ARTHEx raises $87 million in upsized series B to advance RNA therapy

Spanish biotech ARTHEx has closed an expanded series B financing round totaling $87 million, led by French state-backed investor Bpifrance. The proceeds will fund clinical development of ATX-01, the company’s experimental RNA therapy for myotonic dystrophy type 1 (DM1).

Bpifrance joined through its Large Venture and InnoBio arms, alongside existing backers including AdBio Partners, CDTI Innovación, Columbus Venture Partners, European Innovation Council, Hadean Ventures, Invivo Partners and Sound Bioventures. The extension provides fresh backing as ARTHEx advances toward a registrational program.

ATX-01 is designed to inhibit microRNA23b, which suppresses production of MBNL proteins needed for muscle health. Preclinical studies suggest the treatment restores protein balance and corrects splicing defects, potentially tackling the root cause of DM1 rather than its symptoms. Early patient data are expected in 2026.