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To prospectively determine whether brain tumors will respond to immune checkpoint inhibitors (ICIs), we developed a novel mRNA vaccine as a viral mimic to elucidate cytokine release from brain cancer cells in vitro. Our results indicate that cytokine signatures following mRNA challenge differ substantially from ICI responsive versus non-responsive murine tumors. These findings allow for creation of a diagnostic assay to quickly assess brain tumor immunogenicity, allowing for informed treatment with ICI or lack thereof in poorly immunogenic settings.

BACKGROUND Recurrent PCNSBLs represent a therapeutic challenge. Up to 60% of PCNSBL patients relapse to later face survival rates as low as 22%. Unfortunately, tumor heterogeneity and off-target effects have limited the success of immunotherapy against PCNSBL. METHODS We propose a novel immunotherapy to overcome PCNSBL heterogeneity and off-target effects in an exquisitely tumor specific manner using nanoparticle vaccination, capable of delivering personalized tumor derived mRNAs, that induces systemic orchestration of innate and adaptive immunity. We target tumor antigens derived from the B cell receptor (i.e., heavy chain immunoglobulin - IgH) clonotypes. IgH clonotypes are hypervariable gene rearrangements clonally generated by B cells. Tumor IgH clonotypes are unique for each malignant B cell clone and hence attractive immune targets, not shared by normal B cell clones avoiding undesirable off-target effects. RESULTS RNA-NPs can reprogram tumor microenvironment while activating the innate immunity via IFN type I (i.e., IFNα) and priming of hypervariable region clonotype specific T cell responses in naïve mice. We determined the rearranged IgH sequences (predominant clone 99% and nine additional clones with frequencies < 1%) of clinically relevant inbred murine PCNSBL models (BAL17 and A20) by PCR. The number of identified clonotypes confirmed the IgH variability observed in human B cell hematological malignancies. In preliminary experiments targeting lymphoma derived single clonotypes with RNA-NPs, we showed the feasibility of priming in-vivo T cells specific against hypervariable regions after 3 weekly i.v. RNA-NPs (median IFNγ: 58 pg/ml; range: 50-70 pg/ml vs controls < 30 pg/ml; p=0.008). Targeting of clonotype RNA-NPs was associated with decreased tumor growth (p=0.04). Interestingly, we have observed tumor reactive lymphangiogenesis that communicates with regional skull bone marrow observed in 3D microscopy that might direct future routes of RNA-NP administration. CONCLUSION Our RNA-NP systemic vaccination platform can induce PCNSBL clonotype specific T cell responses, sparing normal tissues.

BACKGROUND Although mRNA vaccines have been deployed with great success against COVID-19, unlocking this technology against glioblastoma will necessitate new lipid-nanoparticle formulations that overcome cancer tolerance and immunosuppression. OBJECTIVE/METHODS We sought to develop a novel mRNA vaccine system to make tolerogenic tumor antigens appear more dangerous through use of unmodified nucleosides (pathogen associated molecular patterns, PAMPs) and highly cationic lipid shells that elicit a systemic damage response against cancer antigens. RESULTS We developed a novel vaccine formulation that increases payload packaging of tumor amplified mRNA into multilamellar (onion-shaped) particles for systemic (intravenous) administration. We demonstrate significant immunogenicity and efficacy of multilamellar RNA-NPs in syngeneic murine models for high-grade glioma (KR158b-pp65), and diffuse midline glioma (H3K27M DMG). Remarkably, RNA-NPs significantly improve median survival outcomes of DMG bearing mice beginning therapy at endpoint (Day 35 after midline intracranial implantation). Unlike prototypical mRNA vaccines that activate endosomal toll-like receptors (i.e. TLR7), multilamellar RNA-NPs elicit immunologic response predominantly through intracellular pathogen recognition receptors (RIG-I); long-term survival benefits from RNA-NPs were completely abrogated in RIG-I knockout mice. In canines (pet dogs) with spontaneous gliomas, RNA-NPs elicit massive recruitment/activation of peripheral blood mononuclear cells (PBMCs) which correlate with their trafficking into lymphoreticular organs (in follow-up murine studies). In canines receiving neoadjuvant RNA-NPs, prior to glioma biopsy, we see significant reprogramming of the glioma microenvironment with increased gene signatures for antigen processing/presentation, interferon signaling and cytotoxicity. Upon translation into human clinical trials for glioblastoma patients (NCT04573140), RNA-NPs elicit rapid (within hours) release of cytokines (e.g. IL-1, IL-6, IL-12 TNF-α, interferons) and chemokines (e.g. MIP1α, MCP-1, IP-10), which correlate with mobilization of PBMCs and activation of dendritic cells/CD8 lymphocytes. CONCLUSION First-in-human application of systemic multilamellar RNA-NP vaccines results in significant biologic effects and rapid immunologic reprogramming.

BACKGROUND Diffuse Intrinsic Pontine Glioma (DIPG) is uniformly fatal. Upon diagnosis, DIPG cannot be safely debulked and systemic therapies have unproven benefit. Immunotherapy can overcome these obstacles, but objective responses are rare; and cancer antigens, even when tumor specific (i.e. H3K27M), are usually poorly immunogenic. OBJECTIVE We sought to develop a murine model of diffuse midline glioma (DMG) that better recapitulates human disease. In these models, we tested different iterations of mRNA loaded nanoparticle (NP) vaccines for their therapeutic effect. APPROACH: We implanted murine gliomas (expressing H3K27M mutation) midline into developing neonatal brains. We manufactured different mRNA constructs encoding for foreign proteins (e.g. GFP), H3K27M or wildtype H3K27 and evaluated immunogenicity and anti-tumor efficacy. These mRNA vaccines were layered into lipid particles (RNA-NP) and administered intravenously when animals became acutely symptomatic (similar to when patients are diagnosed). RESULTS Surprisingly, all mRNA constructs tested were sufficient to elicit anti-tumor efficacy against DMGs. This was true for both antigen specific (H3K27M) and non-antigen specific constructs (GFP, H3K27 wildtype). While H3K27M encoding RNA-NPs were superior to H3K27 wildtype encoding RNA-NPs (p=0.057), the adaptive immune effects appear marginal relative to the innate immune responses generated by all RNA-NP constructs. These innate responses are characterized by induction of type I interferon response from plasmacytoid DCs. Interestingly, these effects could not be recapitulated in murine models of adult type glioblastoma (KR158b) which required antigen specificity for induction of anti-tumor efficacy. CONCLUSION These data suggest that pediatric gliomas may be particularly sensitive to innate immunity. We have optimized development of a target H3K27M mRNA construct that balances innate and adaptive bi-directional immune induction. We are completing FDA-IND enabling data to support translation of H3K27M loaded RNA-NPs into human clinical trials.

Introduction: Chimeric antigen receptor (CAR) T-cells have revolutionized therapies for B-cell malignancies. However, while ethnic and racial minorities or those with obesity represent medically underserved populations for whom cancer outcomes are worse, it is unknown whether these factors also negatively impact outcomes of CAR T-cells. Methods: We conducted a retrospective review of 5 unique phase I CAR T-cell trials for children and adults with B-cell malignancies (including CD19, CD22 and BCMA targeted CAR T-cells for B-cell acute lymphoblastic leukemia (B-ALL), B-cell non-Hodgkin lymphoma (NHL) and multiple myeloma (MM)). In addition to evaluating basic demographics, complete remission (CR) rates and cytokine release syndrome (CRS) severity, graded by ASTCT, were stratified by race (white vs non-white), ethnicity and obesity, defined as BMI > 30. All individual protocols were IRB approved, and the retrospective study for this analysis is registered at: Clinicaltrials.gov NCT03827343. Statistics were done in GraphPad Prism, using non-parametric tests with p/= 3 CRS occurred in 35/185 (18.9%) patients and did not vary by race. Grade >/= 3 CRS in white patients was 30/154 (19.5%) vs non-White patients was 5/31 (16.1%); p=NS. Rates of Grade >/= 3 CRS were higher in Hispanic patients, (13/45, 28.9%) versus non-Hispanic patients (21/139, 15.1%), p=0.05 and in obese patients, (9/28, 32.1%) vs non-obese 26/157 (16.6%); p=NS). Conclusion: While CR rates did not vary by race (white versus non-white), ethnicity or obesity, a closer analysis by racial sub-populations and at active dose levels is a critical next step to evaluate for subtle disparities. Hispanic patients and those with obesity had a trend towards higher rates of Grade >/= 3 CRS, which needs further study. Given the tremendous potential of CAR T-cells across diverse populations and ability to overcome chemotherapeutic resistance seen in minority populations, CAR T-cells may represent an opportunity to improve outcomes for underserved populations without substantially increasing toxicity. Citation Format: Paul Borgman, John Ligon, Bonnie Yates, Haneen Shalabi, Toni Foley, Lauren Little, Jennifer Brudno, Lekha Mikkilineni, James Kochenderfer, Nirali N. Shah. The impact of race, ethnicity and obesity on CAR T-cell outcomes [abstract]. In: Proceedings of the AACR Virtual Conference: 14th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2021 Oct 6-8. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr PO-111.