Discovery and validation of single cell biomarkers for clinical outcome in sickle cell disease

University Of Minnesota, Minneapolis MN

Investigators

Abstract

PROJECT SUMMARY There is an urgent and unmet need for pathophysiologically relevant, clinically validated biomarkers for SCD. We know from numerous studies and decades of experience that the lack of validated biomarkers for SCD severity results in suboptimal care and a lack of objective outcome metrics for clinical research. Even as therapeutic development is rapidly advancing, the lack of robust quantitative biomarkers also severely impedes optimization of proposed treatments, prioritization of distinct treatment modalities, as well as assessment, approval, implementation, and comparison of candidate treatments. We have known for more than a century that polymerization of sickle hemoglobin (HbS) and subsequent RBC biomechanical change is the fundamental pathologic event in SCD. Despite the dominant role of HbS polymerization in disease pathology and treatment mechanisms of action, there are no clinically validated assays to measure single RBC HbS polymerization and stiffness increases that drive the disease. Our team developed the first assay to quantify the distribution of HbS polymer among a population of RBC over the physiologic range of oxygen concentration. Moreover, we recently demonstrated the clinical utility of these measurements to distinguish patients who received gene therapy in a clinical trial from those receiving standard of care hydroxyurea even when the two groups have similar levels of fetal hemoglobin (HbF). To further the potential sensitivity of these measurements, we recently demonstrated that we could combine high throughput measurement of single cell HbS polymer content with high throughput measurements of single cell mechanical properties. Thus, we have developed a platform capable of characterizing blood samples based on the key mechanisms that drive the downstream pathologies in the disease. We hypothesize that this combination of RBC biochemical and biophysical properties could serve as a more robust clinical predictor of adverse outcomes than existing measurements. In the proposed studies, we will (1) Define the relationship between common SCD adverse clinical outcomes and single cell biochemical and mechanical properties to identify the most promising biomarkers; (2) Define the relationship between favorable and unfavorable response to SCD treatments and single cell biochemical and mechanical properties to identify the most promising biomarkers; (3) Develop a platform to measure kinetic changes in single RBC properties during deoxygenation and identify kinetic metrics that correlate with clinical outcomes in SCD. With a set of validated biomarkers we can proactively predict odds of an adverse event from steady state values obtained in clinic and monitor response to a new therapy in a rapid, objective and quantitative manner.