ResoTher's Annexin A1 Mimetic RTP-026 Shows 8-Point LVEF Gain in Phase 2a STEMI Trial, Clearing Acquisition Hurdle
核心洞察
ResoTher Pharma (搜索) reported top-line Phase 2a results showing RTP-026 produced an 8 percentage point median LVEF improvement at Day 90 in both dose groups versus 2.5 points for placebo.
The randomized, double-blind, placebo-controlled study enrolled 66 severe STEMI (搜索) patients who received three intravenous infusions of 25 or 75 µg/kg RTP-026 within 24 hours after PCI.
RTP-026 was safe and well tolerated, with no deaths, no withdrawals due to adverse events, and serious adverse events in three active-treatment patients attributed to underlying disease.
ResoTher Pharma (搜索) A/S has reported top-line Phase 2a results for RTP-026 in patients with ST-elevation myocardial infarction (STEMI (搜索)), showing an 8 percentage point improvement in median left ventricular ejection fraction (LVEF) at Day 90 in both active dose groups compared with 2.5 percentage points for placebo — a 3.2-fold greater improvement in cardiac function. The readout, announced on Sept. 14, 2026, by Hunter Capital RTO 1 (搜索) AB (publ), fulfilled a key condition precedent under the letter of intent governing the companies' proposed reverse acquisition.
The randomized, double-blind, placebo-controlled Phase 2a study enrolled 66 patients with severe STEMI (搜索) undergoing standard treatment with percutaneous coronary intervention (PCI). Patients were randomized to RTP-026 at doses of 25 µg/kg or 75 µg/kg, or placebo, with treatment administered as three intravenous infusions within 24 hours following PCI. The study was designed primarily to evaluate the safety and tolerability of ascending doses and to explore potential efficacy signals.
Consistent Signals Across Cardiac Function and Injury
Median LVEF improved from 46% to 54% in the 25 µg/kg group and from 39% to 47% in the 75 µg/kg group, versus 43.5% to 46% in the placebo group. The results were observed despite patients in the active treatment groups presenting with greater disease severity at baseline than those receiving placebo: anterior or septal infarctions were present in 50% of patients in each RTP-026 group compared with 31.3% in the placebo group, and patients in the 75 µg/kg group had considerably higher baseline levels of cardiac troponin T (cTnT) and CK-MB.
Signals extended to biomarkers of myocardial injury and final infarct size. At 24 hours following PCI, median cTnT levels had increased by approximately 129% in the 25 µg/kg group and 65% in the 75 µg/kg group, compared with approximately 615% in the placebo group. Median infarct size at Day 90 was numerically smaller in both treatment groups — 6.6 grams at 25 µg/kg and 8.7 grams at 75 µg/kg — versus 9.3 grams with placebo.
Safety Profile Supports Continued Development
RTP-026 was safe and well tolerated in this high-risk STEMI (搜索) population at doses of up to three infusions of 75 µg/kg. No new safety signal was identified, no patients withdrew due to adverse events, and no fatal cases or rehospitalisations due to major adverse cardiovascular events were reported. Serious treatment-emergent adverse events were reported in three patients receiving active treatment; all were assessed by treating clinicians as related to the underlying disease rather than to RTP-026. One serious treatment-emergent adverse event occurred in the placebo group and was considered possibly treatment related.
The company cautioned that the Phase 2a study was primarily designed to establish safety and tolerability and explore preliminary efficacy signals, and was therefore not statistically powered to demonstrate efficacy. ResoTher CEO Anders Kronborg told European Biotechnology that the headline LVEF comparison is descriptive and that "no baseline-adjusted between-group analysis has been performed." LVEF by cardiac magnetic resonance (CMR) was used as a secondary evaluation and reported descriptively by group at the two measurement time points, within five days and at 90 days, Kronborg said. Without an adjusted comparison, the baseline imbalance leaves open how much of the LVEF gap the drug accounts for.
Phase 2b Planning Underway
Based on the findings, ResoTher has commenced preparations for an international Phase 2b proof-of-concept study intended to further evaluate the treatment effect of RTP-026 in a larger patient population of about 200 patients, with initiation planned toward the end of 2026. Kronborg said the protocol is not final and it is too early to name a primary endpoint.
RTP-026 is an investigational, first-in-class Annexin A1 (搜索) mimetic designed to engage biological pathways involved in the natural resolution of inflammation. A synthetic peptide based on research from the William Harvey Research Institute at Queen Mary University of London, it mimics part of annexin A1 and acts on the immune-cell receptor FPR2 (搜索), aiming to limit inflammatory damage to heart tissue following reopening of the artery without broadly suppressing the immune system. According to European Biotechnology, RTP-026 is the first drug based on annexin A1 to be tested in heart attack patients, a field in which three decades of trials to limit infarct size have been "disappointingly neutral," per an August review.
Transaction Milestone and Remaining Condition
The Phase 2a readout constituted a key condition precedent under the LOI between Hunter Capital RTO 1 (搜索) and ResoTher for proceeding with the proposed reverse acquisition, whereby ResoTher is intended to become the operating business of Hunter Capital RTO 1. The non-binding LOI was signed in March for an all-share deal that would value the combined company at SEK 365 million to SEK 405 million (€33 million to €36 million).
"Today's results represent a major milestone in the proposed transaction with ResoTher," said Jacob Eriksson, CEO of Hunter Capital RTO 1 (搜索). "Beyond the transaction itself, we are highly encouraged by the clinical findings, which were better than we had expected."
The remaining condition precedent is that ResoTher shall have raised, or otherwise have access to, at least SEK 65 million (€5.8 million) in additional financing, which together with approximately SEK 15 million (€1.3 million) previously raised would bring total financing to approximately SEK 80 million. Completion of the proposed reverse acquisition remains subject to fulfilment of this condition, completion of the transaction process and execution of definitive transaction documentation.
Competitive Landscape in Cardioprotection
The Phase 2b programme will enter a field marked by prior setbacks. Faraday Pharmaceuticals (搜索)' FDY-5301, a sodium iodide injection given before the artery is reopened, posted a median infarct size at its top dose of 8.5% of the left ventricle against 14.9% on placebo in a 120-patient Phase 2, then showed no clear benefit on heart failure or cardiovascular death in a 2,317-patient Phase 3 that ended in September 2025; the Seattle company plans no further studies. Novo Nordisk is testing its IL-6 antibody ziltivekimab, first given within 36 hours of a STEMI (搜索) admission, in the 10,000-patient ARTEMIS trial, which carries a December completion date on the registry. A closer size benchmark comes from a 199-patient Norwegian trial of the IL-6 receptor blocker tocilizumab, which reported an adjusted between-group gain of 5.6 percentage points in the share of threatened heart muscle salvaged, measured by MRI at three to seven days.