Inclusion Criteria:  Male or female subjects 18 years of age or older at the time of signing the informed consent Subjects who have voluntarily given written informed consent after the nature of the study has been explained according to applicable requirements prior to study entry Subjects with a histologically confirmed, high-grade Ta or CIS urothelial cell carcinoma of the bladder according to American Joint Committee on Cancer staging and 2016 WHO/ISUP grading classification. Subjects who are unable to obtain intravesical BCG for the treatment of NMIBC, have received at least one dose of intravesical BCG, or at least one dose of intravesical chemotherapy  Exclusion Criteria:  Penicillin allergy (subjects with a questionable history of allergy to penicillin or no history of penicillin use will undergo sensitivity testing prior to inclusion in the study) Predominant (defined as > 50%) adenocarcinoma, squamous cell carcinoma, or histological variants including plasmacytoid, sarcomatoid, or squamous components Prostatic involvement, upper tract urothelial carcinoma, nodal involvement, or metastatic disease Bladder cancer stage ≥ T1 according to American Joint Committee on Cancer staging criteria Bladder cancer stage CIS with concomitant T1  For more information on eligibility criteria, please contact the sponsor.