Inclusion Criteria:  Age 18 or older Diagnosis of relapsed/refractory multiple myeloma corresponding to the Food and Drug Administration (FDA) package insert for isatuximab-irfc (Sarclisa®). Confirmed or planned treatment with intravenous isatuximab-irfc for relapsed/refractory multiple myeloma as standard-of-care therapy. Concurrent therapy with other agents (e.g., pomalidomide) is allowed. Access to and willingness to use a smartphone or other device through which they can send and receive text messages, emails and/or access a mobile application. Willingness to wear and have data collected by a Fitbit Ability to engage in physical activity as evidenced by an Eastern Cooperative Oncology Group (ECOG) performance status score of less than or equal to 2  Exclusion Criteria:  Individuals who are terminally ill, defined as individuals identified by their physician as likely having 6 months or less to live, or those individuals transitioned to comfort measures only (meaning only supportive care measures without curative focused treatment) Individuals for whom there is documentation of inability to provide consent in the medical record. Individuals receiving isatuximab-irfc subcutaneously