A Trial to Learn How Well REGN9933 and REGN7508 Work for Preventing Blood Clots, and How Safe They Are, in Adults Who Have a Peripherally Inserted Central Catheter (PICC)

A Master Protocol for a Phase 2 Randomized, Double-Blind, Placebo-Controlled Study of REGN9933 and REGN7508, Monoclonal Antibodies Against Factor XI for Prevention of Venous Thromboembolism in Patients With a Peripherally Inserted Central Catheter (ROXI-CATH)

This study is researching 2 different experimental drugs called REGN9933 and REGN7508 (called "study drugs"). The study is focused on adults undergoing a placement of a catheter in the vein, also called a 'PICC line'.

The aim of the study is to see how effective the study drug is at preventing venous thromboembolism (VTE) and other related disease after catheter placement.

The study is looking at several other research questions, including:

• What side effects may happen from taking the study drug
• How much study drug is in the blood at different times
• Whether the body makes antibodies against the study drug (which could make the study drug less effective or could lead to side effects)

Key Inclusion Criteria:

1. PICC is clinically indicated for at least 14 days and is anticipated to remain in place for at least 14 days
2. Eastern Cooperative Oncology Group (ECOG) Performance Status ≤2 or equivalent functional status as described in the protocol
3. Body weight ≥45 kg and ≤130 kg during the screening period
4. International normalized ratio (INR) and aPTT values at or below the upper limit of normal as defined by the local lab during the screening period
5. Platelet count ≥100 x 10^9/L during the screening period as described in the protocol

Key Exclusion Criteria:

1. Unsuccessful PICC placement or any other complication associated with this procedure that in the opinion of the study investigator may present any safety concerns to the participant
2. History of prior venous thrombosis in the arm in which the PICC is to be placed
3. Peripheral catheter(s) in the same arm in which the PICC is to be placed or expected need for peripheral catheter(s) placement in the same arm the PICC is to be placed as described in the protocol
4. History of known thromboembolic disease or thrombophilia
5. Participants requiring therapeutic anticoagulation and/or antiplatelet therapy as described in the protocol
6. Expected to receive cancer therapy or other medication associated with a prior episode of Grade 4 thrombocytopenia as described in the protocol
7. Any history of intracranial or intraocular bleeding, excessive operative or post-operative bleeding, traumatic spinal or epidural anesthesia, or history of bleeding diathesis (such as but not limited to Hemophilia A or B, von Willebrand's disease, fibrinogen deficiency, and other inherited or acquired bleeding disorders) as described in the protocol

Note: Other protocol defined inclusion/exclusion criteria apply