Design considerations of an IL13Rα2 antibody–drug conjugate for diffuse intrinsic pontine glioma

Abstract

Diffuse intrinsic pontine glioma (DIPG), a rare pediatric brain tumor, afflicts approximately 350 new patients each year in the United States. DIPG is noted for its lethality, as fewer than 1% of patients survive to five years. Multiple clinical trials involving chemotherapy, radiotherapy, and/or targeted therapy have all failed to improve clinical outcomes. Recently, high-throughput sequencing of a cohort of DIPG samples identified potential therapeutic targets, including interleukin 13 receptor subunit alpha 2 (IL13Rα2) which was expressed in multiple tumor samples and comparably absent in normal brain tissue, identifying IL13Rα2 as a potential therapeutic target in DIPG. In this work, we investigated the role of IL13Rα2 signaling in progression and invasion of DIPG and viability of IL13Rα2 as a therapeutic target through the use of immunoconjugate agents. We discovered that IL13Rα2 stimulation via canonical ligands demonstrates minimal impact on both the cellular proliferation and cellular invasion of DIPG cells, suggesting IL13Rα2 signaling is non-essential for DIPG progression in vitro. However, exposure to an anti-IL13Rα2 antibody–drug conjugate demonstrated potent pharmacological response in DIPG cell models both in vitro and ex ovo in a manner strongly associated with IL13Rα2 expression, supporting the potential use of targeting IL13Rα2 as a DIPG therapy. However, the tested ADC was effective in most but not all cell models, thus selection of the optimal payload will be essential for clinical translation of an anti-IL13Rα2 ADC for DIPG.

IL-13Rα2 Status Predicts GB-13 (IL13.E13K-PE4E) Efficacy in High-Grade Glioma

“…To identify baseline transcript and protein levels of IL-13Rα2 in HGG cells, we performed RNA sequencing and immunoblotting on patient-derived HGG (DMG and adult GBM) cell lines ( Figure 1 ). In accordance with previous investigations [ 16 , 52 , 53 ], our cohort of sequenced HGG transcriptomes demonstrated highly variable expression of IL-13Rα2 RNA among HGG cell lines ( Figure 1 A), ranging from low (SU-DIPG XIII-P, GBM39, and GBM108) to intermediate (SU-DIPG XVII, SF8628, GBM43, and GBM6) and high (PED17, GBM10, and GBM14) expression. Next, we evaluated IL-13Rα2 protein levels in available HGG cell lines.…”

“…IL-13Rα2 has long been recognized as a prognostic biomarker for poor disease prognosis in brain tumors including HGG [ 16 , 32 , 59 ]. While the negligible impact of canonical ligand-mediated IL-13Rα2 stimulation on cell proliferation in IL-13Rα2-high versus IL-13Rα2-low cell lines was somewhat surprising, similar results have been previously reported in cell growth and invasion studies [ 52 ]. Recent investigations have elucidated the role of IL-13Rα2 as a tumor-associated antigen that mediates aberrant STAT3 signaling, driving increased expression of anti-apoptotic genes and, ultimately, promoting tumor progression by blocking cell death and mediating survival [ 17 , 59 , 60 ].…”

“…While the lack of SU-DIPG XIII-P response was consistent with the low expression of IL-13Rα2 in the assayed cell models, none of the IL-13Rα2-medium or IL-13Rα2-high cell lines stimulated with IL-13 demonstrated any significant increase in cell proliferation versus media as the control ( Figure 2 A). Based on previous reports, demonstrating IL-13Rα2 is implicated in cell survival rather than cell growth and invasion [ 19 , 52 ], we hypothesized that cytokine stimulation would be associated with increased IL-13Rα2 expression to enforce this anti-apoptotic effect. To test this, we stimulated HGG cells with IL-13 (10 ng/mL) and investigated protein levels at various time points ( Figure 2 D).…”

Treatment Limitations for Pediatric Diffuse Intrinsic Pontine Gliomas in a Middle-Income Country

“…Despite multiple efforts made to improve outcomes of DIPG patients worldwide, there is lack of consensus of a standard treatment protocol. 18 Additionally, a big concern remains of DIPG treatment in MICs, where multiple limitations influence on the final outcome. 19 DIPG remains an orphan disease in MICs, and the registry and documentation of the evolution of the disease is scarce.…”

A New Mouse Model of Diffuse Midline Glioma to Test Targeted Immunotherapies

“…Another attractive immunotherapeutic target in pediatric HGG is interleukin-13 receptor alpha 2 (IL13Rα2). High expression of IL13Rα2 has been described in DIPG and other pHGG tissues 4,12,13 . Within adult-type diffuse gliomas, IL13Rα2 targeting therapies have been the focus of multiple preclinical and clinical studies.…”