Ex vivo drug sensitivity screening in multiple myeloma identifies drug combinations that act synergistically

Abstract

The management of multiple myeloma (MM) is challenging: An assortment of available drug combinations adds complexity to treatment selection, and treatment resistance frequently develops. Given the heterogeneous nature of MM, personalized testing tools are required to identify drug sensitivities. To identify drug sensitivities in MM cells, we established a drug testing pipeline to examine ex vivo drug responses. MM cells from 44 patients were screened against 30 clinically relevant single agents and 44 doubleand triple-drug combinations. We observed variability in responses across samples. The presence of gain(1q21) was associated with low sensitivity to venetoclax, and decreased ex vivo responses to dexamethasone reflected the drug resistance observed in patients. Less heterogeneity and higher efficacy was detected with many combinations compared to the corresponding single agents. We identified new synergistic effects of melflufen plus panobinostat using low concentrations (0.1-10 nM and 8 nM, respectively). In agreement with clinical studies, clinically approved combinations, such as triple combination of selinexor plus bortezomib plus dexamethasone, acted synergistically, and synergies required low drug concentrations (0.1 nM bortezomib, 10 nM selinexor and 4 nM dexamethasone). In summary, our drug screening provided results within a clinically actionable 5-day time frame and identified synergistic drug efficacies in patient-derived MM cells that may aid future therapy choices.

Phenotypic deconvolution in heterogeneous cancer cell populations using drug screening data

“…A: Illustration of the experimental protocol described in Methods 26 , created using smart.servier.com and biorender.com. B-G: Deconvolution results for 5 MM samples, each exposed to 4 out of 6 drugs: B: Dexamethasone, C: Selinexor, D: Melflufen, E: Venetoclax, F: Ixazomib, G: Thalidomide.…”

“…24,25 Bone marrow samples were taken from each patient, processed, and screened with a set of MM clinically-relevant drugs, as illustrated in Figure 3A and described in the STAR methods section. 26 To perform the drug screens, samples from each patient were subjected to treatment at varying concentrations with a subset of the following drugs: Dexamethasone, Ixazomib, Melflufen, Selinexor, Thalidomide, and Venetoclax. We note that screening data for all drugs for each patient was not available; Figure 3B-G shows the set of patient samples treated by each drug and summarizes the results of PhenoPop deconvolution analysis on each set of drug screen data.…”

“…Drug sensitivity assay CD138+ MM cells (200,000 cells/mL) derived from activation assays were treated with drugs at 9 concentrations using a drug customized concentration range (0,1-10,000), as described in Giliberto et al 26 The drug panel included clinically relevant anti-myeloma drugs, Dexamethasone (0,1-10,000), ixazomib (1-10,000), thalidomide (0,1-10,000), selinexor (0,1-1000), melflufen (0,1-1000) and venetoclax (0,1-10,000). Pre-printed drug plates were made by an acoustic dispenser (Echo 550, LabCyte Inc., San Jose, CA, USA), by the Chemical Biology Platform, NCMM, University of Oslo.…”

Selinexor: Targeting a novel pathway in multiple myeloma

“…Synergistic effects were seen in combination with dexamethasone via the induction of GR expression and inhibition of the mammalian target of rapamycin pathway in MM cells [41], as well as in ex vivo primary MM cells, with MYC‐regulated genes associated with sensitivity to the combination [40]. Selinexor also results in synergistic antimyeloma activity in combination with PIs, potentially via the mechanism of nuclear localization of IκB and the resultant inhibition of NF‐κB activity [42, 43]; specific activity has been demonstrated in combination with both bortezomib [38, 44] and carfilzomib [45], with the latter associated with mechanisms including a reduction in expression of the pro‐survival protein B‐cell lymphoma 2 (Bcl‐2) and induction of caspase‐10‐dependent apoptosis. Other combinations with synergistic activity in preclinical studies include selinexor plus pomalidomide [40], the conventional MM chemotherapy drugs melphalan [46] and doxorubicin [47], the latter mediated through inhibition of nuclear export of topoisomerase II alpha and the resultant doxorubicin‐induced DNA damage, and the investigational pan‐RAF (rapidly accelerated fibrosarcoma) inhibitor TAK‐580 [48], with synergistic effects mediated by the FOXO3a (forkhead box O3)‐Bim (Bcl‐2 interacting mediator of cell death) signalling pathway.…”

“…Synergistic effects were seen in combination with dexamethasone via the induction of GR expression and inhibition of the mammalian target of rapamycin pathway in MM cells [41], as well as in ex vivo primary MM cells, with MYC-regulated genes associated with sensitivity to the combination [40]. Selinexor also results in synergistic antimyeloma activity in combination with PIs, potentially via the mechanism of nuclear localization of IκB and the resultant inhibition of NF-κB activity [42,43]; specific activity has been demonstrated in combination with both bortezomib [38,44] and carfilzomib [45], with the latter associated with mechanisms including a reduction in expression of the pro-survival protein B-cell lymphoma 2 (Bcl-2) and induction of caspase-10-dependent apoptosis. Other combinations with synergistic activity in preclinical studies include F I G U R E 2 US FDA and EMA approvals of selinexor in relapsed/refractory multiple myeloma.…”