NEW YORK – Proteomics firm Alamar Biosciences is seeing strong interest in its neurology immunoassay panel as a tool for Alzheimer's research, company officials said.
The panel, called the NULISAseq CNS Disease Panel 120, measures 120 proteins linked to neurological disease, and is proving a particularly attractive option for scientists and clinicians studying biomarkers and pathways outside the brain amyloid paradigm where much Alzheimer's research has concentrated, said Yuling Luo, Alamar's founder, chairman, and CEO.
Existing Alzheimer's drugs as well as the biomarkers commonly used for diagnosis, all focus on targeting or detecting the brain amyloid plaques characteristic of the disease. Traditionally, PET imaging and cerebrospinal fluid (CSF) testing have been used to detect amyloid plaques. More recently, blood-based biomarkers — phosphorylated-tau 217 in particular — have shown great promise for this purpose.
Researchers are aware, however, that amyloid pathology is only one aspect of Alzheimer's, with changes across a variety of biological pathways contributing to the development and progression of the disease.
The general consensus among key opinion leaders is that Alzheimer's disease is highly heterogeneous, Luo said. "That heterogeneity requires an understanding of Alzheimer's disease at the molecular level beyond p-tau 217," he noted.
Studying large numbers of proteins linked to neurological conditions like Alzheimer's can be challenging, however, particularly given that they are often present in blood at low concentrations, requiring highly sensitive assays. CSF samples are also an option, but collection of these samples is more difficult as it requires a lumbar puncture.
Researchers use tools like mass spectrometry and affinity-based assay panels from companies like Olink and Standard BioTools for broader discovery experiments in Alzheimer's, but Luo said Alamar believes its NULISA (NUcleic acid-Linked Immuno-Sandwich Assay) technology offers advantages in sensitivity and ease of use that will help it win customers in this space.
NULISA is based on the proximity ligation assay (PLA) originally commercialized by Olink Bioscience, the forerunner of Olink. (Olink is currently suing Alamar for patent infringement.) PLA uses pairs of antibodies attached to unique DNA sequences to detect proteins of interest. When the antibodies bind to their targets, the attached DNA strands are brought into proximity and ligated, forming a new template that can then be amplified by rolling circle amplification.
PLA has been in widespread use for more than a decade. According to Alamar, NULISA improves upon the standard PLA method by using a two-stage wash and capture workflow that reduces assay background, thereby improving its sensitivity. Alamar has also developed an automated platform for running NULISA assays, its Argo HT instrument, which the company says requires less than 30 minutes of hands-on time per experiment. Traditional PLA experiments can involve several hours or more of hands-on time.
Luo noted that Alamar had not initially planned to make neurology an area of focus but received strong interest from potential customers in the space, especially around the possibility that the platform's high sensitivity could enable detection of a wide range of neurology markers in blood.
He said the company built the CNS Disease Panel based on input from these potential customers, with an undisclosed large pharma firm providing an initial list of 75 markers it was interested in measuring and other researchers and academics in the space then suggesting additional proteins of interest.
Thomas Karikari, an assistant professor of psychiatry at the University of Pittsburgh, recently used the panel for an analysis of 176 plasma samples taken from 113 subjects from the MYHAT-NI cohort, detailed in a paper published this month in Molecular Neurodegeneration. The researchers identified 14 proteins that were significantly altered in individuals with brain amyloid pathology as determined by PET imaging. They also identified three markers that increased longitudinally in amyloid-positive patients as their amyloid pathology worsened, as well as a set of markers linked to functions including "neuroinflammation, synaptic function, and cerebrovascular integrity" that increased longitudinally with changes in PET tau levels.
"More recently, the [Alzheimer's research] field has become more appreciative of the multifaceted [and] multifactorial nature of Alzheimer's," Karikari said, noting that this has spurred interest in studying larger panels of markers linked to the disease.
He said his lab found the Alamar panel attractive in that it is more comprehensive and sensitive than many other targeted neurology panels, allowing for the measurement of both core markers like forms of amyloid-beta (Aβ) and tau and emerging markers, many of which, he noted, were previously accessible only in CSF.
Karikari said that he and his colleagues consider their recent study to be a proof of concept demonstrating the ability of the Alamar technology to measure these markers in blood. Next, he said, they hope to begin testing certain of these markers — particularly those linked to inflammation and vascular dysfunction — in other well-characterized patient cohorts to determine what information they might provide about the development and progression of Alzheimer's.
While Alamar's NULISA assays and the Argo HT instrument are for research use only, the company has clinical ambitions. Luo said it plans to develop a clinical platform, the Argo Dx, that Alamar and outside parties could use to develop and run diagnostics using its technology. He declined to give a timeline for when the company will launch such a system but said it hopes to do so "as soon as we can."
In the Molecular Neurodegeneration study, Karikari and his coauthors looked at the performance of Alamar's assays for measuring a set of plasma proteins currently used in Alzheimer's diagnoses including p-tau 217, p-tau 231, p-tau 181, neurofilament light (NfL), glial fibrillary acidic protein (GFAP), Aβ40, and Aβ42. They compared the values for these markers produced by the Argo HT to values produced by assays run using Quanterix's Simoa technology, which is widely used in Alzheimer's research as well as for clinical testing.
They found the two platforms had equivalent diagnostic accuracy in terms of identifying individuals positive for brain amyloid pathology as determined by PET imaging, with both scoring as more than 90 percent accurate once the risk factors of age, APOE4 carrier status, and sex were included.
The correlation between the two platforms varied across the seven markers analyzed, with Spearman rank correlation coefficient (rho) values ranging from a high of 0.88 for p-tau 217 to a low of 0.32 for Aβ40.
Karikari said he and his colleagues are now comparing the performance of a variety of platforms for measuring common clinically used blood biomarkers for Alzheimer's. The systems they are looking at include Alamar's NULISA, Quanterix's Simoa, and Fujiebio's Lumipulse G pTau 217/β-Amyloid 1-42 Plasma Ratio in vitro diagnostic test, which the company recently submitted to the US Food and Drug Administration.
Researchers within the European Predictom project are also using NULISA for Alzheimer's biomarker work. Led by Norway's Stavanger University Hospital, the $22.7 million effort comprises 30 academic and industry partners including Novo Nordisk, GE HealthCare, Siemens Healthineers, the University of Geneva, Kings College London, and Alzheimer Europe, and aims to develop tools for the early detection of Alzheimer's disease.
One project within the initiative is looking at whether blood-based Alzheimer's markers can be measured in self-collected finger-prick samples. Led by Nicholas Ashton, associate professor of neurochemistry at the University of Gothenburg, the study aims to measure p-tau 217 in around 4,000 participants using the NULISA assay. The researchers will also measure the full 120 proteins in the CNS Disease Panel in each blood spot.