BridgeBio’s investigational cardiomyopathy molecule acoramidis (AG10) fell short of the phase 3 finish line last week, when it not only failed its primary endpoint, but was associated with decreases in a functional measure of cardiac fitness relative to placebo.

The drug, a potential treatment for transthyretin amyloid cardiomyopathy (ATTR-CM), had good phase 2 outcomes on both biomarkers and long-term survival. But its failure to improve functional outcomes was a big blow, said Neil Kumar, founder and CEO of BridgeBio.

“This result is disappointing and baffling. I am, along with many others, searching for answers” in the drug’s failure to improve the 6-Minute Walking Distance (6MWD), a measure of cardiac function, he said.

The study did return positive results in overall quality of life and some hints of survival benefit at 12 months, so BridgeBio isn’t throwing the molecule in the dustbin yet. The Data Safety Monitoring Committee recommended that the company complete Part B of the study — to assess all-cause mortality and cardiovascular hospitalizations at month 30.