An expanded access record providing Tralesinidase alfa (TA) in Mucopolysaccharidosis Type IIIB and MPS IIIB (Sanfilippo B Syndrome), sponsored by Spruce Biosciences. Available at 1 site in United States. Open to participants aged 12 Months and older. Per ClinicalTrials.gov, last updated 2026-10-06.
Sponsored by Spruce Biosciences · Expanded access
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.
MPS IIIB (Sanfilippo Syndrome Type B) is an ultra-rare, autosomal recessive lysosomal storage disease caused by deficiency of alpha-N-acetylglucosaminidase (NAGLU). In the absence of NAGLU activity, heparan sulfate (HS) and its metabolite HS non-reducing end (HS-NRE) accumulate in lysosomes, causing progressive CNS neurodegeneration. Affected children experience developmental delays beginning between ages 1 and 4, followed by cognitive regression and loss of motor function, with death typically occurring in the second decade of life.
Tralesinidase alfa (TA) is a recombinant human NAGLU-IGF2 fusion protein administered directly into the CNS via ICV infusion. In Study 250-201 and its extension studies, weekly ICV TA normalized or near-normalized CSF HS-NRE levels in all participants within 4 weeks, with effects maintained for up to 5 years. TA treatment was associated with long-term stabilization of cortical gray matter volume and prevention of age-dependent cognitive decline.
Study 250-502 is an intermediate-size EAP under 21 CFR 312.315, intended for participants who are older than 5 years of age or have a BSID-III-C raw score ≥70. The program will continue until TA receives US regulatory approval and commercial availability, or until the allocated TA supply is exhausted.
Participants receive TA (200 mg if age 1 to \<2 years; 300 mg if age ≥2 years) administered via ICV infusion once weekly after surgical implantation of an ICV access device (reservoir and catheter). The first ICV infusion is administered in an inpatient setting; subsequent infusions are done in an outpatient setting. Participants are pretreated with antihistamine approximately 30 minutes before each infusion.
58 studies on the registry are indexed under Mucopolysaccharidosis III; 16 are open to participants now.
Browse Mucopolysaccharidosis III studies →Spruce Biosciences is the lead sponsor of 8 studies on the registry; 2 are open to participants now.
Of its 6 completed or terminated interventional studies of FDA-regulated products, 6 (100%) have results posted.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
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 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 , agrees to follow 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 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 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.
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Tralesinidase alfa (TA) is a sterile solution of recombinant human alpha-N-acetylglucosaminidase fused with insulin-like growth factor 2 (rhNAGLU-IGF2), formulated at 30 mg/mL for ICV infusion. Dose: 200 mg (6.7 mL) for participants age ≥12 to \<24 months; 300 mg (10 mL) for participants age ≥24 months. Administered once weekly via ICV reservoir following isovolumetric removal of up to 10 mL CSF, infused over approximately 10 minutes. Stored frozen at -40°C (±10°C).
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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