Phase I study of gadolinium texaphyrin in newly diagnosed glioblastoma

Abstract

2064 Background: Gadolinium texaphyrin (Gad Tex) is a putative radiosensitizer which inhibits cellular respiration resulting in the production of reactive oxygen species and induces apoptosis (Drugs R D. 2004; 5(1):52–7). Methods: The New Approaches to Brain Tumor Therapy (NABTT) consortium conducted a prospective phase I dose-escalation trial to determine the maximum tolerated dose of Gad Tex along with brain radiation therapy (RT) in newly diagnosed glioblastoma multiforme with KPS > 60. RT was 60 Gy in 30 fractions, 5 days per week over 6 weeks, to localized treatment fields. Two different dosing regimens of Gad Tex were utilized. In regimen A, the initial dose was 2.5 mg/kg with each daily fraction of RT whereas in regimen B it was 5.5 mg/kg with every fraction of RT. Gad Tex was administered 2–5 hours before each radiation treatment. Results: The initial dose in both regimen A and B was found not to be tolerable. Of three patients treated at 2.5 mg/kg/dose on regimen A (daily dosing), one completed planned therapy (30 doses of Gad Tex), one had treatment stopped after 16 doses of Gad Tex when diffuse pulmonary infiltrates with shortness of breath developed and returned after rechallenge with an additional dose of Gad Tex, and one patient developed an allergic reaction after 15 doses of Gad Tex which returned on rechallenge. Of three patients treated at 5.5 mg/kg/dose (qod dosing) on regimen B, one completed planned therapy (15 doses of Gad Tex) after a dose reduction related for skin blisters, and the other two patients discontinued treatment after 9 doses of Gad Tex for debilitating skin blisters. Conclusions: Gad Tex was poorly tolerated as administered in this small phase I study as 4 of 6 patients experienced dose limiting toxicities. As such, NABTT elected not to pursue this drug in subsequent clinical trials. However, similar or more intensive regimens utilizing Gad Tex in combination with brain RT have been successfully administered in patients with newly diagnosed glioblastoma and brain metastases. No significant financial relationships to disclose.