Agnes Eva Hamburger

Differences in binding and effector functions between classes of TNF antagonists

There are currently two Food and Drug Administration-approved classes of biologic agents that target tumor necrosis factor-alpha (TNF-alpha): anti-TNF monoclonal antibodies (mAbs) (adalimumab and infliximab), and soluble TNF receptors (etanercept). This study examined the ability of the TNF antagonists to: (1) bind various polymorphic variants of cell surface-expressed Fc receptors (FcgammaRs) and the complement component C1q, and (2) mediate Ab-dependent cellular cytotoxicity (ADCC) and complement-mediated cytotoxicity (CDC) killing of cells expressing membrane-bound TNF (mTNF) in vitro. Both mAbs and the soluble TNF receptor demonstrated low-level binding to the activating receptors FcgammaRI, FcgammaRIIa, and FcgammaRIIIa, and the inhibitory receptor FcgammaRIIb, in the absence of exogenous TNF. However, upon addition of TNF, the mAbs, but not etanercept, showed significantly increased binding, in particular to the FcgammaRII and FcgammaRIII receptors. Infliximab and adalimumab induced ADCC much more potently than etanercept. In the presence of TNF, both mAbs bound C1q in in vitro assays, but etanercept did not bind C1q under any conditions. Infliximab and adalimumab also induced CDC in cells expressing mTNF more potently than etanercept. Differences in the ability to bind ligand and mediate cell death may account for the differences in efficacy and safety of TNF antagonists.

FGF21 Can Be Mimicked In Vitro and In Vivo by a Novel Anti-FGFR1c/β-Klotho Bispecific Protein

The endocrine hormone FGF21 has attracted considerable interest as a potential therapeutic for treating diabetes and obesity. As an alternative to the native cytokine, we generated bispecific Avimer polypeptides that bind with high affinity and specificity to one of the receptor and coreceptor pairs used by FGF21, FGFR1c and β-Klotho. These Avimers exhibit FGF21-like activity in in vitro assays with potency greater than FGF21. In a study conducted in obese male cynomolgus monkeys, animals treated with an FGFR1c/β-Klotho bispecific Avimer showed improved metabolic parameters and reduced body weight comparable to the effects seen with FGF21. These results not only demonstrate the essential roles of FGFR1c and β-Klotho in mediating the metabolic effects of FGF21, they also describe a first bispecific activator of this unique receptor complex and provide validation for a novel therapeutic approach to target this potentially important pathway for treating diabetes and obesity.