A Study of HG146 Capsule in Chinese Subjects with Relapsed and Refractory Multiple Myeloma

Inclusion Criteria: * Diagnosis of multiple myeloma requiring systemic therapy (International Myeloma Working Group \[IMWG\]) and 2 cycles of treatment including proteasome inhibitors and/or immunomodulators. * Serum M protein≥ 10.0g / L, or urine M protein ≥ 200mg / 24h. * Not suitable for autologous bone marrow transplantation or refuse autologous bone marrow transplantation or relapse after autologous bone marrow transplantation. * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 or 2. * Expected survival of ≥3 months. * Hemoglobin ≥ 80 g/L, Platelet≥75×10\^9/L, Absolute Neutrophil Count≧1.0×109/L (1000 cells/mm3), Prothrombin time(PT) and activated partial thromboplastin time ≤ 2 x Upper Limit of Normal (ULN). * Bilirubin in serum\<1.5\*ULN (2.0mg/dL/20mg/L/34.2μmol/L); glutamic-pyruvic transaminase (ALT) and/or Aspartate Aminotransferase (AST)≤3\*ULN (upper limit of normal). * Normal electrocardiogram, echocardiography and myocardial enzyme spectrumCalibration of blood calcium concentration≤ULN. * Men and women, Non-pregnant women who did not consider giving birth during the trial or five years after the end of the trial. * The patient is able to swallow the capsule. * Patients must provide written consent. Exclusion Criteria: * Severe allergies to the study drug or any of its excipients. * The possibility of gene toxicity, mutagenesis and teratogenicity. * Men and women who did not have sperm or egg cells stored in vitro before the trial and who planned to have children again within five years. * Pregnant or lactating women. * Perform autologous bone marrow transplantation 3 months before admission. * Receive allogeneic bone marrow transplantation. * Use HDAC inhibitors before. * Two weeks prior to admission, received radiotherapy or bone marrow suppressive chemotherapy or biological treatment. * Patients with history of other malignant tumors, except the tumor is in remission and has not been treated for at least 5 years. * Patients with dysphagia or oral absorption disorder. * The investigators determine the conditions not suitable for the study.