Mustang Bio Soars 39.1% on FDA Orphan Drug Designation for MB-101

On July 9, 2025, Mustang Bio's stock surged by 39.1% in pre-market trading, marking a significant milestone for the biopharmaceutical company.

Mustang Bio has received Orphan Drug Designation from the FDA for MB-101, a CAR T-cell therapy targeting astrocytomas and glioblastoma. The Phase 1 trial has shown promising results with 50% of patients achieving stable disease or better. The company plans to enhance efficacy by combining MB-101 with MB-108, an HSV-1 oncolytic virus, to transform "cold" tumors into "hot" ones. This designation could provide Mustang Bio with tax credits, a waiver of prescription drug user fees, and seven years of market exclusivity upon approval.

MB-101, an IL13Ra2-targeted CAR T-cell therapy, has shown promising results in a Phase 1 trial published in Nature Medicine. The trial demonstrated that 50% of patients achieved stable disease or better, with two patients achieving complete responses lasting over 66 months. The FDA's Orphan Drug Designation covers a broader indication than initially proposed by Mustang Bio, highlighting the treatment's potential in addressing rare and aggressive forms of brain cancer.

The designation includes several benefits for Mustang Bio, including tax credits for clinical trials and seven years of market exclusivity if the treatment receives regulatory approval. Additionally, Mustang Bio is exploring a combination therapy, MB-109, which combines MB-101 with MB-108, an HSV-1 oncolytic virus. Preclinical data suggest that this combination could enhance the efficacy of MB-101 by transforming "cold" tumors into "hot" ones, thereby improving the treatment's effectiveness.

The company's mission is to develop innovative cell therapies for challenging-to-treat cancers through strategic partnerships and research. The Orphan Drug Designation for MB-101 further validates Mustang Bio's scientific approach and positions it as an innovator in the biopharmaceutical industry. However, the company faces potential challenges, such as the need for additional funding to continue product development and the early stage of its product candidates. The reliance on third-party suppliers also poses risks to maintaining production and meeting clinical trial timelines.

Mustang Bio's partnerships with top medical institutions, including City of Hope and The University of Alabama at Birmingham, continue to enroll patients in Phase 1 clinical trials for both MB-101 and MB-108.