stereotactic-intracranial-implantation-glioblastoma-patient-derived

Stereotactic Intracranial Implantation of Glioblastoma Patient-derived Xenograft Cell Lines in Mice

The development of efficacious treatment regimens has been challenging for central nervous system tumors, in part due to the limited availability of ...

Mayo Clinic, Rochester

Glioblastoma (GBM) remains one of the most therapy-resistant malignancies with frequent local failures despite aggressive surgery, chemotherapy, and ionizing radiation (IR). Small molecule inhibitors of DNA-dependent protein kinase (DNA-PKi) are potent radiosensitizers currently in clinical trials. Determining which patients may benefit from radiosensitization with DNA-PKi is critical to avoid unnecessary increased risk of normal tissue toxicity. In this study, we used GBM patient-derived xenografts (PDX) in orthotopic murine models to study the relationship between molecular features, pharmacokinetics, and the radiosensitizing potential of the DNA-PKi peposertib. We show that peposertib radiosensitizes established and PDX GBM lines in vitro at 300 nmol/L and above, with a significant increase in radiosensitization by maintaining post-IR exposure for >12 hours. Radiosensitization by peposertib is mediated by catalytic inhibition of DNA-PK, and knockdown of DNA-PK by short hairpin RNA (shRNA) largely abolished the radiosensitizing effect. Peposertib decreased auto-phosphorylation of DNA-PKcs after IR in a dose-dependent manner with a delay in resolution of γH2AX foci at 24 hours. The addition of peposertib to IR significantly increased survival in GBM120 orthotopic xenografts, but not in GBM10. There was no difference in plasma or average tumor concentrations of peposertib in the two cohorts. Although the mechanism underpinning this discordant effect in vitro versus in vivo is not clear, there was an association for greater sensitization in TP53 mutant lines. Transfection of a dominant-negative TP53 mutant in baseline TP53 wild-type GBM lines significantly delayed growth and decreased nonhomologous end joining efficiency (but not homologous recombination), after peposertib exposure. See related commentary by Buchsbaum, p. 840.

DNA-PK Inhibition Shows Differential Radiosensitization in Orthotopic GBM PDX Models Based on DDR Pathway Deficits.

Ataxia Telangiectasia-mutated (ATM) inhibitors are being developed as radiosensitizers to improve the antitumor effects of radiotherapy, but ATM inhibition can also radiosensitize normal tissues. Therefore, understanding the elevated risk of normal tissue toxicities is critical for radiosensitizer development. This study focused on modeling the relationship between acute mucosal toxicity, radiation dose, fractionation schedule, and radiosensitizer exposure. The ATM inhibitor WSD0628 was combined with single or fractionated doses of radiation delivered to the oral cavity or esophagus of Friend Leukemia virus B (FVB) mice. The potentiation by WSD0628 was quantified by a sensitizer enhancement ratio (SER), which describes the changes in radiation tolerance for radiation combined with WSD0628 relative to radiation-only regimens. WSD0628 profoundly enhanced radiation-induced acute oral and esophageal toxicities. For oral mucosal toxicity, the enhancement by WSD0628 with 3 fractions of radiation resulted in an SER ranging from 1.3 (0.25 mg/kg) to 3.1 (7.5 mg/kg). For the 7.5 mg/kg combination, the SER increased with increasing number of fractions from 2.2 (1 fraction) to 4.3 (7 fractions) for oral toxicity and from 2.2 (1 fraction) to 3.6 (3 fractions) for esophageal toxicity, which reflects a loss of the normal tissue sparing benefit of fractionated radiation. These findings were used to develop a modified biologically effective dose model to determine alternative radiation schedules with or without WSD0628 that result in similar levels of toxicity. Successful radiosensitizer dose escalation to a maximally effective therapeutic dose will require careful deliberation of tumor site and reduction of radiation dose volume limits for organs at risk.

Modeling the Acute Mucosal Toxicity of Fractionated Radiotherapy Combined with the ATM Inhibitor WSD0628.

Most oncology therapeutics have limited distribution into the brain, and developing strategies to overcome this limitation would be clinically impactful. While therapeutic radiation is often cited as a strategy to accomplish this, there are no published studies demonstrating the effect of radiation on drug distribution into the brain or brain tumors.

The impact of therapeutic radiation on drug distribution across the blood-brain barrier in normal mouse brain and orthotopic glioblastoma tumors.

The ataxia-telangiectasia mutated (ATM) protein coordinates the cellular response to therapeutic radiation, and ATM inhibitors can potentially enhance the efficacy of radiation in otherwise radiation-resistant tumors.

The novel brain penetrant ataxia-telangiectasia mutated inhibitor WSD0628 provides robust radiosensitization of brain tumor patient-derived xenografts.

Navtemadlin is a potent small-molecule inhibitor of MDM2, which has completed a phase 0 window-of-opportunity study in glioblastoma (GBM). To optimally interpret the clinical data, a detailed analysis of navtemadlin pharmacokinetics (PK), pharmacodynamics, and efficacy was performed in GBM patient-derived xenografts (PDX).

Preclinical Modeling of Navtemadlin Pharmacokinetics, Pharmacodynamics, and Efficacy in IDH-Wild-type Glioblastoma.

Radiation exposure to the eye during cancer treatment can lead to ocular radiation injury (ORI), a devastating condition that can have a profound and permanent impact on vision-related quality of life. Rodent models do not have adequate ocular anatomy to accurately simulate human ORI, and modeling in non-human primates is limited by logistical and ethical concerns. To improve future translational research investigating ways to treat or prevent ORI, we developed protocols for a tree shrew model of ORI. Northern tree shrews () were obtained by our laboratory. Custom housing and handling methods were developed, including custom body suits to maintain the tree shrew's body temperature during procedures. Radiation delivery was optimized to accurately deliver radiation, and imaging was performed to observe fundus changes from ORI. Optimization of tree shrew handling, housing, anesthesia approaches, radiation delivery, and clinically-relevant ocular imaging permitted successful induction and assessment of ORI in tree shrews. With these protocols, tree shrews can be used as a highly relevant model organism with key anatomic features similar to humans to study ORI.

Optimizing procedures for ocular radiation injury studies in the tree shrew.

Murine double minute 2 (MDM2) inhibitors reactivate wild-type p53 and are a promising therapy for glioblastoma, IDH-wildtype (GBM). Brigimadlin is a highly potent MDM2 inhibitor being tested in a phase 0/1 clinical trial in combination with radiation in GBM.

Article	Year
DNA-PK Inhibition Shows Differential Radiosensitization in Orthotopic GBM PDX Models Based on DDR Pathway Deficits. Molecular cancer therapeutics\| PubMed ID: 39440433	2025
Modeling the Acute Mucosal Toxicity of Fractionated Radiotherapy Combined with the ATM Inhibitor WSD0628. Molecular cancer therapeutics\| PubMed ID: 39559836	2025
The impact of therapeutic radiation on drug distribution across the blood-brain barrier in normal mouse brain and orthotopic glioblastoma tumors. Neuro-oncology\| PubMed ID: 40163716	2025
The novel brain penetrant ataxia-telangiectasia mutated inhibitor WSD0628 provides robust radiosensitization of brain tumor patient-derived xenografts. Neuro-oncology\| PubMed ID: 40230030	2025
Preclinical Modeling of Navtemadlin Pharmacokinetics, Pharmacodynamics, and Efficacy in IDH-Wild-type Glioblastoma. Clinical cancer research : an official journal of the American Association for Cancer Research\| PubMed ID: 40591434	2025
Optimizing procedures for ocular radiation injury studies in the tree shrew. Exploration of targeted anti-tumor therapy\| PubMed ID: 41357135	2025
Pharmacokinetic-pharmacodynamic-efficacy modeling of the MDM2 inhibitor brigimadlin in glioblastoma patient-derived xenografts. Neuro-oncology advances\| PubMed ID: 41664821	2026

Lauren L. Ott

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