Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.
Lead Author: Aubin Michalon; Submitting Author (for all communications): Peter Christian Kahr; Institution: Neurimmune; City/State: Schlieren, Zurich, Switzerland

Main Body of the Abstract
Background: Extracellular deposition of transthyretin amyloid (ATTR) is the hallmark of ATTR cardiomyopathy and reducing cardiac ATTR load is a key therapeutic goal to achieve improvements in cardiac function. ALXN2220, previously known as NI006, is a recombinant human antibody designed to activate ATTR depletion by phagocytic immune cells and is currently undergoing clinical investigation (NCT04360434, NCT06183931). Here, we studied the cellular mechanisms of ALXN2220-mediated ATTR depletion in patient-derived cardiac tissue.

Methods: Refractive index tomography, a novel technology enabling non-invasive, ex vivo, high-resolution live-cell imaging was used to investigate the phagocytic process activated by ALXN2220. Human THP-1 macrophages were incubated with patient-derived cardiac tissue in presence of ALXN2220 or isotype control and imaged over a 24-hour period.

Results: ALXN2220 selectively bound to ATTR amyloid as demonstrated by colocalization of fluorescently labelled ALXN2220 and thioflavin-s staining. In the absence of ALXN2220, no phagocytosis of ATTR amyloid could be observed in this experimental set-up. Addition of ALXN2220 triggered the process of antibody-mediated amyloid removal including recruitment of macrophages to amyloid deposits, detachment, internalization, and degradation of ATTR. Multinucleated giant cells participated in the phagocytosis of large amyloid fragments. 
Conclusions: Using a novel technology for high-resolution live-cell imaging, ALXN2220-mediated amyloid depletion from patient cardiac tissue was demonstrated. These visualizations further our understanding of the cellular mechanism involved in antibody-mediated phagocytosis as a potential precision immunotherapy for patients with ATTR cardiomyopathy.

**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Lead Author: Aubin Michalon; Submitting Author (for all communications): Peter Christian Kahr; Institution: Neurimmune; City/State: Schlieren, Zurich, Switzerland

**Main Body of the Abstract**
**Background:** Extracellular deposition of transthyretin amyloid (ATTR) is the hallmark of ATTR cardiomyopathy and reducing cardiac ATTR load is a key therapeutic goal to achieve improvements in cardiac function. ALXN2220, previously known as NI006, is a recombinant human antibody designed to activate ATTR depletion by phagocytic immune cells and is currently undergoing clinical investigation (NCT04360434, NCT06183931). Here, we studied the cellular mechanisms of ALXN2220-mediated ATTR depletion in patient-derived cardiac tissue.

**Methods:** Refractive index tomography, a novel technology enabling non-invasive, ex vivo, high-resolution live-cell imaging was used to investigate the phagocytic process activated by ALXN2220. Human THP-1 macrophages were incubated with patient-derived cardiac tissue in presence of ALXN2220 or isotype control and imaged over a 24-hour period.

**Results:** ALXN2220 selectively bound to ATTR amyloid as demonstrated by colocalization of fluorescently labelled ALXN2220 and thioflavin-s staining. In the absence of ALXN2220, no phagocytosis of ATTR amyloid could be observed in this experimental set-up. Addition of ALXN2220 triggered the process of antibody-mediated amyloid removal including recruitment of macrophages to amyloid deposits, detachment, internalization, and degradation of ATTR. Multinucleated giant cells participated in the phagocytosis of large amyloid fragments. 
**Conclusions:** Using a novel technology for high-resolution live-cell imaging, ALXN2220-mediated amyloid depletion from patient cardiac tissue was demonstrated. These visualizations further our understanding of the cellular mechanism involved in antibody-mediated phagocytosis as a potential precision immunotherapy for patients with ATTR cardiomyopathy.

ALXN2220: high-resolution live-cell imaging of antibody-mediated cardiac ATTR amyloid depletion PB1 (#226)

We invite you to attend the XIX International Symposium on Amyloidosis to be held in Rochester, MN.

This symposium is organized as a hybrid meeting (with the focus on in-person) held from Sunday, May 26 through Thursday, May 30, 2024.

Together with the ISA Board and members of Mayo Clinic, a very attractive scientific hybrid program is being planned. The program will cover a variety of types of systemic amyloidosis: ATTR (hereditary and wild-type), AL (light-chain), AA and less frequent forms. There will be key lectures, specific symposia including those company sponsored, oral presentations and poster sessions of accepted abstracts.

COURSE DESCRIPTION
This program will provide a comprehensive review of state-of-the-art education in systemic amyloidosis: basic science, pathophysiology, diagnosis, current and emerging treatments. Scientific presentations will include competitive oral and poster abstracts. The rapid evolution of scientific discovery and expanding treatment options has created tremendous interest in the field and this meeting will fill and important gap in educating scientists and clinicians.