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Mustang Bio Reprioritizes Pipeline, Sells Manufacturing Facility to Focus on Lead Assets

NEW YORK – Mustang Bio on Thursday said it is discontinuing development of several cell and gene therapy programs so it can focus its resources on advancing its lead CD20 CAR T-cell therapy MB-106, the glioblastoma treatment MB-109, and an in vivo CAR T platform.

As part of a companywide restructuring plan, the company also announced that uBriGene Biosciences will acquire its Worcester, Massachusetts, manufacturing facility in a deal worth up to $11 million, but uBriGene will still manufacture its lead pipeline products.

After looking at its portfolio, the Worcester-based cell and gene therapy company has decided to stop developing its autologous CD123-targeted CAR T-cell therapy MB-102 in refractory acute myeloid leukemia and blastic plasmacytoid dendritic cell neoplasm; and its HER2-, CS1- and PSCA-targeted CAR T-cell therapy programs. These products were part of a codevelopment collaboration with City of Hope.

Under that collaboration, Mustang will continue to advance MB-101, which targets IL13Rα2 on malignant glioma cells, with MB-108, an oncolytic virus designed to make tumors more vulnerable to CAR T-cell treatment. The company plans to file an investigational new drug application for the combined product, dubbed MB-109, with the US Food and Drug Administration this year.

Mustang will also keep codeveloping the CAR T-cell therapy MB-106 with Fred Hutchinson Cancer Center as a treatment for relapsed or refractory B-cell non-Hodgkin lymphomas and chronic lymphocytic leukemia. The treatment has shown high response rates in patients with Waldenstrom macroglobulinemia, and Mustang said it expects to dose the first patient in a pivotal Phase II trial in Q1 2024. The company's collaboration with Mayo Clinic to develop an in vivo CAR T platform technology will also continue.

In its gene therapy portfolio, Mustang said it will pause enrolling patients into pivotal trials of MB-107 and MB-207 in X-linked severe combined immunodeficiency (SCID). The firm decided to delay starting its own trials of the gene therapies in newborns and previously transplanted patients until there is more data from investigator-sponsored trials that partners are conducting using a modified version of the current lentiviral vector.

This year, the company plans to treat a second RAG1-SCID patient with its MB-110 LV-RAG1 ex vivo lentiviral gene therapy in an investigator-sponsored Phase I/II trial in Europe. Mustang will also continue to collaborate with Frank Staal from Leiden University on developing other lentiviral gene therapies.

"Upon completion of a thorough, strategic review of our portfolio of CAR T and gene therapies, it was determined that Mustang's resources should be focused and allocated to benefit our lead clinical-stage CAR T programs, which could provide potential curative treatment options for certain hematologic cancers and solid tumors, supported by data-to-date," Mustang President and CEO Manuel Litchman said. "Concentrating our priorities and postponing the initiation of the MB-107 and MB-207 pivotal trials, along with maintaining a reduced headcount, reduces Mustang's burn and extends our cash runway."

Under the asset purchase agreement between Mustang and uBriGene, uBriGene will pay $6 million upfront for Mustang's cell and gene therapy manufacturing facility. Mustang is eligible for another $5 million if it raises $10 million in gross proceeds from equity raises after the transaction closes, which is expected in June.

UBriGene has said it will expand the Worcester site's capabilities and continue leveraging Mustang's experienced staff, but it will also contribute its own expertise in preclinical research, late-stage and commercial manufacturing of advanced therapies, and regulatory inspections. After the asset purchase is complete, the companies will enter into a manufacturing supply agreement, in which uBriGene will manufacture Mustang's products, including supplying MB-106 for an ongoing Phase I/II trial.

Mustang expects to offset around $2.1 million in severance charges related to the facility transaction with at least $24 million in annual operational savings from personnel, facility, clinical operations, and portfolio restructuring efforts. The firm also reduced its annual interest expense by approximately $4.3 million in April after repaying its loan and security agreement with Runway Growth Finance.