Study to Evaluate the Safety, PK, PD, and Efficacy of PRX-102 in Japanese Patients With Fabry Disease

Inclusion criteria (all subjects)

1. Must have been born in Japan and have their biological parents and all 4grandparents of Japanese descent

2. A documented diagnosis of Fabry disease, as determined by the following:

• Males: Plasma and/or leukocyte alpha-galactosidase-A activity (by activityassay) that is ≤ 5% of mean normal laboratory levels or, if the enzymaticactivity is above the 5% limit but still under the normal level, a confirmeddisease-causing mutation of the GLA gene

• Females: Historical genetic test results consistent with Fabry mutations or, inthe case of novel mutations, a first-degree male relative with Fabry disease

• All subjects: At least one of the following characteristic features of Fabrydisease: neuropathic pain, cornea verticillata, and/or clustered angiokeratoma

3. Estimated glomerular filtration rate (eGFR) at screening ≥40 mL/min/1.73 m2. Foradults, this will be calculated using the Japanese Modified Chronic Kidney DiseaseEpidemiology Collaboration (JPN-CKD-EPI) Creatinine equation (2009); and foradolescents, it will be calculated using the Creatinine Cystatin C-based ChronicKidney Disease in Children (CKiD) equation.

4. Clinical condition that in the opinion of the Investigator requires treatment withERT

5. A female subject (including an adolescent in Cohort C, if applicable) must meet oneof the following criteria:

• If of childbearing potential, she must:

• Have a negative serum pregnancy test result at screening, AND

• Agree to undergo a urine pregnancy test at baseline and every 12 weeksthereafter up to the final treatment, AND

• Agree to use one of the following highly reliable methods of contraceptionfrom the day of the informed consent signature until 30 days after thelast infusion received. The following methods are acceptable:

• Placement of an intrauterine device (IUD) or intrauterine system (IUS)

• Combined (both oestrogen and progestogen) hormonal contraception (oral) associated with inhibition of ovulation, supplemented with abarrier method (preferably male condom)

• Bilateral tubal occlusion

• Sexual abstinence, defined as refraining from heterosexualintercourse during the entire study period

• Partner vasectomy, provided that the partner is the sole sexualpartner and has received medical verification of the surgical success

• Be of non-childbearing potential, defined as one of the following:

• Post-menopausal (12 consecutive months of amenorrhea), OR

• Permanently sterile following hysterectomy, bilateral salpingectomy, orbilateral oophorectomy (supporting evidence required)

Additional inclusion criteria for subjects in Cohort A

For subjects enrolled in Cohort A, these specific inclusion criteria, in addition to those above, apply:

• Aged ≥18 to ≤70 years

• Treatment with agalsidase beta or agalsidase alfa for at least the last 12 monthsprior to screening, with the dose stable (defined as having received at least 80% ofthe labelled dose) for at least the last 6 months

• Diagnosis of kidney impairment, defined as a linear slope of eGFR more negative thanor equal to -2 mL/min/1.73 m2/year. The historical eGFR slope will be calculatedbased on at least 3 serum creatinine values obtained over the 9 to 24 months priorto screening, using the JPN-CKD-EPI Creatinine equation (2009). This criterion willbe confirmed at screening by calculating the screening eGFR slope using historicaland screening serum creatinine values. Both historical and screening eGFR slopeswill be used for the diagnosis of kidney impairment.

Additional inclusion criterion for subjects in Cohort B

For subjects enrolled in Cohort B, this specific inclusion criterion, in addition to those above, applies:

• Aged ≥18 to ≤70 years

Additional inclusion criteria for subjects in Cohort C

For subjects enrolled in Cohort C, these specific inclusion criteria, in addition to those above, apply:

• Aged ≥13 to <18 years

• Subjects who have previously received or are currently receiving ERT treatment, mustbe negative for ADAs to PRX-102

Exclusion Criteria:

1. Administration of ERT for Fabry disease within 14 days before baseline, substratereduction therapy for Fabry disease within 3 days before baseline, or chaperonetherapy for Fabry disease within 3 days before baseline

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

3. Cohort A only: eGFR value of >90 to ≤120 mL/min/1.73 m2 at screening and ahistorical eGFR value >120 mL/min/1.73 m2 in the 9 to 24 months before screening,indicating absence of renal impairment. eGFR to be calculated using the JPN-CKD-EPIcreatinine equation (2009).

4. 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

5. Initiation of treatment, or a change in dose to ongoing treatment, with anangiotensin-converting-enzyme inhibitor (ACEI) or angiotensin II receptor blocker (ARB) in the 4 weeks prior to screening.

6. Currently taking another investigational drug for any condition

7. Carry only known non-pathogenic Fabry mutations

8. History of renal dialysis or kidney transplantation

9. History of acute kidney injury in the 12 months prior to screening, includingspecific kidney diseases (e.g., acute interstitial nephritis, acute glomerular andrenal vasculitis); non-specific conditions (e.g., ischemia, toxic injury); orextrarenal pathology (e.g., prerenal azotaemia, and acute postrenal obstructivenephropathy

10. History of (or current) malignancy requiring treatment; the one exception is a priorhistory of resected basal cell carcinoma

11. Severe cardiomyopathy or significant unstable cardiac disease within 6 months priorto screening

12. A positive test for Severe Acute Respiratory Syndrome-Coronavirus 2 (SARS-CoV-2)within 3 months prior to screening, using a validated molecular assay or validatedantigen assay

13. 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 received

14. Presence of any medical, emotional, behaevioral, or psychological condition that inthe judgment of the Investigator could interfere with the subject's compliance withthe requirements of the study

15. Previous treatment with cellular therapy or gene therapy for any condition