Two recent clinical readouts highlight both the promise and limitations of therapeutic cancer vaccines.
On August 19, Moderna and Merck announced that the Phase III INTerpath-001 trial of intismeran autogene plus pembrolizumab met its endpoints for recurrence-free and distant metastasis-free survival in patients with resected stage IIB-IV melanoma. This is the first positive Phase III trial of an individualized neoantigen and mRNA-based cancer therapy, but detailed efficacy data are still unavailable. Nine days later, BioNTech and Genentech halted a Phase II trial of the individualized mRNA vaccine autogene cevumeran as adjuvant monotherapy in ctDNA-positive, resected stage II-III colorectal cancer after the study crossed a futility boundary.
The divergent outcomes sharpen a key question for the field: Is generating tumor-specific immunity enough, or must cancer vaccines also create conditions in which that immunity can function?
A new preclinical study from researchers at Northeastern University approaches that problem from a biomaterials perspective. The Boston-based researchers developed an injectable vaccine scaffold that combines prolonged tumor-antigen delivery with local oxygen generation, with the goal of simultaneously addressing antigen tolerance and hypoxia-mediated immunosuppression. According to the study, published in Cell Biomaterials, the approach generated cellular and humoral antitumor immunity, slowed established tumor growth, and extended survival in a mouse model of prostate cancer.
The platform, called Click O2-CryogelVAX, uses a macroporous cryogel—a porous, injectable biomaterial that serves as a local vaccine depot. Made from modified hyaluronic acid, its interconnected pores allow immune cells to infiltrate and interact with prostatic acid phosphatase (PAP), a prostate tumor-associated antigen, along with GM-CSF and the adjuvant Poly(I:C).
A challenge with biomaterial vaccines is retaining antigen long enough to stimulate immune cells: proteins physically trapped in hydrogels can load inefficiently and rapidly diffuse away. The researchers instead used click chemistry—a highly selective, biocompatible reaction that was garnered the 2022 Nobel Prize in Chemistry—to covalently tether PAP to the hyaluronic acid scaffold. This improved antigen retention and provided more sustained exposure to antigen-presenting cells.
Click conjugation improved antigen loading by over 90%, while physical encapsulation retained only 10%–18%. Critically, the oxygen-generating version did not permanently lock the antigen. Over 96 hours, Click O2-CryogelVAX released 90% of conjugated PAP, which may have allowed dendritic cells to recruit, load, and activate before migrating to draining lymph nodes and priming adaptive immunity.
The biomaterial’s second component addresses hypoxia. The scaffold incorporates calcium peroxide and catalase to generate oxygen locally for approximately 48 hours. Oxygen-generating cryogels reduced hypoxic leukocyte infiltration from 63%-75% to 41%-42% in vivo.
That distinction is potentially important because hypoxia is not simply a metabolic feature of solid tumors. Hypoxia-driven signaling can promote extracellular adenosine accumulation and impair dendritic-cell and effector T-cell activity, creating an environment hostile to productive antitumor immunity.
Click O2-CryogelVAX increased antigen uptake by conventional dendritic cells and expanded antigen-presenting cells and mature B cells in draining lymph nodes. Vaccination also promoted central-memory CD4+ and CD8+ T-cell populations, while antigen restimulation demonstrated increased TNF-α and IL-2 responses in CD8+ T cells and increased IFN-γ production under several conditions.
The investigators then tested the vaccine therapeutically against established TRAMP-C2 prostate tumors, an immunologically “cold” syngeneic model. Median survival was 47 days with bolus vaccination, 64 days with O2-CryogelVAX and 76 days with Click O2-CryogelVAX. The latter resulted in a 62% increase in median lifespan, and two animals maintained tumor control through the study endpoint.
These results should not be conflated with the clinical progress of individualized mRNA vaccines. Click O2-CryogelVAX remains a mouse-stage platform, used a tumor-associated self-antigen rather than patient-specific neoantigens, and has yet to undergo the toxicology and translational studies required for clinical development.
The clinical question is now whether cancer vaccines induce immunity and when that immunity leads to disease control. The cryogel study suggests antigen selection is only one variable. Antigen persistence, dendritic-cell activation, checkpoint inhibition, tumor immunogenicity, and microenvironment metabolism may determine whether vaccine-induced T cells can kill a tumor.
Therefore, cancer vaccines’ next generation may not be defined by better antigens but by strategies that make tumors more accommodating to vaccine-induced immunity.
