Innate Cell Engager Demonstrates Evidence of Improved EGFR Inhibition in Tumor Cell Lines

The innate cell engager^® (ICE) AFM24 showed greater efficacy in eliciting antibody-dependent cellular phagocytosis of EGFR wild-type and KRAS-mutant tumor cells compared with cetuximab (Erbitux), according to preclinical findings from a study presented in a poster during the 2021 SITC Annual Meeting.

“AFM24 enhances macrophage-mediated antibody-dependent cellular phagocytosis of various EGFR-expressing tumor cell lines, irrespective of the EGFR signaling pathway,” wrote lead study author Sheena Pinto, PhD, translational project leader at Affimed, and coauthors, in the poster.

ICE molecules are made to boost the activity of innate antitumor immune cells. ICE is a bispecific engager of CD16A+ natural killer (NK) cells and macrophages and tumor antigens.

AFM24 is a tetravalent ICE which can bind CD16A and EGFR, the latter of which is overexpressed in many solid cancers and can be associated with poor prognosis.

Current EGFR inhibitors are limited by off-target toxicity and intrinsic and acquired resistance.

However, AFM24 engages CD16A on NK cells and macrophages with a higher affinity than monoclonal antibodies, causing NK cell-mediated antibody-dependent cellular cytotoxicity and macrophage-mediated antibody-dependent cellular phagocytosis.

Moreover, the mechanism of action of AFM24 can surpass the obstacles of current EGFR inhibitors because of its independence to EGFR activity and resulting signaling pathway resistance.

“This mechanism of action may be instrumental to the efficacy of AFM24, especially in macrophage-rich tumors,” wrote the study authors.

Additionally, preclinical and clinical data have shown that ICE molecules could be a safe and effective treatment alone and in combination with other immunotherapies.

In this analysis, investigators evaluated the ability of AFM24 to elicit antibody-dependent cellular phagocytosis in solid tumor cell lines expressing EGFR wild-type or EGFR signaling pathway mutations.

To do so, monocyte-differentiated macrophages from healthy donor peripheral blood mononuclear cells were co-cultured for 4 hours with CMFDA-labeled, wild-type EGFR-expressing or KRAS-mutant tumor cells in the presence of 10 µg/mL of AFM24 or cetuximab. Antibody-dependent cellular phagocytosis was evaluated by flow cytometry.

M0, M1, or M2 macrophages were co-cultured with CMFDA-labeled tumor cells in the presence of increasing concentrations of AFM24. Antibody-dependent cellular phagocytosis was evaluated by flow cytometry.

Finally, M0 macrophages were co-cultured with pHRodo™-labeled tumor cells in the presence of 10 µg/mL of AFM24 or cetuximab. Phagocytosis was evaluated by live cell-imaging analysis with IncuCtye® over 24 hours.

Additional results showed that AFM24 increased antibody-dependent cellular phagocytosis of EGFR-positive tumor cells regardless of macrophage subtype. Moreover, AFM24 was superior to cetuximab in eliciting phagocytosis in EGFR-positive cells in live cell imaging analysis over 24 hours.

Given these findings, AFM24 is now being evaluated in a phase 1/2 trial (NCT04259450) in patients with advanced EGFR-positive solid tumors.

“[AFM24] may offer an alternative therapeutic option, particularly for patients with resistance to conventional EGFR-targeting agents,” concluded the study authors.

Reference

1. Pinto S, Wingert S, Pahl J, et al. Tetravalent, bispecific innate cell engager (ICE®) AFM24 enhances macrophage mediated tumor cell phagocytosis. Presented at: 2021 SITC Annual Meeting; November 10-14; 2021; Washington DC. Abstract 880.