Mustang bucks some partnered cell and gene therapy work

Mustang Bio is galloping away from a few City of Hope-partnered cell therapy programs and pausing a gene therapy trial to funnel resources toward a lead asset developed in collaboration with Fred Hutch. 

A pipeline reprioritization has led the company to ax work on a CD123-targeted CAR T as well as three other cell therapies targeting HER2, CS1 and PCSA, respectively, according to a release Thursday. Mustang will continue work on an IL13Rα2-targeting cell therapy combined with an oncolytic virus—MB-108—that’s been developed alongside City of Hope and Nationwide Children’s Hospital. 

And that’s not all; Mustang is halting “bubble boy disease” gene therapy after a review of data from an ongoing investigator-sponsored trial spurred a pause in enrollment. The company says no safety concerns have been raised and “no insertional mutagenesis or malignancy has been detected” in either investigator-sponsored trial. 

Mustang is awaiting more data from its partner on a new lentiviral vector before launching more of its own trials, which have been delayed out of “an abundance of caution.” 

“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,” said CEO Manuel Litchman, M.D., in a release.

The decision to temporarily shelve work on the two gene therapies stymies Mustang's clinical giddy-up, some four years after the company claimed to have reversed "bubble boy" disease in eight patients. Mustang did not elaborate on why the available data led to the decision to pause. The company says that more details will be provided once additional information on the new vector is reviewed.

The pipeline reprioritization comes as Mustang sells off its Worcester, Massachusetts-based manufacturing facility to uBriGene for up to $11 million. The biotech will receive $6 million upfront and an additional $5 million after raising $10 million in new financing. Closing of the deal is contingent in part on uBriGene taking on a few of Mustang’s employees. 

Once that deal wraps up, the two companies will enter a supply agreement whereby uBriGene will supply Mustang’s lead programs. Mustang says that uBriGene intends to grow the facility “to manufacture a broader portfolio of advanced modalities.” The facility opened in 2018. 

Mustang did not explicitly mention needing to cut staff as part of the portfolio update and manufacturing deal but expects to incur $2.1 million in severance charges. 

"We have not disclosed any details relating to our employees at the facility, but the aligned goal for the partnership is to continue to grow the advanced therapy manufacturing ecosystem in the Greater Boston area,” said Litchman in a statement. 

Editor's note: This story was updated with a statement from CEO Manuel Litchman.