A single microliter of sample. Proteins measured at attomolar levels. No wash steps, and the qPCR machine you already own. That is the wager Spear Bio is scaling out of Harvard's Wyss Institute.
Most diagnostic breakthroughs arrive as bigger, more expensive machines. Spear Bio arrived as better chemistry. The Woburn, Massachusetts company builds immunoassays - the workhorse tests that measure proteins in blood and other fluids - but with a sensitivity that upends what the standard version can do. Its platform, SPEAR, can detect protein biomarkers at attomolar concentrations, a range where a sample may contain only dozens of the target molecules, and it does so from roughly one microliter of diluted sample.
The name is an acronym: Successive Proximity Extension Amplification Reaction. It was invented in the laboratory of Peng Yin at Harvard's Wyss Institute for Biologically Inspired Engineering, then de-risked and carried toward the market by co-founder Feng Xuan, who now serves as chief executive. The company incorporated in 2021 and was formally launched by the Wyss Institute in 2022.
What makes SPEAR unusual is a mechanism the company describes as two-factor authentication for antibodies. In a conventional immunoassay, antibodies that bind where they should not create background noise - false signal that limits how faint a real signal can be before it disappears. SPEAR requires its probes to remain bound to a target for an extended window before any amplifiable signal is generated. Fleeting, non-specific binding never clears the bar. Background collapses, and faint signals become legible.
The practical payoff is a workflow that is both more sensitive and simpler. SPEAR is homogeneous and wash-free: bind, react, amplify, then read the result on an ordinary qPCR instrument. There is no proprietary reader to buy, no wash steps to introduce error, and no need for the high-affinity antibodies that other ultra-sensitive methods depend on. The company reports more than a five-log improvement over conventional ELISA - roughly a hundred-thousand-fold - while using about a hundred times less sample volume.
The homogeneous workflow is what lets SPEAR run on instruments labs already have. Everything happens in a single reaction, and the qPCR readout turns a protein measurement into a nucleic-acid amplification - the kind of signal molecular biology tools amplify exceptionally well.
Incubate roughly 1 µL of diluted sample with proprietary SPEAR probes that attach to proximal sites on the target protein.
Add the reaction mix without any washing. The two-factor authentication step demands sustained co-localization, suppressing background from stray binding.
Add qPCR mix and quantify a target-specific signal on a standard instrument - no specialized reader required.
Sensitivity in immunoassays is measured in orders of magnitude - logs - of improvement over conventional ELISA. Digital ELISA, the prior leap forward, adds about one log. In the company's data using low-affinity antibodies, SPEAR reaches beyond five. The bars below are illustrative of that reported relative scale.
"The quantification of mere dozens of protein molecules in a sample."
Spear Bio's first commercial focus is neurodegeneration, where the biomarkers of interest circulate at vanishingly low levels and every draw of blood or cerebrospinal fluid is precious. Its SPEAR UltraDetect line, launched in 2025, targets the proteins researchers use to study Alzheimer's disease, ALS, multiple sclerosis and traumatic brain injury.
The core wash-free, homogeneous immunoassay that measures proteins at attomolar levels from ~1 µL using a two-factor authentication mechanism and qPCR readout.
Next-generation ultra-sensitive assays for neurodegenerative research, launched with four neurology biomarkers.
Phosphorylated tau assays - leading blood biomarkers for Alzheimer's disease research.
A marker of neuronal damage used broadly across neurology research.
Glial fibrillary acidic protein, a marker of astrocyte activity relevant to brain injury and dementia.
Detection of neutralizing antibodies, extending SPEAR into immunology and infectious disease research.
Academic labs, pharmaceutical and biotech companies, and clinical research groups studying low-abundance proteins - with a strong initial pull from neurology. These are teams for whom a faint, early biomarker signal is the difference between a study that works and one that stalls.
Two long-standing immunoassay bottlenecks: background noise that hides faint signals, and dependence on scarce high-affinity antibodies. SPEAR loosens both, and its sub-microliter volume opens research where sample is limited, such as CSF studies and pediatric work.
A B2B life-science tools company selling assay kits that run on customers' existing qPCR instruments - lowering the cost of adoption. Bio-Techne handles worldwide distribution, letting Spear Bio focus on the science and manufacturing.
SPEAR competes in ultra-sensitive proteomics against digital ELISA (Quanterix Simoa), proximity extension proteomics (Olink) and aptamer platforms (SomaLogic). Its distinguishing bet: no proprietary instrument, and sensitivity that reaches attomolar levels.
Oversubscribed Series A, closed July 2024, on top of roughly $8.4M in earlier financing - about $53.4M raised in total. The round accelerates the assay menu, commercial offerings and in-house manufacturing.
The company is established in Woburn, Massachusetts to commercialize SPEAR, licensed from the Wyss Institute.
Harvard formally announces the spinout in August 2022, with co-founders Peng Yin and Feng Xuan.
An oversubscribed round led by Foresite Capital and Bio-Techne funds expansion, alongside a global distribution deal.
The next-generation immunoassay line ships with four neurology biomarker assays: pTau231, pTau217, GFAP and NfL.
"This funding will allow us to accelerate our assay menu expansion to solve challenges in protein research and early disease diagnostics."
Spear Bio develops and sells ultra-sensitive immunoassay kits based on its SPEAR platform, which measures protein biomarkers at attomolar levels from about one microliter of sample using standard qPCR instruments.
SPEAR (Successive Proximity Extension Amplification Reaction) is a homogeneous, wash-free immunoassay that uses a two-factor authentication mechanism to suppress background, delivering more than a five-log sensitivity improvement over conventional ELISA.
It was co-founded by Feng Xuan (CEO) and Harvard/Wyss professor Peng Yin, and is headquartered in Woburn, Massachusetts. The technology was invented at Harvard's Wyss Institute.
Roughly $53.4M in total, including an oversubscribed $45M Series A in July 2024 led by Foresite Capital and Bio-Techne.
Academic, pharmaceutical and clinical researchers studying low-abundance protein biomarkers, with a strong initial focus on neurodegenerative diseases such as Alzheimer's, Parkinson's and ALS.