AURORA, COLO. –
“We should be very excited about these results, which are better than expected and fundamentally tackle autoimmunity,” said study investigator Gavin Giovannoni, MD, PhD, chair of neurology at the Blizard Institute of Barts, London, and the London School of Medicine and Dentistry. “It will be interesting to see if this treatment reestablishes immune tolerance and induces long-term remission,” he said.
The late-breaking study was presented at the annual meeting of the Consortium of Multiple Sclerosis Centers.
Significant lesion reduction
With a variety of disease-modifying therapies available for MS, frexalimab would be unique as a novel second-generation monoclonal antibody designed to block the costimulatory CD40/CD40L cellular pathway. Importantly, the mechanism is believed to potentially modify T- and B-cell activation and innate immune cell function, for an effect of reducing inflammation without depleting B cells.
To investigate the drug’s efficacy and safety, Dr. Giovannoni and his colleagues conducted the phase 2, multicenter trial, in which 129 participants with relapsing MS were randomized to one of four groups – high-dose frexalimab (n = 52); low-dose frexalimab (n = 51); or placebo (n = 12 high-dose, n = 14 low-dose), for the 12-week placebo-controlled period, followed by an open-label extension period that is currently ongoing.
Among 125 participants who completed the study’s 12-week double-blind period, those receiving high-dose frexalimab had an 89% greater reduction in the number of new gadolinium-enhancing T1-lesions, compared with the pooled placebo group (P = .0004), meeting the study’s primary endpoint. After 24 weeks, as many as 96% of those in the high-dose frexalimab arm were free of gadolinium-enhanced T1 lesions.
The frexalimab low-dose group also had a lower, but significant, reduction in the number of new gadolinium-enhanced T1-lesions of 79% versus the pooled placebo group (P = .0021).
Both of the frexalimab groups also had reductions in enlarging T2-lesions and total gadolinium-enhanced T1-lesions.
In the high-dose group, data on 38 participants with open-label data from week 37 showed no new gadolinium-enhanced lesions.
In terms of safety, frexalimab was well tolerated over the 12-week study, with headache and COVID-19 reported among 4% or fewer participants. No serious adverse events were reported.
Looking ahead at safety, Dr. Giovannoni noted that “a known unknown is infections, but this is a problem with all therapies that work via immunosuppressive mechanisms, not only therapies targeting CD40L.” That said, “we didn’t see a big infection signal in the trial, which is reassuring. It also shows the immune system has built-in redundancy and many mechanisms to fight infections,” he added.
In his newsletter, Dr. Giovannoni characterized the study’s results as “strikingly positive,” adding that they “are the most exciting to emerge in MS in the last 12-24 months.”
Overall, “these are the first randomized controlled phase 2 data for a CD40L inhibitor in MS and indicate potential for further development of frexalimab as a high-efficacy therapy,” the investigators noted. “Frexalimab led to a pronounced reduction of new gadolinium-enhancing lesions by 3 months and was well-tolerated,” they added.