Targeting of IL-2 to cytotoxic lymphocytes as an improved method of cytokine-driven immunotherapy

MB2033, an anti-PD-L1 × IL-2 variant fusion protein, demonstrates robust anti-tumor efficacy with minimal peripheral toxicity

Interleukin-2 (IL-2), a cytokine with pleiotropic immune effects, was the first approved cancer immunotherapy agent. However, IL-2 is associated with systemic toxicity due to binding with its ligand IL-2Rα, such as vascular leakage syndrome, limiting its clinical applications. Despite efforts to extend the half-life of IL-2 and abolish IL-2Rα interactions, the risk of toxicity remains unresolved. In this study, we developed the bispecific fusion protein MB2033, comprising a novel IL-2 variant (IL-2v) connected to anti-programmed death ligand 1 (PD-L1) via a silenced Fc domain. The IL-2v of MB2033 exhibits attenuated affinity for IL-2Rβγ without binding to IL-2Rα. The binding affinity of MB2033 for PD-L1 is greater than that for IL-2Rβγ, indicating its preferential targeting of PD-L1+ tumor cells to induce tumor-specific immune activation. Accordingly, MB2033 exhibited significantly reduced regulatory T cell activation, while inducing comparable CD8+ T cell activation to recombinant human IL-2 (rhIL-2). MB2033 induced lower immune cell expansion and reduced cytokine levels compared with rhIL-2 in human peripheral blood mononuclear cells, indicating a decreased risk of peripheral toxicity. MB2033 exhibited superior anti-tumor efficacy, including tumor growth inhibition and complete responses, compared with avelumab monotherapy in an MC38 syngeneic mouse model. In normal mice, MB2033 was safer than non-α IL-2v and tolerable up to 30 mg/kg. These preclinical results provide evidence of the dual advantages of MB2033 with an enhanced safety and potent clinical efficacy for cancer treatment.

BRAIDing receptors for cell-specific targeting

Systemic toxicity is a major challenge in the development of therapeutics. Consequently, cell-type-specific targeting is needed to improve on-target efficacy while reducing off-target toxicity. Here, we describe a cell-targeting system we have termed BRAID (BRidged Activation by Intra/intermolecular Division) whereby an active molecule is divided into two inactive or less active parts that are subsequently brought together via a so-called 'bridging receptor' on the target cell. This concept was validated using the WNT/β-catenin signaling system, demonstrating that a multivalent WNT agonist molecule divided into two inactive components assembled from different epitopes via the hepatocyte receptor βKlotho induces signaling specifically on hepatocytes. These data provide proof of concept for this cell-specific targeting strategy, and in principle, this may also allow activation of multiple signaling pathways where desirable. This approach has broad application potential for other receptor systems.

A reengineered common chain cytokine augments CD8+ T cell–dependent immunotherapy

Cytokine therapy is limited by undesirable off-target side effects as well as terminal differentiation and exhaustion of chronically stimulated T cells. Here, we describe the signaling properties of a potentially unique cytokine by design, where T cell surface binding and signaling are separated between 2 different families of receptors. This fusion protein cytokine, called OMCPmutIL-2, bound with high affinity to the cytotoxic lymphocyte-defining immunoreceptor NKG2D but signaled through the common γ chain cytokine receptor. In addition to precise activation of cytotoxic T cells due to redirected binding, OMCPmutIL-2 resulted in superior activation of both human and murine CD8⁺ T cells by improving their survival and memory cell generation and decreasing exhaustion. This functional improvement was the direct result of altered signal transduction based on the reorganization of surface membrane lipid rafts that led to Janus kinase-3–mediated phosphorylation of the T cell receptor rather than STAT/AKT signaling intermediates. This potentially novel signaling pathway increased CD8⁺ T cell response to low-affinity antigens, activated nuclear factor of activated T cells transcription factors, and promoted mitochondrial biogenesis. OMCPmutIL-2 thus outperformed other common γ chain cytokines as a catalyst for in vitro CD8⁺ T cell expansion and in vivo CD8⁺ T cell–based immunotherapy.

Retargeting IL-2 Signaling to NKG2D-Expressing Tumor-Infiltrating Leukocytes Improves Adoptive Transfer Immunotherapy

Ex vivo expansion followed by reinfusion of tumor-infiltrating leukocytes (TILs) has been used successfully for the treatment of multiple malignancies. Most protocols rely on the use of the cytokine IL-2 to expand TILs prior to reinfusion. In addition, TIL administration relies on systemic administration of IL-2 after reinfusion to support transferred cell survival. The use of IL-2, however, can be problematic because of its preferential expansion of regulatory T and myeloid cells as well as its systemic side effects. In this study, we describe the use of a novel IL-2 mutant retargeted to NKG2D rather than the high-affinity IL-2R for TIL-mediated immunotherapy in a murine model of malignant melanoma. We demonstrate that the NKG2D-retargeted IL-2 (called OMCPmutIL-2) preferentially expands TIL-resident CTLs, such as CD8+ T cells, NK cells, and γδT cells, whereas wild-type IL-2 provides a growth advantage for CD4+Foxp3+ T cells as well as myeloid cells. OMCPmutIL-2-expanded CTLs express higher levels of tumor-homing receptors, such as LFA-1, CD49a, and CXCR3, which correlate with TIL localization to the tumor bed after i.v. injection. Consistent with this, OMCPmutIL-2-expanded TILs provided superior tumor control compared with those expanded in wild-type IL-2. Our data demonstrate that adoptive transfer immunotherapy can be improved by rational retargeting of cytokine signaling to NKG2D-expressing CTLs rather than indiscriminate expansion of all TILs.

Ramatroban as a Novel Immunotherapy for COVID-19

SARS-CoV-2 virus suppresses host innate and adaptive immune responses, thereby allowing the virus to proliferate, and cause multiorgan failure, especially in the elderly. Respiratory viruses stimulate cyclooxygenase-2 (COX-2) to generate prostanoids including Prostaglandin D2 (PGD2) and thromboxane A2. Furthermore, PGD2 concentrations in the airways increase with aging. PGD2 action mediated via DP2 receptors suppresses both innate and adaptive immune responses, by inhibiting interferon-λ and stimulation of myeloid monocyte-derived suppressor cells respectively. PGD2 and thromboxane A2 actions via the TP receptors activate platelets leading to a prothrombotic state. Ramatroban, a small-molecule antagonist of DP2 and TP receptors, reverses viremia-associated proinflammatory, immunosuppressive5 and prothrombotic processes which are similar to those induced by SARS-Cov-2. Ramatroban, used for the treatment of allergic rhinitis in Japan for the past 20 years has an excellent safety profile. Therefore, Ramatroban merits investigation as a novel immunotherapy for the treatment of COVID-19 disease.

Modifying the cancer-immune set point using vaccinia virus expressing re-designed interleukin-2

The complex immune tumour microenvironment requires an equally complex immunotherapy approach, especially when the cancer-immune set point is non-inflamed. Oncolytic viruses expressing immune activating cytokines might optimally modify the immune microenvironment and improve the antitumour effects. In this study, we have explored a variety of IL-2 constructs expressed by a tumour-selective oncolytic vaccinia virus, designed to maintain IL-2 in the tumour microenvironment to reduce systemic toxicity. An IL-2 construct combining a glycosylphosphatidylinositol (GPI) anchor with a rigid peptide linker leads to functional IL-2 expression on the tumour cell surface and in the tumour microenvironment. This virus construct effectively modifies the cancer-immune set point and treats a variety of murine tumour models with no toxic side effects. In combination with PD-1/PD-L1 blockade this virus cures most of the mice with a high tumour burden. This combination represents a treatment for cancers which are to date unresponsive to immunotherapy.

IL-2 is used systemically for cancer therapy but it is associated with severe toxicity. Here, the authors design a recombinant vaccinia virus expressing membrane-bound IL-2 that shows therapeutic efficacy alone or in combination with checkpoint inhibitors in colon cancer-bearing mice.