Directed evolution of and structural insights into antibody-mediated disruption of a stable receptor-ligand complex.

Antibody drugs exert therapeutic effects via a range of mechanisms, including competitive inhibition, allosteric modulation, and immune effector mechanisms. Facilitated dissociation is an additional mechanism where antibody-mediated "disruption" of stable high-affinity macromolecular complexes can potentially enhance therapeutic efficacy. However, this mechanism is not well understood or utilized therapeutically. Here, we investigate and engineer the weak disruptive activity of an existing therapeutic antibody, omalizumab, which targets IgE antibodies to block the allergic response. We develop a yeast display approach to select for and engineer antibody disruptive efficiency and generate potent omalizumab variants that dissociate receptor-bound IgE. We determine a low resolution cryo-EM structure of a transient disruption intermediate containing the IgE-Fc, its partially dissociated receptor and an antibody inhibitor. Our results provide a conceptual framework for engineering disruptive inhibitors for other targets, insights into the failure in clinical trials of the previous high affinity omalizumab HAE variant and anti-IgE antibodies that safely and rapidly disarm allergic effector cells.

Structure-guided design of ultrapotent disruptive IgE inhibitors to rapidly terminate acute allergic reactions.

BACKGROUND: Anaphylaxis represents one of the most severe and fatal forms of allergic reactions. Like most other allergies, it is caused by activation of basophils and mast cells by allergen-mediated cross-linking of IgE bound to its high-affinity receptor, FcεRI, on the cell surface. The systemic release of soluble mediators induces an inflammatory cascade, rapidly causing symptoms with peak severity in minutes to hours after allergen exposure. Primary treatment for anaphylaxis consists of immediate intramuscular administration of adrenaline. OBJECTIVE: While adrenaline alleviates life-threatening symptoms of an anaphylactic reaction, there are currently no disease-modifying interventions available. We sought to develop potent and fast-acting IgE inhibitors with the potential to rapidly terminate acute allergic reactions. METHODS: Using affinity maturation by yeast display and structure-guided molecular engineering, we generated 3 optimized disruptive IgE inhibitors based on designed ankyrin repeat proteins and assessed their ability to actively remove IgE from allergic effector cells in vitro as well as in vivo in mice. RESULTS: The engineered IgE inhibitors rapidly dissociate preformed IgE:FcεRI complexes, terminate IgE-mediated signaling in preactivated human blood basophils in vitro, and shut down preinitiated allergic reactions and anaphylaxis in mice in vivo. CONCLUSIONS: Fast-acting disruptive IgE inhibitors demonstrate the feasibility of developing kinetically optimized inhibitors for the treatment of anaphylaxis and the rapid desensitization of allergic individuals.

Eosinophils regulate adipose tissue inflammation and sustain physical and immunological fitness in old age.

Adipose tissue eosinophils (ATEs) are important in the control of obesity-associated inflammation and metabolic disease. However, the way in which ageing impacts the regulatory role of ATEs remains unknown. Here, we show that ATEs undergo major age-related changes in distribution and function associated with impaired adipose tissue homeostasis and systemic low-grade inflammation in both humans and mice. We find that exposure to a young systemic environment partially restores ATE distribution in aged parabionts and reduces adipose tissue inflammation. Approaches to restore ATE distribution using adoptive transfer of eosinophils from young mice into aged recipients proved sufficient to dampen age-related local and systemic low-grade inflammation. Importantly, restoration of a youthful systemic milieu by means of eosinophil transfers resulted in systemic rejuvenation of the aged host, manifesting in improved physical and immune fitness that was partially mediated by eosinophil-derived IL-4. Together, these findings support a critical function of adipose tissue as a source of pro-ageing factors and uncover a new role of eosinophils in promoting healthy ageing by sustaining adipose tissue homeostasis.

The mechanistic and functional profile of the therapeutic anti-IgE antibody ligelizumab differs from omalizumab.

Targeting of immunoglobulin E (IgE) represents an interesting approach for the treatment of allergic disorders. A high-affinity monoclonal anti-IgE antibody, ligelizumab, has recently been developed to overcome some of the limitations associated with the clinical use of the therapeutic anti-IgE antibody, omalizumab. Here, we determine the molecular binding profile and functional modes-of-action of ligelizumab. We solve the crystal structure of ligelizumab bound to IgE, and report epitope differences between ligelizumab and omalizumab that contribute to their qualitatively distinct IgE-receptor inhibition profiles. While ligelizumab shows superior inhibition of IgE binding to FcεRI, basophil activation, IgE production by B cells and passive systemic anaphylaxis in an in vivo mouse model, ligelizumab is less potent in inhibiting IgE:CD23 interactions than omalizumab. Our data thus provide a structural and mechanistic foundation for understanding the efficient suppression of FcεRI-dependent allergic reactions by ligelizumab in vitro as well as in vivo.

Targeting IgE in allergic disease.

Immunoglobulin E (IgE) represents the least abundant antibody isotype in human serum. Nevertheless, it has the ability to induce potent allergic reactions. As a key component in the development and manifestation of hypersensitivity responses against usually non-hazardous foreign substances, IgE has become a major target of investigation and the subject of multiple therapeutic approaches for the treatment of allergies. Recent advances in the understanding of pathophysiologic mechanisms underlying IgE-associated allergic disorders have led to the generation of new drug candidates that are currently in development or under clinical evaluation. In this review, we highlight molecular and structural mechanisms underlying the different anti-IgE molecules and suggest a concept of multi-level targeting using a new class of disruptive IgE inhibitors to potentially optimize treatment efficacy.

Nogo-A antibodies and training reduce muscle spasms in spinal cord-injured rats.

OBJECTIVE: Spinal cord injury (SCI) leads to permanent motor and sensory deficits due to the damage of ascending and descending fiber tracts. In addition, malfunctions such as neuropathic pain or muscle spasms develop in many patients, possibly caused by injury-induced plastic changes of neuronal circuits above and below the lesion. New treatment strategies for spinal cord injury aim at enhancing plasticity and neurite growth, for example, by blocking the key neurite growth inhibitor Nogo-A or its downstream effectors. It is therefore crucial to investigate potential effects of such treatments on malfunctions such as muscle spasms. In addition, locomotor training, now a standard therapeutic tool to improve walking ability in incomplete SCI subjects, can be expected to influence the rearrangement of spinal cord circuits and the development of muscle spasms and other malfunctions. METHODS AND RESULTS: Here we present and validate a new rat model for muscle spasms after incomplete SCI and show that both intrathecal anti-Nogo-A antibody treatment and locomotor training, started early after injury, permanently reduce the development of muscle spasms. INTERPRETATION: The results show that an antibody-mediated suppression of the growth inhibitory protein Nogo-A leads to functional recovery and a lower level of malfunctions, suggesting the formation of functionally meaningful connections in the damaged spinal cord. Treadmill training early after SCI also has a beneficial effect.