Developing a blood test for ALS

My connection to amyotrophic lateral sclerosis (ALS).

A typical online search for ALS or Lou Gehrig's disease returns, "a neurodegenerative disease -- affecting the motor neurons in the brain and spinal chord irreversibly." Not long ago, when I started working on the disease, my only connections to ALS were a definition and knowing the fact that Professor Stephen Hawking lived with ALS. Soon I learnt that Dr. Hawking's was one of the rare cases; for most patients, the life expectancy after diagnosis is about 2 to 5 years -- this was the first shock for me. ALS is tagged as a "rare disease" based merely on the number of people living with ALS in the US (5 to 7 cases per 100,000). However, as I started interacting with patients, caregivers and people with susceptible genes, my perception quickly outgrew the definitions and stats. Early in this interviewing process -- speaking with "real people" about personal loses, feeble fights against aggressive disease progression and practically no therapeutic options -- my heart sank. While I felt the urge to work harder on our project with an aim to detect all types of ALS at an early stage, I felt powerless. But as I continued my journey, I connected with a large number of researchers, neurologists and ALS advocates, especially through NEALS annual meetings, I felt hopeful. Experiencing the bravery, passion and tremendous zeal of amazing people like Andrea Lytle and Cassandra Haddad, I felt empowered. And at the end of the most recent NEALS Annual Meeting 2025, my take home message is that, "with a wholehearted effort from stakeholders across the disease landscape, ALS might soon be a treatable disease."   

Current challenges: diagnosis and treatment.

Like many other neurodegenerative diseases, the exact cause and pathophysiology of ALS are unknown, resulting into challenges in accurate diagnosis and developing effective therapies. Clinical assessment, which is the only available strategy to detect ALS, usually detects the disease at a mature stage, leaving providers and patients with little choices to treat the disease or even manage the symptoms, especially for the sub-group of ALS patients who experiences a rapid disease progression. Crucially, this detection strategy is only reasonably accurate for late stage patients (>1 year after the onset of disease symptoms); for early stage patients the accuracy drops to ~50%, while making it completely ineffective for asymptomatic patients. So the need of early (preferably pre-symptomatic) and accurate diagnosis of ALS for timely and effective disease management can be easily understood, but it can have much broader impact. An early or pre-symptomatic diagnosis with biomarker precision would enable robust trial design with improved patient classification and inclusion strategy -- impacting the probability of technical success in developing effective drugs and identifying their target patient populations. So, in a way, the challenges associated with diagnosis and therapy developments are different faces of the same puzzle and the success in one is highly dependent on the other.         

Potential strategy to detect ALS.

The first gene that has been identified in association to ALS is called superoxide dismutase 1 or SOD1. The main role of SOD1 is to control superoxide concentration in human body; elevated levels of superoxide can cause major cellular damage. Certain mutations of SOD1 is known to cause misfolding -- unnatural 3D conformations that inhibit a protein's natural function -- eventually leading to ALS. ALS patients with genes corresponding to these mutations of SOD1 are classified as SOD1-ALS, the predominant type of familial ALS (fALS). About 2% of all ALS patients fall into this category, while sporadic ALS (sALS) accounts for ~90% of all cases; no genetic mutation has been associated with sALS. Interestingly, in some recent studies on sALS patients, SOD1 have been found to behave similarly to that of mutated SOD1 -- leaving room for the argument that misfolded SOD1, whether caused by mutation or environmental factors, is correlated to ALS beyond the SOD1-ALS variation. This is the "core" hypothesis behind our strategy to detect ALS. We are developing a spectroscopic method to identify SOD1 misfolding and the method is agnostic to SOD1 mutation status. It is a non-invasive method, requiring ~1mL blood (nanomolar concentration of SOD1) and based on our observations so far, detects SOD1 misfolding with 100% accuracy.       

Current findings.

The method has been validated so far against lab-expressed pure SOD1 proteins (wild-type and mutants) and healthy patient blood samples. SOD1 primarily exists as a dimer -- leaving the final adduct with two copper (Cu2+) centers. In our method, which employs electron spin resonance (ESR) pulsed dipolar spectroscopy (PDS), we can measure the distance between the Cu2+ centers in SOD1. Proteins are flexible molecules and hence, their dynamic structures consist of many conformations -- differing from the "average protein structures." Therefore, distance measurements between any two residues or atoms in a protein (probes), in this case the two Cu2+ centers in SOD1, produce a distance distribution. The peak(s) and width of the distribution are associated with the average protein structure and flexibility in the region between the probes, respectively. One key point is that the probe must be ESR active to enable distance measurement by ESR PDS and in case of SOD1, the naturally occurring Cu2+ centers are indeed ESR active. So far, we have determined a narrow Cu2+--Cu2+ distance distribution for the wild-type (healthy) SOD1 with a well-defined peak position. Interestingly, for 9 SOD1 mutants that are associated with genetic ALS, the distance distributions become significantly broader compared to the wild-type result. We have already applied the method on healthy human blood samples and found narrow distance distributions similar to that of the lab-expressed wild-type SOD1 with high reproducibility. These observations provide sufficient preliminary validations to implement the method on ALS patient blood samples.  

What's next?

The immediate goal is to procure patient blood samples -- both SOD1-mutated fALS and sALS. We expect to detect SOD1 misfolding in SOD1-mutated fALS patient samples. Results from the experiments on the sALS samples will be particularly important for feasibility assessment of our method in detecting ALS beyond the SOD1-mutated fALS cases. Based on the analysis, we may further attempt to correlate the ESR PDS results to other relevant patient attributes -- for example, rate of disease progression or symptomatic vs. asymptomatic cases.