A Study to Evaluate Efficacy and Safety of PTC299 (Emvododstat) in Hospitalized Participants With Coronavirus (COVID-19)

Inclusion Criteria:

- Signed and dated informed consent document(s).

- Agrees to the collection of nasopharyngeal swabs and venous blood and all other
protocol-specified procedures.

- Male or non-pregnant female adult ≥18 years of age at time of enrollment.

- Hospitalized and has laboratory-confirmed infection with severe acute respiratory
syndrome coronavirus 2 (SARS-CoV-2).

- Symptom onset was ≤10 days prior to screening.

- Has oxygen saturation SpO2 <94% on room air.

- Has at least one of a respiratory rate >24 breaths/minute or cough.

- Lung involvement as confirmed by radiographic infiltrates observed on imaging (chest
X-ray, computed tomography (CT) scan, or an equivalent test).

- Women of childbearing potential (as defined in [CTFG 2014]) must have a negative
pregnancy test at screening and agree to abstinence or the use at least one of the
following highly effective forms of contraception (with a failure rate of <1% per year
when used consistently and correctly). Contraception or abstinence must be continued
for the duration of the study following discharge from the hospital, and for up to 50
days after the last dose of study drug:

i) combined (estrogen and progestogen containing) hormonal contraception associated
with inhibition of ovulation: oral, intravaginal, and transdermal ii) progestogen-only
hormonal contraception associated with inhibition of ovulation: oral, injectable, and
implantable iii) intrauterine device iv) intrauterine hormone-releasing system v)
vasectomized partner with confirmed azoospermia All females will be considered of
childbearing potential unless they are postmenopausal (at least 12 months consecutive
amenorrhea in the appropriate age group without other known or suspected cause) or
have been sterilized surgically (for example, bilateral tubal ligation, hysterectomy,
bilateral oophorectomy).

- Men sexually active with women of childbearing potential who have not had a vasectomy
must agree to use a barrier method of birth control during the study following
discharge from the hospital and for up to 50 days after the last dose of study drug.

Exclusion Criteria:

- Requires mechanical ventilation.

- Current participation in any other interventional study.

- Alanine transaminase/aspartate transaminase levels ≥3 times the upper limit of normal
(×ULN) or total bilirubin (Tbili) ≥2×ULN.

- Lymphocyte count <500 lymphocytes/microliter (μL) or hemoglobin <11 grams/deciliter
(g/dL).

- Stage 4 severe chronic kidney disease or requiring dialysis (that is, estimated
glomerular filtration rate <30).

- Any other condition, that in the opinion of the Investigator, may be cause to exclude
the participant from the study.

- Use of steroids (except dexamethasone), sensitive CYP2D6 substrates, CYP2C inducers,
IL-6 neutralizing antibodies, IL-6 receptor inhibitors, or any investigational
therapy.

- Pregnancy or breast feeding.

- Anticipated transfer to another hospital which is not a study site within 72 hours.

- Known allergy to PTC299 or excipients.