HbS oligomers as a therapeutic target in sickle cell disease

The molecular origin of sickle cell disease (SCD) has been known since 1949. Despite this, the treatment options for afflicted individuals remain limited to a few therapies that have widely variable and/or limited efficacy. The dearth of therapies stems, at least in part, from a dearth of high throughput assays with which to identify molecules that can inhibit sickle hemoglobin (HbS) polymerization. Here, we propose a BOLD BIOENGINEERING approach to drug discovery in sickle cell using time resolved FRET detection of HbS oligomers at sub-nucleating concentrations, which is sensitive to compounds that inhibit HbS interactions and is compatible with high throughput screening (HTS). We have recently developed a novel, time-resolved (TR- FRET) assay that allows direct detection of HbS oligomers and that is compatible with HTS. Thus, for the first time, we have the tools to screen for compounds that inhibit HbS nucleation and polymerization. Moreover, this assay is capable of identifying compounds that disrupt oligomer formation via direct competition with the primary binding site or by allosterically modifying the HbS confirmation. In a pilot screen of a small library (one thousand compounds) we have, for the first time, discovered lead compounds that eliminate HbS oligomers and rescue whole blood from the sickle pathology. Thus, we are now in a position to perform a large-scale campaign to discover and characterize lead compounds with the potential to transform the translation landscape of SCD. In the proposed project, we will: (1) use TR-FRET to discover new small molecules that inhibit in vitro HbS nucleation and (2) determine which subset of hit compounds are able to inhibit HbS polymerization in whole blood under physiologic conditions. This work will serve as a proof of concept HTS discovery compaign that will revolutionary for the field of SCD and will reveal new mechanisms for disrupting HbS polymerization that could transform the landscape for therapy. Additionally, in the course of this work, we will discover and validate new candidate small molecules that can inhibit HbS nucleation and polymerization under physiologic conditions and may lead to desperately needed new clinical therapies for this terrible disease.