Antibody fusions with immunomodulatory proteins for cancer therapy

A novel strategy to generate immunocytokines with activity-on-demand using small molecule inhibitors

Cytokine-based therapeutics have been shown to mediate objective responses in certain tumor entities but suffer from insufficient selectivity, causing limiting toxicity which prevents dose escalation to therapeutically active regimens. The antibody-based delivery of cytokines significantly increases the therapeutic index of the corresponding payload but still suffers from side effects associated with peak concentrations of the product in blood upon intravenous administration. Here we devise a general strategy (named "Intra-Cork") to mask systemic cytokine activity without impacting anti-cancer efficacy. Our technology features the use of antibody-cytokine fusions, capable of selective localization at the neoplastic site, in combination with pathway-selective inhibitors of the cytokine signaling, which rapidly clear from the body. This strategy, exemplified with a tumor-targeted IL12 in combination with a JAK2 inhibitor, allowed to abrogate cytokine-driven toxicity without affecting therapeutic activity in a preclinical model of cancer. This approach is readily applicable in clinical practice.

An antibody-based enzymatic therapy for cancer treatment: The selective localization of D-amino acid oxidase to EDA fibronectin

In order to generate an antibody directed enzyme prodrug therapy, here we designed a chimeric protein by fusing the F8 antibody that recognizes the EDA of fibronectin (expressed on the tumor neovasculature) and an evolved variant of the ROS-generating enzyme D-amino acid oxidase (DAAO). The F8(scFv)-DAAO-Q144R recombinant protein is expressed by both CHO-S and E. coli cells. The F8(scFv)-DAAO-Q144R from E. coli cells is fully soluble, shows a high specific activity, is more thermostable in blood than the native DAAO, possesses a binding affinity for EDA well suited for efficient tumor accumulation, and localizes in tumor tissues. Notably, the F8(scFv)-DAAO-Q144R conjugate generates a stronger cytotoxicity to tumor cells than the native enzyme, especially when an inhibitor of heme oxygenase-1 (HO-1) is used, making it a promising candidate for a selective antitumor oxidative therapy controlled by the substrate addition, in the so called "activity on demand", thus sparing normal tissue from damage.

Cytokine engineering for targeted cancer immunotherapy

Cytokines are key modulators of the immune responses and represent promising therapeutics for a variety of cancers. However, successful translation of cytokine-based therapy to the clinic is limited by, among others, severe toxicities and lack of efficacy due to cytokine pleiotropy and off-target activation of cells. Engineering cytokines with enhanced therapeutic properties has emerged as a promising strategy to overcome these challenges. Advances in protein engineering and protein-polymer conjugate technologies have fostered the generation of cytokines with enhanced target cell specificity and longer half-life than the native ones. These novel cytokines exhibit reduced systemic toxicities while focusing the activities at the tumor site, thus, enhancing antitumor immunity. The growing toolbox of cytokine engineering strategies will further stimulate the development of smart cytokine-based immunotherapies with enhanced efficacy and safety profiles.

Antibody-Cytokine Fusions: Versatile Products for the Modulation of Anticancer Immunity

The remarkable clinical success of immune-checkpoint inhibitors for the treatment of a growing number of cancer types has sparked interest in the discovery of novel forms of immunotherapy, which may be used alone or in combination. In this context, cytokine-based therapeutics are well poised to play a role in modern cancer therapy. This article focuses on antibody-cytokine fusion proteins (also called "immunocytokines") as one class of biopharmaceuticals that can substantially improve the therapeutic index and, thus, the applicability of cytokine products. In many preclinical settings, antibodies can be used to preferentially deliver many (but not all) types of cytokines to primary and metastatic tumor lesions. The antibody-based delivery of certain proinflammatory payloads (such as IL2, IL12, and TNF) to the tumor microenvironment can lead to a dramatic potentiation of their anticancer activity. However, although some fusion proteins have advanced to late-stage clinical trials, much work remains to be done in order to fully characterize the mechanism of action and the pharmaceutical potential of immunocytokines in the clinical setting. Various factors contribute to in vivo performance, including the target antigen, the antibody properties, the nature of the payload, the format of the fusion protein, the dose, and schedule, as well as their use in combination with other therapeutic modalities. Protein engineering opportunities and insights in cancer immunology are contributing to the development of next-generation immunocytokine products and of novel therapeutic concepts, with the goal to increase antitumor activity and reduce systemic toxicity (a common problem for cytokine-based biopharmaceuticals).

Considerations for the Design of Antibody-Based Therapeutics

Antibody-based proteins have become an important class of biologic therapeutics, due in large part to the stability, specificity, and adaptability of the antibody framework. Indeed, antibodies not only have the inherent ability to bind both antigens and endogenous immune receptors but also have proven extremely amenable to protein engineering. Thus, several derivatives of the monoclonal antibody format, including bispecific antibodies, antibody-drug conjugates, and antibody fragments, have demonstrated efficacy for treating human disease, particularly in the fields of immunology and oncology. Reviewed here are considerations for the design of antibody-based therapeutics, including immunological context, therapeutic mechanisms, and engineering strategies. First, characteristics of antibodies are introduced, with emphasis on structural domains, functionally important receptors, isotypic and allotypic differences, and modifications such as glycosylation. Then, aspects of therapeutic antibody design are discussed, including identification of antigen-specific variable regions, choice of expression system, use of multispecific formats, and design of antibody derivatives based on fragmentation, oligomerization, or conjugation to other functional moieties. Finally, strategies to enhance antibody function through protein engineering are reviewed while highlighting the impact of fundamental biophysical properties on protein developability.

Finding the perfect match between nanoparticles and microfluidics to respond to cancer challenges

The clinical translation of new cancer theranostic has been delayed by inherent cancer's heterogeneity. Additionally, this delay has been enhanced by the lack of an appropriate in vitro model, capable to produce accurate data. Nanoparticles and microfluidic devices have been used to obtain new and more efficient strategies to tackle cancer challenges. On one hand, nanoparticles-based therapeutics can be modified to target specific cells, and/or molecules, and/or modified with drugs, releasing them over time. On the other hand, microfluidic devices allow the exhibition of physiologically complex systems, incorporation of controlled flow, and control of the chemical environment. Herein, we review the use of nanoparticles and microfluidic devices to address different cancer challenges, such as detection of CTCs and biomarkers, point-of-care devices for early diagnosis and improvement of therapies. The future perspectives of cancer challenges are also addressed herein.

Duokines: a novel class of dual-acting co-stimulatory molecules acting in cis or trans

Co-stimulatory signals induced by ligands of the tumor necrosis factor superfamily (TNFSF) play a central role in T cell activation and have emerged as a promising strategy in cancer immunotherapy. Here, we established a novel class of bifunctional co-stimulatory fusion proteins with the aim to boost T cell activation at the level of T cell – antigen-presenting cell (APC) interaction. These novel dual-acting cytokine fusion proteins were created by connecting two different homotrimeric TNFSF ligands to form homotrimeric bifunctional molecules (Duokines) or by connecting single-chain derivatives of two different homotrimeric TNFSF with a single, flexible linker (single-chain Duokines, scDuokines). By linking the TNFSF ligands 4-1BBL, OX40L and CD27L in all possible combinations, cis-acting Duokines were generated that act on the same or adjacent T cells, while combining CD40L with 4-1BBL, OX40L and CD27L resulted in trans-acting Duokines acting simultaneously on APCs and T cells. In vitro, co-stimulation of T cells was seen for cis- and trans-acting Duokines and scDuokines in an antigen-independent as well as antigen-specific setting. Trans-acting molecules furthermore activated B cells, which represent a subclass of APCs. In a pilot experiment using the syngeneic B16-FAP mouse tumor model scDuokines displayed antitumoral activity in vivo in combination with a primary T cell-activating bispecific antibody, evident from reduced number of lung metastasis compared to the antibody-only treated group. Our data show that the bifunctional, co-stimulatory duokines are capable to enhance T cell-mediated anti-tumor immune responses, suggesting that they can serve as a new class of immuno-stimulatory molecules for use in cancer immunotherapy strategies.

Potentiation of PD-L1 blockade with a potency-matched dual cytokine-antibody fusion protein leads to cancer eradication in BALB/c-derived tumors but not in other mouse strains

We have recently described a novel therapeutic antibody product (IL2-F8-TNF^mut), featuring the simultaneous fusion of murine IL2 and of a TNF mutant with scFv(F8), an antibody specific to the alternatively-spliced extra domain A of fibronectin (EDA). Here, we report on the in vivo characterization of the anti-cancer activity of IL2-F8-TNF^mut in four immunocompetent murine models of cancer, CT26, WEHI-164, F9 teratocarcinoma and Lewis lung carcinoma (LLC), using the product alone or in combination with a monoclonal antibody specific to murine PD-L1. All four models exhibited a strong expression of EDA-fibronectin, which was confined to vascular structures for F9 tumors, while the other three malignancies exhibited a more stromal pattern of staining. A complete and long-lasting tumor eradication of CT26 and WEHI-164 tumors was observed in BALB/c mice when IL2-F8-TNF^mut was used in combination with PD-L1 blockade. The combination treatment led to improved tumor growth inhibition in 129/SvEv mice bearing murine teratocarcinoma or in C57BL/6 mice bearing murine LLC, but those cancer cures were difficult to achieve in those models. A microscopic analysis of tumor sections, obtained 24 h after pharmacological treatment, revealed that the PD-L1 antibody had homogenously reached tumor cells in vivo and that the combination of PD-L1 blockade with IL2-F8-TNF^mut stimulated an influx of NK cells and of T cells into the neoplastic mass. These data indicate that potency-matched dual-cytokine fusion proteins may be ideally suited to potentiate the therapeutic activity of immune check-point inhibitors.

Production, Purification, and Characterization of Antibody-TNF Superfamily Ligand Fusion Proteins

Antibody-fusion proteins with ligands, e.g., of the TNF superfamily (TNFSF) can be adequately produced in mammalian expression systems. Here, we describe the transient production in adherent and suspension human embryonic kidney cells at laboratory scale, followed by purification procedures applying protein A and immobilized metal affinity chromatography for proteins with Fc domain and 6 × histidine-tag, respectively. In addition, characterization of the purified proteins by size exclusion chromatography is described.

Evolution of the magic bullet: Single chain antibody fragments for the targeted delivery of immunomodulatory proteins

Immunocytokines are fusion proteins that combine the specific antigen binding capacities of an antibody or derivative thereof and the potent bioactivity of a cytokine partner. These novel biopharmaceuticals have been directed to various targets of oncological as well as non-oncological origin and a handful of promising constructs are currently advancing in the clinical trial pipeline. Several factors such as the choice of a disease specific antigen, the antibody format and the modulatory nature of the payload are crucial, not only for therapeutic efficacy and safety but also for the commercial success of such a product. In this review, we provide an overview of the basic principles and obstacles in immunocytokine design with a specific focus on single chain antibody fragment-based constructs that employ interleukins as the immunoactive component. Impact statement Selective activation of the immune system in a variety of malignancies represents an attractive approach when existing strategies have failed to provide adequate treatment options. Immunocytokines as a novel class of bifunctional protein therapeutics have emerged recently and generated promising results in preclinical and clinical studies. In order to harness their full potential, multiple different aspects have to be taken into consideration. Several key points of these fusion constructs are discussed here and should provide an outline for the development of novel products based on an overview of selected formats.

Potency-matched Dual Cytokine-Antibody Fusion Proteins for Cancer Therapy

A novel biopharmaceutical, consisting of the F8 mAb (specific to a splice isoform of fibronectin) simultaneously fused to both TNF and IL2, was found to react with the majority of solid tumors and hematologic malignancies in mouse and man, but not with healthy adult tissues. The product selectively localized to neoplastic lesions in vivo, as evidenced by quantitative biodistribution studies using radioiodinated protein preparations. When the potency of the cytokine payloads was matched by a single-point mutation, the resulting fusion protein (IL2-F8-TNFmut) eradicated soft-tissue sarcomas in immunocompetent mice, which did not respond to individual antibody-cytokine fusion proteins or by standard doxorubicin treatment. Durable complete responses were also observed in mice bearing CT26, C1498, and F9 tumors. The simultaneous delivery of multiple proinflammatory payloads to the cancer site conferred protective immunity against subsequent tumor challenges. A fully human homolog of IL2-F8-TNFmut, which retained selectivity similar to its murine counterpart when tested on human material, may open new clinical applications for the immunotherapy of cancer. Mol Cancer Ther; 16(11); 2442-51. ©2017 AACR.

Tumor-targeted costimulation with antibody-fusion proteins improves bispecific antibody-mediated immune response in presence of immunosuppressive factors

Therapeutic strategies aiming for the induction of an effective immune response at the tumor site can be severely hampered by the encounter of an immunosuppressive microenvironment. We investigated here the potential of concerted costimulation by tumor-directed antibody-fusion proteins with B7.1, 4-1BBL and OX40L to enforce bispecific antibody-induced T cell stimulation in presence of recognized immunosuppressive factors including IL-10, TGF-β, indoleamine 2,3-dioxygenase (IDO), PD-L1 and regulatory T cells. The expression and activity of these factors was demonstrated in the HT1080-FAP/PBMC co-culture setting, where individual and combined costimulation were still capable to enhance T cell stimulation, even though the general activation level was reduced. Additional blockade of TGF-ß or PD-1 resulted especially effective in further enhancing the degree of T cell activation. Here, best outcome was achieved by combined costimulation of targeted 4-1BBL and B7.1. Furthermore, their individual impact on the proliferation of naïve, memory and effector CD8⁺ and CD4⁺ T cell subsets, suggest the coverage of a comprehensive T cell response. Thus, our costimulatory antibody-fusion proteins show great potential to support T cell activation in adverse conditions dictated by the tumor microenvironment.

Addressing the Immunogenicity of the Cargo and of the Targeting Antibodies with a Focus on Demmunized Bacterial Toxins and on Antibody-Targeted Human Effector Proteins

Third-generation immunotoxins are composed of a human, or humanized, targeting moiety, usually a monoclonal antibody or an antibody fragment, and a non-human effector molecule. Due to the non-human origin of the cytotoxic domain, these molecules stimulate potent anti-drug immune responses, which limit treatment options. Efforts are made to deimmunize such immunotoxins or to combine treatment with immunosuppression. An alternative approach is using the so-called “human cytotoxic fusion proteins”, in which antibodies are used to target human effector proteins. Here, we present three relevant approaches for reducing the immunogenicity of antibody-targeted protein therapeutics: (1) reducing the immunogenicity of the bacterial toxin, (2) fusing human cytokines to antibodies to generate immunocytokines and (3) addressing the immunogenicity of the targeting antibodies.

Synergistic effect of programmed cell death protein 1 blockade and secondary lymphoid tissue chemokine in the induction of anti-tumor immunity by a therapeutic cancer vaccine

The use of DNA vaccines has become an attractive approach for generating antigen-specific cytotoxic CD8⁺ T lymphocytes (CTLs), which can mediate protective antitumor immunity. The potency of DNA vaccines encoding weakly immunogenic tumor-associated antigens (TAAs) can be improved by using an adjuvant injected together with checkpoint antibodies. In the current study, we evaluated whether the therapeutic effects of a DNA vaccine encoding human papilloma virus type 16 (HPV-16) E7 can be enhanced by combined application of an immune checkpoint blockade directed against the programmed death-1 (PD-1) pathway and secondary lymphoid tissue chemokine (SLC) also known as CCL21 adjuvant, in a mouse cervical cancer model. The therapeutic effects of the DNA vaccine in combination with CCL21 adjuvant plus PD-1 blockade was evaluated using a tumor growth curve. To further investigate the mechanism underlying the antitumor response, cytolytic and lymphocyte proliferation responses in splenocytes were measured using non-radioactive cytotoxicity and MTT assays, respectively. Vascular endothelial growth factor (VEGF) and IL-10 expression in the tumor and the levels of IFN-γ and IL-4 in supernatants of spleno-lymphocyte cultures were measured using ELISA. The immune efficacy was evaluated by in vivo tumor regression assay. The results showed that vaccination with a DNA vaccine in combination with the CCL21 adjuvant plus PD-1 blockade greatly enhanced cytotoxic T lymphocyte production and lymphocyte proliferation rates and greatly inhibited tumor progression. Moreover, the vaccine in combination with adjuvant and blockade significantly reduced intratumoral VEGF, IL-10 and splenic IL-4 but induced the expression of splenic IFN-γ. This formulation could be an effective candidate for a vaccine against cervical cancers and merits further investigation.

Advancing targeted co-stimulation with antibody-fusion proteins by introducing TNF superfamily members in a single-chain format

Co-stimulation via receptors of the tumor necrosis factor superfamily (TNFSF) emerges as promising strategy to support antitumor immune responses. Targeted strategies with antibody-fusion proteins composed of a tumor-directed antibody part and the extracellular domain of a co-stimulatory ligand of the TNFSF constitute an attractive option to focus the co-stimulatory activity to the tumor site. Since TNFSF members intrinsically form functional units of non-covalently linked homotrimers, the protein engineering of suitable antibody-fusion proteins is challenging. Aiming for molecules of simple and stable configuration, we used TNFSF ligands in a single-chain format (scTNFSF), i.e., three units of the ectodomain connected by polypeptide linkers, folding into an intramolecular trimer. By fusing tumor-directed scFv antibody fragments directed against EpCAM or FAP to co-stimulatory scTNFSF molecules (sc4-1BBL, scOX40L, scGITRL or scLIGHT), a set of monomeric scFv-scTNFSF fusion proteins was generated. In comparison to the scFv-TNFSF format, defined by intermolecular homotrimerization via the TNFSF part, scFv-scTNFSF showed equal or enhanced co-stimulatory activity despite reduced avidity in antibody binding. In addition, enhanced serum stability and improved bioavailability in mice were observed. We show that the scFv-scTNFSF format can be applied to various members of the TNFSF, presenting targeting-dependent co-stimulatory activity. Hence, this format exhibits favorable properties that make it a promising choice for further therapeutic fusion protein development.

Immunocytokines for cancer treatment: past, present and future

Immunocytokines are antibody-cytokine fusion proteins, with the potential to preferentially localize on tumor lesions and to activate anticancer immunity at the site of disease. Various tumor targets (e.g., cell membrane antigens and extracellular matrix components) and antibody formats (e.g., intact IgG and antibody fragments) have been considered for immunocytokine development and some products have advanced to clinical trials. In this review, we present relevant concepts and strategies for the design and use of anticancer immunocytokine products. In addition, we discuss emerging strategies for the pharmaceutical development and clinical application of this promising class of biopharmaceuticals.