Inclusion Criteria:

* Age ≥ 18 years
* RRMM with measurable disease prior to initiation of study intervention. Measurable disease must include at least one of the following criteria:

* Serum M-protein \> 0.5 g/dL or,
* Urine M-protein \> 200 mg/24h or,
* Serum free light chain assay: involved free light chain (FLC) level \> 100 mg/L provided serum free light chain ratio is abnormal or,
* Bone marrow plasma cells \> 10% of total bone marrow cells
* Have received ≥ 1 prior line of therapy
* Planned treatment with the standard of care regimen of daratumumab, carfilzomib, and dexamethasone (Dara-KD) regimen
* Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2
* Absolute neutrophil count: ≥ 1,000 /µL
* Platelets: ≥ 75,000 /µL
* Hemoglobin: ≥ 7 g/dL
* Total bilirubin: ≤ 1.5 x upper limit of normal (ULN): ≤ 3.0 x ULN for Gilbert's Syndrome
* Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase \[SGOT\])/alanine aminotransferase (ALT) (serum glutamic pyruvic transaminase \[SGPT\]): ≤ 3 x ULN
* Estimated glomerular filtration rate (eGFR) ≥ 30 mL/min
* Left ventricular ejection fraction of at least 50% by ECHO or MUGA
* Participants of child-bearing potential must agree to use adequate contraceptive methods (e.g., hormonal or barrier method of birth control; abstinence) prior to study entry and for 6 months following the last dose of the investigational drug. Should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she should inform her treating physician immediately
* Participants must understand the investigational nature of this study and sign an Independent Ethics Committee/Institutional Review Board approved written informed consent form prior to receiving any study related procedure

Exclusion Criteria:

* Known hypersensitivity to selvigaltin or any of the excipients
* Prior hypersensitivity or grade 3 skin toxicity with daratumumab/carfilzomib
* Exposure to prior daratumumab/carfilzomib is permitted, however refractoriness within 6 months of study initiation is exclusionary
* Concomitant medication(s) known to be (a) a strong inhibitor or inducer of CYP3A4, (b) strong P-gp/MDRI inhibitors or inducers or, (c) QT interval (QT) prolonging as defined in the drug's label, with the exception of drugs that are considered absolutely essential for the care of the subject or if the Investigator believes that beginning therapy with such medication is vital to an individual subject's care while on study, and in either case, there is no alternative medication
* Electrocardiogram (ECG) demonstrating a corrected QT interval (QTc) interval \> 470 msec without a bundle block or patients with congenital long QT syndrome
* Coronary artery bypass, angioplasty, vascular stent, myocardial infarction, angina or congestive heart failure in the last 6 months
* Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, class III or IV heart failure (New York Heart Association functional classification system), or psychiatric illness/social situations that would limit compliance with study requirements
* Known active bacillus tuberculosis infection
* Known active HIV unless CD4+ \> 350 cells/µL, no history of AIDS-defining opportunistic infection within the past 12 months, or on effect anti-retroviral therapy (ART) with \> 4 weeks on treatment and viral load \< 400 copies/mL. Confirm low risk of drug-drug interactions or are able to be substituted
* Pregnant or nursing female participants
* Any condition which in the investigator's opinion deems the participant an unsuitable candidate to receive study drug