Page last updated: October 7, 2026
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Clinical Trial Summary
This is an intermediate-size patient population Early Access Program (EAP) providing access to intracerebroventricular (ICV) tralesinidase alfa (TA) for participants with mucopolysaccharidosis type IIIB (MPS IIIB, Sanfilippo Syndrome Type B). The primary objectives are to allow early access to TA treatment and to evaluate the safety and tolerability of TA ICV infusion. Approximately 10 participants will be enrolled at up to 3 US sites and treated with TA once weekly via ICV infusion for up to approximately 52 weeks, or until TA becomes commercially available.
Note: This is unique from Spruce’s TrAnsform clinical research study regarding TA-ERT from Sanfilippo Type B. Learn more about the TrAnsform clinical trial.
Trial Information
Route of administration: intracerebroventricular (ICV) into the fluid space of the brain
Frequency of administration: Infusion once weekly
Anticipated number of participants: Approximately 10
Anticipated number of clinical locations: Up to 3 in the USA
Length of program: up to 52 weeks or until commercially available if drug is approved or until supply is exhausted
Study Contact: April Freeman, (415) 343-5986, EA@sprucebio.com
Clinical site: Children’s Hospital Oakland Research Institution
Contact: Erin O’Neil
Contact email: erin.oneil@ucsf.edu
Study Information: MPS3BStudy.com. The website provides information about TA-ERT, the planned Expanded Access Program and the TrAnsform confirmatory study. Families can also register their interest at the MPS3BStudy.com website to receive updates as sites activate and enrollment begins.
Listing on ClinicalTrials.gov: Read this clinical trial’s information on ClinicalTrials.gov, for more details including contact information to reach out to the study sites, full inclusion and exclusion criteria. We encourage you to check the Clinicaltrials.gov link frequently for updates on possible new study sites and changes in enrollment status or criteria.
Inclusion Criteria:
- Has a diagnosis of MPS IIIB confirmed by deficient NAGLU enzyme activity analyzed at the laboratory during Screening.
- Is ≥12 and ≤60 months of age with a BSID-III-C raw score ≥70. or Is >60 months of age regardless of cognitive level. Has provided written informed consent from a parent or legal guardian Has been determined by the investigator, after consultation with the participant (if applicable) and their family/caregiver, that the known risks of TA ICV infusion are outweighed by its potential benefits.
- If female and of childbearing potential, agrees to follow contraception guidelines from screening until 30 days after the last dose of TA.
- Has the ability to comply with program requirements, in the opinion of the investigator.
Exclusion Criteria:
- Has contraindications for neurosurgery (e.g., congenital heart disease, severe respiratory impairment, or clotting abnormalities).
- Has contraindications for MRI scans, if the investigator deems an MRI and not a CT scan is required for ICV access device placement or follow-up post-placement.
- Has a history of poorly controlled seizure disorder. Is prone to complications from ICV infusion, including participants with hydrocephalus or ventricular shunts.
- Has received any investigational medication within 30 days prior to the Baseline Visit or is scheduled to receive any investigational drug during the course of the program.
- Has a medical condition or extenuating circumstance that, in the opinion of the investigator, might compromise the participant’s ability to comply with program requirements, the participant’s well-being or safety, or the interpretability of the participant’s clinical data.
Trial Updates
September 2026
Spruce announces the launch of MPS3BStudy.com, a single website where families and caregivers can learn about the planned EAP and TrAnsform confirmatory study and also register interest in both. Additionally, in the letter, Szwarcberg states, “Spruce expects to initiate both the EAP and the TrAnsform confirmatory study as early as the fourth quarter of 2026.” Read the complete letter.
August 2026
Spruce Biosciences formally announced that Cure Sanfilippo Foundation and the National MPS Society have agreed to make a combined $5.5 million strategic investment in Spruce. The proceeds will be used to partially fund TA-ERT EAP, helping to broaden patient access to investigational TA-ERT for the treatment of Sanfilippo Syndrome Type B. Additionally, in its press release, Spruce noted, “Spruce expects to initiate TA-ERT EAP as early as the fourth quarter of 2026.” Read the complete statement.
Cure Sanfilippo Foundation is proud to have provided $4.785M and coordination support to the multi-function team to enable earliest access possible for children to this treatment.
July 2026
Spruce shared results from previous clinical trial of normalization or near normalization of spinal fluid heparan sulfate levels (CSF HS-NRE). Treatment associated with long-term stabilization of brain tissue volume and age-dependent cognitive decline.
May 2026
Spruce CEO Javier Szwarcberg shared a letter with the Sanfilippo Syndrome Type B community about recent progress of our TA-ERT program. He highlighted our ongoing regulatory progress, the latest encouraging clinical data from our clinical program and outlined our plans for both a U.S. expanded access program and global confirmatory study. Read more.
December 2025
The opportunity arose in October to support the creation of a Sanfilippo Type B enzyme replacement drug for future use under an Expanded Access Program. Parents and families of children with Type B, communities, and others came together and rallied to fundraise through Cure Sanfilippo Foundation and MPS Society to reach this goal in this short window. The $5.5M needed for this treatment opportunity to become a reality was successfully raised. Read more.
October 2025
The Sanfilippo community has been presented with an opportunity to have an Expanded Access enzyme replacement treatment for some children with Sanfilippo Type B. Read more.