Amyloidosis is a malignant pathology associated with the formation of proteinaceous
amyloid fibrils that deposit in organs and tissues, leading to dysfunction and severe morbidity. More than 25
proteins have been identified as components of
amyloid, but the most common form of systemic
amyloidosis is associated with the deposition of
amyloid composed of
Ig light chains (AL). Clinical management of
amyloidosis focuses on reducing synthesis of the
amyloid precursor
protein. However, recently, passive immunotherapy using
amyloid fibril-reactive
antibodies, such as 11-1F4, to remove
amyloid from organs has been shown to be effective at restoring organ function in patients with
AL amyloidosis. However, 11-1F4 does not bind
amyloid in all AL patients, as evidenced by PET/CT imaging, nor does it efficiently bind the many other forms of
amyloid. To enhance the reactivity and expand the utility of the 11-1F4 mAb as an
amyloid immunotherapeutic, we have developed a pretargeting "peptope" comprising a multiamyloid-reactive
peptide, p5+14, fused to a high-affinity
peptide epitope recognized by 11-1F4. The peptope, known as p66, bound the 11-1F4 mAb in vitro with subnanomolar efficiency, exhibited multiamyloid reactivity in vitro and, using tissue biodistribution and SPECT imaging, colocalized with
amyloid deposits in a mouse model of systemic
serum amyloid A amyloidosis. Pretreatment with the peptope induced 11-1F4 mAb accumulation in
serum amyloid A deposits in vivo and enhanced 11-1F4-mediated dissolution of a human AL
amyloid extract implanted in mice.