Use of Isatuximab, Dexamethasone and Lenalidomide in a Go-Slow Fashion for Ultra-Frail Patients With Multiple Myeloma

Inclusion Criteria: * Male or female subject aged ≥ 18 years. * Histologically confirmed myeloma and/or Plasma Cell Leukemia who are newly diagnosed and having completed ≤ 1 prior cycle of myeloma treatment. * For female subjects of childbearing potential: Negative pregnancy test or evidence of post-menopausal status or evidence of permanent surgical sterilization (bilateral oophorectomy or hysterectomy). The post-menopausal status will be defined as having been amenorrheic for 24 months without an alternative medical cause. * Subjects must be willing to follow contraception requirements listed in the protocol, agree to participate in the Lenalidomide REMS program, and have signed the Patient-Physician Agreement Form. * Male subjects must agree to use a latex condom during intercourse for the duration of study therapy as described in the protocol, even if he has undergone a successful vasectomy. * Recovery to baseline or ≤ Grade 1 CTCAE v5 from toxicities related to any prior treatments, unless AE(s) are clinically nonsignificant and/or stable on supportive therapy per the treating investigator. * Able to provide informed consent and willing to sign an approved consent form that conforms to federal and institutional guidelines. * IMWG defined frailty score ≥ 3. IMWG definition available here: http://www.myelomafrailtyscorecalculator.net Exclusion Criteria: * Receiving other investigational agents. * Any condition that would, in the Investigator's judgment, compromise the subject's ability to understand the subject information, give informed consent, and/or contraindicate the subject's participation in the clinical study due to safety concerns or compliance with clinical study procedures (e.g., infection/inflammation, intestinal obstruction, unable to swallow medication, \[subjects may not receive the drug through a feeding tube\], social/ psychological issues, etc.) * Known prior severe hypersensitivity (NCI CTCAE v5.0 Grade ≥ 3) to investigational product (IP) or any component in its formulations. This includes hypersensitivity or history of intolerance to steroids, mannitol, pregelatinized starch, sodium stearyl fumarate, histidine (as base and hydrochloride salt), arginine hydrochloride, poloxamer 188, sucrose or any of the other components of study intervention that are not amenable to premedication with steroids and H2 blockers or would prohibit further treatment with these agents. * Subjects currently taking prohibited medications as described in the protocol.