Therapeutic Clearance of Amyloid
Can tissue amyloid deposits be removed with an antibody to serum amyloid P component (SAP)?
Fifteen patients with systemic amyloidosis (no cardiac involvement) were enrolled in this phase 1 trial. After circulating SAP was depleted with (R)-1-[6-[(R)-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid (CPHPC), a humanized monoclonal immunoglobulin G1 (IgG1) anti-SAP antibody was infused. Endpoints included organ function, inflammatory markers, and amyloid load. Liver stiffness was measured with transient elastography and amyloid was measured with SAP scintigraphy.
After 6 weeks, antibody-treated patients had decreased liver stiffness, improvements in liver function, and reduced hepatic amyloid load. A reduction in kidney amyloid and shrinkage of an amyloid-laden lymph node were also observed. There were no serious adverse events.
The authors concluded that treatment with CPHPC followed by an anti-SAP antibody safely triggered clearance of amyloid deposits from the liver and some other tissues.
Treatment options are limited for systemic amyloidosis. CPHPC efficiently depletes SAP from the plasma, but not SAP in amyloid tissue deposits. Anti-SAP antibodies have previously been shown to initiate clearance of visceral amyloid deposits, presumably by binding to amyloid, activating complement, and recruiting macrophages that engulf the deposits. In this study, which included subjects with different types of systemic amyloidosis, antibody treatment appeared to be safe and effective. Effectiveness of this promising therapy in patients with extensive cardiac amyloidosis will be tested in future trials.
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