An early clinical study suggests that a new oral drug is safe and well-tolerated in patients with chronic heart failure, say researchers at Sweden’s Karolinska Institutet, whose findings were published last week in The Lancet.
Heart failure with reduced pumping capacity means the heart struggles to pump blood effectively around the body. Despite current treatments, many patients’ condition worsens over time, and existing drugs that strengthen the heart’s contractions can cause serious side effects, like heart rhythm disturbances and effects on blood pressure.
For their study, the researchers investigated a new drug, AC01, which targets the body’s ghrelin receptor. Ghrelin is a hormone that influences metabolism and growth hormone release, and its receptor is also found in heart muscle. AC01 is intended to strengthen the heart’s pumping ability through a different biological mechanism from traditional heart‑stimulating drugs, thereby reducing the risk of side effects.
The study was a randomised, placebo‑controlled phase 1b/2a trial involving 58 patients with stable, chronic heart failure with reduced pumping capacity. Participants received different doses of AC01 or placebo for either seven or 28 days. The main aim was to assess safety and tolerability.
The results show that the drug was well tolerated. No serious side effects linked to AC01 were reported. The researchers also found no signs of harmful effects on heart rhythm or blood pressure. Exploratory analyses additionally indicated signs of improved heart function, such as increased stroke volume and cardiac output.
“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.
The study was conducted in collaboration with researchers and clinicians in several European countries. The research was funded by pharmaceutical company AnaCardio AB.
Several of the researchers, including the principal investigator, have ties to the company, which are disclosed in the scientific article.
Study details
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
Lars Lund, Arantxa Barandiaran Aizpurua, Entela Bollano et al.
Published in The Lancet on 24 June 2026
Summary
Background
The central problem in heart failure with reduced ejection fraction (HFrEF) is reduced contractility. Existing inotropes are associated with adverse effects. In this exploratory study, we aimed to assess the safety and tolerability of AC01, a novel oral calcium-sensitising inotrope and ghrelin receptor agonist, in patients with HFrEF.
Methods
In this phase 1b/2a, randomised, double-blind, placebo-controlled study, adults aged 18–80 with heart failure for at least six months and an ejection fraction of 40% or lower were enrolled at 14 sites in The Netherlands, the UK, Sweden, and Italy. All patients had a transvenous implantable cardioverter defibrillator for primary prevention, with back-up pacing to protect against excessive bradycardia. Other eligibility criteria included sinus rhythm or permanent, persistent, or paroxysmal atrial fibrillation or flutter (only allowed in phase 2a), with a mean resting heart rate of 55–90 beats per min. Randomisation used permuted blocks, with block sizes of four for phase 1b and three for phase 2a. In phase 1b, patients were enrolled in four sequential dose cohorts and randomly assigned 3:1 to ascending doses of AC01 (0·1 mg, 0·3 mg, 1·0 mg, or 3·0 mg) or placebo twice daily for 7 days. In phase 2a, patients were randomly assigned 1:1:1 to parallel groups receiving 1·0 mg AC01, 3·0 mg AC01 (1·0 mg AC01 on days 1 and 2 and 3·0 mg thereafter), or placebo orally twice daily for 28 days. Patients, study personnel, outcomes assessors, those analysing the data, and the sponsor were masked to treatment assignment. The primary outcome was safety and tolerability. Safety was monitored by physical examination, vital signs, safety laboratory assessments, and 12-lead electrocardiograms (ECGs) periodically during the treatment period and until the end-of-study visit (day 12 in phase 1b and day 42 in phase 2a), and cardiac rhythm was continuously monitored remotely using a patch device until day 9 in phase 1b and until day 4 in phase 2a. Adverse or unexpected events, signs, or symptoms were recorded.
Findings
Between Feb 23, 2023, and Aug 28, 2025, 58 patients (53 [91%] male and five [9%] female patients with a median age of 66·0 years [IQR 60·3–72·0]) were randomly assigned: 32 in phase 1b and 26 in phase 2a. In phase 1b, four cohorts of eight patients were enrolled; in each cohort, six patients were allocated to AC01 and two to placebo, with AC01 dose cohorts of 0·1 mg, 0·3 mg, 1·0 mg, and 3·0 mg. In phase 2a, nine patients were allocated to 1·0 mg AC01, eight to 3·0 mg AC01, and nine to placebo. There were 12 AC01-related adverse events in phase 1b and 18 in phase 2a. There were no AC01-related serious adverse events; one treatment-related serious adverse event of increased high-sensitivity cardiac troponin I concentration occurred in a patient receiving placebo in phase 1b. Mild or moderate treatment-emergent adverse events were reported in 33 (80%) of 41 patients receiving AC01 and 12 (71%) of 17 patients receiving placebo. The most common treatment-emergent adverse events were hypotension, non-sustained ventricular tachycardia, dyspnoea, hyperglycaemia, dizziness or vertigo, and headache. ECG data showed no apparent signs of tachycardia, new-onset tachyarrhythmias, myocardial ischaemia, or morphological or conduction abnormalities. No case of symptomatic hypotension was reported, and there were no apparent effects of AC01 on high-sensitivity cardiac troponin I or NT-proBNP. There were no deaths during the study.
Interpretation
In patients with HFrEF, AC01 over 28 days appeared safe and well tolerated, and no major harms were identified in this early-phase study. These findings support further investigations of AC01 in larger studies.
See more from MedicalBrief archives:
Semaglutide shows heart benefits in key group – global study
Weight loss drug approved for heart disease prevention
Stents ineffective for heart failure patients – landmark seven-year UK trial
SGLT2 inhibitors in preserved ejection fraction heart failure — Meta-analysis