Anti-HLA antibodies with complementary and synergistic interaction geometries promote classical complement activation on platelets.

High titers of HLA antibodies are associated with platelet refractoriness, causing poor platelet increments after transfusions in a subset of patients with HLA antibodies. Currently, we do not know the biological mechanisms that explain the variability in clinical responses in HLA alloimmunized patients receiving platelet transfusions. Previously we showed that a subset of anti-HLA IgG-antibodies induces FcγRIIa-dependent platelet activation and enhanced phagocytosis. Here, we investigated whether anti-HLA IgG can induce complement activation on platelets. We found that a subset of anti-HLA IgG induced complement activation via the classical pathway, causing C4b and C3b deposition and formation of the membrane-attack complex. This resulted in permeabilization of platelet membranes and increased calcium influx. Complement activation also caused enhanced α-granule release, as measured by CD62P surface exposure. Blocking studies revealed that platelet activation was caused by FcγRIIa-dependent signaling as well as HLA antibody induced complement activation. Synergistic complement activation employing combinations of monoclonal IgGs suggested that assembly of oligomeric IgG complexes strongly promoted complement activation through binding of IgGs to different antigenic determinants on HLA. In agreement with this, we observed that preventing anti-HLA-IgG hexamer formation using an IgG-Fc:Fc blocking peptide, completely inhibited C3b and C4b deposition. Our results show that HLA antibodies can induce complement activation on platelets including membrane attack complex formation, pore formation and calcium influx. We propose that these events can contribute to fast platelet clearance in vivo in patients refractory to platelet transfusions with HLA alloantibodies, who may benefit from functional-platelet matching and treatment with complement inhibitors.

Nonclinical Development of ANX005: A Humanized Anti-C1q Antibody for Treatment of Autoimmune and Neurodegenerative Diseases.

ANX005 is a humanized immunoglobulin G4 recombinant antibody against C1q that inhibits its function as the initiating molecule of the classical complement cascade. The safety and tolerability of ANX005 are currently being evaluated in a phase I trial in healthy volunteers ( www.clinicaltrials.gov Identifier: NCT03010046). Inhibition of C1q can be applied therapeutically in a broad spectrum of diseases, including acute antibody-mediated autoimmune disease, such as Guillain-Barré syndrome (GBS), and in chronic diseases of the central nervous system involving complement-mediated neurodegeneration, such as Alzheimer's disease (AD). To support the clinical development of ANX005, several studies were conducted to assess the pharmacology, pharmacokinetics, and potential toxicity of ANX005. ANX-M1, the murine precursor of ANX005, functionally inhibits the classical complement cascade both in vitro and in vivo, to protect against disease pathology in mouse models of GBS and AD. Toxicology studies with ANX005, itself, showed that intravenous administration once weekly for 4 weeks was well tolerated in rats and monkeys, with no treatment-related adverse findings. Serum levels of ANX005 in monkeys correlate with a reduction in free C1q levels both in the serum and in the cerebrospinal fluid. In summary, ANX005 has shown proof of concept in in vitro and in vivo nonclinical pharmacology models, with no toxicity in the 4-week repeat-dose studies in rats and monkeys. The no observed adverse effect level was 200 mg/kg/dose, which is 200-fold higher than the first-in-human starting dose of 1 mg/kg in healthy volunteers.

One new cycloartane triterpene glycoside from Beesia calthaefolia.

One new cycloartane triterpene glycoside (1) was isolated from the whole plant of Beesia calthaefolia. Its structure was elucidated on the basis of extensive spectroscopic data analysis. Its inhibitory effect was measured by the classical pathway of the complement system, and compared with those of known related cycloartane glycosides 2 and 3, previously isolated by us from the same plant. Compounds 1 and 2 exhibited inhibitory activity of complement system with IC50 of 395.3 and 214 µM, respectively. The results suggested that OH at C-12, C-18 and C-15 along with the polarity could affect the inhibitory activity.

Flavonol glycosides and other phenolic compounds from Viola tianshanica and their anti-complement activities.

CONTEXT: Viola tianshanica Maxim. (Violaceae) is a perennial herb distributed in Central Asia, especially in the Xinjiang Uygur Autonomous Region (XUAR) of China. Preliminary study showed that the ethanol extract of the herb exhibited the anti-complement activity against the classical pathway, but the active components responsible for this capacity remain unknown and are yet to be studied. OBJECTIVE: The objective of this study was the isolation and identification of the anti-complement constituents of V. tianshanica. MATERIALS AND METHODS: The ethyl acetate and n-butanol fractions from the ethanol extract of V. tianshanica were purified. The structures of the isolates were identified by spectroscopic methods, and comparing their spectral data with those reported in the literature. All the isolates (0.02-2.50 mg/mL) were evaluated for their anti-complement activity against the classical and alternative pathways. RESULTS: Twenty-one phenolic compounds including 15 flavonol O-glycosides (1-15), one flavone 6,8-di-C-glycoside (16), one flavone aglycone (17), and four phenolic acid derivatives (18-21) were isolated and identified. Bioassay showed that 11 compounds inhibited the classical pathway and the alternative pathway with CH50 and AP50 values of 0.113-1.210 mM and 0.120-1.579 mM, respectively. Preliminary mechanistic study using complement-depleted sera demonstrated that 1 acted on C1q, C2, C4, and C9 components, 16 on C1q, C4, and C5, and 21 on C1q, C3, C4, and C9. CONCLUSION: All isolated compounds except 1 and 10 were reported for the first time from V. tianshanica. Compound 16 is the first flavone C-glycoside isolated from the herb. Flavonol O-glycosides and phenolic acids contributed the anti-complement activity of the herb.

Complement blockade with a C1 esterase inhibitor in paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, clonal, hematopoietic stem cell disorder that manifests with a complement-mediated hemolytic anemia, bone marrow failure, and a propensity for thrombosis. These patients experience both intra- and extravascular hemolysis in the context of underlying complement activation. Currently eculizumab effectively blocks the intravascular hemolysis PNH. There remains an unmet clinical need for a complement inhibitor with activity early in the complement cascade to block complement at the classical and alternative pathways. C1 esterase inhibitor (C1INH) is an endogenous human plasma protein that has broad inhibitory activity in the complement pathway through inhibition of the classical pathway by binding C1r and C1s and inhibits the mannose-binding lectin-associated serine proteases in the lectin pathway. In this study, we show that commercially available plasma derived C1INH prevents lysis induced by the alternative complement pathway of PNH erythrocytes in human serum. Importantly, C1INH was able to block the accumulation of C3 degradation products on CD55 deficient erythrocytes from PNH patient on eculizumab therapy. This could suggest a role for inhibition of earlier phases of the complement cascade than that currently inhibited by eculizumab for incomplete or nonresponders to that therapy.

Anticomplementary activity of oleanane-type triterpenes from the roots of Aceriphyllum rossii.

To gain a better understanding of the anticomplement activity of triterpenoids, the complement activity of five unusual oleanane-type triterpenoids, bearing a carboxyl group at the C-29 position, were estimated against the classical pathway of a complementary system. The five triterpenoids were obtained from the roots of Aceriphyllum rossii (Saxifragaceae), and were determined to be aceriphyllic acids B-E (1-4) and K (5). Of the isolated compounds, compounds 1, 2 and 5 showed anticomplement activities, with IC(50) values of 328.4, 77.5 and 348.6 µM, respectively, whereas, compounds 3 and 4 were inactive. This showed that a carboxyl group at the C-23 position and an α-configuration of a hydroxyl group at the C-3 position in the olean-29-carboxylic acid triterpenoids seemed to play an important role in the anticomplement activity of human serum against erythrocytes.

Phenylethanoid glycosides from Monochasma savatieri and their anticomplement activity through the classical pathway.

Five new phenylethanoid glycosides, savasides A-E (1-5), along with 6 known ones were isolated from the whole plant of Monochasma savatieri Franch. The structures of 1-5 were elucidated on the basis of spectroscopic data analysis. Moreover, all isolated compounds were evaluated for anticomplement activity through the classical pathway.

Cycloartane-type triterpene glycosides from the rhizomes of Cimicifuga heracleifolia and their anticomplementary activity.

Seven known triterpene glycosides, 23-O-acetylshengmanol 3-O-α-L-arabinopyranoside (1), 23-O-acetylshengmanol 3-O-ß-D-xylopyranoside (2), 24-epi-24-O-acetylhydroshengmanol 3-O-ß-D-xylopyranoside (3), cimiaceroside B (4), (23R,24S)-cimigenol 3-O-ß-D-xylopyranoside (5), (23R,24R)-25-O-acetylcimigenol 3-O-ß-D-xylopyranoside (6) and (23R,24S)-25-O-anhydrocimigenol 3-O-ß-D-xylopyranoside (7) were isolated from the rhizomes of Cimicifuga heracleifolia. Their chemical structures were determined on the basis of spectroscopic analyses including 2D NMR. All isolates were investigated for their inhibitory effects on the classical pathway of the complement system. Among them, compound 6 showed strong inhibitory activity with an IC50 value of 7.7 µM while compound 3 was moderately active with an IC50 value of 195.6 µM.

Inhibitory effects of three oleanolic acid glycosides from Achyranthes japonica on the complement classical pathway.

The present study evaluated the anticomplement effects of isolated compounds from Achyranthes japonica in the classical pathway of the complement system. Using column chromatography, three compounds: achyranthoside C dimethyl ester, achyranthoside C butyl dimethyl ester, and achyranthoside E dimethyl ester were isolated and evaluated for in vitro anticomplement activity. Achyranthoside C dimethyl ester showed the most potent inhibitory activity against the complement system, with 50% inhibitory concentrations (IC(50)) values of 26.2 µg/mL. This is the first report of anticomplement activity of isolated compounds from A. japonica.

Anticomplement activity of organic solvent extracts from Korea local Amarantaceae spp.

The study evaluated the anticomplement activity from various solvent extracts of nine Amarantaceae plants (Achyranthes japonica (Miq.) Nakai, Amaranthus mangostanus L., Amaranthus retroflexus L., Amaranthus spinosus L., Celosia argentea var. spicata., Amaranthus lividus L., Celosia cristata L., Amaranthus viridis L., Gomphrena globosa L.) from South Korea on the classical pathway. We have evaluated various organic solvent extract from nine Amarantaceae plants with regard to its anticomplement activity on the classical pathway. Achyranthes japonica chloroform extracts showed inhibitory activity against complement system with 50% inhibitory concentrations (IC(50)) value of 73.1µg/ml. This is the first report of anticomplement activity from Amarantaceae plants.

Inhibitory effects of organic solvent extracts from Korean local plants on the complement classical pathway.

The study evaluated the anticomplement effects from organic solvent extracts of five Compositae plants (Ligularia fischeri (Ledeb.) Turez, Ligularia taquetii (H.Lev. & Vaniot) Nakai, Ainsliaea acerifolia Sch.Bip, Aster scaber Thunb, Aster koraiensis Nakai, Synurus deltoides Aiton) from South Korea on the classical pathway complement system. We have evaluated organic solvent extracts from five Compositae with regard to its anticomplement activity. Chloroform extracts from L. taquetii showed inhibitory activity against complement system with 50% inhibitory concentrations (IC50) values of 73.2 µg/mL. This is the first report of anticomplement activity from L. taquetii.

Anticomplement activity of various solvent extracts from Korea local Artemisia spp.

The study evaluated the anticomplement activity from various solvent extracts of eight Artemisia plants (Artemisia capillaris Thunb., Artemisia fukudo Makino., Artemisia japonica Thunb., Artemisia montana (Nakai) Pamp., Artemisia keiskeana Miq., Artemisia rubripes Nakai., Artemisia stolonifera (Maxim.) Kom., and Artemisia sylvatica Max.) from South Korea on the classical pathway (CP). We have evaluated various organic solvent extract from eight Artemisia plants with regard to its anticomplement activity on the CP. A. rubripes and A. montana chloroform extracts showed inhibitory activity against complement system with 50% inhibitory concentrations (IC50) values of 54.3 and 64.2 µg/mL. This is the first report of anticomplement activity from Artemisia plants.

Anticomplement activity of isolated compounds from Artemisia montana.

The study evaluated the anticomplement activity from isolated compounds from Artemisia montana (Nakai) Pamp. from South Korea on the classical pathway. In a previous work, A. montana (Nakai) Pamp. chloroform extracts showed inhibitory activity against complement system. The chromatographic separation of a chloroform chloride extract of A. montana (Nakai) Pamp. led to the isolation of four compounds. Their structures were characterized to be ezoartemin, yamayomoginin, ezomontanin and 11,13-dihydroezomontanin by spectroscopic data. This is the first report of anticomplement activity of isolated compounds from A. montana (Nakai) Pamp.

Inhibition effects of isolated compounds from Artemisia rubripes Nakai of the classical pathway on the complement system.

The study evaluated the anticomplement activity from isolated compounds from Artemisia rubripes Nakai from South Korea on the classical pathway. In the previous works, Artemisia rubripes chloroform extracts showed inhibitory activity against complement system. The chromatographic separation of a chloroform chloride extract of Artemisia rubripes led to the isolation of three compounds. Their structures were characterized to be scopoletin (1), 11,(13)-triene-6,12-olide (2), and 1ß,6α-dihydroxy-4(15)-eudesmene (3) by spectroscopic data. This is the first report of anticomplement activity of isolated compounds from Artemisia rubripes.

Isolated compounds from Sorghum bicolor L. inhibit the classical pathway of the complement.

The present study evaluated the anticomplement effects from isolated compounds of Sorghum bicolor in classical pathway complement system. Using column chromatograph, three compounds; Sorgoleone-362 (1), Sorgoleone-360 (2) and Sorgoleone-386 (3) were isolated and evaluated for in vitro anticomplement activity. Sorgoleone-386 showed inhibitory activity against complement system with 50% inhibitory concentrations (IC(50)) values of 148.3µg/ml. This is the first report of anticomplement activity of isolated compounds from Sorghum bicolor.

Anti-complementary ginsenosides isolated from processed ginseng.

As part of an ongoing search for immunomodulatory components aimed at the anti-complementary effect, ginsenosides isolated from processed ginseng were found to have inhibitory activity on complement activation through classical pathways. Activity-guided fractionation was used to isolate four ginsenosides, namely ginsenoside Rg6, F4, Rk3, and Rh4. Ginsenoside Rk3 and Rh4 had a 3 fold higher inhibition activity than rosmarinic acid which was used as a positive control while ginsenoside Rg6 and F4 showed only mild effects similar to that of the positive control. The results suggest that the activity of the corresponding ginsenosides may be increased by the glycosyl moiety at the C6 position rather than the double bond conformation at C20, and ginsenoside Rk3 and Rh4 could have a role in treating inflammatory diseases.

Anticomplement activity of polyacetylenes from leaves of Dendropanax morbifera Leveille.

The present study evaluated the anticomplement effect of polyacetylenes from Dendropanax morbifera (Araliaceae) in the classical pathway complement system. The leaves of D. morbifera were evaluated with regard to its anticomplement activity, and its active principles identified following activity-guided isolation. An aqueous CCl(4) fraction of the leaves of D. morbifera exhibited significant anticomplement activity on the classical pathway complement system, which was expressed as total hemolytic activity. Three polyacetylenes isolated from the leaves of D. morbifera, namely (3S)-falcarinol (1), (3S,8S)-falcarindiol (2) and (3S)-diynene (3). Compounds 1, 2 and 3 showed inhibitory activity against complement system with 50% inhibitory concentrations (IC(50)) values of 87.3 µM, 15.2 µM and 39.8 µM. Among the compounds tested, 2 showed the most potent anticomplement activity (IC(50), 15.2 µM).

Inhibitory effects of isolated compounds from black coloured rice bran on the complement classical pathway.

The present study evaluated the anticomplement effects of isolated compounds from black coloured rice bran in the classical pathway of the complement system. Using column chromatography, three compounds: oryzafuran, quercetin and protocatechuic acid, were isolated and evaluated for in vitro anticomplement activity. Oryzafuran showed the most potent inhibitory activity against the complement system, with 50% inhibitory concentration (IC50) values of 126.2 µg/mL. This is the first report of anticomplement activity of isolated compounds from black coloured rice bran.

Inhibition effects of the classical pathway complement of three Sorghum bicolor from South Korea.

The present study evaluated the anti-complement effects from organic solvent extracts of three varieties (Hwanggeumchal Sorghum, Chal Sorghum, and Heuin Sorghum) from Sorghum bicolor in classical pathway complement system. We have evaluated organic solvent extract from Sorghum bicolor varieties with regard to its anti-complement activity. Chal Sorghum ethyl acetate extract showed inhibitory activity against complement system with 50% inhibitory concentrations (IC(50)) values of 38.7 µg/mL. This is the first report of anti-complement activity from Sorghum bicolor varieties.

Inhibition effects of the classical pathway complement of isolated compounds from Quercus glauca.

Species of the Quercus species is an evergreen broadleaf tree found not only in Korea but also in China, Taiwan, and Japan. Quercus species is the most commonly occurring plant among the 50 native species of the family Fagaceae in Korea, China, and Taiwan. Quercus species have been used for diarrhea, dysentery, dermatitis, and hemorrhagia in Korean folk medicine. The present study evaluated the anticomplement effect of constituents from Quercus species (Fagaceae) in classical pathway complement system. We have evaluated leaves of five species of the Quercus genus with regard to its anticomplement activity and have identified its active principles following activity-guided isolation. Bioactivity-guided fractionation of the 80% methanol extracts of the stem barks of Quercus glauca Thunberg has led to the isolation of galloyl derivatives, displaying high anticomplement activity. Four galloyl derivatives isolated from the leaves of Q. glauca, namely 6'-O-galloyl salidroside (1), methyl gallate (2), 1,2,3,6-tetragalloylglucose (3), and 1,2,6-trigalloylglucose (4). 1, 2, 3 and 4 showed inhibitory activity against complement system with 50% inhibitory concentrations (IC(50)) values of 224 µM, 362.4 µM, 32.3 µM, and 138.3 µM. Among the compounds tested, 3 showed the most potent anticomplement activity (IC(50), 32.3 µM). This is the first report of the isolation and anticomplement activity from Q. glauca.