An Fc-inert PD-L1×4-1BB bispecific antibody mediates potent anti-tumor immunity in mice by combining checkpoint inhibition and conditional 4-1BB co-stimulation

Immune checkpoint inhibitors (ICI) targeting the PD-1/PD-L1 axis have changed the treatment paradigm for advanced solid tumors; however, many patients experience treatment resistance. In preclinical models 4-1BB co-stimulation synergizes with ICI by activating cytotoxic T- and NK-cell-mediated anti-tumor immunity. Here we characterize the mechanism of action of a mouse-reactive Fc-inert PD-L1×4-1BB bispecific antibody (mbsAb-PD-L1×4-1BB) and provide proof-of-concept for enhanced anti-tumor activity. In reporter assays mbsAb-PD-L1×4-1BB exhibited conditional 4-1BB agonist activity that was dependent on simultaneous binding to PD-L1. mbsAb-PD-L1×4-1BB further blocked the PD-L1/PD-1 interaction independently of 4-1BB binding. By combining both mechanisms, mbsAb-PD-L1×4-1BB strongly enhanced T-cell proliferation, cytokine production and antigen-specific cytotoxicity using primary mouse cells in vitro. Furthermore, mbsAb-PD-L1×4-1BB exhibited potent anti-tumor activity in the CT26 and MC38 models in vivo, leading to the rejection of CT26 tumors that were unresponsive to PD-L1 blockade alone. Anti-tumor activity was associated with increased tumor-specific CD8⁺ T cells and reduced regulatory T cells within the tumor microenvironment and tumor-draining lymph nodes. In immunocompetent tumor-free mice, mbsAb-PD-L1×4-1BB treatment neither induced T-cell infiltration into the liver nor elevated liver enzymes in the blood. Dual targeting of PD-L1 and 4-1BB with a bispecific antibody may therefore address key limitations of first generation 4-1BB-agonistic antibodies, and may provide a novel approach to improve PD-1/PD-L1 checkpoint blockade.

BNT162b2 vaccine induces neutralizing antibodies and poly-specific T cells in humans

BNT162b2, a nucleoside-modified mRNA formulated in lipid nanoparticles that encodes the SARS-CoV-2 spike glycoprotein (S) stabilized in its prefusion conformation, has demonstrated 95% efficacy in preventing COVID-19¹. Here we extend a previous phase-I/II trial report² by presenting data on the immune response induced by BNT162b2 prime-boost vaccination from an additional phase-I/II trial in healthy adults (18-55 years old). BNT162b2 elicited strong antibody responses: at one week after the boost, SARS-CoV-2 serum geometric mean 50% neutralizing titres were up to 3.3-fold above those observed in samples from individuals who had recovered from COVID-19. Sera elicited by BNT162b2 neutralized 22 pseudoviruses bearing the S of different SARS-CoV-2 variants. Most participants had a strong response of IFNγ⁺ or IL-2⁺ CD8⁺ and CD4⁺ T helper type 1 cells, which was detectable throughout the full observation period of nine weeks following the boost. Using peptide-MHC multimer technology, we identified several BNT162b2-induced epitopes that were presented by frequent MHC alleles and conserved in mutant strains. One week after the boost, epitope-specific CD8⁺ T cells of the early-differentiated effector-memory phenotype comprised 0.02-2.92% of total circulating CD8⁺ T cells and were detectable (0.01-0.28%) eight weeks later. In summary, BNT162b2 elicits an adaptive humoral and poly-specific cellular immune response against epitopes that are conserved in a broad range of variants, at well-tolerated doses.

BNT162b2 vaccine induces neutralizing antibodies and poly-specific T cells in humans

BNT162b2, a nucleoside-modified mRNA formulated in lipid nanoparticles that encodes the SARS-CoV-2 spike glycoprotein (S) stabilized in its prefusion conformation, has demonstrated 95% efficacy in preventing COVID-19¹. Here we extend a previous phase-I/II trial report² by presenting data on the immune response induced by BNT162b2 prime-boost vaccination from an additional phase-I/II trial in healthy adults (18-55 years old). BNT162b2 elicited strong antibody responses: at one week after the boost, SARS-CoV-2 serum geometric mean 50% neutralizing titres were up to 3.3-fold above those observed in samples from individuals who had recovered from COVID-19. Sera elicited by BNT162b2 neutralized 22 pseudoviruses bearing the S of different SARS-CoV-2 variants. Most participants had a strong response of IFNγ⁺ or IL-2⁺ CD8⁺ and CD4⁺ T helper type 1 cells, which was detectable throughout the full observation period of nine weeks following the boost. Using peptide-MHC multimer technology, we identified several BNT162b2-induced epitopes that were presented by frequent MHC alleles and conserved in mutant strains. One week after the boost, epitope-specific CD8⁺ T cells of the early-differentiated effector-memory phenotype comprised 0.02-2.92% of total circulating CD8⁺ T cells and were detectable (0.01-0.28%) eight weeks later. In summary, BNT162b2 elicits an adaptive humoral and poly-specific cellular immune response against epitopes that are conserved in a broad range of variants, at well-tolerated doses.

mRNA therapeutics in cancer immunotherapy

Synthetic mRNA provides a template for the synthesis of any given protein, protein fragment or peptide and lends itself to a broad range of pharmaceutical applications, including different modalities of cancer immunotherapy. With the ease of rapid, large scale Good Manufacturing Practice-grade mRNA production, mRNA is ideally poised not only for off-the shelf cancer vaccines but also for personalized neoantigen vaccination. The ability to stimulate pattern recognition receptors and thus an anti-viral type of innate immune response equips mRNA-based vaccines with inherent adjuvanticity. Nucleoside modification and elimination of double-stranded RNA can reduce the immunomodulatory activity of mRNA and increase and prolong protein production. In combination with nanoparticle-based formulations that increase transfection efficiency and facilitate lymphatic system targeting, nucleoside-modified mRNA enables efficient delivery of cytokines, costimulatory receptors, or therapeutic antibodies. Steady but transient production of the encoded bioactive molecule from the mRNA template can improve the pharmacokinetic, pharmacodynamic and safety properties as compared to the respective recombinant proteins. This may be harnessed for applications that benefit from a higher level of expression control, such as chimeric antigen receptor (CAR)-modified adoptive T-cell therapies. This review highlights the advancements in the field of mRNA-based cancer therapeutics, providing insights into key preclinical developments and the evolving clinical landscape.

BNT162b vaccines protect rhesus macaques from SARS-CoV-2

A safe and effective vaccine against COVID-19 is urgently needed in quantities that are sufficient to immunize large populations. Here we report the preclinical development of two vaccine candidates (BNT162b1 and BNT162b2) that contain nucleoside-modified messenger RNA that encodes immunogens derived from the spike glycoprotein (S) of SARS-CoV-2, formulated in lipid nanoparticles. BNT162b1 encodes a soluble, secreted trimerized receptor-binding domain (known as the RBD-foldon). BNT162b2 encodes the full-length transmembrane S glycoprotein, locked in its prefusion conformation by the substitution of two residues with proline (S(K986P/V987P); hereafter, S(P2) (also known as P2 S)). The flexibly tethered RBDs of the RBD-foldon bind to human ACE2 with high avidity. Approximately 20% of the S(P2) trimers are in the two-RBD 'down', one-RBD 'up' state. In mice, one intramuscular dose of either candidate vaccine elicits a dose-dependent antibody response with high virus-entry inhibition titres and strong T-helper-1 CD4+ and IFNγ+CD8+ T cell responses. Prime-boost vaccination of rhesus macaques (Macaca mulatta) with the BNT162b candidates elicits SARS-CoV-2-neutralizing geometric mean titres that are 8.2-18.2× that of a panel of SARS-CoV-2-convalescent human sera. The vaccine candidates protect macaques against challenge with SARS-CoV-2; in particular, BNT162b2 protects the lower respiratory tract against the presence of viral RNA and shows no evidence of disease enhancement. Both candidates are being evaluated in phase I trials in Germany and the USA1-3, and BNT162b2 is being evaluated in an ongoing global phase II/III trial (NCT04380701 and NCT04368728).

A noninflammatory mRNA vaccine for treatment of experimental autoimmune encephalomyelitis

The ability to control autoreactive T cells without inducing systemic immune suppression is the major goal for treatment of autoimmune diseases. The key challenge is the safe and efficient delivery of pharmaceutically well-defined antigens in a noninflammatory context. Here, we show that systemic delivery of nanoparticle-formulated 1 methylpseudouridine-modified messenger RNA (m1Ψ mRNA) coding for disease-related autoantigens results in antigen presentation on splenic CD11c+ antigen-presenting cells in the absence of costimulatory signals. In several mouse models of multiple sclerosis, the disease is suppressed by treatment with such m1Ψ mRNA. The treatment effect is associated with a reduction of effector T cells and the development of regulatory T cell (Treg cell) populations. Notably, these Treg cells execute strong bystander immunosuppression and thus improve disease induced by cognate and noncognate autoantigens.

Dexamethasone premedication suppresses vaccine-induced immune responses against cancer

Glucocorticosteroids (GCS) have an established role in oncology and are administered to cancer patients in routine clinical care and in drug development trials as co-medication. Given their strong immune-suppressive activity, GCS may interfere with immune-oncology drugs. We are developing a therapeutic cancer vaccine, which is based on a liposomal formulation of tumor-antigen encoding RNA (RNA-LPX) and induces a strong T-cell response both in mice as well as in humans. In this study, we investigated in vivo in mice and in human PBMCs the effect of the commonly used long-acting GCS Dexamethasone (Dexa) on the efficacy of this vaccine format, with a particular focus on antigen-specific T-cell immune responses.

We show that Dexa, when used as premedication, substantially blunts RNA-LPX vaccine-mediated immune effects. Premedication with Dexa inhibits vaccine-dependent induction of serum cytokines and chemokines and reduces both the number and activation of splenic conventional dendritic cells (cDC) expressing vaccine-encoded antigens. Consequently, priming of functional effector T cells and therapeutic activity is significantly impaired. Interestingly, responses are less impacted when Dexa is administered post-vaccination. Consistent with this observation, although many inflammatory cytokines are reduced, IFNα, a key cytokine in T-cell priming, is less impacted and antigen expression by cDCs is intact. These findings warrant special caution when combining GCS with immune therapies relying on priming and activation of antigen-specific T cells and suggest that careful sequencing of these treatments may preserve T-cell induction.

mRNA: A Versatile Molecule for Cancer Vaccines

mRNA vaccines are finally ready to assume their rightful place at the forefront of nucleic acid- based vaccines. Major achievements within the last two decades have turned this highly versatile molecule into a safe and very attractive pharmaceutical platform that combines many positive attributes able to address a broad range of diseases, including cancer. The simplicity of mRNA vaccines greatly reduces complications generally associated with the production of biological vaccines. Intrinsic costimulatory and inflammatory triggers in addition to the provision of the antigenic information makes mRNA an all- in-one molecule that does not need additional adjuvants and that does not pose the risk of genomic integration. Clinical studies in various cancer types are moving forward and promising results with favorable clinical outcome are awaited. This review will recapitulate conceptual, mechanistic and immune-related features of this highly versatile molecule, elucidate how these features have been addressed in the past, and how comprehensive understanding can foster further optimization for broad application possibilities in cancer treatment.

Translating nanoparticulate-personalized cancer vaccines into clinical applications: case study with RNA-lipoplexes for the treatment of melanoma

The development of nucleic acid based vaccines against cancer has gained considerable momentum through the advancement of modern sequencing technologies and on novel RNA-based synthetic drug formats, which can be readily adapted following identification of every patient's tumor-specific mutations. Furthermore, affordable and individual ‘on demand’ production of molecularly optimized vaccines should allow their application in large groups of patients. This has resulted in the therapeutic concept of an active personalized cancer vaccine, which has been brought into clinical testing. Successful trials have been performed by intranodal administration of sterile isotonic solutions of synthetic RNA vaccines. The second generation of RNA vaccines which is currently being developed encompasses intravenously injectable RNA nanoparticle formulations (lipoplexes), made up from lipid excipients, denoted RNA(LIP). A first product that has made its way from bench to bedside is a therapeutic vaccine for intravenous administration based on a fixed set of four RNA lipoplex drug products, each encoding for one shared tumor antigen (Lipoplex Melanoma RNA Immunotherapy, ‘Lipo-MERIT’). This article describes the steps for translating these novel RNA nanomedicines into clinical trials.

Abstract CT032: A first-in-human phase I/II clinical trial assessing novel mRNA-lipoplex nanoparticles for potent cancer immunotherapy in patients with malignant melanoma

Immunotherapeutic approaches have evolved as promising and valid alternatives to available conventional cancer treatments. Amongst others, vaccination with tumor antigen-encoding RNAs by local administration is currently successfully employed in various clinical trials. To allow for a more efficient targeting of antigen-presenting cells (APCs) and to overcome potential technical challenges associated with local administration, we have developed a novel RNA immunotherapeutic for systemic application based on a fixed set of four liposome complexed RNA drug products (RNA(LIP)), each encoding one shared melanoma-associated antigen.

The novel RNA(LIP) formulation was engineered (i) to protect RNA from degradation by plasma RNases and (ii) to enable directed in vivo targeting of APCs in lymphoid compartments, thus (iii) allowing for intravenous administration of multiple RNA products advancing from local to systemic targeting of APCs. Here, RNA(LIP) products trigger a Toll-like receptor (TLR)-mediated Interferon-α (IFN-α) release from plasmacytoid dendritic cells (DCs) and macrophages stimulating DC maturation and hence inducing innate immune mechanisms as well as potent vaccine antigen-specific immune responses.

Notably, BioNTech RNA Pharmaceuticals′ RNA(LIP) formulation is a universally applicable potent novel vaccine class for intravenous APC targeting and the induction of potent synchronized adaptive and type-I interferon-mediated innate immune responses for cancer immunotherapy. Similar to other liposomal drugs, the ready-to-use RNA(LIP) products are prepared individually in a straight-forward manner directly prior to use from three components, namely solutions containing RNA drug product, NaCl diluent, and liposome excipient, that are provided as a kit.

A multi-center phase I/II trial to clinically validate this pioneering RNA(LIP) formulation for the treatment of malignant melanoma was initiated in 2015 (NCT02410733). The objective of the clinical trial is to study the feasibility, safety, tolerability, immunogenicity and evaluate potential clinical activity of the RNA(LIP) immunotherapy concept.

Detailed information on the ongoing trial, the recruitment and treatment status as well as data on the assessment of vaccine-induced immune responses will be presented.

Citation Format: Robert A. Jabulowsky, Carmen Loquai, Mustafa Diken, Lena M. Kranz, Heinrich Haas, Sebastian Attig, Nicole Bidmon, Janina Buck, Evelyna Derhovanessian, Jan Diekmann, Daniel Fritz, Veronika Jahndel, Alexandra Kemmer-Brueck, Klaus Kuehlcke, Andreas N. Kuhn, Peter Langguth, Ulrich Luxemburger, Martin Meng, Felicitas Mueller, Richard Rae, Fatih Sari, Doreen Schwarck-Kokarakis, Christine Seck, Kristina Spieß, Meike Witt, Jessica C. Hassel, Jochen Utikal, Roland Kaufmann, Sebastian Kreiter, Christoph Huber, Oezlem Tuereci, Ugur Sahin. A first-in-human phase I/II clinical trial assessing novel mRNA-lipoplex nanoparticles for potent cancer immunotherapy in patients with malignant melanoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT032.

Systemic RNA delivery to dendritic cells exploits antiviral defence for cancer immunotherapy

Lymphoid organs, in which antigen presenting cells (APCs) are in close proximity to T cells, are the ideal microenvironment for efficient priming and amplification of T-cell responses. However, the systemic delivery of vaccine antigens into dendritic cells (DCs) is hampered by various technical challenges. Here we show that DCs can be targeted precisely and effectively in vivo using intravenously administered RNA-lipoplexes (RNA-LPX) based on well-known lipid carriers by optimally adjusting net charge, without the need for functionalization of particles with molecular ligands. The LPX protects RNA from extracellular ribonucleases and mediates its efficient uptake and expression of the encoded antigen by DC populations and macrophages in various lymphoid compartments. RNA-LPX triggers interferon-α (IFNα) release by plasmacytoid DCs and macrophages. Consequently, DC maturation in situ and inflammatory immune mechanisms reminiscent of those in the early systemic phase of viral infection are activated. We show that RNA-LPX encoding viral or mutant neo-antigens or endogenous self-antigens induce strong effector and memory T-cell responses, and mediate potent IFNα-dependent rejection of progressive tumours. A phase I dose-escalation trial testing RNA-LPX that encode shared tumour antigens is ongoing. In the first three melanoma patients treated at a low-dose level, IFNα and strong antigen-specific T-cell responses were induced, supporting the identified mode of action and potency. As any polypeptide-based antigen can be encoded as RNA, RNA-LPX represent a universally applicable vaccine class for systemic DC targeting and synchronized induction of both highly potent adaptive as well as type-I-IFN-mediated innate immune mechanisms for cancer immunotherapy.

Abstract B041: A novel nanoparticular formulated tetravalent RNA cancer vaccine for treatment of patients with malignant melanoma

Immunotherapeutic approaches have evolved as promising and valid alternatives to available conventional cancer treatments. Amongst others, vaccination with tumor antigen-encoding RNAs by local administration is currently successfully employed in various clinical trials. To allow for a more efficient targeting of antigen-presenting cells (APCs) we have developed a novel RNA immunotherapeutic for systemic application based on a fixed set of four liposome complexed RNA drug products (RNA(LIP)) each encoding one shared melanoma-associated antigen.

Similar to other liposomal drugs, the four injectable RNA(LIP) products constituting the investigational medicinal product will be prepared individually in a straight-forward manner directly prior to use from three components, namely solutions containing RNA drug product, NaCl diluent, and liposome excipient, that are provided as a kit.

The novel lipoplex formulation was engineered (i) to protect RNA from degradation by plasma RNases and (ii) to enable directed in vivo targeting of APCs in lymphoid compartments, thus (iii) allowing for intravenous administration of multiple RNA products advancing from local to systemic targeting of APCs. The improved selective delivery of the RNA(LIP) products into APCs has further been shown to lead to an enhanced induction of vaccine-induced T-cell responses.

Extensive pharmacological characterization of the RNA(LIP) platform revealed that upon cellular uptake the encoded antigens will be translated into proteins that will be rapidly processed into peptide fragments, which after presentation by MHC class I and II molecules on the surface of APCs induce tumor antigen-specific CD8+ and CD4+ T-cell responses that spread systemically. These vaccine-induced T cells have been shown to specifically recognize and kill antigen-positive tumor cells eliciting potent anti-tumoral activity in vivo. The potent vaccination effects are additionally enhanced by further immunomodulatory effects based on the transient release of pro-inflammatory cytokines such as IFN-α, IP-10, and IL-6 due to binding of the administered RNA drug products to Toll-like receptors (TLRs).

The clinical translation of this pioneering therapeutic concept is currently being realized in a multi-center, first-in-human phase I trial in patients with malignant melanoma. Main objectives of the clinical trial are to study safety, tolerability, and immunogenicity of this innovative immunotherapy approach.

The novel lipoplex formulation, RNA(LIP) mechanism of action, study design and clinical workflow, as well as recruitment and treatment status of the ongoing clinical trial will be presented.

Citation Format: Robert A. Jabulowsky, Carmen Loquai, Mustafa Diken, Lena M. Kranz, Heinrich Haas, Sebastian Attig, Cedrik M. Britten, Janina Buck, Evelyna Derhovanessian, Jan Diekmann, Isaac Esparza, Daniel Fritz, Yves Huesemann, Veronika Jahndel, Klaus Kuehlcke, Andreas N. Kuhn, Peter Langguth, Ulrich Luxemburger, Martin Meng, Felicitas Mueller, Kerstin C. Reuter, Doreen Schwarck, Kristina Spiess, Meike Witt, Jessica C. Hassel, Jochen Utikal, Roland Kaufmann, Marc Schrott, Sebastian Kreiter, Oezlem Tuereci, Christoph Huber, Ugur Sahin. A novel nanoparticular formulated tetravalent RNA cancer vaccine for treatment of patients with malignant melanoma. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B041.