Potential of Sea-CD70 for the Treatment of Myeloid Leukemia
Authors: Diolaiti Daniel , Haass Jane , Ulrich Michelle , Chen Yufei , Ho Phoenix , Gardai Shyra J 
Published: November 2020

CD70 (CD27L) is a member of the tumor necrosis factor superfamily transiently expressed on activated adaptive and innate immune cells. Engagement of CD70 to the co-stimulatory receptor CD27, which is present on adaptive immune cells, promotes antigen-specific T cell responses. Both CD70 and CD27 have been reported to be aberrantly expressed on AML and MDS blasts, but are absent on normal hematopoietic progenitor cells, making them appealing therapeutic targets. CD70-CD27 interactions, working through auto- and/or paracrine signaling, can induce a stem-like signature and stimulate the proliferation of leukemic blasts. In addition, the CD70-CD27 interaction drives inflammatory cytokine production from both CD27 and CD70 pathways, resulting in cytokine production from leukemic blasts and the myeloid cells.
Inflammatory signaling is a critical component of the crosstalk between hematopoietic stem and progenitor cells and their microenvironment during infection or hematopoietic stress. However, chronic inflammation can suppress normal hematopoietic stem cell function and eventually lead to bone marrow failure. Similarly, preleukemic and leukemic cell' interactions with the bone marrow microenvironment can induce secretion of pro-inflammatory factors, which in turn, could suppress normal blood cell formation. Therefore, blockade of the CD70-CD27 inflammatory signal pathway could help restore normal hematopoiesis, limit immune evasion, and increase the immune directed responses in MDS and AML.
SEA-CD70 is a humanized, nonfucosylated monoclonal antibody targeting CD70. SEA-CD70 retains the ability to block CD27 mediated signaling and binds significantly better than the fucosylated parent to the FcγRIIIa receptor. SEA-CD70 mediates potent target killing through Fc-dependent antibody effector functions, including antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), and complement-dependent cytotoxicity (CDC). SEA-CD70 can also disrupt CD70-CD27 signaling and could block cellular proliferation and survival of blast cells in vitro. SEA-CD70 may also inhibit the inflammatory signals originating from the interaction between the tumor microenvironment and leukemic blasts. In vivo, SEA-CD70 delayed tumor growth and increased survival in subcutaneous AML xenograft mouse tumor models both as a single agent and when combined with standard of care (SOC) agents. Overall, our data highlight the therapeutic potential of SEA-CD70 for the treatment of AML and MDS patients.

Disclosures
Diolaiti: Seattle Genetics:Current Employment, Current equity holder in publicly-traded company.Haass:Seattle Genetics:Current Employment, Current equity holder in publicly-traded company.Ulrich:Seattle Genetics:Current Employment, Current equity holder in publicly-traded company.Chen:Seattlke Genetics:Current Employment, Current equity holder in publicly-traded company.Ho:Seattle Genetics:Current Employment, Current equity holder in publicly-traded company.Gardai:Seattle genetics:Current Employment, Current equity holder in publicly-traded company.