This is a prospective multicenter, open-label, dose-escalation trial to assess the safety, tolerability, and pharmacodynamics of 4D-310 following a single IV administration. The study population is comprised of adult males and females with Fabry Disease.

This is a prospective multicenter, open-label, dose-escalation trial to assess the safety, tolerability, and pharmacodynamics of 4D-310 following a single IV administration. The study population is comprised of adult males and females with Fabry Disease.

Inclusion Criteria:

1. Male or female ≥ 18 years of age
2. Pathogenic GLA mutation consistent with Fabry Disease
3. Confirmed diagnosis of classic or late-onset Fabry disease
4. Individuals on ERT must be on a stable dose for at least 6 months (and a minimum of 12 months total exposure) prior to study enrollment
5. Agree to use highly effective contraception

Exclusion Criteria:

1. Presence of high titer neutralizing antibody to 4D-310 capsid, or presence of high antibody titer to AGA
2. eGFR <45 mL/min/1.73 m2
3. Undergone kidney transplantation or currently on hemodialysis or peritoneal dialysis
4. HIV, active or chronic hepatitis B or C,
5. Evidence of liver disease, severe pulmonary disease or diabetes with poor glycemic control
6. History of stroke or transient ischemic attack within the last 12 months, or other significant thromboembolic disease history (e.g. pulmonary embolism)
7. Contraindication to systemic corticosteroid therapy or immunosuppressive therapy
8. Chronic steroid use, defined as ≥ 3 months of oral corticosteroid use within the last 12 months.
9. Moderately severe to severe cardiovascular disease or uncontrolled hypertension
10. Left ventricular ejection fraction of <45% on echocardiogram (ECHO)
11. Currently receiving investigational drug, device or therapy or having ever received gene therapy
12. History of infusion related response to ERT or any adverse reaction leading to ERT discontinuation
13. History of cancer within 2 years (exceptions include non-melanoma skin cancer, localized prostate cancer treated with curative intent)
14. Pregnant or breast-feeding