Study of Bromodomain and Extra-Terminal Protein (BET) Inhibitor RO6870810 as Mono- and Combination Therapy in Advanced Multiple Myeloma

Inclusion Criteria:

   - Performance status
   - Life expectancy > 3 months

   - Relapsed or refractory multiple myeloma. Participants with primary refractory myeloma
   only allowed in dose-escalation phase of the study.

   - Prior treatment: Treated with at least three prior lines of multiple myeloma therapy
   including a proteasome inhibitor and an immuno modulatory agent or who are double
   refractory to a proteasome inhibitor and an immuno modulatory agent. Prior anti-CD38
   antibody (e.g., daratumumab, isatuximab) treatment is acceptable only for participants
   receiving monotherapy treatment.

   - Prior treatment: Treated with two or more lines of prior therapy, with disease
   refractory to both a proteasome inhibitor and an immunomodulatory agent, and disease
   progression (as defined by International Myeloma Working Group (IMWG) criteria)
   following treatment with an anti-CD38 monoclonal antibody given as monotherapy or in
   combination therapy. The most recent treatment regimen must have contained an
   anti-CD38 monoclonal antibody.

   - Treatment with prior autologous transplant is permitted

   - Documented diagnosis of symptomatic multiple myeloma, as defined by the IMWG

   - Measurable disease defined as at least one of the following: serum M-protein >/=1
   grams/deciliter (g/dL), urine M-protein >/= 200 milligrams/24 hours (mg/24h), serum
   free light chain (SFLC) assay: involved SFLCs >/= 10 mg/dL (>/= 100 mg/L) and an
   abnormal SFLC ratio (<0.26 or >1.65).

   - Female participants of childbearing potential must have a negative serum pregnancy
   test within the 7 days prior to the first study drug administration.

   - For women of childbearing potential: agreement to remain abstinent (refrain from
   heterosexual intercourse) or use contraceptive methods that result in a failure rate
   of < 1% per year during the treatment period and for at least 2 months after the last
   dose of RO6870810 as monotherapy, or for at least 3 months after the last dose of
   daratumumab.

   - For men: agreement to remain abstinent (refrain from heterosexual intercourse) or use
   contraceptive measures and agreement to refrain from donating sperm, as defined: With
   female partners of childbearing potential or pregnant female partners, men must remain
   abstinent or use a condom during the treatment period and for at least 4 months after
   the last dose of RO6870810 as monotherapy, or for at least 3 months after the last
   dose of daratumumab.

Exclusion Criteria:

   - Plasma cell leukemia defined as peripheral plasma cell count > 2000/cubic millimeter
   (mm^3)

   - For expansion cohorts only: Primary refractory multiple myeloma defined as disease
   that is non-responsive in participants who have never achieved a minimal response or
   better with any therapy

   - History of other malignancy within 2 years prior to screening, except for ductal
   carcinoma in situ not requiring chemotherapy, appropriately treated carcinoma in situ
   of the cervix, non-melanoma skin carcinoma, low-grade, localized prostate cancer
   (Gleason score    cancer

   - POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein and
   skin changes)

   - Current or prior disease or treatment that could compromise protocol objectives in the
   opinion of the Investigator and/or the Sponsor

   - Pregnant or breastfeeding female.

   - Consumption of agents which strongly inhibit CYP3A4 enzyme, within 7 days prior to the
   first dose of study treatment and during the study.

   - Consumption of agents which strongly induce CYP3A4 enzyme, within 14 days prior to the
   first dose of study treatment and during the study.

   - Surgery within 21 days prior to study entry.

   - Prior treatment with small molecule BET family inhibitor or receiving steroids >the
   equivalent of 10mg prednisone daily

   - participants who are currently receiving any other investigational agent or have
   received an investigational agent within 30 days or 5 half-lives, whichever is longer,
   prior to study entry

   - Uncontrolled cancer pain

   - Prior anti-cancer therapy (chemotherapy, targeted agents, radiotherapy, and
   immunotherapy) within 14 days except for alkylating agents (e.g., melphalan) within 28
   days.