Preclinical development of an anti-CD30/anti-CD16A bispecific tetravalent TandAb antibody for the treatment of Hodgkin lymphoma.

Abstract

e18532 Background: CD30 is a validated tumor target that is expressed on both Hodgkin’s Lymphoma cells and some activated immune cells. To improve antibody-based therapies targeting CD30, Affimed developed an NK cell-recruiting bispecific antibody. Methods: To enhance the recruitment and activation of NK cells for tumor cell lysis, we isolated a human antibody that is highly specific for the A isoform of FcgRIII (CD16A). Its variable domain (Fv) was used to construct a tetravalent bispecific TandAb, consisting of four Fvs linked in tandem, with two binding sites for both the CD16A on NK cell and the CD30 target cell antigens. The resulting anti-CD30/anti-CD16A bispecific tetravalent TandAb AFM13 was compared to both an anti-CD30/anti-CD16A bispecific diabody and an Fc-enhanced anti-CD30 IgG in binding and cytotoxicity assays in vitro. Pharmacokinetics and safety of the TandAb were investigated in Cynomolgus monkeys. Results: AFM13 is retained longer on NK cells than either the anti-CD30 IgG or the bispecific diabody due to its bivalency for CD16A; it binds both CD16A alleles (158F, 158V) equally well indicating the potential for broader patient response than that achieved with current therapeutic mAbs. AFM13 did not induce systemic activation of NK cells. It displays higher potency (EC50) and higher efficacy (maximal lysis) than either the anti-VD30 IgGs or the bispecific diabody in a cytotoxicity assay. The cytotoxic activity of AFM13 is unaffected by physiological concentrations of polyclonal IgG, whereas that of anti-CD30 IgGs is dramatically reduced. Cynomolgus monkeys were identified as the only relevant species for toxicity testing. Pharmacokinetics studies reveal AFM13 half-lives of up to 22.9 h after repeated dosing. MTD was not reached in a single dose escalation study ranging to 100 mg/kg maximum. A 28 days toxicity study, with dosing up to 10 mg/kg every other day, revealed an excellent safety profile. No signs of immunotoxicity or systemic cytokine release were observed. Conclusions: AFM13 may be a more effective treatment for Hodgkin’s Lymphoma that is refractory to treatment with anti-CD30 IgGs and is under evaluation in a Phase I clinical trial.