This is an observational study in which only data will be collected from children with venous thromboembolism who are prescribed rivaroxaban or warfarin by their doctors.

Venous thromboembolism (VTE) is a condition in which people have problems due to the formation of blood clots in their veins.

The study drug rivaroxaban is an approved treatment for VTE in children and adults in Japan. It is a blood thinner that prevents the blood from clotting by blocking a protein responsible for blood clotting.

Warfarin is another blood thinner that is available for VTE. In this study warfarin is the reference drug.

A previous study was carried out to learn about how well rivaroxaban works and how safe it is in children with VTE. However, to better understand the safety of this drug in children, more knowledge is needed about the use of rivaroxaban in the real world.

The main purpose of this study is to learn more about the occurrence of major bleeding in children taking rivaroxaban. Major bleeding can be bleeding within the skull, bleeding inside the eye, bleeding from an organ in the digestive system, or bleeding which requires being given blood from a donor.

In addition, this study will help learn more about the following in children with VTE:

• The occurrence of major bleeding during treatment with rivaroxaban and during treatment with warfarin
• The occurrence of bleeding of importance in children being treated with rivaroxaban and in children being treated with warfarin. Bleeding of importance in children can be: bleeding from the lung, blood in the kidney, heavy menstrual bleeding
• The occurrence of major bleeding and bleeding of importance in children who are taking drugs called anti platelet agents and NSAIDs to prevent blood clots at the same time as rivaroxaban, who are taking a drug that blocks the action of a protein called 'CYP3A4' at the same time as rivaroxaban, who have reduced kidney function, who have taken rivaroxaban for a long time, or who have taken other drugs by mouth to prevent blood clots before starting rivaroxaban
• The occurrence of repeated VTE on treatment with rivaroxaban and on treatment with warfarin The children with VTE in this study are already receiving rivaroxaban or warfarin treatment as part of their regular care from their doctors.

The data will come from an electronic health records database created by a company called Medical Data Vision. The data will be collected between January 2021 and June 2024.

Researchers will look at the health information from children less than 18 years of age with VTE in Japan who are prescribed treatment with rivaroxaban or warfarin during the study period.

In this study, only available data from routine care are collected. No visits or tests are required as part of this study

Inclusion Criteria:At index date, which is the date of first prescription of rivaroxaban or of warfarin during the study period

• Age less than 18 years
• Diagnosis of VTE at any point before and including the index date
• Receiving a prescription/dispensation of rivaroxaban or warfarin

Exclusion Criteria:

• none

Patients with pediatric VTE treated with rivaroxaban or warfarin in real-world clinical practice in Japan between 01 January 2021 and 30 June 2024

Availability of this study's data will be determined according to Bayer's commitment to the EFPIA/PhRMA "Principles for responsible clinical trial data sharing". This pertains to scope, timepoint and process of data access. As such, Bayer commits to sharing upon request from qualified researchers patient-level clinical trial data, study-level clinical trial data, and protocols from clinical trials in patients for medicines and indications approved in the US and EU as necessary for conducting legitimate research. This applies to data on new medicines and indications that have been approved by the EU and US regulatory agencies on or after January 01, 2014. Interested researchers can use www.clinicalstudydatarequest.com to request access to anonymized patient-level data and supporting documents from clinical studies to conduct research. Information on the Bayer criteria for listing studies and other relevant information is provided in the Study sponsors section of the portal.