The use of biomarker assays to advance personalized medicine through predictive risk assessment, improved diagnostics, and monitoring of disease progression and treatment response was one of the main topics of discussion at the recent American Association of Clinical Chemistry (AACC) meeting in Philadelphia, PA. The value of novel and “repurposed” biomarkers, and the various methods in use and being developed to measure them are themes that spanned therapeutic areas and different analytical technologies. The focus is on developing highly sensitive and accurate tests, whether for measuring peptides, proteins, steroid hormones, or other biomolecules that can guide clinical decision-making and help individualize patient management.
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Some of the new biomarker assays aim to differentiate acute from chronic disease and stable from progressive disease, for example in the areas of coronary artery disease and kidney disease. Biomarkers for cardiac risk profiling are gaining a lot of attention, as Lynsey Adams of Randox Laboratories noted. The company’s ELISA to measure HDL3 cholesterol, a subform of high-density lipoprotein, provides clinicians with more detailed lipid profiling information. These types of risk assessment assays can help stratify patients based on the need for more aggressive preventive therapy.
Cardiac troponin is a protein biomarker, specific for cardiac tissue, which is routinely used to diagnose myocardial infarction in the acute setting. High-sensitivity assays in development will enable broader applications of cardiac troponin in the setting of chronic heart disease, for predicting mortality risk and disease progression. Using these assays, researchers have been able to show that very small changes in cardiac troponin levels correlate with risk for death due to cardiovascular disease and for the development of heart failure.
“Even a slight increase in cardiac troponin can predict cardiovascular disease over the next decade,” says Guido Baechler, president and CEO of Singulex, which has developed a high-sensitivity cardiac troponin assay based on its single molecule counting technology.
Procalcitonin, a peptide precursor of the hormone calcitonin, has shown promise as a predictive biomarker for patients at risk of progression to systemic bacterial infection, or septic shock. At the AACC meeting, Thermo Scientific announced that it had received expanded FDA clearance for its procalcitonin biomarker assay for
sepsis risk assessment.
Mass Spectrometry and Immunoassays Vie for Attention
Immunoassays to measure biomarkers and a variety of analytes for diagnostic testing are a mainstay of clinical laboratories. There is currently an emphasis on increased automation to improve throughput and efficiency and minimize manual handling and human errors. Automation of the clinical laboratory workflow offers substantial benefits, but is not without challenges, as noted by Nikola Baumann, PhD, Director, Central Clinical Laboratory and Central Processing at the Mayo Clinic. In particular, Dr. Baumann described the need for greater standardization in the pre-analytical phase of testing. Among the anticipated advances in automation for the clinical laboratory that she foresees are more flexibility for accommodating different analyzers and specimens, and solutions that help to consolidate and link areas of the lab that have traditionally operated in silos.
New technologies for automating immunoassays and molecular diagnostic tests such as PCR- or sequencing-based assays were also on display. These included automated platforms designed for high volume testing by large clinical laboratories, such as the newly announced Atellica™ Solution from Siemens. Additionally compact diagnostic systems are contributing to the ease of transitioning immunoassays and many of the new molecular testing methods to smaller labs and, increasingly to point-of-care settings including clinics and physicians’ offices. Seeing a promising market for what Giles Sanders, scientist and business development consultant at TTP, describes as “desktop biology,” the company developed the new Puckdx™ platform. TTP will convert a partner’s immunoassay or molecular diagnostic to a single-use disposable cartridge compatible with the system.
Interest in and applications for mass spectrometry (MS)-based testing in clinical laboratories have expanded significantly, and that trend shows no sign of slowing as the size, cost, and operational complexity of MS instruments continue to decrease. The results of assays run on mass spectrometers coupled to liquid chromatographs can be used to confirm or complement immunoassays. In large reference laboratories, MS has long been the method of choice for quantifying many analytes. Despite the learning curve involved in being able to use MS-based assay systems and to interpret the test results properly, MS is increasingly a technology of choice for laboratory developed tests (LDTs) and is even the basis for some new point-of-care diagnostic platforms.
Increasing Regulatory Oversight
Analytical methods and biomarkers face an increasingly regulated market as they transition from life science research to clinical laboratories, where they may be automated and offered as LDTs or fully compliant in vitro diagnostic (IVD) solutions, noted Dr. Achim von Leoprechting, Executive Vice President and Head of the Partnering Business at Tecan. LDTs are assays that are used essentially only by the lab in which they are developed. As such, they have not traditionally required FDA clearance, although the agency has signaled its intention to increase regulatory oversight of LDTs.
At the AACC meeting, Scott Kephart, PhD, President of Quasar Companies, gave a presentation on behalf of Agilent on the topic of how to perform an LDT validation. Dr. Kephart specializes in urine-based drug testing using LC/MS. Making LC/MS technology accessible to and financially viable for POC diagnostics requires narrowing the scope of capabilities of conventional research-based instruments -- simplifying them to meet the needs of an individual lab. Yet competing market forces are at play, says Dr. Kephart, because even as manufacturers try to reign in the complexity of the instruments and make them more user friendly, at the same time, the drug testing market is demanding a broader scope of tests.
Athena Petrides, PhD, Assistant Medical Director of Chemistry and Director of Toxicology at Brigham and Women's Hospital, in a presentation on behalf of Waters, discussed the advantages and challenges of introducing LC/MS technology into a clinical laboratory, specifically for urine-based drug testing. The main drawbacks of traditional immunoassay-based drug testing include limited selectivity, with results being class specific only and cross-reactivity within a drug class being vendor-specific, stated Dr. Petrides. She also noted that immunoassays do not provide information on drug metabolism. In contrast, selected reaction monitoring (SRM) using LC/MS offers good selectivity, analytical sensitivity, and high signal-to-noise ratios. In drug testing, the ability to interpret the MS results correctly across the entire profile of drugs tested and their metabolites is one of the main challenges and depends on adequate staff training.
Circulating Tumor Cells and Cell-free DNA
The diagnostic potential of tumor cells and cell-free tumor DNA that can be isolated from patients' blood and used for liquid biopsies, and of other types of rare cells and circulating cell-free DNA (cfDNA) generated a lot of buzz at the AACC meeting. Non-cancer-related applications of cfDNA analysis include the ability to do noninvasive prenatal testing on fetal DNA circulating in the mother's bloodstream. This rapidly growing field still faces challenges to more routine adoption, including the fact that capture of fetal cells is not yet foolproof and can fail. Results interpretation and quality assessment are other aspects of cfDNA-based prenatal testing targeted for improvement.
Liquid biopsies, still a new and emerging area of clinical research and development, are generating a great deal of interest for their potential to improve cancer diagnostics and monitoring, helping guide individualized treatment strategies. Isolation and analysis of circulating tumor cells or tumor-derived cfDNA can provide real-time information and allow clinicians to follow metastatic disease over time without subjecting patients to repeat surgical procedures. Liquid biopsies also offer valuable information on tumor heterogeneity and changes in cancer-related gene expression patterns. Physicians can use the results of periodic testing to monitor disease progression and treatment response and perhaps even to detect the development of drug resistance before there is clinical evidence that a treatment is no longer effective. Analysis of DNA extracted from liquid biopsies can also enable cancer genome analysis across a broader range of samples, tumor types, and disease stages. Research presented at the AACC meeting demonstrated how advances in noninvasive cancer diagnostics are enabling high-throughput molecular analysis of circulating tumor DNA for cancer genome profiling.
The technology is also being applied to circulating tumor DNA analysis in studies with direct clinical relevance. For example, in a poster presentation from the MD Anderson Cancer Center, researchers demonstrated the ability to perform molecular characterization and gene expression analysis on circulating breast cancer cells isolated from blood using the Parsortix™ cell separation system from ANGLE. The data show the potential to detect gene transcripts with high levels of sensitivity. The researchers reported good correlation between expected and observed gene expression.
The Parsortix™system from ANGLE uses micro-fluidics on a disposable cassette to capture and then harvest circulating tumor cells (CTCs) from blood. The device selects out tumor cells based on their less deformable nature and larger size compared to other blood components.
Research and clinical advances in cfDNA were also reported in the area of organ transplantation. The presence of donor graft-derived cfDNA can provide an early indication of the potential for rejection of a transplanted organ. Circulating cfDNA testing is also contributing to improved, more personalized methods of determining optimal immunosuppressant therapy.
The IVD market, currently valued at more than $40 billion dollars and expanding at a CAGR of 3-5%, according to estimates presented by Dr. David Martyr, CEO of Tecan, is benefiting from advances in research-based analytical technologies that are being automated and optimized for use in the clinical setting. High-sensitivity biomarker assays, mass spec-based analytical tests, automation of molecular diagnostics, and gene expression analysis performed on liquid biopsies are just some examples of the methods and technologies transitioning into clinical laboratories.
Vicki Glaser is a freelance writer living in Pennsylvania.