Inclusion Criteria:

• Subject must have completed protocol AVTX-803-LAD-301.
• Subject must be between 6 months and 75 years old.
• Subject or parent (for subjects under legal age for consent) has provided written informed consent for this study. Additionally, written informed assent has been provided, as appropriate, for minors of older age, per local institutional review board (IRB)/ethics committee (EC) policy and requirements.
• Subject has biochemically and genetically proven LAD II (SLC35C1-CDG).
• Subject is willing and able to comply with the protocol.
• Women of childbearing potential (WOCBP) meeting the criteria below:
  • Non-lactating and has a negative pregnancy test at screening; AND
  • Uses an acceptable double-barrier method of contraception as determined by the investigator or sub-investigator for the duration of the study and 30 days following the last dose of study drug.
• Male subjects must agree to use an acceptable double-barrier method of contraception with their partner as determined by the investigator or sub-investigator for the duration of the study and 30 days following the last dose of study drug.  

Exclusion Criteria: 

• Subject has severe anemia defined as hemoglobin < 8.0 g/dL (< 4.9 mmol/L).
• Subject has impaired renal function as defined by an eGFR < 90 mL/min.
• Subject has known or suspected intolerance or hypersensitivity to fucose or any ingredients of the investigational product.
• In the investigator’s opinion, subject has a history of failure to respond to fucose at adequate dosing.
• In the investigator’s opinion, subject is not able or not willing to comply with the study requirements.
• Subject is pregnant.

Eligibility last updated 7/13/22. Questions regarding updates should be directed to the study team contact.