Inclusion Criteria:

* Male or female participants 18 years of age or older at the time of signing informed consent
* Participants who have voluntarily given written informed consent after the nature of the study has been explained according to applicable requirements prior to study entry
* Central histologic confirmation of high-grade non-muscle invasive CIS (± Ta/T1) with active disease
* Participants who are BCG naive, or participants who are BCG exposed and have not received intravesical BCG for at least 24 months prior to the most recent CIS diagnosis (Cohort A). Participants with persistent or recurrent CIS (± Ta/T1) who are BCG unresponsive within 12 months of completion of adequate BCG therapy (Cohort B).

Exclusion Criteria:

* Penicillin allergy (participants with a questionable history of allergy to penicillin will undergo penicillin blood allergy testing via central laboratory
* Predominant (defined as \> 50%) adenocarcinoma, squamous cell carcinoma, or histological variants including plasmacytoid, sarcomatoid, or squamous components according to central review
* Concomitant prostatic or upper tract urothelial involvement per Investigator's assessment
* Nodal and metastatic disease are excluded if they existed at any time (whether present or in the past)
* Any history of ≥ T2 bladder cancer that existed at any point in time in the participant's history

For more information on eligibility criteria, please contact the Sponsor

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 6/11/2024. Questions regarding updates should be directed to the study team contact.