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Mustang Bio Expanding Phase I/II Trial of Anti-CD20 CAR T-Cell Therapy

NEW YORK – Mustang Bio said on Tuesday that it will launch a multi-center Phase I/II trial of its CAR T-cell therapy after seeing encouraging efficacy and safety in a single-center trial at the Fred Hutchinson Cancer Center.

Mustang is developing MB-106, a CD20-targeted, autologous CAR T-cell therapy, for people with relapsed or refractory B-cell non-Hodgkin lymphomas (B-NHL), chronic lymphocytic leukemia (CLL), and other hematologic cancers. It's a third-generation CAR T-cell therapy in that it is engineered to include two co-stimulatory domains to boost its activity, whereas second-generation CAR T-cell therapies have just one co-stimulatory domain, and first-generation therapies have none. Cells with these additional co-stimulatory domains have shown increased anti-cancer activity in preclinical studies.

MB-106 was developed at Fred Hutchinson by Oliver Press and Brian Till and licensed to Mustang in 2017. That transaction included an agreement for Mustang to provide partial funding for a clinical trial, which commenced in 2018. The US Food and Drug Administration accepted the company's investigational new drug application for MB-106 in May 2021, and in November 2021, Mustang Bio received a $2 million grant from the National Cancer Institute, which it earmarked in part to fund a Phase I/II trial of the treatment.

Data from that trial, conducted at Fred Hutchinson and presented this month at a meeting sponsored by the American Society of Transplantation and Cellular Therapy and the Center for International Blood and Marrow Transplant Research, showed that the therapy was safe and effective.

In the study, 25 patients with a range of malignancies including follicular lymphoma, diffuse large B-cell lymphoma, and Waldenström macroglobulinemia, received five different doses of MB-106. The overall response rate on MB-106 after 28 days was 96 percent, and the complete response rate was 72 percent across all dose levels. Among responding patients, there were two who had previously relapsed on a CAR T-cell therapy. Researchers observed expansion of CAR T cells across all dose levels.

"[I]n this single-institution study, we observed a favorable safety profile and a high rate of complete and durable responses, which make MB-106 suitable for outpatient treatment," Mazyar Shadman, a physician at Fred Hutchinson and principal investigator of the study, said in presenting the data at the meeting. "Additionally, the responses from patients treated previously with CD19-directed CAR T-cell therapy show the potential of MB-106 as an immunotherapy option for these patients." The trial at Fred Hutchinson is still open and enrolling patients with CD20-positive B-NHL and CLL, as well as those previously on a CAR T-cell treatment.

In addition to MB-106, Worcester, Massachusetts-based Mustang is developing an IL13Rα2-directed CAR T-cell therapy, MB-101, in brain cancer and a CD123-targeted CAR T-cell therapy, MB-102, for blastic plasmacytoid dendritic cell neoplasm, acute myeloid leukemia, and high-risk myelodysplastic syndrome. It recently announced plans to begin a clinical trial of MB-101 combined with MB-108, a herpes virus-based therapeutic targeting tumor cells, in previously treated brain cancer patients.