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1080 Using site-specific chemical conjugation to generate superior half-life extended or PD-1-targeted formats of a potent IL-18 variant resistant to IL-18 binding protein
  1. Jean Carralot,
  2. Camille Delon,
  3. Rubén Alvarez Sanchez,
  4. Roy Meoded,
  5. Philipp Moosman,
  6. Kea Martin,
  7. Arnaud Goepfert,
  8. Andrew Chi,
  9. Vijaya Pattabiraman and
  10. Bertolt Kreft
  1. Bright Peak Therapeutics, Basel, Switzerland


Background Interleukin-18 (IL-18) is a pro-inflammatory cytokine able to trigger both innate as well as adaptive immune responses. IL-18 is a potent amplifier of IFNg signaling which induces pleiotropic Th1 responses, making it an attractive cytokine for cancer immunotherapy. However, the clinical efficacy of wild-type (wt) IL-18 was limited, potentially due to the upregulation IL-18 binding protein (IL-18BP). IL-18BP is a secreted IFNg-induced antagonist that binds IL-18 with high affinity, prevents its interaction with the IL-18 receptor, and neutralizes IL-18 activity. Hence, we aimed to generate a potent IL-18BP-resistant IL-18 ”payload” that can be turned into optimal therapeutic formats with superior pharmacologic properties or leverage synergistic mechanisms of action (MOA).

Methods By introducing of a minimal set of mutations we generated an optimized human IL-18 that, compared to wt-IL-18, shows enhanced potency and significant resistance to IL-18BP. We further engineered the enhanced IL-18 variant to create a versatile “payload” that can be chemically conjugated in a site-specific manner. Conjugation to polyethylene glycol (PEG) resulted in a half-life extended agent, while conjugation to an anti-PD-1 antibody yielded a PD1-IL18 immunocytokine (IC) allowing exploitation of synergistic MOAs. We then characterized the pharmacologic and anti-tumor properties of these two therapeutic formats in vitro and in vivo.

Results Compared to wt-IL-18, the conjugatable payload is 300-fold more potent and >600-fold less sensitive to IL-18BP inhibition. Conjugation to a 30 kDa PEG yields a molecule with significantly improved PK properties in mice that is able to strongly activate CD8+ T and NK cells and to potently trigger the release of pro-inflammatory cytokines. PEGylated IL-18 showed strong anti-tumor efficacy which was enhanced in combination with an anti-PD-1 antibody. For the PD1-IL18 IC, the basic properties of the anti-PD-1 antibody and the cytokine payload were largely preserved after chemical conjugation. The PD1-IL18 IC exhibited potent antitumor activity in vivo inducing complete responses in the large majority of animals.

Conclusions We generated a potent and IL-18BP-resistant IL-18 payload that can be chemically conjugated to distinct chemical or biological entities in a site-specific manner to generate unique IL-18-based therapeutic formats with desirable pharmacological properties. Both the PEGylated half-life extended IL-18 and the PD1-IL18 IC are well tolerated, show encouraging efficacy in pre-clinical models, and have the potential to be next-generation enhanced IL-18 therapeutics.

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