Inhibiting granulocyte/macrophage–colony stimulating factor (GM-CSF) with mavrilimumab prevented some patients with severe COVID-19 pneumonia and hyperinflammation from needing mechanical ventilation and reduced their risk of dying versus placebo in a phase 2 study.
There was no difference in outcomes between the two doses of mavrilimumab used in the trial (6 mg/kg or 10 mg/kg) and combined data showed a higher percentage of patients achieving the primary endpoint of being alive and free of mechanical ventilation at 29 days, at 87%, versus placebo, at 74%.
The P value was 0.12, “which achieved the prespecified evidentiary standard of 0.2,” according to, vice president of clinical research and development at Kiniksa Pharmaceuticals in Lexington, Mass.
Importantly, there was a 61% reduction in the risk of dying if patients had received mavrilimumab rather than placebo, she reported at the annual European Congress of Rheumatology. Mortality at day 29 was 21% in the placebo arm but just 8% in the combined mavrilimumab arms (P = .07).
Hendrik Schulze-Koops, MD, called it a “surprising study” and that “the outcome is very spectacular” in his short appraisal of the study during the Clinical Highlights session on the final day of the congress.
Mavrilimumab was “a compound that we would not have thought that would have such an impact on the outcome of COVID-19 infected patients,” Dr. Schulze-Koops of Ludwig Maximilian University of Munich added.
In this small study, “there was a consistent suggestion of a biological effect across key endpoints,” Richard Conway, MBChB, PhD, a consultant rheumatologist at St. James’s Hospital in Dublin, pointed out in an interview.
“Similar to tocilizumab, the benefits with mavrilimumab appear to be in addition to those seen with glucocorticoids, as 96% of patients received dexamethasone,” Dr. Conway observed. Furthermore, nearly one-third received antiviral or remdesivir treatment.
“This study was likely underpowered to assess a clinically meaningful benefit,” he said, adding that “there is insufficient evidence at present to begin using mavrilimumab as an alternative to currently available agents.” That said, “these results are promising for future studies.”
Rationale for GM-CSF inhibition with mavrilimumab in COVID-19 pneumonia
“The cytokine GM-CSF is vital to both lung homeostasis and regulation of inflammation in autoimmunity,” Dr. Pupim explained.
She added that “GM-CSF is implicated in the mechanism of aberrant immune cell infiltration and activation in the lungs, and it may contribute to respiratory failure and death in patients with severe COVID-19 pneumonia and systemic hyperinflammation.”
The efficacy and safety of blocking GM-CSF with mavrilimumab have been shown previously in phase 2 studies in other diseases, Dr. Pupim noted. This includes patients with rheumatoid arthritis and those with giant cell arteritis.
“It was hypothesized that GM-CSF receptor–alpha blockade may reduce infiltration of pathogenic cells into the lung and may suppress inflammation in COVID-19 pneumonia in hyperinflammation,” she explained.