This is an open-label, multi-center, single group, Phase 3 study for treatment with rilzabrutinib.

The purpose of this study is to provide continuation of rilzabrutinib treatment to adult participants with ITP who have completed the LTE of the LUNA 3 study in Japan, demonstrating clinically meaningful benefit as judged by the Investigator.

Inclusion Criteria:

• Participants who have been enrolled in and have completed the LTE of the LUNA 3 study with demonstration of efficacy without major safety concern while on study considered by the Investigator to be clinically meaningful.
• Participants who have ongoing diagnosis of primary ITP and continue to require treatment for ITP according to the Investigator.
• Participants who have acceptable benefit/risk profile.
• Contraceptive use by men and women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.

Exclusion Criteria:

• Participants with secondary ITP.
• Pregnant or lactating women.
• Electrocardiogram (ECG) findings for participants. The above information is not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org