AB0356 THERAPEUTIC DRUG MONITORING: STANDARDIZATION OF PROMONITOR QUICK IFX AND PROMONITOR QUICK ADL POINT OF CARE TESTS WITH WHO INTERNATIONAL STANDARDS FOR THE QUANTIFICATION OF INFLIXIMAB AND ADALIMUMAB IN WHOLE BLOOD AND SERUM

Background

Promonitor Quick IFX and Promonitor Quick ADL are rapid point of care lateral flow tests (LFT) based on a sandwich immunoassay for the quantification of infliximab (IFX) and adalimumab (ADL), respectively, in human whole blood (finger prick or venous) or serum. These tests are to be used as an aid in Therapeutic Drug Monitoring (TDM) of rheumatic and inflammatory bowel disease patients under anti-TNFα therapy. The international standards (IS) developed by World Health Organization (WHO) for IFX and ADL allow harmonization and comparability among different assays.

Objectives

The aim of this study, was to show that Promonitor Quick IFX and Promonitor Quick ADL can measure either reference or biosimilar drugs, as well as to evaluate the agreement of Promonitor Quick IFX and Promonitor Quick ADL tests and the WHO IS.

Methods

Clinical and Laboratory Standards Institute EP10-A3 guidelines were followed to estimate the bias of Promonitor Quick assays when used to quantify IFX or ADL in samples containing the reference drugs, biosimilars or the WHO IS. Briefly, whole blood was spiked with four known concentrations of IFX or ADL, including current clinical decision levels. Ten replicates were measured of each level along two days.

Promonitor Quick IFX was evaluated using the reference drug, SB2 and CT-P13 biosimilars, and the WHO IS (NIBSC 16/170).

Promonitor Quick ADL was evaluated using the reference drug, ABP501 and SB5 biosimilars, and the WHO IS (NIBSC 17/236).

Results were obtained in combination with the automated portable reader PQreader.

Results

Bias was estimated by comparing the observed concentration of drug spiked whole blood samples. Each biosimilar was compared to the reference at the different drug levels tested. Results showed that Promonitor Quick IFX and Promonitor Quick ADL are able to measure equivalently any molecule (see Table 1).

Table 1.Promonitor Quick IFX bias results in whole blood samples. Each molecule was compared to the reference drug.IFX concentration (μg/mL)Bias (%)CT-P13SB2GP1111WHO IS314%3%4%8%79%0%5%15%101%5%6%8%Promonitor Quick ADL bias results in whole blood samples.Each molecule was compared to the reference drug.ADL concentration (μg/mL)Bias (%)ABP501SB5WHO IS317%2%3%513%3%12%82%2%7%10517%2%

Similar results were obtained when serum matrix was used.

The accuracy or closeness of the agreement between the result provided by Promonitor Quick IFX and Promonitor Quick ADL and the true value of the measurand was assessed by measuring the IS developed by the WHO (see Table 1).

Conclusion

Promonitor Quick IFX and Promonitor Quick ADL allow monitoring of patients treated with IFX and ADL, respectively, with just a finger prick sample. Both tests can quantify reference and biosimilar drugs with equivalent results. Moreover, comparable results were obtained with the WHO IS, and thus, demonstrate that Promonitor Quick tests are suited to accurately determine drug levels at the clinical decision points in both whole blood and serum, proving to be an effective and valuable tool in TDM and immediate decision making in the doctor office or hospitals.

Disclosure of Interests

Amagoia Ametzazurra Employee of: Employee of Progenika Biopharma - Grifols, Javier Pascual Employee of: Employee of Progenika Biopharma - Grifols, Lorena Del Rio Employee of: Employee of Progenika Biopharma - Grifols, Ane Urigoitia Employee of: Employee of Progenika Biopharma - Grifols, Daniel Nagore Employee of: Employee of Progenika Biopharma - Grifols, M. Begoña Ruiz-Argüello Employee of: Employee of Progenika Biopharma - Grifols

AB0370 COMPARISON OF A NEW RANDOM-ACCESS SOLUTION FOR THERAPEUTIC DRUG MONITORING OF ADALIMUMAB TO THE REFERENCE ELISA TEST

Background

Despite numerous studies, Therapeutic Drug Monitoring (TDM) of biological therapies is still debated partly motivated by the accessibility to a ready-to-use monotest device capable of delivering accurate results in a timely manner without the burden of sample batching, therefore allowing immediate decision making.

Objectives

We aimed at comparing the new Chorus Promonitor Adalimumab monotest running in the fully automated random-access Chorus TRIO system to the reference ELISA test Promonitor ADL run in a Triturus system.

Methods

Chorus Promonitor Adalimumab (Diesse Diagnostica Danese, Italy) is an immunoassay kit for the automated quantitative detection of adalimumab (ADL) in human serum using a ready-to-use disposable monotest device applied on the Chorus TRIO (Diesse Diagnostica Danese, Italy) instrument, a random-access single test multiparametric system for immuno-colorimetric assays. The new device implements the same specific reagents as in the reference ELISA test Promonitor ADL (Progenika, Spain) run in a Triturus (Grifols, Spain) system, therefore ensuring the same analytical specificity and applicability for patient monitoring previously demonstrated with the predicate ELISA. The new monotest device contains all the reagents necessary to perform the assay, and a lot-specific master curve method is used for calibrating. The comparison was performed in a set of 53 serum samples from patients under ADL therapy that covered the entire drug trough concentrations found in clinical practice (up to 30 ug/mL). Pearson’s correlation, Bland-Altman and Passing-Bablok regression analysis were used to study the association and quantitative comparison between the methods.

Results

Time to first result for the Chorus Promonitor Adalimumab test was 2 hours and 45 min minutes and after this a new result was delivered every 30 seconds. Positive and negative percent agreements between both tests were 100%. A high correlation between both tests was found (coefficient of correlation of 0.959, p<0.01). The Passing-Bablok regression analysis determined an excellent comparability of both data sets with a slope of 1.032 (0.952-1.129) with an intercept of -0.428 (-1.292-0.053).

Figure 1.

Conclusion

The Chorus Promonitor Adalimumab represents the first evolution of the gold-standard Promonitor ELISA technology into a monotest random-access technology that enables quick turnaround time to facilitate TDM for ADL and aid immediate decision making.

Disclosure of Interests

None declared

AB0369 CORRELATION OF THE FIRST LATERAL FLOW-BASED POINT OF CARE TEST TO QUANTIFY INFLIXIMAB AND ANTI-INFLIXIMAB ANTIBODIES IN A FINGER PRICK SAMPLE WITH THE REFERENCE ELISA TECHNIQUE

Background

Current techniques to monitor clinical response may require several days and centralised facilities, which may cause delays in effective therapeutic decisions. Therefore, the use of a rapid decentralized test will facilitate patient management and improve patient care.

Objectives

The goal of this study was to validate the use of capillary blood in a real point-of-care (POC) setting for rheumatic patients under infliximab treatment by using Promonitor Quick lateral flow (LF) tests. Results were compared to the Promonitor ELISA reference technique in serum samples used by centralised laboratories.

Methods

A prospective, observational study was designed to evaluate the performance of a rapid LF test (Promonitor Quick IFX, Progenika, Spain). 160 infliximab treated rheumatology consecutive patients (400 samples) were recruited in two hospitals in Galicia, Spain. Prior to the infusion, a finger prick sample was obtained and analysed. Anti-infliximab antibodies were also determined with Promonitor Quick ANTI-IFX1-4. Results were read with the automated portable PQreader instrument. Additionally, a serum sample was collected for subsequent comparative analysis with either LF or ELISA tests.

Qualitative (positive (PPA) and negative (NPA) agreements) and quantitative (Pearson correlation and bias) performance of the LF test was compared to ELISA, as well as between different specimens following CLSI EP09-A3.

Results

Overall agreement between Promonitor Quick IFX finger prick and ELISA test was 91% (88% PPA; 100% NPA). The quantitative comparison showed a good correlation (Pearson correlation coefficient: 0.85 and observed bias: 25%) (Table 1).

Table 1.Performance results: infliximab drugQualitative ComparisonN*PPANPAoverallPOC finger prick vs ELISA27488%100%91%POC serum vs ELISA28198%100%98%Quantitative ComparisonN*Pearson correlationBiasPOC finger prick vs ELISA1650.8525%POC serum vs ELISA1810.916%*Only samples in the common measurement range for both methods considered.Performance results: anti-infliximab anti-drug antibodiesQualitative ComparisonN*PPANPAoverallPOC finger prick visual vs. PQreader396100%99%99%POC serum visual vs PQreader398100%100%100%POC finger prick PQreader vs ELISA39390%99%98%POC serum PQreader vs ELISA39589%100%99%

Similar results were also observed when serum was used with either the LF or the ELISA tests (98% overall agreement, 0.91 correlation coefficient; 6% bias) (Table 1).

Overall agreements for visual and automated (PQreader) interpretations with Promonitor Quick ANTI-IFX were 99% and 100% for finger prick and serum specimens, respectively (Table 1).

Conclusion

Promonitor Quick can be used to reliably quantify infliximab in capillary blood samples and results are comparable to those obtained with the reference ELISA technique. The use of the rapid POC test with finger prick will allow clinicians to monitor their patients in a fully decentralized mode to aid in the decision making process. PQreader is a sensitive portable equipment to report drug as well as antibody levels in the patient samples.

References

[1]Atreya, R. et al. J Crohns Colitis. 2019;13:S391

[2]Ametzazurra, A. et al. J Crohns Colitis. 2017;11:S335-S336

[3]Fiorino, G. et al. J Crohns Colitis. 2017;11:S388

[4]Facchin, A. et al. J Crohns Colitis. 2019;13:S349- S350

Disclosure of Interests

M. Begoña Ruiz-Argüello Employee of: Employee of Progenika Biopharma - Grifols, Javier Pascual Employee of: Employee of Progenika Biopharma - Grifols, Lorena Del Rio Employee of: Employee of Progenika Biopharma - Grifols, Ane Urigoitia Employee of: Employee of Progenika Biopharma - Grifols, Cristina Balo-Farto: None declared, Carlos Fernández-López: None declared, ANTONIO MERA VARELA: None declared, Francisco Javier de-Toro-Santos: None declared, Daniel Nagore Employee of: Employee of Progenika Biopharma - Grifols, Amagoia Ametzazurra Employee of: Employee of Progenika Biopharma - Grifols

AB0354 THERAPEUTIC DRUG MONITORING: PERFORMANCE OF THE FIRST LATERAL FLOW-BASED POINT OF CARE TEST FOR THE QUANTIFICATION OF INFLIXIMAB IN A FINGER PRICK

Background

Promonitor Quick IFX is a lateral flow test (LFT) for the quantification of infliximab (IFX) in human whole blood (finger prick or venous) or serum in 20 minutes. This LFT is based on a sandwich immunoassay to quantify either the reference IFX or biosimilars.

Objectives

The objective of this study was to perform the required analytical studies to establish the specifications of the product.

Methods

Clinical and Laboratory Standards Institute (CLSI) guidelines were followed for the evaluation of the analytical specifications of the LFT in whole blood and serum matrices: Linearity (EP-06-A), Detection capability (EP17-A2), Interfering substances (EP07, 3rd Edition) and Intermediate precision (EP05-A3). Results were obtained in combination with the automated portable reader PQreader. A Datamatrix provided with each Promonitor Quick IFX kit contains the calibration information required for the PQreader to measure the Control and Test lines and report the IFX concentration.

Results

The linear assay range was determined to be 1-58 µg/mL in whole-blood and 0.6-67 µg/mL in serum according to the processes indicated in the Package Insert. The Limit of Blank is 0.8 μg/mL, the Limit of Detection and Lower Limit of Quantification (LLoQ) are 1.1 μg/mL, and the Upper Limit of Quantification (ULoQ) is 15.4 μg/mL.

There was no effect on assay performance when each of the following substances were added to samples with 0, 3, and 7 μg/mL of IFX: Haemoglobin (>1000 mg/dL), Bilirubin (>40 mg/dL), Triglycerides (>1500 mg/dL), HAMA (160 AU/mL), Rheumatoid factor (200 IU/mL), EDTA (5.4 mg/mL), Heparin (51 U/mL), Citrate (11.4%), Vedolizumab (60 μg/mL) and Adalimumab (20.25 μg/mL).

Repeatability and within-device precision results obtained for the positive samples are shown in Table 1.

Table 1.IFX theoretical concentration (μg/mL)Whole blood samplesSerum samplesMean observed IFX concentration (μg/mL)RepeatabilityWithin-device precisionMean observed IFX concentration (μg/mL)RepeatabilityWithin-device precisionSDCV%SDCV%SDCV%SDCV%33.20.6180.8253.60.5150.617771.3181.7248.31.4161.821109.81.8182.72810.91.8162.321

The negative samples showed a negative result in all the measurements.

Conclusion

Promonitor Quick IFX is the first LFT available for true Point of Care testing of patients treated with IFX with just a finger prick sample. It provides quick turnaround time to facilitate therapeutic drug monitoring and aid immediate decision making in the doctor office or hospitals with an excellent analytical performance.

Disclosure of Interests

Amagoia Ametzazurra Employee of: Employee of Progenika Biopharma - Grifols, Javier Pascual Employee of: Employee of Progenika Biopharma - Grifols, Lorena Del Rio Employee of: Employee of Progenika Biopharma - Grifols, Ainara Maguregui Employee of: Employee of Progenika Biopharma - Grifols, Daniel Nagore Employee of: Employee of Progenika Biopharma - Grifols, M. Begoña Ruiz-Argüello Employee of: Employee of Progenika Biopharma - Grifols

Both soluble and membrane-anchored forms of Felid herpesvirus 1 glycoprotein G function as a broad-spectrum chemokine-binding protein

Recently, glycoprotein G (gG) of several alphaherpesviruses infecting large herbivores was shown to belong to a new family of chemokine-binding proteins (vCKBPs). In the present study, the function of Felid herpesvirus 1 (FeHV-1) gG as a vCKBP was investigated and the following conclusions were reached: (i) FeHV-1 secreted gG is a high-affinity broad-spectrum vCKBP that binds CC, CXC and C chemokines; (ii) gG is the only vCKBP expressed by FeHV-1 that binds CCL3 and CXCL1; (iii) secreted gG blocks chemokine activity by preventing their interaction with high-affinity cellular receptors; (iv) the membrane-anchored form of gG expressed on the surface of infected cells is also able to bind chemokines; and (v) the vCKBP activity is conserved among different field isolates of FeHV-1. Altogether, these data demonstrate that FeHV-1 gG is a new member of the vCKBP-4 family. Moreover, this study is the first to demonstrate that gG expressed at the surface of FeHV-1-infected cells can also bind chemokines.

Cleavage of the human respiratory syncytial virus fusion protein at two distinct sites is required for activation of membrane fusion

Preparations of purified full-length fusion (F) protein of human respiratory syncytial virus (HRSV) expressed in recombinant vaccinia-F infected cells, or of an anchorless mutant (F(TM(-))) lacking the C-terminal 50 amino acids secreted from vaccinia-F(TM(-))-infected cells contain a minor polypeptide that is an intermediate product of proteolytic processing of the F protein precursor F0. N-terminal sequencing of the intermediate demonstrated that it is generated by cleavage at a furin-motif, residues 106-109 of the F sequence. By contrast, the F1 N terminus derives from cleavage at residue 137 of F0 which is also C-terminal to a furin recognition site at residues 131-136. Site-directed mutagenesis indicates that processing of F0 protein involves independent cleavage at both sites. Both cleavages are required for the F protein to be active in membrane fusion as judged by syncytia formation, and they allow changes in F structure from cone- to lollipop-shaped spikes and the formation of rosettes by anchorless F.

Effect of Sublytic Concentrations of Sodium Cholate on Phospholipase C Hydrolysis of Phospholipid Bilayers

Phospholipase C activity has been assayed with phosphatidylcholine as substrate in the presence of sodium cholate at concentrations well below those producing lipid solubilization. With short-chain phosphatidylcholine, which exists in monomeric form in aqueous solution, cholate has little or no effect. However, when the substrate is egg phosphatidylcholine in the form of bilayers, small cholate concentrations (below 1 mM, corresponding to an effective surfactant:lipid ratio below 0.05) increase the maximum enzyme rates by about threefold, while decreasing drastically the latency periods of enzyme activity. Previous studies from this laboratory have associated the phospholipase enhancing activity of a variety of amphiphiles to their ability to facilitate the formation of inverted hexagonal phospholipid structures, yet sodium cholate has the opposite effect, stabilizing the lamellar versus the inverted hexagonal phase. This suggests that cholate is activating phospholipase C through a hitherto undescribed mechanism. Sodium cholate concentrations above 1 mM decrease further the enzyme lag time, but they are less effective in enhancing enzyme rates. These observations may be pertinent in the analysis of biochemical data with purified lipases, as well as in physiological studies of biliary function. Copyright 1999 Academic Press.

Vesicle membrane fusion induced by the concerted activities of sphingomyelinase and phospholipase C

When vesicles composed of an equimolar mixture of sphingomyelin, phosphatidylcholine, phosphatidylethanolamine, and cholesterol are treated with phospholipase C, phospholipid hydrolysis occurs without major changes in vesicle architecture. In the same way, addition of sphingomyelinase leads only to sphingomyelin cleavage. However, when both enzymes are added together, their joint hydrolytic activities give rise to leakage-free vesicle aggregation, lipid mixing, and aqueous contents mixing, i.e. vesicle fusion. The contribution of both enzymes is unequal, the main role of sphingomyelinase being the production of relatively large amounts of ceramide that will facilitate the lamellar-to-nonlamellar transition in the formation of the fusion pore, whereas phospholipase C provides mainly a localized, asymmetric, high concentration of diacylglycerol that constitutes the trigger for the fusion process. The lipidic end-products of both enzymes cooperate in destabilizing and fusing the membranes in a way that is never achieved through the action of any of the enzymes individually, nor by the products themselves when premixed with the other lipids during liposome preparation. Thus the enzymes appear to be coupled through their reaction products. This is the first observation of membrane fusion induced by the concerted activities of two enzymes. Besides, considering that both diacylglycerol and ceramide are important metabolites involved in cell signaling, it may also provide new ideas in the exploration of "cross-talk" phenomena between different signal transduction pathways.

Phospholipase C hydrolysis of phospholipids in bilayers of mixed lipid compositions

Phosphatidylcholine phospholipase C (EC 3.1.4.3) from Bacillus cereus has been assayed with substrates in the form of large unilamellar vesicles. Phosphatidylcholine, phosphatidylethanolamine (also a substrate for the enzyme), sphingomyelin, and cholesterol have been mixed in various proportions, in binary, ternary, and quaternary mixtures. A lag period, followed by a burst of enzyme activity, has been found in all cases. The activity burst was always accompanied by an increase in turbidity of the vesicle suspension. Varying lipid compositions while keeping constant all the other parameters leads to a range of lag times extending over 2 orders of magnitude (from 0.13 to 38.0 min), and a similar variability is found in maximal enzyme rates (from 0.40 to 55.9 min-1). Meanwhile, the proportion of substrate that is hydrolyzed during the lag period remains relatively constant at 0.10% moles of total lipid, in agreement with the idea that enzyme activation is linked to vesicle aggregation through diacylglycerol-rich patches. Phosphatidylethanolamine and cholesterol enhance the enzyme activity in a dose-dependent way: they reduce the lag times and increase the maximal rates. The opposite is true of sphingomyelin. These lipids exert each its own peculiar effect, positive or negative, either alone or in combination, so that the susceptibility of a given mixture to the enzyme activity can be to some extent predicted from its composition. Phospholipase C activity is not directly influenced by the formation of nonlamellar structures. However, the presence of lipids with a tendency to form nonlamellar phases, such as phosphatidylethanolamine or cholesterol, stimulates the enzyme even under conditions at which purely lamellar phases exist. Conversely sphingomyelin, a well-known stabilizer of the lamellar phase, inhibits the enzyme. Thus phospholipase C appears to be regulated by the overall geometry and composition of the bilayer.

Phosphatidylinositol-dependent membrane fusion induced by a putative fusogenic sequence of Ebola virus

The membrane-interacting abilities of three sequences representing the putative fusogenic subdomain of the Ebola virus transmembrane protein have been investigated. In the presence of calcium, the sequence EBO(GE) (GAAIGLAWIPYFGPAAE) efficiently fused unilamellar vesicles composed of phosphatidylcholine, phosphatidylethanolamine, cholesterol, and phosphatidylinositol (molar ratio, 2:1:1:0.5), a mixture that roughly resembles the lipid composition of the hepatocyte plasma membrane. Analysis of the lipid dependence of the process demonstrated that the fusion activity of EBO(GE) was promoted by phosphatidylinositol but not by other acidic phospholipids. In comparison, EBO(EA) (EGAAIGLAWIPYFGPAA) and EBO(EE) (EGAAIGLAWIPYFGPAAE) sequences, which are similar to EBO(GE) except that they bear the negatively charged glutamate residue at the N terminus and at both the N and C termini, respectively, induced fusion to a lesser extent. As revealed by binding experiments, the glutamate residue at the N terminus severely impaired peptide-vesicle interaction. In addition, the fusion-competent EBO(GE) sequence did not associate significantly with vesicles lacking phosphatidylinositol. Tryptophan fluorescence quenching by vesicles containing brominated phospholipids indicated that the EBO(GE) peptide penetrated to the acyl chain level only when the membranes contained phosphatidylinositol. We conclude that binding and further penetration of the Ebola virus putative fusion peptide into membranes might be governed by the nature of the N-terminal residue and by the presence of phosphatidylinositol in the target membrane. Moreover, since insertion of such a peptide leads to membrane destabilization and fusion, the present data would be compatible with the involvement of this sequence in Ebola virus fusion.

Morphological changes induced by phospholipase C and by sphingomyelinase on large unilamellar vesicles: a cryo-transmission electron microscopy study of liposome fusion

Cryo-transmission electron microscopy has been applied to the study of the changes induced by phospholipase C on large unilamellar vesicles containing phosphatidylcholine, as well as to the action of sphingomyelinase on vesicles containing sphingomyelin. In both cases vesicle aggregation occurs as the earliest detectable phenomenon; later, each system behaves differently. Phospholipase C induces vesicle fusion through an intermediate consisting of aggregated and closely packed vesicles (the "honeycomb structure") that finally transforms into large spherical vesicles. The same honeycomb structure is also observed in the absence of enzyme when diacylglycerols are mixed with the other lipids in organic solution, before hydration. In this case the sample then evolves toward a cubic phase. The fact that the same honeycomb intermediate can lead to vesicle fusion (with enzyme-generated diacylglycerol) or to a cubic phase (when diacylglycerol is premixed with the lipids) is taken in support of the hypothesis according to which a highly curved lipid structure ("stalk") would act as a structural intermediate in membrane fusion. Sphingomyelinase produces complete leakage of vesicle aqueous contents and an increase in size of about one-third of the vesicles. A mechanism of vesicle opening and reassembling is proposed in this case.

Different effects of enzyme-generated ceramides and diacylglycerols in phospholipid membrane fusion and leakage

When large unilamellar vesicles consisting of sphingomyelin:phosphatidylethanolamine:cholesterol (2:1:1 molar ratio) are treated with sphingomyelinase, production of ceramides in the bilayer is accompanied by leakage of vesicle aqueous contents and by vesicle aggregation in the absence of lipid mixing or vesicle fusion. This is in contrast to the situation of phosphatidylcholine:phosphatidylethanolamine:cholesterol (2:1:1 molar ratio) liposomes when treated with phospholipase C. In that case, in situ generation of diacylglycerol leads to vesicle aggregation followed by vesicle fusion in the absence of leakage (Nieva, J. L., Goñi, F. M., and Alonso, A. (1989) Biochemistry 28, 7364-7367). Moreover, when ceramides (5-10 mol %) are included in the formulation of the phosphatidylcholine-containing vesicles, they reduce the lag time of phospholipase C-induced fusion, although they are less active than diacylglycerols in this respect. 31P NMR studies of aqueous lipid dispersions show that diacylglycerols as well as ceramides induce a thermotropic lamellar to non-lamellar phase transition in both phospholipid:cholesterol mixtures under study although sphingomyelin-containing bilayers are more stable than those containing phosphatidylcholine, and ceramide is less active than diacylglycerol in promoting non-lamellar phase formation. These observations are relevant to both the physiological role of ceramides and the current views on the mechanism of membrane fusion.