Therapeutic Agent For Multiple Myeloma Research Articles

Predictors of response to venetoclax and therapeutic potential of CDK7 inhibition in multiple myeloma

AbstractVenetoclax, a selective BCL2 inhibitor, has emerged as a promising therapeutic agent for multiple myeloma (MM), particularly in patients harboring the t(11;14) translocation. In this study, we set out to identify markers of sensitivity and resistance to venetoclax in a real-world patient population, aiming to facilitate the development of personalized therapeutic strategies. Through the analysis of RNA-seq data from relapsed/refractory patients treated with venetoclax, either as a single agent or in combination with other drugs, we unveiled a novel 6-gene signature that significantly stratified patients into risk groups for relapse and further validated its clinical relevance in 2 independent clinical and ex vivo data sets. Our analysis also highlighted the negative impact of chromosome 1q gain, which harbors the MCL1 gene, on progression-free survival, even in t(11;14)-positive patients. Encouraged by the well-documented role of MCL1 in resistance to venetoclax in various malignancies and the prognostic importance of the BCL2/MCL1 ratio in our cohort, we explored Cyclin-Dependent Kinase 7 (CDK7) inhibition as a potential strategy to overcome venetoclax resistance. In vitro experiments demonstrated that CRISPR-Cas9–mediated CDK7 depletion led to decreased MCL1 levels, enhancing the sensitivity of MM cells to venetoclax. Moreover, the combination of the CDK7 inhibitor THZ1 with venetoclax markedly induced cell death in venetoclax-resistant MM cells harboring 1q gain, thus offering a rational therapeutic approach, particularly for patients with this aberration. Overall, these findings provide important insights for optimizing venetoclax-based therapeutic strategies in MM.

The importance of removing interference caused by Darzalex® (daratumumab) in pre-transfusion testing

Introduction: Multiple myeloma (MM) is a hematologic malignacy characterized by the uncontrolled proliferation of abnormal plasma cells in the bone marrow. Darzalex® (daratumumab) has emerged as a highly effective therapeutic agent for MM, offering an additional treatment option for patients who have developed resistance to other therapies. However, the use of Darzalex® poses challenges in pre-transfusion testing due to its strong binding affinity of the monoclonal anti-CD38 antibody to CD38 protein, resulting in panreactivity with test erythrocytes and complicating the detection of erythrocyte alloantibodies. The objective of this case report is to outline the procedures, significance, and methodologies for mitigating this interference using the DaraEx® reagent. Case Report: We present the cases of three patients diagnosed with MM and treated with Darzalex® at our institution in 2023. Following the administration of Darzalex®, all three patients exhibited positive results on indirect antiglobulin tests (IAT). Cross-matching tests conducted with red blood cell concentrates also yielded positive results, with strengths ranging from 2+ to 3+. To eliminate interference, we used a specific DaraEx® reagent that utilizes Fab fragments of anti-CD38 to mitigate interference by masking CD38 on the cell surface. Subsequent application of this reagent resulted in negative IAT results for all three patients. However, one patient still displayed a weakly positive cross-matching test (<1+), suggesting that complete elimination of interference may not always be achievable with the DaraEx® method. Conclusion: Despite the availability of reliable methods such as dithiothreitol and the DaraEx® reagent for mitigating interference, complete success in eliminating interference remains elusive. This underscores the importance of implementing proactive measures to prevent interference. Patients undergoing Darzalex® therapy should undergo comprehensive immunohematological testing before medication administration. Given the increased need for blood transfusions in MM patients, ensuring the compatibility of blood products is essential for safe transfusion practices.

Novel c-Myc G4 stabilizer EP12 promotes myeloma cytotoxicity by disturbing NF-κB signaling

Multiple myeloma (MM) is a B-cell malignancy characterized by the excessive proliferation of bone marrow plasma cells and the production of abnormal immunoglobulins. Despite advances in therapeutic strategies, it remains an incurable disease. Recently, innovative anticancer drugs have been developed and approved, leading to improvements in MM therapy; however, drug resistance continues to be a major obstacle that results in treatment failure. Therefore, the development of novel agents is imperative to achieve superior therapeutic outcomes for relapsed/refractory multiple myeloma (MM) patients. Previously, we identified EP12 as a c-Myc G4 stabilizer that could induce cytotoxicity in MM cells in vitro. However, further investigation is required to elucidate the underlying molecular mechanisms and anti-MM activity of EP12 in vivo. In this study, we have discovered that the compound EP12 effectively inhibits primary myeloma growth in vivo by destabilizing c-Myc and disrupting the canonical nuclear factor-κB (NF-κB) signaling pathway. Overall, our findings suggest that EP12, as a potent c-Myc inhibitor, holds great promise as a therapeutic agent for MM.

Shikonin induces ferroptosis in multiple myeloma via GOT1-mediated ferritinophagy.

Multiple myeloma (MM) is an incurable hematological malignancy that lacks effective therapeutic interventions. Ferroptosis is a newly discovered form of cell death that has shown great potential for MM therapy. As a proteasome inhibitor and necroptosis inducer, shikonin (SHK) performs dual functions in MM cells. However, whether SHK inhibits the development of MM via ferroptosis or any other mechanism remains elusive. Here, we provide evidence that SHK treatment was capable of inducing ferroptosis and immunogenic cell death (ICD) in MM. The results showed that SHK treatment induced lactate dehydrogenase release, triggered cell death, evoked oxidative stress, and enhanced ferrous iron and lipid peroxidation levels. Furthermore, treatment with ferroptosis inhibitors reversed SHK-induced cell death, which indicated that ferroptosis contributed to this phenomenon. Meanwhile, ferroptosis was accompanied by the extracellular release of Adenosine 5'-triphosphate (ATP) and High mobility group protein B1 (HMGB1), which are characteristics of ICD. Further investigation showed that glutamic-oxaloacetic transaminase 1 (GOT1) acted as a critical mediator of SHK-induced ferroptosis by promoting ferritinophagy. In conclusion, our findings suggest that SHK exerts ferroptotic effects on MM by regulating GOT1-mediated ferritinophagy. Thus, SHK is a potential therapeutic agent for MM.

Thrombosis in multiple myeloma: risk stratification, antithrombotic prophylaxis, and management of acute events. A consensus-based position paper from an ad hoc expert panel.

The introduction of new therapeutic agents for multiple myeloma (MM), including proteasome inhibitors, immunomodulatory drugs, and monoclonal antibodies, has improved the outcomes of patients but, in parallel, has changed the frequency and epidemiology of thrombotic events. Thrombosis is now a significant cause of morbidity and mortality in MM patients, and optimal thromboprophylaxis is far from being reached. Moving from the recognition that the above issue represents an unmet clinical need, an expert panel assessed the scientific literature and composed a framework of recommendations for improving thrombosis control in patients who are candidates for active treatment for MM. The panel generated key clinical questions using the criterion of clinical relevance through a Delphi process. It explored four domains, i.e., thrombotic risk factors and risk stratification, primary thromboprophylaxis, management of acute thrombotic events, and secondary thromboprophylaxis. The recommendations issued may assist hematologists in minimizing the risk of thrombosis and guarantee adherence to treatment in patients with MM who are candidates for active treatment.

Histone arginine methyltransferase CARM1 selective inhibitor TP-064 induces apoptosis in endometrial cancer

Histone modification is the key epigenetic mechanism that regulates gene expression. Coactivator-associated arginine methyltransferase 1 (CARM1) is an arginine methyltransferase that catalyzes dimethylation of histone H3 (H3R17) at arginine 17. Lately, it has been suggested that CARM1 is associated with human carcinogenesis, and the CARM1-selective inhibitor, TP-064, has been shown to be a potential therapeutic agent for multiple myeloma. However, the physiological significance of CARM1 in endometrial cancer remains unclear. Therefore, we aimed to explore the role of CARM1 and the effect of TP-064 in endometrial cancer. To this end, we analyzed CARM1 expression in endometrial cancer using quantitative real-time polymerase chain reaction and examined the antitumor mechanism with CARM1 knockdown endometrial cancer cells. Moreover, we evaluated the therapeutic capability of TP-064 in endometrial cancer cells. CARM1 was remarkably overexpressed in 52 endometrial cancer tissues compared to normal endometrial tissues. The growth of CARM1 knockdown endometrial cancer cells was suppressed and CARM1 knockdown induced apoptosis. TP-064 also inhibited endometrial cancer cell growth and declined the number of endometrial cancer cell colonies. These data suggest that CARM1 may be a powerful therapeutic target for endometrial cancer.

Disruption of Lipid Raft Microdomains, Regulation of CD38, TP53, and MYC Signaling, and Induction of Apoptosis by Lomitapide in Multiple Myeloma Cells

Multiple myeloma (MM) is characterized by accumulation of a malignant clone of plasma cells in the bone marrow. Curative treatments are not yet available. Therefore, we undertook a drug repurposing approach to identify possible candidates from a chemical library of 1,230 FDA-approved drugs by virtual drug screening. As a target, we have chosen the non-receptor Bruton's tyrosine kinase (BTK) which is one of the main regulators of the MM biomarker CD38. In silico virtual screening was performed by using PyRx. Flow cytometry was applied for cell cycle and apoptosis analysis. Furthermore, protein and gene expression was determined by western blotting and microarray hybridization. Lipid raft staining was observed by confocal microscopy. The in silico identified lipid-lowering lomitapide presented with the strongest cytotoxicity among the top 10 drug candidates. This drug arrested the cell cycle in the G2/M phase and induced apoptosis in MM cells. Western blot analyses revealed that treatment with lomitapide induced cleavage of the apoptosis regulator PARP and reduced the expression of CD38, an integral part of lipid rafts. Using confocal microscopy, we further observed that lipid raft microdomain formation in MM cells was inhibited by lomitapide. In four MM cell lines (KMS-12-BM, NCI-H929, RPMI-8226, and MOLP-8) treated with lomitapide, microarray analyses showed not only that the expression of CD38 and BTK was down-regulated, but also that the tumor suppressor gene TP53 and the oncogene c-MYC were among the top deregulated genes. Further analysis of these data by Ingenuity pathway analysis (IPA) suggested that lomitapide interferes with the cross-talk of CD38 and BTK and apoptosis-regulating genes via TP53 and c-MYC. Lomitapide treatment led to disruption of lipid raft domains and induction of pro-apoptotic factors and might, therefore, be considered as a potential therapeutic agent in MM.

Serum Bcma May Interfere with Anti-Bcma-CAR-Transduced T Cells or Other Anti-Bcma Antibody-Based Immunotherapy in Multiple Myeloma

Introduction: CAR T cell-based immunotherapy has shown clinical activity in a variety of B-cell malignancies. Specifically, the engineered CAR-transduced T cells targeting B-cell maturation antigen (BCMA) on multiple myeloma (MM) have shown promising activity for the treatment of relapsed/refractory (RR) MM patients. However, MM patients have high levels of solubilized BCMA (sBCMA) in the blood especially those with RR disease. Due to these findings, we hypothesized that circulating levels of sBCMA may interfere with the efficacy of CAR T cell immunotherapy or other anti-BCMA antibody (Ab)-based therapeutic approaches for treating MM patients.Study design: Sera were collected from MM patients and healthy subjects after obtaining institutional review board approval (IRB). Serum levels of human BCMA were determined using an ELISA kit (R&D Systems, Minneapolis, MN). For the BCMA antibody binding assay, 50 µL of human BCMA fluorescein-conjugated polyclonal Ab or monoclonal Ab was incubated with 100 µL of diluent buffer and 100 µL of serum from human subjects with varying sBCMA concentrations. To demonstrate the effects of sBCMA interference with anti-BCMA CAR T function, we utilized a wide range of concentrations (0ng/ml, 3ng/ml, 18 ng/mL, 32ng/ml, 37ng/ml, 110ng/ml, 156ng/ml, 390ng/ml, 530ng/ml and 2167 ng/mL); recombinant BCMA (0ng/ml, 65ng/ml, 130ng/ml, 400ng/ml, 1200ng/ml). After one hour of incubation at room temperature (RT), each sample was added to primary tumor cells from MM patients with progressive disease. These cells were incubated for two hours at RT away from light. Following incubation, cells were washed three times using PBS. Flow cytometric analysis was performed using a Beckman Coulter Cytomics FC 500 with Cytomics CXP software. The same procedure was followed to observe the effects of recombinant human BCMA. To assess immunofluorescent (IFC) analysis of anti-BCMA binding to MM tumor cells, IFC staining was completed following a standard IFC assay protocol and the BCMA binding markers were identified under the microscope (Olympus BX51).Results and discussion: The experimental results demonstrate a concentration dependent response of anti-BCMA antibody binding to primary MM tumor cells. At sBCMA levels lower than 150ng/mL, there was no significant difference in anti-BCMA antibody binding to tumor cells. However, at concentrations greater than 150 ng/mL, a significant decrease in binding was observed. At 390ng/ml, serum sBCMA blocked 50% of anti-BCMA antibody binding to the tumor cells. At 2000ng/ml, serum sBCMA interfered with anti-BCMA antibody binding to tumor cells by more than 80%. When using recombinant BCMA, we observed the same concentration dependent effects on anti-BCMA binding to MM cells. As the levels of recombinant BCMA increased, the antibody binding to MM cells decreased. These results suggest that higher BCMA levels that are present in patients with MM interfere with binding to MM tumor cells; and, thus, could reduce the efficacy of CAR T cell and other immunotherapy approaches targeting BCMA. The fluorescent image further demonstrated serum sBCMA blocked anti-BCMA antibody binding to primary MM tumor cells in a concentration dependent fashion. In 2013 Carpenter et al . showed that sBCMA levels do not interfere with CAR-T-cells. However, the sBCMA concentrations used in those experiments are based on low sBCMA levels (10ng/ml). We have consistently detected concentrations much higher than 150ng/ml of sBCMA in MM patients. Our experimental data showed 30-35% serum BCMA level was above 150ng/ml in 500 MM serum samples and 50% serum BCMA level was above 150ng/ml in relapsed/refractory patients.Conclusion: The results demonstrated that higher serum sBCMA concentrations do interfere with anti-BCMA antibody directed CAR T cells immunotherapy therapies or any anti-BCMA antibody therapeutic agents in MM. We suggest determining serum sBCMA level before anti-BCMA antibody directed CAR T cells immunotherapy therapy or use of any anti-BCMA antibody therapeutic agents. DisclosuresBerenson:OncoTracker, Inc.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Research Funding.

Unbiased Phosphoproteomics Reveals a Therapeutically Relevant Connection between Pre-mRNA Splicing and Proteasome Inhibition in Multiple Myeloma

Introduction: Proteasome inhibitors (PIs) are first-line therapeutic agents in multiple myeloma. While these small molecules have revolutionized myeloma therapy, nearly all myeloma patients treated with PIs eventually experience drug resistance and relapse. We have previously examined the global effects of PIs on the transcriptional and translational landscape of multiple myeloma plasma cells (Wiita et al, eLife (2013) 2:01236). Here, we hypothesized that investigation into the intracellular signaling response to PI-induced stress would help elucidate additional PI mechanisms of action in this cancer.Methods: We applied an unbiased phosphoproteomic screen to MM.1S myeloma cells treated with the PI carfilzomib across a 24-hour time course. We used trypsin digestion, FeCl2 enrichment, and a single-shot 4-hour LC method on each sample harvested at each time point on a Thermo Q-Exactive Plus mass spectrometer, with phosphopeptide identification and label-free quantification performed in MaxQuant. Targeted mass spec was then performed for validation on a subset of upregulated and downregulated phosphosites by parallel reaction monitoring (PRM) on SILAC-labeled, carfilzomib treated MM.1S cells, as well as another multiple myeloma cell line, AMO1, at 24 hr of treatment. MM.1S cells were also treated with another multiple myeloma therapeutic agent, melphalan, to compare the response to a non-PI drug. Analysis was carried out in Skyline. For paired-end mRNA-seq, we constructed sequencing libraries from the SILAC samples and sequenced on an Illumina HiSeq4000 and analyzed with JuncBASE software to correlate changes in splicing factor phosphorylation with alternative splicing events. In vitro viability studies of myeloma cell lines were carried out with Cell-titer-glo assay. For in vivo studies, we used disseminated murine xenograft models of luciferase-labeled MM.1S implanted intravenously into NSG mice, with tumor burden measured by bioluminescence. Mice (n=6 per arm) were treated with 3 mg/kg E7107 or DMSO IV 5d/wk for 2 wks.Results: Among the more than 5,000 phosphopeptides quantified in the phosphoproteomic screen, the most profoundly upregulated phosphosites mapped to numerous serine-and-arginine rich (“SR”) core components of the pre-mRNA spliceosome (Fig. 1A: upregulated phosphosites across time course in gold; downregulated in cyan. Red arrows indicate SR protein phosphosites; green arrows are positive control phosphosites on EIF4EBP1 and RPS6, known to decrease after PI treatment.). These targets were confirmed by targeted mass spec, while simultaneous mRNA-seq confirmed no change in splicing factor abundance in response to PI (Fig. 1A). Intriguingly, intron retention appeared to be a dominant signature in pre-mRNA splicing after PI treatment based on JuncBASE analysis. This connection led us to investigate whether induction of intron retention may be sufficient to lead to myeloma tumor cell death. We therefore obtained the clinical candidate E7107, a specific inhibitor of the core spliceosome factor SF3B1, known to strongly induce intron retention across the transcriptome. We found that a panel of myeloma cell lines were highly sensitive to E7107 at low nanomolar concentrations, which are easily achievable in patients based on prior Phase I studies. We further found evidence of synergy in vitro between E7107 and PI treatment, and E7107 was equally efficacious in naïve and PI-resistant AMO1 cells. Furthermore, pre-clinical experiments in murine xenograft models with a brief two-week treatment with E7107 significantly decreased tumor burden and significantly increased lifespan (Fig 1B).Conclusion: Our approaches here reveal a novel connection between PI-induced stress and modulation of the core spliceosome machinery not previously observed in any other system. By capitalizing on this vulnerability, we further propose that targeting the spliceosome machinery may be a novel therapeutic option for multiple myeloma patients, either in combination with PIs or in the PI-refractory setting, addressing a major clinical need. [Display omitted] DisclosuresWiita:Sutro Biopharma: Research Funding; TeneoBio, Inc.: Research Funding.

A Novel Aryl-Guanidinium Based Compound Targets the STAT3 Signalling Pathway, Downregulates MCL-1 Expression and Induces Anti-Myeloma Activity

Multiple myeloma (MM) is a hematological malignancy characterized by the proliferation of malignant plasma cells in the bone marrow microenvironment. Increased understanding of the pathophysiology of MM and advances in therapeutics have led to an increased survival of patients in the past decade. However, despite the effectiveness of the first-line treatments, patients invariably relapse and become drug refractory due to genetic heterogeneity and induction of prosurvival signalling cascades in the bone marrow microenvironment. There is, therefore, a need for novel therapeutics which target key prosurvival signalling pathways in MM. The Janus kinase (JAK)/Signal transducer and activator of transcription 3 (STAT3) pathway in MM can be both constitutively active due to autonomous mutations or activated by growth and survival factors, such as interleukin-6 (IL-6), secreted by bone marrow stromal cells and other cells within the bone marrow microenvironment. STAT3 is upregulated in MM and increases the expression of genes involved proliferation, angiogenesis and evasion of apoptosis. STAT3 target genes include prosurvival BCL2 family members, such as MCL-1 which is overexpressed in MM, leading to apoptosis resistance and is associated with shorter patient survival. Several studies have shown promise in targeting prosurvival BCL2 family members with BCL2 homology domain 3 (BH3) mimetics in MM. We have previously described a member of a series of guanidinium based compounds which inhibits BRAF, a serine/threonine kinase component of the RAS/ERK signalling pathway, through a putative type-III allosteric mechanism [Diez-Cecilia et al, (2015) Bioorg. Med. Chem. Lett. 25, 4287-4292]. Here, we describe a new derivative of this series, VP79s, which exhibits cytotoxicity in MM cell lines with IC50 values in the low micromolar range; however, VP79s does not inhibit RAS/ERK signalling suggesting a novel mechanism of action. VP79s was found to induce apoptosis in NCI-H929 and U266B1 MM cell lines in a dose- and time-dependent manner. VP79s was more potent in inducing cell death in a panel of drug sensitive and drug resistant MM cell lines compared to standard and emerging therapeutic agents for MM. VP79s rapidly inhibited both constitutively active and IL-6-induced STAT3 signalling in MM cells. Examination of upstream mediators of STAT3 signalling suggested a mechanism for VP79s inhibition of STAT3 activation via inhibition of JAK2 phosphorylation and downregulation of the IL-6 receptors, CD126 and CD130. Analysis of downstream STAT3 targets demonstrated that treatment with VP79s resulted in a rapid time-dependent decrease in expression of MCL-1. VP79s was shown to overcome adhesion mediated drug resistance in MM cells in a co-culture model system with bone marrow stromal cells which induces MM cell resistance to treatment with the proteasome inhibitor bortezomib. Combining VP79s with bortezomib synergistically enhanced apoptosis in MM cells compared with single agent treatment. VP79s showed selective cytotoxicity in patient derived MM cells compared to normal donor lymphocytes and reduced the viability of MM patient samples in a dose-responsive manner suggesting its potential as an anti-MM therapeutic. In conclusion, the novel agent VP79s inhibits the JAK/STAT3 signalling pathway resulting in rapid downregulation of MCL-1 expression and inducing potent anti-MM activity. This mechanism may suggest a novel strategy for targeting MCL-1, an emerging target in MM. Disclosures No relevant conflicts of interest to declare.

Dihydroartemisinin Modulates Apoptosis and Autophagy in Multiple Myeloma through the P38/MAPK and Wnt/β-Catenin Signaling Pathways.

Dihydroartemisinin (DHA), an active metabolite and derivative of artemisinin, is the most effective antimalarial drug and has strong antitumor activity in various tumor types. It has recently been reported that DHA can induce autophagy and has significant effects on multiple myeloma (MM), but the mechanisms and the relationship between the autophagy and apoptosis induced by DHA remain to be elucidated. Herein, we demonstrated that DHA significantly induces cell death in a dose- and time-dependent manner via the extrinsic and intrinsic apoptosis pathways. Moreover, DHA-induced autophagy, which plays a prodeath role in MM, can regulate canonical apoptosis and vice versa. Furthermore, the P38/MAPK signaling pathway is responsible for decreased autophagy and increased apoptosis. DHA induces autophagy and apoptosis also through the inhibition of the Wnt/β-catenin signaling pathway. In addition, DHA shows a strong effect in a xenograft mouse model. Collectively, these findings reveal that DHA, as an artemisinin-based drug, could be an effective and safe therapeutic agent for MM.

Abstract LB-227: Preclinical development and characterization of STI-6129, an anti-CD38 antibody-drug conjugate, as a new therapeutic agent for multiple myeloma

Abstract CD38 is a validated target for the treatment of CD38-overexpressing hematologic malignancies such as multiple myeloma (MM). Daratumumab is the first anti-CD38 mAb drug approved by the FDA for use as single agent and in combination with standard therapies for MM. However, resistance to Daratumumab in both primary and refractory MM patients has been reported. Here we report the preclinical development of STI-6129 (also CD38-077), a CD38-targeting antibody-drug conjugate (ADC), as a new therapeutic agent for MM. STI-6129 consists of a fully human anti-CD38 antibody, STI-5171, identified from the Sorrento G-MAB® antibody library, conjugated to the microtubule inhibitor duostatin-5.2 (Duo-5.2) via a non-polyethylene glycol linker using our site-specific conjugation proprietary C-LOCK technology. STI-5171 binds specifically to CD38-positive but not CD38-negative tumor cell lines with a KD ~ 1.72E-8 M. STI-6129 is internalized into CD38-positive cells at a rate comparable to that of the unconjugated antibody STI-5171. In cytotoxicity studies, STI-6129 exhibited CD38-dependent cytotoxic activity against a panel of CD38-expressing tumor cell lines with the range of EC50 from 5-100 µg/mL. Importantly, STI-6129 does not display cytotoxic activity (EC50 > 150 μg/mL) against normal human PBMCs after 120 hr exposure. Mechanistic evaluation of STI-5171 compared to Daratumumab revealed that this antibody does not induce homotypic aggregation of tumor cells, a cell adhesion response that has been reported to be linked to drug resistance and increased metastatic potential. Further, the anti-tumor activity of STI-6129 showed broad, potent, and CD38-dependent in vivo efficacy in multiple xenograft animal models. Pharmacokinetic evaluation of STI-6129 in Daudi-Fluc tumor-bearing mice revealed that the ADC is stable with half-life (T1/2) of 7-11 days, comparable to that of the unconjugated antibody. The serum concentration of STI-6129 remained above the therapeutically effective level up to 1 week in mice after a single injection at 10 mg/kg. In cynomolgus monkey, the PK profiles of STI-6129 and STI-5171 were nearly identical, further confirming the stability of the ADC in monkey blood circulation.In summary, STI-6129 exhibits potent in vitro and in vivo anti-tumor activities in multiple CD38-positive hematological models. These results warrant further development of STI-6129, potentially as a better or alternative agent for treatment of multiple myeloma. Citation Format: Lingna Li, Andrew Hau, Wenyong Tong, Megan Lau, Tong Zhu, Katherine Fells, Angel Wei, Xiaoqing Li, Dylan Deng, Yingqing Sun, Ernest Kovacs, Alisher Khasanov, Zheng Yan, Panyun Zhu, Heyue Zhou, Henry Ji, Hui Li, Hong Zhang. Preclinical development and characterization of STI-6129, an anti-CD38 antibody-drug conjugate, as a new therapeutic agent for multiple myeloma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-227.

The impact of first-line therapy with novel agents in multiple myeloma patients age 80 and above: A systematic review.

e20532 Background: Novel therapeutic agents in multiple myeloma (MM) have demonstrated significant improvements in treatment outcomes. However, data remains scarce in newly diagnosed transplant-ineligible patients aged 80 and above as they are less represented in clinical trials. Optimal treatment of this population also proves challenging due to treatment-related adverse events. Methods: MEDLINE and EMBASE search concluded March 4, 2019. We included studies that evaluated first-line treatment of age ≥80 transplant-ineligible MM patients with novel agents. The primary outcomes assessed were OS and PFS. A qualitative analysis was undertaken due to the small number of included articles. Results: Of 1683 articles assessed for eligibility, 134 articles proceeded to full-text review. 6 articles with a total of 819 patients age ≥ 80 (range 80-96) were included for analysis (5 retrospective analyses and 1 phase II, non-randomized trial). Median OS were significantly shorter in age ≥80 in comparison to younger groups (reported median OS ranged from 19.5-31.9mo for age ≥80, 46-54.8mo for age 66-79, and 81-83.8mo or not reached for age ≤65). Shorter survival was associated with poorer performance status, advanced ISS stage, higher Charlson Comorbidity Index, anemia and elevated serum LDH. In one study, attaining a very good partial response or better (≥VGPR) was associated with improved median OS (30.4mo vs 18.8mo, p = 0.001). There was no difference between age groups for OS if ≥ VGPR was attained (53.4mo in age ≥80, vs not reached in age 66-79 or age ≤65; p = 0.184). In 1 of 3 studies that reported median PFS, a significant difference in one study was noted by age [age ≥80 = 19.1mo, age 66-79 = 26.3mo (p = 0.033), ≤65 = 54.3mo (p = 0.0009)]. Early mortality (at 2 or 6 months; in 3 studies) was significantly greater than in patients age < 80 and was primarily due to infection or renal failure, and more often in the frail. One study noted that despite reduced OS, the relative survival rate was higher in patients aged ≥85 at 2 years than in younger age groups. Conclusions: Our review excluded most RCTs as subgroup analyses of patients aged ≥80 were not available. Regardless, included articles are representative of the real-world experience. This systematic review suggests that while MM patients aged ≥80 experience shorter OS and PFS, treatment with a novel agent may offer comparable survival outcomes to younger groups in those able to attain ≥VGPR. Relative survival in elderly patients also favours active treatment in this age group, while balancing the risks of early mortality.

Targeting of CD38 by the Tumor Suppressor miR-26a Serves as a Novel Potential Therapeutic Agent in Multiple Myeloma.

Multiple myeloma is an incurable refractory hematologic malignancy arising from plasma cells in the bone marrow. Here we investigated miR-26a function in multiple myeloma and tested single-wall carbon nanotube delivery of miR-26a in vitro and in vivo. miR-26a was downregulated in patients with multiple myeloma cells compared with plasma cells from healthy donors. miR-26a overexpression inhibited proliferation and migration and induced apoptosis in multiple myeloma cell lines. To identify the targets of miR-26a, RPMI8226-V-miR-26-GFP and RPMI8226-V-GFP cells were cultured using stable isotope labeling by amino acids in cell culture (SILAC) medium, followed by mass spectrometry analysis. In multiple myeloma cells overexpressing miR-26a, CD38 protein was downregulated and subsequently confirmed to be a direct target of miR-26a. Depletion of CD38 in multiple myeloma cells duplicated the multiple myeloma inhibition observed with exogenous expression of miR-26a, whereas restoration of CD38 overcame the inhibition of miR-26a in multiple myeloma cells. In a human multiple myeloma xenograft mouse model, overexpression of miR-26a inhibited CD38 expression, provoked cell apoptosis, and inhibited cell proliferation. Daratumumab is the first CD38 antibody drug for monotherapy and combination therapy for patients with multiple myeloma, but eventually resistance develops. In multiple myeloma cells, CD38 remained at low level during daratumumab treatment, but a high-quality response is sustained. In daratumumab-resistant multiple myeloma cells, CD38 expression was completely restored but failed to correlate with daratumumab-induced cell death. Therefore, a therapeutic strategy to confer selection pressure to maintain low CD38 expression in multiple myeloma cells may have clinical benefit. SIGNIFICANCE: These results highlight the tumor suppressor function of miR-26a via its targeting of CD38 and suggest the therapeutic potential of miR-26a in patients with multiple myeloma.

Promoter hypermethylation influences the suppressive role of long non-coding RNA MEG3 in the development of multiple myeloma.

Methylation is a fundamental regulator of gene transcription. Long non-coding RNA maternally expressed 3 (MEG3) inhibits cell proliferation in various types of cancer. However, the molecular mechanisms of MEG3 methylation in the regulation of multiple myeloma (MM) are unknown. In the present study, MEG3 upregulation was negatively associated with the International Staging System (ISS) status of the bone marrow samples of 39 patients with MM. MEG3 overexpression in an MM cell line resulted in elevated p53 expression. Furthermore, the results of methylation-specific PCR revealed that the abnormal methylation status of the MEG3 promoter region was present in eight of the 39 bone marrow samples collected. Treatment of the MM cell line with the DNA methylation inhibitor 5-Aza-2'-deoxycytidine (5-Aza-CdR) resulted in tumor cell proliferation inhibition, apoptosis induction and G0/G1 cell cycle arrest. Furthermore, 5-Aza-CdR decreased aberrant hypermethylation of the MEG3 promoter and increased the expression of MEG3. However, 5-Aza-CdR exerted no effect on p53 expression. To the best of our knowledge, the present study is the first to report that the demethylation reagent 5-Aza-CdR may serve as a therapeutic agent in MM by upregulating MEG3 expression. However, the mechanism of action was independent of p53 expression.

Autologous Stem-Cell Transplantation for Multiple Myeloma in the Era of Novel Therapies.

Despite the evolution of the therapeutic arsenal for the treatment of multiple myeloma (MM) over the past decade, autologous stem-cell transplantation (ASCT) remains an integral part of the treatment of patients with both newly diagnosed and relapsed MM. The advent of novel therapies, such as immunomodulatory agents, proteasome inhibitors, and monoclonal antibodies, has led to unprecedented levels of deep hematologic responses. Nonetheless, studies show that ASCT has an additive effect leading to additional deepening of responses. As the therapeutic agents for MM continue to evolve, the timing, duration, and sequence of their use in combination with ASCT will be crucial to understand to obtain the deepest response and survival benefit for patients with MM. This review aims to discuss the role of ASCT for the management of MM, with a particular focus on the role of ASCT in the context of novel therapies and minimal residual disease.

The Covalent CDK7 Inhibitor THZ1 Potently Induces Apoptosis in Multiple Myeloma Cells In Vitro and In Vivo.

The goal of this study was to characterize the activity of the covalent CDK7 inhibitor THZ1 in multiple myeloma models. Multiple myeloma lines were exposed to varying THZ1 concentrations alone or with carfilzomib or ABT-199, after which apoptosis was monitored by flow cytometry, protein expression by Western blot analysis, mRNA by RT-PCR. Analogous studies were performed in cells ectopically expressing c-MYC, MCL-1, or BCL-XL, or CRISPER-Cas CDK7 sgRNA knockout. Primary multiple myeloma cells were exposed to THZ1 ± carfilzomib or ABT-199. In vivo effects of THZ1 were examined in a systemic U266 xenograft model. THZ1 markedly diminished multiple myeloma cell proliferation and survival despite bortezomib or stromal cell resistance in association with G2-M arrest, inactivation of CTD RNA Pol II, dephosphorylation of CDKs 7 as well as 1, 2, and 9, and MCL-1, BCL-xL, and c-MYC mRNA or protein downregulation. Ectopic MCL-1, c-MYC, or BCL-XL expression significantly protected cells from THZ1 lethality. Both THZ1 and CRISPR-Cas CDK7 knockout sharply diminished multiple myeloma cell proliferation and significantly increased carfilzomib and ABT-199 lethality. Parallel effects and interactions were observed in primary CD138+ (N = 22) or primitive multiple myeloma cells (CD138-/CD19+/CD20+/CD27+; N = 16). THZ1 administration [10 mg/kg i.p. twice daily (BID), 5 days/week] significantly improved survival in a systemic multiple myeloma xenograft model with minimal toxicity and induced similar events observed in vitro, for example, MCL-1 and c-MYC downregulation. THZ1 potently reduces multiple myeloma cell proliferation through transcriptional downregulation of MCL-1, BCL-XL, and c-MYC in vitro and in vivo. It warrants further attention as a therapeutic agent in multiple myeloma.

Impact of chromosomal abnormalities on the efficacy of lenalidomide plus dexamethasone treatment in patients with relapsed/refractory multiple myeloma.

Lenalidomide is an effective therapeutic agent for multiple myeloma (MM). However, its efficacy in the context of chromosomal abnormalities (CA) is poorly understood. We retrospectively analyzed 83 patients with relapsed/refractory (RR) MM, who received lenalidomide plus low-dose dexamethasone (Ld), in the context of CA. The median age and number of prior therapies were 69 and 2, respectively. Three, 11, 45, and 19 patients achieved complete response, very good partial response, partial response, and stable disease, respectively. Median progression-free survival (PFS) and overall survival (OS) were 11.1 and 38.8 months, respectively. Seventy-two patients were evaluated for frequently observed translocations; median PFS was 24.4months in 20 patients with t(11;14), 13.0months in 16 patients with t(4;14), and 3.7months in seven patients with t(14;16). G-banded karyotype analysis detected 11 hypodiploid patients, who had shorter PFS and OS (2.5 and 6.2months, respectively) compared to others (13.0 and 43.7months, respectively). Hypodiploid patients showed poor clinical outcome, whereas patients with t(11;14) showed favorable outcome. In summary, the present study presents the clinical impact of chromosomal abnormalities on the outcome of Ld therapy, and contributes to understanding the appropriate choice of lenalidomide-based therapy to achieve effective treatment of RR MM.

Chidamide, a histone deacetylase inhibitor, induces growth arrest and apoptosis in multiple myeloma cells in a caspase‑dependent manner

Chidamide, a novel histone deacetylase (HDAC) inhibitor, induces antitumor effects in various types of cancer. The present study aimed to evaluate the cytotoxic effect of chidamide on multiple myeloma and the underlying mechanisms involved. Viability of multiple myeloma cells upon chidamide treatment was determined by the Cell Counting Kit-8 assay. Apoptosis induction and cell cycle alteration were detected by flow cytometry. Specific apoptosis-associated proteins and cell cycle proteins were evaluated by western blot analysis. Chidamide suppressed cell viability in a time- and dose-dependent manner. Chidamide treatment markedly suppressed the expression of type I HDACs and further induced the acetylation of histones H3 and H4. In addition, it promoted G0/G1 arrest by decreasing cyclin D1 and c-myc expression, and increasing phosphorylated-cellular tumor antigen p53 and cyclin-dependent kinase inhibitor 1 (p21) expression in a dose-dependent manner. Treatment with chidamide induced cell apoptosis by upregulating the apoptosis regulator Bax/B-cell lymphoma 2 ratio in a caspase-dependent manner. In addition, the combination of chidamide with bortezomib, a proteasome inhibitor widely used as a therapeutic agent for multiple myeloma, resulted in enhanced inhibition of cell viability. In conclusion, chidamide induces a marked antimyeloma effect by inducing G0/G1 arrest and apoptosis via a caspase-dependent pathway. The present study provides evidence for the clinical application of chidamide in multiple myeloma.

Immunogenic Cell Death and Immunotherapy of Multiple Myeloma.

Over the past decades, immunotherapy has demonstrated a prominent clinical efficacy in a wide variety of human tumors. For many years, apoptosis has been considered a non-immunogenic or tolerogenic process whereas necrosis or necroptosis has long been acknowledged to play a key role in inflammation and immune-related processes. However, the new concept of “immunogenic cell death” (ICD) has challenged this traditional view and has granted apoptosis with immunogenic abilities. This paradigm shift offers clear implications in designing novel anti-cancer therapeutic approaches. To date, several screening studies have been carried out to discover bona fide ICD inducers and reveal the inherent capacity of a wide variety of drugs to induce cell death-associated exposure of danger signals and to bring about in vivo anti-cancer immune responses. Recent shreds of evidence place ER stress at the core of all the scenarios where ICD occur. Furthermore, ER stress and the unfolded protein response (UPR) have emerged as important targets in different human cancers. Notably, in multiple myeloma (MM), a lethal plasma cell disorder, the elevated production of immunoglobulins leaves these cells heavily reliant on the survival arm of the UPR. For that reason, drugs that disrupt ER homeostasis and engage ER stress-associated cell death, such as proteasome inhibitors, which are currently used for the treatment of MM, as well as novel ER stressors are intended to be promising therapeutic agents in MM. This not only holds true for their capacity to induce cell death, but also to their potential ability to activate the immunogenic arm of the ER stress response, with the ensuing exposure of danger signals. We provide here an overview of the up-to-date knowledge regarding the cell death mechanisms involved in situations of ER stress with a special focus on the connections with the drug-induced ER stress pathways that evoke ICD. We will also discuss how this could assist in optimizing and developing better immunotherapeutic approaches, especially in MM treatment.