Plonmarlimab, a GM-CSF-neutralizing antibody, for macrophage activation syndrome.

What was studied

This study tested a drug called plonmarlimab. It is an antibody that blocks GM-CSF. It was given to people with macrophage activation syndrome, or MAS. MAS is a rare and grave problem linked to rheumatic disease. All 18 people had MAS that failed or came back after high-dose steroid drugs. This was a phase 2 trial at many sites, and all got the same drug. Each person got the drug once a week for 8 weeks.

What they found

After 8 weeks, 15 of the 18 people had responded to the drug. The typical time to a response was 2.1 weeks. MAS symptoms eased in a typical time of 1.1 weeks. Steroid doses went down a lot by week 8. No grade 3 or worse infections were seen. Blood levels of ferritin and IL-18 fell fast.

What it means for patients

The authors say the drug showed signs that it works in MAS. They say people generally coped well with it. They also say IL-18 may help show how this drug type acts.

Why it is not certain yet

Only 18 people took part. There was no comparison group of people on other care. Both doctors and patients knew which drug was given. This was a phase 2 trial, so it is an early step. The abstract reports results only up to week 8. The abstract does not list other side effects in detail.

Source

Plonmarlimab, a GM-CSF-neutralizing antibody, for macrophage activation syndrome.

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