Reprogramming Macrophages Using Autologous Hematopoietic Stem Cells As Immunotherapy for Glioblastoma: TEM-GBM Study (NCT03866109)

Background: Bone marrow-derived macrophages represent an Important driver of clinical outcomes for many solid tumors. By contributing to changes in the local inflammatory tumor microenvironment (TME), tumor growth and disease progression occurs more quickly. We have developed a cell-based platform that harnesses the power of hematopoietic stem cells (HSC) to change the activity and role of macrophages that may provide a durable and safe treatment for solid tumors.

Temferon is an autologous HSC-based platform that delivers IFNa into the TME in a targeted manner via Tie-2 expressing monocytes (TEMs), with transcriptional and post-transcriptional controls mediated by miRNA target sequences.

Material & Methods: TEM-GBM is an open-label, Phase 1/2a dose-escalation study evaluating the safety and efficacy of escalating doses of Temferon in 21 newly diagnosed glioblastoma patients with unmethylated MGMT promoter. Key eligibility criteria include age 18-70 years, ECOG 0-1 and KPS >70%, and adequate cardiac, renal, hepatic & pulmonary function. Important exclusion criteria include the presence of active autoimmune disease or receipt of any oral or parenteral chemotherapy or immunotherapy within 2 years of screening. Patients requiring moderate or high doses of corticosteroid are also excluded. Autologous CD34+ HSPC are mobilized with lenograstim and plerixafor, collected by apheresis, purified and ex vivo modified with a lentiviral vector that enables HSC TEMs progeny to be loaded with IFN-a. So far, up to 3 million Temferon cells/kg have been co-administered with a fixed dose of non-manipulated CD34+ supporter cells following a sub-myeloablative conditioning regimen (Thiotepa + BCNU/Busulfan).

Results: As of July 2022, 4 escalating doses of Temferon (0.5-3.0x10⁶/kg) were tested across 17 patients assigned to 6 cohorts. Current total follow-up following Temferon infusion is 7-749 days months (3-28 months after 1^st Surgery). To date, no DLTs have been identified. In all patients, we observed rapid engraftment of gene modified progenitors and fast recovery from the sub-myeloablative conditioning regimens used (median engraftment across all the cohorts: Neutrophils D+13, Platelets D+14 following Temferon infusion). A dose ordered increased in Temferon-derived progeny was seen, as defined by the presence of gene-marked cells in peripheral blood. Edited cells were identified within two weeks of Temferon administration & persisted, albeit at lower levels, up to 18 months following Temferon Infusion (longest time of analysis). Despite the substantial high proportion of engineered cells, very low concentrations of IFNα were detected in the plasma and in the CSF, indicating tight regulation of transgene expression. SAEs were mostly attributed to conditioning chemotherapy (e.g. infections) or disease progression.

Potential long-term benefit with Temferon was identified in a patient who received 2.0x10⁶/kg. After Temferon administration the patient experienced a persistent GGT elevation (from D+79), reported as a SUSAR which spontaneously resolved, and at D+120 disease progression was reported. Thereafter MRI showed an increase in tumor necrosis, an approximate 40% reduction in enhancing tumor volume, and the patient remained clinically stable 1 year following Temferon, with no 2nd line therapy added. The patient reached the 2 years follow-up timepoint in July with stable disease identified.

Seven recurrent tumors were resected and where enough fresh material was available gene-marked cells were identified in the CD45+ tumor infiltrate in 2/2 specimens (3%-5%). scRNA analysis of the myeloid TME compartment (n=4 Temferon patients) detected a broad induction of an IFN, TNF/NFkB & hypoxia response relative to n=6 standard-of-care treated patients and unveiled an overrepresentation of pro-inflammatory macrophage clusters. Notably, the highest proportion of pro-inflammatory macrophages was detected in a stable lesion biopsied from a patient that had a contemporaneous progressing lesion, which instead contained the lowest pro-inflammatory macrophage quantity.

Conclusions: Our interim results show that Temferon is well tolerated, with no dose limiting toxicities identified to date. The results provide initial evidence of Temferon's potential to modulate the TME of GBM patients, and anecdotal evidence for long lasting effects of Temferon in prevention of disease progression.

Gentner:ExCellThera: Consultancy; Genenta Science: Consultancy, Current holder of stock options in a privately-held company, Other: Founder, Research Funding. Ciceri:Kite Pharma: Consultancy.