ARO-MAPT

October 14, 2026: Arrowhead Pharmaceuticals (NASDAQ: ARWR) reported interim Phase 1/2a results for ARO-MAPT in healthy volunteers, an investigational RNAi therapy targeting MAPT for Alzheimer’s disease and other tauopathies. In the ongoing AROMAPT-SC-1001 study, subcutaneous ARO-MAPT produced durable reductions in cerebrospinal fluid total tau, which the company said clinically validates blood-brain barrier delivery of siRNA via its TRiM platform.

At Day 105, mean CSF total tau reductions were 40% and 69% for 2.1 mg/kg and 6.4 mg/kg dosed on Days 1, 8, and 15, respectively. A 12.8 mg/kg regimen given on Days 1 and 15 achieved a mean 73% reduction at Day 105, with a maximum individual reduction of 85%. Because Day 105 is 90 days after the final dose, the data support potential once-quarterly or less frequent dosing.

ARO-MAPT was generally well tolerated; most treatment-emergent adverse events were Grade 1/mild, with no serious TEAEs, deaths, or discontinuations. Common TEAEs included injection-site reactions, bruising at vessel puncture site, upper respiratory tract infection, back pain, and headache.

Next steps: complete dosing in healthy-volunteer multiple-ascending-dose cohorts, continue enrollment in early Alzheimer’s disease cohorts, and provide data updates in 2027. Regulatory discussions have begun for planned studies in MAPT-associated frontotemporal dementia and Progressive Supranuclear Palsy.