What This Means
This research tested whether a drug called mitiperstat, which blocks an enzyme called myeloperoxidase (MPO), could help people with a type of heart failure where the heart muscle pumps adequately but is too stiff. The idea behind the treatment was that MPO produces harmful chemical substances that reduce the availability of nitric oxide, stiffen heart muscle cells, and cause scarring — all of which are thought to contribute to this type of heart failure. The study enrolled 711 patients and randomly assigned them to receive one of two doses of mitiperstat or a placebo (inactive treatment) for 48 weeks, measuring whether symptoms and exercise ability improved after 16 weeks.
The results showed that mitiperstat did not improve patients' heart failure symptoms as measured by a standard patient questionnaire (KCCQ-TSS), nor did it improve how far patients could walk in 6 minutes. Additionally, no improvements were seen in any of the other measures tested, including markers of heart stress in the blood (natriuretic peptides), inflammatory markers, or heart structure and function on ultrasound. The drug was generally well tolerated — side effects and serious complications were similar between the mitiperstat and placebo groups — though a skin rash occurred more often in patients taking mitiperstat (3.6%) compared to placebo (0.4%).
This research suggests that blocking MPO with mitiperstat, despite a strong biological rationale, does not translate into clinical benefit for patients with this form of heart failure. These findings highlight how difficult it remains to develop effective treatments for heart failure with preserved ejection fraction, and raise questions about whether MPO inhibition is an effective therapeutic target for this condition, or whether different patient populations, doses, or treatment strategies might need to be explored.