Abstract A007: Preclinical bone metastasis technology platform – Predictive evaluation of experimental therapies on bone metastasis
Authors: Kähkönen Tiina E , Halleen Jussi M , Bernoulli Jenni 
Published: December 2023

Abstract
Most cancer deaths are due to metastases, and bone metastases are a considerable problem especially in breast and prostate cancer, being developed in 70-90% of advanced-stage patients. Despite major investments in oncology drug development, bone metastases are currently incurable and a high unmet medical need with only 5% of patients being alive 5 years after the diagnosis. Development of therapies for bone metastasis has been challenging due to lack of appropriate preclinical models available to support decision making in next phases of drug development. In the absence of clinically relevant preclinical bone metastasis models, the current strategy is to rely on preclinical efficacy data obtained with subcutaneous models that lack the clinically relevant local tissue microenvironment, which has a major impact on tumor growth. The use of clinically non-relevant models in preclinical-stage development may be one important reason for the current &gt;95% failure rate of oncology drugs in clinical trials. To support predictive evaluation of therapies for bone metastatic cancers, we describe a preclinical bone metastasis technology platform for evaluating efficacy of novel therapies on bone metastases. The platform utilizes tumors growing in bone microenvironment, mimicking growth of bone metastases in patients. Syngeneic or humanized mouse models with tumor and immune cells of same species are needed for supporting development of immunotherapies, allowing interactions of tumor and immune cells in the bone metastatic microenvironment, according to the novel osteoimmuno-oncology concept. The platform provides a predictive tool for studying unique biological features associated with different types of bone metastases in cancer-type specific manner. Here we summarize case examples where results from preclinical bone metastasis studies align with clinical findings of different therapies approved or evaluated for bone metastasis. Zoledronic acid, an anti-resorptive bisphosphonate that is currently used in breast cancer patients with bone metastases to prevent cancer-induced bone loss, showed improved bone health but no effects on tumor growth. Radium-223 dichloride, an approved treatment for bone metastatic castration-resistant prostate cancer in patients, showed reduced prostate cancer growth and decreased tumor-induced bone changes. As for immunotherapies, an IDO1 inhibitor had no effects on breast cancer bone metastases and the anti-PD-1 antibody pembrolizumab had no effects on breast and prostate cancer bone metastases, predicting recent clinical findings that demonstrate lack of efficacy of anti-PD-1 in clinical prostate cancer trials. We conclude that the bone metastasis technology platform is a biologically relevant tool for preclinical evaluation of the efficacy of experimental therapies on bone metastasis, and it has been validated with positive and negative case examples, demonstrating its clinically predictive power.
Citation Format: Tiina E Kähkönen, Jussi M Halleen, Jenni Bernoulli. Preclinical bone metastasis technology platform – Predictive evaluation of experimental therapies on bone metastasis [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A007.