prediction tools), better select patients for sentinel lymph node biopsy, and tailor catch-all follow-up protocols to the individual. Systemic drug treatments, including immune checkpoint inhibitor (ICI) therapies and BRAF-targeted therapies, have radically improved the prognosis of metastatic (stage III and IV) cutaneous melanoma patients, and also shown benefit in the earlier setting of stage IIB/C primary melanoma. Unfortunately, a response is far from guaranteed. Here, we review clinically relevant, established, and emerging, prognostic, and predictive pathological biomarkers that refine clinical decision-making in primary and metastatic melanoma patients. Gene expression profile assays and nomograms are emerging tools for prognostication and sentinel lymph node risk prediction in primary melanoma patients. Biomarkers incorporated into clinical practice guidelines include BRAF V600 mutations for the use of targeted therapies in metastatic cutaneous melanoma, and the HLA-A∗02:01 allele for the use of a bispecific fusion protein in metastatic uveal melanoma. Several predictive biomarkers have been proposed for ICI therapies but have not been incorporated into Australian clinical practice guidelines. Further research, validation, and assessment of clinical utility is required before more prognostic and predictive biomarkers are fluidly integrated into routine care.

Refining mutanome-based individualised immunotherapy of melanoma using artificial intelligence

Using the particular nature of melanoma mutanomes to develop medicines that activate the immune system against specific mutations is a game changer in immunotherapy individualisation. It offers a viable solution to the recent rise in resistance to accessible immunotherapy alternatives, with some patients demonstrating innate resistance to these drugs despite past sensitisation to these agents. However, various obstacles stand in the way of this method, most notably the practicality of sequencing each patient's mutanome, selecting immunotherapy targets, and manufacturing specific medications on a large scale. With the robustness and advancement in research techniques, artificial intelligence (AI) is a potential tool that can help refine the mutanome-based immunotherapy for melanoma. Mutanome-based techniques are being employed in the development of immune-stimulating vaccines, improving current options such as adoptive cell treatment, and simplifying immunotherapy responses. Although the use of AI in these approaches is limited by data paucity, cost implications, flaws in AI inference capabilities, and the incapacity of AI to apply data to a broad population, its potential for improving immunotherapy is limitless. Thus, in-depth research on how AI might help the individualisation of immunotherapy utilising knowledge of mutanomes is critical, and this should be at the forefront of melanoma management.