Abcuro Raises $66 Million To Re-Run Ulviprubart In Less Severe IBM, After Prior Study Missed Statistical Significance

Abcuro has raised $66 million in Series D financing to fund another clinical trial of ulviprubart in inclusion body myositis, giving the company a second shot at a rare muscle disease program after disappointing results earlier this year.

The new plan centers on patients with less severe inclusion body myositis, or IBM, a subgroup that Abcuro said showed a 50% slowing of disease progression in a pre-defined analysis. In the overall Phase 2/3 study population, results presented in March during the Global Conference on Myositis were not statistically significant, although the company said the data showed a trend toward slower disease progression relative to placebo and that the drug had a favorable safety and tolerability profile.

The data

Abcuro is developing ulviprubart for IBM, which belongs to a group of muscle diseases called idiopathic inflammatory myopathies. The company argues that IBM develops from pathogenic T cells that express killer cell lectin-like receptor G1, or KLRG1. Ulviprubart is a monoclonal antibody designed to selectively target and deplete those pathogenic T cells while sparing other immune cells.

That mechanism remains central to the company’s case for continuing development after the March setback. The earlier study did not deliver the statistically significant result that would typically strengthen a regulatory filing, but Abcuro’s forward path depends on the subgroup finding in less severe patients rather than on a claim of success across the full trial population.

Abcuro estimates that about 40,000 patients have been diagnosed with IBM in the U.S. It also estimates that patients with less severe disease represent about half of the overall IBM population, which helps explain why the company is concentrating its next study there instead of repeating a broader trial design.

The financing

The Series D was led by New Leaf Venture Partners. Other participants included funds managed by abrdn Inc., Bain Capital Life Sciences, Samsara BioCapital, Redmile Group, Mass General Brigham Ventures, RA Capital Management, Pontifax, Sanofi Ventures, Foresite Capital, NEA, Eurofarma Ventures, Kaitai Capital, Soleus Capital, Nancy Chang, Shang Bay, and Rock Springs Capital.

Abcuro last raised money in early 2025, when it brought in a $200 million Series C round led by New Enterprise Associated. The contrast between the two financings is notable: the latest round is much smaller, but it is being directed at a more defined objective, namely a new trial that the company said could support a regulatory submission in less severe IBM.

That points to the current investment case. Rather than financing a broad platform expansion, backers are funding a narrower, evidence-based retry around the portion of the population where Abcuro believes ulviprubart’s effect was strongest. In biotech financing terms, this looks less like a reset and more like a conviction round tied to a specific regulatory strategy.

The road here

Abcuro received what the source described as disappointing news this year because ulviprubart had been expected to support a regulatory submission in IBM, a disorder with no FDA-approved therapies. The company now says it has been in discussions with the FDA and plans to begin the next study in the fourth quarter of this year.

The strategic signal is that investors were willing to fund another trial even after a miss, but only with a tighter patient-selection thesis. In a disease area with no approved drugs, a favorable safety and tolerability profile plus a pre-defined subgroup effect can be enough to preserve financing access, though it also raises the stakes on whether the next study can prospectively confirm that signal in the less severe population.