Ixazomib Research Articles

Proteasome inhibitors and risk of cardiovascular events in patients with multiple myeloma.

300 Background: Proteasome inhibitors (PI) represent a significant advancement in the treatment of multiple myeloma (MM). While recent studies have stressed the cardiovascular (CV) risk associated with carfilzomib (CARF) use, the risk with ixazomib (IXA) is underreported and no large comparative analysis is available. This study aims to compare CV and dose-limiting toxicities in MM patients treated with CARF and IXA. Methods: We conducted a retrospective cohort study analyzing TriNetX electronic medical records, including MM patients age 18 years and older who initiated CARF or IXA between January 1, 2016 to December 31, 2023. Patients with a prior history of heart failure (HF) or arrhythmias were excluded. We evaluated the incidence of new onset of HF and arrhythmia within three months of initiating PIs. Secondary outcomes included the incidence of diarrhea, nausea and vomiting during this period. Propensity score matching (PSM) was performed using 1:1 nearest neighbor matching to balance baseline characteristics. Matching covariates included patients’ demographics (age, sex, race/ethnicity), cardiovascular comorbidities and medications (cardiovascular and chemotherapy). Hazard ratios (HRs) for the outcomes were calculated using Cox proportional hazards models with a significance threshold of p<0.05. Results: We identified 950 and 2,872 patients in the IXA- and CARF-treated cohorts, respectively. After PSM, each cohort included 753 patients, with a mean age of 65 years, 52% male and 65% white. Matched populations had no significant differences with respect to matching criteria. The new onset of HF within three months was 2.8% in the IXA group and 5.4% in the CARF group (HR: 0.50, 95% CI: 0.30–0.85, p=0.009). The new onset of arrhythmias was also significantly lower in the IXA group (4.3%) compared to the CARF group (6.6%) (HR:0.63, 95% CI:0.40–0.98, p=0.04). There was no significant difference in the incidence of diarrhea (HR: 0.92, 95% CI: 0.68–1.26, p=0.61), while nausea/vomiting was significantly lower in the IXA group (HR:0.71, 95% CI:0.54–0.93, p=0.013). Conclusions: Our study indicates that ixazomib is associated with a significantly lower risk of cardiac side effects compared to carfilzomib in the treatment of MM, with similar gastrointestinal side effects. Enhanced cardiac monitoring may be necessary for patients on carfilzomib. Further research is needed to validate these cardiovascular risk differences.

Evaluation of the Effectiveness of Additional Risk Minimization Measures for Ixazomib Citrate for Relapsed/Refractory Multiple Myeloma in Japan: A Web-Based Survey Among Pharmacists.

Ixazomib citrate (IXA) in combination with lenalidomide and dexamethasone (IRD therapy) has been approved for the treatment of relapsed or refractory multiple myeloma. In Japan, as these three drugs have different dosing schedules, dosing instructions for patients have been prepared and distributed to patients via healthcare professionals to promote an understanding of the appropriate dosing regimen, as an additional risk minimization measure (aRMM). This survey aimed to investigate whether the aRMM material is being utilized for the adequate use of IXA. A web-based questionnaire survey was conducted among in-hospital pharmacists in Japan who instructed patients on IXA dosing for IRD therapy. The primary endpoint was the proportion of pharmacists who provided patients with the contents of the aRMM material (i.e., how to take IXA). The secondary endpoints were the proportion of pharmacists who had obtained the aRMM material and the proportion of pharmacists who understood the importance of explaining how to take IXA to patients. Of the 330 pharmacists who completed the questionnaire, 93.0% answered that they had explained how to take IXA to patients. Of those who answered that they had explained how to take IXA, 33.2% responded that they had experience in using the aRMM material. In addition, 37.6% of the pharmacists answered that they had obtained the aRMM material. Moreover, 95.8% stated that they knew how to take IXA, and 90.3, 9.1, 0.3, and 0.3% of pharmacists answered that the importance of explaining how to take IXA was "very important," "probably important," "less important" and "not important," respectively. How to take IXA was explained to patients by pharmacists and the aRMM material was utilized at the time of the explanation, indicating that the aRMM material contributes to the promotion of the appropriate use of IXA.

Abstract 4554: Novel combination therapy for treating proteasome inhibitor-resistant multiple myeloma

Abstract Multiple myeloma (MM) is an incurable plasma cell malignancy characterized by osteolytic bone disease and immunosuppression. Proteasome inhibitors (PIs) have remarkably improved the survival of MM patients, but dose-limiting toxicities and the development of drug resistance limit their long-term utility. Elevated TGF-β levels in MM patient sera correlate with drug resistance, disease progression, metastasis and poor prognosis. Therefore, we evaluated the anti-MM therapeutic potential of a TGF-β type I receptor kinase inhibitor, Vactosertib. In vitro treatment of Vactosertib synergistically inhibited the growth of bortezomib (BTZ)-resistant MM cells in combination with either BTZ or ixazomib (IXZ) by suppressing TGF-β activation of Smad2/3 and expression of PSMB5, which encodes the proteasome 5 catalytic subunit targeted by PIs. Oral administration of Vactosertib as a single agent decreased MM progression and mortality of the mice bearing BTZ-resistant MM. Vactosertib alone also attenuated PSMB5 expression and proteasome activity, reduced the expansion of CD11b+Gr-1+ myeloid derived suppressor cells (MDSCs) in bone marrow (BM) tumor microenvironment (TME), and diminished the population of Foxp3+ regulatory T cells (Treg) in the spleen. Combination therapy of Vactosertib plus PI (BTZ or IXZ) exhibited a synergistic anti-myeloma effect when compared to either Vactosertib or PI alone by greatly prolonged survival and significant a reduction in both MDSCs and Tregs. Furthermore, therapy of BCMA+ CAR T cells in combination with Vactosertib exhibited a synergistic anti-tumor effect, compared to either CAR T cells or Vactosertib. Taken together, our data provide the rationale for clinical evaluation of Vactosertib in MM and demonstrate proof-of-concept that combination of Vactosertib and either PI or cell therapy may overcome drug resistance and enhance durable patient responses. Citation Format: Byung-Gyu Kim, Sung Hee Choi, Huong Nguyen, Fu-Sen Liang, Seong-Jin Kim, John Letterio, Alex Huang. Novel combination therapy for treating proteasome inhibitor-resistant multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4554.

Combined green analytical principles and quality by design for ultraperformance liquid chromatography analytical method development, the characterization and in-silico toxicity prediction of Ixazomib degradation products using mass spectrometry

Ixazomib citrate (IC) is the first oral selective proteosome inhibitor for treating multiple myeloma. IC is prone to degradation due to its oxidative deboronation and the amide bond, affecting patient health, drug quality, and efficacy. The stability of IC is crucial during drug development as it guides the inherent stability of the molecule, its degradation pathways, packing materials, and formulation development. Following the International Conference on Harmonization (ICH) Q1A (R2) and Q1B, a stability study were performed for both solution and solid-state stress studies. Under oxidative and alkaline conditions, 3 degradation products (DPs) were identified, separated, and method-validated according to ICH Q2 (R1) guidelines. From the Design Expert statistical tool, the Central Composite Design was used to optimize the final analytical method conditions, where the p-values for the model are < 0.05%. Green analytical chemistry has significantly reduced the use of hazardous organic solvents without losing chromatographic performance. The green separation and quantification of DPs and IC on Ultra Performance Liquid Chromatography (UPLC) using an Inert-Sustain C8 (50×3.0) mm 2.0 µm column with gradient elution using 10 mM ammonium acetate buffer (pH 5.0) and ethanol at a flow rate of 0.5 mL/min and detection at 230 nm. The results of green assessment tools like GAPI, AGREE, and Analytical eco-scale found that the method is excellent for the greenness of utilizing ethanol as a solvent, shorter runtime, and lesser waste. The method was validated as per ICH Q2 guidelines, and the results found it is sensitive, precise, accurate, robust, and linear for its intended use. The method is suitable for quantifying IC and its DPs from 2.0 to 150 µg/mL with R2 values of 0.9996 with a detection limit of 1.0 µg/mL. The plausible degradation structures and pathways of DPs were outlined using tandem mass spectra employed on LC-QTOF-MS/MS in both ESI positive and negative modes. The mechanistic explanation for establishing DPs was explained in detail. The ADMET Predictor™ software predicted the physicochemical and ADMET properties. The toxicity profile reveals that DP2 and DP3 are teratogenic, while D1 and D3 show phospholipidosis.

The Relative Efficacy of Available Proteasome Inhibitors in Preventing Muscle Contractures Following Neonatal Brachial Plexus Injury.

Contractures following neonatal brachial plexus injury (NBPI) are associated with growth deficits in denervated muscles. This impairment is mediated by an increase in muscle protein degradation, as contractures can be prevented in an NBPI mouse model with bortezomib (BTZ), a proteasome inhibitor (PI). However, BTZ treatment causes substantial toxicity (0% to 80% mortality). The current study tested the hypothesis that newer-generation PIs can prevent contractures with less severe toxicity than BTZ. Unilateral brachial plexus injuries were surgically created in postnatal (5-day-old) mice. Following NBPI, mice were treated with either saline solution or various doses of 1 of 3 different PIs: ixazomib (IXZ), carfilzomib (CFZ), or marizomib (MRZ). Four weeks post-NBPI, mice were assessed for bilateral passive range of motion at the shoulder and elbow joints, with blinding to the treatment group, through an established digital photography technique to determine contracture severity. Drug toxicity was assessed with survival curves. All PIs prevented contractures at both the elbow and shoulder (p < 0.05 versus saline solution controls), with the exception of IXZ, which did not prevent shoulder contractures. However, their efficacies and toxicity profiles differed. At lower doses, CFZ was limited by toxicity (30% to 40% mortality), whereas MRZ was limited by efficacy. At higher doses, CFZ was limited by loss of efficacy, MRZ was limited by toxicity (50% to 60% mortality), and IXZ was limited by toxicity (80% to 100% mortality) and loss of efficacy. Comparisons of the data on these drugs as well as data on BTZ generated in prior studies revealed BTZ to be optimal for preventing contractures, although it, too, was limited by toxicity. All of the tested second-generation PIs were able to reduce NBPI-induced contractures, offering further proof of concept for a regulatory role of the proteasome in contracture formation. However, the narrow dose ranges of efficacy for all PIs highlight the necessity of precise proteasome regulation for preventing contractures. Finally, the substantial toxicity stemming from proteasome inhibition underscores the importance of identifying muscle-targeted strategies to suppress protein degradation and prevent contractures safely. Although PIs offer unique opportunities to establish critical mechanistic insights into contracture pathophysiology, their clinical use is contraindicated in patients with NPBI at this time.

A Phase II Multicenter Clinical Trial Assessing the Safety and Efficacy of Ixazomib, Pomalidomide and Dexamethasone Combination As Second or Third-Line Treatment for Triple-Class Exposed Patients with Relapsed and Refractory Multiple Myeloma (iPod-790 Trial)

Introduction: Despite significant improvement in the outcomes of early treatment lines in myeloma, most patients (Pts) invariably relapse. As triple and quadruple regimens are being introduced at the upfront setting, many Pts are either triple-class exposed or triple-class refractory (TCE/TCR) early in their disease course. Although novel immunotherapies are emerging with impressive efficacy among TCE/TCR myeloma Pts, their use is currently limited due to potential toxicities, costs and logistic constraints. We report the outcomes of the IPoD-790 clinical trial (NCT04790474), an all-oral regimen: ixazomib (IXA), pomalidomide (POM) and dexamethasone (DEX) (IPd) combination, in Pts with relapsed refractory multiple myeloma (RRMM) who progressed after bortezomib (BTZ), lenalidomide (LEN) and daratumumab (DARA) therapies. Methods: A phase 2, investigator initiated, open-label, single-arm, prospective, multicenter study evaluating the safety, tolerability and efficacy of IPd as a second or third-line combination treatment for TCE RRMM Pts. Pts receive IXA: 3 mg days (d) 1,4,8,11 of 21-d Cycles (Cy) 1-3; 4mg d 1,8,15 of 28-d Cy 4-24. POM 4mg: d 1-14 Cy 1-3; d 1-21 Cy 4-24. DEX 20mg: d 1,2,8,9,15,16 Cy 1-3; d 1,2,8,9,15,16,22,23 Cy 4-24. Treatment continues for 24 cycles, or until disease progression (PD) or unacceptable toxicity (the earliest of the three). After completion of 24 treatment cycles, Pts continue POM DEX as standard of care. The primary endpoint is progression free survival (PFS) according to IMWG criteria. Results: Fifty-five (out of the 60 Pts planned) were enrolled; we report data on 46 Pts who had their first dose between March 2021 and April 2023, further data will be presented at the meeting. The median age was 72 (range: 53-88); 18 (39%) were ≥75 years old; 59% were male, ISS was I/II/II for 48% / 25% and 28% respectively; 59% had high risk FISH cytogenetics (t(4:14), t(14:16), +1q21, del17p) with 14% double-hit. Nine percent had extramedullary disease at study enrollment. Exposure rates to BTZ, LEN and DARA were 100%, 98% and 96%, respectively. Forty-one percent had undergone autologous bone marrow transplantation. Refractoriness rates to BTZ, LEN and DARA were 57%, 91% and 65%, respectively. Thirty-seven percent were TCR. At data cutoff date of 15-Jun-2023, the median follow-up time was 10.4 [95% CI 7.6-13.2] months. Ninety-three percent of the Pts had at least one treatment emergent adverse event (TEAE) and 65% had a TEAE grade 3 or 4. Common (≥ 10%) TEAEs include neutropenia 35% (28% Gr 3 or 4), pneumonia 24% (17% Gr 3 or 4), thrombocytopenia 22% (15% Gr 3 or 4), back pain 22% (2% Gr 3 or 4), asthenia 20% (0% Gr 3 or 4), diarrhea 20% (0% Gr 3 or 4), peripheral edema 20% (2% Gr 3 or 4), COVID19 infection 15% (2% Gr 3 or 4 ), anemia 13% (2% Gr 3 or 4), acute kidney injury (AKI) 13% (7% Gr 3 or 4), rash 13% (0% Gr 3 or 4). At data cut-off date, 31 Pts (67%) discontinued the study treatment; 20 (43%) due to PD, 7 (15%) due to adverse events (including 3 patients with pneumonia, and 1 patient each with COVID19 infection, campylobacter gastroenteritis, upper gastrointestinal bleeding and AKI) and 4 (9%) died (2 cases of pneumonia, 1 COVID 19 infection and 1 cerebro-vascular accident). Overall response rate was 59% (27/46); 8 Pts (17%) achieved complete or very good partial response (CR/VGPR), 19 Pts (41%) achieved partial response (PR) and 12 Pts (30%) had stable disease (SD). The median PFS was 6.6 [95% CI 2.9 - 10.3] months (Figure 1a). Median duration of response (DOR) was 10.8 months. Median OS was not reached; 1-year overall survival was 81.6±6.7% (Figure 1a). One-year OS was significantly better for responders (89.3±7.3%) than non-responders (72.2±10.7%), p=0.015 ( figure 1b). Conclusions: IPd combination with a twice-weekly ixazomib induction provided an all-oral safe and efficacious therapy in triple-exposed RRMM Pts, most of whom were refractory to both DARA and LEN. Response rates and PFS are encouraging, compared to parenteral PI and IMiD combination regimens in TCE/TCR MM, with a favorable safety profile and convenience, especially among an elderly and frail population with relapsed myeloma.

Medical Writing Bias in Myeloma Clinical Research: A Comprehensive Analysis

Background Previous studies investigating associations between pharmaceutical funding and clinical trial results have found ties between pharmaceutical sponsorship and results favoring the sponsor's interests. There are no studies examining potential sponsorship bias within the field of multiple myeloma (MM). Addressing sponsorship bias is essential to ensure reliability, validity, and ethical conduct of clinical research in the field of MM. This study analyzes potential sponsorship bias in MM specifically regarding use of medical writers that are employees of or directly funded by pharmaceutical companies among published clinical research studies of drugs approved to treat MM from January 2000 - March 2023. Methods Clinical study papers from PubMed between January 2000 and March 2023 were analyzed if at least 1 of the 10 following drugs were evaluated: bortezomib (BORT), carfilzomib (CARF), daratumumab (DARA, elotuzumab (ELO), isatuximab (ISA), ixazomib (IXA), lenalidomide (LEN), panobinostat (PAN), pomalidomide (POM), and selinexor (SELI), and the manufacturer of the drug(s) sponsored the study (N=1466). Papers were considered to contain potential medical writing bias if the paper was written by employees of the manufacturer of the drug(s) or medical writers directly funded by the manufacturer. Papers were analyzed by year, drug, and journal in which it was published. Results From 2000 - March 2006, no potential writing bias occurred. In 2007, it first became apparent when 4% (2/53) of papers showed bias which has increased as follows: 2008 - 2012 [14% (41/300)], 2013 - 2017 [25% (100/405)], 2018-2022 [33% (171/521)], and increased to 44% (12/27) in 2023. We also analyzed writing bias according to the specific drugs from January 2000 - March 2023 with the following rates of potential bias: ISA 93% (26/28), IXA 77% (36/47), DARA 76% (63/83), ELO 71% (17/24), SELI 62% (8/13), POM 55% (27/49), PAN 50% (9/18), BORT 47% (47/100), LEN 46% (75/163) and CARF 32% (15/47). Potential writing bias was also determined according to the specific medical journal in which the paper was published from 2000 - March 2023. Blood and British Journal of Haematology have the highest number of potentially biased manuscripts at 42 and 30, respectively, representing 25% (42/142) and 21% (30/143) of the papers published, respectively. New England Journal of Medicine and Lancet have high percentages of potential writing bias at 33% (9/27) and 46% (6/13), respectively. Many journals have 100% (n=6) but these sources only had 1 paper meeting the study criteria. Conclusion Since 2000, we have observed an alarming increase in the rate of clinical research papers evaluating drugs approved to treat MM which have been written by pharmaceutical company employees or medical writers directly funded by them. Notably, nearly half (44%) of papers published this year showed potential writing bias. Rates varied greatly between different drugs with ISA, IXA and DARA showing the highest rates of writing bias whereas BORT, LEN and CARF showed the lowest rates. Specific journals including Blood and British Journal of Haematology both show high numbers of papers with potential writing bias; and, furthermore, a high percentage of papers published in high impact journals such as the New England Journal of Medicine and Lancet show this type of potential bias. This practice of allowing medical writing to be carried out by those with direct ties to the pharmaceutical company is likely to result in the publication of papers with results and conclusions regarding the efficacy and safety of drugs that are biased which compromises their scientific integrity and objectivity.

CNOT4 Knockout Induces Proteasome Inhibitor Resistance in Multiple Myeloma Cells

Background: The outcomes of multiple myeloma (MM) patients have been significantly improved with novel therapies including proteasome inhibitors (PI). However, many patients develop PI resistance and becoming refractory to PI. Although several studies have identified the mechanisms of PI resistance, such as mutation to the proteasome β5 subunit, ER stress suppression, autophagy activation, and activation of efflux drug pumps, it remains unclear yet. To investigate new genes that may contribute to PI resistance, we performed a genome-wide CRISPR dropout screening in an MM cell line. Materials and Methods: To identify the genes responsible for PI resistance, we used a CRISPR library (Kosuke Yusa, V3) targeting 18,740 human genes. The knockout cells, in which an CRISPR library lentivirus was introduced into a Cas9-expressing AMO1 MM cell line, were treated with ixazomib (IXA), carfilzomib (CFZ), and DMSO for two weeks. Next, we used next generation sequencing (NGS) to count sgRNA copy numbers of the pre-drug control group and the drug-treated group. NGS analysis of the treated cells showed that inactivated genes which induced higher levels of cell proliferation in the PI group than in the DMSO group were considered candidate genes for PI resistance. Results: We identified 35 genes for PI resistance including the genes encoding subunits of the proteasome 19S complex, consistent with previous reports that shows reducing 19S subunits protects MM cells from bortezomib. Among 35 candidate genes, we chose the top hit gene, CNOT4, to further investigate. CNOT4 is a component of CCR4-NOT complex which removes the mRNA poly(A) tail for degradation of mRNA. In addition, CNOT4 has E3 ubiquitin ligase activity and is reported to control the proteasome complex formation. To further validate the effect of PI resistance with inactivated CNOT4, we generated CNOT4 KO AMO1 cells and performed an MTS assay. We observed a decrease in PI sensitivity compared with AMO1 wildtype (WT) (IXA IC 50: 24.8 nM (KO) vs 13.0 nM (WT), CFZ IC 50: 7.45 nM (KO) vs 2.76 nM (WT)). To investigate the influence of CNOT4 on proteasome complex formation and its activity, we first measured the expression of ubiquitinated proteins by Western blotting. In CNOT4 KO AMO1 cells, the expression of ubiquitinated proteins is increased with or without PI treatment, suggesting that inactivated CNOT4 can suppress the function of degrade ubiquitinated proteins in proteasome 19S complex. To elucidate the mechanism underlying the resistance effect, we next checked the expression of ER stress marker proteins. In CNOT4 KO AMO1 cells, the expression of PERK and IRE1α proteins are decreased with PI treatment, suggesting that inactivated CNOT4 can suppress the ER stress levels in spite of the increases of ubiquitinated proteins. Conclusion: Our CRISPR screen revealed that CNOT4 inactivation induced PI resistance in human MM cells. CNOT4 inactivation suppresses the function of 19S proteasome, which is reported the influence of PI resistance, and downregulates the ER stress signal leading to avoid PI induced cell death. Our findings demonstrate that CNOT4 plays an important role in PI sensitivity.

Novel potential drugs for the treatment of primary open-angle glaucoma using protein-protein interaction network analysis.

Glaucoma is the second leading cause of irreversible blindness, and primary open-angle glaucoma (POAG) is the most common type. Due to inadequate diagnosis, treatment is often not administered until symptoms occur. Hence, approaches enabling earlier prediction or diagnosis of POAG are necessary. We aimed to identify novel drugs for glaucoma through bioinformatics and network analysis. Data from 36 samples, obtained from the trabecular meshwork of healthy individuals and patients with POAG, were acquired from a dataset. Next, differentially expressed genes (DEGs) were identified to construct a protein-protein interaction (PPI) network. In both stages, the genes were enriched by studying the critical biological processes and pathways related to POAG. Finally, a drug-gene network was constructed, and novel drugs for POAG treatment were proposed. Genes with p < 0.01 and |log fold change| > 0.3 (1,350 genes) were considered DEGs and utilized to construct a PPI network. Enrichment analysis yielded several key pathways that were upregulated or downregulated. For example, extracellular matrix organization, the immune system, neutrophil degranulation, and cytokine signaling were upregulated among immune pathways, while signal transduction, the immune system, extracellular matrix organization, and receptor tyrosine kinase signaling were downregulated. Finally, novel drugs including metformin hydrochloride, ixazomib citrate, and cisplatin warrant further analysis of their potential roles in POAG treatment. The candidate drugs identified in this computational analysis require in vitro and in vivo validation to confirm their effectiveness in POAG treatment. This may pave the way for understanding life-threatening disorders such as cancer.

Molecular Cardiotoxic Effects of Proteasome Inhibitors Carfilzomib and Ixazomib and Their Combination with Dexamethasone Involve Mitochondrial Dysregulation.

With the development and approval of new proteasome inhibitors, proteasome inhibition is increasingly recognized in cancer therapy. Besides successful anti-cancer effects in hematological cancers, side effects such as cardiotoxicity are limiting effective treatment. In this study, we used a cardiomyocyte model to investigate the molecular cardiotoxic mechanisms of carfilzomib (CFZ) and ixazomib (IXZ) alone or in combination with the immunomodulatory drug dexamethasone (DEX) which is frequently used in combination therapies in the clinic. According to our findings, CFZ showed a higher cytotoxic effect at lower concentrations than IXZ. DEX combination attenuated the cytotoxicity for both proteasome inhibitors. All drug treatments caused a marked increase in K48 ubiquitination. Both CFZ and IXZ caused an upregulation in cellular and endoplasmic reticulum stress protein (HSP90, HSP70, GRP94, and GRP78) levels and DEX combination attenuated the increased stress protein levels. Importantly, IXZ and IXZ-DEX treatments caused upregulation of mitochondria fission and fusion gene expression levels higher than caused by CFZ and CFZ-DEX combination. The IXZ-DEX combination reduced the levels of OXPHOS proteins (Complex II-V) more than the CFZ-DEX combination. Reduced mitochondrial membrane potential and ATP production were detected with all drug treatments in cardiomyocytes. Our findings suggest that the cardiotoxic effect of proteasome inhibitors may be due to their class effect and stress response and mitochondrial dysfunction may be involved in the cardiotoxicity process.

Design and discovery of novel dipeptide boronic acid ester proteasome inhibitors, an oral slowly-released prodrug for the treatment of multiple myeloma

Multiple myeloma (MM), the second most common hematological malignancy, is a disease characterized by a clonal expansion of malignant plasma cells that accumulate in the bone marrow. Ixazomib citrate was the first commercially available oral proteasome inhibitor for the treatment of MM. However, it immediately hydrolyzed into the active form on exposure to aqueous solution and so it was a pseudo prodrug. Herein, a series of dipeptide boronic acid esters as novel oral proteasome inhibitors were designed, synthesized and biologically investigated for the inhibition of the β5 subunit of 20S proteasome. Based on the enzymatic results, structure-activity relationships (SAR) were discussed in detail. Some potent compounds were further evaluated to inhibit the proliferation of MM cell line RPMI-8226. The results showed that some compounds were active against RPMI-8226 with IC50 values of less than 10 nM. The solution stability showed that ixazomib citrate was completely hydrolyzed to its active form ixazomib within 2 min in the simulated gastric juice. However, among the screened compounds, prodrug 18u was stable enough in simulated gastric juice and simulated intestinal juice, and its hydrolysis rate was 59.7% and 3.6% after 2 h, respectively. In addition, 18u exhibited good microsome stabilities and pharmacokinetic properties and displayed strong antiproliferative activity against the RPMI-8226 cell line (5.6 nM). Furthermore, compound 18u exhibited strong in vivo anticancer efficacy in human MM (RPMI-8226) xenograft mouse model.

The UHPLC-UV method applied for the forced degradation study of ixazomib and HRMS identification of its degradation products

Ixazomib is the only orally active proteasome inhibitor used in clinical practice as an anticancer drug. The novel, rapid UHPLC-UV assay for ixazomib was developed and applied to the forced degradation study followed by HRMS identification of the main degradation products. Oxidative deboronation and hydrolysis of the amid bond were found to be the principal degradation pathways. The chemical standards of the main degradation products were prepared. The method was validated for the simultaneous assay of ixazomib and its degradation products within the concentration ranges of 2.50–100.00 µg/mL (ixazomib); 0.75–60.00 μg/mL (Impurity A and B) and 1.25–60.00 μg/mL (Impurity C). The stability study revealed that ixazomib in solution is: 1) relatively stable in neutral and acidic environments, 2) its decomposition is accelerated at higher pH, 3) it is sensitive to the effects of oxidants and light, and 4) the degradation of ixazomib follows the first-order kinetics under neutral, acidic, alkaline, and UV stress. Contrary, the solid substance of ixazomib citrate was relatively resistant to heat (70 °C), heat/humidity (70 °C/75 % RH), and UV irradiation for 24 h. This study presents the first MS-compatible UHPLC method for the quantification of ixazomib and its degradation products. Furthermore, it provides data about the inherent stability and kinetics of degradation of ixazomib in a solution that may be useful in further investigation of this drug, or the development of novel proteasome inhibitors based on the ixazomib structure.

Effectiveness and Safety of Ixazomib in Combination with Lenalidomide and Dexamethasone in Relapsed or Refractory Multiple Myeloma in a Real-Life Population in France: The Remix Study

Background Ixazomib (IXA) is an oral proteasome inhibitor (PI) used in combination with lenalidomide and dexamethasone (IXA-Rd) for patients (pts) with relapsed and/or refractory multiple myeloma (RRMM). Efficacy and safety have been demonstrated in the phase 3 Tourmaline-MM1 clinical trial (1), which has recently reported the longest median overall survival (mOS) in phase III studies of Rd-based triplets (53.6 months, mo) (2). The REMIX study has been conducted since IXA became available in France in 2017. It is the largest cohort of RRMM pts receiving IXA-Rd combination in real life. The final analysis was performed with a median follow-up of 28.7 mo. Methods REMIX is a non-interventional, prospective study conducted in 59 sites (public and private) in pts with RRMM in France. To be eligible pts had to receive IXA-Rd in second line or later and IXA had to be initiated concomitantly to Rd (pts who started lenalidomide (lena) more than 6 weeks before IXA were excluded). After inclusion, pts were assessed every 3 mo during 24 mo and then every 6 mo as per standard practice. Analysis comprised OS, progression-free survival (PFS), overall response rate (ORR), very good partial response (VGPR) and tolerance. The analysis was conducted for the overall population and in subgroups of interest: age and lines of treatment (L2, L3 or L4+). Results A total of 376 eligible pts were included. Median age was 71 years (y) with 18.4% of patients aged ≥80y. At IXA-Rd initiation, 48.8% of pts were frail and 21.8% had renal clearance ≤50 ml/min. Comorbidities were reported in 62.8% of pts, including diabetes (8.8%), renal disease (8.8%) or solid tumour (6.4%). At inclusion, the cytogenetic risk was standard, high or unknown in 44.4%, 12% and 43.6% of pts, respectively. MM was diagnosed at a median of 4y before IXA-Rd initiation. 44.5% of pts had previous autologous stem cell transplantation (ASCT). IXA-Rd was initiated in L2, L3 or advanced lines (L4+) in 60.4%, 18.1% and 21.5% of pts, respectively. Regarding previous treatment received, 66.0% of pts had received IMID (including 39.2% lena and 11.7% pomalidomide), 93.1% had received PI (including 91.7% bortezomib and 7.5% carfilzomib) and 13.9% had received daratumumab. Most pts were previously exposed to lena in L3 (73.5% of L3, n=50/68, for a median duration of 16 mo) and L4+ (91.3% of L4+, n=73/81, for 17 mo) compared to L2 (10.6% of L2, n=24/227, for 18 mo). Out of all pts, 26, (7.9%) were considered lena-refractory during previous therapy. The median washout (WO) period between lena discontinuation and IXA-Rd start was 22.8 mo (SD: ±23.9). IXA was used for a median of 12.4 mo (13 cycles) at a 4-mg dose for 90.4% of pts. The median PFS (mPFS) was 19.1 mo (95% CI: 14.9-21.5) for the overall cohort, with a mPFS of 21.5 mo (95% CI: 19.2-24.8) for L2 (n=213), 21.9 mo (95% CI: 16.2-28.7) for L3 (n=65) and 5.8 mo (95% CI: 4.8-9.4) for L4+ (n=80). In the subgroups of pts aged <80y (n=293) and ≥80y (n=65), mPFS were 19.1 mo (95% CI: 15.9-21.9), and 17.4 mo (95% CI: 10.8-23.0), respectively. The mOS was not reached for the overall cohort; 36mo and 48mo OS rates were respectively 58.3% (95% CI: 52.6%-63.9%) and 52.4% (95% CI: 44.2%-60.5%). The 36mo OS rates were 63.4% (95% CI: 56.1-70.8%), 68.9% (95% CI: 57.1-80.7%) and 35.3% (95% CI: 23.9-46.7%) in L2, L3 and L4+ pts respectively. Among the 331 pts with available response according to investigators, the ORR was 73.1% (79.8% in L2, 70% in L3 and 54.4% in L4+ patients) and the VGPR rate was 45% (52.7% in L2, 41.7% in L3 and 25% in L4+ pts). IXA discontinuation was reported in 74.1% of pts (n=278). Discontinuation was related to AE in 21% of cases (n=79). Serious adverse events (SAE) were reported in 54.3% (n=204), including 57 (15.2%) pts with SAE considered related to IXA. Most frequent (>10%) AEs were diarrhoea (52%), thrombocytopenia (45.9%), asthenia (29.7%), neutropenia (23.6%) and anaemia (22.3%). Conclusion The REMIX study reported a mPFS in real-world conditions of 19.1 mo consistent with MM1 (20.6 mo), while half of patients were considered frail and 39.2% had previously received lenalidomide. The effectiveness in third line of treatment is similar to that in second line but was lower in L4+ as expected (5.7 mo). mOS is not reached at 48mo which aligns with MM1 final analysis. Reported AEs are consistent with the known safety profile of Ixazomib. Funding Takeda Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

A Phase II Multicenter Clinical Trial Assessing the Safety and Efficacy of Ixazomib Pomalidomide Dexamethasone Combination As Second or Third-Line Treatment for Patients with Triple Exposed Relapsed and Refractory Multiple Myeloma: Prespecified Interim Analysis (IPoD-790 trial)

Introduction: Despite significant improvement in the outcomes of early treatment lines in myeloma, most patients (Pts) invariably relapse. As triple and quadruple regimens are being introduced at the upfront setting, many Pts are either triple-exposed or triple-refractory early in their disease course. We report here the outcomes of a pre-specified interim analysis of the IPoD-790 clinical trial (NCT04790474), an all oral ixazomib (IXA) pomalidomide (POM) dexamethasone (DEX) (IPd) combination, in Pts with relapsed refractory multiple myeloma (RRMM) previously treated with bortezomib (BTZ) lenalidomide (LEN) and daratumumab (DARA). Methods: A phase 2, investigator initiated, open-label, single-arm, prospective, multicenter study evaluating the safety, tolerability and efficacy of IPd as a second or third-line combination treatment for Pts with RRMM who progressed after receiving BTZ, LEN and DARA during the first and second treatment lines. IXA is administered twice-weekly during the first 3 cycles. Pts receive IXA: 3 mg days (d) 1, 4, 8, 11 of 21-d Cycles (Cy) 1-3; 4mg d 1, 8, 15 of 28-d Cy 4-24. POM 4mg: d 1-14 Cy 1-3; d 1-21 Cy 4-24. DEX 20mg: d 1,2,8,9,15,16 Cy 1-3; d 1,2,8,9,15,16, 22,23 Cy 4-24. Treatment continues until disease progression (PD) or unacceptable toxicity. After completion of 24 treatment cycles, Pts continue POM DEX as standard of care. The primary endpoint is progression free survival (PFS) according to IMWG criteria. Results: Twenty-two Pts (out of the 60 Pts planned) enrolled between February 2021-May 2022. The median age was 71 (range: 53-88), median time from Myeloma diagnosis to study enrollment was 3.7 years; 58% had high risk FISH cytogenetics (t(4:14), +1q21, del17p); 10% had extramedullary disease at study enrollment; 32%, 9%, 73% and 86% of the Pts were refractory to BTZ, cyclophosphamide, LEN and DARA, respectively. Forty-five percent had previously undergone an auto-transplant. At the interim analysis cutoff date of 28-Jun-2022, after a median follow-up of 5.8 months (mo) (95% CI 4.5-7.1), 13 Pts discontinued the study treatment due to disease progression (PD) (n=9, 41%), death (n=2, 9%, 1 each: COVID-19 and cerebrovascular accident) and withdrawal of consent (n=2, 9%). Eighty-six percent of the Pts had at least one treatment emergent adverse event (TEAE) and 59% had a TEAE grade ≥3. TEAE that occurred in ≥10% include neutropenia 27% (23% ≥Gr 3), thrombocytopenia 27% (14% ≥Gr 3), rash 23%, diarrhea 14%, dyspnea 14%, fatigue 14%, COVID-19 14% and pneumonia 14% (14% ≥Gr 3). No Pts discontinued therapy due to an AE. Overall response rate was 53% (10/19 of evaluable Pts); 2 (10%) complete or very good partial response (CR/VGPR); 8 (42%) partial response (PR); 6 (32%) stable disease; 3 (16%) PD. Median time to response was 0.7 (range: 0.4-6) mo. The median PFS and overall survival (OS) were 6.9 [95% CI 2.0-12.0] and not-reached (NR), respectively [Figure 1A]. Median PFS was 10.4 vs 2.2 mo among Pts who achieved at least a PR vs non-responsive Pts, respectively (p=0.005). [Figure 1B]. Conclusions: IPd combination with twice-weekly ixazomib provided an all-oral safe and efficacious therapy in triple-exposed RRMM Pts, most of whom were refractory to both DARA and LEN. Study enrollment is ongoing. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

PEG@ Carbon Nanotubes Composite as an Effective Nanocarrier of Ixazomib for Myeloma Cancer Therapy

In this work, the preparation of a PEG@ multi-walled carbon nanotubes (MWCNTs) composite has shown a great potential effect in tumor therapy using graphite powder at room temperature. PEGylated MWCNTs were created and used as a carrier for targeting the antineoplastic drug Ixazomib to myeloma cancer cells (abnormal plasma cells). Ixazomib (MLN2238) was covalently encapsulated into functionalized carbon nanotubes modified with polyethylene glycol (PEG 600) to obtain MWCNTs-PEG-MLN2238. The Ixazomib@ MWCNTs-PEG composite shows promising results as an effective nanocarrier and using a small amount of MWCNTs-PEG-Ixazomib that has a low toxicity compared with that of Ixazomib alone. A multifunctional MWCNTs-PEG-Ixazomib composite is used to test biological effects on multiple myeloma cell lines RPMI 8226 using the MTT assay to enhance treatment efficiency. The cytotoxicity of free Ixazomib citrate (69% cell viability of RPMI8226 cells) was higher than that of MWCNTs-PEG-Ixazomib (91% cell viability) at the same maximum concentration of Ixazomib citrate (50 µg/ml). In this work, we performed a study of preparation of MWCNTs with an acceptable Ixazomib loading efficiency and determination of the drug systemic toxicity for the first time. In this study, the preparation of MWCNTs with acceptable Ixazomib loading efficiency and determination of the drug systemic toxicity was performed for the first time. The MTT assay results show decreasing the toxicity of Ixazomib after loading with the MWCNTs-PEG composite. The MWCNTs-PEG @ Ixazomib show promising results as an effective carrier of Ixazomib and lead to a decrease in the cost of using Ixazomib.Graphical

Bortezomib Eliminates Persistent Chlamydia trachomatis Infection through Rapid and Specific Host Cell Apoptosis.

Chlamydia trachomatis, a parasitic intracellular bacterium, is a major human pathogen that causes millions of trachoma, sexually transmitted infections, and pneumonia cases worldwide. Previously, peptidomimetic inhibitors consisting of a hydrophobic dipeptide derivative exhibited significant inhibitory effects against chlamydial growth. Based on this finding, this study showed that both bortezomib (BTZ) and ixazomib (IXA), anticancer drugs characterized by proteasome inhibitors, have intensive inhibitory activity against Chlamydia. Both BTZ and IXA consisted of hydrophobic dipeptide derivatives and strongly restricted the growth of Chlamydia (BTZ, IC50 = 24 nM). In contrast, no growth inhibitory effect was observed for other nonintracellular parasitic bacteria, such as Escherichia coli. BTZ and IXA appeared to inhibit chlamydial growth bacteriostatically via electron microscopy. Surprisingly, Chlamydia-infected cells that induced a persistent infection state were selectively eliminated by BTZ treatment, whereas uninfected cells survived. These results strongly suggested the potential of boron compounds based on hydrophobic dipeptides for treating chlamydial infections, including persistent infections, which may be useful for future therapeutic use in chlamydial infectious diseases.

High-Throughput Screening of FDA-Approved Drug Library Reveals Ixazomib Is a Broad-Spectrum Antiviral Agent against Arboviruses.

The emergence of significant arboviruses and their spillover transmission to humans represent a major threat to global public health. No approved drugs are available for the treatment of significant arboviruses in circulation today. The repurposing of clinically approved drugs is one of the most rapid and promising strategies in the identification of effective treatments for diseases caused by arboviruses. Here, we screened small-molecule compounds with anti-tick-borne encephalitis virus, West Nile virus, yellow fever virus and chikungunya virus activity from 2580 FDA-approved drugs. In total, 60 compounds showed antiviral efficacy against all four of the arboviruses in Huh7 cells. Among these compounds, ixazomib and ixazomib citrate (inhibitors of 20S proteasome β5) exerted antiviral effects at a low-micromolar concentration. The time-of-drug-addition assay suggested that ixazomib and ixazomib citrate disturbed multiple processes in viruses’ life cycles. Furthermore, ixazomib and ixazomib citrate potently inhibited chikungunya virus replication and relieved virus-induced footpad swelling in a mouse model. These results offer critical information which supports the role of ixazomib as a broad-spectrum agent against arboviruses.

P925: IMPACT OF PRIOR TREATMENT EXPOSURE ON THE EFFECTIVENESS OF IXAZOMIB-LENALIDOMIDE-DEXAMETHASONE IN RELAPSED/REFRACTORY MULTIPLE MYELOMA PATIENTS TREATED IN ROUTINE CLINICAL PRACTICE (THE INSURE STUDY)

Background: Results from INSURE, a pooled, global analysis of 3 observational studies, show that the effectiveness of ixazomib-lenalidomide-dexamethasone (IRd) used to treat relapsed/refractory multiple myeloma (RRMM) in routine clinical practice is comparable to its efficacy seen in the TOURMALINE-MM1 trial (median progression-free survival [PFS], 19.9 vs 20.6 months [mos]), with no new safety concerns (Leleu ASH 2021 #2701). Data on effectiveness outcomes following retreatment with agents used in earlier lines of therapy (LoTs) are limited, but may be of particular value for MM pts previously treated with lenalidomide (LEN) or proteosome inhibitors (PIs). Aims: To characterize the impact of prior exposure & refractoriness to LEN or PIs on the effectiveness & safety of IRd in RRMM. Methods: INSURE is a pooled analysis of data from 3 studies: INSIGHT MM, UVEA-IXA, & REMIX. INSIGHT MM is a prospective, global study of 4307 MM patients (pts) from 15 countries. UVEA-IXA is a multicenter, longitudinal, retrospective cohort study of 309 RRMM pts receiving ixazomib (IXA)-based therapy via an early-access program in Europe. REMIX is a retrospective/prospective study of 198 RRMM pts treated with IRd via a compassionate-use program in France. INSURE included adult RRMM pts who had received IRd in ≥2nd LoT. Primary outcomes were PFS & time-to-next therapy (TTNT). Secondary outcomes included: duration of treatment (DOT), overall survival (OS), overall response rate (ORR), & safety (discontinuations due to adverse events [AEs] were reported separately for each study). In this prespecified analysis pts were grouped by prior LEN or PI exposure (naïve, exposed, or refractory). Results: 562 pts were included: 391/100/71 were LEN-naïve/exposed/refractory & 37/408/117 were PI-naïve/exposed/refractory. In LEN-naïve/exposed/refractory pts, median age was 69/68/68 years (yrs; 24/14/18% >75 yrs) & 18/13/22% had an Eastern Cooperative Oncology Group performance status (ECOG PS) ≥2 (missing pts excluded from %); pts had received a median of 1/2/3 LoT(s) prior to IRd. In PI-naïve/exposed/refractory pts, median age was 71/68/69 yrs (38/22/15% >75 yrs) & 6/16/27% had an ECOG PS ≥2 (missing pts excluded from %); pts in all 3 subgroups had received a median of 2 LoTs prior to IRd. The Table shows effectiveness outcomes. Median DOT was 15.3/15.6/4.7 mos & median PFS was 21.6/25.8/5.8 mos in LEN-naïve/exposed/refractory pts. Median DOT & PFS in PI-naïve/exposed/refractory pts were 20.4/15.2/7.6 mos & not reached/19.7/12.9 mos, respectively. OS data were immature. The proportions of LEN-naïve/exposed/refractory pts in INSIGHT (n=114/39/28) & UVEA-IXA (n=161/15/19) who discontinued a study drug due to AEs were: IXA, 32/28/25% & 19/7/11%; LEN, 22/28/18% & 16/7/11%; dexamethasone (DEX), 18/21/14% & 11/0/11%, respectively. The proportions of PI-naïve/exposed/refractory pts in INSIGHT (n=9/130/42) & UVEA-IXA (n=18/125/52) who discontinued a study drug due to AEs were: IXA, 44/28/31% & 22/17/15%; LEN, 33/22/21% & 17/16/12%; DEX, 33/18/17% & 17/10/8%, respectively. Data for discontinuations due to AEs were not available for REMIX. Additional safety data will be presented. Image:Summary/Conclusion: IRd appeared to be effective in RRMM pts in routine clinical practice regardless of prior LEN or PI exposure, with better outcomes seen in LEN- &/or PI-non-refractory vs -refractory pts. PFS outcomes in the naïve/exposed populations are comparable to those reported in TOURMALINE-MM1. Pts with prior LEN or PI exposure can achieve clinical benefit when retreated suggesting that prior exposure should not preclude use of these agents in later LoTs.

Discovery of Inhibitors for Mycobacterium Tuberculosis Peptide Deformylase Based on Virtual Screening in Silico.

Tuberculosis has been the serious disease threatening human health and public safety due to the emergence of MDR and XDR-TB. Mycobacterium tuberculosis peptide deformylase (MtPDF) is a valuable target for antituberculotics. In order to discover new potential inhibitor candidates of MtPDF as leads for antituberculotics, Discovery Studio (DS) 2019 was used to perform molecular docking for virtual screening in silico with the bioactive compound library-I (L1700) against MtPDF. Six compounds with high docking scores and favourable ligand-protein interactions by LibDock and CDOCKER were selected for the evaluation of the inhibition potencies against MtPDF and Mycobacterium smegmatis. GST-6×His tagged MtPDF was recombinant expressed and purified firstly by Glutathione Sepharose 4B, and secondly by Ni Sepharose 6 FF after the cleavage of human rhinovirus 3C protease. These compounds showed IC50 values from 0.5 μmol/L to 112 μmol/L against MtPDF, among which CUDC-101 bearing hydroxamic acid exhibited IC50 of 0.5 μmol/L on MtPDF and MIC against Mycobacterium smegmatis of 32 μg/mL, and Ixazomib Citrate with IC50 of 63 μmol/L and MIC of 16 μg/mL. CUDC-101 and Ixazomib Citrate are promising as the potential leads for antituberculotics.

Abstract 1398: Impact of proteasome inhibitor specificity and efficacy on apoptosis induction by combination with ABT-199

Abstract Metastatic Soft-Tissue Sarcomas (STS) are a rare and highly heterogeneous group of mesenchymal malignancies that carry a poor prognosis. Therapy is hampered by a limited number of effective treatments, and the almost non-existing long-term survival rate illustrates the need of effective targeted treatment. As a potential approach, we investigated combination of the clinically approved BH3-mimetic drug ABT-199 with different proteasome inhibitors (PIs): Bortezomib, Carfilzomib and Ixazomib, each with proven efficacy, e.g., in multiple myeloma. ABT-199 selectively inhibits the anti-apoptotic protein Bcl-2 while Bortezomib (BOZ) and Ixazomib (IXZ) bind reversible to the β1 and β5 subunits of the 20S proteasome and Carfilzomib (CFZ) irreversibly blocks the subunits β2 and β5. We investigated whether the combination of ABT-199 with CFZ or IXZ shows synergistic activity as recently published for BOZ. SW982 sarcoma cells were cultured with PIs alone or in combination with ABT-199. Cell death was detected by flow cytometric analysis of mitochondrial membrane potential (TMRM) and exposure of phosphatidyl serine (Annexin V). To elucidate potential differences due to specificity of PIs, we analyzed expression of BCL-2 family proteins by Western Blot and performed analogue experiments in knock-out (BAXKO, BAKKO, BOKKO) cell lines. In combination, ABT-199&amp;BOZ or ABT-199&amp;CFZ showed comparable synergistic cell death induction in SW982 while ABT-199&amp;IXZ less efficiently induced cell death. Engineered SW982 knock-out cell lines suggests specific relevance of BOK in IXZ induced apoptosis, whereas all tested PIs crucially depend on BAX for apoptosis induction in combination with ABT-199. Also, as shown for ABT-199&amp;BOZ, both CFZ and IXZ, alone and in combination with ABT-199, efficiently induced expression of NOXA. Strikingly, and in line with augmented cell death induction, ABT-199&amp;CFZ resulted in highest expression of NOXA as compared to BOZ and IXZ. ABT-199&amp;PIs synergistically induce apoptotic cell death in SW982 and corresponding knock-out cell lines with CFZ showing exacerbated expression of NOXA. ABT-199&amp;CFZ also induced strongest stabilization of p53, a transcriptional key regulator of NOXA. We suggest that simultaneous inhibition of anti-apoptotic BCL-2 by ABT-199 and the enhanced expression of NOXA double-hit on the BCL-2 and the MCL-1 signaling axis force the cells over the threshold of apoptosis. Enhanced efficacy of CFZ is dually caused by reduced degradation of NOXA and enhanced stabilization of p53, which in turn transactivates expression of NOXA. In conclusion, PI specificity and efficacy modulate apoptosis induction by combination with ABT-199. Future efforts, e.g. knock-out of relevant BH3-only proteins, will elucidate the observed variable efficacy of these and other PIs for prospective translation in clinical applications. Citation Format: Sandra Weller, Benjamin Schaefer, Tobias Beigl, Kathrin Böpple, Walter E. Aulitzky, Hans-Georg Kopp, Frank Essmann. Impact of proteasome inhibitor specificity and efficacy on apoptosis induction by combination with ABT-199 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1398.