ResoTher heart data clear acquisition hurdle, set up 200-patient trial

Why it matters: RTP-026 is the first drug based on annexin A1, one of the body’s own brakes on inflammation, to be tested in heart attack patients. Three decades of trials to limit infarct size have been “disappointingly neutral,” an August review concluded.

By the numbers: Patients with severe ST-elevation myocardial infarction (STEMI) received 25 µg/kg or 75 µg/kg of RTP-026, or placebo, as three infusions within 24 hours of the procedure that reopened their blocked artery, according to the announcement.

• Median left ventricular ejection fraction (LVEF), a measure of the heart’s pumping function, rose from 46% to 54% on the lower dose and from 39% to 47% on the higher dose, versus 43.5% to 46% on placebo.
• Median infarct size at Day 90 was 6.6 grams on the lower dose and 8.7 grams on the higher dose, versus 9.3 grams on placebo.
• No patients died or dropped out over side effects. Doctors attributed serious adverse events in three patients on RTP-026 to their underlying disease.

Yes, but: The trial was designed mainly for safety and not powered to show efficacy, and its headline comparison, 8 percentage points of LVEF gain on both doses against 2.5 on placebo, is descriptive. “No baseline-adjusted between-group analysis has been performed,” ResoTher CEO Anders Kronborg told European Biotechnology.

• “LVEF by CMR was used as a secondary evaluation,” Kronborg added. “The LVEF measured by CMR was reported descriptively by group at the two measurement time points, within five days and at 90 days.”
• Without an adjusted comparison, the imbalance also leaves open how much of the LVEF gap the drug accounts for. ResoTher plans an international Phase 2b of about 200 patients toward the end of 2026, but the protocol is not final and it is too early to name a primary endpoint, Kronborg said.

The big picture: One precedent failed last year. Faraday Pharmaceuticals’ 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 admission, in the 10,000-patient ARTEMIS trial, which carries a December completion date on the registry.
• A closer benchmark in size for a 200-patient Phase 2b comes from Norway: a 199-patient trial of the IL-6 receptor blocker tocilizumab 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.

How it works: RTP-026, a synthetic peptide based on Queen Mary University of London research, mimics part of annexin A1 and acts on the immune-cell receptor FPR2. ResoTher is developing it to limit the inflammatory damage to heart tissue that follows reopening of the artery.

Follow the money: Hunter Capital RTO 1 signed a non-binding letter of intent in March for the all-share deal, which would value the combined company at SEK 365 million to SEK 405 million (€33 million to €36 million).

• The deal still requires ResoTher to raise or otherwise secure at least SEK 65 million (€5.8 million), on top of about SEK 15 million (€1.3 million) already raised, Hunter Capital RTO 1 said on Sept. 14. In March, it had aimed to close by Sept. 30.

Bottom line: The 200-patient trial, and the endpoint ResoTher picks for it, will show whether RTP-026’s signal survives an adjusted comparison. In the meantime, the company needs to convince investors with the data it has in hand to make the planned reverse merger happen.