Arrowhead Pharmaceuticals dosed the first subjects on December 8, 2025 in its Phase 1/2a trial of ARO‑MAPT, an RNA interference therapeutic that targets the MAPT gene responsible for tau protein production in Alzheimer’s disease and related tauopathies.
The study, designated AROMAPT‑SC‑1001, is a placebo‑controlled, dose‑escalating trial that will enroll up to 64 healthy volunteers and 48 patients with early Alzheimer’s disease. Participants receive a single‑dose phase followed by a multiple‑dose phase, with weekly subcutaneous injections for three weeks and then monthly injections for three months, for a total of six administrations.
Primary objectives include evaluating safety, tolerability, pharmacokinetics, and pharmacodynamics, with target engagement measured by reductions in MAPT mRNA and tau protein in blood and cerebrospinal fluid. Cognitive and functional outcomes will also be monitored in the patient cohort.
Preclinical non‑human primate studies presented at the RNA Leaders USA Congress 2025 demonstrated deep knockdown of MAPT across central nervous system regions after subcutaneous injection, supporting a quarterly dosing schedule. Arrowhead’s proprietary TRiM™ platform enables blood‑brain‑barrier penetration, a key differentiator for CNS RNAi therapies.
Strategically, this milestone marks Arrowhead’s first foray into central nervous system indications, expanding its pipeline beyond cardiometabolic and rare disease programs. The company has set a goal of 20 clinical‑stage or marketed products by 2025 and recently launched REDEMPLO for severe hypertriglyceridemia. Initial data from the ARO‑MAPT trial are expected in the second half of 2026, potentially opening a new therapeutic avenue for Alzheimer’s and related tauopathies.
Dr. James Hamilton, Chief Medical Officer, emphasized the unmet need for disease‑modifying treatments targeting tau, noting that ARO‑MAPT could slow or halt cognitive decline by reducing tau pathology.
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