Novel Human Antibodies to Insulin Growth Factor 2 Receptor (IGF2R) for Radioimmunoimaging and Therapy of Canine and Human Osteosarcoma

Abstract

Etiological and genetic drivers of osteosarcoma (OS) are not well studied and vary from one tumor to another; making it challenging to pursue conventional targeted therapy. Recent studies have shown that cation independent mannose-6-phosphate/insulin-like growth factor-2 receptor (IGF2R) is consistently overexpressed in almost all of standard and patient-derived OS cell lines, making it an ideal therapeutic target for development of antibody-based drugs. Monoclonal antibodies, targeting IGF2R, can be conjugated with alpha- or beta-emitter radionuclides to deliver cytocidal doses of radiation to target IGF2R expression in OS. This approach known as radioimmunotherapy (RIT) can therefore be developed as a novel treatment for OS. In addition, OS is one of the common cancers in companion dogs and very closely resembles human OS in clinical presentation and molecular aberrations. In this study, we have developed human antibodies that cross-react with similar affinities to IGF2R proteins of human, canine and murine origin. We used naïve and synthetic antibody Fab-format phage display libraries to develop antibodies to a conserved region on IGF2R. The generated antibodies were radiolabeled and characterized in vitro and in vivo using human and canine OS patient-derived tumors in SCID mouse models. We demonstrate specific binding to IGF2R and tumor uptake in these models, as well as binding to tumor tissue of canine OS patients, making these antibodies suitable for further development of RIT for OS

Radioimmunotherapy Targeting IGF2R on Canine-Patient-Derived Osteosarcoma Tumors in Mice and Radiation Dosimetry in Canine and Pediatric Models

“…Human, canine and murine IGF2R-binding IF3 mAb was expressed and purified in our laboratories as described in [13]. SG-iTLC (silica gel instant thin layer chromatography) strips for quantification of radiolabeling yields were acquired from Agilent (Mississauga, ON, Canada).…”

“…111 In was obtained from BWXT (Cambridge, ON, Canada), and 177 Lu, from RadioMedix (Houston, TX, USA). IF3 mAb was conjugated to 2.5 initial molar excess of CHXA" as in [13]. The conjugate-antibody ratio (CAR) of CHXA" molecules per IF3 molecule post-conjugation was determined by MALDI-TOF (University of Alberta, Edmonton, Canada) to be 0.91.…”

“…The conjugate-antibody ratio (CAR) of CHXA" molecules per IF3 molecule post-conjugation was determined by MALDI-TOF (University of Alberta, Edmonton, Canada) to be 0.91. Radiolabeling with 111 In and 177 Lu was performed as in [13]. Radiolabeling yields were typically greater than 98%, and radiolabeled mAbs required no further purification.…”

“…Impressively, this effect of the RIT on the tumors in comparison with multiple control groups was achieved using a single administration and non-optimized dosing [11,12]. As modern requirements for biological drugs require the mAbs to be humanized or fully human, we have recently developed a fully human mAb IF3, which binds with high specificity and affinity to human, canine and murine IGF2R, and evaluated it in vitro and in vivo for binding to commercial OS cell lines and human and canine-patient-derived tumors [13]. In this work, we evaluated the efficacy and safety of radioimmunotherapy with the 177 Lu-labeled IF3 of mice bearing canine-patient-derived tumors and performed canine and human dosimetry calculations.…”

Radionuclides in Diagnostics and Therapy of Malignant Tumors: New Development

“…Broqueza and co-workers [ 12 ] reported the development and initial characterization of human antibodies that bind to the insulin-like growth factor-2 receptor (IGF2R) overexpressed in osteosarcomas (OS). A phage-display library was used to generate three Fab fragments, which had low nanomolar affinities to the IGF2R of human, canine, and murine origin.…”