Core Insights - Mustang Bio's shares surged 180.7% following the FDA's Orphan Drug designation for its investigational candidate MB-101, aimed at treating rare brain cancers such as recurrent diffuse and anaplastic astrocytoma and glioblastoma [1][4] Group 1: FDA Orphan Drug Designation - The FDA's Orphan Drug designation is granted to drugs for rare diseases affecting fewer than 200,000 people in the U.S., encouraging innovation in unmet medical needs [2] - MB-101, an IL13Rα2-targeted CAR-T cell immunotherapy, is currently in a phase I study for recurrent/refractory GBM patients [1][4] Group 2: Market and Financial Implications - Drugs with Orphan status receive various incentives, including tax credits for clinical study costs, waivers of prescription drug user fees, and seven years of market exclusivity for the designated condition [3] - Year-to-date, Mustang Bio's shares have declined 62.3%, contrasting with a 1.9% decline in the industry [3] Group 3: Clinical Development and Future Plans - MB-101 has shown durable responses in its phase I GBM study, with 50% of patients achieving stable disease or better, including two complete responses lasting 7.5 and over 66 months [7] - Mustang Bio plans to initiate a phase I study of a combination therapy, MB-109, in 2026, pending financing or partnership [8][9] - The company also has another candidate, MB-108, which received Orphan Drug status last year and is being evaluated in a separate phase I study for GBM [6]