INCB001158 Combined With Subcutaneous (SC) Daratumumab, Compared to Daratumumab SC, in Relapsed or Refractory Multiple Myeloma

Inclusion Criteria:

* Prior diagnosis of multiple myeloma according to IMWG diagnostic criteria.
* Measurable disease at screening.
* Has received at least 3 but not more than 5 prior lines of multiple myeloma treatment, including proteasome inhibitor, immunomodulatory drug, and anti-CD38 therapies.
* Eastern Cooperative Oncology Group performance status of 0 or 1.
* Willing to avoid pregnancy or fathering children.
* Willing to provide fresh and archival bone marrow aspiration and biopsy tissue.

Exclusion Criteria:

* Receipt of any of the following treatment within the indicated interval before the first administration of study drug:

  * Anti-myeloma treatment within 2 weeks or 5 half-lives (whichever is longer).
  * Investigational drug (including investigational vaccines) or invasive investigational medical device within 4 weeks.
  * Autologous stem cell transplant within 12 weeks, or allogeneic stem cell transplant at any time.
  * Plasmapheresis within 4 weeks.
  * Radiation therapy within 2 weeks.
  * Major surgery within 2 weeks, or inadequate recovery from an earlier surgery, or surgery planned during the time the participant is expected to participate in the study or within 2 weeks after the last dose of study treatment.
* Toxicity ≥ Grade 2 from previous anti-myeloma therapy except for stable chronic toxicities (≤ Grade 2) not expected to resolve, such as stable Grade 2 peripheral neuropathy.
* Known additional malignancy (other than multiple myeloma) that is progressing or requires active treatment, or history of other malignancy within 2 years of study entry.
* Laboratory values at screening outside the protocol-defined range.
* Significant concurrent, uncontrolled medical condition including but not limited to known chronic obstructive pulmonary disease (COPD), persistent asthma, or history of asthma within the past 2 years; chronic or current active infectious disease requiring systemic antibiotics, antifungal, or antiviral treatment; acute diffuse infiltrative pulmonary disease; clinically significant or uncontrolled cardiac disease.
* Plasma cell leukemia, Waldenström's macroglobulinemia, POEMS syndrome, or amyloidosis.