FDA approves new treatment for refractory multiple myeloma

The U.S. Food and Drug Administration granted accelerated approval to Xpovio (selinexor) tablets in combination with the corticosteroid dexamethasone for the treatment of adult patients with relapsed refractory multiple myeloma (RRMM) who have received at least four prior therapies and whose disease is resistant to several other forms of treatment, including at least two proteasome inhibitors, at least two immunomodulatory agents, and an anti-CD38 monoclonal antibody.

"While there is no cure for multiple myeloma, there are FDA-approved treatments to target the cancer and slow down the spread of the disease. Sadly, often over time, patients can exhaust all available treatments and still see their disease progress," said Richard Pazdur, M.D., director of the FDA’s Oncology Center of Excellence and acting director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research. "Today we approved a treatment under our accelerated approval program that provides a treatment option for patients with multiple myeloma with no available therapy."

Multiple myeloma is cancer that begins in plasma cells (white blood cells that produce antibodies) and may also be referred to as plasma cell myeloma. Abnormal plasma cells build up in the bone marrow, forming tumors in many bones of the body. As more antibodies are made, it can cause blood to thicken and keep the bone marrow from making enough healthy blood cells. The exact causes of multiple myeloma are unknown, but it is more common in older people and African Americans.

Efficacy was evaluated in 83 patients with RRMM who were treated with Xpovio in combination with dexamethasone. At the end of the study, the overall response rate was measured at 25.3%. The median time to first response was four weeks, with a range of one to ten weeks. The median duration of response was 3.8 months. The efficacy evaluation was supported by additional information from an ongoing, randomized trial in patients with multiple myeloma.

Common side effects of patients taking Xpovio in combination with dexamethasone include a low white blood cell count (leukopenia), a low count of neutrophils, a type of white blood cell (neutropenia), low count of platelets (thrombocytopenia) and low amount of red blood cells (anemia). Patients also reported vomiting, nausea, fatigue, diarrhea, fever, decreased appetite and weight, constipation, upper respiratory tract infections and low blood sodium levels (hyponatremia).

Health care professionals are advised to monitor patients for low blood counts, platelets and sodium levels. Patients should avoid taking Xpovio with other medications that may cause dizziness or confusion and avoid situations where dizziness may be a problem. Health care professionals are advised to optimize the patient's hydration status, blood counts and other medications to avoid dizziness or confusion. The FDA advises health care professionals to tell females of reproductive age and males with a female partner of reproductive potential to use effective contraception during treatment with Xpovio. Women who are pregnant or breastfeeding should not take Xpovio because it may cause harm to a developing fetus or newborn baby. Xpovio must be dispensed with a patient Medication Guide that describes important information about the drug's uses and risks.

Xpovio in combination with dexamethasone was granted accelerated approval, which enables the FDA to approve drugs for serious conditions to fill an unmet medical need based on an endpoint that is reasonably likely to predict a clinical benefit to patients. Further clinical trials are required to verify and describe Xpovio's clinical benefit.

The FDA granted this application Fast Track designation. Xpovio also received Orphan Drug designation, which provides incentives to assist and encourage the development of drugs for rare diseases. The FDA granted the approval of Xpovio to Karyopharm Therapeutics. 

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