TCB2, a new anti-human interleukin-2 antibody, facilitates heterodimeric IL-2 receptor signaling and improves anti-tumor immunity

rhIL-7-hyFc and hIL-2/TCB2c combination promotes an immune-stimulatory tumor microenvironment that improves antitumor efficacy of checkpoint inhibitors

BACKGROUND

Recombinant human interleukin (rhIL)-7-hyFc (efineptakin alfa; NT-I7) is a potent T-cell amplifier, with two IL-7 molecules fused to IgD/IgG4 elements. rhIL-7-hyFc promotes extensive infiltration of CD8+ T cells into the tumor, concurrently increasing the numbers of intratumoral PD-1+CD8+ T cells. The hIL-2/TCB2 complex (SLC-3010) inhibits tumor growth by preferential activation of CD122 (IL-2Rβ)high CD8+ T cells and natural killer cells, over regulatory T cells (Tregs). We investigated the underlying mechanisms of rhIL-7-hyFc and hIL-2/TCB2c antitumor activity and the potential synergistic efficacy, specifically focusing on tumor-specific CD8+ cells within the tumor and the tumor-draining lymph nodes (tdLN).

METHODS

MC38 and CT26 tumor-bearing mice were administered with 10 mg/kg rhIL-7-hyFc intramuscularly and 0.9 mg/kg hIL-2/TCB2c intravenously. Anti-PD-1 monoclonal antibody was administered intraperitoneally three times at 3-day intervals at a dose of 5 mg/kg. Tumor volume was measured to assess efficacy. To compare the composition of immune cells between each monotherapy and the combination therapy, we analyzed tumors and tdLNs by flow cytometry.

RESULTS

Our data demonstrate that the combination of rhIL-7-hyFc and hIL-2/TCB2c increases efficacy and generates an immune-stimulatory tumor microenvironment (TME). The TME is characterized by an increased infiltration of tumor-specific CD8+ T cells, and a decreased frequency of CD39highTIM-3+ Treg cells. Most importantly, rhIL-7-hyFc increases infiltration of a CD62L+Ly108+ early progenitor population of exhausted CD8+ T cells (TPEX), which may retain long-term proliferation capacity and replenish functional effector CD8+ T cells. hIL-2/TCB2c induces differentiation of CD62L+Ly108+ TPEX rapidly into CD101+ terminally differentiated subsets (terminally exhausted T cell (TEX term)). Our study also demonstrates that rhIL-7-hyFc significantly enhances the proliferation rate of TPEX in the tdLNs, positively correlating with their abundance within the tumor. Moreover, rhIL-7-hyFc and hIL-2/TCB2c can overcome the limited therapeutic effectiveness of PD-1 blockade, culminating in the complete regression of tumors.

CONCLUSIONS

rhIL-7-hyFc can expand and maintain the progenitor pool of exhausted CD8+ T cells, whereas hIL-2/TCB2c promotes their differentiation into TEX term. Together, this induces an immune-stimulatory TME that improves the efficacy of checkpoint blockade.

Optimising IL-2 for Cancer Immunotherapy

The key role of T cells in cancer immunotherapy is well established and is highlighted by the remarkable capacity of Ab-mediated checkpoint blockade to overcome T-cell exhaustion and amplify anti-tumor responses. However, total or partial tumor remission following checkpoint blockade is still limited to only a few types of tumors. Hence, concerted attempts are being made to devise new methods for improving tumor immunity. Currently, much attention is being focused on therapy with IL-2. This cytokine is a powerful growth factor for T cells and optimises their effector functions. When used at therapeutic doses for cancer treatment, however, IL-2 is highly toxic. Nevertheless, recent work has shown that modifying the structure or presentation of IL-2 can reduce toxicity and lead to effective anti-tumor responses in synergy with checkpoint blockade. Here, we review the complex interaction of IL-2 with T cells: first during normal homeostasis, then during responses to pathogens, and finally in anti-tumor responses.

Engineering Anticytokine Antibodies for Immune Modulation

The delicate balance of immune homeostasis is regulated by the interactions between cytokines and their cognate cell surface signaling receptors. There is intensive interest in harnessing cytokines as drugs for diseases such as cancer and autoimmune disorders. However, the multifarious and often contradictory activities of cytokines, coupled with their short serum half-lives, limit clinical performance and result in dangerous toxicities. There is thus growing emphasis on manipulating natural cytokines to enhance their selectivity, safety, and durability through various strategies. One strategy that has gained traction in recent years is the development of anticytokine Abs that not only extend the circulation half-life of cytokines but also specifically bias their immune activities through multilayered molecular mechanisms. Although Abs are notorious for their antagonistic activities, this review focuses on anticytokine Abs that selectively agonize the activity of the target protein. This approach has potential to help realize the clinical promise of cytokine-based therapies.

The T-Cell Growth Factor Interleukin-2, Which Is Occasionally Targeted by Autoantibodies, Qualifies as Drug for the Treatment of Allergy, Autoimmunity, and Cancer: Collegium Internationale Allergologicum (CIA) Update 2024

Interleukin(IL)-2 was originally characterized as an important T-cellular growth factor but later on, turned out to be a pivotal homeostatic factor for the establishment and maintenance of both natural(n)Treg and peripheral(p)Treg. In this review, it was aimed to connect the peculiar structural and functional aspects of IL-2 to the innovative advancements in tailoring its multifaceted functional behavior for targeting various IL-2 receptor types. The article includes detailed descriptions of modified versions of IL-2, obtained by either mutating or fusing IL-2 to heterologous molecules or by forming IL-2/(monoclonal) antibody complexes (IL-2C), and discusses their functional implications for addressing such heterologous pathological conditions in cancer, autoimmunity, and allergy. Additionally, this review sheds light on the underexplored contribution of autoantibodies to the endogenous regulation of IL-2 within the realms of both health and disease. The ongoing efforts to fine-tune IL-2 responses through antibody-dependent targeting or molecular engineering offer considerable translational potential for the future utility of this important cytokine.

An engineered immunocytokine with collagen affinity improves the tumor bioavailability, tolerability, and therapeutic efficacy of IL-2

The clinical utility of human interleukin-2 (hIL-2) is limited by its short serum half-life, preferential activation of regulatory T (TReg) over immune effector cells, and dose-limiting toxicities. We previously engineered F10 immunocytokine (IC), an intramolecularly assembled cytokine/antibody fusion protein that linked hIL-2 to an anti-IL-2 antibody (denoted F10) that extended IL-2 half-life and augmented the immune effector to TReg ratio. Here, we leveraged molecular engineering to improve the anti-tumor therapeutic efficacy and tolerability of F10 IC by developing an iteration, denoted F10 IC-CBD (collagen binding domain), designed for intratumoral administration and in situ retention based on collagen affinity. F10 IC-CBD retained IL-2 bioactivity exclusively in the tumor and eliminated IL-2-associated toxicities. Furthermore, F10 IC exhibited potent single-agent therapeutic efficacy and synergy with systemic immune checkpoint blockade and elicited an abscopal response in mouse tumors models. This engineered fusion protein presents a prototype for the design of intratumoral therapies.

Accurate profiling of full-length Fv in highly homologous antibody libraries using UMI tagged short reads

Deep parallel sequencing (NGS) is a viable tool for monitoring scFv and Fab library dynamics in many antibody engineering high-throughput screening efforts. Although very useful, the commonly used Illumina NGS platform cannot handle the entire sequence of scFv or Fab in a single read, usually focusing on specific CDRs or resorting to sequencing VH and VL variable domains separately, thus limiting its utility in comprehensive monitoring of selection dynamics. Here we present a simple and robust method for deep sequencing repertoires of full length scFv, Fab and Fv antibody sequences. This process utilizes standard molecular procedures and unique molecular identifiers (UMI) to pair separately sequenced VH and VL. We show that UMI assisted VH-VL matching allows for a comprehensive and highly accurate mapping of full length Fv clonal dynamics in large highly homologous antibody libraries, as well as identification of rare variants. In addition to its utility in synthetic antibody discovery processes, our method can be instrumental in generating large datasets for machine learning (ML) applications, which in the field of antibody engineering has been hampered by conspicuous paucity of large scale full length Fv data.

Engineered cytokine/antibody fusion proteins improve delivery of IL-2 to pro-inflammatory cells and promote antitumor activity

Progress in cytokine engineering is driving therapeutic translation by overcoming the inherent limitations of these proteins as drugs. The interleukin-2 (IL-2) cytokine harbors great promise as an immune stimulant for cancer treatment. However, the cytokine's concurrent activation of both pro-inflammatory immune effector cells and anti-inflammatory regulatory T cells, its toxicity at high doses, and its short serum half-life have limited clinical application. One promising approach to improve the selectivity, safety, and longevity of IL-2 is complexation with anti-IL-2 antibodies that bias the cytokine towards the activation of immune effector cells (i.e., effector T cells and natural killer cells). Although this strategy shows therapeutic potential in preclinical cancer models, clinical translation of a cytokine/antibody complex is complicated by challenges in formulating a multi-protein drug and concerns about complex stability. Here, we introduce a versatile approach to designing intramolecularly assembled single-agent fusion proteins (immunocytokines, ICs) comprising IL-2 and a biasing anti-IL-2 antibody that directs the cytokine's activities towards immune effector cells. We establish the optimal IC construction and further engineer the cytokine/antibody affinity to improve immune biasing function. We demonstrate that our IC preferentially activates and expands immune effector cells, leading to superior antitumor activity compared to natural IL-2 without inducing toxicities associated with IL-2 administration. Collectively, this work presents a roadmap for the design and translation of immunomodulatory cytokine/antibody fusion proteins.

Engineered human cytokine/antibody fusion proteins expand regulatory T cells and confer autoimmune disease protection

Low-dose human interleukin-2 (hIL-2) treatment is used clinically to treat autoimmune disorders due to the cytokine's preferential expansion of immunosuppressive regulatory T cells (Tregs). However, off-target immune cell activation and short serum half-life limit the clinical potential of IL-2 treatment. Recent work showed that complexes comprising hIL-2 and the anti-hIL-2 antibody F5111 overcome these limitations by preferentially stimulating Tregs over immune effector cells. Although promising, therapeutic translation of this approach is complicated by the need to optimize dosing ratios and by the instability of the cytokine/antibody complex. We leverage structural insights to engineer a single-chain hIL-2/F5111 antibody fusion protein, termed F5111 immunocytokine (IC), which potently and selectively activates and expands Tregs. F5111 IC confers protection in mouse models of colitis and checkpoint inhibitor-induced diabetes mellitus. These results provide a roadmap for IC design and establish a Treg-biased immunotherapy that could be clinically translated for autoimmune disease treatment.

Selective Expansion of Tregs Using the IL-2 Cytokine Antibody Complex Does Not Reverse Established Alopecia Areata in C3H/HeJ Mice

Alopecia areata (AA) is an autoimmune disease mediated by NKG2D-expressing cytotoxic T lymphocytes destroying hair follicles in the skin. It is one of the most common autoimmune diseases, but there is no effective treatment modality approved by the FDA. Regulatory T cells (Tregs) are crucial for suppressing autoreactive T cells, and in the skin, they promote hair growth by inducing anagen. Based on this, we tested the therapeutic potential of expanded Tregs in AA using the C3H/HeJ mouse model. In mice with AA, NKG2D-expressing CD8 T cells widely infiltrate both haired and hairless skin areas, which have tissue-resident memory T-cell phenotypes. Tregs in the skin express CD25, CTLA-4, GATA-3, and Jagged1 and efficiently proliferate with IL-2 cytokine antibody complex. However, expanding Tregs in the skin did not induce anagen in normal mice, indicating that they are necessary but not sufficient for anagen induction. Also, they fail to suppress autoreactive CD8 T cells in the skin to reverse established AA in C3H/HeJ mice. These results suggest that Treg expansion alone is not sufficient for AA treatment, and combined immunotherapy is required.

Immune checkpoint inhibitors for PD-1/PD-L1 axis in combination with other immunotherapies and targeted therapies for non-small cell lung cancer

It has been widely acknowledged that the use of immune checkpoint inhibitors (ICI) is an effective therapeutic treatment in many late-stage cancers. However, not all patients could benefit from ICI therapy. Several biomarkers, such as high expression of PD-L1, high mutational burden, and higher number of tumor infiltration lymphocytes have shown to predict clinical benefit from immune checkpoint therapies. One approach using ICI in combination with other immunotherapies and targeted therapies is now being investigated to enhance the efficacy of ICI alone. In this review, we summarized the use of other promising immunotherapies and targeted therapies in combination with ICI in treatment of lung cancers. The results from multiple animals and clinical trials were reviewed. We also briefly discussed the possible outlooks for future treatment.

Site-specific PEGylation of interleukin-2 enhances immunosuppression via the sustained activation of regulatory T cells

The preferential activation of regulatory T (T_reg) cells by interleukin-2 (IL-2), which selectively binds to the trimeric IL-2 receptor (IL-2R) on T_reg cells, makes this cytokine a promising therapeutic for the treatment of autoimmune diseases. However, IL-2 has a narrow therapeutic window and a short half-life. Here, we show that the pharmacokinetics and half-life of IL-2 can be substantially improved by orthogonally conjugating the cytokine to poly(ethylene glycol) (PEG) moieties via a copper-free click reaction through the incorporation of azide-bearing amino acids at defined sites. Subcutaneous injection of a PEGylated IL-2 that optimally induced sustained T_reg-cell activation and expansion over a wide range of doses through highly selective binding to trimeric IL-2R led to enhanced therapeutic efficacy in mouse models of lupus, collagen-induced arthritis and graft-versus-host disease without compromising the immune defences of the host against viral infection. Site-specific PEGylation could be used more generally to engineer cytokines with improved therapeutic performance for the treatment of autoimmune diseases.

Crystal structure of human interleukin-2 in complex with TCB2, a new antibody-drug candidate with antitumor activity

Immunotherapy via interleukin-2 (IL-2) mediated activation of anti-tumor immune response is a promising approach for cancer treatment. The multi-potent cytokine, IL-2 has a central role in immune cell activation and homeostasis. Since IL-2 preferentially activates immunosuppressive T regulatory cells by IL-2Rα dependent manner, blocking IL-2:IL-2Rα interaction is a key to amplify the IL-2 activity in effector T cells toward anti-tumor response. Anti-IL-2 monoclonal antibodies are good candidates to control the IL-2:IL-2Rα interaction. In a previous study, we developed a new IL-2Rα mimetic antibody, TCB2, and showed that the human IL-2(hIL-2):TCB2 complex can stimulate T effector cells specifically and elicit potent anti-cancer immunotherapeutic effect, especially when administered in combination with immune checkpoint inhibitors. To understand the molecular mechanism, we determined the crystal structure of TCB2-Fab in a complex with hIL-2 at 2.5 Å resolution. Our structural analysis reveals that TCB2 binds to the central area of the hIL-2Rα binding region on hIL-2, and binding angle and epitope are different from previously known hIL-2Rα mimicking antibody NARA1 which recognizes the top part of hIL-2. TCB2 binding to hIL-2 also induces an allosteric effect that increases the affinity for the hetero-dimeric hIL-2 receptor, IL-2R(β + γ), on effector T cells.

Autophagy in the cancer-immunity dialogue

Autophagy is quintessential for the maintenance of cellular homeostasis in all eukaryotic cells, explaining why both normal and malignant cells benefit from proficient autophagic responses. Moreover, autophagy is intimately involved in the immunological control of malignant transformation, tumor progression and response to therapy. However, the net effect of autophagy activation or inhibition on the natural growth or therapeutic response of tumors evolving in immunocompetent hosts exhibits a considerable degree of context dependency. Here, we discuss the complex cross-talk between autophagy and immuno-oncology as delineated by genetic and pharmacological approaches in mouse models of cancer.

Targeted Activation of T Cells with IL-2-Coupled Nanoparticles

Interleukin-2 (IL-2) is a T cell growth factor particularly required in regulatory T cell maintenance and memory T cell responses. High-dose IL-2 treatment was the first FDA-approved immunotherapy for cancer, while low-dose IL-2 administration has shown promise in allograft rejection and autoimmune and inflammatory diseases. However, its pleiotropic nature and the existence of IL-2 receptors with different binding affinity limit its therapeutic application. For an improved clinical applicability of the cytokine, a targeted receptor assignment must, therefore, be achieved. Nanoparticles allow controlling the location and dose of immunomodulating compounds and to specifically address specific receptors through targeted drug binding. In this review article we discuss the IL-2 biology and current clinical application with regard to nanoparticle-based IL-2-mediated manipulation of T cell responses in autoimmunity, chronic inflammation, and cancer.