Note 3 - Clinical Trial and Sponsored Research Agreements

Research and Development Expenses - Sponsored Research and Clinical Trial Agreements

For the three and nine months ended September 30, 2023 and 2022, the Company recorded the following expense in research and development for sponsored research and clinical trial agreements in the Unaudited Statements of Operations pursuant to the terms of this agreement:

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CD123 (MB-102) Clinical Research Support Agreement

Beginning in February 2017, the Company was party to a clinical research support agreement for the CD123-directed CAR T program (the “CD123 CRA”) with City of Hope National Medical Center (“COH” or “City of Hope”) whereby, the Company has agreed to contribute approximately $0.1 million per patient in connection with the ongoing investigator-initiated study. In May 2023, the Company determined to discontinue development of its MB-102 program and terminated the associated CRA and license.

IL13Rα2 (MB-101) Clinical Research Support Agreements

Since February 2017, the Company has been party to a clinical research support agreement for the IL13Rα2-directed CAR T program (the “IL13Rα2 CRA”) with COH, whereby, the Company has agreed to contribute $0.1 million related to patient costs in connection with the on-going investigator-initiated study.

Since October 2020, the Company has been party to a clinical research support agreement for the IL13Rα2-directed CAR T program for adult patients with leptomeningeal glioblastoma, ependymoma or medulloblastoma (the “IL13Rα2 Leptomeningeal CRA”) with COH whereby, the Company has agreed to contribute $0.1 million per patient in connection with the ongoing investigator-initiated study. Further, the Company agreed to fund approximately $0.2 million annually pertaining to the clinical development of the IL13Rα2-directed CAR T program for this patient population.

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Since October 2020, the Company has been party to a Sponsored Research Agreement (“SRA”) with COH to conduct combination studies of a potential IL13Rα2 CAR (MB-101) and herpes simplex-1 oncolytic virus therapy (MB-108). Pursuant to the SRA, the Company funded research in the amount of $0.3 million for the program. In November 2022, the SRA was amended to include additional funding of $0.6 million.

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Since March 2021, the Company has been party to a clinical research support agreement for an Institutional Review Board-approved, investigator-initiated protocol entitled: “Single Patient Treatment with Intraventricular Infusions of IL13Rα2-targeting and HER2-targeting Chimeric Antigen Receptor (CAR)-T cells for a Single Patient (UPN 181) with Recurrent Multifocal Malignant Glioma.” Pursuant to the terms of this agreement, the Company will contribute up to $0.2 million in connection with the ongoing investigator-initiated study.

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CS1 (MB-104) Clinical Research Support Agreement

Beginning in June 2020, the Company was party to a clinical research and support agreement with COH in connection with an investigator-sponsored study conducted under an Institutional Review Board-approved for MB-104, whereby the Company has agreed to reimburse COH for costs associated with this trial, when incurred, not to exceed $2.4 million. The agreement will expire upon the delivery of a final study report or earlier. Since inception, the Company has reimbursed COH $2.2 million. In May 2023, the Company determined to discontinue development of its MB-104 program and terminated the associated CRA and license.

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HER2 (MB-103) Clinical Research Support Agreement

Beginning in September 2020, the Company was party to a clinical research support agreement with COH in connection with an investigator-sponsored study conducted under an Institutional Review Board-approved, investigator-initiated protocol entitled: “Phase I Study of Cellular Immunotherapy using Memory-Enriched T Cells Lentivirally Transduced to Express a HER2-Specific, Hinge-Optimized, 41BB-Costimulatory Chimeric Receptor and a Truncated CD19 for Patients with Recurrent/Refractory Malignant Glioma” for MB-103. Under the terms of the agreement the Company will reimburse COH for costs associated with this trial not to exceed $3.0 million. The agreement will expire upon the delivery of a final study report or earlier. Since inception, the Company has reimbursed COH $3.0 million. In May 2023, the Company determined to discontinue development of its MB-103 program and terminated the associated CRA and license.

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PSCA (MB-105) Clinical Research Support Agreement

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Beginning in October 2020, the Company was party to a clinical research support agreement with COH in connection with an investigator-sponsored study conducted under an Institutional Review Board-approved, investigator-initiated protocol entitled: “A Phase 1 Study to Evaluate PSCA-Specific Chimeric Antigen Receptor (CAR)-T Cells for Patients with Metastatic Castration Resistant Prostate Cancer” for MB-105. The Company has agreed to reimburse COH for costs associated with this trial not to exceed $2.3 million. The agreement will expire upon the delivery of a final study report or earlier. Since inception, the Company has reimbursed COH $0.5 million. In May 2023, the Company determined to discontinue development of its MB-105 program and terminated the associated CRA and license.

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CD20 (MB-106) Clinical Trial Agreement with Fred Hutchinson Cancer Research Center

Since July 3, 2017, in conjunction with the CD20 Technology License from Fred Hutchinson Cancer Center (“Fred Hutch”), the Company has been party to an investigator-initiated clinical trial agreement (the “CD20 CTA”) to provide partial funding for a Phase 1/2 clinical trial at Fred Hutch evaluating the safety and efficacy of the CD20 Technology in patients with relapsed or refractory B-cell non-Hodgkin lymphomas. In connection with the CD20 CTA, the Company agreed to fund up to $5.3 million of costs associated with the clinical trial, which commenced during the fourth quarter of 2017. In November 2020, the CD20 CTA was amended to include additional funding of approximately $1.8 million, which includes $0.8 million for the treatment of five patients with chronic lymphocytic leukemia. In January 2022, the CD20 CTA was amended to include additional funding of $2.2 million increasing the total payment obligation of the Company in connection with the CD20 CTA not to exceed $9.3 million. Since inception, the Company has reimbursed Fred Hutch $8.4 million.

XSCID (MB-107) Data Transfer Agreement with St. Jude Children’s Research Hospital

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Since June 2020, the Company has been party to a Data Transfer Agreement with St. Jude Children’s Research Hospital (“St. Jude”) under which Mustang will reimburse St. Jude for costs associated with St. Jude’s clinical trial for the treatment of infants with X-linked severe combined immunodeficiency (“XSCID”), whereby the Company will continue to reimburse St. Jude for costs incurred in connection with this trial. Since inception, the Company has reimbursed St. Jude $3.5 million.

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RAG1-SCID (MB-110) Sponsored Research Support Agreement (“SRA”) with Leiden University Medical Centre

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Since September 8, 2021, in connection with the Leiden License, the Company has been party to a Sponsored Research Support Agreement (“SRA”) with Leiden University Medical Centre (“LUMC”) under which the Company will fund

research in the amount of approximately $0.5 million annually over a period of 5 years. The research performed pursuant to this agreement will support technology the Company has licensed from Leiden for the use of a gene therapy under development for the treatment of severe immunodeficiency caused by mutations in the RAG1 gene.

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Sponsored Research Support Agreement with Mayo Clinic  

Since June 2021, the Company has been party to an SRA with the Mayo Clinic under which the Company will fund research in the amount of $2.1 million over a period of two years. In October 2022, the SRA was amended to include additional funding of approximately $0.1 million. The research performed pursuant to this agreement will support technology the Company has licensed from Mayo Clinic for a novel technology that may be able to transform the administration of CAR T therapies and has the potential to be used as an off-the-shelf therapy. Since inception, the Company has funded $2.2 million.