IL-2 is inactivated by the acidic pH environment of tumors enabling engineering of a pH-selective mutein

Abstract

Cytokines interact with their receptors in the extracellular space to control immune responses. How the physicochemical properties of the extracellular space influence cytokine signaling is incompletely elucidated. Here, we show that the activity of interleukin-2 (IL-2), a cytokine critical to T cell immunity, is profoundly affected by pH, limiting IL-2 signaling within the acidic environment of tumors. Generation of lactic acid by tumors limits STAT5 activation, effector differentiation, and antitumor immunity by CD8 + T cells and renders high-dose IL-2 therapy poorly effective. Directed evolution enabled selection of a pH-selective IL-2 mutein (Switch-2). Switch-2 binds the IL-2 receptor subunit IL-2Rα with higher affinity, triggers STAT5 activation, and drives CD8 + T cell effector function more potently at acidic pH than at neutral pH. Consequently, high-dose Switch-2 therapy induces potent immune activation and tumor rejection with reduced on-target toxicity in normal tissues. Last, we show that sensitivity to pH is a generalizable property of a diverse range of cytokines with broad relevance to immunity and immunotherapy in healthy and diseased tissues.

Tumour-infiltrating lymphocytes: from prognosis to treatment selection

“…The importance of the TME on TIL dynamics is further proven by the effect of hypoxia and acidity on TIL effector functions and proliferation. It has been suggested that an acidic environment prevents lymphocyte proliferation by impairing the stimulatory activity of IL-2 [76,116,117]. Furthermore, acidosis in the TME impairs the cytolytic activity and cytokine secretion of CD8 + T lymphocytes [76,118].…”

TCR-engineered T cell therapy in solid tumors: State of the art and perspectives

“…Last, gene modifications developed for CAR-T cell therapies to overcome tumor-related immunosuppression could also be used for TCR-T cells, such as PD-1 disruption, PD-1–CD28 chimeric constructs, or dominant negative transforming growth factor–β receptor type 2 ( 116 ). In addition to synthetic biology, combination with approaches targeting the tumor microenvironment ( 7 , 8 ) or modified cytokines resistant to hypoxic and acidic conditions prevalent in tumors may improve the efficiency of adoptive T cell therapies ( 117 ).…”

Spatiotemporally programming cytokine immunotherapies through protein engineering

“…Leveraging differential pH levels within the TME for conditional activation has also been explored. Gaggero et al recently demonstrated the pH sensitivity of the wild‐type IL‐2/IL‐2Rɑ interaction 93 . At acidic pH (6.5, commensurate with tumor levels), IL‐2 is shown to be a much weaker agonist of activated CD8 T cells because of minimized IL‐2Rɑ binding (IL‐2RβƔ was unchanged) 93 .…”

“…Using yeast surface display and directed evolution, the authors identify Switch‐2, an IL‐2 mutein with 5 amino acid mutations capable of binding IL‐2Rɑ at low pH. Switch‐2 is shown to improve responses in a variety of tumor models over extended half‐life Fc/IL‐2 93 . The pH dependency of the high affinity IL‐2Rɑ interaction has interesting applications for IL‐2 therapies, since it implies that wild‐type IL‐2/lymphocyte interactions in the tumor are naturally not‐alpha.…”

“…Gaggero et al recently demonstrated the pH sensitivity of the wild-type IL-2/IL-2Rɑ interaction. 93 At acidic pH (6.5, commensurate with tumor levels), IL-2 is shown to be a much weaker agonist of activated CD8 T cells because of minimized IL-2Rɑ binding (IL-2RβƔ was unchanged). 93 The authors hypothesized that an IL-2 mutein capable of effectively signaling through IL-2Rɑ at acidic pH would elicit improved anti-tumor re- this redox-sensitive "masking" in the non-ACT context through the development of "switchable" immune modulators (Sw-IM).…”