Pharmacodynamic evaluation and safety assessment of treatment with antibodies to serum amyloid P component in patients with cardiac amyloidosis: an open-label Phase 2 study and an adjunctive immuno-PET imaging study

BACKGROUND

In a Phase I study treatment with the serum amyloid P component (SAP) depleter miridesap followed by monoclonal antibody to SAP (dezamizumab) showed removal of amyloid from liver, spleen and kidney in patients with systemic amyloidosis. We report results from a Phase 2 study and concurrent immuno-positron emission tomography (PET) study assessing efficacy, pharmacodynamics, pharmacokinetics, safety and cardiac uptake (of dezamizumab) following the same intervention in patients with cardiac amyloidosis.

METHODS

Both were uncontrolled open-label studies. After SAP depletion with miridesap, patients received ≤ 6 monthly doses of dezamizumab in the Phase 2 trial (n = 7), ≤ 2 doses of non-radiolabelled dezamizumab plus [89Zr]Zr-dezamizumab (total mass dose of 80 mg at session 1 and 500 mg at session 2) in the immuno-PET study (n = 2). Primary endpoints of the Phase 2 study were changed from baseline to follow-up (at 8 weeks) in left ventricular mass (LVM) by cardiac magnetic resonance imaging and safety. Primary endpoint of the immuno-PET study was [89Zr]Zr-dezamizumab cardiac uptake assessed via PET.

RESULTS

Dezamizumab produced no appreciable or consistent reduction in LVM nor improvement in cardiac function in the Phase 2 study. In the immuno-PET study, measurable cardiac uptake of [89Zr]Zr-dezamizumab, although seen in both patients, was moderate to low. Uptake was notably lower in the patient with higher LVM. Treatment-associated rash with cutaneous small-vessel vasculitis was observed in both studies. Abdominal large-vessel vasculitis after initial dezamizumab dosing (300 mg) occurred in the first patient with immunoglobulin light chain amyloidosis enrolled in the Phase 2 study. Symptom resolution was nearly complete within 24 h of intravenous methylprednisolone and dezamizumab discontinuation; abdominal computed tomography imaging showed vasculitis resolution by 8 weeks.

CONCLUSIONS

Unlike previous observations of visceral amyloid reduction, there was no appreciable evidence of amyloid removal in patients with cardiac amyloidosis in this Phase 2 trial, potentially related to limited cardiac uptake of dezamizumab as demonstrated in the immuno-PET study. The benefit-risk assessment for dezamizumab in cardiac amyloidosis was considered unfavourable after the incidence of large-vessel vasculitis and development for this indication was terminated. Trial registration NCT03044353 (2 February 2017) and NCT03417830 (25 January 2018).

Therapeutic Clearance of Amyloid by Antibodies to Serum Amyloid P Component

BACKGROUND

The amyloid fibril deposits that cause systemic amyloidosis always contain the nonfibrillar normal plasma protein, serum amyloid P component (SAP). The drug (R)-1-[6-[(R)-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid (CPHPC) efficiently depletes SAP from the plasma but leaves some SAP in amyloid deposits that can be specifically targeted by therapeutic IgG anti-SAP antibodies. In murine amyloid A type amyloidosis, the binding of these antibodies to the residual SAP in amyloid deposits activates complement and triggers the rapid clearance of amyloid by macrophage-derived multinucleated giant cells.

METHODS

We conducted an open-label, single-dose-escalation, phase 1 trial involving 15 patients with systemic amyloidosis. After first using CPHPC to deplete circulating SAP, we infused a fully humanized monoclonal IgG1 anti-SAP antibody. Patients with clinical evidence of cardiac involvement were not included for safety reasons. Organ function, inflammatory markers, and amyloid load were monitored.

RESULTS

There were no serious adverse events. Infusion reactions occurred in some of the initial recipients of larger doses of antibody; reactions were reduced by slowing the infusion rate for later patients. At 6 weeks, patients who had received a sufficient dose of antibody in relation to their amyloid load had decreased liver stiffness, as measured with the use of transient elastography. These patients also had improvements in liver function in association with a substantial reduction in hepatic amyloid load, as shown by means of SAP scintigraphy and measurement of extracellular volume by magnetic resonance imaging. A reduction in kidney amyloid load and shrinkage of an amyloid-laden lymph node were also observed.

CONCLUSIONS

Treatment with CPHPC followed by an anti-SAP antibody safely triggered clearance of amyloid deposits from the liver and some other tissues. (Funded by GlaxoSmithKline; ClinicalTrials.gov number, NCT01777243.).

Pentraxin-3 Silencing Suppresses Gastric Cancer-related Inflammation by Inhibiting Chemotactic Migration of Macrophages

BACKGROUND

Chronic inflammation characterized by the recruitment and activation of macrophages has been implicated in the development of gastric cancer.

MATERIALS AND METHODS

Expression of the long form of pentraxin-3 (PTX3) in gastric cancer cells was examined by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. The migratory capacity of gastric cancer cells and chemotaxis of macrophages by PTX3 were assessed by wound-healing and transwell assays. PTX3 silencing using small interfering RNA (siRNA) was performed to confirm PTX3-mediated effects.

RESULTS

We demonstrated that PTX3 expression was elevated in human advanced gastric cancer tissues with increased infiltration of CD11b+ macrophages. Tumor necrosis factor-alpha increased PTX3 expression via nuclear factor-kappa B activation in human gastric cancer cells. PTX3 promoted the tumor cell migratory potential, the recruitment of macrophages and their subsequent binding to gastric cancer cells. These effects were suppressed by PTX3 knockdown using siRNA.

CONCLUSION

Our findings suggest that gastric cancer-derived PTX3 promotes macrophage recruitment, which may contribute to gastric cancer-related inflammation.

Atorvastatin reduces long pentraxin 3 expression in vascular cells by inhibiting protein geranylgeranylation

BACKGROUND

The long pentraxin PTX3 is an acute-phase multi-functional protein that might play both positive and detrimental effects under different pathophysiological conditions. We previously showed that statins down-regulate the release of PTX3 in human endothelial cells (ECs). The present study investigated the mechanism mediating this effect, its occurrence in other cells involved in atherogenesis, and whether it takes place in experimental atherosclerosis.

METHODS AND RESULTS

We found that atorvastatin (1-5 μmol/L) decreased the production and release of PTX3 in human ECs through a post-transcriptional effect. Co-incubation with mevalonate or geranylgeranyl pyrophosphate prevented this effect. Direct blockade of geranylgeranyl transferase I by GGTI-286, treatment with the Rac inhibitor NSC23766 or silencing of the geranylgeranylated GTPase Rac2 by siRNA closely mimicked the action of atorvastatin. In contrast, inactivation of other geranylgeranylated proteins such as RhoA, RhoB, and RhoC or Rac1 did not affect PTX3 release. In addition, we found that atorvastatin also decreased PTX3 secretion in aortic SMCs through a mechanism likely dependent on protein geranylgeranylation, while no effect was observed in monocytes. Finally, we found that atherosclerotic lesions from cholesterol-fed rabbits treated with atorvastatin (2.5 mg/kg/day for 8 weeks) showed less immunoreactive PTX3 than lesions from control animals.

CONCLUSIONS

Results suggest that statins may interfere with PTX3 expression in vascular cells via inhibition of protein geranylgeranylation. Since PTX3 is increasingly regarded as an important mediator of the inflammatory response underlying atherosclerosis and its complications, these results highlight the need for further studies of the role of PTX3 and its potential pharmacological modulation in cardiovascular disease.

Neonatal levels of acute phase proteins and later risk of non-affective psychosis

Mounting evidence suggests that immune disturbances in early life may be implicated in the etiology of non-affective psychoses. Our aim was to assess the levels of neonatal acute phase proteins (APPs), central to innate immune function as well as central nervous system development, in neonatal dried blood spots and their association with later risk of non-affective psychoses. This case-control study included 196 individuals with a verified register-based diagnosis of non-affective psychosis and 502 controls matched on age, sex and hospital of birth. Concentrations of nine different APPs were measured in eluates from dried blood spots using a bead-based multiplex assay. Odds ratios (OR) for non-affective psychoses were calculated for log(2)-transformed (continuous) as well as tertiles of APP concentrations. In continuous analysis, higher concentrations of two APPs, tissue plasminogen activator (tPA; OR: 0.90, 95% confidence interval (CI): 0.85-0.96) and serum amyloid P (SAP; OR: 0.88, 95% CI: 0.78-0.99) were protective in terms of risk of non-affective psychosis. These relationships were not affected by the addition of covariates relevant to maternal health, pregnancy and delivery to the model. Tertile analysis confirmed a protective relationship for higher levels of tPA and SAP, as well as for procalcitonin (highest tertile OR: 0.54, 95% CI:0.32-0.91). Our results suggest that persons who develop non-affective psychoses have lower levels of certain APPs at the time of birth. These differences may render individuals more susceptible to infectious diseases or cause deficiencies in pathways critical for neurodevelopment.

Geranylgeranyl-pyrophosphate regulates secretion of pentraxin 3 and monocyte chemoattractant protein-1 from rheumatoid fibroblast-like synoviocytes in distinct manners

OBJECTIVES

We previously reported that 10 mg/day of simvastatin significantly reduced clinical scores of rheumatoid arthritis (RA) in active RA patients with hypercholesterolemia. In this study, we have investigated the mechanism by which simvastatin inhibits the production of the mediators of inflammation, such as pentraxin 3 (PTX3) and monocyte chemoattractant protein-1 (MCP-1), from fibroblast-like synoviocytes (FLS) derived from patients with RA.

METHODS

FLS from RA patients were cultured with 0-10 μM simvastatin for 24 h. ELISA and real-time PCR were used to quantitate the protein level and the mRNA level of PTX3 and MCP-1, respectively.

RESULTS

Simvastatin both reduced the secretion of PTX3 and MCP-1 in FLS cultures and inhibited their mRNA expression in these cells. The effects of simvastatin were all completely reversed in the presence of mevalonic acid or geranylgeranylpyrophosphate, but not in the presence of farnesyl-pyrophosphate. The geranylgeranyl transferase inhibitor GGTI-298 and the Rho kinase inhibitor Y-27632 inhibited the production of PTX3 but not of MCP-1.

CONCLUSIONS

Although simvastatin inhibited the production of PTX3 and MCP-1 in RA FLS, the mechanisms were quite different. It inhibits PTX3 production in a Rho-dependent manner but MCP-1 production in a Rho-independent manner. These results shed light on novel aspects of the anti-inflammatory mechanisms of simvastatin and may prove its important role in the treatment of rheumatic diseases.

Molecular mechanisms of fibrillogenesis and the protective role of amyloid P component: two possible avenues for therapy

Amyloid deposits regress when the supply of fibril precursor proteins is sufficiently reduced, indicating that amyloid fibrils are degradable in vivo. Serum amyloid P component (SAP), a universal constituent of amyloid deposits, efficiently protects amyloid fibrils from proteolysis in vitro, and may contribute to persistence of amyloid in vivo. Drugs that prevent binding of SAP to amyloid fibrils in vivo should therefore promote regression of amyloid and we are actively seeking such agents. A complementary strategy is identification of critical molecular processes in fibrillogenesis as targets for pharmacological intervention. All amyloidogenic variants of apolipoprotein AI contain an additional positive charge in the N-terminal fibrillogenic region of the protein. This is unlikely to be a coincidence and should be informative about amyloidogenesis by this protein. The two amyloidogenic variants of human lysozyme, caused by the first natural mutations found in its gene, provide a particularly powerful model system because both the crystal structure and folding pathways of wild-type lysozyme are so well characterized. The amyloidogenic variant lysozymes have similar 3D crystal structures to the wild type, but are notably less thermostable. They unfold on heating, lose enzymic activity, and aggregate to form amyloid fibrils in vitro.

Ligand-assisted aggregation of proteins. Dimerization of serum amyloid P component by bivalent ligands

A comprehensive series of solution and crystallographic studies reveal how simple, achiral, bivalent ligands of the cyclic pyruvate of glycerol promote face-to-face complex formation of the pentraxin, serum amyloid P component (SAP) into decamers. SAP, a protein of the human innate immune system, is universally present in amyloids, including cerebral amyloid deposits found in the brain of Alzheimer disease patients. Removal of SAP through a specific aggregation mechanism mediated by multivalent ligands appears to provide therapeutic benefit in the progression of this disease. Crystallographic studies reveal that in our novel series of ligands only the methyl and carboxylate moieties of the pyruvate ketal directly interact with the protein, but the geometric constraints imposed by the tether dictate which of two chair conformations are adopted by the pyruvate dioxane ring. Solution studies, as interpreted through a simple thermodynamic model, account for the distribution of pentameric and decameric bound states at different ligand concentrations and indicate that differences in the flexibility of the tether determine the geometry and stability of the specific aggregates formed between SAP and two different bivalent ligands. The factors affecting the design of ligands promoting face-to-face protein dimerization as well as potential biological implications are discussed.

Glycosaminoglycans inhibit neurodegenerative effects of serum amyloid P component in vitro

Serum amyloid P component, a member of pentraxin serum protein family, has been suggested to contribute to the progression of neurodegeneration including Alzheimer's disease by binding to beta-amyloid fibrils leading to an increased stability of the deposits against proteolytic degradation and by inducing neuronal apoptosis. Here, we show that glycosaminoglycans inhibit both the serum amyloid P component-beta-amyloid interaction and the neurotoxic effect of serum amyloid P component. These effects correlate with the structure of glycosaminoglycans and show different structure-activity relationship in the case of the two different effects. While the efficacy of the inhibition on the serum amyloid P component-induced cell death increases with the uronic acid content, the inhibitory activity on the serum amyloid P component-beta-amyloid interaction decreases with the increasing uronic acid content of the glycosaminoglycans. The inhibitory effect of glycosaminoglycans on the interaction between the first component of the complement cascade (C1q) and beta-amyloid shows a similar structure-activity relationship as on the serum amyloid P component-beta-amyloid interaction. This suggests that glycosaminoglycans interfere with the binding site on beta-amyloid for serum amyloid P component and C1q. The functional consequence of this binding has been demonstrated by heparin which promotes the proteolysis of beta-amyloid in vitro in the presence of serum amyloid P component. Our results suggest that glycosaminoglycans might have therapeutical potential on the neurodegeneration reducing its progress.

Targeted pharmacological depletion of serum amyloid P component for treatment of human amyloidosis

The normal plasma protein serum amyloid P component (SAP) binds to fibrils in all types of amyloid deposits, and contributes to the pathogenesis of amyloidosis. In order to intervene in this process we have developed a drug, R-1-[6-[R-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid, that is a competitive inhibitor of SAP binding to amyloid fibrils. This palindromic compound also crosslinks and dimerizes SAP molecules, leading to their very rapid clearance by the liver, and thus produces a marked depletion of circulating human SAP. This mechanism of drug action potently removes SAP from human amyloid deposits in the tissues and may provide a new therapeutic approach to both systemic amyloidosis and diseases associated with local amyloid, including Alzheimer's disease and type 2 diabetes.

Serum amyloid P-component-induced colony-stimulating factors production by macrophages

Purified mouse serum amyloid P-component (SAP; 0.5-50 microg/kg), injected intravenously into Swiss mice, induced the production of serum colony-stimulating factors (CSFs); the maximum induction was observed at 10.0 microg/kg. Further, in vitro purified mouse SAP (0.1-50 microg/ml) stimulated the mouse elicited peritoneal macrophages to elaborate CSFs in the conditioned medium (CM); 5.0 microg/ml SAP appeared to be the optimum. Both in vivo and in vitro the maximum production of CSFs occurred 6 h after initiation of stimulation, and returned to the background levels by 48 h. Mannose 6-P, mannose 1-P and mannose, and not other sugars inhibited the SAP-induced production of CSFs by macrophages which suggests that SAP interaction with macrophages was mediated by specific glycoprotein-receptors. A neutralizing (100%) concentration of rabbit antimouse interleukin (IL)-1 polyclonal antibody had no effect on the SAP-induced CSF production, indicating that it would be IL-1-independent. SAP-induced CSFs, both in serum and CM, were functionally similar as they supported the formation of granulocyte (G), macrophage (M) and GM colonies in similar proportions. The production of CSFs appeared to be lipopolysaccharide (LPS)-independent as it was not inhibited by polymyxin B sulfate (25.0 microg/ml), and heat-inactivated (80 degrees C, 1 h, pH 7.0) SAP did not induce the production of CSFs. The CSFs were produced de novo because cycloheximide (50.0 microg/ml) completely inhibited their production. These results demonstrate that purified mouse SAP, in a dose-dependent manner, can induce the production of serum CSFs in mice, and can induce LPS-independent de novo production of CSFs by elicited macrophages in vitro.

A synthetic lipopolysaccharide-binding peptide based on amino acids 27-39 of serum amyloid P component inhibits lipopolysaccharide-induced responses in human blood

LPS-binding proteins in plasma play an important role in modifying LPS toxicity. Significant properties have already been attributed to the LPS-binding protein (LBP). It accelerates LPS toxicity as well as incorporation into high-density lipoproteins, leading to neutralization of LPS in serum. A search for other LPS-binding components in serum, using LPS-coated magnetic beads, revealed a new LPS-binding protein. N-terminal microsequencing identified this protein as serum amyloid P component (SAP). Purified SAP bound to smooth and rough types of LPS via the lipid A part. SAP inhibited the binding of FITC-labeled ReLPS (LPS from Salmonella minnesota strain R595) to human monocytes and the ReLPS-induced priming of the oxidative burst of human neutrophils only in the presence of low concentrations of LBP. In search for the LPS binding site of SAP, we found that pep27-39, a 13-mer peptide consisting of amino acids 27-39 of SAP, competitively inhibited the binding of LPS to SAP. In addition, pep27-39 significantly inhibited ReLPS-induced responses in phagocytes in the presence of serum, as well as in human whole blood. Carboxamidomethylated pep27-39 showed an even more pronounced reduction of the ReLPS-induced priming of phagocytes in human blood. Performing gel filtration of FITC-labeled ReLPS incubated with soluble CD14, we showed that SAP could not prevent binding of LPS to soluble CD14, in contrast to pep27-39. The ability of pep27-39 to antagonize specifically the effects of LPS in the complex environment of human blood suggests that pep27-39 may be a novel therapeutic agent in the treatment of gram-negative sepsis.

Interferon-gamma inhibits expression of the long pentraxin PTX3 in human monocytes

PTX3 is a prototypic long pentraxin expressed by various cell types, most prominently monocytes and endothelial cells, in response to interleukin-1 (IL-1), tumor necrosis factor (TNF) and bacterial products. In the present report, we show that interferon-gamma (IFN-gamma) inhibits the expression of the PTX3 gene induced by exposure to IL-1, TNF or lipopolysaccharide in human monocytes. This effect is dose dependent and observable when IFN-gamma is added from 24 h before up to 3 h after the addition of IL-1. While the time course of the IL-1-induced PTX3 mRNA expression is not affected, IFN-gamma reduces the stability of the PTX3 mRNA as well as its transcription. The inhibition of PTX3 expression is restricted to monocytes in that no inhibition occurs in cytokine-stimulated fibroblasts and endothelial cells. Under the same conditions, as expected, IFN-gamma augmented monocyte chemotactic protein-1 expression in the same cell preparations. PTX3 protein secretion by activated monocytes is also suppressed by exposure to IFN-gamma. Altogether, these data identify a negative pathway of regulation mediated by IFN-gamma, which may occur under inflammatory conditions.

Congo red inhibits proteoglycan and serum amyloid P binding to amyloid beta fibrils

Various data suggest that Alzheimer's disease results from the accumulation of amyloid beta (A beta) peptide fibrils and the consequent formation of senile plaques in the cognitive regions of the brain. One approach to lowering senile plaque burden in Alzheimer's disease brain is to identify compounds that will increase the degradation of existing amyloid fibrils. Previous studies have shown that proteoglycans and serum amyloid P (SAP), molecules that localize to senile plaques, bind to A beta fibrils and protect the amyloid peptide from proteolytic breakdown. Therefore, molecules that prevent the binding of SAP and/or proteoglycans to fibrillar A beta might increase plaque degradation and prove useful in the treatment of Alzheimer's disease. The nature of SAP and proteoglycan binding to A beta is defined further in the present study. SAP binds to both fibrillar and nonfibrillar forms of A beta. However, only the former is rendered resistant to proteolysis after SAP association. It is interesting that both SAP and proteoglycan binding to A beta fibrils can be inhibited by glycosaminoglycans and Congo red. Unexpectedly, Congo red protects fibrillar A beta from breakdown, suggesting that this compound and other structurally related molecules are unlikely to be suitable for use in the treatment of Alzheimer's disease.

Calcium-enhanced aggregation of serum amyloid P component and its inhibition by the ligands heparin and heparan sulphate. An electron microscopic and immunoelectrophoretic study

Serum amyloid P component (SAP) is a pentraxin found in the circulation and in all forms of amyloid deposits. Its physiological and pathophysiological functions are largely unknown. Electron microscopy showed purified human SAP to consist of double pentameric discs compatible with the results of size chromatography. The formation of double pentamers did not require calcium ions. The outer diameter of the discs arranged face-to-face was 11.6 nm and the inner diameter 3.2 nm. The thickness of single and double pentamers was 4.1 and 8.7 nm, respectively. Quadruple pentamers were occasionally seen. The self-aggregation of human SAP molecules was investigated in the presence and absence of calcium ions at different concentrations. In calcium-free solutions few and mostly small SAP aggregates were seen. After addition of calcium at increasing concentration the aggregates grew in size and crystalline-like structures were formed already at 2 mM calcium. At 25 mM calcium, large aggregates with a crystalline array occasionally exhibiting cylinders predominated. Binding of the ligands heparin and heparan sulphate to SAP completely abolished the calcium-enhanced aggregation, but the distribution of the SAP molecules was affected, resulting in strands or groups of adjacent molecules. The electrophoretic mobility of SAP was moreover significantly altered after its calcium-dependent reaction with these ligands. We conclude that purified SAP has a tendency to double pentamer formation and self-aggregation also in the absence of calcium ions. However, aggregation is greatly enhanced even at low concentrations (2 mM) of calcium. SAP's tendency to self-aggregation is abolished after its binding to heparin or heparin sulphate. Furthermore, our TEM studies indicate that purified human SAP freed of its natural ligands has the double pentameric form, whereas the electrophoretic investigations suggest that SAP's interaction with low-molecular-weight natural ligands in serum prevents homodimerization and self-aggregation.

Binding specificity of mouse serum amyloid P-component for fibronectin

Binding between purified mouse serum amyloid P-component (SAP) and plasma fibronectin (Fn) occurred when either one of the proteins was immobilized by specific antibody and the second protein was offered in a soluble form. Binding of Fn to immobilized SAP was cooperative and saturable at a molar ratio of SAP/Fn = 7.1. The molar ratio at saturation was 3.7 for SAP/Fn when SAP was allowed to bind to immobilized Fn. The binding required 2 to 3mM amounts of Ca++. The binding of SAP to Fn was selectively inhibited by a monoclonal antibody specific for the mid-molecule region of Fn, by soluble gelatin, and by heparin in the presence of 3mM Ca++. We conclude that the SAP binding site was localized at the mid-molecule region of Fn that includes the adjacent gelatin-binding domain and the heparin-I binding domain.