Bcl-xL Inhibitor Research Articles

Molecular Docking of Natural Alkaloids with Bcl-xL Protein in The Apoptosis Process

Background: The anti-apoptotic protein Bcl-xL is a viable target for cancer therapy due to its critical role in cancer formation and resistance to chemotherapy. Insights into Bcl-xL’s role have spurred the development of a new category of cancer drugs called Bcl-xL inhibitors, which mimic the BH3-only protein to cause apoptosis. It could be initiated using alkaloids, owing to their remarkable biological characteristics. Alkaloids, among the biggest obtainable from plants, possess a distinctive structure characterized by the presence of a nitrogen atom in various positions within the molecule. Objective: In the current study, the potential of various alkaloids as Bcl-xL inhibitors was investigated through a molecular docking study. Methods: AutoDock Vina software was used to perform docking simulations of the alkaloids. Results: Ten alkaloids/Bcl-xL protein complexes demonstrated strong binding affinities less than -8.0 kcal/mol-1. These complexes include phaenthine (26), 4,5-Dioxoaporphine (1), anonaine (2), atherospermidine (4), limacine (14), liriodenine (16), monomargine (18), ouregidione (24), oxostephanine (25), and taliscanine (29) as the ligand of Bcl-xL protein. Notably, the complexes of Bcl-xL/dicentrinone (10), ouregidione (24), stepharine (28), and taliscanine (29) displayed three to four hydrogen bonds along with hydrophobic contacts. Conclusion: These results suggest that certain alkaloids could act as potential Bcl-xL inhibitors, mimicking BH3-only proteins and thereby potentially triggering apoptosis during cancer treatment.

The dual BCL-2 and BCL-XL inhibitor AZD4320 acts on-target and synergizes with MCL-1 inhibition in B-cell precursor ALL

The dual BCL-2 and BCL-XL inhibitor AZD4320 acts on-target and synergizes with MCL-1 inhibition in B-cell precursor ALL

Novel hydrazide-hydrazone containing 1,2,4-triazole as potent inhibitors of antiapoptotic protein Bcl-xL: Synthesis, biological evaluation, and docking studies.

This study describes the synthesis and characterization of a series of novel hydrazide-hydrazone derivatives containing a 1,2,4-triazole ring. The compounds were characterized using various spectroscopic techniques, such as FT-IR, 1H-NMR, 13C-NMR, HRMS, and elemental analysis. The antiproliferative activity of the synthesized compounds was evaluated against a panel of human cancer cell lines (HCT-116, HepG-2, KLN205, LTPA, U138, and SW620) and healthy cell lines (HSkMC and iPSCs). Among the compounds tested, compounds 4, 5p, 5r, and 5s showed the highest effectiveness in inhibiting the growth of cancer cells with Bcl-xL inhibitory concentration (IC50) values. These compounds further demonstrated selective cytotoxicity against the Bcl-xL-dependent lymphoma cell line (DBs). Molecular docking studies were also performed to investigate the potential binding interactions of compounds 4, 5p, 5r, and 5s with the active site of Bcl-xL (PDB ID: 7LH7, 1.4 Å). Mechanistic studies revealed that compounds 4, 5r, and 5s induced apoptosis predominantly through the intrinsic mitochondrial pathway, while compound 5p exhibited a distinct cell cycle arrest profile, impacting both the S and G2/M phases. Western blot analysis suggested that these compounds may downregulate cyclin expression, thereby blocking its association with Bcl-xL. Overall, these results demonstrate the potential of these novel hydrazide-hydrazone derivatives as anticancer agents with activity comparable or superior to doxorubicin and 5-fluorouracil.

The Innate Immune System and TRAIL-BCL-XL Axis Mediate a Sex Bias in Lung Cancer and Confer a Therapeutic Vulnerability in Females.

There is a significant sex-bias in lung cancer with males showing increased mortality compared to females. A better mechanistic understanding of these differences could help identify therapeutic targets to personalize cancer therapies to each sex. After observing a clear sex-bias in humanized mice, with male patient-derived xenograft (PDX) lung tumors being more progressive and deadlier than female PDX lung tumors, we identified mouse tumor models of lung cancer with the same sex-bias. This sex-bias was not observed in models of breast, colon, melanoma, and renal cancers. In vivo, the sex-bias in growth and lethality required intact ovaries, functional innate natural killer (NK) cells and monocytes/macrophages, and the activating receptor NKG2D. Ex vivo cell culture models were sensitized to the anti-cancer effects of NKG2D-mediated NK cell and macrophage killing through the TRAIL-BCL-XL axis when cultured with serum from female mice with intact ovaries. In both flank and orthotopic models, the BCL-XL inhibitor navitoclax (ABT-263) improved tumor growth control in female mice and required NK cells, macrophages, and the TRAIL signaling pathway. This research suggests that navitoclax and TRAIL pathway agonists could be used as a personalized therapy to improve outcomes in women with lung cancer.

Contribution of A1 to macrophage survival in cooperation with MCL-1 and BCL-XL in a murine cell model of myeloid differentiation

Myeloid cells are the first line of defence against pathogens. Mitochondrial apoptosis signalling is a crucial regulator of myeloid cell lifespan and modulates the function of myeloid cells. The anti-apoptotic protein BCL-2-family protein BCL2A1/A1/BFL-1 is strongly upregulated in inflammation in macrophages. We analysed the contribution of A1 to apoptosis regulation in a conditional system of in vitro differentiation of murine macrophages from immortalised progenitors. We disabled the expression of A1 by targeting all murine A1 isoforms in the genome. Specific inhibitors were used to inactivate other anti-apoptotic proteins. Macrophage progenitor survival mainly depended on the anti-apoptotic proteins MCL-1, BCL-XL and A1 but not BCL-2. Deletion of A1 on its own had little effect on progenitor cell survival but was sensitised to cell death induction when BCL-XL or MCL-1 was neutralised. In progenitors, A1 was required for survival in the presence of the inflammatory stimulus LPS. Differentiated macrophages were resistant to inhibition of single anti-apoptotic proteins, but A1 was required to protect macrophages against inhibition of either BCL-XL or MCL-1; BCL-2 only had a minor role in these cells. Cell death by neutralisation of anti-apoptotic proteins completely depended on BAX with a small contribution of BAK only in progenitors in the presence of LPS. A1 and NOXA appeared to stabilise each other at the posttranscriptional level suggesting direct binding. Co-immunoprecipitation experiments showed the binding of A1 to NOXA and BIM. Interaction between A1 and Noxa may indirectly prevent neutralisation and destabilization of MCL-1. Our findings suggest a unique role for A1 as a modulator of survival in the macrophage lineage in concert with MCL-1 and BCL-XL, especially in a pro-inflammatory environment.

Abstract C032: De novo pyrimidine biosynthesis inhibition synergizes with BCL-XL targeting in pancreatic cancer

Abstract Oncogenic KRAS, the genetic driver of 90% of PDAC, induces a metabolic rewiring characterized, in part, by dependency on de novo pyrimidine biosynthesis. Dihydroorotate dehydrogenase (DHODH) is the enzymatic ‘chokepoint’ of the de novo pyrimidine biosynthesis pathway and an in vivo metabolic liability in pancreatic ductal adenocarcinoma (PDAC). Targeting enzymes in the de novo pyrimidine synthesis pathway such as dihydroorotate dehydrogenase (DHODH) with clinically available inhibitor brequinar (BQ) starved the tumor of nucleotide synthesis and restrained growth of PDAC cells in vitro. However, therapeutic resistance limited BQ long-term effects in PDAC xenografts, which suggests compensatory pathways and that combinatorial strategies are required for enhanced efficacy. Here, we integrated a mass spectrometry (MS)-based quantitative temporal proteomics workflow, LC/MS- based metabolomics and in vitro and in vivo drug-anchored CRISPR/Cas9 genetic screens to identify compensatory pathways to DHODH inhibition (DHODHi) and targets for combination strategies. We demonstrate that DHODHi alters the apoptotic regulatory proteome thereby enhancing sensitivity to inhibitors of the anti-apoptotic BCL2L1 (BCL-XL) protein. Combinatorial regimens with DHODH and BCL-XL inhibition synergistically induce apoptosis in PDAC cell lines and patient-derived PDAC organoids. In vivo DHODH inhibition with Brequinar and BCL-XL degradation with DT2216, a proteolysis targeting chimera (PROTAC), significantly inhibits the growth of PDAC tumors. Our data defines mechanisms of adaptation to DHODH inhibition and identifies a combination therapy strategy in PDAC. Citation Format: huan zhang, Qijia yu, Naiara Santana-Codina, Clara Poupault, Claudia Campos, Xingping Qin, Aparna Padhye, Nicole Sindoni, Miljan Kuljanin, Junning Wang, Matthew J. Dorman, Andrew J. Aguirre, Stephanie K. Dougan, Kristopher A. Sarosiek, Joseph D. Mancias. De novo pyrimidine biosynthesis inhibition synergizes with BCL-XL targeting in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr C032.

Sorafenib and SIAIS361034, a novel PROTAC degrader of BCL-xL, display synergistic antitumor effects on hepatocellular carcinoma with minimal hepatotoxicity

The overexpression of BCL-xL is closely associated with poor prognosis in hepatocellular carcinoma (HCC). While the strategy of combination of BCL-xL and MCL-1 for treating solid tumors has been reported, it presents significant hepatotoxicity. SIAIS361034, a novel proteolysis targeting chimera (PROTAC) agent, selectively induces the ubiquitination and subsequent proteasomal degradation of BCL-xL through the CRBN-E3 ubiquitin ligase. When combined with sorafenib, SIAIS361034 showed a potent synergistic effect in inhibiting hepatocellular carcinoma development both in vitro and in vivo. Since SIAIS361034 exhibits a high degree of selectivity for degrading BCL-xL in hepatocellular carcinoma, the hepatotoxicity typically associated with the combined inhibition of BCL-xL and MCL-1 is significantly reduced, thereby greatly enhancing safety. Mechanistically, BCL-xL and MCL-1 sequester the BH3-only protein BIM on mitochondria at baseline. Treatment with SIAIS361034 and sorafenib destabilizes BIM/BCL-xL and BIM/MCL1 association, resulting in the liberation of more BIM proteins to trigger apoptosis. Additionally, we discovered a novel compensatory regulation mechanism in hepatocellular carcinoma cells. BIM can rapidly respond to changes in the balance between BCL-xL and MCL-1 through their co-transcription factor MEF2C to maintain apoptosis resistance. In summary, the combination therapy of SIAIS361034 and sorafenib represents an effective and safe approach for inhibiting hepatocellular carcinoma progression. The novel balancing mechanism may also provide insights for combination and precision therapies in the treatment of hepatocellular carcinoma.

ONC212, alone or in synergistic conjunction with Navitoclax (ABT-263), promotes cancer cell apoptosis via unconventional mitochondrial-independent caspase-3 activation

Mitochondria-targeting agents, known as mitocans, are emerging as potent cancer therapeutics due to pronounced metabolic and apoptotic adaptations in the mitochondria of cancer cells. ONC212, an imipridone-family compound initially identified as a ClpP agonist, is currently under investigation as a potential mitocan with demonstrated preclinical efficacy against multiple malignancies. Despite this efficacy, the molecular mechanism underlying the cell death induced by ONC212 remains unclear. This study systematically investigates the mitochondrial involvement and signaling cascades associated with ONC212-induced cell death, utilizing HeLa and A549 cancer cells. Treated cancer cells exhibited characteristic apoptotic features, such as annexin-V positivity and caspase-3 activation; however, these occurred independently of typical mitochondrial events like membrane potential loss (ΔΨm) and cytochrome c release, as well as caspase-8 activation associated with the extrinsic pathway. Additionally, ONC212 treatment increased the expression of anti-apoptotic proteins Bcl-2 and Bcl-xL, which impeded apoptosis, as the overexpression of Bcl-2-GFP and Bcl-xL-GFP significantly reduced ONC212-mediated cell death. Furthermore, combining a sub-lethal dose of the Bcl-2/Bcl-xL inhibitor Navitoclax with ONC212 markedly augmented caspase-3 activation and cell death, still without any notable ΔΨm loss or cytochrome c release. Moreover, inhibition of caspase-9 activity unexpectedly augmented, rather than attenuated, caspase-3 activation and the subsequent cell death. Collectively, our research identifies ONC212 as an atypical mitochondrial-independent, yet Bcl-2/Bcl-xL-inhibitable, caspase-3-mediated apoptotic cell death inducer, highlighting its potential for combination therapies in tumors with defective mitochondrial apoptotic signaling.

Melatonin effect on breast and ovarian cancers by targeting the PI3K/Akt/mTOR pathway.

Melatonin, the hormone of the pineal gland, possesses a range of physiological functions, and recently, its anticancer effect has become more apparent. A more thorough understanding of molecular alterations in the components of several signaling pathways as new targets for cancer therapy is needed because of current innate restrictions such as drug toxicity, side effects, and acquired or de novo resistance. The PI3K/Akt/mTOR pathway is overactivated in many solid tumors, such as breast and ovarian cancers. This pathway in normal cells is essential for growth, proliferation, and survival. However, it is an undesirable characteristic in malignant cells. We have reviewed multiple studies about the effect of melatonin on breast and ovarian cancer, focusing on the PI3K/Akt/mTOR pathway. Melatonin exerts its inhibitory effects via several mechanisms. A: Downregulation of downstream or upstream components of the signaling pathway such as phosphatase and tensin homolog (PTEN), phosphatidylinositol (3,4,5)-trisphosphate kinase (PI3K), p-PI3K, Akt, p-Akt, mammalian target of rapamycin (mTOR), and mTOR complex1 (mTORC1). B: Apoptosis induction by decreasing MDM2 expression, a downstream target of Akt, and mTOR, which leads to Bad activation in addition to Bcl-XL and p53 inhibition. C: Induction of autophagy in cancer cells via activating ULK1 after mTOR inhibition, resulting in Beclin-1 phosphorylation. Beclin-1 with AMBRA1 and VPS34 promotes PI3K complex I activity and autophagy in cancer cells. The PI3K/Akt/mTOR pathway overlaps with other intracellular signaling pathways and components such as AMP-activated protein kinase (AMPK), Wnt/β-catenin, mitogen-activated protein kinase (MAPK), and other similar pathways. Cancer therapy can benefit from understanding how these pathways interact and how melatonin affects these pathways.

Chromosome instability functions as a potential therapeutic reference by enhancing chemosensitivity to BCL-XL inhibitors in colorectal carcinoma.

Chromosome instability (CIN) and subsequent aneuploidy are prevalent in various human malignancies, influencing tumor progression such as metastases and relapses. Extensive studies demonstrate the development of chemoresistance in high-CIN tumors, which poses significant therapeutic challenges. Given the association of CIN with poorer prognosis and suppressed immune microenvironment observed in colorectal carcinoma (CRC), here we aimed to discover chemotherapeutic drugs exhibiting increased inhibition against high-CIN CRC cells. By using machine learning methods, we screened out two BCL-XL inhibitors Navitoclax and WEHI-539 as CIN-sensitive reagents in CRC. Subsequent analyses using a CIN-aneuploidy cell model confirmed the vulnerability of high-CIN CRC cells to these drugs. We further revealed the critical role of BCL-XL in the viability of high-CIN CRC cells. In addition, to ease the evaluation of CIN levels in clinic, we developed a three-gene signature as a CIN surrogate to predict prognosis, chemotherapeutic and immune responses in CRC samples. Our results demonstrate the potential value of CIN as a therapeutic target in CRC treatment and the importance of BCL-XL in regulating survival of high-CIN CRC cells, therefore representing a valuable attempt to translate a common trait of heterogeneous tumor cells into an effective therapeutic target.

Mitochondria of T Lymphocytes Promote Anti-Pulmonary Tumor Immune Response.

B-cell lymphoma 2 (Bcl-2), a protein involved in apoptosis, has been proven to have carcinogenic potential and is well documented. With the recent advancement in optical technology, it has become possible to observe subcellular organelles such as mitochondria in real-time without the need for staining. Consequently, we have examined the movement of mitochondria in cancer cells, correlating it with the regulation of Bcl-2. Using a tomographic microscope, which can detect the internal structure of cells, we observed lung tumor cells. Cells were exposed to a laser beam (λ = 520 nm) inclined at 45°, and holographic images were recorded up to a depth of 30 µm of reconstruction. Intriguingly, lung tumor cells rapidly expelled mitochondria upon the attachment of Bcl-2 or B-cell lymphoma extra-large (Bcl-xL) inhibitors. On the other hand, we observed that tumor cells hijack mitochondria from T cells. The hijacked mitochondria were not immediately linked to tumor cell death, but they played a role in assisting granzyme B-induced tumor cell death. Due to lower levels of Bcl-2 and Bcl-xL on the mitochondria of T cells compared to lung tumor cells, immune cells depleted of Bcl-2 and Bcl-xL were co-cultured with the tumor cells. As a result, a more effective tumor cell death induced by granzyme B was observed. Additionally, further enhanced anticancer immune response was observed in vivo. Together, we show that modified mitochondria of T cells can provide potential novel strategies towards tumor cell death.

Involvement of Janus kinase-dependent Bcl-xL overexpression in steroid resistance of group 2 innate lymphoid cells in asthma.

The mechanisms underlying the development of steroid resistance in asthma remain unclear. To establish whether as well as the mechanisms by which the activation of Janus kinases (JAKs) is involved in the development of steroid resistance in asthma, murine steroid-resistant models of the proliferation of group 2 innate lymphoid cells (ILC2s) in vitro and asthmatic airway inflammation in vivo were analysed. ILC2s in the lungs of BALB/c mice were sorted and then incubated with IL-33, thymic stromal lymphopoietin (TSLP), and/or IL-7 with or without dexamethasone (10 nM), the pan-JAK inhibitor, delgocitinib (1-10 000 nM), and/or the Bcl-xL inhibitor, navitoclax (1-100 nM), followed by the detection of viable and apoptotic cells. The anti-apoptotic factor, Bcl-xL was detected in ILC2s by flow cytometry. As a steroid-resistant asthma model, ovalbumin (OVA)-sensitized BALB/c mice were intratracheally challenged with OVA at a high dose of 500 μg four times. Dexamethasone (1 mg/kg, i.p.), delgocitinib (3-30 mg/kg, p.o.), or navitoclax (30 mg/kg, p.o.) was administered during the challenges. Cellular infiltration into the lungs was analysed by flow cytometry. Airway remodelling was histologically evaluated. The following results were obtained. (1) Cell proliferation concomitant with a decrease in apoptotic cells was induced when ILC2s were cultured with TSLP and/or IL-7, and was potently inhibited by dexamethasone. In contrast, when the culture with TSLP and IL-7 was performed in the presence of IL-33, the proliferative response exhibited steroid resistance. Steroid-resistant ILC2 proliferation was suppressed by delgocitinib in a concentration-dependent manner. (2) The culture with IL-33, TSLP, and IL-7 induced the overexpression of Bcl-xL, which was clearly inhibited by delgocitinib, but not by dexamethasone. When ILC2s were treated with navitoclax, insensitivity to dexamethasone was significantly cancelled. (3) The development of airway remodelling and the infiltration of ILC2s into the lungs in the asthma model were not suppressed by dexamethasone, but were dose-dependently inhibited by delgocitinib. Combination treatment with dexamethasone and either delgocitinib or navitoclax synergistically suppressed these responses. Therefore, JAKs appear to play significant roles in the induction of steroid resistance by up-regulating Bcl-xL in ILC2s. The inhibition of JAKs and Bcl-xL has potential as pharmacotherapy for steroid-resistant asthma, particularly that mediated by ILC2s.

Improved drug target deconvolution with PISA-DIA using an extended, overlapping temperature gradient.

Thermal proteome profiling (TPP) is a powerful tool for drug target deconvolution. Recently, data-independent acquisition mass spectrometry (DIA-MS) approaches have demonstrated significant improvements to depth and missingness in proteome data, but traditional TPP (a.k.a. CEllular Thermal Shift Assay "CETSA") workflows typically employ multiplexing reagents reliant on data-dependent acquisition (DDA). Herein, we introduce a new experimental design for the Proteome Integral Solubility Alteration via label-free DIA approach (PISA-DIA). We highlight the proteome coverage and sensitivity achieved by using multiple overlapping thermal gradients alongside DIA-MS, which maximizes efficiencies in PISA sample concatenation and safeguards against missing protein targets that exist at high melting temperatures. We demonstrate our extended PISA-DIA design has superior proteome coverage as compared to using tandem-mass tags (TMT) necessitating DDA-MS analysis. Importantly, we demonstrate our PISA-DIA approach has the quantitative and statistical rigor using A-1331852, a specific inhibitor of BCL-xL. Due to the high melt temperature of this protein target, we utilized our extended multiple gradient PISA-DIA workflow to identify BCL-xL. We assert our novel overlapping gradient PISA-DIA-MS approach is ideal for unbiased drug target deconvolution, spanning a large temperature range whilst minimizing target dropout between gradients, increasing the likelihood of resolving the protein targets of novel compounds.

Blockage of BCL-XL overcomes venetoclax resistance across BCL2+ lymphoid malignancies irrespective of BIM status

AbstractVenetoclax (VEN), a B-cell lymphoma 2 (BCL2) inhibitor, has a promising single-agent activity in mantle cell lymphoma (MCL), acute lymphoblastic leukemia (ALL), and large BCLs, but remissions were generally short, which call for rational drug combinations. Using a panel of 21 lymphoma and leukemia cell lines and 28 primary samples, we demonstrated strong synergy between VEN and A1155463, a BCL-XL inhibitor. Immunoprecipitation experiments and studies on clones with knockout of expression or transgenic expression of BCL-XL confirmed its key role in mediating inherent and acquired VEN resistance. Of note, the VEN and A1155463 combination was synthetically lethal even in the cell lines with lack of expression of the proapoptotic BCL2L11/BIM and in the derived clones with genetic knockout of BCL2L11/BIM. This is clinically important because BCL2L11/BIM deletion, downregulation, or sequestration results in VEN resistance. Immunoprecipitation experiments further suggested that the proapoptotic effector BAX belongs to principal mediators of the VEN and A1155463 mode of action in the BIM-deficient cells. Lastly, the efficacy of the new proapoptotic combination was confirmed in vivo on a panel of 9 patient–derived lymphoma xenografts models including MCL (n = 3), B-ALL (n = 2), T-ALL (n = 1), and diffuse large BCL (n = 3). Because continuous inhibition of BCL-XL causes thrombocytopenia, we proposed and tested an interrupted 4 days on/3 days off treatment regimen, which retained the desired antitumor synergy with manageable platelet toxicity. The proposed VEN and A1155463 combination represents an innovative chemotherapy-free regimen with significant preclinical activity across diverse BCL2+ hematologic malignancies irrespective of the BCL2L11/BIM status.

Abstract CT146: AZD0466 in patients with advanced non-Hodgkin lymphoma: Efficacy and safety in an open-label phase 1 trial

Abstract Background Overexpression of pro-survival proteins Bcl-2 and Bcl-xL have been associated with poor prognosis in patients with non-Hodgkin lymphoma (NHL). AZD0466 is a drug-dendrimer conjugate consisting of the dual Bcl-2/Bcl-xL inhibitor AZD4320 covalently conjugated to a pegylated poly-L-lysine dendrimer, which allows for gradual release by hydrolysis. Preclinically, AZD0466 monotherapy has demonstrated efficacy in xenograft models of diffuse large B-cell lymphoma (DLBCL). Here, we report results from a Phase 1 trial (NCT05205161) of AZD0466 in relapsed/refractory (R/R) advanced B-cell NHL (B-NHL). Methods Eligible patients were ≥18 years old and had received 2-5 prior lines of therapy. AZD0466 was administered intravenously, with a dose ramp-up on days 1 and 4 of a 28-day cycle, and weekly administration of the target dose from day 8. The primary objective of the dose escalation phase was to assess the safety and tolerability of AZD0466 in patients with R/R B-NHL and to identify the maximum tolerated dose and recommended phase 2 dose. Preliminary efficacy was evaluated using Lugano 2014 criteria. Secondary objective was evaluation of pharmacokinetic (PK) parameters for the study drug. Results As of November 02, 2023, 7 patients (DLBCL n=5, follicular lymphoma n=1, marginal zone lymphoma (MZL) n=1; median age, 57 [26−79] years) had received AZD0466 at 600 mg (n=3), 1200 mg (n=3), or 2400 mg (n=1). All patients experienced adverse events (AEs). AEs possibly related to AZD0466 were reported in 6 patients, most common: platelet count decrease (57.1%), neutropenia/neutrophil count decrease (42.9%), and hypophosphatemia (28.6%). Grade ≥3 AEs possibly related to AZD0466 were reported in 4 patients: 2 Grade 3 and 1 Grade 4 neutropenia/neutrophil count decrease, and 2 AEs that led to treatment discontinuation (Grade 3 platelet count decrease and dose-limiting Grade 3 troponin increase). Among 6 evaluable patients across all dose levels, 1 patient with MZL treated at 1200 mg had an objective response (partial response). Another 3 patients had a best overall response of stable disease and 2 patients had progressive disease. One patient discontinued the study prior to disease assessment. AZD4320 exposure was dose-proportional, with PK profiles similar to studies with other hematologic malignancies. As a surrogate of Bcl-xL on-target activity, transient thrombocytopenia with moderate platelet count recovery prior to the next dose was observed in most patients, in line with preclinical modeling. Pharmacodynamic modulation based on cleaved caspase-3 induction by AZD0466 was observed at 1200 and 2400 mg. Conclusion AZD0466 ≤1200 mg was clinically well tolerated but evidence of asymptomatic myocardial injury was observed at 2400 mg. The study was terminated due to similar findings in a concurrent trial (D8241C00001; NIMBLE). With an objective response observed at the 1200 mg dose level, further development of agents targeting Bcl-2/xL in NHL is warranted with efforts to reduce the cardiotoxicity profile. Citation Format: Geoffrey Chong, Franck Morschhauser, Alex Herrera, Ki-Seong Eom, Tae Min Kim, Michael Wang, Connor Hall, Fathima Zumla Cader, Kaitlyn Beyfuss, Patricia Cheung, Wei Quan, Shringi Sharma, Yotvat Marmor, Jamal Saeh, Jose Mariz. AZD0466 in patients with advanced non-Hodgkin lymphoma: Efficacy and safety in an open-label phase 1 trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT146.

Senolysis of gemcitabine-induced senescent human pancreatic cancer cells.

Gemcitabine (GEM) is often used to treat pancreatic cancer. Many anti-cancer drugs induce cancer cell death, but some cells survive after cell cycle arrest. Such a response to DNA damage is termed cellular senescence. Certain drugs, including the Bcl-2-family inhibitor ABT-263, kill senescent cells; this is termed senolysis. In this study, we examined the therapeutic benefits of ABT-263 in GEM-induced senescence of human pancreatic cancer cells. Of four pancreatic cancer cell lines (PANC-1, AsPC-1, CFPAC-1, and PANC10.05), GEM induced senescent features in PANC-1 and AsPC-1 cells, including increases in the cell sizes and expression levels of mRNAs encoding interleukin (IL)-6/IL-8 and induction of β-galactosidase. Successive treatment with GEM and ABT-263 triggered apoptosis in PANC-1 and AsPC-1 cells and suppressed colony formation significantly. Senolysis of GEM-induced senescent pancreatic cancer cells by ABT-263 was triggered by a Bcl-xL inhibitor, but not by a Bcl-2 inhibitor, suggesting a central role for Bcl-xL in senolysis. In a xenograft mouse model, combined treatment with GEM and ABT-737 (an ABT-263 analog exhibiting the same specificity) suppressed in vivo growth of AsPC-1 significantly. Together, our results indicate that sequential treatment with GEM and senolytic drugs effectively kill human pancreatic cancer cells.

AMPK inhibition sensitizes acute leukemia cells to BH3 mimetic-induced cell death.

BH3 mimetics, including the BCL2/BCLXL/BCLw inhibitor navitoclax and MCL1 inhibitors S64315 and tapotoclax, have undergone clinical testing for a variety of neoplasms. Because of toxicities, including thrombocytopenia after BCLXL inhibition as well as hematopoietic, hepatic and possible cardiac toxicities after MCL1 inhibition, there is substantial interest in finding agents that can safely sensitize neoplastic cells to these BH3 mimetics. Building on the observation that BH3 mimetic monotherapy induces AMP kinase (AMPK) activation in multiple acute leukemia cell lines, we report that the AMPK inhibitors (AMPKis) dorsomorphin and BAY-3827 sensitize these cells to navitoclax or MCL1 inhibitors. Cell fractionation and phosphoproteomic analyses suggest that sensitization by dorsomorphin involves dephosphorylation of the proapoptotic BCL2 family member BAD at Ser75 and Ser99, leading BAD to translocate to mitochondria and inhibit BCLXL. Consistent with these results, BAD knockout or mutation to BAD S75E/S99E abolishes the sensitizing effects of dorsomorphin. Conversely, dorsomorphin synergizes with navitoclax or the MCL1 inhibitor S63845 to induce cell death in primary acute leukemia samples ex vivo and increases the antitumor effects of navitoclax or S63845 in several xenograft models in vivo with little or no increase in toxicity in normal tissues. These results suggest that AMPK inhibition can sensitize acute leukemia to multiple BH3 mimetics, potentially allowing administration of lower doses while inducing similar antineoplastic effects.

Abstract 231: Live cell painting of drug responses in high grade serous cancer organoids

Abstract While most patients with high grade serous ovarian cancer (HGSC) respond to platinum-based chemotherapy, the response is rarely durable and recurrence almost inevitable. A characteristic of HGSC is defective DNA repair. A class of drugs called PARP inhibitors (PARPi) exploit this vulnerability and have proven useful in delaying recurrence. However, resistance is inevitable. In models of HGSC a protein that frequently confers resistance is called Bcl-xL, a member of the Bcl-2 family of proteins that prevent apoptosis. If treating the patients with a PARPi makes cancer cells dependent on Bcl-xL then adding an inhibitor of Bcl-xL to their treatment would be sufficient to cause the cancer cells to die. To test this, we have initiated companion studies for a clinical trial in which patients that have had a recurrence after receiving platinum-based therapy will first be treated with the PARPi Olaparib and then, an inhibitor of Bcl-xL, Navitoclax, will be added to their course of treatment. The idea is that for some women this will provide the one-two-punch needed to eliminate the cancer or at least dramatically prolong response. However, Bcl-xL is only one of the five known inhibitors of apoptosis. To identify which women will benefit most from adding Navitoclax to their treatment we need a biomarker(s). An ideal biomarker would also let us determine for other women which inhibitor of Bcl-2 proteins would be best combined with a PARPi. Our hypothesis is that patient derived organoids can be used as a pragmatic way to identify for individual patients which Bcl-2 protein inhibitor will synergize with a PARPi to optimize treatment. We are using organoids to develop biomarkers for High Grade Serous Cancer (HGSC) treatment response. Organoids generated from biopsy samples acquired prior to treatment for HGSC promise to be efficient and reliable experimental models that recapitulate in vitro patient tumors faithfully enough to facilitate translation to therapeutic decisions for patients. By adapting the relatively new technique of conditional reprogramming and combining it with novel methods for cell aggregation and hydrogel based synthetic ECM supports we can reproducibly generate HGSC patient-specific tumor organoids models in weeks with greater than 90% success. Organoids grown 384 well format are stained with novel non-toxic dyes enabling live cell painting of chemoresponses to drugs alone and in combination with drugs targeting anti-apoptotic proteins. Our data suggest that this approach captures the inherent heterogeneity of the disease, albeit local to the sampled site. We are now employing deep learning AI algorithms to enable automated analyses of 3D confocal image stacks of organoids to infer drug responses that will be compared to patient responses in ongoing clinical trials. Citation Format: David W. Andrews, Betty Li, Wiebke Schormann, Alla Buzina, Lilian Gien, Helen MacKay. Live cell painting of drug responses in high grade serous cancer organoids [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 231.

Abstract 690: Investigation of BH-3 mimetics as radiosensitizing agents in glioblastoma

Abstract Glioblastoma (GBM) is a highly aggressive primary brain tumor. Treatment consists of maximal safe tumor resection, chemotherapy (temozolomide) and radiotherapy; however, this aggressive treatment offers only a modest improvement in outcomes, with average life expectancy of approximately 12 months. Consequently, novel, effective and easily translatable therapies are urgently required. While radiotherapy is an effective treatment for many solid tumors, GBM displays an innate radio-resistance that contributes to treatment failure. Therefore, there is a need to identify chemotherapeutics that can be used as radiosensitizers to increase efficacy. Notably, a key pathway involved in therapeutic resistance is apoptotic evasion, which is driven by upregulation of pro-survival BCL-2 proteins that inhibit the pro-apoptotic proteins necessary for the apoptotic response. Recent advances in drug development have produced a range of BH3 mimetics - novel chemotherapeutics with potential to reinstate apoptosis by targeting specific pro-survival molecules. We hypothesized that the radiation sensitivity of GBM cells would be enhanced by using BH3 mimetics to inhibit pro-survival molecules and release the apoptotic block. A panel of BH3 mimetics was tested in combination with radiotherapy across three patient-derived GBM cell lines (G7, E2 and R15), using a 3D clonogenic culture system that recapitulates in vivo growth patterns and responses. We found that the BCL-XL inhibitor, A1331852, significantly radiosensitized all 3 GBM lines. In addition, Western blot analysis revealed A1331852 to induce PARP1 cleavage in G7 cells when used as a single agent. Subsequent in vivo studies were conducted in our well characterized orthotopic G7 xenograft murine model of GBM. Immunohistochemical studies showed that the pro-survival proteins MCL-1 and BCL-XL were upregulated in irradiated tumors. Furthermore, a pharmacokinetic study in the same orthotopic murine model, allowing for drug delivery evaluation, and optimized treatment scheduling. Importantly, A1331852 was found to be blood brain barrier penetrant at 25 mg/kg, with increased drug detected in tumor vs normal brain tissue. From these data, a survival study investigating A1331852 as a radiosensitizing agent was carried out in the same G7 GBM orthotopic xenograft model. Kaplan-Meier analysis showed an increase in survival of mice treated with A133852 plus radiotherapy compared with the radiotherapy only group (p = 0.0309). Overall, we have demonstrated that dependence on BCL-2 family proteins is a vulnerability that can be targeted to improve radiotherapy response in GBM. Furthermore, we have identified a promising BH3 mimetic, A1331852, to use in combination with RT and have completed a proof-of-concept in vivo study that confirms the potential of BH3 mimetics to improve outcomes for patients with GBM. Citation Format: Louise R. Dutton, Clara Mullen, Anna L. Koessinger, Mark Jackson, Katrina Stevenson, Anthony J. Chalmers, Stephen Tait, Kirsteen J. Campbell, Joanna L. Birch. Investigation of BH-3 mimetics as radiosensitizing agents in glioblastoma [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 690.

Abstract 7223: A triplet therapeutic strategy targeting MEK, BCL-XL, and EGFR, for KRAS-mutant pancreatic ductal adenocarcinoma

Abstract KRAS mutations drive over 90% of pancreatic cancers, but KRAS has been proven difficult to target. Downstream of KRAS, MEK inhibition in combination with BCL-XL inhibition is synthetically lethal and an effective treatment for gynecologic, but not colorectal malignancies. Like colorectal cancer, pancreatic cancer often exhibits aberrant HER/EGFR activity. We hypothesized that a triplicate regimen targeting MEK, BCL-XL, and EGFR/HER would be effective for pancreatic cancer. Trametinib (MEK inhibitor), Afatinib (pan-EGFR/HER inhibitor), and Navitoclax (BCL-XL inhibitor); or DT2216 (a BCL-XL/BCL-1 proteolysis targeting chimera, PROTAC) were explored using various combinatorial strategies. These drug combinations were tested using four primary human pancreatic cancer cell lines using live cell imaging (Incucyte) and an in vivo murine model. Group comparisons were analyzed using one-way ANOVAs, and adjusted p-values <0.05 were considered significant. We observed that no single-agent treatments were effective. MEK inhibition plus anti-BCL-XL (Trametinib + Navitoclax or Trametinib + DT2216) demonstrated efficacy in one of the four cell lines. We noted synergistic effects on reduced cell growth and increased cell death when EGFR/HER inhibition was included by the administration of Afatinib. The triplet combination resulted in synergistic effects in three of four cell lines with Navitoclax and four of four cell lines with DT2216 (q<0.05). This effect was confirmed with DT2216 inhibition of BCL-XL in an in-vivo murine model. In conclusion, our study shows that a combinatory strategy targeting MEK, BCL-XL, and pan-EGFR/HER receptor kinase shows significant synergistic effects in pancreatic cancer. Clinical trials that assess the efficacy and safety of this strategy for patients with KRAS-mutant pancreatic cancer are warranted. Our data also suggests that novel KRAS inhibitors as monotherapy are likely to fail. Citation Format: Gerik W. Tushoski-Alemán, Alexandra J. Crespin, Chibeze J. Oguejiofor, Jordan A. McKean, Kelly M. Herremans, Thomas J. George, Carmen J. Allegra, Steven J. Hughes, Song Han. A triplet therapeutic strategy targeting MEK, BCL-XL, and EGFR, for KRAS-mutant pancreatic ductal adenocarcinoma [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 7223.