This is a multi-center, open-label, clinical study with Dose Escalation (Phase 1) and Expansion (Phase 2) to independently assess the MTD, efficacy , and safety of 10 combination therapies in 11 arms in patients with RRMM and NDMM. Patients will be assigned to treatment arms based on their diagnoses and treatment histories. For 9 patients, a PK Run-in period will precede Cycle 1 (DLT evaluation) to assess selinexor PK when co-administered with a strong CYP3A4 inhibitor. In the Dose Escalation Phase (Phase 1): (a) in Arm 1 (SPd), Arm 2 (SVd), and Arm 3 (SRd in RRMM), patients will be randomized to either QW or BIW selinexor dosing cohorts; (b) in Arm 5 (SDd), patients will be sequentially assigned in blocks of 3 to either QW or BIW selinexor dosing; (c) in Arm 4 (SPVd), Arm 6 (SKd), Arm 7 (Srd in NDMM), Arm 8 (SNd), Arm 9 (SPEd), Arm 10 (SBd), and Arm 11 (SDPd) patients will be assigned to QW selinexor dosing.~Cohort 1.4 is included from Version 10 to study safety and tolerability of SPd with selinexor 40 mg QW, is lower than RP2D (ie, selinexor 60 mg QW) in combination with pomalidomide 4 mg. Cohort 1.4 is a different expansion cohort from the one with RP2D (ie, Cohort 1.3). In Cohort 1.4, 20 patients will be enrolled in total.~Starting in protocol Version 8.0, patients enrolled to the Dose Escalation Phase of Arm 4 (SPVd), Arm 6 (SKd), Arm 8 (SNd), Arm 9 (SPEd), Arm 10 (SBd), and Arm 11 (SDPd) will first be enrolled to a 14-day PK Run-in period (selinexor +/- clarithromycin) until 9 patients have been enrolled. During this 14-day PK Run-in period, selinexor 40 milligrams (mg) will be administered alone on Day 1, clarithromycin 500 mg twice daily (BID) will be administered on Days 2-8, and selinexor 40 mg will again be administered on Day 8 with the morning clarithromycin dose. Blood samples for PK analysis will be collected pre-dose and 1 (± 10 min), 1.5 (± 10 min), 2 (± 10 min), 3 (± 10 min), 4 (± 10 min), 5 (± 10 min), 6 (± 10 min), 8 (± 10 min), and 24 h (± 30 min) hours after selinexor is dosed on Day 1 (without clarithromycin) and Day 8 (with clarithromycin). Patients will then proceed to the DLT evaluation period that will begin after the completion of the 14-day PK Run-in period; this day will be designated as Cycle 1 Day 1 (C1D1) in the Dose Escalation Phase.
This study will independently assess the efficacy and safety of 10 combination therapies in 11 arms, in dose-escalation/-evaluation and expansion phases, for the treatment of patients with relapsed/refractory multiple myeloma (RRMM) and newly diagnosed multiple myeloma (NDMM). The combinations to be evaluated are:~Arm 1: Selinexor + dexamethasone + pomalidomide (SPd)~Arm 2: Selinexor + dexamethasone + bortezomib (SVd); enrollment complete~Arm 3: Selinexor + dexamethasone + lenalidomide (SRd) in RRMM; enrollment complete~Arm 4: Selinexor + dexamethasone + pomalidomide + bortezomib (SPVd)~Arm 5: Selinexor + dexamethasone + daratumumab (SDd); enrollment complete~Arm 6: Selinexor + dexamethasone + carfilzomib (SKd)~Arm 7: Selinexor + dexamethasone + lenalidomide (SRd) in NDMM~Arm 8: Selinexor + dexamethasone + ixazomib (SNd)~Arm 9: Selinexor + dexamethasone + pomalidomide + elotuzumab (SPEd)~Arm 10: Selinexor + dexamethasone + belantamab mafodotin (SBd)~Arm 11: Selinexor + dexamethasone + pomalidomide + daratumumab (SDPd)~Selinexor pharmacokinetics:~PK Run-in (Days 1-14):~Starting in protocol version 8.0, patients enrolled to any arm in the Dose Escalation Phase (i.e., Arm 4 [SPVd], Arm 6 [SKd], Arm 8 [SNd], Arm 9 [SPEd], Arm 10 [SBd], and Arm 11 [SDPd]) will also first be enrolled to a pharmacokinetics (PK) Run-in period until 9 patients have been enrolled to this period to evaluate the PK of selinexor before and after co-administration with a strong CYP3A4 inhibitor.