131I-omburtamab Delivered by Convection-Enhanced Delivery in Patients With Diffuse Intrinsic Pontine Glioma

Omburtamab is a murine IgG1 monoclonal antibody, recognizing CD276 (also known as B7- H3). Omburtamab is 131I-labeled at designated radio pharmacies and will be provided as a final radiolabeled product to treatment site. The proposed intervention includes surgical placement using standard stereotactic techniques of a small caliber cannula into the tumor in the pons followed by positive pressure infusion (i.e. CED) of 131I-omburtamab. Iodine-131 conjugated omburtamab (131I-omburtamab) administered via the intracerebroventricular route for the treatment of metastatic CNS neuroblastoma was shown to be tolerable and improve survival. Furthermore, 124I-omburtamab administered by convection enhanced delivery (CED) was shown to have a tolerable safety profile in an ongoing dose escalation trial (in doses up to 4mCi) in patients with diffuse pontine gliomas that have not progressed following external beam radiation therapy. The aim of this trial is to determine the efficacy and safety of 131I-omburtamab in patients with DIPG that have not progressed following external beam radiation therapy.

The IMP infusion volume for CED will be adjusted to 4, 6 or 8 mL dependent on the size of the tumor as estimated by MRI. The maximum volume of 8 mL was tested, and safety cleared in the 11-011 trial. Assuming a ratio of approximately 1:3 between the infusion volume and the distribution volume the infusion volume will be adjusted to ensure coverage of the tumor and 0.5 cm of the surrounding margin. The infusion volume will be 4 mL if tumor size (+0.5 cm margin) \<10 cm3, 6 mL if tumor size (+0.5 cm margin) ≥10 and \<15 cm3, and 8 mL if tumor size (+0.5 cm margin) ≥15 and ≤20 cm3. The maximum infusion rate will be 10 μL/min. Infusions will be initiated using an escalating flow rate plan with 10-min intervals until the maximum rate is achieved (0·5 μL/min, 1·0 μL/min, 2·0 μL/min, 5·0 μL/min, 7·5 μL/min and 10 μL/min).