A Study of SEL-212 in Patients With Gout Refractory to Conventional Therapy II

Inclusion Criteria:

1. Has negative results of an FDA Emergency Use Authorized COVID-19 molecular assay fordetection of SARS-CoV-2 RNA from a nasal or oropharyngeal specimen;

2. History of symptomatic gout defined as:

3. ≥ 3 gout flares within 18 months of Screening or

4. Presence of ≥ 1 gout tophus or

5. Current diagnosis of gouty arthritis

6. At the Screening Visit: male age 21 - 80 years, inclusive, or female ofnon-childbearing potential age 21-80 years, inclusive, where nonchildbearingpotential is defined as:

7. > 6 weeks after hysterectomy with or without surgical bilateralsalpingo-oophorectomy or

8. Post-menopausal (> 24 months of natural amenorrhea or in the absence of >24months of amenorrhea, one documented confirmatory FSH measurement)

9. Has chronic refractory gout defined as having failed to normalize sUA and whosesigns and symptoms are inadequately controlled with any of the xanthine oxidaseinhibitors, or for whom these drugs are contraindicated for the patient;

10. Has at the Screening Visit SUA ≥ 7 mg/dL

11. Negative serology for HIV-1/-2 and negative antigen to hepatitis B and negativeantibodies to hepatitis C;

Exclusion Criteria:

1. Has a history of anaphylaxis, severe allergic reactions, or severe atopy;

2. Has a history of any allergy to pegylated products, including, but not limited topegloticase (Krystexxa®), peginterferon alfa-2a (Pegasys®), peginterferon alfa-2b (PegIntron®), pegfilgrastim (Neulasta®), pegaptanib (Macugen®), pegaspargase (Oncaspar®), pegademase (Adagen®), peg-epoetin beta (Mircera®), pegvisomant (Somavert®) certolizumab pegol (Cimzia®), naloxegol (Movantik®), peginesatide (Omontys®), and doxorubicin liposome (Doxil®);

3. Is taking and cannot discontinue known major CYP3A4/P-gp inhibitors or majorCYP3A4/P-gp inducers at least 14 days before dosing. Patients must remain off thesemedications for the duration of the study, including natural products such as St.John's Wort or grapefruit juice.

4. Is taking drugs known to interact with rapamycin (sirolimus - Rapamune®) such ascyclosporine, diltiazem, erythromycin, ketoconazole, posaconazole, voriconazole,itraconazole, rifampin, verapamil unless they are stopped 14 days prior to dosingand will not be used/prescribed during the trial.

5. Had major surgery within 3 months of initial screening.

6. Had a gout flare during Screening that was resolved for less than 1 week prior tofirst treatment with study drug (exclusive of chronic synovitis/arthritis) unlessthe patient has a history of inter-flare intervals of < 1 week.

7. Has uncontrolled diabetes at Screening with HbA1c ≥ 8.5%;

8. Has fasting Screening glucose > 240 mg/dL;

9. Has fasting Screening triglyceride > 500 mg/dL;

10. Has fasting Screening low-density lipoprotein (LDL) > 200 mg/dL;

11. Has glucose-6-phosphate dehydrogenase (G6PD) deficiency;

12. Has uncontrolled hypertension defined as blood pressure > 170/100 mmHg at Screeningand 1 week prior to dosing

13. Individual laboratory values which are exclusionary

• White blood cell count (WBC) < 3.0 x109/L

• Serum aspartate aminotransferase (AST) or alanine amino transferase (ALT) > 3xupper limit of normal (ULN) in the absence of known active liver disease

• Estimated glomerular filtration rate (eGFR) < 30 mL/min/1.73 m2

• Urine albumin creatinine ratio (UACR) > 30 mg/g

• Hemoglobin (Hgb) < 9 g/dL

• Serum phosphate < 2.0 mg/dL

14. Is receiving ongoing treatment for arrhythmia, including placement of an implantabledefibrillator, unless considered stable and on active treatment;

15. Has evidence of unstable cardiovascular disease or unstable cerebrovascular vasculardisease. This includes patients who have had a cardiac/vascular event(s) in the last 3 months including heart attack, stroke or vascular bypass surgery or patients whoare deemed, by their physician or PI, to have active cardiovascular, cerebrovascularor peripheral vascular symptoms/disease inadequately controlled by medication;

16. Has congestive heart failure, New York Heart Association Class III or IV;

17. Unless clinically stable and/or appropriately treated, electrocardiogram (ECG) withevidence of clinically significant arrhythmia or other abnormalities that, in theopinion of the investigator, are consistent with significant underlying cardiacdisease;

18. History of significant hematological disorders within 5 years or autoimmunedisorders, and/or patient is currently immunosuppressed or immunocompromised;

19. Prior exposure to any experimental or marketed uricase (e.g., rasburicase (Elitek,Fasturtec), pegloticase (Krystexxa®®), pegadricase (SEL 037))

20. Patient has received a live vaccine in the previous 6 months.

21. Patient is planning to receive any live vaccine during the study.

22. History of malignancy within the last 5 years other than basal skin cancer;

23. Patients with a documented history of moderate or severe alcohol or substance usedisorder within the 12 months prior to randomization.

24. History of or evidence of clinically severe interstitial lung disease

25. Immunocompromised state, regardless of etiology