Lucia Bonati, Leo Scheller, Stephen Buckley, Sailan Shui, Bruno Correia, Li Tang

Leveraging chemically-controlled protein switches for increased safety of cytokine-based cancer immunotherapeutics

Cytokines are key signal mediators of the immune system playing an essential role in the orchestration of immune responses. Despite their unique ability to modulate the immune system, the translation of cytokine-based therapies to the clinic has been greatly hindered by severe toxicities due to the pleiotropy and off-targeting effects of many cytokines.

Here, we present a general strategy that enables precise control over cytokine activity. We control their activity by selectively masking the receptor binding site with a fused chemically-responsive domain, which could be unmasked with a competing molecule (Venetoclax). To achieve this, Bcl-2 was fused to the cytokine and the BIM-BH3 interaction motif was transplanted to sites in close proximity to the cytokine’s receptor binding site. In absence of Venetoclax, Bcl-2 bound the cytokine with high affinity blocking the interaction site between the cytokine and its receptor. Upon addition of Venetoclax, the interaction between Bcl-2 and the BIM-BH3 motif was disrupted, so restoring the cytokine’s activity. We have developed switchable mutants for a range of different cytokines (IL-2, IL-10, and IL-15) used in cancer immunotherapy. Moreover, we showed that in presence of Venetoclax, their activities can be selectively and fully restored.  

Overall, this drug-responsive switch strategy may achieve spatiotemporal control of cytokine activities in vivo and thus improve the safety and clinical applicability of cytokine therapeutics.