1. Proteasome inhibitors: Bortezomib has been widely used clinically as a first-generation proteasome inhibitor. Carfilzomib, a second-generation proteasome inhibitor, was approved by the US FDA on July 20, 2012 for the treatment of relapsed refractory MM, and has been shown to be effective in clinical trials for the monotherapy of relapsed myeloma. The ORR was 42% (52% in the increased dose group) every 28 days, with a median PFS of 8,3 months for all patients. The common grade 3/4 toxicities were mainly hematological events, with a very low incidence of peripheral neuropathy, 14% and 19% for grades 1/2 and only 2% and 0% for grades 3/4, respectively. Another clinical trial confirmed that no dose adjustment of carfilzomib is required in patients with renal failure. For combination chemotherapy, a phase I/II clinical trial of carfilzomib + lenalidomide + dexamethasone combination (relapsed refractory myeloma) had an ORR of 78% with manageable toxicity. The phase III clinical trial ASPIRE on this basis has been enrolled and completed. 2. Immunomodulators: Thalidomide and lenalidomide, as the first and second generation immunomodulators, have been widely used in domestic and foreign clinics respectively. Pomalidomide is the newest immunomodulator, which was approved by the US FDA on February 8, 2013 for the treatment of relapsed refractory MM and can overcome the resistance of bortezomib and lenalidomide with a low incidence of thromboembolic events. Pomalidomide has independent drug activity and also has good efficacy when used in combination. Studies from Europe and the United States have consistently shown that the remission rate with pomalidomide and dexamethasone in lenalidomide-resistant patients is about 30%. Recently, it has been reported that pomalidomide combined with cyclophosphamide and prednisone is safe and effective in the treatment of relapsed refractory MM, with an ORR of 51% with pomalidomide 2 and 5 mg/d along with cyclophosphamide 50 mg and prednisone 50 mg once every other day. Many studies are underway for pomalidomide in combination with existing drugs or new chemotherapy agents under development. 3. Histone deacetylase inhibitor HDACi: In plasma cell disease, the likely mechanism is inhibition of histone deacetylase 6 (HDAC6), an important function of HDAC6 that affects bypass pathways of proteolytic metabolism including the aggregation pathway and the autophagy pathway. It has been clinically demonstrated that proteasome inhibitors and histone deacetylase 6 inhibitors have synergistic effects in patients with myeloma. Phase I clinical trials of Vorinostat in combination with bortezomib showed an overall response rate of 30% and were particularly effective in those patients with bortezomib resistance; however, Phase II studies did not show an advantage in PFS and OS compared to single-agent bortezomib, which may be related to the toxicity limitations of Vorinostat. Panobinostat Panobinostat has a better safety profile than vorinostat and showed encouraging response rates in both phase I and II studies; the phase III randomized trial “Panoramal Study”: comparing bortezomib/dexamethasone with pabtizomib/bortezomib/dexamethasone in patients with early relapsed myeloma. Bortezomib/dexamethasone in patients with early relapsed myeloma, the results are expected. 4. Antibody drugs: Anti-MM mechanism mainly involves 1 antibody-dependent cytotoxic effect (ADCC); complement-dependent cytotoxic effect; direct inhibition of proliferation or promotion of apoptosis. Antibody drugs alone have limited anti-MM effects, but the combination of immunomodulators and antibody drugs can produce synergistic anti-MM effects, for example, lenalidomide significantly increases anti-CS1 monoclonal antibody-induced ADCC. phase I/II clinical studies have tested the efficacy of the combination chemotherapy of lenalidomide, erlotuzumab (CS1 antibody) and low-dose dexamethasone, with high remission rates and long duration of remission, compared with the previous Phase III randomized clinical study evaluating the clinical efficacy of lenalidomide in combination with erlotuzumab is ongoing and is expected to clarify the clinical benefit of erlotuzumab in patients with relapsed myeloma compared to the results of previous lenalidomide and high-dose dexamethasone treatment studies. Other targeted antibodies: CD138 antibody daratumomab, for which clinical trials have been reported showing early, high remission rates; antibody-coupled chemotoxin (anti-CD138 – DM1 immunotoxin) is expected to significantly increase killing activity against MM; DKK- -1 antibody, MabB3, promotes osteoblast differentiation and calcium deposition in animal models while inhibiting osteoclast differentiation and trap formation ability, and BHQ880, which improves bone disease inhibits tumor growth, is in clinical trials. In addition, research on CD56 antibody and BAF antibody is also in progress.