AFM13 Is the Most Advanced Bispecific NK-Cell Engaging Antibody in Clinical Development Substantially Enhancing NK-Cell Effector Function and Proliferation

Introduction:

AFM13 is an NK-cell engaging CD30/CD16A bispecific tetravalent TandAb antibody currently in phase 2 clinical development in Hodgkin lymphoma (HL) and other CD30⁺ malignancies. It engages NK-cells through CD16A with high affinity and specificity and confers significantly stronger NK-cell activation compared to other therapeutic antibodies. We have previously shown synergistic efficacy when NK-cell activation by AFM13 is combined with check-point modulation such as anti-PD-1 treatment, which is known to unleash T cell and NK-cell activity. The goal of this study was to identify further candidates for combination treatments and biomarkers that potentially indicate NK-cell responses to AFM13 treatment.

Methods:

AFM13-mediated NK-cell cytotoxicity and IFN-γ production after 4-hour interaction with HL cell lines was measured by ⁵¹Cr release assays and flow cytometry, respectively. Expression of NK-cell receptors, NK-cell proliferation (CFSE dilution) and expansion (absolute cell counts) was analyzed by flow cytometry.

Results:

The interaction of NK-cells with AFM13-coated tumor cells up-regulated the expression of NK-cell receptors such as CD25, CD69, CD137/4-1BB as well as molecules that may serve as NK-cell check-points when compared with the unrelated NK-cell binding TandAb AFM12 that does not bind to target cells. Importantly, CD16A engagement by AFM13 enhanced the proliferation and expansion potential of NK-cells when subsequently incubated with IL-15 or with particularly low doses of IL-2. NK-cell cytotoxicity and IFN-γ production was substantially increased towards CD30⁺ tumor cells in the presence of AFM13. Even target cells resistant to naïve and IL-2/IL-15-activated NK-cells were susceptible to AFM13-induced NK-cell cytotoxicity. AFM13 concentrations of as low as 10^-2 µg/mL resulted in maximal activity while AFM13 was significantly more potent than native anti-CD30 IgG1 antibody. NK-cell activation by IL-2 or IL-15 had a synergistic effect on AFM13-mediated cytotoxicity.

Conclusion:

AFM13 specifically enhances the cytotoxic, proliferative and cytokine-producing potential of NK-cells. Our data indicate that the distinctive modulation of NK-cell receptors can be utilized to monitor NK-cell responses during AFM13 therapy and provides candidates for therapeutic combination strategies. Moreover, the combination with low doses of IL-2 or with IL-15 may expand the quantity of tumor-reactive NK-cells after AFM13 treatment and promote NK-cell functionality in the tumor microenvironment in cancer patients.