A Study to Learn About the Safety and Effects of the Study Drug PRX-102 in Children and Adolescents With Fabry Disease

Inclusion Criteria:

• Participants with the provision of informed consent from their legal guardians

• Boys and girls aged 2 to 7 years (Cohort A), 8 to 12 years (Cohort B), or 13 to <18years (Cohort C).

• Confirmed diagnosis of Fabry disease

• Presence of at least one of the following characteristic features of Fabry disease:neuropathic pain, cornea verticillata, and/or clustered angiokeratoma.

• History of Fabry pain: Fabry crises OR chronic pain.

• Clinical condition that, in the investigator's opinion, requires ERT treatment.

Exclusion Criteria:

All Subjects:

• Estimated glomerular filtration rate (eGFR) at screening < 80 mL/min/1.73 m2.

• History of type I hypersensitivity reactions (anaphylactic or anaphylactoidlife-threatening reaction) to other ERT treatment for Fabry disease or any componentof the study drug.

• Initiation of treatment with an angiotensin-converting enzyme inhibitor (ACEi) orangiotensin II receptor blocker (ARB) or a dose change in ongoing treatment in thefour weeks before screening.

• Urine protein to creatinine ratio (UPCR) > 0.5 g/g (0.5 mg/mg or 500 mg/g) if nottreated with an ACE inhibitor or ARB.

• Currently taking another investigational drug for any condition.

• History of acute kidney injury in the 12 months before screening, including specifickidney diseases (e.g., acute interstitial nephritis, acute glomerular and vasculiticrenal diseases); non-specific conditions (e.g., ischaemia, toxic injury); orextrarenal pathology (e.g., prerenal azotaemia, acute postrenal obstructivenephropathy).

• History of renal dialysis or kidney transplantation.

• History of or current malignancy requiring treatment.

• Severe cardiomyopathy or significant unstable cardiac disease within six monthsbefore screening.

• A positive test for Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-CoV-2)within three months before screening.

• Presence of any medical, emotional, behavioural, or psychological condition that, inthe Investigator's judgement, could interfere with the subject's compliance with therequirements of the study.

Additional Exclusion Criteria for Subjects Enrolled in Stage I:

• Female

• Non-classic form of Fabry disease

• Receipt of treatment for Fabry disease within six months before screening

• Positive for anti-PRX-102 antibodies at screening

Additional Exclusion Criteria for Subjects in Stage II (i.e., non-treatment naïve males or females):

• Unwilling to discontinue current ERT treatment for Fabry disease before baseline.

• Females: Pregnant or lactating, or of childbearing potential with a fertile malepartner and unwilling to use a highly reliable method of contraception from theinformed consent signature until 30 days after the last infusion.