511 A NKG2A antibody-IL-2 mutant fusion protein for cancer immunotherapy

Background

Nature Killer cells play a pivotal role in cancer immunosurveillance. The inhibitory receptor NKG2A modulates the function of NK cells as well as CD8 T cells by recognizing the non-classical MHC molecule - HLA-E which is expressed at high level in certain tumor types such as H&N cancer. NKG2A blockade has been proposed as a new immunotherapy complementary to PD-1 blockade. However, as a standalone therapy, inhibition of NKG2A and HLA-E is hardly effective both in mouse tumor models and in clinical trials. Since cytokine stimulated NK cells have been shown to possess improved persistence, expansion, metabolic function, and activity against tumor cells both in vitro and in vivo in multiple solid and haematological cancer models, a NKG2A antibody conjugated IL-2 mutant was created, aiming to deliver avidity-driven IL2 receptor stimulation to NKG2A+ immune cells for cancer immunotherapy.

Methods

An IL-2 variant was engineered to eliminate binding to IL2Rα (CD25) and to have attenuated affinity for IL2Rβγ (CD122/CD132). This detuned cytokine was fused to a high-affinity blocking antibody targeting NKG2A to generate a fusion molecule called ES015-IL2v. The ability of ES015-IL2v to activate IL-2-like signaling specifically to NKG2A-expressing cells was evaluated in vitro using human lymphocytes by measuring pSTAT5 signaling. The in vitro NKG2A-dependent proliferation assay was also evaluated with NK92 cells. The antitumor efficacy was evaluated in multiple animal models with surrogate ES015-IL2m antibodies.

Results

SPR analysis show that ES015-IL2v binds to IL2Rβγ with attenuated affinity and has no binding to IL2Rα. ES015-IL2v only induces IL-2 receptor signaling in NKG2A positive NK, NKT and CD8 T cells but has no effect on Treg cells. Indeed, ES015-IL2v induces dose – dependent NK cell expansion. Mouse surrogate ES015-IL2m antibody enhances the intra-tumoral NKG2A+ NK and CD8 T cell proliferation/activation and has superior control of malignancies in vivo.

Conclusions

In summary, ES015-IL2v is a highly potent anti-tumor agent, and our in vitro and in vivo data support its further development into next stage.