**Phase 2a Study of VX-407 in Participants With ADPKD Who Have a Subset of PKD1 Gene Variants (AGLOW)** Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a condition where cysts grow in the kidneys. This study is testing a drug called VX-407 to see if it reduces the size of the kidneys when adjusted for height (htTKV). The study also checks the safety, how the body tolerates the drug, and how the drug moves through the body (pharmacokinetics or PK). **Who can join?** People diagnosed with ADPKD, who can attend all visits, and have a specific kidney imaging classification. They need a certain level of kidney function measured by eGFR (a test that shows how well the kidneys are working). **Who cannot join?** If you have other kidney diseases, have had a kidney removed, or have had a transplant, you cannot join. You also cannot join if you are on dialysis or plan to start it soon. **Key Points:** - **Study Visits:** Participants must attend scheduled visits. - **Eligibility:** Specific kidney function and imaging criteria are required. - **Exclusions:** Certain medical histories like other kidney diseases or transplants disqualify participation.