Qalsody, Biogen’s therapy for a specific form of amyotrophic lateral sclerosis, in April became the first neurological drug whose accelerated approval was based on a levels of a surrogate biomarker in patients’ blood. This is great news for Quanterix, maker of the leading blood test for the biomarker in question, neurofilament light chain.
“Blood is a great proxy for whether the drug is working the way you’d like it to work,” says Masoud Toloue, chief executive of Quanterix. The group hopes that Qalsody’s approval will presage the use of more blood biomarkers for approval decisions and other applications. But some clinical data have been questionable, and much will depend on Qalsody’s confirmatory trial.
Known generically as tofersen and initially developed by Ionis, Qalsody was approved by the FDA in April for ALS patients who have a mutation in the superoxide dismutase 1 gene. The approval was based on the drug’s proven ability to reduce blood levels of neurofilament light chain (NfL). NfL is a rod-like protein that functions as an internal scaffold for neurons, Toloue explains, and when neurons become damaged or die, as happens in ALS and other brain disorders, they shed NfL into the cerebrospinal fluid and blood. …