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

Abstract

Purpose: The purpose of the present study was to evaluate the anti^epidermal growth factor receptor (EGFR) monoclonal antibody (mAb), cetuximab, (IMC-C225) and the anti-EGFRvIII mAb, L8A4, used in combination as delivery agents for boron neutron capture therapy (BNCT) of a rat glioma composed of a mixture of cells expressing either wild-type (F98 EGFR ) or mutant receptors(F98 npEGFRvIII ). Experimental Design: A heavily boronated polyamidoamine dendrimer (BD) was linked by heterobifunctional reagents to produce the boronated mAbs, BD-C225 and BD-L8A4. For in vivo biodistribution and therapy studies, a mixture of tumor cells were implanted intracerebrally into Fischer rats. Biodistribution studies were carried out by administering 125 I-labeled bioconjugates via convection-enhanced delivery (CED), and for therapy studies, nonradiolabeled bioconjugates were used for BNCT. This was carried out 14 days after tumor implantation and 24 h after CED at the Massachusetts Institute of Technology nuclear reactor. Results: Following CED of a mixture of 125 I-BD-C225 and 125 I-BD-L8A4 to rats bearing composite tumors, 61.4% of the injected dose per gram (ID/g) was localized in the tumor compared with 30.8% ID/g for 125 I-BD-L8A4 and 34.7% ID/g for 125 I-BD-C225 alone. The corresponding calculated tumor boron values were 24.4 Ag/g for rats that received both mAbs, and 12.3 and 13.8 Ag/g, respectively, for BD-L8A4 or BD-C225 alone. The mean survival time of animals bearing composite tumors, which received both mAbs, was 55 days (P < 0.0001) compared with 36 days for BD-L8A4 and 38 days for BD-C225 alone, which were not significantly different from irradiated controls. Conclusions: Both EGFRvIII and wild-type EGFR tumor cell populations must be targeted using a combination of BD-cetuximab and BD-L8A4. Although in vitro C225 recognized both receptors, in vivo it was incapable of delivering the requisite amount of 10 B for BNCT of EGFRvIII-expressing gliomas.

Thymidine kinase 1 as a molecular target for boron neutron capture therapy of brain tumors

“…via the penile vein 2.5 h. before neutron irradiation. All irradiated rats were anesthetized with a mixture of ketamine and xylazine, after which they were irradiated at the MITR-II reactor, as previously described by us (11,30). Dosimetry and Clinical Monitoring.…”

“…Dosimetry and Clinical Monitoring. Dosimetric measurements were performed, as previously described (11,30). The measured absorbed dose rates in mice (muscle Ϫ3.5% nitrogen by weight) at the position of the tumor and normalized to the reactor operating at 5 MW were 0.20 Ϯ .01 Gy⅐min Ϫ1 for ␥ photons, 0.13 Ϯ 0.01 Gy⅐min Ϫ1 for thermal neutrons (principally capture in nitrogen 14 N [n, p] 14 C), and 0.04 Gy⅐min Ϫ1 for neutron capture per g of 10 B in tissue.…”

Epidermal Growth Factor Receptor Expression Identifies Functionally and Molecularly Distinct Tumor-Initiating Cells in Human Glioblastoma Multiforme and Is Required for Gliomagenesis

“…Likewise, EGFR gene amplification is positively correlated with molecularly defined GBM subclasses, characterized by active proliferation and poor prognosis (21). Valuable preclinical information has also been obtained by modulating EGFR expression in standard serum-cultured glioma cell lines (22)(23)(24)(25) and by using these in vitro cultures for testing different therapeutic approaches (26).…”

Dendrimer Conjugates for Drug Delivery

“…143 The use of the anti -EGF receptor MoAbs was alternatively used for targeting purposes, 144 with encouraging in vivo results for biodistribution. 145,146 Other receptors overexpressed at tumoral sites like VEGFR and FAR are currently being assayed on boronated dendrimeric platforms for BNCT purposes. For instance, a generation 5 PAMAM dendrimer equipped with 102 to 110 decaboranes, a fl uorescent tag, and VEGF was found to accumulate in vitro in VEGFR expressing cells via a VEGFR -2 mechanism.…”