Safety, pharmacokinetics, and exploratory efficacy of the oral ghrelin receptor agonist AC01 in heart failure with reduced ejection fraction (GOAL-HF1): a randomised, double-blind, placebo-controlled, phase 1b/2a study
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In the Phase 1b/2a GOAL-HF1 trial, the novel oral ghrelin receptor agonist AC01 was safe, well-tolerated, and demonstrated promising early signals of improved cardiac output and structure in patients with chronic HFrEF.
Key Findings
Study Design
Study Limitations
Clinical Significance
AC01 represents a potential paradigm shift in heart failure management. Historically, positive inotropic agents have been restricted to acute, short-term, or palliative use due to severe risks including arrhythmias, increased myocardial oxygen consumption, and excess mortality. AC01, functioning via a unique ghrelin receptor agonist mechanism, offers the first promising clinical evidence of a safe, orally administered agent that improves cardiac contractility without the historic perils of traditional inotropes. This establishes a strong foundation for Phase 2b and Phase 3 trials to evaluate chronic, at-home oral inotropic therapy in HFrEF.
Historical Context
The modern standard of care for HFrEF is centered around neurohormonal blockade and metabolic modulation (e.g., ARNIs, beta-blockers, MRAs, and SGLT2 inhibitors), which improve survival but do not directly target the fundamental mechanical deficit of a weakened myocardium. Previous attempts to develop oral inotropes (such as PDE3 inhibitors and oral beta-agonists) consistently failed because their mechanism of increasing intracellular cAMP and calcium led to fatal arrhythmias and accelerated mortality. Developed from research at Karolinska Institutet, AC01 explores an entirely alternative contractile pathway (ghrelin receptor agonism) to uncouple the enhancement of myocardial contractility from pro-arrhythmic and ischemic risks.
Guided Discussion
High-yield insights from every perspective
How does a ghrelin receptor agonist like AC01 theoretically improve cardiac output and structure in patients with heart failure with reduced ejection fraction (HFrEF)?
Key Response
Ghrelin, often known as the 'hunger hormone', acts on the growth hormone secretagogue receptor (GHSR). In the setting of HFrEF, activating this pathway stimulates the release of growth hormone and insulin-like growth factor 1 (IGF-1), which promotes myocardial contractility, reduces cellular apoptosis, and lowers peripheral vascular resistance via endothelial nitric oxide release. Additionally, it helps counteract cardiac cachexia by stimulating appetite and anabolic pathways, improving overall metabolic efficiency.
Given the highly effective four-pillar guideline-directed medical therapy (GDMT) currently standard for HFrEF, what specific patient phenotype or clinical gap might an oral ghrelin receptor agonist like AC01 fill if it progresses to FDA approval?
Key Response
While current GDMT (ARNI/ACEi, beta-blockers, MRAs, SGLT2 inhibitors) significantly improves morbidity and mortality, many patients still progress to advanced heart failure characterized by frailty, severe fatigue, and cardiac cachexia. AC01 might be uniquely beneficial for patients experiencing these anabolic deficits, sarcopenia, or refractory low cardiac output despite optimal GDMT, as it targets a distinct metabolic and neurohormonal axis not addressed by the current four pillars.
How might the neurohormonal and metabolic changes induced by a ghrelin receptor agonist interact with the physiological blockade provided by current HFrEF GDMT, particularly concerning sympathetic tone and volume regulation?
Key Response
Ghrelin generally exhibits sympathoinhibitory effects, which could synergize favorably with beta-blockers to reduce myocardial oxygen demand. However, growth hormone secretagogues can sometimes cause mild sodium and fluid retention. Fellows must consider how AC01's vasodilatory effects might risk hypotension when combined with ARNIs, or conversely, whether the diuretic and natriuretic properties of SGLT2 inhibitors and MRAs might perfectly counterbalance any theoretical GH-mediated fluid retention, creating a complementary pharmacological profile.
If Phase 3 trials confirm the structural and functional efficacy of AC01, how will this class of medication shift our clinical paradigm regarding the definition of 'success' in chronic HFrEF management?
Key Response
Historically, HFrEF management has focused heavily on mortality reduction and preventing hospital readmissions. A drug that actively promotes anabolic recovery and reverse remodeling challenges attendings to look beyond survival curves and focus on restoring vitality. Incorporating functional endpoints like frailty indices, lean body mass recovery, and precise echocardiographic reverse remodeling metrics into routine assessment will become paramount, shifting the focus from simply slowing decline to actively rebuilding functional capacity.
Scholarly Review
Critical appraisal through the lens of expert reviewers and guideline development
In a Phase 1b/2a trial assessing a metabolic and structural intervention like AC01, what are the primary methodological challenges in validating exploratory efficacy endpoints such as cardiac output and remodeling, and how should subsequent trials be designed to mitigate these?
Key Response
Assessing cardiac structure and output in early-phase trials relies on surrogate imaging markers (e.g., echocardiography, cardiac MRI) which carry high inter-operator variability and require rigorous core lab adjudication. Furthermore, the short duration of a Phase 1b/2a trial may not adequately capture long-term reverse remodeling. Future trial designs must mitigate this by employing sensitive, early-change biomarkers alongside standardized multiparametric MRI protocols, ensuring adequate statistical power to separate true structural drug effects from spontaneous fluctuations or background therapy optimization.
When evaluating the exploratory efficacy signals of AC01 from the GOAL-HF1 trial, what specific confounders related to background heart failure therapy and baseline metabolic status would you scrutinize before endorsing these results for broad publication?
Key Response
A rigorous peer review must determine if improvements in cardiac output and structure were genuinely due to AC01 or confounded by the recent uptitration of concurrent GDMT, such as SGLT2 inhibitors or ARNIs. Furthermore, baseline differences in BMI, nutritional status, and the severity of baseline cachexia could significantly skew the perceived efficacy of a ghrelin agonist. Evaluating whether randomization adequately balanced these variables and confirming the stability of background therapies during the trial is critical to establishing internal validity.
Assuming large-scale Phase 3 trials demonstrate a significant morbidity benefit for AC01, what evidentiary thresholds must be met for the ACC/AHA/HFSA to recommend an entirely new pharmacological class alongside the established 'four pillars' of HFrEF therapy?
Key Response
Current ACC/AHA/HFSA guidelines require robust, reproducible Phase 3 data (Level of Evidence A) demonstrating significant improvements in hard clinical endpoints (cardiovascular death, heart failure hospitalizations) on top of maximally tolerated GDMT. The committee would evaluate AC01's number needed to treat (NNT), its safety profile (especially regarding fluid retention or theoretical oncologic risks from prolonged GH stimulation), and cost-effectiveness. If AC01 primarily benefits a distinct subgroup (e.g., patients with documented cardiac cachexia), it might receive a targeted Class IIa recommendation for that specific phenotype rather than a universal Class I recommendation.
Clinical Landscape
Noteworthy Related Trials
PARADIGM-HF
Tested
Sacubitril/valsartan 200 mg twice daily
Population
Patients with HFrEF
Comparator
Enalapril 10 mg twice daily
Endpoint
Composite of cardiovascular death or heart failure hospitalization
DAPA-HF
Tested
Dapagliflozin 10 mg daily
Population
Patients with HFrEF with or without type 2 diabetes
Comparator
Placebo
Endpoint
Composite of worsening heart failure or cardiovascular death
GALACTIC-HF
Tested
Omecamtiv mecarbil
Population
Patients with symptomatic HFrEF
Comparator
Placebo
Endpoint
Composite of heart failure event or cardiovascular death
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