Interaction of serum amyloid P component with hexanoyl bis(D-proline) (CPHPC).

Under physiological conditions, the pentameric human plasma protein serum amyloid P component (SAP) binds hexanoyl bis(D-proline) (R-1-{6-[R-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl}pyrrolidine-2-carboxylic acid; CPHPC) through its D-proline head groups in a calcium-dependent interaction. Cooperative effects in binding lead to a substantial enhancement of affinity. Five molecules of the bivalent ligand cross-link and stabilize pairs of SAP molecules, forming a decameric complex that is rapidly cleared from the circulation by the liver. Here, it is reported that X-ray analysis of the SAP complex with CPHPC and cadmium ions provides higher resolution detail of the interaction than is observed with calcium ions. Conformational isomers of CPHPC observed in solution by HPLC and by X-ray analysis are compared with the protein-bound form. These are discussed in relation to the development of CPHPC to provide SAP depletion for the treatment of amyloidosis and other indications.

An observational, non-interventional study for the follow-up of patients with amyloidosis who received miridesap followed by dezamizumab in a phase 1 study.

BACKGROUND: Miridesap depletes circulating serum amyloid P (SAP) and dezamizumab (anti-SAP monoclonal antibody) targets SAP on amyloid deposits, triggering amyloid removal. In a phase 1, first-in-human study (FIHS), progressive amyloid removal was observed in some patients after ≤ 3 cycles of miridesap/dezamizumab. METHODS: This observational, non-interventional study in patients who received miridesap/dezamizumab during the FIHS (planned follow-up: 5 years) evaluated response to treatment based on routine assessments of disease status and key organ function. In a post hoc analysis, patients responding to treatment in the FIHS during follow-up were identified as responders and further categorized as sustained or declining responders. RESULTS: In the FIHS, 17/23 patients were treatment responders. Of these patients, seven (immunoglobulin light chain [AL], n = 6; serum amyloid A, n = 1) were considered sustained responders and ten (fibrinogen-a alpha chain [AFib], n = 5; AL, n = 4; apolipoprotein A-I, n = 1) were considered declining responders. We primarily present responder patient-level data for functional, cardiac, laboratory and imaging assessments conducted during the follow-up period, with non-responder data presented as supplementary. CONCLUSION: No further development of miridesap/dezamizumab is planned in amyloidosis. However, long-term follow-up of these patients may provide insight into whether active removal of amyloid deposits has an impact on disease progression. TRIAL REGISTRATION: ClinicalTrials.gov, NCT01777243. Registered 28 January 2013, https://clinicaltrials.gov/ct2/show/study/NCT01777243 .

Pharmacological removal of serum amyloid P component from intracerebral plaques and cerebrovascular Aß amyloid deposits in vivo.

Human amyloid deposits always contain the normal plasma protein serum amyloid P component (SAP), owing to its avid but reversible binding to all amyloid fibrils, including the amyloid ß (Aß) fibrils in the cerebral parenchyma plaques and cerebrovascular amyloid deposits of Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA). SAP promotes amyloid fibril formation in vitro, contributes to persistence of amyloid in vivo and is also itself directly toxic to cerebral neurons. We therefore developed (R)-1-[6-[(R)-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid (CPHPC), a drug that removes SAP from the blood, and thereby also from the cerebrospinal fluid (CSF), in patients with AD. Here we report that, after introduction of transgenic human SAP expression in the TASTPM double transgenic mouse model of AD, all the amyloid deposits contained human SAP. Depletion of circulating human SAP by CPHPC administration in these mice removed all detectable human SAP from both the intracerebral and cerebrovascular amyloid. The demonstration that removal of SAP from the blood and CSF also removes it from these amyloid deposits crucially validates the strategy of the forthcoming 'Depletion of serum amyloid P component in Alzheimer's disease (DESPIAD)' clinical trial of CPHPC. The results also strongly support clinical testing of CPHPC in patients with CAA.