Multiple myeloma (MM), the second most common hematological malignancy, is a clonal plasma cell disorder characterized by the secretion of monoclonal immunoglobulins. The annual incidence of newly diagnosed MM (NDMM) patients is about 2-3/100,000. In the past 20 years, the median overall survival (OS) of MM patients has prolonged from 3 to 5 years to 8 to 10 years since many novel agents developed on the pipeline of treatment. For patients with relapsed/refractory multiple myeloma, the combination of new drugs can prolong the patient's progression-free survival (PFS) and overall survival (OS). At present, guidelines recommend the use of 3-4 drugs combined with chemotherapy containing proteasome inhibitors, immunomodulators or daratumomab for the treatment of patients with relapsed and refractory multiple myeloma treatment.

Bortezomib combined with lenalidomide and dexamethasone (VRd) is the first-line induction program recommended by guidelines; It has been widely used in the first-line treatment of MM patients. Therefore, when the disease relapses, the VRd regimen is not effective again. Research data shows that the second-generation oral proteasome inhibitor drug ixazomib combined with lenalidomide and dexamethasone (IxaRd) is used to treat the disease. In the treatment of RRMM patients, the progression-free survival period was significantly better than that of the lenalidomide and dexamethasone groups, and at the same time, it did not significantly increase the adverse reactions. The second-generation PI drug, Ixazomib, was approved in China in May 2018 and is widely used in RRMM patients. In addition, because most patients with multiple myeloma use lenalidomide in the first-line treatment and maintenance treatment, a large proportion of RRMM patients are resistant to lenalidomide. Pomalidomide, the third-generation oral immunomodulator drug, can overcome lenalidomide resistance and has better safety in patients with renal insufficiency MM. The results of clinical trials confirmed that pomalidomide combined with a proteasome inhibitor and dexamethasone is better than a dual-drug regimen of pomalidomide and dexamethasone in RRMM patients. A convenient and safe full oral regimen, that is, ixazomib combined with pomalidomide and dexamethasone (IxaPd) is expected to improve the efficacy and survival of RRMM patients. The purpose of this study was to evaluate the efficacy and safety of a three-drug oral regimen of ixazomib, pomalidomide and dexamethasone in patients with relapsed MM who have received lenalidomide.

At the screening visit, informed consent will be obtained from all subjects who are deemed potentially eligible for enrollment in the study, according to the protocol-specified inclusion and exclusion criteria.Eligible patients are receive treatment IxaPD. Ixazomib 4 mg, capsules, orally, once on Days 1, 8 and 15 of every 28-day cycle , pomalidomide 25mg qd day 1\~21 of every 28-day cycle, Dexamethasone 40 mg (20 mg for patients \>75 years of age) was given on days 1, 8, 15, and 22 of every 28-day cycle. Treatment was continued until disease progression, unacceptable toxicity.Progression free survival, overall survival, time to next treatment, overall response rate and safety issues will be recorded. Drug doses will be adjusted or withdrawn based on the degree of toxicities.