Abstract 910: A novel bifunctional anti-PD-1 IL-7 fusion protein to reinvigorate exhausted T cell and disarms Treg suppressive activity
Authors: Morello Aurore , Durand Justine , Thepenier Virginie , Teppaz Géraldine , Seite Margaux , Pengam Sabrina , Mary Caroline , Poirier Nicolas 
Published: September 2020

Abstract
Despite the clinical success of anti-PD(L)1 therapy, the majority of patient remain unresponsive or fail to develop a durable response. We explored a second generation of PD-1 antibody by fusing IL-7 cytokine to the Fc portion, called BiCKI® IL-7. The high affinity of the anti PD-1 antibody will allow the concentration/retention of the drug into the tumor microenvironment and preferentially deliver IL-7 in cis-dependent manner to PD-1+ cells. IL-7 is an optimal target for immunotherapy to preferentially stimulate effector T-cell (Teff) functions over regulatory T-cells (Treg)due to the differential expression of IL-7R and poor capacity of IL-7 to stimulate Treg proliferation. Moreover, It has been published that PD-1 blockades increase IL-7R expression and improve IL-7 signaling in exhausted T-cells rationalizing our combinatorial approach.
Results Our anti PD-1/IL-7 bispecific antibody efficiently blocks the PD-1/PD-L1 and PD-L2 interactions and the PD-1-mediated inhibitory signal (pSHP1) and in parallel activates IL-7R pSTAT5 signaling into T cells. Anti PD-1/IL-7 preferentially binds in cis to T cells coexpressing PD-1 and CD127 enabling a selective activation of primed antigen- experienced T cells over PD1-negative (e.g. naïve) cells. A high affinity/avidity of the molecule was observed using biosensor when both receptor CD127 and PD-1, supporting the cis-targeting activity of the drug. Using in vitro T cell activation bioassay, we observed that IL-7 portion fused to the anti-PD-1 synergizes to enhance TCR mediated signaling (NFAT) through activation of the non-canonical pathway while IL-7 in combination with anti-PD1 (two separates product) has no additive effect. Although IL-7R expression decrease over chronic stimulation of Teff cells, we demonstrated that IL-7 efficiently activates progenitor and some fully-exhausted human T-cells (pSTAT5) and maintain their proliferation and survival capacity. This IL-7R signaling activation was associated with a significant increased IFNγ secretion using ex-vivo fresh human tumor explant culture. A significant higher IFNγ production was obtained with anti PD-1/IL-7compared to anti PD-1 treatment alone, including in non-responder patients to anti-PD1, suggesting that the anti PD-1/IL-7 bispecific can reactivate TILs that are resistant to PD-1 therapy. Knowing that Tregs have a key suppressive function, we also explored the possibility that anti-PD-1/IL-7 affect Treg functions. In a human Treg/Teff coculture assay, anti PD-1/IL-7 abrogates the Treg capacity to inhibit proliferation and IFN-g secretion of CD8+ Teff. Moreover, IL-7 and anti-PD-1/IL-7 does not stimulate Treg proliferation, in contrast to IL-2 and IL-15.
Conclusion Our data validate the therapeutic potential of providing IL-7 signals to overcome PD-1 resistance. The bifunctional anti-PD1/IL-7 favors the T-cell effector over T-regulatory immune balance by stimulating Teff cells and exhausted T-cell, while disarming Tregs suppressive functions.
Citation Format: Aurore Morello, Justine Durand, Virginie Thepenier, Géraldine Teppaz, Margaux Seite, Sabrina Pengam, Caroline Mary, Nicolas Poirier. A novel bifunctional anti-PD-1 IL-7 fusion protein to reinvigorate exhausted T cell and disarms Treg suppressive activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 910.