Rhonwyn Waterson: “A drug repurposing pipeline to find treatments for SLC6A8/CRT-1 (creatine transporter) deficiency”
ABSTRACT
Rationale: There is currently no treatment for SLC6A8/CRT-1 related intellectual disability. We have established a 3- tier pipeline to find repurpose-able drugs for this condition.
Methods:
Tier 1: In silico drug screening using a library of FDA approved drugs to identify drugs that would bind to the high-resolution 3D structure of SLC6A8/CRT-1 protein.
Tier 2: In vitro testing of candidate drugs for their ability to rescue mutant SLC6A8/CRT-1 activity using electrophysiological patch clamp technique and measuring changes in transmembrane sodium gradient in SLC6A8 variant transfected HEK293 cells.
Tier 3: To further validate tier 2 results, creatine uptake studies are performed in SLC6A8 deficient human fibroblasts measuring cellular uptake of D3 labelled creatine (D3-creatine) and its intracellular conversion to phosphocreatine (D3-PCr). Guanidino-propionate (GPA), a competitive inhibitor of SLC6A8-mediated creatine uptake is used to confirm SLC6A8 specificity of the measured uptake rates.
Results: Using Tier 1 and 2 we have identified 12 candidate drugs / compounds which partially rescue deficient SLC6A8 activity in transfected HEK293 cells. 6/12 compounds can potentially be used for off label prescription in n-of-1 studies. 5/6 are effective in variant Phe408del and Asn336del. One compound (4PBA) showed efficacy in several SLC6A8/CRT-1 missense mutations. We have created data for time and dose dependent D3-creatine uptake in wild type and Phe408del fibroblasts informing experimental protocols for further drug testing. Work in progress: To test D3-creatine uptake in Phe408del fibroblasts (purchased from the Coriell Biobank) and in Asn336del fibroblasts (once available) in response to 5 repurpose-able drugs identified in tier 2.
Acknowledgement: Our research is generously supported by the ACD.