191 - Preclinical Evaluation of First-in-Class PROTAC Survivin Degrader HMAK101 for Radiosensitization for GBM, DIPG and Brain Metastases
Presenter(s)
S. Zheng1, J. Zhang2, B. Cui3, R. Yeeravalli2, G. Zhou4, E. Petrosyan2, J. A. Saab2, Y. Liu5, Y. Wei5, Y. Wu6, J. Fares2, S. Hosseinibarkooie7, S. H. S. Weng7, T. Sita1, G. E. Woloschak1, P. Zhang2, Y. Zhang5, I. Balyasnikova2, A. Ahmed2, and M. S. Lesniak8; 1Department of Radiation Oncology, Northwestern University Feinberg School of Medicine, Chicago, IL, 2Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL, 3State Key Laboratory of Vascular Homeostasis and Remodeling, Department of Cardiology and Institute of Vascular Medicine, Peking University Third Hospital, Beijing, IL, 4Institute for Protein Design, Department of Biochemistry, University of Washington, Seattle, WA, 5State Key Laboratory of Vascular Homeostasis and Remodeling, Department of Cardiology and Institute of Vascular Medicine, Peking University Third Hospital, Beijing, China, 6Department of Mathematics, DigiPen Institute of Technology, Redmond, WA, 7Proteomics Platform, Office of Shared Research Facilities, University of Chicago, Division of the Biological Sciences, Chicago, IL, 8Department of Neurological Surgery, Northwestern University Robert H. Lurie Comprehensive Cancer Center, Chicago, IL
Purpose/Objective(s): Most of previously irradiated glioblastoma (GBM) and diffuse intrinsic pontine gliomas (DIPG) develop local recurrence. Survivin is a well-known 'undruggable' radiation-resistance factor protein with high expression levels in malignant glioma cells. This study reports the mechanism, preclinical efficacy and toxicology profile of the first-in-class, CNS-penetrant PROteolysis TArgeting Chimeras (PROTAC) survivin degrader HMAK101 in radiosensitizing GBM and DIPG.
Materials/Methods: Surface plasmon resonance (SPR) assay measured the Kd of CRBN-HMAK101-survivin ternary structure. Pharmacodynamic (PK) study was performed in mouse, rat and cynomolgus monkey. DNA damage was evaluated with Comet assay, quantification of gamma H2AX foci as well as TUNEL assay. In vitro efficacy of HMAK101 in combination with RT was measured with colony formation assay and fitted with linear-quadratic model. Intratumoral PK study was performed in orthotopic GBM model. Toxicity study was performed in preclinical phase 1 dose escalation study. The in vivo efficacy of HMAK101 in combination with radiation (RT+HMAK101) was evaluated in GBM and DIPG orthotopic xenograft models.
Results: HMAK101 downregulates survivin in GBM PDCs in a time and dose-dependent manner with a half-maximal degradation concentrations (DC50s) after 24h treatment for GBM43, 0.05 nM; GL260, 0.51 nM; GBM123, 2.32 nM; U-87 MG, 8.18 nM; and GBM12, 616.59 nM. HMAK101 interacts with survivin with Kd of 102 nM in the SPR assay. HMAK101 induced DNA damage response in GBM and DIPG cells with significant gamma H2AX foci accumulation and DNA fragmentation. HMAK101 enhanced RT-induced DNA damage, caspase-3/-7 activation and ROS accumulation. In the rat PK studies, an I.V. dose of 2.0 mg/kg of HMAK101 brain parenchyma concentration at 2 h after injection (15.4 ng/g) and 6h after injection (5.85 ng/g) with brain/plasma ratio 6.1% and 18.9%, respectively. In cynomolgus monkey, HMAK101 was readily detected in the CSF 2 hours after IV injection of 2.0 mg/kg of HMAK101. Intratumoral PK study showed HMAK101 was still readily detectable in the brain tumor 16 hours after I.V. dose of HMAK101 at 1 mg/kg and 2 mg/kg, suggesting daily dose regimen. Dose escalation toxicity study in mice with 0 mg/kg, 2 mg/kg, 4 mg/kg and 8 mg/kg of HMAK101 delivered daily with I.V. tail vein for 14 days showed minimal to no toxicities. Orthotopic GL261 GBM model demonstrated that RT+HMAK101 significantly prolonged the survival of mice with GBM as compared with the control or either treatment alone groups. In GBM38-Luc xenograft model, combination of HMAK101 with RT decreased the tumor burden, and prolonged the survival of the GBM bearing nude mice. Xenograft models for DIPG and breast cancer brain metastases are ongoing.
Conclusion: First-in-class PROTAC survivin degrader HMAK101 demonstrates low toxicity profile when used alone and in combination with RT. HMAK101 penetrates BBB, accumulates in the brain tumor tissue, and potentiated RT efficacy in vitro and in vivo.