NASHVILLE, TENNESSEE — , new trial data suggested.
Researchers found a near absence of new brain lesions at 48 weeks in patients on the highest dose. At this level of disease suppression, there was no evidence of increased infection risk, which investigators said might relate to its mechanism of action. In addition, there were no thrombotic events, which is what defeated a first-generation drug in this same class.
Among those initially randomly assigned to receive 1200 mg every 4 weeks, 96% were free of new gadolinium-positive (Gd+ T1) lesions at 48 weeks, reported investigator Yang Mao-Draayer, MD, PhD, director of Clinical and Experimental Therapeutics at the Oklahoma Medical Research Foundation’s Multiple Sclerosis Center of Excellence, Oklahoma City. Annual relapse rates were also low.
The findings were presented at the annual meeting of the Consortium of Multiple Sclerosis Centers.
No Effect on Lymphocyte Count
As previously reported, 12-week frexalimab results were noteworthy because they provided validation for CD40L as a target in the control of MS. One of the unique features of this therapy relative to many other immunomodulatory therapies is that it has shown little, if any, effect on lymphocyte counts or immunoglobulin levels.
In the double-blind randomized phase 2 trial, 125 patients with MS of all other MS therapy were randomized in a 4:4:4:1 ratio to 1200-mg frexalimab administered intravenously every 4 weeks after a loading dose, to 300-mg frexalimab administered subcutaneously every 2 weeks after a loading dose, or to one of the two matching placebo arms.
For the primary endpoint of new Gd+ T1 lesions at the end of the blinded study, the rates at week 12 were 0.2 and 0.3 in the higher- and lower-dose treatment groups, respectively, and 1.4 in the pooled placebo groups.
At 48 weeks, the results were even better. From 12 weeks, the rate of Gd+ T1 lesions in the high-dose group continued to fall, reaching 0.1 at week 24 and 0.0 at week 48. In the lower-dose group, there was also a stepwise decline over time with a value of 0.2 at week 48. The annual relapse rate at week 48 was 0.4.
Reengineered Agent
In the placebo groups, the same type of suppression of disease activity was observed after they were switched to active therapy at the end of 12 weeks.
By 24 weeks, the number of new Gd+ T1 lesions had fallen to 0.3 in placebo patients switched to the higher dose and 1.0 in those switched to the lower dose.
By week 48, the rates were 0.2 in both of the switch arms.
The proportions of patients free of new Gd+ T1 lesions at 48 weeks were 96% in the group started and maintained on the highest dose of frexalimab, 87% in those started and maintained on the lower dose, 90% in those started on placebo and switched to the highest dose of frexalimab, and 92% of placebo patients switched to the lower dose.
“T2 lesion volume from baseline through week 48 was stable in patients who continued receiving frexalimab and decreased in placebo participants after switching to frexalimab at week 12,” Dr. Mao-Draayer reported.
The CD40-CD40L co-stimulatory pathway that regulates both adaptive and innate immune responses has been pursued as a target for MS therapies for decades, Dr. Mao-Draayer said.
A first-generation monoclonal antibody directed at elevated levels of CD40L, which is implicated in the inflammation that drives MS, showed promise but was abandoned after it was associated with an increased risk for thromboembolic events in a phase 1 trial, she said.
However, the second-generation agent was engineered to avoid an interaction with platelets, which played a role in the risk for thrombosis associated with the failure of the earlier drug.
As with the first-generation agent, frexalimab had little or no impact on lymphocyte count or immunoglobulin G and immunoglobulin M levels. Both remained stable during the 12-week controlled trial and through the ongoing open-label extension, Dr. Mao-Draayer said.
This might be a factor in the low level of adverse events. Most importantly, there have been no thromboembolic events associated with frexalimab so far, but the follow-up data also show rates of infection and other events, such as nasopharyngitis, that were comparable with placebo in the 12-week controlled trial and have not increased over longer-term monitoring.
Such adverse events as headache and COVID-19 infection have also occurred at rates similar to placebo.
Two phase 3 trials are underway. FREXALT is being conducted in relapsing-remitting MS. FREVIV has enrolled patients with nonrelapsing secondary progressive MS.