Cancer mRNA vaccines: clinical advances and future opportunities

mRNA vaccines have been revolutionary in terms of their rapid development and prevention of SARS-CoV-2 infections during the COVID-19 pandemic, and this technology has considerable potential for application to the treatment of cancer. Compared with traditional cancer vaccines based on proteins or peptides, mRNA vaccines reconcile the needs for both personalization and commercialization in a manner that is unique to each patient but not beholden to their HLA haplotype. A further advantage of mRNA vaccines is the availability of engineering strategies to improve their stability while retaining immunogenicity, enabling the induction of complementary innate and adaptive immune responses. Thus far, no mRNA-based cancer vaccines have received regulatory approval, although several phase I-II trials have yielded promising results, including in historically poorly immunogenic tumours. Furthermore, many early phase trials testing a wide range of vaccine designs are currently ongoing. In this Review, we describe the advantages of cancer mRNA vaccines and advances in clinical trials using both cell-based and nanoparticle-based delivery methods, with discussions of future combinations and iterations that might optimize the activity of these agents.

Intratumoral therapies in head and neck squamous cell carcinoma: A systematic review and future perspectives

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) presents an ideal scenario for intratumoral therapies (IT), due to its local recurrence pattern and frequent superficial extension. IT therapies aim to effect tumor regression by directly injecting antineoplastic agents into lesions. However, there is a lack of updated evidence regarding IT therapies in HNSCC.

PATIENTS AND METHODS

A systematic literature search (CRD42023462291) was conducted using WebOfScience, ClinicalTrials.gov, and conference abstracts from ESMO and ASCO, identifying for IT clinical trials in patients with HNSCC, from database creation to September 12th, 2023. Efficacy as well as safety (grade ≥ 3 treatment-related adverse events[trAEs]) were reported.

RESULTS

After evaluation of 1180 articles identified by the systematic search, 31 studies treating 948 patients were included. IT injectables were categorized as chemotherapies with or without electroporation (k = 4, N = 268), oncolytic viruses, plasmids, and bacteria-based (k = 16, N = 446), immunotherapies and EGFR-based therapies (k = 5, N = 160), radioenhancer particles (k = 2, N = 68), and calcium electroporation (k = 1, n = 6). EGFR-antisense plasmids, NBTXR3 radioenhancer and immune innate agonists show best overall response rates, at 83 %, 81 % and 44 % respectively. Eleven (35 %) studies added systemic therapy or radiotherapy to the IT injections. No study used predictive biomarkers to guide patient selection. 97 % studies were phase I-II. Safety-wise, electroporation and epinephrine-based injectable trials had significant local symptoms such as necrosis, fistula formation and post-injection dysphagia. Treatment-related tumor haemorrhages of various grades were described in several trials. Grade ≥ 3 trAEs attributable to the other therapies mainly comprised general symptoms such as fatigue. There were 3 injectable-related deaths across the systematic review.

CONCLUSION

This is the first review to summarize all available evidence of IT in HNSCC. As of today, IT therapies lack sufficient evidence to recommend their use in clinical practice. Continuing research on potential molecules, patient selection, safe administration of injections and controlled randomized trials are needed to assess their added benefit.

Intralesional Treatments for Invasive Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (cSCC) is the second most frequent cancer in humans and has the potential to progress locally, metastasize, and cause death in a subset of patients. cSCC is especially common in the elderly, and it will probably represent a major health concern in the near future. Surgery is the standard treatment for cSCC, but intralesional therapies can sometimes be considered for certain patients and under certain circumstances. The choice of intralesional treatment depends on the patient's characteristics and the clinician's previous experience and expertise. Here we are reviewing intralesional treatments for cSCC and keratoacanthoma (KA). We have started with some classic drugs, such as methotrexate and 5-fluorouracil, bleomycin, interferon, and cryosurgery, but also comment on electrochemotherapy. Finally, we have focused on novel therapies, some of which are under development, and future perspectives, including intralesional immunotherapy and oncolytic viruses.

mRNA melanoma vaccine revolution spurred by the COVID-19 pandemic

The advent of mRNA vaccines represents a significant advance in the field of vaccinology. While several vaccine approaches (mRNA, DNA, recombinant protein, and viral-vectored vaccines) had been investigated at the start of the COVID-19 pandemic, mRNA vaccines quickly gained popularity due to superior immunogenicity at a low dose, strong safety/tolerability profiles, and the possibility of rapid vaccine mass manufacturing and deployment to rural regions. In addition to inducing protective neutralizing antibody responses, mRNA vaccines can also elicit high-magnitude cytotoxic T-cell responses comparable to natural viral infections; thereby, drawing significant interest from cancer immunotherapy experts. This mini-review will highlight key developmental milestones and lessons we have learned from mRNA vaccines during the COVID-19 pandemic, with a specific emphasis on clinical trial data gathered so far for mRNA vaccines against melanoma and other forms of cancer.

Applications and clinical trial landscape using Toll-like receptor agonists to reduce the toll of cancer

Toll-like receptors (TLRs), which serve as a bridge between innate and adaptive immunity, may be viable treatment targets. TLRs are the first line of defense against microbes and activate signaling cascades that induce immune and inflammatory responses. Patients with "hot" versus "cold" tumors may respond more favorably to immune checkpoint inhibition, and through their downstream effects, TLR agonists have the potential to convert "cold tumors" into "hot tumors" making TLRs in combination with immune checkpoint inhibitors, potential targets for cancer therapies. Imiquimod is a topical TLR7 agonist, approved by the FDA for antiviral and skin cancer treatments. Other TLR adjuvants are used in several vaccines including Nu Thrax, Heplisav, T-VEC, and Cervarix. Many TLR agonists are currently in development as both monotherapy and in combination with immune checkpoint inhibitors. In this review, we describe the TLR agonists that are being evaluated clinically as new therapies for solid tumors.

mRNA-Based Therapeutics in Cancer Treatment

Over the past two decades, significant technological innovations have led to messenger RNA (mRNA) becoming a promising option for developing prophylactic and therapeutic vaccines, protein replacement therapies, and genome engineering. The success of the two COVID-19 mRNA vaccines has sparked new enthusiasm for other medical applications, particularly in cancer treatment. In vitro-transcribed (IVT) mRNAs are structurally designed to resemble naturally occurring mature mRNA. Delivery of IVT mRNA via delivery platforms such as lipid nanoparticles allows host cells to produce many copies of encoded proteins, which can serve as antigens to stimulate immune responses or as additional beneficial proteins for supplements. mRNA-based cancer therapeutics include mRNA cancer vaccines, mRNA encoding cytokines, chimeric antigen receptors, tumor suppressors, and other combination therapies. To better understand the current development and research status of mRNA therapies for cancer treatment, this review focused on the molecular design, delivery systems, and clinical indications of mRNA therapies in cancer.

Engaging Pattern Recognition Receptors in Solid Tumors to Generate Systemic Antitumor Immunity

Malignant tumors frequently exploit innate immunity to evade immune surveillance. The priming, function, and polarization of antitumor immunity fundamentally depends upon context provided by the innate immune system, particularly antigen presenting cells. Such context is determined in large part by sensing of pathogen specific and damage associated features by pathogen recognition receptors (PRRs). PRR activation induces the delivery of T cell priming cues (e.g. chemokines, co-stimulatory ligands, and cytokines) from antigen presenting cells, playing a decisive role in the cancer immunity cycle. Indeed, endogenous PRR activation within the tumor microenvironment (TME) has been shown to generate spontaneous antitumor T cell immunity, e.g., cGAS-STING mediated activation of antigen presenting cells after release of DNA from dying tumor cells. Thus, instigating intratumor PRR activation, particularly with the goal of generating Th1-promoting inflammation that stokes endogenous priming of antitumor CD8⁺ T cells, is a growing area of clinical investigation. This approach is analogous to in situ vaccination, ultimately providing a personalized antitumor response against relevant tumor associated antigens. Here I discuss clinical stage intratumor modalities that function via activation of PRRs. These approaches are being tested in various solid tumor contexts including melanoma, colorectal cancer, glioblastoma, head and neck squamous cell carcinoma, bladder cancer, and pancreatic cancer. Their mechanism (s) of action relative to other immunotherapy approaches (e.g., antigen-defined cancer vaccines, CAR T cells, dendritic cell vaccines, and immune checkpoint blockade), as well as their potential to complement these approaches are also discussed. Examples to be reviewed include TLR agonists, STING agonists, RIG-I agonists, and attenuated or engineered viruses and bacterium. I also review common key requirements for effective in situ immune activation, discuss differences between various strategies inclusive of mechanisms that may ultimately limit or preclude antitumor efficacy, and provide a summary of relevant clinical data.

The treatment of advanced melanoma: a review of systemic and local therapies in combination with immune checkpoint inhibitors in phase 1 and 2 clinical trials

INTRODUCTION

While the incidence of melanoma continues to rise, the mortality of the disease appears to have stabilized. This may, in part, be due to the development and application of immune checkpoint inhibitors as standard of care in advanced melanoma. However, many patients do not respond to these therapies alone. Combining immune checkpoint inhibitors with other classes of therapeutics appears to be a promising direction to improve response and survival in advanced melanoma.

AREAS COVERED

This review article aims to discuss phase 1 and 2 clinical trials examining immune checkpoint inhibitors in combination therapy for the treatment of advanced, unresectable melanoma. In particular, these regimens include various kinase inhibitors, tumor-infiltrating lymphocytes, toll-like receptor agonists, cytokines, and oncolytic viral therapies. The combinations under discussion include both systemic and combination systemic/local therapies.

EXPERT OPINION

Drug combinations discussed here appear to be promising therapeutic regimens for advanced melanoma. Improved understanding of the mechanisms of primary, adaptive, and acquired resistance to immune checkpoint inhibitors may guide the development of future combination regimens.