ADCT-602, a Novel PBD Dimer-containing Antibody-Drug Conjugate for Treating CD22-positive Hematologic Malignancies

Relapsed or refractory B-cell acute lymphoblastic leukemia (R/R B-ALL) and lymphomas have poor patient outcomes; novel therapies are needed. CD22 is an attractive target for antibody-drug conjugates (ADCs), being highly expressed in R/R B-ALL with rapid internalization kinetics. ADCT-602 is a novel CD22-targeting ADC, consisting of humanized mAb hLL2-C220, site specifically conjugated to the pyrrolobenzodiazepine dimer-based payload tesirine. In preclinical studies, ADCT-602 demonstrated potent, specific cytotoxicity in CD22-positive lymphomas and leukemias. ADCT-602 was specifically bound, internalized, and trafficked to lysosomes in CD22-positive tumor cells; after cytotoxin release, DNA interstrand crosslink formation persisted for 48 hours. In the presence of CD22-positive tumor cells, ADCT-602 caused bystander killing of CD22-negative tumor cells. A single ADCT-602 dose led to potent, dose-dependent, in vivo antitumor activity in subcutaneous and disseminated human lymphoma/leukemia models. Pharmacokinetic analyses (rat and cynomolgus monkey) showed excellent stability and tolerability of ADCT-602. Cynomolgus monkey B cells were efficiently depleted from circulation after one dose. Gene signature association analysis revealed IRAK1 as a potential marker for ADCT-602 resistance. Combining ADCT-602 + pacritinib was beneficial in ADCT-602-resistant cells. Chidamide increased CD22 expression on B-cell tumor surfaces, increasing ADCT-602 activity. These data support clinical testing of ADCT-602 in R/R B-ALL (NCT03698552) and CD22-positive hematologic cancers.

ERBB4-Mediated Signaling Is a Mediator of Resistance to PI3K and BTK Inhibitors in B-cell Lymphoid Neoplasms

BTK and PI3K inhibitors are among the drugs approved for the treatment of patients with lymphoid neoplasms. Although active, their ability to lead to long-lasting complete remission is rather limited, especially in the lymphoma setting. This indicates that tumor cells often develop resistance to the drugs. We started from a marginal zone lymphoma cell line, Karpas-1718, kept under prolonged exposure to the PI3Kδ inhibitor idelalisib until acquisition of resistance, or with no drug. Cells underwent transcriptome, miRNA and methylation profiling, whole-exome sequencing, and pharmacologic screening, which led to the identification of the overexpression of ERBB4 and its ligands HBEGF and NRG2 in the resistant cells. Cellular and genetic experiments demonstrated the involvement of this axis in blocking the antitumor activity of various BTK/PI3K inhibitors, currently used in the clinical setting. Addition of recombinant HBEGF induced resistance to BTK/PI3K inhibitors in parental cells and in additional lymphoma models. Combination with the ERBB inhibitor lapatinib was beneficial in resistant cells and in other lymphoma models already expressing the identified resistance factors. An epigenetic reprogramming sustained the expression of the resistance-related factors, and pretreatment with demethylating agents or EZH2 inhibitors overcame the resistance. Resistance factors were also shown to be expressed in clinical specimens. In conclusion, we showed that the overexpression of ERBB4 and its ligands represents a novel mechanism of resistance for lymphoma cells to bypass the antitumor activity of BTK and PI3K inhibitors and that targeted pharmacologic interventions can restore sensitivity to the small molecules.

The ATR inhibitor elimusertib exhibits anti-lymphoma activity and synergizes with the PI3K inhibitor copanlisib

The DNA damage response (DDR) is the cellular process of preserving an intact genome and is often deregulated in lymphoma cells. The ataxia telangiectasia and Rad3-related (ATR) kinase is a crucial factor of DDR in the response to DNA single-strand breaks. ATR inhibitors are agents that have shown considerable clinical potential in this context. We characterized the activity of the ATR inhibitor elimusertib (BAY 1895344) in a large panel of lymphoma cell lines. Furthermore, we evaluated its activity combined with the clinically approved PI3K inhibitor copanlisib in vitro and in vivo. Elimusertib exhibits potent anti-tumour activity across various lymphoma subtypes, which is associated with the expression of genes related to replication stress, cell cycle regulation and, as also sustained by CRISPR Cas9 experiments, CDKN2A loss. In several tumour models, elimusertib demonstrated widespread anti-tumour activity stronger than ceralasertib, another ATR inhibitor. This activity is present in both DDR-proficient and DDR-deficient lymphoma models. Furthermore, a combination of ATR and PI3K inhibition by treatment with elimusertib and copanlisib has in vitro and in vivo anti-tumour activity, providing a potential new treatment option for lymphoma patients.

PI3Kδ activation, IL6 over-expression, and CD37 loss cause resistance to the targeting of CD37-positive lymphomas with the antibody-drug conjugate naratuximab emtansine

Purpose

The transmembrane protein CD37 is expressed almost exclusively in lymphoid tissues, with the highest abundance in mature B cells. CD37-directed antibody- and, more recently, cellular-based approaches have shown preclinical and promising early clinical activity. Naratuximab emtansine (Debio 1562, IMGN529) is an antibodydrug conjugate (ADC) that incorporates an anti-CD37 monoclonal antibody conjugated to the maytansinoid DM1 as payload. Naratuximab emtansine has shown activity as a single agent and in combination with the anti-CD20 monoclonal antibody rituximab in B cell lymphoma patients.

Experimental Design

We assessed the activity of naratuximab emtansine using in vitro models of lymphomas, correlated its activity with CD37 expression levels, characterized two resistance mechanisms to the ADC, and identified combination partners providing synergy.

Results

The anti-tumor activity of naratuximab emtansine was tested in 54 lymphoma cell lines alongside its free payload. The median IC 50 of naratuximab emtansine was 780 pM, and the activity, primarily cytotoxic, was more potent in B than in T cell lymphoma cell lines. In the subgroup of cell lines derived from B cell lymphoma, there was some correlation between sensitivity to DM1 and sensitivity to naratuximab emtansine (r=0.28, P = 0.06). After prolonged exposure to the ADC, one diffuse large B cell lymphoma (DLBCL) cell line developed resistance to the ADC due to the biallelic loss of the CD37 gene. After CD37 loss, we also observed upregulation of IL6 (IL-6) and other transcripts from MYD88/IL6-signaling. Recombinant IL6 led to resistance to naratuximab emtansine, while the anti-IL6 antibody tocilizumab improved the cytotoxic activity of the ADC in CD37-positive cells. In a second model, resistance was sustained by an activating mutation in the PIK3CD gene, associated with increased sensitivity to PI3K δ inhibition and a switch from functional dependence on the anti-apoptotic protein MCL1 to reliance on BCL2. The addition of idelalisib or venetoclax to naratuximab emtansine overcame resistance to the ADC in the resistant derivative while also improving the cytotoxic activity of the ADC in the parental cells.

Conclusions

Targeting B cell lymphoma with the CD37 targeting ADC naratuximab emtansine showed vigorous anti-tumor activity as a single agent, which was also observed in models bearing genetic lesions associated with inferior outcomes, such as MYC translocations and TP53 inactivation or resistance to R-CHOP. Resistance DLBCL models identified active combinations of naratuximab emtansine with drugs targeting IL6, PI3K δ , and BCL2. Despite notable progress in recent decades, we still face challenges in achieving a cure for a substantial number of lymphoma patients (1,2). A pertinent example is diffuse large B cell lymphoma (DLBCL), the most prevalent type of lymphoma (3). More than half of DLBCL patients can achieve remission, but around 40% of them experience refractory disease or relapse following an initial positive response (3). Regrettably, the prognosis for many of these cases remains unsatisfactory despite introducing the most recent antibody-based or cellular therapies (3,4), underscoring the importance of innovating new therapeutic strategies and gaining insights into the mechanisms of therapy resistance. CD37 is a transmembrane glycoprotein belonging to the tetraspanin family, primarily expressed on the surface of immune cells, principally in mature B cells but also, at lower levels, in T cells, macrophages/monocytes, granulocytes and dendritic cells (5) (6-8). CD37 plays a crucial role in various immune functions, including B cell activation, proliferation, and signaling, although its precise role still needs to be fully elucidated. CD37 interacts with multiple molecules, including SYK, LYN, CD19, CD22, PI3K δ , PI3K γ , and different integrins, among others (6-8). In mice, the lack of CD37 is paired with reduced T cell-dependent antibody-secreting cells and memory B cells, apparently due to the loss of CD37-mediated clustering of α 4 β 1 integrins (VLA-4) on germinal center B cells and decreased downstream activation of PI3K/AKT signaling and cell survival (5). Reflecting the expression pattern observed in normal lymphocytes, CD37 exhibits elevated expression in all mature B-cell lymphoid neoplasms, including most lymphoma subtypes, and absence in early progenitor cells or terminally differentiated plasma cells (6,8-14). In DLBCL, CD37 expression has been reported between 40% and 90% of cases across multiple studies performed using different antibodies (10,14-16). CD37-directed antibody- and, more recently, cellular-based approaches have shown preclinical (7,10-14,17-23) and early promising clinical activity (24-32). Among the CD37-targeting agents, naratuximab emtansine (Debio 1562, IMGN529) is an antibody-drug conjugate (ADC) that incorporates the anti-CD37 humanized IgG1 monoclonal antibody K7153A conjugated to the maytansinoid DM1, as payload, via the thioether linker, N-succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC) (10). Based on the initial in vitro and in vivo evidence of anti-tumor activity in lymphoma and chronic lymphocytic leukemia (CLL) (7,10), naratuximab emtansine entered the clinical evaluation as a single agent. The phase 1 study exploring naratuximab emtansine enrolled 39 patients with relapsed/refractory B cell lymphoma (27). The overall response rate (ORR) was 13% across all patients and 22% in DLBCL patients, including the only observed complete remission (CR) (27). In preliminary results of a phase 2 trial exploring the combination of naratuximab emtansine with the anti-CD20 monoclonal antibody rituximab (18), based on positive preclinical data (18), the ORR was 45% in 76 patients with DLBCL with 24 CRs (32%), 57% in 14 patients with follicular lymphoma (five CR), 50% in four MCL patients (2 CR) (31). Here, we studied the pattern of activity of naratuximab emtansine across a large panel of cell lines derived from DLBCL and other lymphoma subtypes and characterized two resistance mechanisms to the ADC.

A DNA biosensors-based microfluidic platform for attomolar real-time detection of unamplified SARS-CoV-2 virus

The emergence of the coronavirus 2019 (COVID-19) arose the need for rapid, accurate and massive virus detection methods to control the spread of infectious diseases. In this work, a device, deployable in non-medical environments, has been developed for the detection of non-amplified SARS-CoV-2 RNA. A SARS-CoV-2 specific probe was designed and covalently immobilized at the surface of glass slides to fabricate a DNA biosensor. The resulting system was integrated in a microfluidic platform, in which viral RNA was extracted from non-treated human saliva, before hybridizing at the surface of the sensor. The formed DNA/RNA duplex was detected in presence of SYBR Green I using an opto-electronic system, based on a high-power LED and a photo multiplier tube, which convert the emitted fluorescence into an electrical signal that can be processed in less than 10 min. The limit of detection of the resulting microfluidic platform reached six copies of viral RNA per microliter of sample (equal to 10 aM) and satisfied the safety margin. The absence of non-specific adsorption and the selectivity for SARS-CoV-2 RNA were established. In addition, the designed device could be applicable for the detection of a variety of viruses by simple modification of the immobilized probe.

Abstract 394: ERBB4-mediated signaling is a mediator of resistance to BTK and PI3K inhibitors in B cell lymphoid neoplasms

Background: Marginal zone lymphoma (MZL) is an indolent yet incurable B cell malignancy. Two BTK inhibitors, ibrutinib and zanubrutinib, are FDA approved for relapsed/refractory MZL patients. PI3K inhibitors have also shown clinical activity. The identification of the mechanisms of resistance can provide useful information to optimize the use of the agents. We previously reported an IL6 driven MZL model of PI3K inhibitors resistance developed by prolonged exposure to the PI3Kδ inhibitor idelalisib (Arribas, Haematologica 2022). Here, we present the detailed characterization of a second model with resistance to both BTK and PI3K inhibitors.

Methods: MTT assay. RNA-Seq, whole exome sequencing, miRNA and methylation profiling. FACS and ELISA analyses.

Results: Resistant cells, developed by continuous exposure of the cell line Karpas1718 to idelalisib, showed resistance to various inhibitors of BTK (ibrutinib, zanubrutinib, acalabrutinib and pirtobrutinib) and PI3K (idelalisib, duvelisib, copanlisib and umbralisib). No mutations affecting BTK, PLCG2 or CXCR4 were identified in resistant cells, which had higher expression of genes involved in ERBB signaling (HBEGF, NRG2, ERBB4), cell proliferation (PBK, MKI67, TCL1A) and DNA recombination (RAG1, RAG2) than parental cells. We confirmed cell surface ERBB4 up-regulation, and the cytoplasmatic expression and secretion of its ligand HBEGF in resistant cells, which led to increased levels of p-AKT and p-ERK. The miRNAs miR-29c and let-7c, known negative regulators of the HBEGF-ERBB axis, were fully methylated and down-regulated in resistant compared to parental cells. ERBB4 genetic silencing improved sensitivity to PI3Kδ inhibitor, and exposure to let-7c or miR-29c mimics decreased secreted HBEGF and recovered sensitivity to PI3K inhibitors in resistant cells. Addition of recombinant HBEGF (rHBEGF) induced resistance to BTK and to PI3K inhibitors in parental cells and in other lymphoma models including mantle cell lymphomas and diffuse large B cell lymphomas (DLBCL). The rHBEGF induced resistance was reverted adding the ERBB inhibitor lapatinib. To extend our findings to the clinical context, using two MZL and one DLBCL expression datasets, we showed HBEGF and ERBB4 expression in clinical specimens. Finally, HBEGF levels appeared elevated in the serum of CLL patients with primary or acquired resistance to PI3Kδ or to BTK inhibitors, compared to patients responding to the drugs and paired for similar clinical features.

Conclusions: We characterized a novel B cell lymphoma model of secondary resistance to BTK and PI3K inhibitors. Our results indicate that epigenetic plasticity led to the activation of HBEGF-ERBB signaling sustaining resistance to BTK/PI3K inhibitors, which can be overcome using epigenetic agents and ERBB inhibitors. These therapeutics approaches could be tested in novel clinical trials. AJA, SN: equally contributed.

Citation Format: Alberto J. Arribas, Sara Napoli, Luciano Cascione, Laura Barnabei, Giulio Sartori, Eleonora Cannas, Eugenio Gaudio, Chiara Tarantelli, Afua A. Mensah, Filippo Spriano, Antonella Zucchetto, Francesca M. Rossi, Andrea Rinaldi, Manuel Castro de Moura, Anastasios Stathis, Georg Stussi, Valter Gattei, Jennifer R. Brown, Manel Esteller, Emanuele Zucca, Davide Rossi, Francesco Bertoni. ERBB4-mediated signaling is a mediator of resistance to BTK and PI3K inhibitors in B cell lymphoid neoplasms [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 394.

IOA-244 is a Non-ATP-competitive, Highly Selective, Tolerable PI3K Delta Inhibitor That Targets Solid Tumors and Breaks Immune Tolerance

PI3K delta (PI3Kδ) inhibitors are used to treat lymphomas but safety concerns and limited target selectivity curbed their clinical usefulness. PI3Kδ inhibition in solid tumors has recently emerged as a potential novel anticancer therapy through the modulation of T-cell responses and direct antitumor activity. Here we report the exploration of IOA-244/MSC2360844, a first-in-class non-ATP-competitive PI3Kδ inhibitor, for the treatment of solid tumors. We confirm IOA-244's selectivity as tested against a large set of kinases, enzymes, and receptors. IOA-244 inhibits the in vitro growth of lymphoma cells and its activity correlates with the expression levels of PIK3CD, suggesting cancer cell-intrinsic effects of IOA-244. Importantly, IOA-244 inhibits regulatory T cell proliferation while having limited antiproliferative effects on conventional CD4⁺ T cells and no effect on CD8⁺ T cells. Instead, treatment of CD8 T cells with IOA-244 during activation, favors the differentiation of memory-like, long-lived CD8, known to have increased antitumor capacity. These data highlight immune-modulatory properties that can be exploited in solid tumors. In CT26 colorectal and Lewis lung carcinoma lung cancer models, IOA-244 sensitized the tumors to anti-PD-1 (programmed cell death protein 1) treatment, with similar activity in the Pan-02 pancreatic and A20 lymphoma syngeneic mouse models. IOA-244 reshaped the balance of tumor-infiltrating cells, favoring infiltration of CD8 and natural killer cells, while decreasing suppressive immune cells. IOA-244 presented no detectable safety concerns in animal studies and is currently in clinical phase Ib/II investigation in solid and hematologic tumors.

Significance

IOA-244 is a first-in-class non-ATP-competitive, PI3Kδ inhibitor with direct antitumor in vitro activity correlated with PI3Kδ expression. The ability to modulate T cells, in vivo antitumor activity in various models with limited toxicity in animal studies provides the rationale for the ongoing trials in patients with solid tumors and hematologic cancers.

Investigation of morpholine isosters for the development of a potent, selective and metabolically stable mTOR kinase inhibitor

Upregulation of mechanistic target of rapamycin (mTOR) signaling drives various types of cancers and neurological diseases. Rapamycin and its analogues (rapalogs) are first generation mTOR inhibitors, and selectively block mTOR complex 1 (TORC1) by an allosteric mechanism. In contrast, second generation ATP-binding site inhibitors of mTOR kinase (TORKi) target both TORC1 and TORC2. Here, we explore 3,6-dihydro-2H-pyran (DHP) and tetrahydro-2H-pyran (THP) as isosteres of the morpholine moiety to unlock a novel chemical space for TORKi generation. A library of DHP- and THP-substituted triazines was prepared, and molecular modelling provided a rational for a structure activity relationship study. Finally, compound 11b [5-(4-(3-oxa-8-azabicyclo[3.2.1]octan-8-yl)-6-(tetrahydro-2H-pyran-4-yl)-1,3,5-triazin-2-yl)-4-(difluoromethyl)pyridin-2-amine] was selected due its potency and selectivity for mTOR kinase over the structurally related class I phosphoinositide 3-kinases (PI3Ks) isoforms. 11b displayed high metabolic stability towards CYP1A1 degradation, which is of advantage in drug development. After oral administration to male Sprague Dawley rats, 11b reached high concentrations both in plasma and brain, revealing an excellent oral bioavailability. In a metabolic stability assay using human hepatocytes, 11b was more stable than PQR620, the first-in-class brain penetrant TORKi. Compound 11b also displayed dose-dependent anti-proliferative activity in splenic marginal zone lymphoma (SMZL) cell lines as single agent and when combined with BCL2 inhibition (venetoclax). Our results identify the THP-substituted triazine core as a novel scaffold for the development of metabolically stable TORKi for the treatment of chronic diseases and cancers driven by mTOR deregulation and requiring drug distribution also to the central nervous system.

Targeting IRAK4 with Emavusertib in Lymphoma Models with Secondary Resistance to PI3K and BTK Inhibitors

Inhibitors of phosphatidylinositol 3-kinase (PI3K) and Bruton tyrosine kinase (BTK) represent a recognized option for the treatment of patients affected by indolent B cell lymphomas. However, small molecules as single agents show limited success in their ability in inducing complete responses, with only partial remission achieved in most patients, suggesting the need for combination therapies. IRAK4 is a protein kinase downstream of the Toll-like receptor signaling (TLR), a driver pathway of secondary tumor° resistance in both hematological and solid tumor malignancies. Activation of IRAK4 upon TLRs and IL-1 receptor (IL-1R) stimulation and through the adaptor protein MYD88 initiates a signaling cascade that induces cytokine and survival factor expression mediated by the transcription factor NF-κB. MYD88-L265P encoding mutations occur in diffuse large B-cell lymphomas, in lymphoplasmacytic lymphomas and in few marginal zone lymphomas (MZL). The IRAK4 inhibitor emavusertib (CA-4948) has shown early safety and clinical activity in lymphoma and leukemia patients. In this preclinical study, we assessed emavusertib effectiveness in MZL, both as single agent and in combination with targeted agents, with a particular focus on its capability to overcome resistance to BTK and PI3K inhibitors. We showed that the presence of MYD88 L265P mutation in bona fide MZL cell lines confers sensitivity to the IRAK4 inhibitor emavusertib as single agent. Emavusertib-based combinations improved the sensitivity of MZL cells to BTK and PI3K inhibitors, including cells with a secondary resistance to these agents. Emavusertib exerted its activity via inhibition of NF-κB signaling and induction of apoptosis. Considering the early safety data from clinical trials, our study identifies the IRAK4 inhibitor emavusertib as a novel compound to be explored in trials for patients with MYD88-mutated indolent B cell lymphomas as single agent and as combination partner with BTK or PI3K inhibitors in unselected populations of patients.

ERBB4-mediated signaling is a mediator of resistance to BTK and PI3K inhibitors in B cell lymphoid neoplasms

BTK and PI3K inhibitors are among the drugs approved for the treatment of patients with lymphoid neoplasms. Although active, their ability to lead as single agents to long-lasting complete remission is rather limited especially in the lymphoma setting. This indicates that tumor cells often develop resistance to the drugs. Here, we show that the overexpression of ERBB4 and its ligands represents a modality for B cell neoplastic cells to bypass the anti-tumor activity of BTK and PI3K inhibitors and that targeted pharmacological interventions can restore sensitivity to the small molecules. We started from a marginal zone lymphoma (MZL) cell line, Karpas-1718, kept under prolonged exposure to the PI3Kδ inhibitor idelalisib until acquisition of resistance, or with no drug. Cells underwent transcriptome, miRNA and methylation profiling, whole exome sequencing, and pharmacological screening which led to the identification of the overexpression of ERBB4 and its ligands HBEGF and NRG2 in the resistant cells. Cellular and genetic experiments demonstrated the involvement of this axis in blocking the anti-tumor activity of various BTK and PI3K inhibitors, currently used in the clinical setting. Addition of recombinant HBEGF induced resistance to BTK and PI3K inhibitors in parental cells but also in additional lymphoma models. Combination with the ERBB inhibitor lapatinib was beneficial in resistant cells and in other lymphoma models already expressing the identified resistance factors. Multi-omics analysis underlined that an epigenetic reprogramming affected the expression of the resistance-related factors, and pretreatment with demethylating agents or EZH2 inhibitors overcame the resistance. Resistance factors were shown to be expressed in clinical samples, further extending the findings of the study. In conclusions, we identified a novel ERBB4-driven mechanism of resistance to BTK and PI3K inhibitors and treatments that appear to overcome it.

Key points

A mechanism of secondary resistance to the PI3Kδ and BTK inhibitors in B cell neoplasms driven by secreted factors.Resistance can be reverted by targeting ERBB signaling.

Antibody-drug conjugates for lymphoma patients: preclinical and clinical evidences

Antibody-drug conjugates (ADCs) are a recent, revolutionary approach for malignancies treatment, designed to provide superior efficacy and specific targeting of tumor cells, compared to systemic cytotoxic chemotherapy. Their structure combines highly potent anti-cancer drugs (payloads or warheads) and monoclonal antibodies (Abs), specific for a tumor-associated antigen, via a chemical linker. Because the sensitive targeting capabilities of monoclonal Abs allow the direct delivery of cytotoxic payloads to tumor cells, these agents leave healthy cells unharmed, reducing toxicity. Different ADCs have been approved by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of a wide range of malignant conditions, both as monotherapy and in combination with chemotherapy, including for lymphoma patients. Over 100 ADCs are under preclinical and clinical investigation worldwide. This paper it provides an overview of approved and promising ADCs in clinical development for the treatment of lymphoma. Each component of the ADC design, their mechanism of action, and the highlights of their clinical development progress are discussed.

United we stand: Double targeting of CD79B and CD20 in diffuse large B-cell lymphoma

Polatuzumab vedotin is antibody-drug conjugate (ADC) targeting CD79B approved for the treatment of patients with relapsed/refractory diffuse large B-cell lymphoma when given in combination with bendamustine and rituximab. The report by Kawasaki et al. provide hints on what might be happening in lymphoma cells exposed to polatuzumab vedotin and to rituximab and on potential mechanism of resistance to the ADC. Commentary on: Kawasaki et al. The molecular rationale for the combination of polatuzumab vedotin plus rituximab in diffuse large B-cell lymphoma. Br J Haematol 2022;199:245-255.

Pharmacologic screen identifies active combinations with BET inhibitors and LRRK2 as a novel putative target in lymphoma

Inhibitors of the Bromo‐ and Extra‐Terminal domain (BET) family proteins have strong preclinical antitumor activity in multiple tumor models, including lymphomas. Limited single‐agent activity has been reported in the clinical setting. Here, we have performed a pharmacological screening to identify compounds that can increase the antitumor activity of BET inhibitors in lymphomas.

The germinal center B‐cell like diffuse large B‐cell lymphoma (DLBCL) cell lines OCI‐LY‐19 and WSU‐DLCL2 were exposed to 348 compounds given as single agents at two different concentrations and in combination with the BET inhibitor birabresib. The combination partners included small molecules targeting important biologic pathways such as PI3K/AKT/MAPK signaling and apoptosis, approved anticancer agents, kinase inhibitors, epigenetic compounds. The screening identified a series of compounds leading to a stronger antiproliferative activity when given in combination than as single agents: the histone deacetylase (HDAC) inhibitors panobinostat and dacinostat, the mTOR (mechanistic target of rapamycin) inhibitor everolimus, the ABL/SRC (ABL proto‐oncogene/SRC proto oncogene) inhibitor dasatinib, the AKT1/2/3 inhibitor MK‐2206, the JAK2 inhibitor TG101209. The novel finding was the benefit given by the addition of the LRRK2 inhibitor LRRK2‐IN‐1, which was validated in vitro and in vivo. Genetic silencing demonstrated that LRRK2 sustains the proliferation of lymphoma cells, a finding paired with the association between high expression levels and inferior outcome in DLBCL patients.

We identified combinations that can improve the response to BET inhibitors in lymphomas, and LRRK2 as a gene essential for lymphomas and as putative novel target for this type of tumors.

Abstract 1879: A novel implantable device to in vivo assess anti-cancer agents

Background: The high variability in clinical responses observed in cancer patients highlights the need of a tailored therapeutic approach. A possible modality is to assess drugs sensitivity directly in the patients, by introducing small drug delivering devices in tumor sites for a very short period and then looking at the local anti-tumor effect. Here, we present the design of an innovative drug eluting device and its test with the BTK inhibitor ibrutinib as an example of small molecules.

Methods: Mathematical models considered factors related to drug (MW), physical properties, desired concentrations in surrounding tissue, polymers and tissue physical features to identify the optimal polymers and the drug loading for the desired release profile over 24h. In vitro proliferation was measured with the MTT assay, in vivo experiments done in NOD-SCID mice (license TI05/2021), and immunohistochemistry on FFPE xenograft sections stained for Ki67 and cleaved caspase 3 (CASP-3).

Results: Device was designed as an arrow-shaped cylinder, with flat end and flatter sections to be filled with the drug-eluting polymers. Prototypes were built in nylon6,6, a biocompatible but stable polymer. Ibrutinib was incorporated in low MW polyester poly-ε-caprolactone (PCL) as biopolymer by solvent casting. Polymeric coating onto devices was done with a dedicated automatic device.Devices loaded with biopolymer and different concentrations of ibrutinib or “empty” biopolymers were first in vitro tested using diffuse large B cell lymphoma (DLBCL) cell lines. Over 72h, devices with drug inhibited proliferation of the ibrutinib-sensitive TMD8 and OCI-Ly10 cell lines, but not of the ibrutinib-resistant SU-DHL-2 and U2932. No effect was seen with devices with ibrutinib-free biopolymers. Devices, empty or loaded with ibrutinib (5μg), were then inserted in xenografts of ibrutinib-sensitive cell line OCI-Ly10 and ibrutinib resistant U2932. After 24h, mice were sacrificed and xenografts analyzed. By Ki67 and CASP-3 a reduced cell proliferation and an increased apoptosis in the region surrounding the device was observed in the ibrutinib-sensitive xenografts, conversely nor reduced cell proliferation nor apoptosis induction were identified in the ibrutinib-resistant xenografts.

Conclusions: We have created a prototype of a device that can locally release drugs allowing the evaluation of anti-tumor activity, optimizing cures tailored to single patient. The system can be further developed to include multiple drugs, including e.g. antibodies.

Citation Format: Giuseppe Perale, Eugenio Gaudio, Tommaso Casalini, Luca Aresu, Anna Rita De Corso, Filippo Spriano, Chiara Tarantelli, Anastasios Stathis, Andrea Castrovinci, Francesco Bertoni. A novel implantable device to in vivo assess anti-cancer agents [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1879.

Abstract 3279: Dual inhibition of EZH2 and histone deacetylases for the treatment of lymphomas with epigenetic aberrations

Background: Lymphomas are characterized by aberrations in epigenetic proteins that contribute to establishing and maintaining the malignant phenotype. Gain of function mutations in EZH2 histone methyltransferase and inactivating mutations in CREBBP acetyltransferase occur in up to 30% of diffuse large B cell lymphomas (DLBCLs). Half of DLBCLs with mutated EZH2 have also mutated CREBBP. In vitro, mutated EZH2 DLBCLs have a lower sensitivity to HDAC inhibitors, HDACi (Mensah et al, 2021). Here, we explored the dual pharmacological inhibition of EZH2 and HDAC for an improved anti-lymphoma activity.

Methods: Biochemical evaluation and characterization of target engagement were done using fluorescence polarization, thermal shift, surface plasmon resonance, isothermal titration calorimetry and microscale thermophoresis. Computer modelling was performed using available EZH2 and HDACs crystal structures. Anti-proliferative activity was assessed after 7 days (d) using MTT and live imaging in DLBCL cells (n = 5). For cell cycle analysis by flow cytometry, cells were treated, fixed then stained with 7-AAD.

Results: We designed and synthesized 2 dual EZH2/HDAC inhibitors, MC4343 and MC4355, starting from the structures of EZH2 inhibitor tazemetostat (taz) and HDACi vorinostat. In biochemical assays, MC4343 and MC4355 had equal potencies towards EZH2 (0.032 nM) but different specificities towards class I and class II HDACs: MC4355 showed 7.5-fold greater inhibition of HDAC3 compared to MC4343 (0.38 µM and 2.85 µM, respectively) and more potently inhibited HDACs 6 and 8 (0.016, 0.17 µM and no activity, respectively). Computational modelling showed that the coordinative functional group of MC4343, but not of MC4355, caused steric clashes with several HDACs in increasing order: HDAC1 = HDAC3 > HDAC8 >> HDAC4 = HDAC6. These results closely mirrored those obtained from the biochemical analysis. Both compounds inhibited proliferation in DLBCL cell lines irrespective of EZH2 or CREBBP mutational status but EZH2 and/or CREBBP mutants were more sensitive. MC4355 (IC50 range = 0.17 - 1.68 µM; median = 0.2 µM) was more potent than MC4343 (IC50 range = 0.17-2.72 µM; median = 1.78 µM). This was confirmed by live imaging analyses. SUDHL4, with EZH2 Y666N, showed poorer sensitivity to both inhibitors compared to DLBCLs with EZH2 Y646N/S. MC4343 and MC4355 induced cell death and G1 arrest in a dose-dependent manner. Pfeiffer, KARPAS422, WSUDLCL2, most sensitive to taz alone (IC50 = 4, 16, 77 nM), were most sensitive to MC4355 (IC50 = 200, 174, 171 nM). Notably, dual inhibitor treatment of Toledo and SUDHL4 with low sensitivity to taz (IC50 = 9, 14 µM), partially rescued sensitivity (IC50 = 1.7, 1.6 µM).

Conclusions: We designed and synthesized 2 novel dual EZH2/HDAC inhibitors, MC4343 and MC4355, with robust anti-proliferative effects in DLBCL. Our data show the efficacy of this novel class of epigenetic agents in lymphomas.

Citation Format: Afua Adjeiwaa Mensah, Sergio Valente, Milos Matkovic, Giulio Sartori, Chiara Falzarano, Chiara Tarantelli, Luciano Cascione, Stefano A. Pileri, Andrea Cavalli, Antonello Mai, Francesco Bertoni. Dual inhibition of EZH2 and histone deacetylases for the treatment of lymphomas with epigenetic aberrations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3279.

Abstract 1817: EG-011 is a first-in-class Wiskott-Aldrich syndrome protein (WASp) activator with anti-tumor activity

Background. Novel therapeutic targets are needed to improve the outcome of individuals with cancer. EG-011 is a small molecule with in vitro and in vivo anti-tumor activity in lymphoma and acute leukemias, but, at least so far, no activity in solid tumor models (Gaudio et al AACR 2019). Since no information was available on its target, we have now performed experiments showing that EG-011 targets WASp.

Methods. Target identification: kinase screens with DiscoverX KINOMEscan, ProQinase Wildtype-Profiler; thermal proteomic profiling. Target validation: pyrene actin polymerization assay. In vitro drug treatment of cell lines followed for changes in actin filaments (F-actin) by confocal imaging with Alexa Fluor 488 Phalloidin.

Results. Extensive kinome screens excluded kinases as targets of EG-011. We then applied thermal proteomic profiling to identify new protein targets interacting with EG-011. Over 3,300 proteins from the soluble proteome from the EG-011 sensitive mantle cell lymphoma cell line REC1 were analyzed and 48 possible protein targets were initially identified. Among the proteins undergoing a thermal shift, WASp was among the most highly destabilized by EG-011. Due to the pattern of expression of WASp, compatible with the anti-tumor activity observed only in hematological cancers (Gaudio et al AACR 2019), we performed further experiments to confirm the possibility that EG-011 targets WASp. One of the main functions of WASp is the regulation of actin filaments formation. Pyrene actin polymerization assays demonstrated that EG-011 activated the auto-inhibited form of WASP with strong actin polymerization. Further confirmation was obtained using confocal imaging of cell lines exposed to DMSO or EG-011 (500 nM, 5 μM) and stained for F-actin. An increase in actine polymerization was seen in EG-011 sensitive (VL51) and not in resistant (Z138) cell lines at 4, 8 and 24h with both concentrations.

Conclusions. These data demonstrate that EG-011 is the “first-in-class” activator of the auto-inhibited form of WASp with selective anti-tumor activity in lymphomas.

Citation Format: Filippo Spriano, Laura Barnabei, Ana Maria Carrasco Del Amor, Meagan R. Tomasso, Chiara Tarantelli, Eugenia Riveiro, Natalina Pazzi, Shae B. Padrick, Susana Cristobal, Franco Cavalli, Eugenio Gaudio, Francesco Bertoni. EG-011 is a first-in-class Wiskott-Aldrich syndrome protein (WASp) activator with anti-tumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1817.

Resistance to PI3κδ inhibitors in marginal zone lymphoma can be reverted by targeting the IL-6/PDGFRA axis

PI3Kδ inhibitors are active in patients with lymphoid neoplasms and a first series of them have been approved for the treatment of multiple types of B-cell lymphoid tumors, including marginal zone lymphoma (MZL). The identification of the mechanisms underlying either primary or secondary resistance is fundamental to optimize the use of novel drugs. Here we present a model of secondary resistance to PI3Kδ inhibitors obtained by prolonged exposure of a splenic MZL cell line to idelalisib. The VL51 cell line was kept under continuous exposure to idelalisib. The study included detailed characterization of the model, pharmacological screens, silencing experiments, and validation experiments on multiple cell lines and on clinical specimens. VL51 developed resistance to idelalisib, copanlisib, duvelisib, and umbralisib. An integrative analysis of transcriptome and methylation data highlighted an enrichment of upregulated transcripts and low-methylated promoters in resistant cells, including IL-6/STAT3- and PDGFRA-related genes and surface CD19 expression, alongside the repression of the let-7 family of miRNA, and miR-125, miR-130, miR-193 and miR-20. The IL-6R blocking antibody to-cilizumab, the STAT3 inhibitor stattic, the LIN28 inhibitor LIN1632, the PDGFR inhibitor masitinib and the anti-CD19 antibody drug conjugate loncastuximab tesirine were active compounds in the resistant cells as single agents and/or in combination with PI3Kδ inhibition. Findings were validated on additional in vitro lymphoma models and on clinical specimens. A novel model of resistance obtained from splenic MZL allowed the identification of therapeutic approaches able to improve the antitumor activity of PI3Kδ inhibitors in B-cell lymphoid tumors.

The bromodomain and extra-terminal domain degrader MZ1 exhibits preclinical anti-tumoral activity in diffuse large B-cell lymphoma of the activated B cell-like type

Aim

Bromodomain and extra-terminal domain (BET) proteins are epigenetic readers that play a fundamental role in transcription regulation. Preclinical and early clinical evidence sustain BET targeting as an anti-cancer approach. BET degraders are chimeric compounds comprising of a BET inhibitor, which allows the binding to BET bromodomains, linked to a small molecule, binder for an E3 ubiquitin ligase complex, triggering BET proteins degradation via the proteasome. These degraders, called proteolysis-targeting chimeras (PROTACs), can exhibit greater target specificity compared to BET inhibitors and overcome some of their limitations, such as the upregulation of the BET proteins themselves. Here are presented data on the anti-tumor activity and the mechanism of action of the BET degrader MZ1 in diffuse large B cell lymphoma (DLBCL) of the activated B-cell like (ABC, ABC DLBCL), using a BET inhibitor as a comparison.

Methods

Established lymphoma cell lines were exposed for 72 h to increasing doses of the compounds. Cell proliferation was evaluated by using an 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazoliumbromide (MTT) assay. Fluorescent-Activated Cell Sorter (FACS) analysis was performed to measure apoptotic activation and RNA sequencing (RNA-Seq) to study the transcriptional changes induced by the compounds.

Results

MZ1, and not its negative control epimer cisMZ1, was very active with a median half maximal inhibitory concentration (IC50) of 49 nmol/L. MZ1 was more in vitro active than the BET inhibitor birabresib (OTX015). Importantly, MZ1 induced cell death in all the ABC DLBCL cell lines, while the BET inhibitor was cytotoxic only in a fraction of them. BET degrader and inhibitor shared partially similar changes at transcriptome level but the MZ1 effect was stronger and overlapped with that caused cyclin-dependent kinase 9 (CDK9) inhibition.

Conclusions

The BET degrader MZ1 had strong cytotoxic activity in all the ABC DLBCL cell lines that were tested, and, at least in vitro, it elicited more profound effects than BET inhibitors, and encourages further investigations.

PI3Kδ Inhibitors as Immunomodulatory Agents for the Treatment of Lymphoma Patients

Simple Summary

This review focuses on the effects that a class of drugs, PI3Kδ inhibitors, used for the treatment of patients with lymphoma can have not on the neoplastic cells but on the normal cells and how this effect can modulate the immune response and potentially contribute to the anti-tumor response.

Abstract

The development of small molecules able to block specific or multiple isoforms of phosphoinositide 3-kinases (PI3K) has already been an active field of research for many years in the cancer field. PI3Kδ inhibitors are among the targeted agents most extensively studied for the treatment of lymphoma patients and PI3Kδ inhibitors are already approved by regulatory agencies. More recently, it became clear that the anti-tumor activity of PI3K inhibitors might not be due only to a direct effect on the cancer cells but it can also be mediated via inhibition of the kinases in non-neoplastic cells present in the tumor microenvironment. T-cells represent an important component of the tumor microenvironment and they comprise different subpopulations that can have both anti- and pro-tumor effects. In this review article, we discuss the effects that PI3Kδ inhibitors exert on the immune system with a particular focus on the T-cell compartment.

Exon-Intron Differential Analysis Reveals the Role of Competing Endogenous RNAs in Post-Transcriptional Regulation of Translation

Stressful conditions induce the cell to save energy and activate a rescue program modulated by mammalian target of rapamycin (mTOR). Along with transcriptional and translational regulation, the cell relies also on post-transcriptional modulation to quickly adapt the translation of essential proteins. MicroRNAs play an important role in the regulation of protein translation, and their availability is tightly regulated by RNA competing mechanisms often mediated by long noncoding RNAs (lncRNAs). In our paper, we simulated the response to growth adverse condition by bimiralisib, a dual PI3K/mTOR inhibitor, in diffuse large B cell lymphoma cell lines, and we studied post-transcriptional regulation by the differential analysis of exonic and intronic RNA expression. In particular, we observed the upregulation of a lncRNA, lncTNK2-2:1, which correlated with the stabilization of transcripts involved in the regulation of translation and DNA damage after bimiralisib treatment. We identified miR-21-3p as miRNA likely sponged by lncTNK2-2:1, with consequent stabilization of the mRNA of p53, which is a master regulator of cell growth in response to DNA damage.

Targeting CD205 with the antibody drug conjugate MEN1309/OBT076 is an active new therapeutic strategy in lymphoma models

Antibody drug conjugates represent an important class of anti-cancer drugs in both solid tumors and hematological cancers. Here, we report preclinical data on the anti-tumor activity of the first-in-class antibody drug conjugate MEN1309/OBT076 targeting CD205. The study included preclinical in vitro activity screening on a large panel of cell lines, both as single agent and in combination and validation experiments on in vivo models. CD205 was first shown frequently expressed in lymphomas, leukemias and multiple myeloma by immunohistochemistry on tissue microarrays. Anti-tumor activity of MEN1309/OBT076 as single agent was then shown across 42 B-cell lymphoma cell lines with a median IC50 of 200 pM and induction of apoptosis in 25/42 (59.5%) of the cases. The activity appeared highly correlated with its target expression. After in vivo validation as the single agent, the antibody drug conjugate synergized with the BCL2 inhibitor venetoclax, and the anti-CD20 monoclonal antibody rituximab. The first-in-class antibody drug targeting CD205, MEN1309/OBT076, demonstrated strong pre-clinical anti-tumor activity in lymphoma, warranting further investigations as a single agent and in combination.

Abstract PO-46: Mechanisms of resistance to the PI3K inhibitor copanlisib in marginal zone lymphoma

Background: PI3Kδ is expressed in B cells and has a central role in the B-cell receptor signaling. Copanlisib is a highly selective PI3Kδ and PI3Kα inhibitor, and it is currently under clinical development in indolent lymphomas including marginal zone lymphoma (MZL). Copanlisib is Food and Drug Administration (FDA) approved for the treatment of patients with relapsed or refractory follicular lymphoma. Nevertheless, a subset of patients can eventually relapse due to acquired resistance. A better understanding of resistance mechanisms could help to design improved therapies; hence, we generated MZL cell lines resistant to copanlisib.

Materials and Methods: Cells were kept on copanlisib (IC90) until acquisition of resistance (RES) or with no drug (parental, PAR). Stable resistance was confirmed by MTT assay after 3 weeks of drug-free culture. Multidrug resistance phenotype was ruled out by confirming sensitivity to vincristine. Cells underwent transcriptome profiling (RNA-Seq) and immunophenotypic analysis.

Results: The RES models were obtained from VL51 cell line with over 50-fold times higher IC50s than PAR counterparts. Of note, the copanlisib-resistant lines showed decreased sensitivity to other PI3K inhibitors such as duvelisib (50-fold) and idelalisib (5-fold) and to the BTK inhibitor ibrutinib (15-fold), suggesting that the mechanism observed here might drive resistance to other downstream B-cell receptor inhibitors. Gene expression profiles of RES showed the upregulation of cytokine signaling (IL1A, IL1B, CXCR4), NFkB (LTA, TNF), MAPK (RASGRP4, RASGRP2), and JAK-STAT (STAT3, JAK3) signaling pathways and negative regulators of apoptosis (CD44, JUN). Conversely, repressed genes in RES were involved in cell adhesion (ITGA4, ITGB1), antigen presentation (HLAs), and IFN response (PARP12, GBP6). Consistent with the overexpression of antiapoptotic signaling genes, RES cells exhibited also resistance to the BCL2-inhibitor venetoclax, either as a single as in combination with copanlisib. Flow cytometry confirmed the CXCR4 upregulation and the downregulation of CD49d (ITGA4), paired with reduced CD20 and CD81 surface expression. In accordance, addition of a CXCR4 inhibitor overcame resistance to copanlisib.

Conclusions: We created a model of secondary resistance to the PI3K inhibitor copanlisib, derived from an MZL cell line. This model will help in clarifying mechanisms of resistance to the drug and to evaluate alternative therapeutic approaches. Indeed, we already identified novel potential targets, such as IL1 and CXCR4, that might be exploited in overcoming resistance to copanlisib and are worthy of further investigation.

Citation Format: Alberto J. Arribas, Sara Napoli, Luciano Cascione, Eugenio Gaudio, Roberta Bordone-Pittau, Marilia Barreca, Giulio Sartori, Chiara Tarantelli, Filippo Spriano, Andrea Rinaldi, Anastasios Stathis, Georg Stussi, Davide Rossi, Emanuele Zucca, Francesco Bertoni. Mechanisms of resistance to the PI3K inhibitor copanlisib in marginal zone lymphoma [abstract]. In: Proceedings of the AACR Virtual Meeting: Advances in Malignant Lymphoma; 2020 Aug 17-19. Philadelphia (PA): AACR; Blood Cancer Discov 2020;1(3_Suppl):Abstract nr PO-46.

Abstract 4206: EUD-GK-001 is a novel kinase inhibitor with in vitro anti-lymphoma activity

Introduction. EUD-GK compounds, and in particular EUD-GK-91, show selectivity for a restricted number of kinases (ALK, RET, TRK, DDR2, ROS1) and have shown anti-tumor activity in specific solid tumor models (Zuccotto et al, EORTC-NCI-AACR 2016). Here, we have assessed a novel derivative of this class of compounds, EUD-GK-001, in a panel of lymphoma models.

Methods. Lymphoma cell lines, including both B- and T-cells lymphomas, were exposed to a large range of concentrations of EUD-GK-001 as single agent for 72h, followed by MTT proliferation assay and IC50 calculation. Cell cycle were assessed in four cell lines (FARAGE, DOHH2, TMD8, OCI-LY-10) treated with 500 nM of EUD-GK-001 for 72h. Baseline protein expression was assessed by mass spectrometry. Baseline gene expression was obtained by using the Illumina HumanHT 12 Expression BeadChips.

Results. EUD-GK-001 presented a median IC50 of 1.65 μM and 3.75 μM across 14 B- and 4 T- cell lines, respectively. Five out of 14 DLBCL cells lines, including both ABC- and GCB- subtypes, presented IC50 values lower than 1 μM, A dose-depended increase of the cells in the sub-G0 phase (15-55%) was observed in two GCB-DLBCL and two ABC-DLBCL cell lines after EUD-GK-001 exposure for 72h.

Taking advantage of available omics data for the tested cell lines (Cascione at al, AACR 2019), functional annotation of RNA and protein levels showed that TNF/NFKB, inflammation, IL6/JAK/STAT3, IL2/STAT5 signatures were enriched among the transcripts more expressed in the sensitive cell lines, while E2F, DNA repair, MYC signatures were enriched in the resistant cell lines. No genes coding for kinases were more expressed in both GCB (n.=2) and ABC (n=2) sensitive than in resistant DLBCL cell lines (GCB, n=2; ABC, n=3 R). However, three kinases, namely SRC, JAK2 and LCK, were significantly more expressed in EUD-GK-001 GCB-DLBCL sensitive cell lines (DOHH2, FARAGE) than in EUD-GK-001 resistant cells (SU-DHL-8, TOLEDO) and merging the top-50 mRNA and top-50 proteins identified by limma, SRC appeared as a central hub of the top genes associated with sensitivity to EUD-GK-001. The pattern of activity of EUD-GK-001 was however different from what reported for the SRC inhibitor dasatinib in the same lymphoma models (Scuoppo et al, PNAS 2019).

Conclusion. EUD-GK-001 is a novel small molecule with in vitro anti-tumor activity in subsets of lymphoma models, which needs to be further explored.

Citation Format: Lorenzo Scalise, Chiara Tarantelli, Fabio Zuccotto, Filippo Spriano, Michele Mascia, Luciano Cascione, Eugenio Gaudio, Mauro Angiolini, Francesco Bertoni. EUD-GK-001 is a novel kinase inhibitor with in vitro anti-lymphoma activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4206.

Abstract 5215: Inhibition of PIM kinases targets synthetic vulnerabilities and enhances antigen presentation in B cell lymphoma

The PIM kinases are highly expressed in activated B-cell (ABC) diffuse large B-cell lymphoma (DLBCL). Oncogenic cooperation between PIMs and MYC has been demonstrated. Transgenic mice co-expressing Eμ-PIM and Eμ-MYC showed accelerated lymphomagenesis. Conversely, knockdown of PIMs dramatically decreased cMYC levels and lowered tumor incidence. Based on these preclinical data, a treatment strategy aiming at disrupting the oncogenic cooperation between PIMs and MYC may improve the outcome of DLBCL. Therefore, we treated a panel of DLBCL cell lines with increasing dose of the clinically relevant pan-PIM inhibitor (PIMi) AZD1208 (from 0.1 to 10μM) for 48 hours (Hrs), which resulted in a dose-dependent growth inhibition with a stronger efficacy in ABC DLBCL cell lines. The analysis of a CRISPR loss-of-function screening in three ABC (LY3, TMD8, HBL1) and three GCB (SUDHL-4, Pfeiffer, BJAB) DLBCL cell lines (Reddy et al, 2017) showed that PIM2 silencing led to significantly decreased viability irrespective of cell-of-origin, suggesting that this oncogene is essential for cell proliferation in DLBCLs. To identify the genes through which PIMs drive the lymphoma phenotype we performed gene expression profiling using 4 ABC DLBCL cell lines (RIVA, TMD8, SUDHL-2, U2932) treated with either DMSO or AZD1208 at 1μM for 4, 8 and 12 Hrs. We observed induction of 3,439 genes whereas 2,473 genes were downregulated. Gene pathway analysis showed that AZD1208 led to downregulation of genes regulated by MYC, including its known downstream p53 and NFKB target genes. On the other hand, AZD1208 treatment broadly induced MHC class II and antigen presentation genes as well as PI3K/AKT, cell cycle and glutaminase genes. Using a high-throughput screening approach, we found that the inhibitors of cell cycle (such as the BCL2 inhibitor venetoclax/ABT199 and the PLK4 inhibitor CFI-400945) and of glutaminase (CB839) enhanced the antiproliferative effect of AZD1208, whereas combinations with the PI3K/AKT/mTOR inhibitors had negligible synergistic effect. In conclusion, our study revealed previously unknown mechanisms of action of PIM inhibitors and provides a framework for future combination strategies.

Citation Format: Patrizia Mondello, Chiara Tarantelli, Luciano Cascione, Alberto J. Arribas, Andrea Rinaldi, Anas Younes, Francesco Bertoni. Inhibition of PIM kinases targets synthetic vulnerabilities and enhances antigen presentation in B cell lymphoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5215.

Understanding the mechanism of action of pyrrolo[3,2-b]quinoxaline-derivatives as kinase inhibitors

Two novel quinoxaline-based EphA3 tyrosine kinase inhibitors have been designed and characterized in vivo in a relevant lymphoma model, showing high efficacy in the control of tumor size.

The X-ray structure of the catalytic domain of the EphA3 tyrosine kinase in complex with a previously reported type II inhibitor was used to design two novel quinoxaline derivatives, inspired by kinase inhibitors that have reached clinical development. These two new compounds were characterized by an array of cell-based assays and gene expression profiling experiments. A global chemical proteomics approach was used to generate the drug-protein interaction profile, which suggested suitable therapeutic indications. Both inhibitors, studied in the context of angiogenesis and in vivo in a relevant lymphoma model, showed high efficacy in the control of tumor size.

Is There a Role for Dual PI3K/mTOR Inhibitors for Patients Affected with Lymphoma?

The activation of the PI3K/AKT/mTOR pathway is a main driver of cell growth, proliferation, survival, and chemoresistance of cancer cells, and, for this reason, represents an attractive target for developing targeted anti-cancer drugs. There are plenty of preclinical data sustaining the anti-tumor activity of dual PI3K/mTOR inhibitors as single agents and in combination in lymphomas. Clinical responses, including complete remissions (especially in follicular lymphoma patients), are also observed in the very few clinical studies performed in patients that are affected by relapsed/refractory lymphomas or chronic lymphocytic leukemia. In this review, we summarize the literature on dual PI3K/mTOR inhibitors focusing on the lymphoma setting, presenting both the three compounds still in clinical development and those with a clinical program stopped or put on hold.

Biological and clinical implications of BIRC3 mutations in chronic lymphocytic leukemia

BIRC3 is a recurrently mutated gene in chronic lymphocytic leukemia (CLL) but the functional implications of BIRC3 mutations are largely unexplored. Furthermore, little is known about the prognostic impact of BIRC3 mutations in CLL cohorts homogeneously treated with first-line fludarabine, cyclophosphamide, and rituximab (FCR). By immunoblotting analysis, we showed that the non-canonical nuclear factor-κB pathway is active in BIRC3-mutated cell lines and in primary CLL samples, as documented by the stabilization of MAP3K14 and by the nuclear localization of p52. In addition, BIRC3-mutated primary CLL cells are less sensitive to flu-darabine. In order to confirm in patients that BIRC3 mutations confer resistance to fludarabine-based chemoimmunotherapy, a retrospective multicenter cohort of 287 untreated patients receiving first-line FCR was analyzed by targeted next-generation sequencing of 24 recurrently mutated genes in CLL. By univariate analysis adjusted for multiple comparisons BIRC3 mutations identify a poor prognostic subgroup of patients in whom FCR treatment fails (median progression-free survival: 2.2 years, P<0.001) similar to cases harboring TP53 mutations (median progression-free survival: 2.6 years, P<0.0001). BIRC3 mutations maintained an independent association with an increased risk of progression with a hazard ratio of 2.8 (95% confidence interval 1.4-5.6, P=0.004) in multivariate analysis adjusted for TP53 mutation, 17p deletion and IGHV mutation status. If validated, BIRC3 mutations may be used as a new molecular predictor to select high-risk patients for novel frontline therapeutic approaches.

Abstract A127: Secretion of IL16 is associated with resistance to ibrutinib in pre-clinical models of lymphoma

Background.The first-in-class BTK inhibitor ibrutinib has been approved by the U.S. Food and Drug Administration (FDA) for different indications including the treatment of patients with marginal zone lymphoma, who are in need of systemic therapy and have received at least one prior anti-CD20-based therapy. We have generated and characterized a model resistant to ibrutinib and derived from splenic marginal zone lymphoma. Materials and Methods.The splenic MZL VL51 cell line was kept under ibrutinib (IC90) until acquisition of resistance or with no drug (parental, PAR). Cell identity was confirmed by STR DNA fingerprinting. Resistance was determined by MTT assay as stable if present after 2-weeks of drug-free culture. Multi-drug resistance phenotype was ruled out. Cells underwent transcriptome profiling (RNA-Seq), whole exome sequencing, lipidomic profiling, pharmacological screening (348 compounds), and immunophenotypic analysis (FACS). Secreted cytokines and growth factors were analyzed by ELISA. Results. We developed a stable ibrutinib resistance model derived from VL51 cell line (VL51-ibR) with 8-fold times higher IC50 than parental cells. Specific mutations associated with resistance were not detected, including those in BTKor PLCG2 genes. Conditioned media from VL51-ibR conferred resistance to ibrutinib in the parental cells, indicating the involvement of secreted factors in the mechanism of resistance. At transcriptome level, VL51-ibR exhibited overexpression of genes coding for secreted molecules (IL16, CXCL10), integrins (ITGAM, ITGA1), members of the NFKB (TNF, LTA) and RAS-RAF (RASGRP4, RASGRP2) signaling pathways. The pharmacologic screening identified acquired sensitivity to a RAS- inhibitor. Lipidomic profiling showed high levels of specific triacylglycerols, glycerophosphocholines and cardiolipins with a down-regulation of sphingomyelins. Also, in agreement with transcriptomic data, VL51-ibR had increased levels of p-PLCG2 and p-ERK, paired with the presence of IL6 and CXCL10 in the medium and double positive surface expression of CXCR5 and CD49d. We extended our findings to other models and to clinical specimens. Lastly, we investigated whether these results might be extrapolated into different in vitro models and splenic marginal zone lymphoma clinical cases. First, IL16 and CXCL10 expression levels were inversely correlated with sensitivity to ibrutinib in a panel of 13 B-cell lymphoma cell lines (Tarantelli et al, CCR 2018) (P&lt;0.05). Second, we determined the top 200 genes positively correlated genes with IL16 in a series of splenic marginal zone lymphoma clinical cases (Arribas et al, Mod Pathol 2013), and we observed that these genes were also more enriched in the VL51-ibR when compared to the parental VL51. Conclusions. We have developed and characterized a preclinical model, driven by secreted factors, of secondary resistance to the BTK-inhibitor ibrutinib in splenic marginal zone lymphoma. The current work provides new insights into the mechanisms of resistance to ibrutinib and can lead to novel therapeutic approaches to overcome the resistance.

Citation Format: Alberto J. Arribas, Sara Napoli, Eugenio Gaudio, Luciano Cascione, Alessandra Di Veroli, Chiara Tarantelli, Filipppo Spriano, Antonella Zucchetto, Francesca Rossi, Giulio Sartori, Andrea Rinaldi, Anastasios Stathis, Georg Stussi, Valter Gattei, Gabriele Cruciani, Emanuele Zucca, Davide Rossi, Francesco Bertoni. Secretion of IL16 is associated with resistance to ibrutinib in pre-clinical models of lymphoma [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A127. doi:10.1158/1535-7163.TARG-19-A127

Identification of a new family of pyrazolo[3,4-d]pyrimidine derivatives as multitarget Fyn-Blk-Lyn inhibitors active on B- and T-lymphoma cell lines

Abnormal activation of B-cell receptor (BCR) signaling plays a key role in the development of lymphoid malignancies, and could be reverted by the simultaneous inhibition of Lyn, Fyn and Blk, three members of the Src family kinase (SFK). Fyn and Blk are also promising targets for the treatment of some forms of T-cell non-Hodgkin lymphoma which point to the druggability of SFKs for the treatment of these cancers. We recently identified Si308 as a potent Fyn inhibitor, while preliminary data showed that it might also inhibit Lyn and Blk. Here, molecular modelling studies were coupled with enzymatic assays to further investigate the effect of Si308 on Lyn and Blk. A small library of pyrazolo[3,4-d]pyrimidines structurally related to Si308 was synthesized and tested on human lymphoma cell lines. Compound 2h emerged as a new multitarget inhibitor of Lyn, Fyn and Blk endowed with remarkable antiproliferative effects on human B and T lymphoma cell lines. Its favorable ADME properties make the compound suitable for further developments.

Abstract 274: The ATR inhibitor BAY 1895344 shows strong preclinical activity in lymphomas and appears associated with specific gene expression signatures

Introduction. Targeting the DNA repairing pathways represents an intriguing new approach for cancer treatment. BAY 1895344 is a potent, highly selective and orally available ATR inhibitor (Luecking et al, AACR 2017) in its early clinical development in patients with advanced solid tumors and lymphomas (NCT03188965). We performed evaluated its antitumor activity in a large panel of lymphoma cell lines.

Methods. IC50s and caspase 3/7 activation were obtained in cell lines derived from human B (n=50) or T cell (n=9), murine (n=2) and canine (n=1) lymphomas exposed to increasing doses of BAY 1895344 for 72h. Apoptosis activation was defined by at least 1.5-fold increase in caspase 3/7 signal activation vs controls. Transcriptome data (Illumina HumanHT 12 Expression BeadChips, HTG Biomarker Panel) were analyzed with GSEA (statistical significance: absolute NES &gt;1.5, FDR &lt; 0.01). In vivo efficacy was evaluated in xenograft studies of human lymphoma in mice.

Results. BAY 1895344 showed anti-tumor activity with a median IC50 of 60 nM (95%C.I.; 3-500 nM) across the 62 cell lines, comprising mainly germinal center B-cell diffuse large B-cell lymphoma (GCB-DLBCL, n.=17), activated B-cell DLBCL (8), mantle cell lymphoma (MCL, 10), marginal zone lymphoma (6), T cell lymphomas (9). BAY 1895344 was mostly cytotoxic with apoptosis induction in 38/62 (61%) of the cell lines. Sensitivity was not affected by lymphoma histology or DLBCL cell of origin, TP53/BCL2/MYC status or ATM/ATR loss.

A xenograft experiment (MCL Rec-1 cell line) demonstrated complete tumor remission with BAY 1895344 (50 mg/kg, twice daily, 3 days on and 4 days off).

Comparing the gene expression profile of 4 less (IC50&gt;200nM) vs 3 very sensitive (IC50&lt;10nM) GCB-DLBCL cell lines, cell cycle regulation and DNA repair genes were positively associated with higher sensitivity (E2F targets; G2M checkpoint; DNA repair), while survival and inflammation transcripts with lower (TNFA signaling; IL2/STAT5 signaling). Similar results for E2F targets, G2M checkpoint, TNFA signaling and IL2/STAT5 signaling were confirmed in MCL cell lines. Finally, we compared the transcriptome obtained using an NGS-based platform in 30 B cell lymphoma cell lines divided by the median IC50. Genes involved in BRCA1 and/or ATM networks, RB1 and/or TP53 targets, WNT signaling were higher in the most sensitive cell lines, while the opposite was true for genes taking part to apoptosis, cytokine interaction pathway, inflammatory response and TNFA signaling via NFκB, and MAPK signaling.

Conclusion. A strong anti-tumor activity, associated with specific gene expression signatures, was seen with BAY 1895344 in lymphoma models, providing further support for the on-going phase I study.

Citation Format: Eugenio Gaudio, Chiara Tarantelli, Filippo Spriano, Luciano Cascione, Alberto Arribas, Emanuele Zucca, Anastasios Stathis, Antje Margret Wengner, Francesco Bertoni. The ATR inhibitor BAY 1895344 shows strong preclinical activity in lymphomas and appears associated with specific gene expression signatures [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 274.

Abstract 4796: EG-011 is a novel small molecule with in vitro and in vivo anti-tumor activity against lymphoma

Introduction: Despite the improvements, still too many patients die for their lymphomas and novel compounds are needed. We present a new small molecule, EG-011 (PCT/EP2018/057678), with in vitro and in vivo anti-cancer activity in lymphoma models.

Methods: Lymphoma and solid tumor cell lines were exposed to a large range of concentrations of EG-011 as single agent for 72h, followed by MTT proliferation assay and IC50 calculation. Cell viability of twelve acute lymphoblastic leukemia (ALL) primary patient cells from different high-risk subgroups (VNN2+, E2A-HLF, refractory T and IKZF plus) co-culture with marrow-derived MSCs were assayed after 72h of incubation with EG-011 and controls. Apoptosis assay was measured with annexin V by FACS. Xenografts were established s.c. into the left flanks of female NOD-SCID mice; treatment (200 mg/kg, i.p. 5 days per week) started with already established tumors. Combinations were evaluated with Chou-Talalay combination index (CI): synergism (&lt;0.9), additive (0.9-1.1), antagonism/no benefit (&gt; 1.1) after 72 hr treatments.

Results: EG-011 presented a median IC50 of 2.25 μM in 62 lymphoma cell lines (95% C.I. 1-5μM). A higher activity was observed in a group of 21 cell lines that had a median IC50 of 250 nM (95% C.I. 40-600 nM). Among these there were 11 germinal center B cell (GCB) diffuse large B cell lymphomas (DLBCL) (sensitive n=11/21, resistant n=9/41, P &lt; 0.05), 4 mantle cell lymphoma (MCL) (sensitive n=4/21, resistant n=6/41, P n.s.), 3 marginal zone lymphoma (sensitive n=3/21, resistant n=2/41, P n.s.). EG-011 did not show any anti-proliferative activity in a panel of 25 solid tumor cell lines (IC50s &gt; 10 μM), Among 12 primary ALL samples, 7 were sensitive to EG-011 with IC50 values between 0.3-4.6 µM after 72h, 5 displayed IC50 higher than 20 µM.

A dose-dependent increase in cell death (20-55%) was observed in lymphoma cell lines (OCI-LY-19 and REC1) (500 nM and 2 μM; 72h). No cytotoxicity was seen in PBMCs from two healthy donors after treatment at 1 and 10 μM for 24h and 48h.

In an in vivo xenograft experiment with the MCL REC-1 cell line, EG-011 delayed tumor growth (Day 6, Day 7, Day 9, P &lt; 0.05) and tumor weight. EG-011-treated tumors were 2.2-fold smaller than controls (P &lt; 0.001).

Combinations were tested in DLBCL (OCI-LY-1, OCI-LY-8, TMD8) and MCL (REC1, MINO). EG-011 was synergistic with rituximab, bendamustine, venetoclax, ibrutinib and lenalidomide in all tested cell lines.

Conclusion: The selective anti-lymphoma activity, in both in vitro and in vivo models, and the observed in vitro synergisms with FDA approved targeted agents make EG-011 a novel intriguing new drug candidate deserving further preclinical studies.

Citation Format: Eugenio Gaudio, Filippo Spriano, Chiara Tarantelli, Matilde Guala, Eugenia Riveiro, Gaetanina Golino, Antonio Lupia, Giosuè Costa, Roberta Rocca, Luciano Cascione, Silvia Jenni, Yi-Chien Tsai, Beat Bornhauser, Stefano Alcaro, Francesco Paduano, Francesco Trapasso, Emanuele Zucca, Anastasios Stathis, Natalina Pazzi, Franco Cavalli, Francesco Bertoni. EG-011 is a novel small molecule with in vitro and in vivo anti-tumor activity against lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4796.

Abstract 3829: NEO1132 and NEO2734, novel dual bromodomain inhibitors of both BET and CREBBP/EP300, compared to single BET or CREBB/EP300 inhibitors in diffuse large B cell lymphoma

Lymphoma cells have frequent deregulation of their epigenome. The Bromodomain (BRD) and Extra-Terminal domain (BET) proteins are key regulators of the transcription process. The acetyltransferases cyclic AMP response element binding protein (CREB)-binding protein (CBP) and the E1A interacting protein of 300 kDa (EP300) are highly homologous BRD-containing transcriptional co-activators and are often mutated in diffuse large B cell lymphoma (DLBCL). Targeting the individual classes of proteins is a new therapeutic approach, with BET inhibitors having both preclinical and early clinical anti-lymphoma activity. NEO2734 and NEO1132 are novel chemically distinct dual inhibitors of both BET and CREBBP/EP300 proteins with different affinity for their targets. Here, we present initial data exploring their anti-tumor activity in DLBCL models. Lymphoma cell lines were exposed to increasing doses of compounds for 72h followed by MTT assay. Twenty-seven DLBCL cell lines were exposed to NEO2734 and NEO1132. NEO2734 showed anti-tumor activity with a median IC50 of 157 nM (95% C.I., 135-214). While, NEO1132 showed a lower activity compared to NEO2734, with a median IC50 of 400nM (95% C.I., 316-622). For both compounds, cell lines derived from activated B-cell-like (ABC) DLBCL (n.=8) were more sensitive than those derived from germinal center B-cell (GCB) DLBCL (n.=19) (P=0.009, P=0.03 respectively). No differences were observed based on double hit MYC/BCL2 (yes, n.=6; no, n.=14), MYC (translocation: yes, n=8; no, n.=13), BCL2 (translocation: yes, n=12; no, n.=6), TP53 (inactive: yes, n=14; no, n.=6), CREBBP (mutated, n.=10; wild type, n=16), or EP300 (mutated, n.=5; wild type, n.=20) gene status. All the cell lines were also exposed to a BET inhibitor (birabresib, OTX015) (Boi et al, Clinical Cancer Res 2015) and to a CREBBP/EP300 inhibitor (CBP30) (Hammitzsch et al, PNAS 2015). The median IC50 values of the two molecules were 237 nM (95% C.I., 171-344) and 5.5 μM (95% C.I., 4.2-8.3 μM) respectively. The four compounds presented a similar pattern of anti-proliferative activity across all the cell lines (NEO2734 vs NEO1132 R2=0.98, P &lt; 0.001; NEO2734 vs birabresib: R2=0.84, P &lt; 0.001; NEO2734 vs CBP30, R2 = 0.73, P &lt; 0.001; birabresib vs CBP30, R2 = 0.73, P &lt; 0.001) but with different degrees of IC50. NEO2734 was significantly more potent than birabresib (P=0.0182), CBP30 (P&lt;0.001) and NEO1132 (P&lt;0.001). The higher activity of NEO2734 compared to NEO1132 may be attributable to its superior potency in binding CREBBP and EP300, confirming the importance of the BET/CREBBP/EP300 simultaneous inhibition. The novel dual BET and CREBBP/EP300 inhibitors NEO2734 and NEO1132 showed potent in vitro anti-tumor activity across a large panel of DLBCL cell lines and their activity appear to be proportional to the binding affinity for both BET and CREBBP/EP300 proteins.

Citation Format: Filippo Spriano, Eugenio Gaudio, Chiara Tarantelli, Gaetanina Golino, Luciano Cascione, Emanuele Zucca, Anastasios Stathis, Francis Giles, Francesco Bertoni. NEO1132 and NEO2734, novel dual bromodomain inhibitors of both BET and CREBBP/EP300, compared to single BET or CREBB/EP300 inhibitors in diffuse large B cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3829.

The ETS Inhibitors YK-4-279 and TK-216 Are Novel Antilymphoma Agents

PURPOSE

Transcription factors are commonly deregulated in cancer, and they have been widely considered as difficult to target due to their nonenzymatic mechanism of action. Altered expression levels of members of the ETS-transcription factors are often observed in many different tumors, including lymphomas. Here, we characterized two small molecules, YK-4-279 and its clinical derivative, TK-216, targeting ETS factors via blocking the protein-protein interaction with RNA helicases, for their antilymphoma activity.

EXPERIMENTAL DESIGN

The study included preclinical in vitro activity screening on a large panel of cell lines, both as single agent and in combination; validation experiments on in vivo models; and transcriptome and coimmunoprecipitation experiments.

RESULTS

YK-4-279 and TK-216 demonstrated an antitumor activity across several lymphoma cell lines, which we validated in vivo. We observed synergistic activity when YK-4-279 and TK-216 were combined with the BCL2 inhibitor venetoclax and with the immunomodulatory drug lenalidomide. YK-4-279 and TK-216 interfere with protein interactions of ETS family members SPIB, in activated B-cell-like type diffuse large B-cell lymphomas, and SPI1, in germinal center B-cell-type diffuse large B-cell lymphomas.

CONCLUSIONS

The ETS inhibitor YK-4-279 and its clinical derivative TK-216 represent a new class of agents with in vitro and in vivo antitumor activity in lymphomas. Although their detailed mechanism of action needs to be fully defined, in DLBCL they might act by targeting subtype-specific essential transcription factors.

The Novel TORC1/2 Kinase Inhibitor PQR620 Has Anti-Tumor Activity in Lymphomas as a Single Agent and in Combination with Venetoclax

The phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling cascade is an important therapeutic target for lymphomas. Rapamycin-derivates as allosteric mTOR complex 1 (TORC1) inhibitors have shown moderate preclinical and clinical anti-lymphoma activity. Here, we assessed the anti-tumor activity of PQR620, a novel brain penetrant dual TORC1/2 inhibitor, in 56 lymphoma cell lines. We observed anti-tumor activity across 56 lymphoma models with a median IC50 value of 250 nM after 72 h of exposure. PQR620 was largely cytostatic, but the combination with the BCL2 inhibitor venetoclax led to cytotoxicity. Both the single agent and the combination data were validated in xenograft models. The data support further evaluation of PQR620 as a single agent or in combination with venetoclax.