Inclusion Criteria:

          -  Patient has given voluntary written informed consent before performance of any
             study-related procedures not part of standard (non-investigational) medical care.

          -  Patient has been previously diagnosed with multiple myeloma based on standard
             criteria.

          -  Patient has relapsed or refractory disease according to international uniform response
             criteria and must have previously received therapy with:

               -  A proteasome inhibitor and Immunomodulatory imide drugs (IMiD)

               -  All subjects must have documented disease progression during or after their last
                  antimyeloma therapy.

          -  Patient has an Eastern Cooperative Oncology Group (ECOG) performance status score ≤ 2.

          -  Patient has measurable disease defined as at least one of the following:

               -  Serum M protein ≥ 0.5 /dL (≥5 g/L)

               -  Urine M protein ≥ 200 mg/24 hours

               -  Serum free light chain (FLC) assay: Involved FLC assay ≥10 mg/dL (≥100 mg/L) and
                  an abnormal serum FLC ratio (<0.26 or >1.65)

          -  Clinical Laboratory Inclusion Criteria: The following laboratory results must be met
             within 14 days (or as stipulated) prior to study drug (treatment) administration:

               -  Absolute neutrophil count (ANC) ≥ 1000 cells/μl (growth factor cannot be used
                  within the previous 5 days)

               -  Platelet count ≥ 50,000/μl (without platelet transfusion in the previous 5 days)

               -  Aspartate aminotransferase (AST/SGOT) and Alanine aminotransferase (ALT/SGPT) ≤
                  3.0 x upper limit of normal (ULN)

               -  Serum total bilirubin ≤ 2.0 mg/dL or >3.0 x ULN for subjects with hereditary
                  benign hyperbilirubinemia

               -  Creatinine clearance ≥ 30 ml/min (calculated by the Cockcroft-Gault Equation or
                  per 24 hour urine collection)

               -  Serum calcium (corrected for albumin) level at or below the ULN range (treatment
                  of hypercalcemia is allowed and subject may enroll if hypercalcemia returns to
                  normal range with standard treatment).

          -  Females of childbearing potential (FCBP) must have a negative serum or urine pregnancy
             test prior to initiation of the study treatment with Vactosertib/POM. The test must
             have a sensitivity of at least 50 mIU/mL. Study participants who are FCBP must either
             commit to continued abstinence from heterosexual intercourse or begin two acceptable
             methods of birth control, one highly effective method and one additional effective
             method at the same time, at least 28 days before she starts taking POM through 30 days
             after the last dose of POM and 60 days after the last dose of Vactosertib. FCBP must
             also agree to ongoing pregnancy testing during the entire duration of treatment. Men
             must agree to use a latex or synthetic condom during sexual contact with a FCBP even
             if they have had a vasectomy from the time of signing the informed consent form
             through 60 days after the last dose of POM or Vactosertib. These same patients must
             not donate sperm. All patients must be counseled at a minimum of every 28 days about
             pregnancy precautions and risks of fetal exposure. All patients enrolled into this
             trial, must agree to be registered in and must comply with all requirements of the
             Pomalidomide Risk Evaluation and Mitigation Strategy (POM REMS™) program.

        Exclusion Criteria:

          -  Prior therapy with Vactosertib or received any investigational drug within the prior
             28 days.

          -  Plasma Cell Leukemia

          -  Patients with solitary plasmacytoma

          -  Patients who are primarily eligible for autologous stem cell transplant

          -  Prior anti-cancer therapy (chemotherapy, targeted agents, radiotherapy, and
             immunotherapy) within the prior 21 days except for alkylating agents (e.g., melphalan)
             within the prior 28 days.

          -  Prior treatment with pomalidomide.

          -  Subjects with active malignancy and/or cancer history that may confound the assessment
             of the study endpoints. Patients with a past cancer history (within 2 years of entry)
             with substantial potential for recurrence and/or ongoing active malignancy must be
             discussed with the trial collaborator, MedPacto Inc., before study entry. Patients
             with the following neoplastic diagnoses are eligible: non-melanoma skin cancer,
             carcinoma in situ (including superficial bladder cancer), cervical intraepithelial
             neoplasia, and organ-confined prostate cancer with no evidence of progressive disease

          -  Any > grade 1 (according to the National Cancer Institute Common Terminology Criteria
             for Adverse Events (NCI CTC AE) v.4.03) adverse reaction unresolved from previous
             treatments or not readily managed and controlled with supportive care. The presence of
             alopecia of any grade and peripheral neuropathy ≤ Grade 2 without pain is allowed.

          -  Previous allogeneic stem cell transplantation with active graft versus host disease
             (GVHD), or treatment with immunosuppressive therapy in the 2 months prior to study
             entry.

          -  No oral corticosteroids 3 days before initiating combinations Vactosertib/POM; inhaled
             corticosteroids are permitted.

          -  Patient is known to be human immunodeficiency virus (HIV) positive, or have chronic or
             active Hepatitis B (core- or surface antigen-positive) or active hepatitis C
             infection.

          -  Clinically significant cardiovascular disease (e.g., uncontrolled or any New York
             Heart Association (NYHA) Class 3 or 4, congestive heart failure, uncontrolled or
             unstable angina, history of myocardial infarction or stroke within 6 months prior to
             study entry, or clinically significant arrhythmias not controlled by medication).

          -  Major abnormalities identified by ECG or echocardiogram (ECHO), at the Investigator's
             discretion.

          -  Presence of aneurisms of the ascending aorta or aortic stress.

          -  Hypertension that is not controlled by standard medication (to 150/90 mmHg or below).

          -  Uncontrolled, clinically significant pulmonary disease (e.g., chronic obstructive
             pulmonary disease (COPD), pulmonary hypertension) that in the opinion of the
             investigator would put the patient at significant risk for pulmonary complications
             during the study.

          -  Uncontrolled intercurrent illness including, but not limited to, uncontrolled
             infection, disseminated intravascular coagulation (DIC), or psychiatric illness/social
             situations that would limit compliance with study requirements.

          -  History of erythema multiforme or severe hypersensitivity to prior IMiD's such as
             thalidomide and lenalidomide.

          -  Patients requiring hemodialysis

          -  The patient is receiving medications that are:

               -  Exclusively or primarily eliminated by cytochrome P-450 isozyme 3A4 (CYP3A4).

               -  Exclusively or primarily eliminated by Uridine 5'-diphospho
                  (UDP)-glucuronyltransferase 1A1 (UGT1A1).

               -  Substrates for the drug transporter multidrug resistance protein 1 (MDR1) have a
                  narrow therapeutic window; or which are strong inhibitors of drug transporter
                  MDR1.

          -  Patients should have discontinued strong CYP1A2 inhibitors (e.g. ciprofloxacin and
             fluvoxamine) at least five half-lives before beginning study treatment.

          -  Inability to tolerate thromboprophylaxis (Required Concurrent Medications)