Neurofilament light chain (NfL) is a well-known and useful biomarker for multiple sclerosis (MS) disease activity, but its association with disease progression is not well understood. A new analysis of MS patients in California’scohort suggests that
“We see evidence for accelerated neuroaxonal damage in the year preceding the first diagnosis of the progression events, [but] only if they were associated with evidence of focal inflammatory activity – that can be either clinical or imaging evidence,” said Ahmed Abdelhak, MD, during a presentation of the study at the annual meeting of the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS).
“By the time we diagnose the EDSS progression, it’s already too late. Every damage or any accelerated neuroaxonal damage that has happened in association with this event already took place around a year ago. I think [this has] huge implications for the designing of clinical trials,” said Dr. Abdelhak, who is a postdoctoral researcher at the University of California, San Francisco.
In the study, researchers analyzed data from 609 MS cases, with a total of 3,906 office visits. The median age was 42 years, and 69.6% were female. Median disease duration was 6 years.
They examined the association between NfL scores and confirmed disease worsening, as recorded by an increase in EDSS score. There was an increase in NfL age-adjusted z score about 12 months in advance among patients with a progression association with a relapse in the past year, compared with individuals who did not experience disease progression. There was also a more modest increase among individuals who had disease progression without a recent relapse, but this was not statistically significant.
“Our findings suggest that the association between NfL levels and EDSS worsening is most prominent in the setting of relapse-associated events,” said Dr. Abdelhak.
Clinical implications and audience skepticism
During the Q&A following the talk, session moderator Charlotte Teunissen, PhD, professor of neurochemistry at Amsterdam University Medical Center, asked about the clinical implication of the finding. “It seems that you concluded that axonal damage has been done before the progression starts. Is that your conclusion? So it means that there is no option to interfere anymore, consequently.”
Dr. Abdelhak responded: “I think that’s a very important interpretation of the data, which I’m sure is a relatively new way of thinking about it. That means, indeed, that when we see these patients, measuring NfL wouldn’t deliver any additional value because they don’t differ between the groups at the time of EDSS worsening. And there is probably nothing more we can do about this event. But it’s still very important to know that any therapeutic intervention has also the need to prevent future disability progression, future neuroaxonal damage, but regarding what has happened already, I’m a little bit skeptical if we will be able to change anything.”
Dr. Teunissen expressed skepticism that there was no further neurodegeneration following the spike in NfL, and pointed out an important caveat, which was the study’s reliance on NfL. “You base your conclusions on what you observe for NfL, and it’s a far-fetched conclusion that there is no further axonal damage ongoing. Maybe NfL is just one marker, and it’s not the best biomarker to measure progression,” she said.
Dr. Abdelhak conceded that it will be necessary to confirm the findings with other biomarkers of neurological injury. Even different subunits of the NfL protein have been shown to have different dynamics in other neurological conditions. “So the data we have give definitely an incomplete picture because we [know] nothing about the other biomarkers of neuroaxonal injury, including the other subunits of NfL,” he said.
Later in the Q&A, Alasdair Coles, MD, professor of neurology at University of Cambridge (England), spoke from the audience. He suggested that the findings could be seen as dispiriting for clinicians. “Would the panel agree that actually for a clinician this is all rather disappointing, because none of these markers are telling us anything that we don’t otherwise know by examining the patient and doing scans?”
“I can attempt to tackle that provocative question,” replied Elias Sotirchos, MD, who also presented on an association between NfL and brain atrophy research during the session. He pointed out that all clinical tests are imperfect, and suggested that NfL isn’t something to be used in isolation. It could be useful when patients are experiencing new symptoms, or worsening symptoms, and in combination with MRI results. “My interpretation of NfL is that it does have incremental value, telling us which patients have lesions that are more destructive, potentially, given all of these consistent associations with brain atrophy and disability progression over time,” said Dr. Sotirchos, who is an assistant professor of neurology at Johns Hopkins Medicine, Baltimore.
Dr. Abdelhak and Dr. Teunissen have no relevant financial disclosures. Dr. Sotirchos has financial relationships with Alexion, Viela Bio, Horizon Therapeutics, Genentech, and Ad Scientiam.