Method Validation and Measurement of Biomarkers in Nonclinical and Clinical Samples in Drug Development: A Conference Report

Immune Reconstitution Profiling Suggests Antiviral Protection After Transplantation with Omidubicel: a Phase 3 Substudy

BACKGROUND

Allogeneic hematopoietic cell transplantation (HCT) is a potentially curative treatment for hematological malignancies and non-malignant disorders. Rapid immune reconstitution (IR) following allogeneic HCT has been shown to be associated with improved clinical outcomes and lower infection rates. A global phase 3 trial (NCT02730299) of omidubicel, an advanced cell therapy manufactured from an appropriately human leukocyte antigen-matched single umbilical cord blood (UCB) unit, showed faster hematopoietic recovery, reduced rates of infection, and shorter hospitalizations in patients randomized to omidubicel compared with those randomized to standard UCB.

OBJECTIVE

This optional, prospective substudy of the phase 3 trial characterized the IR kinetics following HCT with omidubicel compared with UCB in a systematic and detailed manner.

STUDY DESIGN

In this substudy, 37 patients from 14 global sites were included (omidubicel: n=17, UCB: n=20). Peripheral blood samples were collected over 10 predefined time points from 7 to 365 days post-HCT. Flow cytometry immunophenotyping, T cell receptor excision circle quantification, and T cell receptor sequencing were employed to evaluate the longitudinal IR kinetics post-transplant and their association with clinical outcomes.

RESULTS

Patient characteristics in the two comparator cohorts were overall statistically similar, except for age and total body irradiation (TBI) based conditioning regimens. The median age (range) for patients who received omidubicel or UCB was 30 (13-62) years and 43 (19-55) years, respectively. The percentages of patients receiving TBI based conditioning regimens were 47% and 70% for omidubicel and UCB recipients, respectively. Graft characteristics differed in their cellular composition. Omidubicel recipients received a 33-fold higher median dose of CD34+ stem cells, while receiving one third of the median CD3+ lymphocyte dose infused to UCB transplanted patients. Compared with UCB, omidubicel recipients exhibited faster IR of all measured lymphoid and myelomonocytic subpopulations, predominantly in the first 14 days post-transplant. This effect involved circulating natural killer (NK) cells, helper T cells, monocytes, and dendritic cells, with superior long-term B cell recovery from Day 28. One-week post-HCT, omidubicel recipients exhibited 4.1 and 7.7 -fold increases in the median helper T and NK cell counts respectively, compared to their UCB transplanted counterparts. By three weeks post-HCT, omidubicel transplanted patients were 3-fold more likely to achieve clinically relevant helper T and NK cell counts of 100 cells/ µL or above. Similar to UCB, omidubicel yielded a balanced cellular subpopulation composition and diverse T cell receptor repertoire in the short to long term. Omidubicel's CD34+ cell content correlated with faster IR by Day 7 post-HCT, which in turn coincided with earlier hematopoietic recovery. Lastly, early NK and helper T cell reconstitution correlated with a decreased rate of post-HCT viral infections, suggesting a plausible explanation for this phenomenon among omidubicel recipients in the phase 3 study.

CONCLUSIONS

Our findings suggest that omidubicel efficiently promotes IR across multiple immune cells, including CD4+ T cells, B cells, NK cells, and dendritic cell subtypes as early as 7 days post-transplant, potentially endowing recipients of omidubicel with early protective immunity.

DLL3 regulates Notch signaling in small cell lung cancer

Tumor heterogeneity plays a critical role in tumor development and response to treatment. In small-cell lung cancer (SCLC), intratumoral heterogeneity is driven in part by the Notch signaling pathway, which reprograms neuroendocrine cancer cells to a less/non-neuroendocrine state. Here we investigated the atypical Notch ligand DLL3 as a biomarker of the neuroendocrine state and a regulator of cell-cell interactions in SCLC. We first built a mathematical model to predict the impact of DLL3 expression on SCLC cell populations. We next tested this model using a single-chain variable fragment (scFv) to track DLL3 expression in vivo and a new mouse model of SCLC with inducible expression of DLL3 in SCLC tumors. We found that high levels of DLL3 promote the expansion of a SCLC cell population with lower expression levels of both neuroendocrine and non-neuroendocrine markers. This work may influence how DLL3-targeting therapies are used in SCLC patients.

Biomarker context-of-use: how organizational design can impact the implementation of the appropriate biomarker assay strategy

Since 2011, the European Bioanalysis Forum has been discussing the topic of context-of-use for biomarker assays, in support of a cross-industry implementation of its principles. The discussions have led to the acknowledgement of the challenges that we face as an industry in implementing these principles. In addition to scientific recommendations, the European Bioanalysis Forum has addressed these challenges by providing recommendations on organizational design, and what works in both sponsor and contract research organizations, to support and enable context-of-use across biomarker strategies. Here, we highlight the key considerations for organizational design to help ensure that biomarker assays are characterized and validated according to the right context-of-use, to ensure that the right decisions based on the biomarker data can be made during drug development.

An antibody-free platform for multiplexed, sensitive quantification of protein biomarkers in complex biomatrices

Sensitive, multiplexed protein quantification remains challenging despite recent advancements in LC-MS assays for targeted protein biomarker quantification. High-sensitivity protein biomarker measurements usually require immuno-affinity enrichment of target protein; a process which is highly dependent on capture reagent and limited in capability to measure multiple analytes. Herein, we report a novel antibody-free platform, which measures multiple biomarkers from complex matrices employing a strategically optimized solid-phase extraction cleanup and orthogonal multidimensional LC-MS. Eight human protein biomarkers with different specifications were spiked into canine plasma as a model investigation system. The developed strategy achieved the desired sensitivity, robustness, and throughput via the following steps: (1) post digestion mixed-mode cation exchange-reverse phase SPE enrichment cleaned up the sample initially; (2) rapid, high-pH peptide fractionation further eliminated background components efficiently while selectively enriched signature peptides (SP) to provide sufficient sensitivity for multiple targets; and (3) trapping-micro-LC-MS analysis delivered high sensitivity comparable to a nano-LC-MS method but with much better robustness and throughput for the final analysis. Compared with a conventional LC-MS assay with direct protein digestion and limited clean-up, analysis with this antibody-free platform improved the LLOQ by 1-2 orders of magnitude for the eight protein biomarkers, reaching as low as 5 ng/mL in plasma, with feasible robustness and throughput. This platform was applied for the quantification of biomarkers of respiratory conditions in patients with various lung diseases, demonstrating real-world applicability.

Biomarker Assay Validation by Mass Spectrometry

Decades of discussion and publication have gone into the guidance from the scientific community and the regulatory agencies on the use and validation of pharmacokinetic and toxicokinetic assays by chromatographic and ligand binding assays for the measurement of drugs and metabolites. These assay validations are well described in the FDA Guidance on Bioanalytical Methods Validation (BMV, 2018). While the BMV included biomarker assay validation, the focus was on understanding the challenges posed in validating biomarker assays and the importance of having reliable biomarker assays when used for regulatory submissions, rather than definition of the appropriate experiments to be performed. Different from PK bioanalysis, analysis of biomarkers can be challenging due to the presence of target analyte(s) in the control matrices used for calibrator and quality control sample preparation, and greater difficulty in procuring appropriate reference standards representative of the endogenous molecule. Several papers have been published offering recommendations for biomarker assay validation. The situational nature of biomarker applications necessitates fit-for-purpose (FFP) assay validation. A unifying theme for FFP analysis is that method validation requirements be consistent with the proposed context of use (COU) for any given biomarker. This communication provides specific recommendations for biomarker assay validation (BAV) by LC-MS, for both small and large molecule biomarkers. The consensus recommendations include creation of a validation plan that contains definition of the COU of the assay, use of the PK assay validation elements that support the COU, and definition of assay validation elements adapted to fit biomarker assays and the acceptance criteria for both.

Best practices for the development and fit-for-purpose validation of biomarker methods: a conference report

This conference report summarized a full-day workshop, “best practices for the development and fit-for-purpose validation of biomarker methods,” which was held prior to the American Association of Pharmaceutical Scientists (AAPS) PharmSci360 Congress, San Antonio, TX, November 2019. The purpose of the workshop was to bring together thought leaders in biomarker assay development in order to identify which assay parameters and key statistical measures need to be considered when developing a biomarker assay. A diverse group of more than 40 scientists participated in the workshop. The workshop and subsequent working dinner stimulated robust discussion. While a consensus on best practices was not achieved, some common themes and major points to consider for biomarker assay development have been identified and agreed on. The focus of this conference report is to summarize the presentations and discussions which occurred at the workshop. Biomarker assay validation is a complex and an evolving area with discussions ongoing.

Evaluation of a fit-for-purpose assay to monitor antigen-specific functional CD4+ T-cell subpopulations in rheumatoid arthritis using flow cytometry-based peptide-MHC class-II tetramer staining

Antigen-specific T cells can serve as a response biomarker in non-clinical or clinical immunotherapy studies in autoimmune disease. There are protocols with optimized multimer staining methods to detect peptide (p)MHCII+ CD4+ T cells, and some qualified and validated protocols for pMHCI+ CD8+ T cells. However, no protocol is fully or partially qualified to enumerate and characterize antigen-specific pMHCII+ CD4+ T cells from patient samples. Implementing such an assay requires a desired level of specificity and precision, in terms of assay repeatability and reproducibility. In transgenic type II collagen (CII)-immunized HLA-DR1/DR4 humanized mouse models of collagen-induced arthritis (CIA), CII259-273-specific T cells dominantly expand. Therefore antigen-specific T cells recognizing this epitope presented by rheumatoid arthritis (RA)-associated risk HLA-DR allomorphs are of interest to understand disease progression and responses to immunotherapy in RA patients. Using HLA-DRB1∗04:01 or ∗01:01-collagen type II (CII)259-273 tetramers, we evaluated parameters influencing precision and reproducibility of an optimized flow cytometry-based method for antigen-specific CD4+ T cells and eight specific subpopulations with and without tetramer positivity. We evaluated specificity, precision, and reproducibility for research environments and non-regulated laboratories. The assay has excellent overall precision with %CV<25% for intra-assay repeatability, inter-analyst precision, and inter-assay reproducibility. The precision of the assay correlated negatively with the cell viability after thawing, indicating that post-thaw viability is a critical parameter for reproducibility. This assay is suitable for longitudinal analysis of treatment response and disease activity outcome in RA patients, and adaptable for translational or immunotherapy clinical trial settings.

Development of a Flow Cytometry Assay to Predict Immune Checkpoint Blockade-Related Complications

Treatment of advanced melanoma with combined immune checkpoint inhibitor (ICI) therapy is complicated in up to 50% of cases by immune-related adverse events (irAE) that commonly include hepatitis, colitis and skin reactions. We previously reported that pre-therapy expansion of cytomegalovirus (CMV)-reactive CD4⁺ effector memory T cells (T_EM) predicts ICI-related hepatitis in a subset of patients with Stage IV melanoma given αPD-1 and αCTLA-4. Here, we develop and validate a 10-color flow cytometry panel for reliably quantifying CD4⁺ T_EM cells and other biomarkers of irAE risk in peripheral blood samples. Compared to previous methods, our new panel performs equally well in measuring CD4⁺ T_EM cells (agreement = 98%) and is superior in resolving CD4⁺ CD197⁺ CD45RA^- central memory T cells (T_CM) from CD4⁺ CD197⁺ CD45RA⁺ naive T cells (T_naive). It also enables us to precisely quantify CD14⁺ monocytes (CV = 6.6%). Our new “monocyte and T cell” (MoT) assay predicts immune-related hepatitis with a positive predictive value (PPV) of 83% and negative predictive value (NPV) of 80%. Our essential improvements open the possibility of sharing our predictive methods with other clinical centers. Furthermore, condensing measurements of monocyte and memory T cell subsets into a single assay simplifies our workflows and facilitates computational analyses.

A novel hydrophilic interaction chromatography assay characterization of 4-pyridoxic acid, an emergent renal organic anion transporter 1/3 transporter biomarker

Aim: 4-pyridoxic acid (PDA) has been proposed as an endogenous biomarker for renal organic anion transporter 1/3 (OAT1/3) inhibition. Clinical data are needed to support the proposal. Materials & methods: A hydrophilic interaction chromatography (HILIC)-LC/MS/MS assay was developed and characterized to support clinical drug-drug interaction (DDI) studies. Results: A HILIC-LC/MS/MS assay was successfully developed. PDA was measured in two clinical DDI studies; one where no significant OAT1/3 inhibition was observed and a second where a known inhibitor of the transporter was dosed. In both clinical studies, PDA plasma concentrations correlate to OAT1/3 function. Conclusion: The analysis of study samples from two clinical DDI studies using a HILIC-LC/MS/MS assay contributes further evidence that PDA is an endogenous biomarker for OAT1/3 inhibition.

Calibrator material selection: a key criteria during biomarker assay method development

Biomarker assay method development is a multistep rigorous process and calibrant material selection is integral to ensuring the quality of such assays. However, the impact of selection of calibrator material may often get overlooked. In this article, we highlight three case studies where biomarker calibrant material selection was deemed an essential criterion for consideration. Through these case studies we highlight challenges faced, steps taken and discuss the impact on assay-related decision-making. We also provide additional perspectives for selection and characterization of calibrant proteins in the setting of an evolving biomarker context of use.

Serum cytokine profiles in healthy nonhuman primates are blunted by sedation and demonstrate sexual dimorphism as detected by a validated multiplex immunoassay

Cytokine profiling is a valuable tool for monitoring immune responses associated with disease and treatment. This study assessed the impact of sex and sedation on serum cytokines in healthy nonhuman primates (NHPs). Twenty-three cytokines were measured from serum using a bead-based multiplex assay. Assay validation for precision, sensitivity, recovery, linearity, and stability was performed. Samples from male and female cynomolgus and rhesus macaques either cooperating or sedated were compared. All cytokines except TNFα demonstrated acceptable sensitivity and precision, with variable recovery and linearity. IFNγ, IL-2, IL-5, IL-6, IL-8, IL-12/23 (p40), IL-13, IL-15, MCP-1, TGFα, VEGF met acceptance criteria; G-CSF, IL-4, IL-10, MIP1α, sCD40L were marginal. Higher cytokine levels were observed in females and cytokine levels were blunted in sedated NHPs when compared to awake cooperating NHPs. Significant differences observed in cytokines related to sex, species, or imposed by handling highlight the importance of model design on translational relevance for clinical settings.

STRATEGIES AND CHALLENGES IN METHOD DEVELOPMENT AND VALIDATION FOR THE ABSOLUTE QUANTIFICATION OF ENDOGENOUS BIOMARKER METABOLITES USING LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY

Metabolomics is a dynamically evolving field, with a major application in identifying biomarkers for drug development and personalized medicine. Numerous metabolomic studies have identified endogenous metabolites that, in principle, are eligible for translation to clinical practice. However, few metabolomic-derived biomarker candidates have been qualified by regulatory bodies for clinical applications. Such interruption in the biomarker qualification process can be largely attributed to various reasons including inappropriate study design and inadequate data to support the clinical utility of the biomarkers. In addition, the lack of robust assays for the routine quantification of candidate biomarkers has been suggested as a potential bottleneck in the biomarker qualification process. In fact, the nature of the endogenous metabolites precludes the application of the current validation guidelines for bioanalytical methods. As a result, there have been individual efforts in modifying existing guidelines and/or developing alternative approaches to facilitate method validation. In this review, three main challenges for method development and validation for endogenous metabolites are discussed, namely matrix effects evaluation, alternative analyte-free matrices, and the choice of internal standards (ISs). Some studies have modified the equations described by the European Medicines Agency for the evaluation of matrix effects. However, alternative strategies were also described; for instance, calibration curves can be generated in solvents and in biological samples and the slopes can be compared through ratios, relative standard deviation, or a modified Stufour suggested approaches while quantifying mainly endogenous metabolitesdent t-test. ISs, on the contrary, are diverse; in which seven different possible types, used in metabolomics-based studies, were identified in the literature. Each type has its advantages and limitations; however, isotope-labeled ISs and ISs created through isotope derivatization show superior performance. Finally, alternative matrices have been described and tested during method development and validation for the quantification of endogenous entities. These alternatives are discussed in detail, highlighting their advantages and shortcomings. The goal of this review is to compare, apprise, and debate current knowledge and practices in order to aid researchers and clinical scientists in developing robust assays needed during the qualification process of candidate metabolite biomarkers. © 2019 John Wiley & Sons Ltd. Mass Spec Rev.

SITC cancer immunotherapy resource document: a compass in the land of biomarker discovery

Since the publication of the Society for Immunotherapy of Cancer's (SITC) original cancer immunotherapy biomarkers resource document, there have been remarkable breakthroughs in cancer immunotherapy, in particular the development and approval of immune checkpoint inhibitors, engineered cellular therapies, and tumor vaccines to unleash antitumor immune activity. The most notable feature of these breakthroughs is the achievement of durable clinical responses in some patients, enabling long-term survival. These durable responses have been noted in tumor types that were not previously considered immunotherapy-sensitive, suggesting that all patients with cancer may have the potential to benefit from immunotherapy. However, a persistent challenge in the field is the fact that only a minority of patients respond to immunotherapy, especially those therapies that rely on endogenous immune activation such as checkpoint inhibitors and vaccination due to the complex and heterogeneous immune escape mechanisms which can develop in each patient. Therefore, the development of robust biomarkers for each immunotherapy strategy, enabling rational patient selection and the design of precise combination therapies, is key for the continued success and improvement of immunotherapy. In this document, we summarize and update established biomarkers, guidelines, and regulatory considerations for clinical immune biomarker development, discuss well-known and novel technologies for biomarker discovery and validation, and provide tools and resources that can be used by the biomarker research community to facilitate the continued development of immuno-oncology and aid in the goal of durable responses in all patients.

Update to the European Bioanalysis Forum recommendation on biomarkers assays; bringing context of use into practice

In 2012, the European Bioanalysis Forum published a recommendation on biomarker method development and the bioanalysis of biomarkers in support of drug development. Since then, there has been significant discussion on how to bring the topic of context of use of biomarker assays to the forefront so that the purpose of the assay, the use of the data and the decisions being made with the data are well defined and clearly understood, not just by the bioanalytical scientist, but across all stakeholders. Therefore, it is imperative that discussions between the bioanalytical laboratory and the end users of the data happen early (and regularly) in the drug development process to enable the right assays to be developed and appropriately validated to generate the correct data and allow suitable decisions to be made. This updated refinement to the previous European Bioanalysis Forum recommendation will highlight the items to consider when discussing context of use for biomarker assay development and validation, thus enabling the correct conversations to occur and the move away from the misapplication of PK assay validation criteria to biomarker assays.

Fit-For-Purpose PD-L1 Biomarker Testing For Patient Selection in Immuno-Oncology: Guidelines For Clinical Laboratories From the Canadian Association of Pathologists-Association Canadienne Des Pathologistes (CAP-ACP)

Since 2014, programmed cell death protein 1 (PD-1)/programmed cell death ligand 1 (PD-L1) checkpoint inhibitors have been approved by various regulatory agencies for the treatment of multiple cancers including melanoma, lung cancer, urothelial carcinoma, renal cell carcinoma, head and neck cancer, classical Hodgkin lymphoma, colorectal cancer, gastroesophageal cancer, hepatocellular cancer, and other solid tumors. Of these approved drug/disease combinations, a subset also has regulatory agency-approved, commercially available companion/complementary diagnostic assays that were clinically validated using data from their corresponding clinical trials. The objective of this document is to provide evidence-based guidance to assist clinical laboratories in establishing fit-for-purpose PD-L1 biomarker assays that can accurately identify patients with specific tumor types who may respond to specific approved immuno-oncology therapies targeting the PD-1/PD-L1 checkpoint. These recommendations are issued as 38 Guideline Statements that address (i) assay development for surgical pathology and cytopathology specimens, (ii) reporting elements, and (iii) quality assurance (including validation/verification, internal quality assurance, and external quality assurance). The intent of this work is to provide recommendations that are relevant to any tumor type, are universally applicable and can be implemented by any clinical immunohistochemistry laboratory performing predictive PD-L1 immunohistochemistry testing.

Sensitive and selective quantification of mid-regional proadrenomedullin in human plasma using ultra-performance liquid chromatography coupled with tandem mass spectrometry

Mid-regional pro-adrenomedullin (MR-proADM) is suggested to be a prognostic indicator for various diseases. Plasma MR-proADM concentration is commonly measured using immunoassays based on its immunochemical characteristics. However, some immunological interactions affect the measured concentration. We developed and validated a sensitive and selective method for measuring plasma MR-proADM concentration using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) and evaluated its clinical applicability. Plasma samples were prepared by protein precipitation and solid-phase extraction. Samples obtained from healthy volunteers (n = 38), patients with chronic kidney disease (CKD) stages 3 and 4-5 (non-dialysis; n = 20 and 17, respectively), and CKD stage 5D (dialysis; n = 34) were analyzed. Within-batch and batch-to-batch accuracy of the UPLC-MS/MS assay for quality control samples ranged from -0.69 % to 8.05 % and from 1.72 % to 5.76 %, respectively. The lower limit of quantification was 0.4 ng mL^-1. The MR-proADM concentration determined using the UPLC-MS/MS assay correlated strongly with that determined using the immunoassay (Pearson's product-moment correlation coefficient [r] = 0.7875, p < 0.001). Median (range) plasma MR-proADM concentrations of healthy volunteers, patients with CKD stages 3 and 4-5, and patients with CKD stage 5D were 0.67 (0.43-1.27), 1.89 (0.65-6.68), 3.86 (1.60-8.75) and 3.97 (0.66-9.20) ng mL^-1, respectively, and a significant difference among four groups was confirmed. We established a sensitive and selective method for determining plasma MR-proADM concentration using UPLC-MS/MS. Our novel UPLC-MS/MS assay for determining plasma MR-proADM concentration can be used in the clinical setting and may have better selectivity than the immunoassay method.

Empirical Study on the Transparency of Security Risk Information in Chinese Listed Pharmaceutical Enterprises Based on the ANP-DS Method

Frequent outbreaks of drug safety incidents pose a massive threat to public health and safety, while the transparency of security risk information in medical enterprises is not optimistic. Therefore, this study uses the analytic network process (Dempster-Shafer method) to construct a transparent comprehensive evaluation model for security risk information in listed pharmaceutical enterprises from the perspective of government supervision and listed pharmaceutical enterprises. On the basis of 59,305 data obtained by 303 enterprises listed in the Chinese biomedical sector, this research conducted an empirical study on the transparency of safety risk information in Chinese listed pharmaceutical enterprises. The current study found that the transparency of security risk information in Chinese listed pharmaceutical enterprises is generally between “general” and “relatively good” and tends to be “relatively good.” However, administrative punishment information, adverse drug reaction reporting systems, and production processes need continuous improvement.

Development of Gene Expression-Based Biomarkers on the nCounter® Platform for Immuno-Oncology Applications

Biomarkers based on transcriptional profiling can be useful in the measurement of complex and/or dynamic physiological states where other profiling strategies such as genomic or proteomic characterization are not able to adequately measure the biology. One particular advantage of transcriptional biomarkers is the ease with which they can be measured in the clinical setting using robust platforms such as the NanoString nCounter system. The nCounter platform enables digital quantitation of multiplexed RNA from small amounts of blood, formalin-fixed, paraffin-embedded tumors, or other such biological samples that are readily available from patients, and the chapter uses it as the primary example for diagnostic assay development. However, development of diagnostic assays based on RNA biomarkers on any platform requires careful consideration of all aspects of the final clinical assay a priori, as well as design and execution of the development program in a way that will maximize likelihood of future success. This chapter introduces transcriptional biomarkers and provides an overview of the design and development process that will lead to a locked diagnostic assay that is ready for validation of clinical utility.

Portable Resource-Independent Blood-Plasma Separator

The centrifuge is the gold standard for lab-based sample processing. While extremely efficient and robust, centrifuges are seldom used in the field due to the high-power requirements, size, and operational complexity. The lack of viable alternatives for remote sample collection has crippled the ability for mobile practitioners in human and animal medicine to reliably collect blood samples from their patients. There is no truly resource-independent solution that is able to perform highly efficient blood-plasma separation. Here, we describe our initial efforts in developing the High Efficiency Rapid Magnetic Erythrocyte Separator (H.E.R.M.E.S) sleeve, an apparatus that uses a magnetic bead-based separation assay in a scaled-up form factor to achieve highly efficient separation of erythrocytes from plasma within a short amount of time. The sleeve is easy-to-use, is completely resource independent, and achieves highly efficient separation in sample volumes as large as 1 mL by means of a unique mixing scheme. We demonstrate the performance of the sleeve with human blood samples and compare it against conventional end-over-end mixing.

ICCS/ESCCA consensus guidelines to detect GPI-deficient cells in paroxysmal nocturnal hemoglobinuria (PNH) and related disorders part 4 - assay validation and quality assurance

Over the past six years, a diverse group of stakeholders have put forth recommendations regarding the analytical validation of flow cytometric methods and described in detail the differences between cell-based and traditional soluble analyte assay validations. This manuscript is based on these general recommendations as well as the published experience of experts in the area of PNH testing. The goal is to provide practical assay-specific guidelines for the validation of high-sensitivity flow cytometric PNH assays. Examples of the reports and validation data described herein are provided in Supporting Information. © 2017 International Clinical Cytometry Society.

Quantification of Alpha-Synuclein in Biological Fluids by Electrochemiluminescence-Based Detection

Several potential marker candidates for Parkinson's disease (PD) in cerebrospinal fluid (CSF) have been identified. These include α-synuclein, a major constituent of the intracellular aggregates Lewy bodies, a neuropathological hallmark of PD, and others. The extracellular presence of α-synuclein in blood, CSF, saliva, and conditioned media motivated the hypothesis that the quantification of CSF α-synuclein is a biomarker for α-synuclein-related disorders. We here describe the development of an electrochemiluminescence-based assay by conversion of an established ELISA for quantification of α-synuclein. The assay not only works with CSF but can also be used to quantify α-synuclein in different biological fluids, i.e., whole blood and blood products, saliva, as well as brain homogenates and cell culture material.

Current Practices and Challenges in Method Validation

Method validation is a cornerstone on which biomarker development and utilization rest. However, given the abundance of biomarker candidates that are being identified and characterized, validation of these entities for the use in nonclinical studies can be complex. The objective of this continuing education course was to review current practices and challenges encountered during the validation of methods for the analysis of novel biomarkers. Additionally, the importance of biological validation and correlation with pathology end points for biomarker candidates was discussed. This article is a summary of the materials presented at the 36th Annual Symposium of the Society of Toxicologic Pathology for a continuing education course titled "Current Practices and Challenges in Method Validation." The speakers were subject-matter experts in the validation of quantitative mass spectrometry, multiplex binding assays, biological biomarkers, and immunophenotyping and anatomic and clinical pathology considerations in biomarker qualification.

Quantitative determination of potential urine biomarkers of respiratory illnesses using new targeted metabolomic approach

The diagnosis of asthma and chronic obstructive pulmonary disease (COPD) can be challenging due to the overlap in their clinical presentations in some patients. There is a need for a more objective clinical test that can be routinely used in primary care settings. Through an untargeted ¹H NMR urine metabolomic approach, we identified a set of endogenous metabolites as potential biomarkers for the differentiation of asthma and COPD. A subset of these potential biomarkers contains 7 highly polar metabolites of diverse physicochemical properties. To the best of our knowledge, there is no liquid chromatography-tandem mass spectrometry (LC-MS/MS) method that evaluated more than two of the target metabolites in a single analytical run. The target metabolites belong to the families of monosaccharides, organic acids, amino acids, quaternary ammonium compounds and nucleic acids, rendering hydrophilic interaction liquid chromatography (HILIC) an ideal technology for their quantification. Since a clinical decision is to be made from patients data, a fully validated analytical method is required for biomarker validation. Method validation for endogenous metabolites is a daunting task since current guidelines were designed for exogenous compounds. As such, innovative approaches were adopted to meet the validation requirements. Herein, we describe a sensitive HILIC-MS/MS method for the quantification of the 7 endogenous urinary metabolites. Detection was achieved in the multiple reaction monitoring (MRM) mode with polarity switching, using quadrupole-linear ion trap instrument (QTRAP 6500) as well as single ion monitoring in the negative-ion mode. The method was fully validated according to the regulatory guidelines. Linearity was established between 6 and 21000 ng/mL and quality control samples demonstrated acceptable intra- and inter-day accuracy (85.7%-112%), intra- and inter-day precision (CV% <11.5%) as well as stability under various storage and sample processing conditions. To illustrate the method's applicability, the validated method was applied to the analysis of a small set of urine samples collected from asthma and COPD patients. Preliminary modelling of separation was generated using partial least square discriminant analysis (R² 0.752 and Q² 0.57). The adequate separation between patient samples confirms the diagnostic potential of these target metabolites as a proof-of-concept for the differentiation between asthma and COPD. However, more patient urine samples are needed in order to increase the statistical power of the analytical model.

A systematic literature review of the human skin microbiome as biomarker for dermatological drug development

AIMS

To explore the potential of the skin microbiome as biomarker in six dermatological conditions: atopic dermatitis (AD), acne vulgaris (AV), psoriasis vulgaris (PV), hidradenitis suppurativa (HS), seborrhoeic dermatitis/pityriasis capitis (SD/PC) and ulcus cruris (UC).

METHODS

A systematic literature review was conducted according to the PRISMA guidelines. Two investigators independently reviewed the included studies and ranked the suitability microbiome implementation for early phase clinical studies in an adapted GRADE method.

RESULTS

In total, 841 papers were identified and after screening of titles and abstracts for eligibility we identified 42 manuscripts that could be included in the review. Eleven studies were included for AD, five for AV, 10 for PV, two for HS, four for SD and 10 for UC. For AD and AV, multiple studies report the relationship between the skin microbiome, disease severity and clinical response to treatment. This is currently lacking for the remaining conditions.

CONCLUSION

For two indications - AD and AV - there is preliminary evidence to support implementation of the skin microbiome as biomarkers in early phase clinical trials. For PV, UC, SD and HS there is insufficient evidence from the literature. More microbiome-directed prospective studies studying the effect of current treatments on the microbiome with special attention for patient meta-data, sampling methods and analysis methods are needed to draw more substantial conclusions.

Methods for the evaluation of biomarkers in patients with kidney and liver diseases: multicentre research programme including ELUCIDATE RCT

Background

Protein biomarkers with associations with the activity and outcomes of diseases are being identified by modern proteomic technologies. They may be simple, accessible, cheap and safe tests that can inform diagnosis, prognosis, treatment selection, monitoring of disease activity and therapy and may substitute for complex, invasive and expensive tests. However, their potential is not yet being realised.

Design and methods

The study consisted of three workstreams to create a framework for research: workstream 1, methodology – to define current practice and explore methodology innovations for biomarkers for monitoring disease; workstream 2, clinical translation – to create a framework of research practice, high-quality samples and related clinical data to evaluate the validity and clinical utility of protein biomarkers; and workstream 3, the ELF to Uncover Cirrhosis as an Indication for Diagnosis and Action for Treatable Event (ELUCIDATE) randomised controlled trial (RCT) – an exemplar RCT of an established test, the ADVIA Centaur® Enhanced Liver Fibrosis (ELF) test (Siemens Healthcare Diagnostics Ltd, Camberley, UK) [consisting of a panel of three markers – (1) serum hyaluronic acid, (2) amino-terminal propeptide of type III procollagen and (3) tissue inhibitor of metalloproteinase 1], for liver cirrhosis to determine its impact on diagnostic timing and the management of cirrhosis and the process of care and improving outcomes.

Results

The methodology workstream evaluated the quality of recommendations for using prostate-specific antigen to monitor patients, systematically reviewed RCTs of monitoring strategies and reviewed the monitoring biomarker literature and how monitoring can have an impact on outcomes. Simulation studies were conducted to evaluate monitoring and improve the merits of health care. The monitoring biomarker literature is modest and robust conclusions are infrequent. We recommend improvements in research practice. Patients strongly endorsed the need for robust and conclusive research in this area. The clinical translation workstream focused on analytical and clinical validity. Cohorts were established for renal cell carcinoma (RCC) and renal transplantation (RT), with samples and patient data from multiple centres, as a rapid-access resource to evaluate the validity of biomarkers. Candidate biomarkers for RCC and RT were identified from the literature and their quality was evaluated and selected biomarkers were prioritised. The duration of follow-up was a limitation but biomarkers were identified that may be taken forward for clinical utility. In the third workstream, the ELUCIDATE trial registered 1303 patients and randomised 878 patients out of a target of 1000. The trial started late and recruited slowly initially but ultimately recruited with good statistical power to answer the key questions. ELF monitoring altered the patient process of care and may show benefits from the early introduction of interventions with further follow-up. The ELUCIDATE trial was an ‘exemplar’ trial that has demonstrated the challenges of evaluating biomarker strategies in ‘end-to-end’ RCTs and will inform future study designs.

Conclusions

The limitations in the programme were principally that, during the collection and curation of the cohorts of patients with RCC and RT, the pace of discovery of new biomarkers in commercial and non-commercial research was slower than anticipated and so conclusive evaluations using the cohorts are few; however, access to the cohorts will be sustained for future new biomarkers. The ELUCIDATE trial was slow to start and recruit to, with a late surge of recruitment, and so final conclusions about the impact of the ELF test on long-term outcomes await further follow-up. The findings from the three workstreams were used to synthesise a strategy and framework for future biomarker evaluations incorporating innovations in study design, health economics and health informatics.

Trial registration

Current Controlled Trials ISRCTN74815110, UKCRN ID 9954 and UKCRN ID 11930.

Funding

This project was funded by the NIHR Programme Grants for Applied Research programme and will be published in full inProgramme Grants for Applied Research; Vol. 6, No. 3. See the NIHR Journals Library website for further project information.

Fit-for-Purpose Immunohistochemical Biomarkers

There are two aspects of immunohistochemistry (IHC) that are relevant to practicing pathologist: (1) understanding of IHC biomarker panels that are suitable for diagnostic, prognostic and predictive testing, and (2) understanding of IHC quality assurance (QA), which makes sure that the tests in these panels work as they should. The two aspects are closely linked together and call for collaborative approach between pathologists and IHC laboratory technologists as both need to be involved in developing and maintaining IHC biomarkers that are "fit-for-purpose". This article reviews the most current IHC QA concepts that are imminently material to practicing pathologists with emphasis on challenges that are specific to endocrine pathology.

Development of a validated LC- MS/MS method for the quantification of 19 endogenous asthma/COPD potential urinary biomarkers

Obstructive airways inflammatory diseases sometimes show overlapping symptoms that hinder their early and correct diagnosis. Current clinical tests are tedious and are of inadequate specificity in special population such as the elderly and children. Therefore, we are developing tandem mass spectrometric (MS/MS) methods for targeted analysis of urine biomarkers. Recently, proton-nuclear magnetic resonance (¹H-NMR) analysis proposed 50 urinary metabolites as potential diagnostic biomarkers among asthma and chronic obstructive pulmonary disease (COPD) patients. Metabolites are divided into 3 groups based on chemical nature. For group 1 (amines and phenols, 19 urinary metabolites), we developed and validated a high performance liquid chromatographic (HPLC)-MS/MS method using differential isotope labeling (DIL) with dansyl chloride. Method development included the optimization of the derivatization reaction, the MS/MS conditions, and the chromatographic separation. Linearity varied from 2 to 4800 ng/mL and the use of ¹³C₂-labeled derivatives allowed for the correction of matrix effects as well as the unambiguous confirmation of the identity of each metabolite in the presence of interfering isomers in urine. Despite the challenges associated with method validation, the method was fully validated as per the food and drug administration (FDA) and the European medicines agency (EMA) recommendations. Validation criteria included linearity, precision, accuracy, dilution integrity, selectivity, carryover, and stability. Challenges in selectivity experiments included the isotopic contributions of the analyte towards its internal standard (IS), that was addressed via the optimization of the IS concentration. In addition, incurred sample analysis was performed to ensure that results from patient samples are accurate and reliable. The method was robust and reproducible and is currently being applied in a cohort of asthma and COPD patient urine samples for biomarker discovery purposes.

Best practices in performing flow cytometry in a regulated environment: feedback from experience within the European Bioanalysis Forum

Flow cytometry is a powerful tool that can be used for the support of (pre)clinical studies. Although various white papers are available that describe the set-up and validation of the instrumentation (the flow cytometer) and validation of flow cytometry methods, to date no guidelines exist that address the requirements for performing flow cytometry in a regulated environment. In this manuscript, the European Bioanalysis Forum presents additional practice guidance on the use of flow cytometry in the support of drug development programs and addresses areas that are not covered in the previous publications. The concepts presented here are based on the consensus of discussions in the European Bioanalysis Forum Topic Team 32, in meetings in Barcelona, Limelette and multiple telephone conferences.

Performance evaluation of three platforms with ultrasensitive ligand-binding assay potential

Aim: We evaluated three immunoassay-based technologies and their biomarker kits, by determining precision, parallelism and detectability of analytes of interest. Materials & methods: We compared ultrasensitive assays for three biomarkers: interleukins IL-6, IL-13 and IL-17A using kits obtained from Roche (IMPACT platform – proprietary platform), Singulex (Erenna®) and Quanterix (Simoa™). We defined the true LLOD as the LLOQs, and provided disease-specific parallelism results and detectability levels for endogenous analyte, which were good across platforms, though they varied from analyte to analyte. Conclusion: We highlight a simplified approach employed for evaluating ultrasensitive kits and provide an overview of the methodologies used to compare available assays. All three platforms are able to detect very low-level analytes. We recommend all three platforms for detection of very low-level analytes.

Immunotherapy biomarkers 2016: overcoming the barriers

This report summarizes the symposium, 'Immunotherapy Biomarkers 2016: Overcoming the Barriers', which was held on April 1, 2016 at the National Institutes of Health in Bethesda, Maryland. The symposium, cosponsored by the Society for Immunotherapy of Cancer (SITC) and the National Cancer Institute (NCI), focused on emerging immunotherapy biomarkers, new technologies, current hurdles to further progress, and recommendations for advancing the field of biomarker development.

Imaging biomarker roadmap for cancer studies

Imaging biomarkers (IBs) are integral to the routine management of patients with cancer. IBs used daily in oncology include clinical TNM stage, objective response and left ventricular ejection fraction. Other CT, MRI, PET and ultrasonography biomarkers are used extensively in cancer research and drug development. New IBs need to be established either as useful tools for testing research hypotheses in clinical trials and research studies, or as clinical decision-making tools for use in healthcare, by crossing 'translational gaps' through validation and qualification. Important differences exist between IBs and biospecimen-derived biomarkers and, therefore, the development of IBs requires a tailored 'roadmap'. Recognizing this need, Cancer Research UK (CRUK) and the European Organisation for Research and Treatment of Cancer (EORTC) assembled experts to review, debate and summarize the challenges of IB validation and qualification. This consensus group has produced 14 key recommendations for accelerating the clinical translation of IBs, which highlight the role of parallel (rather than sequential) tracks of technical (assay) validation, biological/clinical validation and assessment of cost-effectiveness; the need for IB standardization and accreditation systems; the need to continually revisit IB precision; an alternative framework for biological/clinical validation of IBs; and the essential requirements for multicentre studies to qualify IBs for clinical use.

Validation of biomarkers to predict response to immunotherapy in cancer: Volume I - pre-analytical and analytical validation

Immunotherapies have emerged as one of the most promising approaches to treat patients with cancer. Recently, there have been many clinical successes using checkpoint receptor blockade, including T cell inhibitory receptors such as cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and programmed cell death-1 (PD-1). Despite demonstrated successes in a variety of malignancies, responses only typically occur in a minority of patients in any given histology. Additionally, treatment is associated with inflammatory toxicity and high cost. Therefore, determining which patients would derive clinical benefit from immunotherapy is a compelling clinical question.

Although numerous candidate biomarkers have been described, there are currently three FDA-approved assays based on PD-1 ligand expression (PD-L1) that have been clinically validated to identify patients who are more likely to benefit from a single-agent anti-PD-1/PD-L1 therapy. Because of the complexity of the immune response and tumor biology, it is unlikely that a single biomarker will be sufficient to predict clinical outcomes in response to immune-targeted therapy. Rather, the integration of multiple tumor and immune response parameters, such as protein expression, genomics, and transcriptomics, may be necessary for accurate prediction of clinical benefit. Before a candidate biomarker and/or new technology can be used in a clinical setting, several steps are necessary to demonstrate its clinical validity. Although regulatory guidelines provide general roadmaps for the validation process, their applicability to biomarkers in the cancer immunotherapy field is somewhat limited. Thus, Working Group 1 (WG1) of the Society for Immunotherapy of Cancer (SITC) Immune Biomarkers Task Force convened to address this need. In this two volume series, we discuss pre-analytical and analytical (Volume I) as well as clinical and regulatory (Volume II) aspects of the validation process as applied to predictive biomarkers for cancer immunotherapy. To illustrate the requirements for validation, we discuss examples of biomarker assays that have shown preliminary evidence of an association with clinical benefit from immunotherapeutic interventions. The scope includes only those assays and technologies that have established a certain level of validation for clinical use (fit-for-purpose). Recommendations to meet challenges and strategies to guide the choice of analytical and clinical validation design for specific assays are also provided.

Optimization and evaluation of Luminex performance with supernatants of antigen-stimulated peripheral blood mononuclear cells

BACKGROUND

The Luminex bead-based multiplex assay is useful for quantifying immune mediators such as cytokines and chemokines. Cross-comparisons of reagents for this technique from different suppliers have already been performed using serum or plasma but rarely with supernatants collected from antigen-stimulated peripheral blood mononuclear cells (PBMC). Here, we first describe an optimization protocol for cell culture including quantity of cells and culture duration to obtain reproducible cytokine and chemokine quantifications. Then, we compared three different Luminex kit suppliers.

RESULTS

Intraclass correlation coefficients (ICCs) for a 2-days stimulation protocol were >0.8 for IFNγ and Perforin. The specific concentration was maximal after two or five days of stimulation, depending on the analyte, using 0.5 million PBMC per well, a cell quantity that gave the same level of specific cytokine secretion as 1.0 million. In the second part of the study, Luminex kits from Millipore showed a better working range than Bio-Rad and Ozyme ones. For tuberculin purified protein derivative (PPD)-stimulated samples, the overall mean pooled coefficients of variation (CVs) for all donors and all cytokines was 17.2 % for Bio-Rad, 19.4 % for Millipore and 26.7 % for Ozyme. Although the different kits gave cytokine concentrations that were generally compatible, there were discrepancies for particular cytokines. Finally, evaluation of precision and reproducibility of a 15-plex Millipore kit using a "home-made" internal control showed a mean intra-assay CV <13 % and an inter-assay CV <18 % for each cytokine concentration.

CONCLUSIONS

A protocol with a single round of stimulation but with two time points gave the best results for assaying different cytokines. Millipore kits appear to be slightly more sensitive than those from Bio-Rad and Ozyme. However, we conclude that the panel of analytes that need to be quantified should be the main determinant of kit selection. Using an internal control we demonstrated that a 15-plex magnetic Milliplex kit displayed good precision and reproducibility. Our findings should help optimize assays for evaluating immune responses during the course of disease or infection, or in response to vaccine or therapy.

Fit-for-purpose biomarker immunoassay qualification and validation: three case studies

AIM

To improve on the efficiency of biomarker assay readiness, and for reliable biomarker data to support three drug programs, we implemented a fit-for-purpose approach, qualifying two biomarker assays and validating a third. Results/methodology: The qualification strategy and selection of experiments for two exploratory biomarkers (CXCL1, CCL19) was determined by the intended use of the biomarker data. The third biomarker, IL-6, was validated as the data would be used in monitoring patient safety during dose-escalation studies in a Phase I trial. All three assays passed a priori acceptance criteria.

CONCLUSION

These assays highlight strategies and methodologies for a fit-for-purpose approach. Minimum qualification, full qualification and validation were chosen and supported programs at different stages of drug development.

Confronting the Care Delivery Challenges Arising from Precision Medicine

Understanding the biology of cancer at the cellular and molecular levels, and the application of such knowledge to the patient, has opened new opportunities and uncovered new obstacles to quality cancer care delivery. Benefits include our ability to now understand that many, if not most, cancers are not one-size-fits-all. Cancers are a variety of diseases for which intervention may be very different. This approach is beginning to bear fruit in gynecologic cancers where we are investigating therapeutic optimization at a more focused level, that while not yet precision care, is perhaps much improved. Obstacles to quality care for patients come from many directions. These include incomplete understanding of the role of the mutant proteins in the cancers, the narrow spectrum of agents, broader mutational profiles in solid tumors, and sometimes overzealous application of the findings of genetic testing. This has been further compromised by the unbridled use of social media by all stakeholders in cancer care often without scientific qualification, where anecdote sometimes masquerades as a fact. The only current remedy is to wave the flag of caution, encourage all patients who undergo genetic testing, either germline or somatic, to do so with the oversight of genetic counselors and physician scientists knowledgeable in the pathways involved. This aspiration is accomplished with well-designed clinical trials that inform next steps in this complex and ever evolving process.

Establishing the clinical utility of epigenetic markers in cancer: many challenges ahead

The use of epigenetic biomarkers in cancer management relies on the availability of robust assays and evidence that these markers are able to segregate clinically significant groups of patients. While many cancers are characterized by genetic and epigenetic modifications, it is far simpler to develop molecular tests that detect genetic rather than epigenetic changes. In this special report, we will describe the challenges associated with developing epigenetic assays and the practical issues that must be overcome before they can be used in the clinic.

Saturation monitoring of VX15/2503, a novel semaphorin 4D-specific antibody, in clinical trials

Background

Receptor occupancy, or saturation, assays are often utilized in preclinical and clinical development programs to evaluate the binding of a biologic to a cellular target. These assays provide critical information regarding the dose of drug required to “saturate” the target as well as important pharmacodymamic (PD) data. A flow cytometric method was developed to measure the degree of Semaphorin 4D (SEMA4D; CD100) saturation by VX15/2303, an investigational monoclonal antibody specific for SEMA4D.

Methods

The assay detects VX15/2503, a human IgG₄ specific for SEMA4D, with an IgG₄‐specific monoclonal antibody.

Results

Data generated allowed assessment of two related SEMA4D‐specific pharmacodynamic (PD) markers: (1) The measurement of cellular SEMA4D (cSEMA4D) saturation by VX15/2503, and (2) the cell membrane expression levels of cSEMA4D.

Conclusions

This assay specifically and reproducibly measured cSEMA4D saturation and expression levels. Evaluation of the SEMA4D‐specific PD markers were critical in determining the clinical saturation threshold of cSEMA4D by VX15/2503. © 2015 he Authors Cytometry Part B: Clinical Cytometry Published by Wiley Periodicals, Inc.

Recommendations for Use and Fit-for-Purpose Validation of Biomarker Multiplex Ligand Binding Assays in Drug Development

Multiplex ligand binding assays (LBAs) are increasingly being used to support many stages of drug development. The complexity of multiplex assays creates many unique challenges in comparison to single-plexed assays leading to various adjustments for validation and potentially during sample analysis to accommodate all of the analytes being measured. This often requires a compromise in decision making with respect to choosing final assay conditions and acceptance criteria of some key assay parameters, depending on the intended use of the assay. The critical parameters that are impacted due to the added challenges associated with multiplexing include the minimum required dilution (MRD), quality control samples that span the range of all analytes being measured, quantitative ranges which can be compromised for certain targets, achieving parallelism for all analytes of interest, cross-talk across assays, freeze-thaw stability across analytes, among many others. Thus, these challenges also increase the complexity of validating the performance of the assay for its intended use. This paper describes the challenges encountered with multiplex LBAs, discusses the underlying causes, and provides solutions to help overcome these challenges. Finally, we provide recommendations on how to perform a fit-for-purpose-based validation, emphasizing issues that are unique to multiplex kit assays.

Optimisation of immunofluorescence methods to determine MCT1 and MCT4 expression in circulating tumour cells

BACKGROUND

The monocarboxylate transporter-1 (MCT1) represents a novel target in rational anticancer drug design while AZD3965 was developed as an inhibitor of this transporter and is undergoing Phase I clinical trials ( http://www.clinicaltrials.gov/show/NCT01791595 ). We describe the optimisation of an immunofluorescence (IF) method for determination of MCT1 and MCT4 in circulating tumour cells (CTC) as potential prognostic and predictive biomarkers of AZD3965 in cancer patients.

METHODS

Antibody selectivity was investigated by western blotting (WB) in K562 and MDAMB231 cell lines acting as positive controls for MCT1 and MCT4 respectively and by flow cytometry also employing the control cell lines. Ability to detect MCT1 and MCT4 in CTC as a 4(th) channel marker utilising the Veridex™ CellSearch system was conducted in both human volunteer blood spiked with control cells and in samples collected from small cell lung cancer (SCLC) patients.

RESULTS

Experimental conditions were established which yielded a 10-fold dynamic range (DR) for detection of MCT1 over MCT4 (antibody concentration 6.25 μg/mL; integration time 0.4 seconds) and a 5-fold DR of MCT4 over MCT 1 (8 μg/100 μL and 0.8 seconds). The IF method was sufficiently sensitive to detect both MCT1 and MCT4 in CTCs harvested from cancer patients.

CONCLUSIONS

The first IF method has been developed and optimised for detection of MCT 1 and MCT4 in cancer patient CTC.