At week 12, there was an 89% reduction in new gadolinium (Gd)-enhancing T1 brain lesions — a standard measure of active inflammation in MS – in the high-dose frexalimab group and a 79% reduction in the low-dose treatment group compared with placebo, meeting the study’s primary endpoint.
The effects of frexalimab were sustained over time, “especially at the high dose of frexalimab where 96% of patients were free of new active lesions after 24 weeks of treatment,” first author Patrick Vermersch, MD, PhD, University of Lille, CHU Lille, France, said in a news release.
The full results were published online on in The New England Journal of Medicine, following presentation of preliminary data at the Consortium of Multiple Sclerosis Centers 2023 Annual Meeting.
‘Unambiguous Benefit’
Frexalimab blocks the costimulatory CD40/CD40L pathway, which regulates both adaptive and innate immune responses, and has been implicated in the pathogenesis of MS.
“Through this unique upstream mechanism of action, frexalimab has the potential to address both acute and chronic neuroinflammation in MS, without causing lymphocyte depletion,” a Sanofi press statement noted.
The phase 2 study enrolled 129 adults (mean age, 36 years; 66% women) with relapsing MS, 30% of whom had Gd-enhancing lesions at baseline.
Participants received 1200 mg of frexalimab administered intravenously every 4 weeks (with an 1800-mg loading dose; n = 52), 300 mg of frexalimab administered subcutaneously every 2 weeks (with a 600-mg loading dose; n = 51), or matching placebos for each active treatment (n = 12 and n = 14, respectively).
All but four patients completed the 12-week double-blind period and entered the open-label period.
The primary end point was the number of new Gd-enhancing T1-weighted lesions seen on MRI at week 12 relative to week 8.
At week 12, the adjusted mean number of new Gd-enhancing T1 lesions was 0.2 and 0.3 in the high- and low-dose frexalimab groups, respectively, compared with 1.4 in the pooled placebo group.
The rate ratios, as compared with placebo, were 0.11 in the high-dose group and 0.21 in the low-dose group, corresponding to 89% and 79% reductions in the high- and low-dose groups, respectively.
On the secondary endpoint of number of new/enlarging T2-weighted lesions at week 12, rate ratios in the high- and low-dose groups were 0.08 and 0.14, respectively, corresponding to 92% and 86% reduction in the high- and low-dose treatment groups vs placebo.
The effects were sustained over time across both active treatment groups.
Frexalimab also lowered plasma levels of neurofilament light chain, a biomarker of neuroaxonal damage in MS, as well as plasma levels of CXCL13, a biomarker of inflammatory activity.
Phase 3 Trials Underway
The authors noted that the trial was too brief and small to draw conclusions regarding clinical outcomes. However, during the 12-week double-blind period, no relapses occurred in the high-dose frexalimab group, whereas relapses occurred in roughly 4% of those in the low-dose frexalimab group and the pooled placebo group.
There was no change from baseline to 12 weeks in median scores on the Expanded Disability Status Scale in any study group.
No serious or severe adverse events or deaths were reported during the double-blind period. There were no thromboembolic events — a concern with first-generation anti–CD40L antibodies.
Depletion of lymphocytes was not observed. More infections were observed with frexalimab than with placebo, but no serious infections occurred during 24 weeks of frexalimab treatment. The most common adverse events were COVID-19 and headache. All cases of COVID-19 were uncomplicated and mild to moderate in severity.
Bolstered by the promising phase 2 data, Sanofi has initiated two phase 3 studies assessing frexalimab in relapsing MS and non-relapsing secondary progressive MS.
‘A High Bar for Any New Treatment’
In an accompanying editorial, Stephen L. Hauser, MD, with UCSF Weill Institute for Neurosciences, San Francisco, California, wrote that the results “appear clear, although the clinical significance is uncertain — clear because there was an unambiguous benefit with regard to short-term MRI outcomes in patients who received frexalimab as compared with those who received placebo and because a generally low level of MRI activity persisted during an additional 12-week open-label extension period.”
If the findings hold with longer-term use, Dr. Hauser continued, “it seems likely that there will be a protective effect of frexalimab therapy with regard to relapses of multiple sclerosis.”
Dr. Hauser noted, however, that the “striking clinical benefits and safety profile of the available high-efficacy therapies for relapsing multiple sclerosis create a high bar for any new treatment.”
“In this trial, the MRI outcomes with frexalimab therapy were impressive but appear to be less complete than those with anti-CD20 agents, although trials of different agents cannot be directly compared.”
“Even if future studies show frexalimab to be competitive with currently available therapies for relapsing multiple sclerosis, the paramount need is for more effective therapy against progression,” Dr. Hauser wrote.
While the current trial was neither designed nor powered to assess benefits against progressive MS, “progression is where the true clinical value of frexalimab, and its place in the therapeutic armamentarium against multiple sclerosis, will need to be defined,” Dr. Hauser concluded.
The study was supported by Sanofi. Disclosures for authors and editorialist are available at NEJM.org.
A version of this article first appeared on Medscape.com.