Massachusetts-based Abcuro, Inc. has closed a USD 66 million Series D financing to fund a new potentially registrational study of ulviprubart, its anti-killer cell lectin-like receptor G1 (KLRG1) monoclonal antibody, in patients with inclusion body myositis (IBM). The raise comes after the Phase II/III MUSCLE study of ulviprubart missed statistical significance in its overall patient population, but showed a 50% slowing of disease progression in a pre-defined subgroup of patients with less severe disease, defined as an IBM Functional Rating Scale (IBMFRS) score above 29.
The new study will effectively test whether the subgroup signal reflects a genuine stage-dependent treatment effect, with Abcuro hypothesizing that depletion of pathogenic KLRG1-positive T cells may have greater impact earlier in IBM, before accumulated muscle damage becomes irreversible. The strategy remains high-risk, however, because neither dose achieved statistical significance in the ≥29 IBMFRS subgroup in MUSCLE.
New Leaf Venture Partners led the round, with new investor Rock Springs Capital joining alongside a broad roster of existing backers including 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. The Series D follows a USD 200 million Series C led by NEA in early 2025 and a USD 155 million Series B co-led by Redmile Group and Bain Capital Life Sciences in 2023, bringing total capital raised to approximately USD 463 million.
Proceeds will support initiation of the new study, which Abcuro said it expects to begin in Q4 2026 following discussions with the US FDA, with top-line results anticipated in the second half of 2028. The company said positive results would support a biologics license application (BLA) filing.