Pharmacologic inhibition of OLIG2 by CT-179 disrupts mitotic progression and enhances standard-of-care chemoradiotherapy in glioblastoma
Abstract
Background: Glioblastoma (GBM) remains uniformly fatal. The basic helix-loop-helix transcription factor OLIG2 is universally expressed in diffuse glioma, sustains the tumor-propagating stem-like fraction, and opposes p53-mediated genotoxic responses, but has historically been considered undruggable. We characterized CT-179, a brain-penetrant small-molecule OLIG2 inhibitor, as a candidate therapeutic for GBM.
Methods: Target engagement was assessed by cellular thermal shift assay, differential scanning fluorimetry, crosslinking, and electrophoretic mobility shift assay. Anti-tumor activity was evaluated across eleven patient-derived GBM cell lines, in zebrafish oligodendrocyte precursor cell (OPC)-derived tumors, and orthotopic and subcutaneous GBM models, including combinations with radiotherapy plus temozolomide and with selective Bcl-2 family inhibitors. Results: CT-179 engaged OLIG2 and altered the conformation of dimerized OLIG2 on chromatin without preventing dimerization or fully displacing OLIG2 from DNA. CT-179 reduced OLIG2-positive OPC’s and OPC-derived tumors in zebrafish and inhibited proliferation across all eleven GBM lines (IC50 < 360 nM), depleting the stem-like fraction and inducing apoptosis through mitotic catastrophe, mitotic slippage, or a hybrid response. RNA-seq across three patient-derived glioma stem cell lines identified β-tubulin gene isoforms as the most strongly CT-179-down-regulated transcripts at the early time point and showed correlated β-tubulin and OLIG2 expression in TCGA glioblastoma specimens. Combination with the Mcl-1 inhibitor S63845 or the Bcl-2/Bcl-xL/Bcl-w inhibitor ABT-737 produced greater-than-additive cytotoxicity. Oral CT-179 crossed the blood-brain barrier and extended median survival as a single agent across two independent adult orthotopic patient-derived backgrounds (GBM8 and G06); intraperitoneal CT-179 was associated with reduced intratumoral OLIG2 and Ki-67 staining in GBM8 orthotopic xenografts. Combination of CT-179 with radiotherapy and temozolomide eliminated all GBM8 and 7 of 8 GBM4 subcutaneous xenografts without weight loss and significantly extended survival when combined with radiotherapy in MGMT-unmethylated GBM6 orthotopic xenografts (CT-179 administered intraperitoneally).
Conclusions: CT-179 is a brain-penetrant inhibitor of an established GBM driver with single-agent and combination activity across several orthotopic models, supporting clinical development for GBM and translational evaluation in other OLIG2-dependent CNS malignancies.
Key Points: CT-179 is the first brain-penetrant small-molecule inhibitor of OLIG2 with potent activity across patient-derived glioblastoma models.
CT-179 induces apoptosis through mitotic catastrophe and slippage rather than collapse of receptor tyrosine kinase signaling.
Oral CT-179 combined with radiotherapy and temozolomide eliminates the great majority of subcutaneous patient-derived GBM xenografts without overt toxicity.
Oral CT-179 extends single-agent survival across two independent adult orthotopic patient-derived backgrounds (GBM8 and G06); intraperitoneal CT-179 is associated with reduced intratumoral OLIG2 and Ki-67 staining in GBM8 tumors.
Intraperitoneal CT-179 plus radiotherapy significantly extends survival in an MGMT-unmethylated GBM6 orthotopic model where temozolomide contributes minimally and supports the rationale for further evaluation in MGMT-unmethylated GBM.
Importance of the Study: Glioblastoma is uniformly fatal, and durable disease-modifying therapies that disable the lineage transcription factor programs sustaining the GBM stem-like state have remained elusive. OLIG2 is universally expressed in diffuse glioma and is a central driver of stemness, lineage-restricted RTK signaling, and resistance to genotoxic therapy, yet has historically been considered undruggable. This study reports the foundational preclinical characterization of CT-179, a brain-penetrant small molecule that engages OLIG2 directly and induces glioblastoma cell death through disrupted mitotic progression. Oral CT-179 crosses the blood-brain barrier, prolongs survival in orthotopic patient-derived xenografts, and substantially enhances the efficacy of standard-of-care radiotherapy and temozolomide. Activity in an MGMT-unmethylated orthotopic patient-derived GBM model in combination with radiotherapy is of particular translational interest, since this is the patient population for which temozolomide contributes minimally and the unmet need is greatest. These data establish proof of concept for direct pharmacologic inhibition of OLIG2 in GBM and provide a translational rationale, including an MGMT-stratified combination strategy, for combining CT-179 with current standard-of-care chemoradiotherapy.
Lay Summary: Glioblastoma is the most common and aggressive brain cancer in adults, and almost all patients die of their disease. One reason is a protein called OLIG2, which keeps tumor cells in an immature, treatment-resistant state and has long been considered impossible to target with drugs. We studied CT-179, a small molecule that enters the brain and blocks OLIG2. In glioblastoma cells and in mice, CT-179 forced dividing tumor cells into a faulty, lethal division, extended survival on its own, and strengthened the effect of standard radiation and chemotherapy. These results support testing CT-179 in people with glioblastoma.
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BibTeX
@misc{greenall2026pharmacologic,
title = {{Pharmacologic inhibition of OLIG2 by CT-179 disrupts mitotic progression and enhances standard-of-care chemoradiotherapy in glioblastoma}},
author = {Sam A. Greenall and Shengnan C. Chen and Gordon Alton and Graham Beaton and Reghan Boelter and Mattie Casey and Ivan Babic and Zara C. Bruce and Daniel J. Garama and Rajesh Mukthavaram and Fabio C. Tucci and Satheesh B. Ravula and Ambrosio Lopez and Susan Knowles and Gregory D. Stein and Yuchen Li and Bennett Stork and Rochelle D’Souza and Ashwani Kumar and Ralf Kittler and Ann C.M. Tuma and Jann N. Sarkaria and Daniel J. Gough and Rodney A. Stewart and Santosh Kesari and Bryan W. Day and Terrance G. Johns},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.14.759257},
url = {https://www.biorxiv.org/content/10.64898/2026.10.14.759257v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Pharmacologic inhibition of OLIG2 by CT-179 disrupts mitotic progression and enhances standard-of-care chemoradiotherapy in glioblastoma
AU - Sam A. Greenall
AU - Shengnan C. Chen
AU - Gordon Alton
AU - Graham Beaton
AU - Reghan Boelter
AU - Mattie Casey
AU - Ivan Babic
AU - Zara C. Bruce
AU - Daniel J. Garama
AU - Rajesh Mukthavaram
AU - Fabio C. Tucci
AU - Satheesh B. Ravula
AU - Ambrosio Lopez
AU - Susan Knowles
AU - Gregory D. Stein
AU - Yuchen Li
AU - Bennett Stork
AU - Rochelle D’Souza
AU - Ashwani Kumar
AU - Ralf Kittler
AU - Ann C.M. Tuma
AU - Jann N. Sarkaria
AU - Daniel J. Gough
AU - Rodney A. Stewart
AU - Santosh Kesari
AU - Bryan W. Day
AU - Terrance G. Johns
PY - 2026
DA - 2026/10/14
PB - bioRxiv
DO - 10.64898/2026.10.14.759257
UR - https://www.biorxiv.org/content/10.64898/2026.10.14.759257v1
AB - Background: Glioblastoma (GBM) remains uniformly fatal. The basic helix-loop-helix transcription factor OLIG2 is universally expressed in diffuse glioma, sustains the tumor-propagating stem-like fraction, and opposes p53-mediated genotoxic responses, but has historically been considered undruggable. We characterized CT-179, a brain-penetrant small-molecule OLIG2 inhibitor, as a candidate therapeutic for GBM. Methods: Target engagement was assessed by cellular thermal shift assay, differential scanning fluorimetry, crosslinking, and electrophoretic mobility shift assay. Anti-tumor activity was evaluated across eleven patient-derived GBM cell lines, in zebrafish oligodendrocyte precursor cell (OPC)-derived tumors, and orthotopic and subcutaneous GBM models, including combinations with radiotherapy plus temozolomide and with selective Bcl-2 family inhibitors. Results: CT-179 engaged OLIG2 and altered the conformation of dimerized OLIG2 on chromatin without preventing dimerization or fully displacing OLIG2 from DNA. CT-179 reduced OLIG2-positive OPC’s and OPC-derived tumors in zebrafish and inhibited proliferation across all eleven GBM lines (IC50 < 360 nM), depleting the stem-like fraction and inducing apoptosis through mitotic catastrophe, mitotic slippage, or a hybrid response. RNA-seq across three patient-derived glioma stem cell lines identified β-tubulin gene isoforms as the most strongly CT-179-down-regulated transcripts at the early time point and showed correlated β-tubulin and OLIG2 expression in TCGA glioblastoma specimens. Combination with the Mcl-1 inhibitor S63845 or the Bcl-2/Bcl-xL/Bcl-w inhibitor ABT-737 produced greater-than-additive cytotoxicity. Oral CT-179 crossed the blood-brain barrier and extended median survival as a single agent across two independent adult orthotopic patient-derived backgrounds (GBM8 and G06); intraperitoneal CT-179 was associated with reduced intratumoral OLIG2 and Ki-67 staining in GBM8 orthotopic xenografts. Combination of CT-179 with radiotherapy and temozolomide eliminated all GBM8 and 7 of 8 GBM4 subcutaneous xenografts without weight loss and significantly extended survival when combined with radiotherapy in MGMT-unmethylated GBM6 orthotopic xenografts (CT-179 administered intraperitoneally). Conclusions: CT-179 is a brain-penetrant inhibitor of an established GBM driver with single-agent and combination activity across several orthotopic models, supporting clinical development for GBM and translational evaluation in other OLIG2-dependent CNS malignancies. Key Points: CT-179 is the first brain-penetrant small-molecule inhibitor of OLIG2 with potent activity across patient-derived glioblastoma models. CT-179 induces apoptosis through mitotic catastrophe and slippage rather than collapse of receptor tyrosine kinase signaling. Oral CT-179 combined with radiotherapy and temozolomide eliminates the great majority of subcutaneous patient-derived GBM xenografts without overt toxicity. Oral CT-179 extends single-agent survival across two independent adult orthotopic patient-derived backgrounds (GBM8 and G06); intraperitoneal CT-179 is associated with reduced intratumoral OLIG2 and Ki-67 staining in GBM8 tumors. Intraperitoneal CT-179 plus radiotherapy significantly extends survival in an MGMT-unmethylated GBM6 orthotopic model where temozolomide contributes minimally and supports the rationale for further evaluation in MGMT-unmethylated GBM. Importance of the Study: Glioblastoma is uniformly fatal, and durable disease-modifying therapies that disable the lineage transcription factor programs sustaining the GBM stem-like state have remained elusive. OLIG2 is universally expressed in diffuse glioma and is a central driver of stemness, lineage-restricted RTK signaling, and resistance to genotoxic therapy, yet has historically been considered undruggable. This study reports the foundational preclinical characterization of CT-179, a brain-penetrant small molecule that engages OLIG2 directly and induces glioblastoma cell death through disrupted mitotic progression. Oral CT-179 crosses the blood-brain barrier, prolongs survival in orthotopic patient-derived xenografts, and substantially enhances the efficacy of standard-of-care radiotherapy and temozolomide. Activity in an MGMT-unmethylated orthotopic patient-derived GBM model in combination with radiotherapy is of particular translational interest, since this is the patient population for which temozolomide contributes minimally and the unmet need is greatest. These data establish proof of concept for direct pharmacologic inhibition of OLIG2 in GBM and provide a translational rationale, including an MGMT-stratified combination strategy, for combining CT-179 with current standard-of-care chemoradiotherapy. Lay Summary: Glioblastoma is the most common and aggressive brain cancer in adults, and almost all patients die of their disease. One reason is a protein called OLIG2, which keeps tumor cells in an immature, treatment-resistant state and has long been considered impossible to target with drugs. We studied CT-179, a small molecule that enters the brain and blocks OLIG2. In glioblastoma cells and in mice, CT-179 forced dividing tumor cells into a faulty, lethal division, extended survival on its own, and strengthened the effect of standard radiation and chemotherapy. These results support testing CT-179 in people with glioblastoma.
SN - 2692-8205
ER -