ALS drug PrimeC shows safety and hints of benefit in phase 2b trial - with an unusual signal in speech

Amyotrophic lateral sclerosis strips away motor function methodically - first the hands, then the legs, then speech, then breathing. Most people diagnosed with ALS die within three to five years. The few approved treatments slow progression modestly at best. Any drug that shows even preliminary signs of meaningful benefit gets intense attention.

PrimeC, an oral combination of celecoxib (an anti-inflammatory) and ciprofloxacin (an antibiotic), has now produced those preliminary signs. The PARADIGM phase 2b trial, published in JAMA Neurology, found the drug safe and well-tolerated, with exploratory efficacy signals that the investigators say justify advancing to a phase 3 study.

Trial design and safety

The multicenter trial randomized 68 participants with ALS in a 2:1 ratio to PrimeC or placebo for six months, followed by a 12-month open-label extension in which all participants received the active drug. The primary objective was safety assessment, and on that front, PrimeC performed well. Drug-related adverse events were more common in the treatment arm (20.0% versus 4.3% for placebo), but most were mild to moderate and temporary.

The study was led by Merit Cudkowicz, Executive Director of Mass General Brigham Neuroscience Institute, and Jeremy Shefner, professor of neurology at Barrow Neurological Institute.

Functional scores that widened over time

The trial was not designed or powered to prove efficacy, but the exploratory functional data drew attention. Participants taking PrimeC scored 2.23 points higher on the ALS Functional Rating Scale Revised (ALSFRS-R) at six months compared to placebo. That is a modest difference on a 48-point scale. But by 18 months - after the placebo group had also switched to PrimeC during the open-label phase - participants who had been on the drug from the start scored 7.92 points higher on average than those who started later.

The benefit was particularly pronounced for bulbar function - the ability to speak and swallow, which is controlled by motor neurons in the brainstem. This specificity is noteworthy because different ALS treatments may preferentially affect different functional domains, and bulbar decline is among the most distressing symptoms for patients and families.

Early, continuous treatment was also associated with a 64% reduced risk of ALS-related complications, including hospitalization, respiratory failure, or death.

Biomarker evidence of target engagement

PrimeC was designed to target three pathological processes in ALS: neuroinflammation, excess iron accumulation, and abnormal microRNA activity. The biomarker data offered some support for all three mechanisms. Participants initially assigned to PrimeC had lower levels of ferritin, the iron storage protein, suggesting the drug affected iron metabolism. Treatment was also associated with lower levels of microRNA molecules previously linked to ALS pathology.

However, neurofilament light chain - a widely used biomarker of neuronal damage in ALS - showed no treatment-related difference between groups. This is a notable gap because neurofilament light is the most established fluid biomarker for tracking ALS progression, and its lack of response raises questions about whether PrimeC is protecting motor neurons or affecting the disease through a different pathway.

Why cautious optimism is the right register

With 68 participants, the trial is too small to draw firm efficacy conclusions. The open-label extension, while valuable for long-term safety data, introduces bias because participants and clinicians know who is receiving the drug. The 7.92-point difference at 18 months is striking, but it compares early starters to late starters rather than active drug to placebo over the full period.

The ALS field has been burned repeatedly by promising phase 2 results that collapse in larger trials. The disease's variable progression rate means small studies can produce apparent treatment effects that are actually driven by chance imbalances in disease severity between groups. Only a well-powered phase 3 trial with adequate controls can determine whether PrimeC's signals represent genuine disease modification.

Shefner noted that the consistency across multiple clinical endpoints and multiple biomarkers is what distinguishes this result from many earlier ALS studies. Cudkowicz emphasized the urgency of following up for patients and families. The PARADIGM trial was funded by NeuroSense Therapeutics, the company developing PrimeC, which played a role in study design, data analysis, and manuscript preparation - a standard arrangement for industry-sponsored trials but one that warrants acknowledgment when interpreting results.