Evaluation of the Therapeutic Potential of a HER3-Binding Affibody Construct TAM-HER3 in Comparison with a Monoclonal Antibody, Seribantumab

Abstract

Human epidermal growth factor receptor type 3 (HER3) is recognized to be involved in resistance to HER-targeting therapies. A number of HER3-targeting monoclonal antibodies are under clinical investigation as potential cancer therapeutics. Smaller high-affinity scaffold proteins are attractive non-Fc containing alternatives to antibodies. A previous study indicated that anti-HER3 affibody molecules could delay the growth of xenografted HER3-positive tumors. Here, we designed a second-generation HER3-targeting construct (TAM-HER3), containing two HER3-specific affibody molecules bridged by an albumin-binding domain (ABD) for extension of blood circulation. Receptor blocking activity was demonstrated in vitro. In mice bearing BxPC-3 xenografts, the therapeutic efficacy of TAM-HER3 was compared to the HER3-specific monoclonal antibody seribantumab (MM-121). TAM-HER3 inhibited heregulin-induced phosphorylation in a panel of HER3-expressing cancer cells and was found to be equally as potent as seribantumab in terms of therapeutic efficacy in vivo and with a similar safety profile. Median survival times were 60 days for TAM-HER3, 54 days for seribantumab, and 41 days for the control group. No pathological changes were observed in cytopathological examination. The multimeric HER3-binding affibody molecule in fusion to ABD seems promising for further evaluation as candidate therapeutics for treatment of HER3-overexpressing tumors.

Evaluation of a radiocobalt-labelled affibody molecule for imaging of human epidermal growth factor receptor 3 expression

“…The anti-HER3 affibody molecules also demonstrated cross-species reactivity with the murine HER3 counterpart, mErbB3 (31), and murine models would therefore reflect the factors influencing the distribution of the anti-HER3 affibody molecules in humans. In preclinical therapy studies, treatment of mice with a construct containing two anti-HER3 affibody molecules (600 µg/injection, 3 injections/week) up to 70 days was not associated with any toxicity (32,33).…”

“…Many more potential drug candidates are in preclinical evaluation. Additionally, we have recently demonstrated that an anti-HER3 affibody dimer fused with a domain with high affinity to albumin, Z HER3 -ABD-Z HER3 , inhibited HER3-induced phosphorylation in vitro and delayed growth of HER3 expressing tumours in vivo (32,33). The fact that 57 Co-Z HER3 binds to the same epitope as the anti-HER3 therapeutic agents seribantumab (47) and the affibody conjugate Z HER3 -ABD-Z HER3 (32) makes it appropriate to use this conjugate to monitor receptor occupancy during therapy.…”

Influence of Molecular Design on the Targeting Properties of ABD-Fused Mono- and Bi-Valent Anti-HER3 Affibody Therapeutic Constructs

“…Indeed, in vitro the bi- and trivalent HER3-specific affibody molecules were significantly more efficient in blocking phosphorylation of HER3 and inhibiting cellular activity and proliferation compared to the monovalent control [ 20 , 26 ]. We demonstrated that a bivalent construct based on an anti-HER3 affibody molecule fused with ABD, 3A3, also efficiently inhibited growth of HER3-expressing cells in vitro, had prolonged in vivo half-life, delayed growth of HER3-expressing BxPC-3 xenografts in mice, and was equipotent to seribantumab (MM-121) [ 27 , 28 ]. Importantly there was no observable toxicity after multiple administrations of the construct [ 28 ].…”

Generation of novel affibody molecules targeting the EBV LMP2A N-terminal domain with inhibiting effects on the proliferation of nasopharyngeal carcinoma cells

“…For therapeutic applications solely based on blocking the activity of tumour-related target protein as a mechanism of action, the fragment crystallisable (Fc) region of mAbs mediating, for instance, complement-dependent cytotoxicity and antibodydependent cell-mediated cytotoxicity (ADCC) is not required and might even be undesired 21 . Similar to non-Fc-portion antibody derivatives, such as scFv, fragment variable (Fv), and fragment antigen binding (Fab), affibody molecules are very valuable alternatives for such indications, and several affibody-based tumour targeting therapeutic agents with robust biological activity and no immunogenicity issues have been reported 30,38,39 . Affibody molecules do not contain any disulphide bridges, an observation suggesting that they could fold in the reducing environment of the cell cytoplasm 40 .…”