The ENCIRCLE Trial

Inclusion Criteria: 1. 18 years of age or older 2. MR ≥ 3+ 3. NYHA functional class ≥ II 4. Per the Heart Team, commercially available surgical or transcatheter treatment options are deemed unsuitable due to clinical, anatomic or technical considerations. 5. Subject's heart failure management has been optimized based on subject characteristics and applicable guidelines, and stable for at least 30 days prior to enrollment. 6. The subject or subject's legal representative has been informed of the nature of the study, agrees to its provisions and has provided written informed consent. Exclusion Criteria: 1. Mitral/cardiac anatomy that would preclude appropriate delivery and deployment of the SAPIEN M3 dock or valve 2. Inappropriate anatomy for femoral introduction and delivery of the SAPIEN M3 dock and valve 3. Presence of any device that will contact or interfere with the SAPIEN M3 System during delivery or after implantation 4. Left ventricular ejection fraction \<25% 5. Severe right ventricular dysfunction 6. Need for aortic, tricuspid or pulmonic valve intervention within the next 12 months 7. History of heart transplant 8. Cardiac imaging evidence of intracardiac mass, thrombus or vegetation 9. Active bacterial endocarditis within 180 days of the procedure 10. Hemodynamic instability requiring inotropic or mechanical support within 30 days of the procedure 11. Myocardial infarction within 30 days of the procedure 12. Clinically significant untreated coronary artery disease requiring revascularization 13. Any percutaneous cardiovascular intervention, cardiovascular surgery, or carotid surgery within 30 days of the procedure 14. Stroke or transient ischemic attack within 90 days of the procedure 15. Irreversible, severe pulmonary hypertension 16. Chronic obstructive pulmonary disease requiring home oxygen therapy or chronic outpatient oral steroid use 17. Renal insufficiency or receiving renal replacement therapy 18. Liver disease 19. Planned surgery within the next 12 months 20. Inability to tolerate or a medical condition precluding treatment with antithrombotic therapy, including heparin administration during the procedure 21. Active infection requiring current antibiotic therapy 22. Active SARS-CoV-2 infection (Coronavirus-19 \[COVID-19\]) or previously diagnosed with COVID-19 with sequelae that could confound endpoint assessments 23. Leukopenia, anemia, thrombocytopenia, history of bleeding diathesis or coagulopathy or hypercoagulable states 24. Refusal of blood products 25. Female who is pregnant or lactating 26. Estimated life expectancy \<12 months due to non-cardiac conditions 27. Participating in another investigational drug or device study that has not reached its primary endpoint 28. Subject considered to be part of a vulnerable population