Researchers at Karolinska Institutet in Sweden have taken the first steps in testing a new oral medication for people living with chronic heart failure and the early results look encouraging, according to a study published in The Lancet. The drug, called AC01, appears to be safe, well-tolerated, and may even help the heart pump more effectively.
The Problem with Current Treatments
Heart failure with reduced pumping capacity is a serious condition in which the heart can’t push blood around the body as effectively as it should. Even with today’s best treatments, many patients see their condition deteriorate over time. And while there are drugs that can boost the heart’s pumping power, they often come with serious downsides, including dangerous changes to heart rhythm and blood pressure.
The new AC01 is designed to strengthen the heart’s contractions through a completely different biological pathway than the drugs we currently use, which researchers hope will mean fewer side effects.
How the New Drug Works
AC01 targets something called the ghrelin receptor. Ghrelin is a hormone involved in regulating hunger and it also affects the release of growth hormone. What’s interesting is that ghrelin receptors are found in heart muscle too, which makes them a potential new target for treating heart problems. By acting on these receptors, AC01 aims to give the heart a helpful boost without the risks that come with traditional heart-stimulating medications.
What the Study Looked At
The trial was a small and early-stage phase 1b/2a study. It involved only 58 patients with stable, chronic heart failure whose hearts had reduced pumping capacity. The study was randomised and placebo-controlled, meaning some participants got the real drug while others received a dummy pill, and neither the patients nor the researchers knew who got what.
Participants took either AC01 or a placebo at different doses for either 7 or 28 days. The main goal at this stage wasn’t to prove the drug works, but to find out whether it’s safe and well tolerated.
Encouraging Early Results
The preliminary findings were positive. Patients tolerated the drug well, and there were no serious side effects linked to AC01. Importantly, the researchers didn’t see any of the dangerous heart rhythm problems or blood pressure issues that often plague this type of medication.
There were also some hopeful hints that the drug might be doing what it’s designed to do. Extra analyses suggested signs of improved heart function, including an increase in stroke volume (the amount of blood pumped with each beat) and cardiac output (the total amount of blood the heart pumps per minute).
It’s worth being cautious here, though. The study was small and short, and the team was careful not to oversell the results. “This is an early study with a limited number of patients, but the results suggest that AC01 can be administered safely to people with heart failure. The findings now justify further studies to investigate whether the signals of improved heart function that we have observed can lead to clinical benefit in larger and longer studies,” said Lars Lund, first author and professor at the Department of Medicine, Solna, Karolinska Institutet, and senior consultant cardiologist at Karolinska University Hospital.
What Happens Next
These early results give researchers good reason to move ahead with bigger, longer studies with more participants. Those next trials will be needed to find out whether AC01 doesn’t just look safe and promising on paper but actually makes a real difference for patients, helping them feel better, live longer, or avoid being hospitalised.
Lars H Lund, Arantxa Barandiaran Aizpurua, Entela Bollano, Oscar Braun, et al. Safety, tolerability, and haemodynamic effects of the ghrelin receptor agonist AC01 in patients with chronic heart failure: a randomised, double-blind, placebo-controlled, phase 1b/2a study, The Lancet, online June 24, 2026, doi: 10.1016/S0140-6736(26)00904-9