Abstract LB145: Lentiviral-based hematopoietic stem cell platform for macrophage-specific expression in glioma immunotherapy

Abstract Currently, the FDA has approved several lentiviral (LV)-based cell therapies using autologous hematopoietic stem cells (HSCs) for the treatment of inherited monogenic diseases. Glioblastoma (GBM) has shown limited responsiveness to current immunotherapies, largely due to a lack of specificity and durability, as well as its profoundly immunosuppressive tumor immune microenvironment (TME) driven by tumor-associated macrophages (TAMs). TAMs constitute up to 50% of the cellular composition in GBM. Approximately 85% of TAMs originate from infiltrating macrophages/monocytes, while the remaining 15% are brain-resident microglia. To overcome this, we have developed a macrophage-restricted gene delivery platform using lentivirally engineered HSCs. To achieve lineage-specific expression, we utilized the human CD68 (hCD68) promoter and demonstrated strong lineage specificity, driving gene expression across both human and murine macrophages. Both human and mouse gliomas demonstrated high CD68 expression. CD68 expression was induced 2–5-fold higher in in vitro generated TAMs and in tumor-bearing brain compared to bone marrow, spleen, and blood immune cells. Transplantation of donor CD45.1 HSCs into lethally irradiated recipient CD45.2 mice led to reconstitution of blood lineages, which were stably maintained for over a 2-month monitoring period. Intracranial implantation of murine glioma cells seven weeks post-HSC transplantation led to infiltration of over 90% donor CD68⁺ myeloid cells into the brain TME. In the post tumor implantation cohort, recipient mice underwent intracranial implantation of murine glioma cells followed by transplantation with donor HSCs engineered with an hCD68 promoter–driven mCherry lentivirus. mCherry expression was detected in 40.05% ± 6.32% of CD68⁺ donor-derived TAMs specifically in the brain and was absent in donor-derived CD68⁺ lineages from the spleen, peripheral blood, and bone marrow. Collectively, these results demonstrate the utility of our macrophage-specific, TME induced HSC-based gene delivery platform as a modular system with the potential to be adapted to other immunosuppressive malignancies. Citation Format: Jianzhong Zhang, Edward J. Allen, Víctor A. Arrieta, Heba Ali, Ningjia Zhou, Venkatanagasai Raju Alluri, Michael D. McRaven, Sergio Barajas, Adam M. Sonabend, Amy B. Heimberger, Yan Liu, Ajit Chande, Atique U. Ahmed, Jason M. Miska, Catalina Lee-Chang, Peng Zhang, Thomas J. Hope, Crismita Dmello. Lentiviral-based hematopoietic stem cell platform for macrophage-specific expression in glioma immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(8_Suppl):Abstract nr LB145.