Tysabri: how long were the pivotal tox studies?

“Chronic toxicity studies of repeated doses of natalizumab over a 26-week period, followed by a 17 week dose-free period in cynomolgus monkeys”

“A six-month toxicity study with natalizumab as weekly intravenous infusion in juvenile cynomologus monkeys with a 17-week recovery period”

“In several repeated dose toxicity studies in cynomolgus monkeys the dosing of 3, 10, or 30 mg/kg of natalizumab was performed on alternate days through day 28 by IV injection.”