Abstract 2815: Immunotherapy development landscape for bone metastasis - need of predictive preclinical efficacy evaluation for de-risking clinical development
Authors: Kähkönen Tiina E. , Halleen Jussi M. , MacRitchie Gary , Andersson Ronnie M. , Bernoulli Jenni 
Published: March 2024

Abstract
Most cancer deaths are due to metastases, and bone metastases are challenge especially in breast and prostate cancer, being developed in 70-90% of advanced-stage patients. Bone metastases remain incurable causing high mortality, skeletal-related effects and decreased quality of life. Currently used immunotherapies are ineffective in bone metastases. This creates a need to improve understanding immune microenvironment in bone metastases, namely interactions between tumor, immune and bone cells according to the osteoimmuno-oncology (OIO) concept, and ultimately to develop immunotherapies that primarily target bone metastases.
We used 1stOncology database, a cancer drug development resource to identify novel immunotherapies in development for breast and prostate cancer bone metastasis. Twenty-four immunotherapies that included evaluation of effects on bone metastasis were identified. Efficacy of only three of the identified therapies had been evaluated in preclinical bone metastasis models, one reason being that such models have not been commonly available. The use of clinically relevant and predictive preclinical bone metastasis models would significantly de-risk decision making when moving to clinical development in bone metastasizing cancers.
To support predictive preclinical evaluation of immunotherapies for bone metastatic cancers, we describe a preclinical bone metastasis technology platform for evaluating efficacy of immunotherapies. The platform utilizes tumors growing in bone microenvironment, mimicking growth of bone metastases in patients, and generates tumor-induced bone effects in a cancer-type specific manner. Syngeneic and/or humanized mouse models with tumor and immune cells of the same species are needed for development of immunotherapies, allowing interactions of tumor and immune cells in the bone metastatic microenvironment to support mode-of-action studies. The platform is clinically predictive, as demonstrated with observed effects that align with clinical findings. As an example, anti-PD-1 antibody had no effects on breast and prostate cancer bone metastases, predicting recent clinical findings that demonstrate lack of efficacy in clinical prostate cancer trials.
We conclude that tumor microenvironment in bone metastases has unique characteristics and is understudied as a potential primary cause of lack of efficacy of many immunotherapies, especially in breast and prostate cancer. It is prime time to focus on bone metastases by increasing understanding of the immune landscape in the bone tumor microenvironment according to the OIO concept. The biologically relevant and clinically predictive preclinical bone metastasis technology platform should be routinely used to study the mechanism-of-action and efficacy of therapies before entering clinical development in bone metastasizing cancers.
Citation Format: Tiina E. Kähkönen, Jussi M. Halleen, Gary MacRitchie, Ronnie M. Andersson, Jenni Bernoulli. Immunotherapy development landscape for bone metastasis - need of predictive preclinical efficacy evaluation for de-risking clinical development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2815.