This study will establish the safety and effectiveness of the SAPIEN M3 System in subjects with symptomatic, at least 3+ mitral regurgitation (MR) for whom commercially available surgical or transcatheter treatment options are deemed unsuitable.

Following completion of enrollment, subjects will be eligible for enrollment in the continued access phase of the trial.

This is a prospective single-arm, multicenter study.

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