Cure Sanfilippo Foundation and the National MPS Society have agreed a combined $5.5 million strategic investment in Spruce Biosciences, which will go towards the Tralesinidase Alfa Enzyme Replacement Therapy (TA-ERT) for Sanfilippo Syndrome Type B (or MPS IIIB) Expanded Access Program (EAP). 

Samir Gharib, President and Chief Financial Officer of Spruce Biosciences, commented: “This investment is a powerful expression of what we can accomplish when industry and the patient community work together. Their support helps us expand access to investigational TA-ERT for children with MPS IIIB who urgently need treatment options today, while we continue our work to bring this therapy to all eligible patients.” 

MPS IIIB is a rapidly progressing neurodegenerative disease that primarily affects children and for which there are no FDA-approved therapies. 

TA-ERT is a fusion protein comprised of recombinant human alpha-N-acetylglucosaminidase (rhNAGLU), intended as an enzyme replacement therapy for the treatment of patients with MPS IIIB who lack rhNAGLU enzyme activity.  

TA-ERT is anticipated to restore rhNAGLU enzyme activity in the central nervous system following intracerebroventricular injection. rhNAGLU typically lacks the mannose-6 phosphate (M6P) residues that are essential for efficient cellular uptake via the M6P receptor pathway. As a result, the naked enzyme is poorly absorbed by cells, including neurons.  

To address this challenge, TA-ERT is fused to an insulin-like growth factor 2 peptide, which binds to the cation-independent M6P on cell surfaces. This fusion enables the enzyme to be internalized and delivered to the lysosome, thereby enhancing its therapeutic potential for treating MPS IIIB.  

By restoring NAGLU enzymatic activity and promoting clearance of lysosomal heparan sulfate and heparan sulfate non-reducing end in the brain, TA-ERT therapy is expected to preserve neuronal cell health and potentially halt or slow the neurological decline and improve clinical outcomes in affected patients.