Alport syndrome (AS) is a rare genetic condition that causes kidney disease, hearing loss, and eye abnormalities that occur due to changes in specific genes (COL4A3, COL4A4, and COL4A5). These genes help in producing an important protein called collagen. People with AS have a high risk of developing chronic kidney disease (CKD), a condition in which there is progressive loss in kidney function over time. The kidneys soon lose their ability to remove waste products from the body properly, resulting in end-stage kidney disease. A common sign of decreasing kidney function is the presence of excess protein in the urine that is not usually found with healthy kidneys. This condition is known as proteinuria. The study drug, BAY 3401016 (a monoclonal antibody), is a type of medicine that blocks a protein called Semaphorin 3A (Sema3A), which is thought to be involved in causing kidney damage in AS. By blocking the action of the Sema3A protein, BAY 3401016 may prevent proteinuria and slow down the loss in kidney function due to AS.

The main purpose of this study is to learn more about how well BAY 3401016 works in slowing down the loss in kidney function in adults with a rapidly progressing AS.

Inclusion Criteria:

• Participants must be 18 to 45 years of age inclusive
• Participants with AS, either XLAS (male) or ARAS (male or female)
• eGFR ≥ 45 mL/min/1.73m2
• UACR ≥ 500mg/g

Exclusion Criteria:

• Chronic kidney disease is different from AS
• Clinically significant illness that could have influence on the safety of the participant and/or interfere with the study objectives
• History or current existence of malignancy
• Participants with history of severe allergies, multiple drug allergies or non-allergic drug reactions including allergies affecting the lower respiratory tract - allergic asthma, allergies requiring therapy with corticosteroids or urticaria
• Participants with active skin disorders (e.g. atopic dermatitis, severe acne)
• Systolic blood pressure above 140 mmHg
• Diastolic blood pressure above 90 mmHg

Availability of this study's data will later 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.vivli.org 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 member section of the portal.