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573 A novel human anti-PD1/IL15 bi-functional protein with robust anti-tumor activity and low systemic toxicity
  1. Dan Lu1,
  2. Zhanna Polonskaya2,
  3. Tzu-Pei Chang2,
  4. Stella Martomo2,
  5. Xenia Luna2,
  6. Zhikai Zhang2,
  7. Stanley Ng2,
  8. Faical Miyara2 and
  9. Jeegar Patel2
  1. 1Kadmon Corporation, New York, NY, USA
  2. 2Kadmon Pharmceuticals, LLC, New York, NY, USA


Background IL-15 is a key cytokine promoting CD8+ T, NK, and NKT cell proliferation and has demonstrated clinical activity in cancer patients without evidence of any Treg stimulation.1 2 However, its short half-life and systemic toxicity limit its clinical utility. Kadmon has established an IL-15 fusion protein platform to extend the IL-15 serum half-life and direct its action to the tumor microenvironment.3 A major asset of this platform is anti-PD1/IL15 bifunctional protein. To test the bifunctionality hypothesis of this fusion protein in murine models, four different formats of the surrogate bi-functional proteins were engineered by fusing mouse IL-15 to a mouse-human chimeric anti-mouse PD1 antibody (m3A7). We presented earlier that the single IL-15 N-terminal fusion to anti-PD1 antibody (1N-IL-15/m3A7) showed significantly stronger anti-tumor activity in vivo mainly due to the cis-presentation to the PD1 and IL2Rβγ co-expressed on TILs. The cis-presentation potentially maximizes the bi-functionality of PD1 blockade and IL-15 stimulation.4 Here, the therapeutic single IL-15 N-terminal fusion antibodies containing a novel human PD1 antagonist antibody (38B2) and either wild-type IL15 (1N-IL-15/38B2) or mutated 65S-IL15 (65S-1N-IL-15/38B2) have been constructed; their anti-PD1 functions, IL15 stimulation and anti-tumor activities were evaluated.

Methods Purified 1N-IL-15/38B2 and 65S-1N-IL-15/38B2 were generated and characterized in vitro.4 The anti-tumor activities were examined in the human-PD-1/PD-L1 transgenic BALB/c mice subcutaneously transplanted with the human-PD-L1 positive CT26 colon carcinoma. The treatment was started when tumors reached 100 mm3 (IP, QW).

Results All 1N-IL-15/anti-PD1 fusions showed similar potencies in binding to the soluble and cell expressed human PD1 and blocking the hPDL-1 binding to hPD1. Comparing to wild-type 1N-IL-15/38B2, mutated 65S-1N-IL-15/38B2 showed lower stimulation (>150 folds) in the M07e, CTLL2, mouse spleen cells and hPBMC (mainly CD8T+ T cell) proliferation. When we treated hPDL1-CT26 tumor transplanted hPDL1-hPD1 transgenic mice with 65S-1N-IL-15/38B2 at 6 mg/kg, 80% of tumor growth inhibition (TGI) was achieved with no body-weight loss. Although wild-type 1N-IL-15/38B2 at 3 mg/kg demonstrated similar efficacy, a significant mouse body-weight loss was observed and 1/3 mice died after second injection. No anti-tumor activity was observed for 65S-1N-IL-15 non-target fusion in 6 mg/kg.

Conclusions The previous observation of robust anti-tumor activity of surrogate 1N-IL-15/m3A7 in PD1 resistant LL2 model was replicated with the therapeutic bifunctional protein in this study. We also found that lower stimulation 65S-1N-IL-15/38B2 showed strong anti-tumor activity with significant low systemic toxicity; suggesting that the 65S mutation increased the therapeutic window of this bi-functional protein


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  2. Waldmann TA. Cytokines in Cancer Immunotherapy. Cold Spring Harb Perspect Biol 2018;103. Martomo, S. etc. ESMO 2019 1221P; SITC 2019 P#4854. Polonskaya Z. etc. AACR 2020 #2263

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