A Study to Learn About the Study Medicine Elranatamab Alone and With Daratumumab in People With Multiple Myeloma Who Have Received Other Treatments

Inclusion Criteria:

* Prior diagnosis of multiple myeloma as defined by IMWG criteria (Rajkumar et al, 2014).
* Measurable disease based on IMWG criteria as defined by at least 1 of the following:

  * Serum M-protein ≥0.5 g/dL.
  * Urinary M-protein excretion ≥200 mg/24 hours.
  * Serum immunoglobulin FLC ≥10 mg/dL (≥100 mg/L) AND abnormal serum immunoglobulin kappa to lambda FLC ratio (\<0.26 or \>1.65).
* Prior anti-multiple myeloma therapy including treatment with lenalidomide.
* ECOG performance status ≤2.
* Resolved acute effects of any prior therapy to baseline severity or CTCAE Grade ≤1.
* Not pregnant and willing to use contraception.

Exclusion Criteria:

* Smoldering multiple myeloma.
* Plasma cell leukemia.
* Amyloidosis.
* POEMS Syndrome.
* Stem cell transplant within 12 weeks prior to enrolment, or active graft versus host disease.
* Active HBV, HCV, SARS-CoV2, HIV, or any active, uncontrolled bacterial, fungal, or viral infection.
* Any other active malignancy within 3 years prior to enrolment, except for adequately treated basal cell or squamous cell skin cancer, or carcinoma in situ.
* Previous treatment with a BCMA-directed therapy.
* Live attenuated vaccine within 4 weeks of the first dose of study intervention.
* Administration with an investigational product (e.g. drug or vaccine) concurrent with study intervention or within 30 days preceding the first dose of study intervention used in this study.