Inclusion Criteria:  Individuals  Have provided informed consents (TCH and NIH) by subject or parent/legal guardian/legally authorized representative (as appropriate). Are males or females ≥ 17 years of age at the time of screening  Have genetically confirmed diagnosis of syndromic CLN3 disease with  EITHER:  A. Two pathogenic mutations in the CLN3 gene, OR B. One confirmed pathogenic AND one variant of unknown significance, OR 2 variants of unknown significance, PLUS secondary confirmation with evidence of characteristic inclusions on electron microscopy AND characteristic clinical course. There is no restriction on the specific CLN3 mutations for eligibility to enroll in the study. The mutations will be recorded in the electronic case report form (eCRF) for potential use in determining if CLN3 genotype is associated with tolerability and/or effectiveness of BBDF-101 therapy.  Male and female participants must use a highly effective method of contraception and must continue for the duration of the trial (and for 30 days after the end of treatment). Are able to complete study assessments (subject or caregiver) and return to the clinic as scheduled  Exclusion criteria  Individuals  Have a medical condition that in the opinion of the PI would interfere with the safety assessments or increase the subject's risk of AEs Have a diagnosis ( HbA1c level > 7%) or are treated for Type 1 or Type 2 diabetes mellitus Have, in the opinion of the PI, a clinically significant abnormality in their clinical laboratory values (hematology, chemistry, or urinalysis) at screening that would preclude their participation in the study