BOSTON: This trial evaluates the effectiveness, safety and affect on quality of life for two drug regimes using a combination of targeted therapy drugs (Selinexor, Bortezomib) and steroids (Dexamethasone) for the treatment of patients with recurrent Multiple MyelomaA Phase 3 Randomized, Controlled, Open-label Study of Selinexor, Bortezomib, and Dexamethasone (SVd) Versus Bortezomib and Dexamethasone (Vd) in Patients With Relapsed or Refractory Multiple Myeloma (RRMM)

Exclusion

1. Prior exposure to a SINE compound (i.e. an XPO-1 inhibitor), including selinexor.
2. Prior malignancy that required treatment, or has shown evidence of recurrence (except for non-melanoma skin cancer or adequately treated cervical carcinoma in situ) during the 5 years prior to randomization.
3. Any concurrent medical condition or disease (e.g., uncontrolled active hypertension, uncontrolled active diabetes, active systemic infection, etc.) that is likely to interfere with study procedures.
4. Uncontrolled active infection requiring parenteral antibiotics, antivirals, or antifungals within 1 week prior to C1D1.
5. Active plasma cell leukemia.
6. Documented systemic light chain amyloidosis.
7. MM involving the central nervous system.
8. Polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes (POEMS) syndrome.
9. Spinal cord compression.
10. Greater than Grade 2 neuropathy or ≥ Grade 2 neuropathy with pain at baseline, regardless of whether or not the patient is currently receiving medication
11. Known intolerance, hypersensitivity, or contraindication to glucocorticoids.
12. Radiation, chemotherapy, or immunotherapy or any other anticancer therapy (including investigational therapies) ≤ 2 weeks prior to C1D1. Localized radiation to a single site at least 1 week before C1D1 is permitted. Glucocorticoids within 2 weeks of C1D1 are permitted. Patients on long-term glucocorticoids during Screening do not require a washout period but must be able to tolerate the specified dexamethasone dose in this study.
13. Prior autologous stem cell transplantation < 1 month or allogeneic stem cell transplantation < 4 months prior to C1D1.
14. Active graft versus host disease (after allogeneic stem cell transplantation) at C1D1.
15. Pregnant or breastfeeding females.
16. Body Surface Area < 1.4 m² at baseline, calculated by the Dubois or Mosteller method.
17. Life expectancy of < 4 months.
18. Major surgery within 4 weeks prior to C1D1.

19. Active, unstable cardiovascular function:

    1. Symptomatic ischemia, or
    2. Uncontrolled clinically significant conduction abnormalities (e.g., patients with ventricular tachycardia on anti-arrhythmics are excluded; patients with first-degree atrioventricular block or asymptomatic left anterior fascicular block/right bundle branch block will not be excluded), or
    3. Congestive heart failure of New York Heart Association Class ≥ 3 or known left ventricular ejection fraction < 40%, or
    4. Myocardial infarction within 3 months prior to C1D1.
20. Known active human immunodeficiency virus (HIV) infection or HIV seropositivity
21. Known active hepatitis A, B, or C infection; or known to be positive for hepatitis C virus ribonucleic acid (RNA) or hepatitis B virus surface antigen.
22. Any active gastrointestinal dysfunction interfering with the patient's ability to swallow tablets, or any active gastrointestinal dysfunction that could interfere with absorption of study treatment.
23. Any active, serious psychiatric, medical, or other conditions/situations that, in the opinion of the Investigator, could interfere with treatment, compliance, or the ability to give informed consent.
24. Contraindication to any of the required concomitant drugs or supportive treatments.
25. Patients unwilling or unable to comply with the protocol, including providing 24-hour urine samples for urine protein electrophoresis at the required time points.