Dose-Escalation Study of ABBV-838, an Antibody Drug Conjugate, in Subjects With Relapsed and Refractory Multiple Myeloma

Inclusion Criteria:

Eastern Cooperative Oncology Group Performance Status of 0 to 2
Not eligible for stem cell/bone marrow transplant or have refused stem cell/bone marrow transplant or have relapsed after autologous or allogeneic stem cell/bone marrow transplant
Eligible for and agree to BM aspirate prior to treatment start
Measurable disease M component in serum (≥ 0.5 g/dL) and/or urine (≥ 0.2 g excreted in a 24 hour collection sample)
Must have received at least 3 prior lines of therapy including a proteasome inhibitor and an immunomodulatory agent or those who are double refractory to a PI and an immunomodulatory agent and have demonstrated disease progression (DP) on or within 60 days of completion of the last therapy; participants previously treated with an alkylating agent, in addition to an IMiD or proteasome inhibitor, are allowed to enroll in the trial
Participants must have adequate liver, kidney, and bone morrow function
Participants with a history of chronic heart failure must have cardiac ECHO indicating left ventricular ejection fraction (LVEF) ≥ 45% within 21 days prior to first dose of study drug
Participants in the combination therapy arms must be eligible to receive pomalidomide/dexamethasone, bortezomib/dexamethasone or lenalidomide/dexamethasone or other approved agents per current prescribing information for MM.
Participants who will receive combination therapy with Pomalidomide/Dexamethasone must have received at least two prior therapies including lenalidomide and a proteasome inhibitor and have demonstrated disease progression on or within 60 days of completion of the last therapy

Exclusion Criteria:

Received anti-cancer therapy including chemotherapy, immunotherapy, radiation, biologic, any investigational therapy or herbal therapy within a period of 21 days prior to the first dose of ABBV-838, and have unresolved toxicities ≥ grade 2
Concurrent metastatic solid tumors
Non-Measurable M Protein (serum or urine) and measurable sFLC (< 100 mg/mL)
Major surgery within 21 days prior to the first dose of ABBV-838
Clinically significant uncontrolled condition(s) including but not limited to the following:

Grade ≥ 3 peripheral neuropathy or grade 2 peripheral neuropathy with pain Uncontrolled hypercalcemia Active uncontrolled infection Symptomatic congestive heart failure Unstable angina pectoris or cardiac arrhythmia Psychiatric illness/social situation that would limit compliance with the study

Major immunologic reaction to any IgG containing agent or auristatin based agent
Participants who are taking strong CYP3A4 inhibitors
Positive for HIV (Human Immunodeficiency Virus) or with active hepatitis B and/or C
Corneal pathology that would limit evaluation of loss in visual acuity associated with corneal deposits.
Prior exposure to pomalidomide for subjects enrolling in the pomalidomide/dexamethasone combination arm.