Initial insights into the interaction of antibodies radiolabeled with Lutetium-177 and Actinium-225 with tumor microenvironment in experimental human and canine osteosarcoma.

BACKGROUND: Osteosarcoma (OS) is a prevalent primary bone cancer affecting both humans and canines. This study describes initial insights into the interaction of the human monoclonal antibody IF3 to an insulin-like growth factor 2 receptor (IGF2R) radiolabeled with either alpha-emitting Actinium-225 (225Ac) or beta-emitting Lutetium-177 (177Lu) radionuclides with the OS cells and tumor microenvironment (TME) in experimental human and canine OS. BASIC PROCEDURES: SCID mice bearing canine Gracie or human OS-33 OS tumors were treated with 177Lu- or 225Ac-labeled IF3 antibody, sacrificed at 24, 72 or 168 h post-treatment and their tumors were analyzed by immunohistochemistry (IHC) for the presence of OS cells, various elements of TME as well as for the double DNA strand breaks with γH2AX and caspase 3 assays. MAIN FINDINGS: IHC revealed a reduction in IGF2R-positive OS cells and OS stem cell populations post therapy with 225Ac- and 177Lu-labeled IF3 antibody. Notably, radiolabeled IF3 antibody effectively diminished pro-tumorigenic M2 macrophages, highlighting its therapeutic promise. The study also unveiled varied responses of natural killer (NK) cells and M1 macrophages, shedding light on the intricate TME interplay. Time-dependent increase in γ-H2AX staining in canine Gracie and human OS-33 tumors treated with [177Lu]Lu-IF3 and [225Ac]Ac-IF3 was observed at 24 and 72 h post-RIT. PRINCIPAL CONCLUSIONS: These findings suggest that radiolabeled antibodies offer a hopeful avenue for personalized OS treatment, emphasizing the importance of understanding their impact on the TME and potential synergies with immunotherapy.

Comparative Molecular Characterization and Pharmacokinetics of IgG1-Fc and Engineered Fc Human Antibody Variants to Insulin-like Growth Factor 2 Receptor (IGF2R).

Novel therapeutic approaches are much needed for the treatment of osteosarcoma. Targeted radionuclide therapy (TRT) and radioimmunotherapy (RIT) are promising approaches that deliver therapeutic radiation precisely to the tumor site. We have previously developed a fully human antibody, named IF3, that binds to insulin-like growth factor 2 receptor (IGF2R). IF3 was used in TRT to effectively inhibit tumor growth in osteosarcoma preclinical models. However, IF3's relatively short half-life in mice raised the need for improvement. We generated an Fc-engineered version of IF3, termed IF3δ, with amino acid substitutions known to enhance antibody half-life in human serum. In this study, we confirmed the specific binding of IF3δ to IGF2R with nanomolar affinity, similar to wild-type IF3. Additionally, IF3δ demonstrated binding to human and mouse neonatal Fc receptors (FcRn), indicating the potential for FcRn-mediated endocytosis and recycling. Biodistribution studies in mice showed a higher accumulation of IF3δ in the spleen and bone than wild-type IF3, likely attributed to abnormal spleen expression of IGF2R in mice. Therefore, the pharmacokinetics data from mouse xenograft models may not precisely reflect their behavior in canine and human patients. However, the findings suggest both IF3 and IF3δ as promising options for the RIT of osteosarcoma.

Characterization of IGF2R Molecular Expression in Canine Osteosarcoma as Part of a Novel Comparative Oncology Approach.

Progress in prognostic factors, treatments, and outcome for both canine and human osteosarcoma (OS) has been minimal over the last three decades. Surface overexpression of the cation independent mannose-6-phosphate/insulin-like growth factor receptor type 2 (IGF2R) has been proven to occur in human OS cells. Subsequently, radioimmunotherapy (RIT) targeting IGF2R has demonstrated promising preliminary results. The main aims of this study were to investigate the expression of IGF2R in spontaneously occurring canine OS cells using immunohistochemistry (IHC) on archived biopsy samples and to assess its prognostic significance. Thirty-four dogs were included in the study. All cases showed that 80-100% of OS cells stained positive for IGF2R. IGF2R overexpression alone was not shown to have prognostic significance using both visual and quantitative methods of IHC staining intensity. This study has established for the first time the consistent expression of IGF2R in spontaneously occurring canine OS. This comparative oncology approach will allow further investigation into RIT as a novel treatment modality; first in canines and then in humans with OS. In addition, further studies should be performed to assess the true prognostic significance of IGF2R overexpression.

Design and development of 1,3,5-triazine-thiadiazole hybrids as potent adenosine A2A receptor (A2AR) antagonist for benefit in Parkinson's disease.

Various studies showed adenosine A2A receptors (A2ARs) antagonists have profound therapeutic efficacy in Parkinsons Disease (PD) by improving dopamine transmission, thus being active in reversing motor deficits and extrapyramidal symptoms related to the disease. Therefore, in the presents study, we have showed the development of novel 1,3,5-triazine-thiadiazole derivative as potent A2ARs antagonist. In the radioligand binding assay, these molecules showed excellent binding affinity with A2AR compared to A1R, with significant selectivity. Results suggest, compound 7e as most potent antagonist of A2AR among the tested series. In docking analysis with A2AR protein model, compound 7e found to be deeply buried into the cavity of receptor lined via making numerous interatomic contacts with His264, Tyr271, His278, Glu169, Ala63, Val84, Ile274, Met270, Phe169. Collectively, our study demonstrated 1,3,5-triazine-thiadiazole hybrid as a highly effective scaffold for the design of new A2A antagonists.