Mustang Bio Ignites Bullish Retail Buzz As FDA Grants Orphan Status To Brain Cancer Drug

Mustang Bio generated increased retail chatter on Monday after the company said that the FDA had awarded Orphan Drug Designation to its experimental CAR-T drug MB-101 for the treatment of astrocytomas and glioblastoma (GBM), two types of fast-growing brain tumors.

The treatment, which targets the IL13Ra2 protein, is currently being studied in a Phase 1 trial. 

In early results published in Nature Medicine, MB-101 was well-tolerated, with 50% of patients seeing stable disease or better. 

Among them, two had partial responses, and two others achieved complete responses lasting 7.5 months and more than five and a half years.

Mustang is also looking at a combo approach, pairing MB-101 with MB-108, an HSV-1-based oncolytic virus, in a regimen it calls MB-109. 

Preclinical studies suggest that MB-108 may help modify the tumor microenvironment, essentially turning "cold" tumors into "hot" ones to improve efficiency of MB-101 CAR-T cells.

MB-108 already has Orphan Drug status for malignant glioma, and Mustang says the combination could allow MB-101 to move more effectively through the tumor, activate in the right spots, and target cancer cells more precisely.

Both MB-101 and MB-108 are still enrolling patients in Phase 1 studies, including one at City of Hope, the other at The University of Alabama at Birmingham. 

However, moving the MB-109 program forward will depend on whether the company can secure more funding or land a partnership deal.

Orphan Drug status gives MB-101 access to several FDA benefits, including seven years of market exclusivity if approved, tax breaks on clinical trial costs, and waived fees, which are all part of a program designed to support treatments for rare conditions affecting fewer than 200,000 people in the U.S.

On Stocktwits, retail sentiment for Mustang Bio was ‘extremely bullish’ amid a 105,200% surge in 24-hour message volume.

One user on Stocktwits suggested that shares of $MBIO could climb to the $15–$20 range if the company secures a partnership, noting the stock “has life” and is poised to grow, especially for those who bought in below $1.20.

Another user speculated that a partnership or buyout by a larger pharmaceutical company could be in play, calling the day’s FDA designation “great news” for Mustang Bio.

The stock has declined 68% so far in 2025.

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