Molecular Targeting and Treatment of an Epidermal Growth Factor Receptor–Positive Glioma Using Boronated Cetuximab

Abstract

Purpose: The purpose of the present study was to evaluate the anti^epidermal growth factor monoclonal antibody (mAb) cetuximab (IMC-C225) as a delivery agent for boron neutron capture therapy (BNCT) of a human epidermal growth factor receptor (EGFR) gene-transfected rat glioma, designated as F98 EGFR . Experimental Design: A heavily boronated polyamidoamine dendrimer was chemically linked to cetuximab by means of the heterobifunctional reagents N-succinimidyl 3-(2-pyridyldithio)-propionate and N-(k-maleimido undecanoic acid)-hydrazide. The bioconjugate, designated as BD-C225, was specifically taken up by F98 EGFR glioma cells in vitro compared with receptornegative F98 wild-type cells (41.8 versus 9.1 Ag/g). For in vivo biodistribution studies, F98 EGFR cells were implanted stereotactically into the brains of Fischer rats, and 14 days later, BD-C225 was given intracerebrally by either convection enhanced delivery (CED) or direct intratumoral (i.t.) injection. Results: The amount of boron retained by F98 EGFR gliomas 24 h following CED or i.t. injection was 77.2 and 50.8 Ag/g, respectively, with normal brain and blood boron values <0.05 Ag/g. Boron neutron capture therapy was carried out at the Massachusetts Institute of TechnologyResearch Reactor 24 h after CED of BD-C225, either alone or in combination with i.v. boronophenylalanine (BPA). The corresponding mean survival times (MST) were 54.5 and 70.9 days (P = 0.017), respectively, with one long-term survivor (more than 180 days). In contrast, the MSTs of irradiated and untreated controls, respectively, were 30.3 and 26.3 days. In a second study, the combination of BD-C225 and BPA plus sodium borocaptate, given by either i.v. or intracarotid injection, was evaluated and the MSTs were equivalent to that obtained with BD-C225 plus i.v. BPA. Conclusions:The survival data obtained with BD-C225 are comparable with those recently reported by us using boronated mAb L8A4 as the delivery agent.This mAb recognizes the mutant receptor, EGFRvIII. Taken together, these data convincingly show the therapeutic efficacy of molecular targeting of EGFR using a boronated mAb either alone or in combination with BPA and provide a platform for the future development of combinations of high and low molecular weight delivery agents for BNCTof brain tumors.Boron neutron capture therapy (BNCT) is based on the nuclear capture and fission reactions that occur when nonradioactive boron-10 is irradiated with low energy (e V 0.025 eV) thermal neutrons to produce 11 B in an unstable form, which undergoes instantaneous nuclear fission to produce a-particles and recoiling lithium-7 nuclei. These high linear energy transfer particles have a range of 5 to 9 Am, thereby restricting their destructive effects to only those cells containing 10 B. To be

Molecular Targeting and Treatment of Composite EGFR and EGFRvIII-Positive Gliomas Using Boronated Monoclonal Antibodies

“…As we have previously reported (18), when 125 I-BD-L8A4 was administered to animals bearing F98 npEGFRvIII tumors or 125 I-BD-C225 to rats bearing F98 EGFR gliomas (19), the amount of radioactivity localized in the tumors was almost equivalent (60.1% and 53.3% ID/g, respectively) to that observed in the present study (61.4% ID/g; Table 1). The data from the biodistribution studies were predictive of those obtained in the therapy studies.…”

“…As previously reported, the best survival data in animals bearing homotypic tumors were obtained with BD-L8A4 in F98 npEGFRvIII glioma -bearing rats (18), and with BD-C225 in rats bearing F98 EGFR gliomas (19).…”

“…The greatest prolongation in survival time of animals bearing composite tumors was seen following the administration of boronated cetuximab and L8A4 with a MST of 55 F 5 days and a range of 37 to 87 days. Almost identical survival data were obtained in rats bearing EGFR-expressing tumors that had received boronated cetuximab ( In a recently published report (19), we had concluded that cetuximab would be the best choice as a boron delivery agent for several reasons. First, it has been shown to be clinically active against a variety of EGFR(+) tumors, including colon cancer metastatic to the liver and recurrent squamous cell carcinoma of the head and neck (26,27,55).…”

“…F98 EGFR and F98 npEGFRvIII cells were produced by transfecting F98 cells with the human genes encoding either wild-type EGFR (19,39) or its mutant isoform, EGFRvIII (17). The resulting cell lines, respectively designated F98 EGFR and F98 npEGFRvIII , expressed f1.2 Â 10 5 receptor sites of either wildtype EGFR or EGFRvIII.…”

Enhanced Survival and Cure of F98 Glioma–Bearing Rats following Intracerebral Delivery of Carboplatin in Combination with Photon Irradiation

“…It has been used experimentally by one of us (R.F.B.) to enhance the delivery of boronated anti -epidermal growth factor monoclonal antibodies for boron neutron capture therapy (24,25).…”