503 KH-801, a differentated humanized anti-CD24 antibody, potentiates the effects of immunomodulatory and anti-tumor activity in preclinical cancer models with favorable safety profiles

Background

CD24 is a small GPI-anchored, highly glycosylated membrane protein, which interacting with Siglec-10 on TAMs (Tumor Associated Macrophages) acting as 'don't eat me' signals, and helping tumor cells avoid being engulfed by macrophages. CD24 is widely detected in many solid tumors.¹ We have developed a unique humanized anti-CD24 antibody, KH-801, that depletes tumor cells not only by the Fc-mediated immune effector function, but also through blocking the CD24/Siglec10 axis signals in vivo and in vitro preclinical models.

Methods

Cell-based binding to human T cell, human B cell , human granulocyte and a panel of tumor cells was evaluated by flow cytometry. Mice M2 TAMs elimination and T cell infiltration in vivo were evaluated by flow cytometry after anatomy. The ability of KH-801 in enhancing phagocytosis of tumor cells was evaluated using human monocyte-derived M2 macrophage by live-cell microscopy and flow cytometry. in vivo efficacy of KH-801 was test in wild-type C57BL/6 and C57BL/6J^{Smoc-Siglecgtm1(hSIGLEC10)/Smoc} bearing MC38 murine syngeneic colorectal cancer cells stable expressing human CD24. Toxicokinetics parameters of KH801 were evaluated in the one-month multiple-dose toxicity study in cynomolgus monkeys.

Results

KH-801 selectively binds to tumor cells compared to CD24 positive blood cells such as granulocytes, B cells and T cells, which may improve the therapeutic window of KH-801 in clinic (figure 1). KH-801 significantly promotes human monocyte-derived M2 macrophage phagocytosis of tumor cells with a single-digit nM activity. KH-801 Fc variant 2 without binding to FcγRs, still promote phagocytosis of Monocyte-derived M2 macrophages (figure 2). The results indicate that KH-801, a IgG1 isotype antibody, promotes phagocytosis of tumor cells not only through the Fc-mediated immune effector function, but also the blocking of CD24/Siglec10 axis signals. Besides, KH-801 promotes T cell infiltration into the tumor tissues and M2 TAMs elimination, that may transform cold tumors into hot tumors, and increase the anti-tumor potential for combination with other checkpoint inhibitors (figure 3). Moreover, dose-dependent anti-tumor efficacy has been demonstrated in multiple mouse tumor xenograft models (figure 4). Additionly, the differentiated epitope makes KH-801 exhibit good tolerance in monkey non-GLP toxicity studyv (table 1).

Conclusions

KH801 displays potent tumor growth inhibition activity through not only phagocytosis enhancement by blocking of CD24/Siglec10 axis signals, ADCC and ADCP to kill tumor cells directly, but also regulating tumor microenvironment by enhancing M2 TAMs elimination and T cell infiltration. The results show that KH-801 has potential treatment value in a variety of solid tumors.

References

Barkal AA, Brewer RE, Markovic M, Kowarsky M, Barkal SA, Zaro BW, Krishnan V, Hatakeyama J, Dorigo O, Barkal LJ, Weissman IL. CD24 signalling through macrophage Siglec-10 is a target for cancer immunotherapy. Nature. 2019 Aug;572(7769):392–396.