X-Linked SCID Gene Transfer Therapy Placed on Clinical Hold

The latest hold on MB-207 follows a similar hold on another XSCID therapy, MB-107.

The FDA has placed a clinical hold on the investigational new drug application (IND) for MB-207, Mustang Bio’s gene transfer program for X-linked severe combined immunodeficiency (XSCID).1

Mustang Bio submitted an IND for a phase 2 study to evaluate the lentiviral gene transfer therapy in December 2021 in patients with XSCID previously treated with hematopoietic stem cell transplantation (HSCT) for whom re-treatment is indicated. The clinical hold is pending Chemistry, Manufacturing and Controls (CMC) clearance.

“We appreciate the FDA’s support and guidance as we pursue the advancement of MB-107 and MB-207 as potential treatment options for XSCID, a life-threatening, rare genetic disorder with limited treatment options available. We hope to efficiently expedite the development of both critically needed treatments for newly diagnosed infants with XSCID who are between two months to two years of age and for children with XSCID who have previously received HSCT and require re-treatment,” Manuel Litchman, MD, president and chief executive officer, Mustang,said in a statement.1 “We look forward to initiating our multi-center pivotal Phase 2 clinical trial of MB-107 under a Mustang-sponsored IND in newly diagnosed infants with XSCID who are between two months to two years of age in the third quarter of 2022.”

MB-207 has been studied at the National Institute of Allergy and Infectious Diseases (NIAID) since 2012 and is currently being assessed in a NIAID-supported phase 1/2 trial (NCT01306019) in patients with XSCID over the age of 2 years previously treated with HSCT with declining immune function and symptomatic infections. The therapy has been granted orphan drug and rare pediatric disease designations by the FDA.

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Mustang Bio is also developing MB-107, another lentiviral gene transfer therapy for the potential treatment of XSCID in newly diagnosed patients under the age of 2 years. MB-107 is being evaluated in a phase 1/2 trial (NCT01512888) at St. Jude, UCSF Benioff Children’s Hospital in San Francisco, and Seattle Children’s Hospital. The company plans to initiate a phase 2 trial in the third quarter of 2022 with an expected enrollment of 10 patients.

MB-107 has been granted rare pediatric, orphan drug, and regenerative medicine advanced therapy designations by the FDA as well as advanced therapy medicinal product classification, orphan drug, and PRIME designation by the EMA. The therapy was previously placed on hold by the FDA in 2020 also pending CMC clearance, and this hold was lifted in January 2021.2

“In light of our positive experience managing the prior MB-107 CMC hold, and our ability to secure FDA clearance to proceed with that program, we believe that our CMC team is well positioned to address the Agency’s concerns around MB-207 once additional clarification of the hold becomes available. Furthermore, we remain fully committed to the success of the pivotal Phase 2 MB-207 clinical trial for children with XSCID who have previously received HSCT and require re-treatment,” Litchman added to the statement.1

1. Mustang Bio provides an update on its IND application for MB-207, a lentiviral gene therapy for treatment of X-linked severe combined immunodeficiency (“XSCID”) in previously transplanted patients. News release. Mustang Bio. January 24, 2021. https://finance.yahoo.com/news/mustang-bio-provides-ind-application-220000491.html
2. Mustang Bio provides updates on its lentiviral gene therapies for the treatment of X-linked severe combined immunodeficiency (“XSCID”). News release. Mustang Bio. February 2, 2021. https://www.globenewswire.com/news-release/2021/02/02/2168050/0/en/Mustang-Bio-Provides-Updates-on-its-Lentiviral-Gene-Therapies-for-the-Treatment-of-X-linked-Severe-Combined-Immunodeficiency-XSCID.html
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