Anti‐αLβ2 antibodies reveal novel endocytotic cross‐modulatory functionality

Abstract

Background and Purpose: Antibodies targeting cell surface receptors are considered to enable highly selective therapeutic interventions for immune disorders and cancer.Their biological profiles are found, generally, to represent the net effects of antibody-target interactions. The former therapeutic anti-integrin αLβ2 antibody efalizumab seems to defeat this paradigm by eliciting, via mechanisms currently unknown, much broader effects than would be predicted based on its target specificity. Experimental Approach:To elucidate the mechanisms behind these broad effects, we investigated in primary human lymphocytes in vitro the effects of anti-αLβ2 antibodies on the expression of αLβ2 as well as unrelated α4 integrins, in comparison to Fab fragments and small-molecule inhibitors. Key Results:We demonstrate that anti-αLβ2 mAbs directly induce the internalization of α4 integrins. The endocytotic phenomenon is a direct consequence of their antibody nature. It is inhibited when monovalent Fab fragments or small-molecule inhibitors are used. It is independent of crosslinking via anti-Fc mAbs and of αLβ2 activation. The cross-modulatory effect is unidirectional and not observed in a similar fashion with the α4 integrin antibody natalizumab. Conclusion and Implications:The present study identifies endocytotic crossmodulation as a hitherto unknown non-canonical functionality of anti-αLβ2 antibodies. This cross-modulation has the potential to fundamentally alter an antibody's benefit risk profile, as evident with efalizumab. The newly described phenomenon may be of relevance to other therapeutic antibodies targeting cluster-forming receptors. Thus, pharmacologists should be cognizant of this action when investigating such antibodies.

Decrypting Integrins by Mixed-Solvent Molecular Dynamics Simulations

“…To the best of our knowledge SAN-300, a humanized monoclonal antibody apparently no longer in development, was the sole modality explored clinically for the treatment of rheumatoid arthritis . As anti-integrin antibodies are known to be associated with substantive limitations, allosteric targeting of VLA-1 by small molecules may emerge as an important translational advance. Target indications of high medical need under consideration for future VLA-1 inhibitors include inflammatory, fibrotic, and malignant diseases. − …”

T-Cell Adhesion in Healthy and Inflamed Skin

“…However, while efalizumab effectively reduces LFA-1 at the T cell surface, it was also observed to cause downregulation of  4  1 (Grönholm et al 2016;Guttman-Yassky et al 2008;Mancuso et al 2020). The mechanisms underlying this response are unclear; however, outside-in signaling through LFA-1 is known to influence  4  1 and crosstalk between these integrins is a feature of their molecular function (Grönholm et al 2016;Kim and Hammer 2019;Mancuso et al 2020). In vitro experiments indicate that efalizumab can induce  4  1 without LFA-1 activation which is a requirement for integrin crosstalk (Mancuso et al 2020).…”

“…Efalizumab, which was briefly approved for treating psoriasis before being removed from the market owing to incidences of PML (complication risk of 1 in 400 compared with that of 1 in 1,000 for natalizumab), illustrates an additional complexity in developing integrin-based drugs ( Cortese et al., 2021 ; Ley et al., 2016 ). An anti-α L monoclonal, efalizumab, was expected to be highly specific for blocking LFA-1 (α L β 2 ) because the α L integrin chain only pairs with β 2 ( Ley et al., 2016 ; Mancuso et al., 2020 ). However, although efalizumab effectively reduces LFA-1 at the T-cell surface, it was also observed to cause the downregulation of α 4 β 1 ( Grönholm et al., 2016 ; Guttman-Yassky et al., 2008 ; Mancuso et al., 2020 ).…”

“…An anti-α L monoclonal, efalizumab, was expected to be highly specific for blocking LFA-1 (α L β 2 ) because the α L integrin chain only pairs with β 2 ( Ley et al., 2016 ; Mancuso et al., 2020 ). However, although efalizumab effectively reduces LFA-1 at the T-cell surface, it was also observed to cause the downregulation of α 4 β 1 ( Grönholm et al., 2016 ; Guttman-Yassky et al., 2008 ; Mancuso et al., 2020 ). The mechanisms underlying this response are unclear; however, outside-in signaling through LFA-1 is known to influence α 4 β 1, and crosstalk between these integrins is a feature of their molecular function ( Grönholm et al., 2016 ; Kim and Hammer, 2019 ; Mancuso et al., 2020 ).…”

“…The mechanisms underlying this response are unclear; however, outside-in signaling through LFA-1 is known to influence α 4 β 1, and crosstalk between these integrins is a feature of their molecular function ( Grönholm et al., 2016 ; Kim and Hammer, 2019 ; Mancuso et al., 2020 ). In vitro experiments indicate that efalizumab can induce α 4 β 1 without LFA-1 activation, which is a requirement for integrin crosstalk ( Mancuso et al., 2020 ). Therefore, α 4 β 1 downregulation may occur through additional biochemical interactions.…”