Selinexor (KPT-330) and Liposomal Doxorubicin For Relapsed and Refractory Multiple Myeloma

Selinexor orally as outlined in the study treatment arm.

Pegylated liposomal doxorubicin at a starting dose of 20 mb/m² as outlined in the treatment arm.

Participants will be instructed to take Dexamethasone 40 mg (10 tablets) orally once weekly with meals (ideally with breakfast to minimize insomnia). Participants older than 75 years and patients previously intolerant to 40 mg dosage will be allowed to receive 20 mg (5 tablets) once a week.