Author byline as per print journal: Lyndsay Davies1, PhD; Katie Milligan1, BSc; Mark Corris1, BSc; Ian Clarke1; Paul Dwyer1, MSc; Sarah Elizabeth Lee2, PhD; Jolene Teraoka3, BSc; Jill Crouse-Zeineddini3, PhD; Jane Hippenmeyer4, PharmD
Study Objectives: To investigate the quality and in-use stability of the trastuzumab biosimilar ABP 980 (KANJINTI™) in both concentrated multi-dose bags and following dilution and extended storage in intravenous (IV) bags and elastomeric devices, to address the stability requirements of different global pharmacy practices.
Submitted: 19 July 2021; Revised: 30 September 2021; Accepted: 1 October 2021; Published online first: 14 October 2021
KANJINTI™ (trastuzumab; Amgen), a biosimilar for Herceptin® (Roche), is a human epidermal growth factor 2 (HER2)-targeted humanized monoclonal antibody for the treatment of HER-2 positive early and metastatic breast cancer and metastatic gastric cancer . Supplied as a powder for concentrate for solution for infusion, trastuzumab is first reconstituted with sterile water for injection (sWFI) prior to dilution in 0.9% w/v NaCl in polyvinylchloride (PVC), polyethylene (PE) or polypropylene (PP) bags . Monoclonal antibodies are complex molecules and are subject to a variety of degradation routes that can be initiated by many factors including formulation, environment, and manipulations , many of which are encountered during preparation, transport and storage. The stability data provided in the Summary of Product Characteristics (SmPC) for the majority of antibody therapeutics has, until recently, usually been limited to 24–48 hours following dilution for intravenous infusion (IV), with statements that from a microbiological point of view, the product should be used immediately. Recently, the SmPCs of many of the originator antibody therapeutic products have been updated to provide extended stability once diluted. For example, the trastuzumab originator, Herceptin®, has seen two updates to the shelf life since August 2018 ; from stating that solutions of Herceptin® for IV infusion are physically and chemically stable for 24 hours not exceeding 30°C, the SmPC was updated to 7 days (published on emc on 29/08/2018) and subsequently 30 days at 2°C–8°C (21/03/2019), and 24 hours at temperatures not exceeding 30°C. The same recommendations are provided in the current SmPC for KANJINTI™ (trastuzumab) . Despite the extended stability data provided by SmPCs, the immediate use of the infusion solutions from a microbiological point of view is still advised, otherwise, the in-use storage times and conditions prior to use are the responsibility of the user, with the recommendation that this would not normally be longer than 24 hours at 2°C–8°C unless reconstitution and dilution have taken place under controlled and validated aseptic conditions. Extension of the shelf life of products places more emphasis on the quality of the aseptic preparation; since preparation of such therapeutics varies by region and sometimes takes place on the wards or other locations with poorly controlled aseptic conditions. This is especially prevalent in situations without extended shelf life, as doses are prepared and used in close proximity to the patients. An extended shelf life can allow more economical and efficient use of pharmacy aseptic units and drug, allowing advanced batch preparation, dose banding strategies  and vial sharing. Preparation under controlled and validated aseptic conditions not only enhances patient safety but also contributes to cost savings by reducing the waste of these expensive drugs, both by utilizing whole vial volumes and avoiding missed doses caused by patient failing to show for appointments or unexpected delays in treatment, by continued storage of the un-administered drug. For the advantages of shelf-life extension to be realized, reliable stability data is of immense value for allowing the safe preparation, storage and use of the drug preparations.
In the United Kingdom (UK), shelf-life extension can be applied to antibody therapeutic preparations providing there is robust stability data to support it; this allows pharmacy aseptic units to assign an extended shelf life to its own preparations under both Section 10 exemption and under the terms of a Specials Licence. The UK National Health Service (NHS) document ‘A Standard Protocol for Deriving and Assessment of Stability Part 2 – Aseptic Preparations (Biopharmaceuticals), 4th Edition, August 2020’ provides guidance for the design and assessment of a robust stability study in support of shelf-life extension . In other countries, drug solutions are prepared by centralized pharmacies or compounding units for transport to clinical sites, which requires longer storage periods than those recommended by the manufacturer; stability data supporting the in-use period of these drugs is therefore vital to provide assurance of their stability during preparation, storage, transportation and administration. Compounding units in Italy are known to prepare pharmacy bulk packs, essentially multi-dose bags containing concentrated drug, which are supplied to hospital pharmacies. Suitable stability data on such stock preparations allows extended storage by the pharmacy for use in making patient-specific doses. Although not an accepted practice in the UK, stability of reconstituted KANJINTI™ (trastuzumab) 21 mg/mL solution stored refrigerated for up to 63 days in multi-dose IV bags was investigated in this study, with additional assessment on the diluted 0.3 mg/mL and 4 mg/mL in 0.9% w/v NaCl infusion solutions that were prepared from multi-dose bags.
The combination of a population increasing in age, new therapies, speciality medications that require expert administration and longer treatment cycles has resulted in an increased demand on healthcare services with additional pressures on clinicians and pharmacy aseptic services. Ambulatory infusion therapy allows medically stable patients to be treated at home or at alternate sites, reducing the need for lengthy hospital stays and often avoiding the need for hospital admission . In addition to assessing the stability of KANJINTI™ (trastuzumab) infusions in polyolef in IV bags, this study investigated the stability of KANJINTI™ (trastuzumab) infusions in a portable elastomeric infusion system that allows continuous IV administration of medications in any setting; medication is delivered to the patient as the elastomeric ‘balloon’ consistently deflates and pushes solution through the IV tubing and into the catheter/port. However, the materials in the elastomeric pump device differ from the PVC, PE or PP bags that the SmPC describes are compatible for preparation of the diluted KANJINTI™ (trastuzumab) infusion, with the elastomeric balloon made from polyisoprene and tubing which may be primed with solution following preparation. Stability of drug following extended storage in these devices is therefore important to ensure the absence of drug-container interactions.
The stability of the trastuzumab originator (Herceptin®) in ready-to-administer presentations [7-10] and, more recently, stability data on several trastuzumab biosimilars [11-14] has been previously reported. To address the stability requirements of different global pharmacy practices, we have conducted a comprehensive study to investigate the effects of extended storage on the trastuzumab biosimilar, KANJINTI™, using several complementary methods to evaluate the stability of a range of concentrations in different containers and storage regimes, as summarized in Table 1. Study 1 evaluated the stability of 21 mg/mL reconstituted solution stored in IV bags (multi-dose bags) for 6 hours at room temperature (17°C–-23°C; RT) followed by 63 days at 2°C–8°C, and following dilution from pre-stored multi-dose bags in 0.9% w/v NaCl to 0.3 mg/mL and 4 mg/mL, stored for 6 hours at RT followed by 4 days at 2°C–8°C plus 24 hours at 25°C/60% relative humidity (RH), in polyolef in IV bags. Study 2 evaluated the stability of KANJINTI™ (trastuzumab) following dilution in 0.9% w/v NaCl to 0.3 mg/mL, 0.8 mg/mL and 4 mg/mL when stored in polyolef in IV bags and INTERMATE® elastomeric infusion pump devices under different storage regimes, as summarized in Table 1; to present a further stability challenge, all diluted products in Study 2 were prepared using KANJINTI™ (trastuzumab) reconstituted solutions that had been stored in pierced vials at 2°C–8°C, protected from light, for 11 days.
Preparation and storage of KANJINTI™ (trastuzumab) solutions
All KANJINTI™ (trastuzumab) solutions were aseptically prepared by the Royal Liverpool and Broadgreen University Hospitals NHS Trust (RLBUHT) Pharmacy Aseptic Production Unit in a Positive Pressure Isolator. KANJINTI™ (trastuzumab) 150 mg powder for concentrate for solution for infusion (Amgen Inc) was reconstituted with sterile water for injection (sWFI), as instructed in the SmPC , to a final concentration of 21 mg/mL trastuzumab. For the purpose of sampling, all IV bags had a non-vented dispensing pin installed into the giving port during aseptic preparation. All concentrated and diluted KANJINTI™ (trastuzumab) solutions were stored protected from light in storage areas that are subject to constant temperature monitoring.
Study 1: For preparation of the multi-dose bags of reconstituted solution, a non-vented dispensing pin was installed into the giving port of a 50 mL NaCl 0.9% w/v solution for infusion VIAFLO® bag (Baxter), and the contents withdrawn using a sterile 50 mL syringe, ensuring the removal of as much solution as possible. The contents of seven reconstituted KANJINTI™ (trastuzumab) vials were combined and added to an empty 50 mL VIAFLO® bag. Three bags (A1, A2, A3) were prepared for initial testing (T0) prior to storage at RT (17°C–23°C) for 6 hours followed by 2°C–8°C storage for 63 days. Testing was carried out following 7 days, 20 days, 41 days and 63 days of storage.
A further three multi-dose bags of reconstituted KANJINTI™ (trastuzumab) solution were prepared (B1, B2, B3) and stored at 2°C–8°C; Bag B1 was stored for 22 days, Bag B2 for 42 days and Bag B3 for 63 days. Following the specified storage period, the concentrated bags were each used to prepare three bags of 0.3 mg/mL and three bags of 4 mg/mL in 0.9 % w/v NaCl, by dilution of the appropriate volume of the reconstituted KANJINTI™ (trastuzumab) solution in 50 mL NaCl 0.9% w/v solution for infusion VIAFLO® bag (Baxter). The 0.3 mg/mL and 4 mg/mL solutions were tested on the day of preparation (T0), prior to storage at RT (17°C–23°C) for 6 hours followed by 4 days storage at 2°C–8°C plus 24 hours at 25°C/60%RH, after which final testing was carried out.
Study 2: Following reconstitution of KANJINTI™ (trastuzumab) 150 mg powder for concentrate for solution for infusion vials as instructed by the SmPC , the rubber stopper of each vial was pierced an additional three times in different locations using a 19G needle and stored at 2°C–8°C for 11 days. These pierced vials (PV) were diluted to f inal concentrations of 0.3 mg/mL, 0.8 mg/mL and 4 mg/mL in 100 mL NaCl 0.9% w/v solution for infusion VIAFLO® bags (Baxter; 3 bags of each concentration) or INTERMATE® SV System 100 mL/h (Baxter; 3 devices of each concentration). The diluted solutions were tested within 2 hours of preparation (T0), prior to storage at RT (17°C–23°C) for 6 hours followed by 2°C–8°C storage. KANJINTI™ (trastuzumab) 0.3 mg/mL solutions were stored refrigerated for 21 days prior to transfer to 25°C/60%RH storage for 24 hours, with testing after 7 days, 14 days, 21 days and 22 days storage; 0.8 mg/mL and 4 mg/mL solutions were stored refrigerated for 76 days plus an additional 48 hours at 25°C/60%RH, with testing after 14 days, 35 days, 56 days, 76 days, 77 days and 78 days storage. Note that two sets of 0.8 mg/mL and 4 mg/mL VIAFLO® bags were prepared as indicated in Table 1; Set 2 was used for bioassay and assessment of trastuzumab concentration by SEC-HPLC and were stored for total of 79 days, see Table 1, with testing after 14 days, 35 days, 56 days, 77 days, 78 days and 79 days storage. Set 1 was used for all other tests. For clarity of presentation, results from Set 1 and Set 2 bags are listed with the total storage time of 78 days to represent the shortest storage period.
Sampling for analysis
All sampling and testing (with the exception of the bioassay) was performed at Quality Control North West Liverpool, UK, which is hosted by the Liverpool University Hospitals NHS Foundation Trust. Initial testing was performed within 2 hours of sample preparation, prior to storage of samples. At subsequent time points, containers were removed from storage and allowed to equilibrate to room temperature (protected from light) for 30 mins. Prior to sampling, each container was gently inverted 10 times and left to stand for 2 mins to eliminate gas bubbles. Sampling from containers was carried out in a Class II Safety Cabinet using aseptic technique. A pre-cut (4 cm) Lectrocath Line was attached to the Dispensing Pin on each of the IV bags using the Luer Lock connection and an appropriate volume of sample was drained and collected from each bag for testing; separate aliquots were collected for sub-visible particle count analysis. The Lectrocath Line was then disconnected from the bag. For the INTERMATE® pump device products, the initial 2 mL was drained to a separate tube (to remove sample stored in the delivery tube) and visually inspected prior to dispensing to waste. The appropriate volume of sample was then drained and collected from each device for testing; separate aliquots were collected for subvisible particle count analysis. Samples for bioassay testing were collected in Cryovials with External Thread, Self-Sealing Cap (1.0 mL, Skirted; Starlab (UK) Ltd). Cryovials were immersed into liquid nitrogen for 1 min then stored at -80°C. Following sampling, the containers were returned to the appropriate storage area for testing at subsequent time points. Samples for bioassay testing were stored at -80°C until all time points had been collected; they were then transferred to Amgen Inc. under dry ice storage for bioassay analysis at the Attribute Sciences Potency and Characterization Laboratory, USA.
Forced degradation (aged samples)
A series of ‘aged’ trastuzumab samples were prepared for use as system suitability samples to demonstrate the stability-indicating ability of the analytical techniques employed. A vial of KANJINTI™ (trastuzumab) 150 mg powder for concentrate for solution for infusion was reconstituted as per SmPC  to produce a 21 mg/mL reconstituted solution, which was stored exposed to ambient temperature (17°C–23°C) and natural daylight; an aliquot of this solution was withdrawn at intervals (specified in Table 2) over 89 days and diluted with 0.9% w/v NaCl to 0.3 mg/mL.
Appearance by visual inspection
Solution colour, clarity and particulate formation were monitored by visual inspection of a single sample from each container. Following sampling, each KANJINTI™ (trastuzumab) sample was viewed in the clear colourless sample tube against a white background to assess colour and against a black background for clarity and compared to a sample of distilled water as a reference. Samples were also viewed in their containers for the presence of visible particles using a light magnifier. Particular attention was made to the sample in the delivery line of the INTERMATE® devices for evidence of precipitation.
pH was determined based on Ph. Eur. Method 2.2.3 , using a Mettler Toledo SevenMulti™ pH meter and a Mettler Toledo InLab® MicroPro-ISM probe or InLab® ExpertPro probe. The instrument was calibrated using pH 4.00, pH 7.00 and pH 9.00 certified buffer solutions (SPEX CertiPrep) prior to measuring KANJINTI™ (trastuzumab) samples that were equilibrated to a temperature of 20°C–25°C.
Size Exclusion Chromatography (SEC)
The trastuzumab monomer concentration and % ratio of the trastuzumab monomer, high molecular weight species (HMW; e.g. dimers, trimers, higher order aggregates) and low molecular weight species (LMW; e.g. fragmentation products) was determined by size-exclusion chromatography-HPLC (SEC-HPLC) using a validated stability-indicating method on an Agilent 1100 Series HPLC system with UV detector. Chromatographic results were collected by data handling software [Agilent OpenLab CDS (Version A.01.04) EZChrom Edition (Version A.04.04) or OpenLab CDS Version 2.4]. The chromatographic separation was performed at ambient temperature on a Tosoh Bioscience TSK gel G3000 SWXL column (7.8 mm x 30.0 cm) using a mobile phase composition of 25 mM Na2HPO4, 25 mM NaH2PO4, and 0.3 M NaCl, pH 6.8. Mobile phase was filtered through a 0.45 μm Nylon filter membrane under vacuum prior to use. An isocratic flow rate of 0.8 mL/min was maintained for a run time of 26 mins per injection for Standards, 21 mg/mL and 4 mg/mL samples. The run time was extended to 40 mins for 0.3 mg/mL and 0.8 mg/mL product samples due to a peak eluting around 26 mins that was attributable to the VIAFLO® bag contents. A detection wavelength of 220 nm was used with an injection volume of 50 μl. The autosampler tray temperature was maintained at 5°C throughout the analysis.
The 0.3 mg/mL samples were injected without further dilution, 0.8 mg/mL, 4 mg/mL and 21 mg/mL samples were diluted to 0.3 mg/mL with 0.9% w/v NaCl. The trastuzumab monomer concentration in each sample was determined by assaying against three freshly prepared trastuzumab standards, prepared at each time point from KANJINTI™ (trastuzumab) powder for concentrate for solution for infusion (Amgen) to give nominal concentrations of 0.375 mg/mL, 0.3 mg/mL and 0.225 mg/mL trastuzumab; results were calculated as a % of the initial trastuzumab monomer concentration at T0. The method was quantitatively validated in terms of precision, accuracy, linearity, stability of analytical solutions, robustness, limit of detection (LOD), limit of quantification (LOQ) and selectivity. The stability-indicating ability of the method was confirmed through forced degradation studies.
Non-Reducing (NR) and Reducing (RED)-Capillary Gel Electrophoresis (CGE)
To monitor the purity of trastuzumab, CGE was performed under both non-reducing and reducing conditions using a deltaDOT High Performance Capillary Electrophoresis platform, HPCE-512TC (deltaDOT Ltd, UK), using a 32.7 cm 50 μm I.D. fused silica capillary with a 20 cm separation length. Separation of SDS-protein complexes was achieved using SDS-MW Gel Buffer (Beckman Coulter). The capillary and sample carousel were maintained at 22°C. Separation was monitored on-column at 214 nm by diode array. CGE results were collected by P3Controller software and analysed using P3Eva software (deltaDOT Ltd, UK). Both NR- and RED-CGE methods were validated in terms of linearity, precision, stability of solution, LOQ and selectivity. Samples were analysed alongside a reduced protein size standard (MW Sizing Standard; Beckman Coulter) and a trastuzumab standard that was freshly prepared from KANJINTI™ (trastuzumab) powder for concentrate for solution for infusion (Amgen) to be matched in terms of matrix and concentration to the analytical samples. KANJINTI™ (trastuzumab) 0.3 mg/mL and 0.8 mg/mL samples were used without dilution, KANJINTI™ (trastuzumab) 21 mg/mL and 4 mg/mL samples were diluted to 0.3 mg/mL (Study 1) or 0.8 mg/mL (Study 2) with 0.9% w/v NaCl prior to preparing SDS-protein complexes by combination with a concentrated SDS sample buffer (600 mM Tris-HCl pH 9.0 containing 10% SDS). For NR-CGE, each SDS-trastuzumab complex was alkylated with Iodoacetamide (IAM), added to a f inal concentration of 30 mM prior to heating at 70°C for 10 mins. A system suitability sample was prepared without the addition of IAM and heated to 100°C for 10 mins to induce fragmentation. Samples were introduced on to the capillary hydrodynamically at 10 psi for 20 secs and separated at 16 kV (reverse polarity) for 37 mins. For RED-CGE, each SDS-trastuzumab complex was reduced by adding 3% v/v 2-mercaptoethanol prior to heating at 70°C for 10 mins. Samples were introduced on to the capillary hydrodynamically at 10 psi for 10 secs and separated at 16 kV (reverse polarity) for 31 mins. Analysis of a forced degraded (aged) sample demonstrated the stability-indicating nature of the method.
Capillary Zone Electrophoresis (CZE)
Charge variants were analysed by Capillary Zone Electrophoresis (CZE), performed on a deltaDOT HPCE-512TC (deltaDOT Ltd, UK), using a 61.1 cm 50 μm I.D. fused silica capillary with a 48.8 cm separation length. CZE separations were performed in a buffer comprised of 0.05% HPMC, 500 mM EACA, 1.9 mM TETA, pH 5.7. All samples were injected hydrodynamically at 0.5 psi for 10 secs and separated at 20 kV (standard polarity) for 42 mins. The capillary was maintained at 25°C, the sample carousel was held at 16°C. All detection was at 214 nm by diode array. The CZE method was validated in terms of linearity, precision, stability of solution, LOQ and selectivity. KANJINTI™ (trastuzumab) 0.3 mg/mL and 0.8 mg/mL samples were used for CZE analysis without further dilution; KANJINTI™ (trastuzumab) 21 mg/mL and 4 mg/mL samples were diluted to 0.3 mg/mL (Study 1) or 0.8 mg/mL (Study 2) with 0.9% w/v NaCl. Samples were analysed alongside a trastuzumab standard that was freshly prepared from KANJINTI™ (trastuzumab) powder for concentrate for solution for infusion (Amgen) to be matched in terms of matrix and concentration to the analytical samples. Analysis of a forced degraded (aged) KANJINTI™ (trastuzumab) sample, exposed to ambient conditions (ambient temperature and natural daylight), was used to demonstrate the stability-indicating ability of the CZE system.
Sub-visible particle count analysis
Particle counting was performed using a HIAC 9703+ liquid particle counter and accompanying PharmSpec software (Beckman Coulter), with analysis based on the US Pharmacopeia (USP) monograph USP41<787> . Test samples were allowed to equilibrate to ambient temperature prior to testing; 5 x 0.5 mL counts were performed; the first reading was discarded, and the remaining results averaged.
A cell-based proliferation inhibition assay was performed using the human breast tumour cell line, BT-474, which expresses human epidermal growth factor receptor 2 (HER2), the target antigen for trastuzumab. BT-474 cells were incubated with varying concentrations of KANJINTI™ (trastuzumab) reference standard, control and test samples. The endpoint detection reagent CellTiter-Glo® was used to determine the number of viable cells. When incubated with cells, this reagent produces a luminescence signal that is proportional to the amount of adenosine triphosphate (ATP) present, which is directly proportional to the number of viable cells, and inversely proportional to the concentration of the drug. The biological activity of the test sample was determined by comparison of the test sample response to that of the Reference Standard (relative potency). The final reported result is the arithmetic mean of 3 individual determinations.
Study 1: The reconstituted KANJINTI™ (trastuzumab) 21 mg/mL solutions stored in 50 mL VIAFLO® bags were clear and colourless on the day of preparation (T0), but were observed as clear, very pale-yellow solutions following 7 days storage at 2°C–8°C, which remained throughout 63 days storage. No visible particles were detected at any time point. The appearance of the reconstituted solutions did comply with the description provided in the SmPC  for reconstituted KANJINTI™ (trastuzumab), which states it as ‘a colourless to pale-yellow transparent solution’ that ‘should be essentially free of visible particulates’.
KANJINTI™ (trastuzumab) 0.3 mg/mL and 4 mg/mL in 0.9% w/v NaCl samples were clear colourless solutions with no detectable visible particulates, when prepared from 22 day and 42 day stored multi-dose bags and stored refrigerated for 4 days plus 24 hours at 25°C/60%RH. Diluted 0.3 mg/mL and 4 mg/mL samples prepared from 63 day stored multi-dose bag of reconstituted KANJINTI™ (trastuzumab) solution appeared as clear very pale-yellow solutions with a few small translucent particles on the day of preparation; although only a few particles were detected, it was noted that these were more prominent in the 0.3 mg/mL products compared with the 4 mg/mL products. Although the pale-yellow colour remained, the particles were not visible following storage at 2°C–8°C for 4 days plus 24 hours at 25°C/60%RH.
Study 2: All samples remained clear and colourless for the duration of the respective study (0.3 mg/mL: 21 days refrigerated plus 24 hours at 25°C/60%RH; 0.8 mg/mL and 4 mg/mL: 76 days refrigerated plus 48 hours at 25°C/60%RH), with no visible precipitates or particulate matter detected.
Study 1: No significant change was observed for the pH of the reconstituted KANJINTI™ (trastuzumab) 21 mg/mL solutions stored in 50 mL VIAFLO® bags stored refrigerated for 63 days; the mean pH throughout the duration of the study was pH 6.11, which is in agreement with that stated for the reconstituted solution in the SmPC , which states a pH of approximately 6.1. All three bags remained within 0.15 pH units of the initial pH at T0 at each time point. The pH of the diluted 4 mg/mL samples prepared from the 22 day, 42 day and 63 day stored multi-dose bags of reconstituted KANJINTI™ (trastuzumab) solution all remained close to pH 6.1, whereas the diluted 0.3 mg/mL bags had a lower average of pH 5.9, most likely reflecting the lower buffering capacity of the excipients. The 4-day refrigerated plus 24 hours at 25°C/60%RH storage had no significant effect on the pH of the diluted samples at either concentration, see Figure 1A.
Study 2: The 0.3 mg/mL samples in IV bags recorded a higher pH than those in Study 1, with a mean pH of 6.17 across the study when stored refrigerated for 21 days plus 24 hours at 25°C/60%RH, however, the 0.3 mg/mL samples had a lower average pH when stored in INTERMATE® pumps (mean pH5.78), see Figure 1B. The 0.8 mg/mL and 4 mg/mL samples in IV bags and the 4 mg/mL sample in INTERMATE® pumps all remained close to pH 6.10 throughout 76 days refrigerated storage plus 48 hours at 25°C/60%RH (mean of pH 6.12, pH 6.15 and pH 6.10, respectively, across all time points), however, the pH of the 0.8 mg/mL sample stored in INTERMATE® pumps was noticeably lower with a mean of pH 5.88 across the time points, see Figure 1C.
The overall observed results of the two studies would indicate that storage of low concentrations of trastuzumab in INTERMATE® pumps in this case 0.3 mg/mL to 0.8 mg/mL, does result in a reduction of the pH of the samples, which may be due to the reduced capacity of the excipients to buffer the pH effects of the INTERMATE® pump device upon interaction with the drug solution. The pH of 0.3 mg/mL, 0.8 mg/mL and 4 mg/mL samples did not vary significantly from their respective initial pH’s at T0, regardless of container, with the average pH (n = 3) of each sample type remaining within 0.24 pH units of T0 at the final time point.
Monitoring of monomer content by SEC-HPLC
SEC-HPLC analysis detected the trastuzumab monomer peak with a retention time (Rt) of approximately 10.1 mins in all sample and standard chromatograms, with minor peaks detected at 8.4 mins, attributed to the dimer, and 15.6 mins, which was identified as the excipient histidine. Any secondary peaks detected were monitored as potential HMW or LMW products throughout the study and calculated as a percentage of total peak area (excluding the histidine peak area). Analysis of the forced degraded (aged) KANJINTI™ (trastuzumab) samples showed signs of progressive degradation with increased exposure times to ambient conditions, indicated primarily by a reduction in monomer and concurrent increase in secondary peak areas for HMW and LMW products, see Figure 2A and Table 2, demonstrating the stability indicating ability of the method. In contrast, the monomer represented on average 99.08% ± 0.16% in all test samples, regardless of concentration, container or study length. A summary of the monomer, HMW and LMW content and trastuzumab concentration in Study 1 and 2 samples are shown in Tables 3 and 4, respectively. Example chromatograms from the final time point of the 78-day study are presented as a worst case with regards to study duration, overlaid with the chromatogram of freshly prepared reference standard for comparison in Figure 2B, indicating no additional peaks or evolution of HMW or LMW products following 6 hours at RT + 76 days at 2°C–8°C + 48 hours at 25°C/60%RH.
Trastuzumab concentration by SEC-HPLC
To monitor the potential adsorption of trastuzumab onto the container walls, the monomer concentration was assessed at each time point and remained within 98.72%–101.90% of the initial concentration for samples, regardless of starting concentration, container or study duration, see Tables 3 and 4.
Monitoring of aggregation by SEC-HPLC
A minimum peak area equivalent to 0.05% of the initial trastuzumab monomer peak area (at T0) in each sample type was applied; any secondary peaks with an area less than this for each standard and sample chromatogram were disregarded.
Study 1: The only HMW peak detected in the reconstituted KANJINTI™ (trastuzumab) 21 mg/mL solutions stored in 50 mL VIAFLO® bags and the diluted 0.3 mg/mL and 4 mg/mL samples prepared from the multi-dose bags was that attributed to the dimer, which remained consistent in the 21 mg/mL multi-dose bags throughout 63 days storage at 2°C–8°C, accounting for ≤1.04% of the total peak area in all three bags and increasing by no more than 0.13% from the initial content. The level of dimer decreased from the initial content at T = Day 0 in all 0.3 mg/mL products following 4 days storage at 2°C–8°C plus 24 hours at 25°C/60%RH (maximum 0.09% decrease detected) and remained consistent in 4 mg/mL products (maximum 0.02% increase detected). The average HMW content of three containers tested in each study is summarised in Table 3.
Study 2: The only HMW peak detected in 0.8 mg/mL and 4 mg/mL test samples following 76 days storage at 2°C–8°C plus 48 hours at 25°C/60%RH was that attributable to the dimer, which increased from the initial content at T = Day 0 by ≤0.06% in 0.8 mg/mL samples and by ≤0.13% in all 4 mg/mL samples, regardless of container, following 76 days storage at 2-8°C plus 48 hours at 25°C/60%RH. In addition to the peak considered as the dimer (Rt = 8.4 mins), an additional peak was detected at Rt = 6.4 mins in 0.3 mg/mL sample chromatograms at time points T7 and T14 only, that represented ≤0.11% of the total peak area. The HMW products detected in KANJINTI™ (trastuzumab) 0.3 mg/mL in 0.9% w/v NaCl samples remained consistent throughout 21 days storage at 2°C–8°C plus 24 hours at 25°C/60%RH, accounting for ≤0.93% of the total peak area and remaining within ± 0.16% of initial HMW content, regardless of container. The average HMW content of three containers tested in each study is summarized in Table 4.
Monitoring of fragmentation by SEC-HPLC
A minimum peak area equivalent to 0.05% of the initial trastuzumab monomer peak area (at T0) in each sample type was applied; any secondary peaks with an area less than this for each standard and sample chromatogram were disregarded. The histidine peak area was monitored and remained consistent (with a mean range of 3.66%–3.73% during the longest storage period of 78 days for 0.8 mg/mL and 4 mg/mL strengths in both IV bags and INTERMATE® pumps). The area of any LMW peaks (excluding histidine) were combined and expressed as a percentage of the total peak area.
Study 1: No LMW products with peak areas exceeding the applied minimum area were detected in any of the KANJINTI™ (trastuzumab) 21 mg/mL reconstituted solutions stored in 50 mL VIAFLO® bags throughout 63 days storage at 2°C–8°C. LMW products were only detected in 0.3 mg/mL samples diluted from 63 day stored multi-dose bag and remained consistent with no more than 0.08% detected at T0 or following 4 days storage at 2°C–8°C plus 25°C/60%RH in any of the three bags. The average LMW content of three containers tested in each study is summarised in Table 3.
Study 2: The highest level of LMW products was detected in 0.8 mg/mL products stored in INTERMATE® pumps; however, this was never more than 0.30% throughout the duration of the study in any of the three devices. LMW products accounted for less than 0.11% in 0.8 mg/mL KANJINTI™ (trastuzumab) bags and less than 0.07% in 4 mg/mL samples, regardless of container, following 76 days storage at 2°C–8°C plus 48 hours at 25°C/60%RH. No LMW products with peak areas exceeding the applied minimum area were detected in KANJINTI™ (trastuzumab) 0.3 mg/mL in 0.9%w/v NaCl when stored in VIAFLO® bags or INTERMATE® pumps throughout 21 days storage at 2°C–8°C, plus additional 24 hours at 25°C/60%RH. The average LMW content of three containers tested in each study is summarized in Table 4.
Purity by NR-CGE
Fragmentation of trastuzumab in the system suitability sample resulted in the intact antibody (2-Heavy-2-Light chains; 2H2L) being well resolved from impurities, such as the Light chain (L), Heavy chain (H), Heavy-Light chain (HL), Heavy-Heavy chain (HH) and 2-Heavy-1-Light chain (HHL), see Figure 3B. These impurities were used as markers for the detection of fragments in the KANJINTI™ (trastuzumab) test samples. A progressive decrease in intact trastuzumab (2H2L) content and an increase in detected fragments in the test samples would have been indicative of degradation, as demonstrated in the aged KANJINTI™ (trastuzumab) samples, see Figure 3A and Table 2, however no such trend was observed; the NR-CGE profile at each time point was comparable with that at the initial time point, indicating no significant degradation of the drug throughout the duration of the study. The average initial and final content of LMW degradation products and monomer of the three containers tested in each study is summarized in Table 5 with representative electropherograms in Figure 3.
Study 1: The 2H2L content in all reconstituted KANJINTI™ (trastuzumab) 21 mg/mL solutions stored in 50 mL VIAFLO® bags remained ≥95.3% in each of the three bags at each time point and was comparable to the level detected in the standard (≥95.7%). The 2H2L content in all 0.3 mg/mL and 4 mg/mL samples diluted from the concentrated stock bags remained ≥95.8% following 4 days storage at 2°C–8°C plus 24 hours at 25°C/60%RH, regardless of the age of the stock bag it was prepared from.
Study 2: There was no detectable loss in purity of trastuzumab in KANJINTI™ 0.8 mg/mL and 4 mg/mL samples stored refrigerated for 76 days plus 48 hours at 25°C/60%RH, with 2H2L content remaining above 96.2% in both VIAFLO® bags and INTERMATE® pumps at the final time point, comparable to the reference standard (96.4%). The 2H2L content in KANJINTI™ (trastuzumab) 0.3 mg/mL products remained ≥93.0% at each time point and was comparable to the level detected in the standard (≥94.7%).
Purity by RED-CGE
CGE was performed under reducing conditions for determination of purity of the heavy (H) and light (L) chains, measured as the sum of H+L. RED-CGE analysis of the aged system suitability sample indicated a reduction in the % Peak Area of the H chain, with additional peaks of higher molecular weight (HMW), one of which was below the level of detection in the Control (freshly prepared) sample, resulting in a decrease in the % Purity (H+L) and H:L ratio, see Table 2 and Figure 4, demonstrating the stability-indicating ability of the reducing CGE system. In contrast, the RED-CGE profile of the test samples at each time point was comparable with the initial profile at the respective T0, indicating no significant degradation of the drug throughout the duration of the study. The average % purity of three containers tested in each study is summarized in Table 5 with example electropherograms in Figure 4.
Study 1: The purity in each KANJINTI™ (trastuzumab) 21 mg/mL reconstituted solution stored in 50 mL VIAFLO® bags was ≥98.0% for the duration of the study and was comparable to that detected in the standard (≥97.7%), remaining within 1.2% of the initial content at T0 following 63 days refrigerated storage. A loss in purity of no more than 1.2% was observed in all three 0.3 mg/mL samples diluted from the concentrated stock bags following 4 days storage at 2°C–8°C plus 24 hours at 25°C/60%RH, regardless of the age of the stock bag it was prepared from; a maximum 2.5% loss in purity was detected in 4 mg/mL bags, which had been prepared from the 63-day stored concentrated stock bag. The H+L purity in 4 mg/mL bags prepared from 22-day and 42-day old-concentrated stock bags remained within 1.8% of the initial content after 4 days storage at 2°C–8°C plus 24 hours at 25°C/60%RH.
Study 2: The purity of H+L chains in each 0.8 mg/mL and 4 mg/mL sample was ≥97.5% at the final time point (T = 76 hours + 48 hours) and was comparable to that detected in the standard, which remained ≥97.4% at each time point; all samples remained within 0.9% of the initial purity in both IV bags and INTERMATE® pumps at the final time point. There was no detectable loss in purity in 0.3 mg/mL samples over 21 days refrigerated storage plus 24 hours at 25°C/60%RH, which remained within 1.6% of the initial purity at each point.
Charge variant analysis by CZE
CZE was used to evaluate the distribution of charged variants, with peaks grouped as basic, main or acidic variants. Analysis of the aged sample, exposed to ambient temperature and daylight for 27 days to induce degradation, demonstrated an 11.1% reduction in main peak with a concurrent 12.3% increase in acidic charge variants, see Table 2 and Figure 5. These results agree with those of Vieillard et al. 2018 for another trastuzumab biosimilar, which showed a significant increase in acidic variants following 28 days storage at 22°C, detected by weak cation exchange chromatography . For the KANJINTI™ (trastuzumab) samples under test, the charge profile of each demonstrated no significant change in the % content of main, basic or acidic charge variants, and remained consistent throughout the duration of each study with the profile obtained at the initial time point, regardless of the storage container. The average % basic, main and acidic variants of three containers tested in each study is summarized in Table 6 with example electropherograms in Figure 5.
Study 1: The average main peak content for the three bags (77.87%) following 63-day refrigerated storage of the reconstituted KANJINTI™ (trastuzumab) 21 mg/mL solutions stored in 50 mL VIAFLO® bags was comparable to the average initial content at T0 (77.24%), with no significant changes to the acidic or basic variants, see Table 6. The main peak in each 0.3 mg/mL and 4 mg/mL sample diluted from the concentrated stock bags did not decrease by more than 2.1% following 4 days storage at 2°C–8°C plus 24 hours at 25°C/60%RH, regardless of the age of the stock bag it was prepared from.
Study 2: There was no detectable loss in trastuzumab main peak in KANJINTI™ 0.8 mg/mL and 4 mg/mL samples in VIAFLO® or INTERMATE® pumps with an average maximum 1.51% decrease in % main peak observed following 76 days refrigerated storage plus 48 hours at 25°C/60%RH; the main peak content remained ≥76.8% at each time point regardless of container, comparable to that in freshly prepared standard (≥77.8% at each time point). Similarly, there was no significant loss in main peak in 0.3 mg/mL stored in VIAFLO® or INTERMATE® pumps following 21 days refrigeration plus 24 hours at 25°C/60%RH, with an average maximum 0.79% reduction.
Sub-visible particle count analysis
The quantification of sub-visible particles is important for ensuring the quality and safety of therapeutic protein preparations, since the presence of mobile undissolved particles can pose a danger to patients receiving the drug. With the exception of the reconstituted KANJINTI™ (trastuzumab) 21 mg/mL solutions stored in 50 mL VIAFLO® bags, particles >10 μm and >25 μm were quantified in all 0.3 mg/mL, 0.8 mg/mL and 4 mg/mL KANJINTI™ (trastuzumab) samples at the initial, mid (where applicable) and final time point of each study and are summarized in Figure 6. All products complied with the limits stated in USP<787> for sub-visible particulate matter in therapeutic protein injections and in British Pharmacopoeia (BP) 2019 Appendix XIII A: Particulate contamination: Sub-visible particles (Ph. Eur. method 2.9.19) for solutions for infusion or solutions for injection supplied in containers with a nominal content of 100 mL or less (≤6,000 per container equal to or greater than 10 μm and ≤600 per container equal to or greater than 25 μm) [16, 17].
Bioactivity by inhibition of cell proliferation bioassay
The bioassay was performed on initial (T0) and final time point samples taken for each set of KANJINTI™ (trastuzumab) test samples. The determined % Relative Potency results were calculated relative to the % bioactivity obtained at the initial time point (T0), which was designated as 100%, to identify any significant change in biological activity following the extended storage periods. There were no significant changes in the % bioactivity in any of the KANJINTI™ (trastuzumab) test samples across all concentrations and containers following the various storage durations. The mean potency of three containers in each set of samples is presented in Table 7.
Study 1: The biological potency of the concentrated stock bags of reconstituted KANJINTI™ (trastuzumab) 21 mg/mL solutions stored refrigerated for 63 days was consistent with the initial potency across all three bags (100%–102%). Diluted 0.3 mg/mL and 4 mg/mL samples, prepared from 63-day refrigerated concentrated stock bag of reconstituted KANJINTI™ (trastuzumab) 21 mg/mL solution, were assessed as they represented the greatest stability challenge with regards to storage duration and each sample maintained 89%-97% of the initial potency following 4 days storage at 2°C–8°C plus 24 hours at 25°C/60%RH.
Study 2: There was a consistent biological potency in KANJINTI™ (trastuzumab) 0.8 mg/mL and 4 mg/mL samples in VIAFLO® or INTERMATE® pumps stored for 76 days at 2°C–8°C plus 48 hours at 25°C/60%RH, with all samples retaining 93%–107% of their respective initial potency, and 0.3 mg/mL samples retaining 97%–110% potency following 21 days refrigeration plus 24 hours at 25°C/60%RH.
This study has used a range of analytical techniques to evaluate the stability of KANJINTI™, a trastuzumab biosimilar, to address the requirements of different global pharmacy practices: Study 1 was designed to assess the stability of reconstituted solution (21 mg/mL) when stored refrigerated in 50 mL multi-dose bags, and following subsequent dilution in 0.9% w/v NaCl for shorter term storage in polyolef in bags at f inal concentrations of 0.3 mg/mL and 4 mg/mL; Study 2 assessed the stability of KANJINTI™ (trastuzumab) 0.3 mg/mL, 0.8 mg/mL and 4 mg/mL in 0.9% w/v NaCl solutions when stored in polyolef in IV bags and ambulatory devices. All studies included a 6-hour storage period at RT (17°C–23°C) following initial sampling for T0 analysis and prior to refrigeration to cover the timeframe and conditions that products may be subjected to during preparation/handling, prior to use. Diluted KANJINTI™ (trastuzumab) products were subjected to 24 hours to 48 hours storage at 25°C/60%RH at the end of the refrigeration storage period to allow assessment of stability at the in-use temperature they will be administered and provide data for evaluating the effect of temperature excursions. Products were prepared aseptically in a hospital aseptic manufacturing unit so that the acquired stability data represented the manufacturing processes that would typically be used.
Forced-degraded samples are often used to demonstrate the stability-indicating ability of analytical techniques employed, however, the conditions used to degrade the sample, e.g. dramatic change in pH, temperature or oxygen level, may have an unrepresentative effect on the molecular structure of proteins . This study utilized KANJINTI™ (trastuzumab) 21 mg/mL reconstituted solutions, exposed to ambient conditions (17°C–23°C and natural daylight) for extended periods of time prior to dilution with 0.9% w/v NaCl, to challenge the stability-indicating nature of the analytical methods. These ‘aged’ products were representative of the ‘natural’ degradation routes followed by the trastuzumab molecule when stored for extended periods outside of the recommended storage conditions (2°C–8°C and protected from light), demonstrating the progressive degradation that occurs in unfavourable storage conditions. Changes were detected after just 27 days exposure, notably increased aggregation and fragmentation with concurrent reduction in monomer as detected by SEC, increased fragmentation detected by NR-CGE, a decrease in % purity of heavy and light chains detected by RED-CGE, and altered distribution of charge variants detected by CZE, resulting in increased acidic variants, likely due to deamidation which is considered as a common degradation pathway for proteins . An increase in acidic variants at 22°C has been detected in another trastuzumab biosimilar (Herzuma®) . Previous studies on stability of the trastuzumab originator (Herceptin®) have indicated ready-to-administer infusion solutions (0.4 mg/mL–4 mg/mL) stored in polypropylene bags are stable for 28 days when stored at room temperature without light protection  and in polyolef in bags at 0.8 mg/mL–2.4 mg/mL for 6 months at 20°C ± 2°C, protected from light , with no evidence of physicochemical instability. The changes to the trastuzumab molecule stored at ‘ambient’ temperatures and exposed to natural daylight in the present study have occurred in the concentrated 21 mg/mL reconstituted solution, in the presence of undiluted excipients and demonstrate that room temperature and the effects of light exposure should not be underestimated.
The production of multi-dose bags of concentrated drug, supplied as pharmacy bulk packs to hospitals for dilution in making patient-specific doses, is not a widely used practice; however, this study has provided evidence that the reconstituted solution retains its physicochemical properties and biological activity following 63 days storage at 2°C–8°C and following dilution to 0.3 mg/mL and 4 mg/mL in 0.9% w/v NaCl IV bags, stored refrigerated for 4 days plus 24 hours at 25°C/60%RH.
The use of solutions from previously pierced vials is not a recommended practice in the NHS in the UK. We had previously determined the stability of reconstituted KANJINTI™ (trastuzumab) (21 mg/mL) stored in the vial following 11 days storage at 2°C–8°C, protected from light (unpublished data) and the stability of 0.3 mg/mL–4 mg/mL KANJINTI™ (trastuzumab) product in 0.9% w/v NaCl was further challenged by using 11-day-old reconstituted solutions stored in pierced vial for their preparation. Whereas the stability of 0.8 mg/mL–4 mg/mL products was assessed over a total of 78 days, the stability assessment of 0.3 mg/mL solutions was limited to a total of 22 days since it has been stated that 0.3 mg/mL KANJINTI™ (trastuzumab) solutions are rarely used clinically  and there is a tendency for lower concentrations of biological molecules to be less stable, likely related to dilution of stabilizing excipients . The stability of KANJINTI™ (trastuzumab) 0.3 mg/mL–3.8 mg/mL in 0.9% w/v NaCl IV bags for 35 days at 2°C–8°C has previously been reported , the current study has provided additional stability data for this concentration range by including storage in INTERMATE® pumps, allowing the option of ambulatory infusion therapy.
The most obvious differences between the drug presentations were in the pH of the lower dose samples stored in INTERMATE® pumps; the pH of 0.3 mg/mL and 0.8 mg/mL solutions stored in INTERMATE® pumps were lower compared with storage in IV bags (maximum difference of 0.45 units and 0.26 units, respectively), whereas 4 mg/mL solutions returned a similar pH regardless of container (max. difference of 0.07 units). The lower pH is likely due to the reduced capacity of the excipients in lower doses (due to dilution) to buffer the pH effects of the INTERMATE® pump upon interaction with the drug solution, this seemingly had no effect on stability since the pH of lower dose samples did not vary significantly from their respective initial pH at T0, regardless of container, and no sign of instability was detected by the other analytical methods. There was no significant change (defined as 0.5 pH unit; ) in the pH of any of the tested solutions over the respective storage periods.
There was no change in trastuzumab monomer concentration in any of the samples regardless of dilution, container or study length indicating no adsorption of the drug to the containers. This is particularly pertinent for the KANJINTI™ (trastuzumab) solutions stored in the INTERMATE® pumps, since the protein is in contact with different materials to those stated to be compatible in the SmPC , including the elastomeric balloon (polyisoprene) and tubing, providing supporting data for the absence of drug-container interaction when storing monoclonal antibodies in these ambulatory devices. The combined data from SEC and CGE indicated that there was no evidence of aggregate formation or fragmentation in any of the solutions during the storage periods, whilst CZE detected no significant changes in the charge variant distribution, suggesting that there had been no chemical modification leading to degradation. Sub-visible particles in all solutions and containers complied with the Ph. Eur. method 2.9.19 limits  whilst the bioassay data demonstrated that the extended storage periods did not affect the biological potency of the KANJINTI™ (trastuzumab) preparations.
A limitation to the present study is that transport simulation was not performed, however the effect of mechanical stress to simulate transportation has been reported for KANJINTI™ (trastuzumab) infusion products in IV bags prepared at similar concentrations to this study (0.3 mg/mL–3.8 mg/mL)  with no adverse effect on stability. The nature of the INTERMATE® pumps would result in less agitation of the solution within the elastomeric balloon, suggesting mechanical stress may have less effect on solutions stored in these devices. Microbiological stability, aseptic processes, transport processes and associated risks should be independently assured by the user. The lack of data to detect particles in the 0.1 μm–1μm range is also considered a limitation of the study, since submicronic particles can reflect early signs of protein destabilization and the beginning of aggregation. Sub-visible protein particles in the 0.1 μm–10 μm, as well as those >10 μm, have the potential to impact the safety and efficacy of a product over its shelf life . Despite the characterization gap for submicron particles in the 0.1 μm–1 μm range, SEC analysis, which can characterize soluble aggregates in the range of 10 nm–100 nm , did not indicate any evolution of dimer or aggregate formation. The sub-visible particle counts in the 2 μm–5 μm range were also monitored by light obscuration, which detected varying numbers throughout the different storage durations (supplementary data). There was no obvious or consistent trend although the most variability was associated with the lower 0.3 mg/mL concentrations; variability was also observed in the control containers containing 0.9% w/v NaCl diluent only.
The present study has provided additional stability data on the trastuzumab biosimilar KANJINTI™ when prepared in both concentrated multi-dose bags and following dilution and extended storage in IV bags and elastomeric devices. Extended shelf lives based on stability data should be as short as practicable , however, the extended stability data provides storage options that allow the infusions to be prepared in advance under controlled and validated aseptic conditions, contributing to increased patient safety and a reduction in drug waste. The stability demonstrated in the portable elastomeric device may provide the option to treat patients outside of the hospital environment, reducing the need for hospital admission.
The combined data from a range of stability-indicating analytical methods has demonstrated the in-use physicochemical stability and bioactivity of the trastuzumab biosimilar KANJINTI™ when prepared in controlled validated aseptic conditions and stored for extended periods, in both concentrated multi-dose bags (21 mg/mL) and following dilution in IV bags and elastomeric devices (0.3 mg/mL–4 mg/mL), to address the stability requirements of different global pharmacy practices.
Drugs often have to be diluted to prepare the correct dose to give to a patient and it is important to ensure that the diluted drug does not deteriorate during storage. This study has tested the quality of the drug KANJINTI™ (trastuzumab) before and after it has been diluted and stored for different lengths of time in different containers. The results indicated that KANJINTI™ (trastuzumab) remains stable at both high and low doses that are commonly used after storage in a fridge and during a period of time at room temperature. This means that the drug infusion can be prepared in advance and stored refrigerated until required, reducing cost and saving clinician time. As well as being stable in infusion bags, the study has indicated that the drug is stable in a portable elastomeric device that may allow patients to be treated outside of the hospital environment; this may provide clinicians and patients with increased treatment options.
The authors would like to thank the Royal Liverpool and Broadgreen University Hospitals NHS Trust (RLBUHT) Pharmacy Aseptic Production Unit for preparation of samples and Kristen Elson (Amgen, Thousand Oaks, CA, USA) for providing guidance and direction throughout the study.
This study was funded by Amgen Inc.
Competing interests: Jolene Teraoka, Jill Crouse-Zeineddini and Jane Hippenmeyer are Amgen employees and stockholders. Sarah Elizabeth Lee is an employee of Baxter Healthcare. Quality Control North West Liverpool is a hosted service of Liverpool University Hospitals NHS Foundation Trust. The testing performed by Quality Control North West Liverpool was funded by Amgen Inc.
Provenance and peer review: Not commissioned; externally peer reviewed.
Lyndsay Davies1, PhD
Katie Milligan1, BSc
Mark Corris1, BSc
Ian Clarke1, Medical Technical Officer
Paul Dwyer1, MSc
Sarah Elizabeth Lee2, PhD
Jolene Teraoka3, BSc
Jill Crouse-Zeineddini3, PhD
Jane Hippenmeyer4, PharmD
1Quality Control North West – Liverpool, Pharmacy Practice Unit, 70 Pembroke Place, Liverpool L69 3GF, UK
2Baxter Healthcare Corporation, 25212 IL-120, Round Lake, IL 60073, USA
3Amgen Inc. Attribute Sciences, Thousand Oaks, CA 91320, USA
4Amgen (Europe) GmbH, 22 Suurstoffi, CH-6343 Rotkreuz, Switzerland
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Author for correspondence: Lyndsay Davies, PhD, Senior Pharmaceutical Biochemistry Analyst, Quality Control North West – Liverpool, Pharmacy Practice Unit, 70 Pembroke Place, Liverpool L69 3GF, UK
Disclosure of Conflict of Interest Statement is available upon request.
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