Lenalidomide, sold under the trade name Revlimid among others, is a medication used to treat multiple myeloma, smoldering myeloma, and myelodysplastic syndromes (MDS). For multiple myeloma, it is used after at least one other treatment and generally with dexamethasone. It is taken by mouth. Common side effects include diarrhea, itchiness, joint pain, fever, headache, and trouble sleeping. Severe side effects include low blood platelets, low white blood cells, and blood clots. Use during pregnancy may harm the fetus. The dose may need to be adjusted in people with kidney problems. It has a chemical structure similar to thalidomide but has a different mechanism of action. How it works is not entirely clear as of 2019. Lenalidomide was approved for medical use in the United States in 2005. It is on the World Health Organization's List of Essential Medicines. Lenalidomide is used to treat multiple myeloma. It is a more potent molecular analog of thalidomide, which inhibits tumor angiogenesis, tumor-secreted cytokines, and tumor proliferation through induction of apoptosis. Lenalidomide is effective at inducing a complete or "very good partial" response and improves progression-free survival. Adverse events more common in people receiving lenalidomide for myeloma include neutropenia, deep vein thrombosis, infections, and an increased risk of other hematological malignancies. The risk of second primary hematological malignancies does not outweigh the benefit of using lenalidomide in relapsed or refractory multiple myeloma. It may be more difficult to mobilize stem cells for autograft in people who have received lenalidomide. In 2006, lenalidomide received U.S. Food and Drug Administration (FDA) clearance for use in combination with dexamethasone in people with multiple myeloma who have received at least one prior therapy. In 2017, the FDA approved lenalidomide as standalone maintenance therapy (without dexamethasone) for people with multiple myeloma following autologous stem cell transplant.