according to investigators. The biomarker appears to have a stronger correlation with disability in people with nonactive disease, compared with those with active disease. These data were presented at the Joint European Committee for Treatment and Research in Multiple Sclerosis–Americas Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS–ACTRIMS) 2020, this year known as MSVirtual2020.
Astroglial injury and activation is one of the characteristic features of progressive MS. Following such injury, GFAP is released into the cerebrospinal fluid and blood.
“It may be that GFAP plays an especially important role in patients without focal inflammatory activity and is more associated with insidious progression,” said, head of the MS center at University Hospital Basel (Switzerland). “This [finding] needs to be investigated further within the same cohort, but also [within] additional well-characterized other cohorts.”
Dr. Kuhle and colleagues examined GFAP as a prognostic biomarker of disability worsening by analyzing data for patients with active or nonactive secondary progressive MS who participated in the phase 3 EXPAND study, which compared siponimod with placebo. In this post hoc analysis, the investigators quantified baseline GFAP in plasma samples using single-molecule array technology. They categorized GFAP as high or low according to the gender-stratified 80th percentile.
Dr. Kuhle’s group assessed the effect of GFAP on time to an Expanded Disability Status Scale score of 7 (i.e., restriction to wheelchair) using a Cox regression model adjusted for age, gender, disease duration, treatment, relapses in the 24 months prior to study start, and baseline EDSS. In addition, they performed subgroup analyses in patients with active secondary progressive MS and those with nonactive secondary progressive MS. They defined active disease as having relapses at 24 or fewer months before study entry or gadolinium-enhancing T1 lesions at baseline. Participants without these characteristics were classified as having nonactive disease. The investigators also stratified the results by gender.
Correlation was strongest in nonactive disease
The current analysis included samples for 1,405 of the 1,651 patients who had been randomly assigned to treatment in the EXPAND study. The median GFAP level was 119.6 pg/mL among men and 141.4 pg/mL among women.
The risk of reaching an EDSS score of 7 was higher in patients with a high baseline GFAP level. Of 281 (12.1%) participants with a high baseline GFAP level, 34 reached this endpoint, compared with 54 of 1,117 (4.8%) participants with a low baseline GFAP level. For patients with a high GFAP level at baseline, the hazard ratio of this outcome was 1.96.
Subgroup analyses indicated that the increased risk of reaching an EDSS score of 7 was seen mainly in women. Of 169 women (13.6%) with high baseline GFAP level, 23 reached this endpoint, compared with 34 of 673 women (5.1%) without a high baseline GFAP level (HR, 2.22). Among men, the difference was not significant. Of 112 men (9.8%) with a high baseline GFAP level, 11 reached an EDSS score of 7, compared with 20 of 444 men (4.5%) without a high baseline GFAP level (HR, 1.45). The reason for this sex difference is unknown, said Dr. Kuhle. “A next important step is to ensure this [finding] is not influenced by other hidden factors.”
Dr. Kuhle and colleagues also found that the increase in risk of reaching an EDSS score of 7 was mainly observed in patients with nonactive secondary progressive MS. Among 133 such patients with a high baseline GFAP level, 14 (10.5%) reached this endpoint, compared with 22 of 570 patients (3.9%) without a high baseline GFAP level (HR, 3.40). The difference among patients with active secondary progressive MS was not significant (20 of 144 patients [13.9%] with high baseline GFAP level, compared with 30 of 521 patients [5.8%] without a high baseline GFAP level; HR, 1.58). Dr. Kuhle and colleagues found similar trends in the associations between baseline GFAP levels and time to 6-month confirmed disability progression, but these trends were less pronounced.
“The measurement of plasma or blood neurofilament light chain [NfL] is certainly closer to a potential clinical application than [the measurement of] GFAP,” Dr. Kuhle admitted. “However, highly sensitive platforms open the field to the fascinating possibility of finding meaningful biomarkers in the blood compartment in MS.” This development should be developed further. It is necessary to validate the significance of GFAP measures in individual patients and describe them with greater precision before they can be applied clinically. It also is necessary to create normative data and explore for the impact of other variables like age and comorbidities, he added.
“We are currently analyzing the EXPAND data further to see which characteristics at baseline and at end of study are driving plasma GFAP concentrations,” said Dr. Kuhle. “We also need to investigate whether progression events are captured accurately by GFAP in plasma. It will also be important to combine the GFAP data with NfL measures that are already available in this cohort.”
Study addresses a clinical need
“There is great need for a reliable, easy-to-measure, and relevant fluid biomarker for use in MS,” said, staff neurologist at the Cleveland Clinic’s Mellen Center for MS. Neurofilaments have been a leading candidate among biomarkers, but researchers are exploring other candidates as well. An advantage of the present study is that Dr. Kuhle and colleagues examined a large number of patients with secondary progressive MS who underwent highly structured follow-up over several years, Dr. Fox said.
“What is most interesting is that the predictive capacity was greater in nonrelapsing secondary progressive MS, and so may have advantages over neurofilament in this group of patients,” he added. “Currently, GFAP is a research test and isn’t available for clinical practice.”
Researchers should investigate other ways in which GFAP is related to future disease activity (e.g., in the form of relapses or new MRI lesions) as well as to other measures of disability progression besides restriction to a wheelchair, said Dr. Fox. “Future research needs to examine whether this biomarker is helpful at the individual patient level. Can it guide a patient’s clinician toward treatment recommendations?”
This study was funded by Novartis. Neither Dr. Kuhle nor Dr. Fox had no relevant disclosures to report.
This article was updated 9/14/2020.