Lymphoma Pre-clinical Models Research Articles

Myeloid-derived suppressor cell mitochondrial fitness governs chemotherapeutic efficacy in hematologic malignancies

Myeloid derived suppressor cells (MDSCs) are key regulators of immune responses and correlate with poor outcomes in hematologic malignancies. Here, we identify that MDSC mitochondrial fitness controls the efficacy of doxorubicin chemotherapy in a preclinical lymphoma model. Mechanistically, we show that triggering STAT3 signaling via β2-adrenergic receptor (β2-AR) activation leads to improved MDSC function through metabolic reprograming, marked by sustained mitochondrial respiration and higher ATP generation which reduces AMPK signaling, altering energy metabolism. Furthermore, induced STAT3 signaling in MDSCs enhances glutamine consumption via the TCA cycle. Metabolized glutamine generates itaconate which downregulates mitochondrial reactive oxygen species via regulation of Nrf2 and the oxidative stress response, enhancing MDSC survival. Using β2-AR blockade, we target the STAT3 pathway and ATP and itaconate metabolism, disrupting ATP generation by the electron transport chain and decreasing itaconate generation causing diminished MDSC mitochondrial fitness. This disruption increases the response to doxorubicin and could be tested clinically.

Abstract 6062: Potent and orally bioavailable BCL6 protein degraders demonstrate efficacy in pre-clinical models of diffuse large B-cell lymphoma (DLBCL)

Abstract The B-cell lymphoma 6 (BCL6) transcription repressor protein is a protooncogene especially in diffuse large B-cell lymphoma (DLBCL), conferring survival, protection, and maintenance of lymphoma cells. BCL6 expression in normal B cells contributes to initiation and maintenance of the germinal centers (GC). Somatic mutations of the BCL6 gene including chromosome translocations have been shown to result in the deregulation of BCL6 expression and contributes to a subgroup of poor prognostic double- and triple-hit lymphomas. To solve this unmet clinical need, we have developed highly specific, potent, and orally bioavailable BCL6 protein degrader HSK43608 that demonstrates potent in vitro and in vivo efficacy in multiple pre-clinical DLBCL models. HSK43608 achieves >90% BCL6 degradation at 10 nM and DC50 of <1 nM in the OCI-Ly1 model following 24 hr treatment. Time-course studies showed >90% BCL6 degradation within 1 hr which could be maintained at 24 hrs. Importantly, medicinal chemistry efforts have resulted in the successful development of new-generation IMIDs to improve the oral bioavailability of BCL6 degrader for in vivo treatment. As expected, concentration of HSK43608 in tumor tissue was much higher than that in plasma in the DLBCL xenograft models. This tumor tissue enrichment of HSK43608 achieved >95% BCL6 degradation 48 hr after last dosing and convincing tumor growth inhibition. It is worth noting that BCL6 knockout mice suffer from myocarditis with eosinophils infiltration in heart muscle. The tissue distribution study demonstrated less HSK43608 in heart than in plasma, partially explained why there was no sign of myocarditis with eosinophils infiltration in the heart of the HSK43608 treated mice. Taking advantage of the new IMIDs structure, HSK43608 barely induce the degradation of the first generation IMIDs targets including GSPT1, SALL4, CK1α, Aiolos and Ikaros, indicating its safety. In summary, these results indicate HSK43608 as a potent and orally bioavailable BCL6 degrader and support further development. Citation Format: Jun Xu, Yangguang Li, Ju Wang, Pingming Tang, Yuting Liao, Chen Zhang, Pangke Yan. Potent and orally bioavailable BCL6 protein degraders demonstrate efficacy in pre-clinical models of diffuse large B-cell lymphoma (DLBCL) [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 6062.

Abstract 160: FGFR1+ cancer associated fibroblasts (CAFs) produce an extracellular matrix (ECM) that curbs infiltration of phagocytic tumor-associated macrophages (TAMs)

Abstract About 40% of diffuse large B-cell lymphoma (DLBCL) pts do not respond to immunochemotherapy. In human and murine models, we and others have shown that the lymphoma microenvironment (LME) changes with disease progression and treatment resistance. This lymphoma cell-LME co-evolutionary process results in expansion of treatment-resistant lymphoma cells as well as reduced infiltration of T cells and reprogramming of CAFs and TAMs into immune suppressive entities. Our analysis of relapse or refractory (RR)-DLBCLs showed not only an immune depleted LME but also an enrichment of CAFs harboring activation of fibroblast growth factor receptor (FGFR1+). Since FGFR1 inhibitors (FGFR1i) are clinically available, we sought to determine its anti-neoplastic effect on DLBCL. We first confirmed that lymphoma cells, including murine and human, and primary and RR-DLBCLs, did not express FGFR1. Accordingly, no anti-tumoral effect was detected when the selective FGFR1i SSR128129E was administered in vitro to a lymphoma cell panel. However, oral administration of FGFR1i to pre-clinical lymphoma models including two RR-DLBCL patient-derived xenografts (PDX) and four syngeneic murine models representing distinct DLBCL genetic subtypes produced a significant anti-lymphoma effect in all cases. In addition to decreased lymphoma cells, we observed increase in the ECM and TAM infiltration, even in the murine models, suggesting that FGFR1i reprogrammed the CAFs. We thus conducted matrisome analysis (i.e., ECM proteomics) in a murine model (p53 mutant) and found a significant up-regulation of proteoglycans and the immune active glycoproteins decorin, lumican and byglican (q-value <0.05 vs. vehicle). To determine whether these ECM changes affect lymphoma cells, we performed 3D co-cultures of lymphoma cells embedded into de-celularized ECM obtained from FGFR1i vs. vehicle mice. We found that FGFR1i-ECM (vs. vehicle-ECM) modifies the secretome of lymphoma cells by upregulating several cytokines including IL6, IL16 and TNF-alpha. To further characterize the functional state of CAFs and TAMs, we conducted single cell RNA-seq in the two RR-DLBCL PDXs treated as before. We found that FGFR1-CAFs in the LME of FGFR1i tumors (vs. vehicle) were reprogrammed into inflammatory-like CAFs characterized by the expression of several monocyte/macrophage chemotactic factors including CCL2, CCL7, CXCL3, and CXCL12. Consequent with these findings we not only observed an increase infiltration of TAMs in the LME of FGFR1i tumors but also that they were reprogrammed in phagocytic phenotypes. In sum, our results suggest that CAF-FGFR1+ produce an immune “silent” ECM that characterizes RR-DLBCL while FGFR1i reverses this ECM phenotype ultimately resulting in the infiltration of antitumoral TAMs, delineating a novel ECM-directed therapeutic approach for this disease. Citation Format: Nicolás Di Siervi, Maria Victoria Revuelta, Nahuel Zamponi, Giorgio Inghirami, Leandro Cerchietti. FGFR1+ cancer associated fibroblasts (CAFs) produce an extracellular matrix (ECM) that curbs infiltration of phagocytic tumor-associated macrophages (TAMs) [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 160.

Tunable PhenoCycler imaging of the murine pre-clinical tumour microenvironments

BackgroundThe tumour microenvironment (TME) consists of tumour-supportive immune cells, endothelial cells, and fibroblasts. PhenoCycler, a high-plex single cell spatial biology imaging platform, is used to characterize the complexity of the TME. Researchers worldwide harvest and bank tissues from mouse models which are employed to model a plethora of human disease. With the explosion of interest in spatial biology, these panoplies of archival tissues provide a valuable resource to answer new questions. Here, we describe our protocols for developing tunable PhenoCycler multiplexed imaging panels and describe our open-source data analysis pipeline. Using these protocols, we used PhenoCycler to spatially resolve the TME of 8 routinely employed pre-clinical models of lymphoma, breast cancer, and melanoma preserved as FFPE.ResultsOur data reveal distinct TMEs in the different cancer models that were imaged and show that cell-cell contacts differ depending on the tumour type examined. For instance, we found that the immune infiltration in a murine model of melanoma is altered in cellular organization in melanomas that become resistant to αPD-1 therapy, with depletions in a number of cell-cell interactions.ConclusionsThis work presents a valuable resource study seamlessly adaptable to any field of research involving murine models. The methodology described allows researchers to address newly formed hypotheses using archival materials, bypassing the new to perform new mouse studies.

Inhibition of EZH2 Improves CART19 Immunotherapy By Reprogramming Lymphoma Tumor Cells and Enhancing T-Cell Functionality

Introduction: Anti-CD19 chimeric antigen receptor T cell (CART19) immunotherapy provides a high response rate in diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) patients, but only ~30-40% of patients maintain a durable remission. The factors contributing to lymphoma resistance to CART19 are numerous, multifaceted, and coincidental, such as tumor intrinsic properties, CART dysfunction, the immunosuppressive tumor microenvironment (TME), and host factors. However, most strategies currently in development to increase CART efficacy only address one resistance mechanism at a time; therefore, it is unlikely that these approaches will be consistently effective in a group of heterogeneous patients. In this study, we sought to develop a strategy to overcome multiple resistance mechanisms simultaneously. Epigenetic modulation offers a promising approach to this goal, as it can reshape the tumor landscape, as well as immune cells. DLBCL/FL cells depend for their survival on the methyltransferase EZH2, which represses gene expression by generating histone 3 lysine 27 trimethylation. Interestingly, somatic gain-of-function mutations of EZH2 are frequently found in DLBCL/FL and drive lymphomagenesis and impair tumor B-cell to T-cell interactions, leading to an immune evasive phenotype. Therefore, we hypothesized that EZH2 inhibition could enhance CART anti-tumor effect, remodeling the entire tumor ecosystem by: a. inhibiting lymphoma growth; b. increasing lymphoma immunogenicity; and c. enhancing T cell function ( Fig. 1A). Methods and Results: Through short-term killing assays, we compared CART19 alone to CART19 combined with the EZH2 inhibitor tazemetostat (taz), and demonstrated that taz enhances CART19 tumor killing of DLBCL cell lines [OCI-Ly18 and Toledo (with wild-type EZH2) and SU-DHL-4 (with mutant EZH2)]. Interestingly, the highest effect was observed when tumor cells were pre-incubated with taz and taz was kept in the coculture with CART19. This finding underscores the importance of tumor priming to improve CART19 recognition and activation. Since EZH2 is also expressed by T cells, we tested if EZH2 inhibition impacted CART cell function. Co-treatment of lymphoma cell lines with taz and CART19 was associated with higher cytokine secretion over time (INFy and TNF) by CART cells and CART cell expansion. Most importantly, using the sub-cutaneous OCI-Ly18 xenograft lymphoma model in immunodeficient NSG mice, we demonstrated that taz administration improved tumor control ( Fig. 1B) and CART19 expansion and infiltration in vivo. Mechanistically, we studied the molecular changes in lymphoma cells (OCI-Ly18 and SU-DHL-4) induced by exposure to taz/CART19 or CART19 alone by performing RNA sequencing. We observed upregulation of genes involved in inflammatory response, B-cell activation/differentiation (e.g., BATCH2), adhesion (OX40L, CD80), and motility (CAECAM1, NRCAM1, EPHB2, CXCL16, CXCL10), sustaining the hypothesis that EZH2 inhibition changed lymphoma immunogenicity and the tumor:CART cell interaction. Indeed, functionally, we observed that taz exposure increased tumor:CART cell interaction in vitro as demonstrated by increased avidity (zMovi assay). Further, single-cell RNA sequencing performed on circulating CART19 cells from taz-treated-mice revealed enrichment in naïve and less exhausted CART cells. Lastly, we assessed whether increased activation of EZH2 in tumor cells reduces responses to CART19 in the clinic. We retrospectively analyzed a cohort of large B-cell lymphoma patients treated with commercial CART19 (tisagenlecleucel and axicabtagene ciloleucel) at the University of Pennsylvania between January 2018 and March 2023 for response (Lugano criteria) according to their EZH2 mutational status. Patients harboring EZH2 activating mutations (14/69) had a reduced complete response rate to CART19 as compared to wild-type patients (15.4% vs. 40.0%). Conclusions: Our data demonstrate that modulation of EZH2 enhances CART19 immunotherapy in preclinical models of lymphoma. EZH2 inhibition rewires lymphoma immunogenicity, making tumor cells more susceptible to CART19 killing and reducing CART19 terminal differentiation. By understanding and modulating the interplay between tumor and CART cells, we can unlock the full potential of CART19 immunotherapy in DLBCL/FL patients, aiming at long-lasting treatment outcomes.

Tafasitamab in Combination with a CD20xCD3 Bispecific T-Cell Engager Significantly Prolongs Survival in Preclinical Lymphoma Models

R-CHOP remains the standard of care for newly diagnosed DLBCL patients. However, 30-40% of patients are refractory or relapse after initial response to the immunochemotherapy, indicating a high-unmet medical need for these patients. Tafasitamab is a CD19-targeting, Fc-modified humanized monoclonal antibody mediating antibody-dependent cellular cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP) and direct cytotoxicity. Tafasitamab was granted accelerated approval by the FDA in 2020 and conditional marketing authorization by the EMA in 2021 for the treatment of transplant-ineligible adult patients with relapsed or refractory (R/R) DLBCL in combination with the immunomodulatory drug lenalidomide. CD20xCD3 T-cell engagers are currently under clinical investigation or recently received FDA approval in 2L+ DLBCL (Thieblemont 2023; Dickinson 2022). CD19- and CD20-targeting antibodies might complement each other, as I) CD19 could compensate for CD20-low/ -negative settings and vice versa and II) monoclonal antibodies and T-cell engagers combine powerful and distinct immune pathways holding great potential to increase responses in patients who may need additional therapeutic options. The aim of this study was to investigate the combination of tafasitamab and MOR212, a proprietary proof-of-concept CD20xCD3 T-cell engaging antibody, in preclinical models of lymphoma. First, MOR212 was characterized in vitro and in vivo to ensure comparability with other CD20xCD3 bispecific antibodies (comp1-3) currently under clinical investigation. In in vitro cytotoxicity assays, MOR212 demonstrated similar (comp1-2), or improved (comp3) cytotoxicity (MOR212 vs comp1 and 2 p>0.05 vs comp3 p=0.03; exemplary data for EC50 in SU-DHL-4 cells; n=6), cytokine secretion (MOR212 vs comp1-3 p>0.05; exemplary data for EC50 TNFα; n=4) and T-cell activation (MOR212 vs comp1 p=0.05; vs comp2 p>0.05 vs comp3 p=0.003; exemplary data for % CD69 on CD8 T-cells; n=6) in cell lines expressing different levels of CD20. In a lymphoma in vivo model co-engrafted with human T-cells, MOR212 prolonged progression-free survival of mice to a similar extent as two comparator molecules that were tested head-to-head (MOR212 vs comp1 and 3 p>0.05;) at a dose of 0.1 mg/kg. Next, we investigated the combination of tafasitamab and MOR212 in vitro. Due to the differential killing kinetics of a monoclonal antibody and a T-cell engager, we made use of a real time live-cell imaging assay. Lymphoma cells were co-cultured with healthy donor peripheral blood mononuclear cells (PBMCs) and tafasitamab and MOR212 were added in different concentration combinations. Tumor cell killing was monitored every 3 hours for 72 hours and revealed improved target cell killing by the combination of both compounds (signal/background caspase 3/7 staining at 48h: MOR212 24.2 vs tafasitamab 28.2 vs MOR212+tafasitamab 111.5; n=1). To confirm these findings in vivo, we used human CD34+ engrafted NCG mice with a huIL15 boost allowing for the development of human T-cells as well as NK-cells, as essential effector cells for the combination of both compounds. Raji lymphoma cells were engrafted and treatment with the single or combination therapy was started once tumors reached a pulpable size. Combination of tafasitamab and MOR212 significantly improved progression-free survival in animals compared to monotherapy treatment (tafasitamab+MOR212 vs tafasitamab only p=0.0002 and MOR212 only p=0.0098). In addition, the combined treatment regimen appeared to be safe in mice as no side effects on both body weight loss and clinical score were recorded throughout the entire observation period. Our findings prove that the combination of tafasitamab and a CD20xCD3 T-cell engaging antibody significantly increases tumor cell eradication both in vitro and in vivo and lay the ground to potentially translate the results into improved outcome for patients with aggressive lymphoma in future clinical trials.

Safety, Efficacy and T-Cell Predictive Biomarkers in a Phase I Trial of Copanlisib+Nivolumab in Patients with Richter's Transformation (RT) or Transformed Non-Hodgkin Lymphoma (tNHL)

Background. Despite advances in targeted and cellular therapy, outcomes among patients (pts) with RT and tNHL remain dismal. Copanlisib (COPA) is a selective, small molecule, PI3Kinhibitor which preferentially targets the p110αδ isoforms . COPA has shown clinical efficacy in NHL and is an approved therapy for follicular lymphoma (FL). Nivolumab (NIVO) is a PD-1 antagonist which has demonstrated activity in NHL. Furthermore, combined targeting of PI3K and PD-1 has demonstrated synergy in pre-clinical lymphoma models. Here we report results of a phase 1 study of COPA in combination with NIVO in pts with R/R RT or tNHL (NCT03884998) and correlate response to treatment and T cell functionality in RT. Methods. This ongoing multicenter, open-label, phase I, investigator-sponsored study is enrolling pts with RT or tNHL, age ≥18 years, whose disease has relapsed or was refractory to ≥1 prior line of therapy. The phase I portion of the study follows a standard 3+3 design, followed by a dose expansion of 16 evaluable pts, with two planned dose levels of COPA administered IV (dose level [DL]1 - 45 mg on days 1, 8 and 15 and DL2 - 60 mg on days 1, 8 and 15 of a 28-day cycle). NIVO 240 mg is given IV on days 1 and 15. Pts receive up to 24 cycles of therapy. Dose limiting toxicities (DLT) were defined as grade ≥4 hematologic lasting > 7 days or grade ≥3 non-hematologic toxicities. The primary study objective is to evaluate the maximum tolerated dose (MTD) of the combination; secondary objectives are preliminary efficacy by Lugano criteria. Exploratory objectives include T-cell functionality assessed by flow cytometry analysis of cell subsets as well as scRNA-Seq performed on biospecimens banked from pts pre-treatment, after cycles 1 and 5, and at the end of treatment. Results. The study enrolled 25 pts to date, 11 in dose finding (8 at DL1 and 3 at DL2) and 14 in dose expansion cohorts. Fourteen pts had RT and 11 had tNHL (10 tFL and 1 transformed lymphoplasmacytic lymphoma). Median (med) age was 65 years (32-77), 88% (22/25) had ECOG performance status 0-1. Pts had received a med of 4 prior lines of therapy (range, 1-10); 8 pts (2 RT, 6 tNHL) had CAR T cells. During dose finding, 8 pts were treated at DL1 (45 mg COPA), of which 2 pts did not complete the DLT period due to rapidly progressive disease and were replaced. No DLTs were observed in 6 evaluable pts at DL1. At DL2 (60 mg COPA), three DLTs (neutropenia, thrombocytopenia) occurred in 2 pts determining the MTD of COPA to be 45 mg. After a median follow-up of 14 months (range 1.8-20.6), the most common treatment-related adverse events (AEs, any grade) were diarrhea and anemia (Table 1). Twenty-three pts went off protocol after a med of 3 cycles (range 1-20); 2 remain on treatment. Sixteen pts discontinued therapy due to progressive disease and 6 due to AEs. Among the 23 efficacy-evaluable pts who completed at least one cycle of therapy, 10 pts achieved a response (ORR 43%). Pts with tFL had an ORR of 60% (2 CR and 4 PR) with median progression free survival (mPFS) 4.8 months (95%CI: 0.4-16.8) and median duration of response (mDOR) 10.2 months (95%CI: 2.0-13.6) (Figure 1). Pts with RT had an ORR of 33% (2 CR and 2 PR) with mPFS 2.0 months (95%CI: 0.7-4.9) and mDOR not reached (95%CI: 3.0-NA). Analysis of paired samples from pts using flow cytometry and scRNA-Seq demonstrated an increase in circulating CD8+ T cell population and a decrease in exhaustion markers (PD1, CTLA-4) after exposure to COPA/NIVO. Analysis of 2 responding RT pts by scRNA-Seq demonstrated downregulation of MYC in tumor cells and upregulation of IFN response in T cells. This pattern was not observed 3 RT non-responders (NRs). By contrast, CD8+ effector T-cells from NRs exhibited downmodulation of the IFN response after cycle 1 of treatment and concurrent activation of p53-regulated genes and apoptotic genes. Tregs sourced from RT responders showed enhanced expression of apoptosis pathways after treatment, while these pathways were downregulated in NR Tregs. Discussion. We identified COPA 45 mg IV on days 1, 8 and 15 as the MTD/RP2D in combination with NIVO in pts with R/R RT and tFL. This combination was generally well-tolerated and had activity, particularly in pts with with tFL. We observed key differences in gene expression patterns in T cell subsets between the responders and NRs. Downregulation of MYC in the tumor, activation of the apoptotic program in Tregs and enhanced CD8 T-cell IFN response were associated with treatment response in RT. Accrual is ongoing.

Novel Drug to Target HK2 Overcomes Therapeutic Resistance in Preclinical B-Cell Lymphoma Models

Background: The Warburg's effect is a hallmark in cancer. Hexokinase II (HK2) is a glycolic kinase to phosphorylate glucose to glucose-6-phosphate, which can be utilized as the energy source for cells. HK2 is predominantly overexpressed in cancer cells and has been associated with poor clinical outcomes in cancer patients. Previously, we demonstrated that HK2 mRNA and protein levels were increased in diffuse large B-cell lymphoma patients, and were significantly associated with inferior progression free survival (PFS) and overall survival (OS). In our rituximab and chemotherapy-resistant cell lines (TRCL), we demonstrated an upregulation of HK2 expression level is association with voltage-dependent anion channel (VDAC) resulting in a) repress mitochondrial potential and b) global therapy resistance. Knocking out HK2 overcame the chemo-resistance phenotype observed in TRCL. Here, we designed a novel specific inhibitor of HK2 and tested its activity in lymphoma pre-clinical models. Material and Methods: A HK2 specific inhibitor (HK2-001) was designed and generated according to antisense peptide technology, CABS-docking system and ROSWTTA analyzing. A panel of B-cell lymphoma cell lines including rituximab/chemo-sensitive and resistant cell lines (Raji, Raji 4RH, RL and RL 4RH), diffuse large B-cell lymphoma (DLBCL) (DHL4, DOHH2, TMD8 and U2932) and mantle cell lymphoma (MCL) (HBL2, Granta, Mino and Z138) were used. In addition, primary tumor cells isolated from chronic lymphocytic lymphoma (CLL) or other B-cell lymphoma patients were used. Briefly, cell lines or primary tumor cells were exposed to escalating doses of HK2-001 alone or in combination with different chemotherapy agents (doxorubicin, dexamethasone), targeted agents (i.e. burton tyrosine kinase inhibitors, BH3 mimetics) or monoclonal anti-CD20 antibodies. Cell viability was evaluated using the Presto Blue assay in experiments testing pharmacological interactions between HK2-001 and chemotherapy or targeted agents. All experiments were performed in triplicates in three separate experiments. The coefficient of synergy was calculated using CalcuSyn. Results: In vitro exposure of lymphoma cell lines to HK2-001 induced cell death in a panel of B-cell lymphoma cell lines representing rituximab/chemo-sensitive and resistant lymphoma. In addition, synergistic activity was observed between HK2-001 and doxorubicin, ibrutinib, and Venetoclax. These effects were also observed in primary tumor cells isolated from B-cell lymphoma patients. In addition, HK2-001 potentiated the anti-tumor activity of Rituximab and Obinutuzumab ex vivo. Conclusion: We developed a novel peptide targeting HK2. Pre-clinical studies suggested anti-tumor activity as a single agent. More importantly, HK2-001 enhanced the anti-tumor activity of chemotherapy agents, BTK inhibitors, BH3 mimetics and monoclonal antibodies targeting CD20. HK2-001 is a promising novel therapeutic strategy for against B-cell lymphoma, especially in refractory or relapsed patients. Future studies aimed to evaluate the effects of HKII-001 drug combinations in lymphoma animal models are planned and to evaluate its effects on Chimeric antigen receptor T-cells (CART) or bi-specific antibodies.

An Idiotype Vaccine Strategy Utilizing Targeted NGS and Cell Free Protein Synthesis System Ensures Identification and Production of Human Idiotype Antigens, and Shows Promising Results in Preclinical Models of B-Cell Lymphoma with a Novel TLR7/8 Agonist-Based Adjuvant and Anti-PD-L1 Antibody

Background: Non-Hodgkin lymphoma (NHL) is one of the most common hematological malignancies in the world. Despite advances in treatment options, such as chimeric antigen receptor T cells (CAR-T) or bispecific antibodies, many patients still recur after complete remissions (CR) or do not achieve CR. Since B cell malignancies arise from clonal expansion, the B cell receptor (BCR) expressed on the cell surface, idiotype, has been studied as a tumor-specific antigen. Several trials have evaluated idiotype vaccines in clinical setting, but failed to demonstrate efficacy. Limitations have arisen from the uncertainty of BCR sequence confirmation, long turnaround time in manufacturing idiotype antigen, and the absence of strong immune modulators. Here, we utilized targeted next generation sequencing (NGS) for BCR, cell-free protein synthesis (CFPS) system for idiotype antigen manufacturing, and a novel liposomal TLR7/8 agonist-based adjuvant to optimize idiotype vaccine. Methods: To generate the idiotype antigens as single-chain variable fragment (scFv) from A20 lymphoma cell line and biopsy samples from NHL patients, variable regions of BCR heavy and light chain were sequenced by targeted NGS. Total RNA was isolated from A20 cells and tumor tissues from patients, and reverse transcription-polymerase chain reaction (RT-PCR) was performed using constant region-specific primers, resulting in the 1 st strand cDNA. Subsequently, the 2 nd strand cDNA was synthesized using V-gene specific primers and sequenced using an Illumina MiSeq sequencer. We applied targeted NGS to patients' tumor tissues from Asan Medical Center and Seoul National University Hospital to understand whether this method works in human tissues as well. The identified sequence was cloned into a linear DNA template and expressed by CFPS system. We optimized the CFPS system and purification process of idiotype antigen scFv from A20 cell line and human tissues. The liposomal adjuvant ProLNG-001 (TLR7/8 agonist 140 μg) and ProLNG-002 (TLR7/8 agonist 70 μg + TLR4 agonist 5 ug) were synthesized by microfluidics method. Idiotype antigen A20-scFv 50 μg was given alone or mixed with ProLNG-001 or -002. To investigate the efficacy of the idiotype vaccine, BALB/c mice were subcutaneously injected with 5×10 5 of A20 cells. Mice were subcutaneously vaccinated 4 times at 1-week intervals starting from day 2 after tumor inoculation. Atezolizumab 10 mg/kg was administered intraperitoneally 3 times a week for 3 weeks in the idiotype vaccine + immune checkpoint inhibitor combination group (Figure 1a). Results: Targeted NGS has confirmed BCR sequences from A20 cell line and dominant malignant B cell clone from patients' tumor with a success rate of over 90% when sufficient volume (more than 500 mm 3) of biopsy sample was provided for RNA extraction. Also, we were able to express the idiotype scFv antigens determined from 18 NHL patients' tumor samples using CFPS system with a 100% success rate (Figure 1b). The untreated mice (Group 1) showed a tumor growth pattern similar to that of Group 2 (vaccination with antigen only). Vaccination with idiotype antigen mixed with liposomal adjuvants, ProLNG-001 (Group 3) and ProLNG-002 (Group 4), significantly inhibited tumor growth. The combination of anti-PD-L1 antibody and idiotype antigen mixed with ProLNG-002 (Group 5) generated even better overall anti-tumor responses with 14 out of 15 mice showing no residual tumor at day 34 after tumor inoculation. Conclusion: Taken together, the idiotype vaccine strategy using targeted NGS for BCR, CFPS system for idiotype antigen manufacturing, and TLR7/8-agonist-based liposomal adjuvants showed highly effective results in the preclinical syngeneic A20 tumor model. Furthermore, the usage of immune checkpoint inhibitors combined with idiotype vaccine in B cell lymphoma may exert synergistic effects. The CFPS system can be applied to swift, robust and personalized manufacturing of idiotype antigen for individuals with different idiotype sequence in a GMP setting, which was not possible in prior studies. These results support further development of the idiotypic vaccine as a treatment option for non-Hodgkin's B cell lymphomas.

A First-in-Human Phase 1 Study of ABBV-525, a Small-Molecule MALT1 Inhibitor, in Patients with Relapsed or Refractory B-Cell Non-Hodgkin Lymphoma

Background and Significance Many B-cell malignancies are characterized by chronic activation of the B-cell receptor (BCR) and nuclear factor kappa B (NF-κB) signaling pathways. In many non-Hodgkin lymphoma (NHL) subtypes, constitutive NF-κB activation results from genetic mutations and/or auto-antigen stimulation of the BCR pathway. While agents targeting the BCR pathway are effective treatments for many B-cell malignancies, patients (pts) often have progressive disease due to acquired resistance to BCR-targeted agents. Thus, there is an unmet medical need for novel therapeutic targets and treatment approaches. The mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is an enzymatic and scaffolding node in the BCR pathway and a key mediator of the BCR/NF-κB signal transduction pathway. Its action is downstream, or in some instances parallel to, resistance mechanisms to existing NHL therapies, including BTK C481S and PLCG2 mutations, which are known acquired mechanisms of resistance to covalent Bruton's tyrosine kinase (BTK) inhibitors in pts with chronic lymphocytic leukemia (CLL). MALT1 inhibition represents a novel therapeutic approach for malignancies with chronic activation of NF-κB, including those pts with acquired resistance to upstream targets. ABBV-MALT1 is a small-molecule, tool compound, MALT1 inhibitor. Preclinical studies of ABBV-MALT1 have demonstrated potent activity against MALT1-relevant biomarkers, including inhibition of BCR pathway signal transduction and reduced NF-κB gene activation in non-germinal center B-cell diffuse large B-cell lymphoma (non-GCB DLBCL) cell lines. ABBV-MALT1 has also shown activity in a range of preclinical lymphoma models as both monotherapy and in combination with venetoclax, including robust antitumor activity in malignant B-cell models that are resistant to BTK inhibitors. This phase 1 study evaluates the clinical candidate MALT1 inhibitor ABBV-525 as monotherapy in pts with relapsed or refractory (R/R) B-cell NHL. Study Design and Methods This is a first-in-human, phase 1, open-label, multicenter study of single-agent ABBV-525 in pts with R/R B-cell NHL (NCT05618028). Eligibility criteria are listed in Table 1. The primary objectives are to evaluate safety, tolerability, and pharmacokinetics (PK) of ABBV-525 and to determine the recommended phase 2 dose (RP2D). The secondary objective is to assess the preliminary efficacy of ABBV-525 in subsets of pts with R/R B-cell NHL. Exploratory objectives include evaluating biomarkers predictive of response and pharmacodynamic biomarkers, including the effects of ABBV-525 on BCR pathway signal transduction and NF-κB gene activation. This is a 3-part study (Figure 1): dose escalation (part 1), dose optimization (part 2), and dose expansion (part 3). Part 1 aims to establish the maximum administered dose/maximum tolerated dose of ABBV-525 and is primarily guided by a Bayesian optimal interval design. Part 2 aims to identify the RP2D of ABBV-525. Part 3 will further characterize the safety profile of ABBV-525 at the RP2D. Approximately 150 pts are planned for enrollment, including those with various R/R mature B-cell lymphomas in part 1, pts with documented diagnosis of R/R CLL in part 2, and pts with documented diagnosis of non-GCB DLBCL in part 3. ABBV-525 is orally administered until disease progression, intolerable toxicity, or other study discontinuation criteria are met. Safety assessments include dose-limiting toxicities, adverse events (per National Cancer Institute Common Terminology Criteria for Adverse Events v5.0), clinical laboratory parameters, vital signs, and electrocardiogram variables. PK parameters, including maximum observed plasma concentration (C max), time to C max, and area under the concentration-time curve will be analyzed using noncompartmental methods. Efficacy will be assessed through response per disease-specific criteria (including International Workshop on Chronic Lymphocytic Leukemia, International Workshop on Waldenstrom's Macroglobulinemia, and Lugano classification). Duration of response will be evaluated by Kaplan-Meier estimates. Biomarker data will be analyzed as change from baseline and summarized for each scheduled postbaseline visit. Pts are being enrolled in 25 sites across the USA, Australia, Belgium, France, Germany, Israel, Spain, and UK. As of August 1, 2023, 2 pts had been treated.

Mitochondrial Reprogramming By Bcl-2 Inhibitor Venetoclax Enhances αCD19 CAR-T Cell Fitness and Anti-Tumor Efficacy

Introduction Patients undergoing anti-CD19 chimeric antigen receptor T cell (CAR T) therapy for the treatment of aggressive B-cell non-Hodgkin lymphomas (B-NHL) can expect a complete response rate of merely 43-68%. Insubstantial clinical responses to CAR T therapy and a small window of survival for patients facing relapsed/refractory (R/R) disease highlights the critical need for improvement of CAR T therapy in aggressive B-NHL cases. Recent findings suggest that enriching for a CD8 + T Stem Cell Memory (T SCM) population within adoptive cell therapies translates to enhanced antitumor function and persistence in vivo, and thus produces favorable clinical outcomes. T SCM cells display heightened self-renewal, low mitochondrial membrane potential (∆Ψm), and are metabolically dependent upon oxidative phosphorylation (OXPHOS) and fatty acid oxidation (FAO). Selection of CD8 + T SCM subsets is therefore necessary to ensure a robust antitumor response. Previously, we revealed synergy between the Bcl-2 inhibitor, Venetoclax, and CAR T cells in the context of B-NHL. Venetoclax exposure increased CD8 + T SCM cell frequency, decreased ∆Ψm, reduced T Regulatory (T REG) cell frequency, and bolstered effector cytokine production. Though the role of Bcl-2 inhibition within B-NHLs is well characterized (FDA-approved for frontline and relapsed/refractory chronic lymphocytic leukemia [CLL] treatment), further investigation regarding the impact of Venetoclax on the patient T cell compartment is needed. In this study, we demonstrate a role for Venetoclax as a qualitative enhancer of bulk CAR T cell product using both healthy-donor and B-NHL patient-derived T cells, and implicate modulation of mitochondrial pathways as a likely mechanism of action. Methods Whole peripheral blood mononuclear cells were collected from consenting healthy human donors or CLL patients undergoing ramp-up with Venetoclax (BDR 164122) at Roswell Park Comprehensive Cancer Center, and activated with αCD3/αCD28. CLL samples were collected at baseline, 1 day, 7 days, and 1-month timepoints. Transduction was performed with lentiviral vectors encoding CD28 or 4-1BB-based α-CD19 CAR constructs 24 hours post-activation. Transduced cells were cultured in RPMI with hIL-2 and hIL-7. In vivo studies were performed on 7-week-old SCID mice using Raji-Luc, Rec-1, and U2932. Venetoclax was given daily [100mg/kg] via oral gavage. CAR T cells were delivered by single infusion via tail-vein injection at a dose of either 1x10 6 or 3x10 6 cells total.Mice were imaged via IVIS spectrum. Western blot was performed on stimulated untransduced T cells or CAR T cells exposed to Venetoclax. Total protein was quantified, and membranes were probed for apoptotic and mitochondrial protein expression. Patient sample immunophenotyping was performed on CLL patient samples using panels interrogating memory differentiation, exhaustion, and T REG populations. Results Consistent with our hypothesis, a significant increase in mitochondrial proteins associated with FAO and OXPHOS - ACC, PDH, and AMPKα - was observed in exposed CAR T cells, as well increased expression of transcription factor FOXO1 - an essential driver of CD8 + memory differentiation. Voltage-dependent anion channel (VDAC) expression increased, suggesting heightened efflux of respiratory substrates into the tricarboxylic acid cycle. Hexokinase-I, a critical glycolytic enzyme, was significantly downregulated. We next investigated our combination therapy in vivo and observed extended survival outcome by 15 days. Further in vivo studies investigating preclinical models of mantle cell lymphoma and activated B-cell diffuse large B-cell lymphoma are currently ongoing. Within our CLL patient samples, 24-hour and 7-day timepoints reflected a favorable population increase in CD8 + T SCM cells as compared to baseline samples, and marginally restored CD8 + T cell frequencies. Conclusion Metabolic properties guide T cell memory differentiation and fitness. There exists potential to manipulate this mechanism and select the most metabolically fit T cell population for adoptive cell therapies. In addition to answering fundamental questions of CAR T cell biology, the combination of Venetoclax and CAR T cell therapy may provide a solution to the observed clinical gap, in which CAR T therapy as a single agent does not afford favorable response rates in the context of aggressive and R/R B-NHLs.

Macrophage Mediated Abscopal Effects of Radiation Therapy

Radiation therapy (RT) can activate both innate and adaptive immune responses, and the combination of RT and immunotherapy is thought to be a promising strategy. We found that the "don't-eat-me" molecule CD47 is highly expressed on the surface of small cell lung cancer (SCLC) cells, a highly metastatic form of lung cancer, and that blockade of CD47 can enhance the phagocytosis of SCLC cells by macrophages. In this study, we investigated whether combining CD47 blockade and RT could synergize to inhibit the tumor growth of SCLC as well as other cancers in preclinical models. We evaluated efficacy and immune responses by RT and CD47 blockade in SCLC preclinical models as well as in colon cancer and lymphoma preclinical models. We engrafted cancer cells into both flanks of recipient mice and irradiated only one side of tumors with or without CD47 antibodies to investigate local and systemic effects of RT and CD47 blockade. We also used liver metastases models and endogenous lung tumor models to investigate anti-tumor effects and immune responses in their tumor microenvironments. In human patients, we investigated immune responses after RT using CIBERSORTx. We found CD47 blockade potently enhances the local antitumor effects of RT in all the pre-clinical models of SCLC we tested. Strikingly, CD47 blockade also stimulates systemic "abscopal" effects inhibiting non-irradiated SCLC tumors in mice receiving RT. These effects are observed in liver metastases models and endogenous lung tumor models as well as subcutaneous tumor models. Surprisingly, these abscopal effects are independent of T cells but require macrophages that migrate into non-irradiated tumor sites in response to inflammatory signals produced by RT and are locally activated by CD47 blockade to phagocytose cancer cells. Similar abscopal antitumor effects were observed in other cancer models treated with RT and CD47 blockade. We also found that RT increases tumor infiltrating macrophages in human cancer patients. Interestingly, these abscopal antitumor effects are enhanced by PD-1 blockade in some models. Our data clearly demonstrate macrophage-mediated abscopal responses of RT when combined with CD47 blockade in a range of cancer models. The systemic activation of antitumor macrophages following radiation and CD47 blockade may be particularly important in cancer patients who suffer from metastatic disease. RT is a part of standard-of-care and CD47-blocking strategies are in clinical trials, therefore our observations may be rapidly translatable to cancer patients.

A novel CAR-T cell product targeting CD74 is an effective therapeutic approach in preclinical mantle cell lymphoma models

BackgroundMantle cell lymphoma (MCL) is a rare B-cell non-Hodgkin lymphoma subtype which remains incurable despite multimodal approach including chemoimmunotherapy followed by stem cell transplant, targeted approaches such as the BTK inhibitor ibrutinib, and CD19 chimeric antigen receptor (CAR) T cells. CD74 is a nonpolymorphic type II integral membrane glycoprotein identified as an MHC class II chaperone and a receptor for macrophage migration inhibitory factor. Our group previously reported on CD74's abundant expression in MCL and its ability to increase via pharmacological inhibition of autophagosomal degradation. Milatuzumab, a fully humanized anti-CD74 monoclonal antibody, demonstrated significant activity in preclinical lymphoma models but failed to provide meaningful benefits in clinical trials mainly due to its short half-life. We hypothesized that targeting CD74 using a CAR-T cell would provide potent and durable anti-MCL activity.MethodsWe engineered a second generation anti-CD74 CAR with 4-1BB and CD3ζ signaling domains (74bbz). Through in silico and rational mutagenesis on the scFV domain, the 74bbz CAR was functionally optimized for superior antigen binding affinity, proliferative signaling, and cytotoxic activity against MCL cells in vitro and in vivo.ResultsFunctionally optimized 74bbz CAR-T cells (clone 42105) induced significant killing of MCL cell lines, and primary MCL patient samples including one relapse after commercial CD19 CAR-T cell therapy with direct correlation between antigen density and cytotoxicity. It significantly prolonged the survival of an animal model established in NOD-SCIDγc−/− (NSG) mice engrafted with a human MCL cell line Mino subcutaneously compared to controls. Finally, while CD74 is also expressed on normal immune cell subsets, treatment with 74bbz CAR-T cells resulted in minimal cytotoxicity against these cells both in vitro and in vivo.ConclusionsTargeting CD74 with 74bbz CAR-T cells represents a new cell therapy to provide a potent and durable and anti-MCL activity.

OPEN‐LABEL PHASE 1/2 STUDY OF CC‐99282, A CEREBLON E3 LIGASE MODULATOR (CELMOD) AGENT ± RITUXIMAB, IN PATIENTS WITH RELAPSED/REFRACTORY (R/R) NON‐HODGKIN LYMPHOMA (NHL)

Introduction: CC-99282 is a novel, oral, small molecule CELMoD® agent that co-opts cereblon to induce targeted degradation of Ikaros/Aiolos, transcription factors critical for B-cell malignancy development. Compared with immunomodulatory drugs (IMiD), CC-99282 had 10- to 100-fold enhanced antiproliferative and apoptotic activity in preclinical models of diffuse large B-cell lymphoma (DLBCL), while maintaining immunostimulatory effects. We previously reported promising efficacy and a predictable and manageable safety profile of CC-99282 in patients (pts) with R/R NHL (Michot et al. EHA, 2022). Methods: CC-99282-NHL-001 (NCT03930953) is a 2-part, multicentre, first-in-human study with dose escalation of CC-99282 monotherapy (part A) and expansion ± combination partners (part B) in pts with R/R DLBCL or follicular lymphoma (FL) who progressed after ≥2 lines of therapy, or pts with R/R DLBCL with ≥1 line of standard therapy and transplant-ineligible. Part A dosing is CC-99282 0.2–0.8 mg QD on 3 intermittent schedules of 28 d cycles. Part B dosing is CC-99282 0.2 or 0.4 mg alone on 2 intermittent schedules or with rituximab (RTX). Here, we report updated efficacy results for CC-99282 monotherapy (part A) and new safety data for CC-99282 + RTX (part B). Results: For part A, as of Sep 14, 2022, 50 pts were treated (38 DLBCL, 12 FL; median age 66 y); 3 pts (6%) completed, 7 (14%) were ongoing and 40 (80%) discontinued, most commonly due to progressive disease (n = 33, 66%). Median # of prior systemic anticancer therapies was 3 (range 1–8). For doses ≥0.4 mg on 7/14 or 14/28 d schedules, the overall response rate was 43% (17/40 evaluable pts; 10/30 DLBCL, 7/10 FL), with complete response in 7 and partial response in 10 pts. Responders included pts previously treated with CAR T cell therapy and/or IMiD/CELMoD agents. Responses were durable (Figure), with median duration of response (mDOR) of 299 d (range 48–898; median follow-up [mFU] 293) in pts with DLBCL and mDOR of 448 d (135–930; mFU 572) in pts with FL. For part B, as part of the safety run-in, 12 pts were treated with CC-99282 + RTX (9 DLBCL, 3 FL; median age 61y). With mFU of 6 wks (range 4–28), neutropenia was the most common any-grade treatment-emergent adverse event (AE), occurring in 5/12 (42%) pts, including 25% (3/12) grade 3/4 neutropenia. No febrile neutropenia occurred. There were no dose reductions, discontinuations, or dose-limiting toxicities (DLTs). Severe AEs included fever (n = 2), and dyspnoea and fatigue (n = 1 each). Similar safety profiles were observed at both CC-99282 dose levels, 0.2 and 0.4 mg, combined with RTX. The research was funded by: Celgene, a Bristol-Myers Squibb Company Keywords: aggressive B-cell non-Hodgkin lymphoma, combination therapies, indolent non-Hodgkin lymphoma Conflicts of interests pertinent to the abstract J. M. Michot Honoraria: Ideogen Educational grants: Amgen J. Chavez Consultant or advisory role: Advisory board of Kite and Novartis C. Carpio Consultant or advisory role: Consultancy: Takeda, Regeneron, Novartis Educational grants: Celgene E. Bachy Consultant or advisory role: Consultancy: Roche, Takeda, Incyte Honoraria: Kite/Gilead, Novartis Research funding: Daiishi F. Morschhauser Consultant or advisory role: Consultancy: Roche, Gilead, Genmab, Novartis, Abbvie J. M. Jørgensen Consultant or advisory role: Advisory board: Roche, Gilead, Novartis, BMS R. Cordoba Consultant or advisory role: Advisory role: BMS, Janssen, Abbvie, Astra Zeneca, Eli Lilly, Beigene, Kite P. Bories Consultant or advisory role: Consultancy: Abbvie; Advisory role: Kite/Gilead Research funding: BMS Educational grants: Kite/Giliead P. Patah Employment or leadership position: Employment: BMS Other remuneration: Equity ownership: BMS B. de Moucheron Employment or leadership position: Employment: BMS Stock ownership: BMS S. Carrancio Employment or leadership position: Employment: BMS Stock ownership: BMS C. Guarinos Employment or leadership position: Employment: BMS X. Zheng Employment or leadership position: Employment: BMS C. Mei Employment or leadership position: Employment: BMS M. Pourdehnad Employment or leadership position: BMS Stock ownership: BMS L. Nastoupil Honoraria: DC Therapeutics, Abbvie, BMS/Celgene, Incyte, Caribou Biosciences, Epizyme, Genentech, Gilead/Kite, Janssen, Novartis, Pfizer, Takeda Research funding: BMS/Celgene, Caribou Biosciences, Epizyme, Genentech, Gilead/Kite, IGM Biosciences, Janssen, Novartis, Pfizer, Takeda

Lenalidomide overcomes the resistance to third-generation CD19-CAR-T cell therapy in preclinical models of diffuse large B-cell lymphoma.

Chimeric antigen receptor (CAR)-T cells against CD19 have been proven to be effective in treating B-cell hematological malignancies. However, the efficacy of this promising therapy is limited by many factors. In this study, the germinal center B-cell-like diffuse large B-cell lymphoma (GCB-DLBCL) cell line OCI-Ly1, and patient-derived xenografted (PDX) mice (CY-DLBCL) were used as the CAR-T cell-resistant model. Meanwhile, the activated B-cell-like (ABC) DLBCL cell line OCI-Ly3 and PDX mice (ZML-DLBCL) were defined as the CAR-T sensitive model. The enhancement of CAR-T cell function by lenalidomide (LEN) was examined in vitro and in vivo. Lenalidomide effectively enhanced the function of third-generation CD19-CAR-T cells by polarizing CD8+ CAR-T cells to CD8 early-differentiated stage and Th1 type, reducing CAR-T cell exhaustion and improving cell expansion. It was further demonstrated that CAR-T cells combined with LEN substantially reduce the tumor burden and prolong the survival time in various DLBCL mouse models. LEN was also found to promote the infiltration of CD19-CAR-T cells into the tumor site by modulating the tumor microenvironment. In summary, the results of the present study suggest that LEN can improve the function of CD19-CAR-T cells, providing a basis for clinical trials using this combination therapy against DLBCL.

Chimeric TIM-4 receptor-modified T cells targeting phosphatidylserine mediates both cytotoxic anti-tumor responses and phagocytic uptake of tumor-associated antigen for T cell cross-presentation

To leverage complementary mechanisms for cancer cell removal, we developed a novel cell engineering and therapeutic strategy co-opting phagocytic clearance and antigen presentation activity into Tcells. We engineered a chimeric engulfment receptor (CER)-1236, which combines the extracellular domain of TIM-4, a phagocytic receptor recognizing the "eat me" signal phosphatidylserine, with intracellular signaling domains (TLR2/TIR, CD28, and CD3ζ) to enhance both TIM-4-mediated phagocytosis and Tcell cytotoxic function. CER-1236 Tcells demonstrate target-dependent phagocytic function and induce transcriptional signatures of key regulators responsible for phagocytic recognition and uptake, along with cytotoxic mediators. Pre-clinical models of mantle cell lymphoma (MCL) and EGFR mutation-positive non-small cell lung cancer (NSCLC) demonstrate collaborative innate-adaptive anti-tumor immune responses both invitro and invivo. Treatment with BTK (MCL) and EGFR (NSCLC) inhibitors increased target ligand, conditionally driving CER-1236 function to augment anti-tumor responses. We also show that activated CER-1236 Tcells exhibit superior cross-presentation ability compared with conventional Tcells, triggering E7-specific TCR T responses in an HLA class I- and TLR-2-dependent manner, thereby overcoming the limited antigen presentation capacity of conventional Tcells. Therefore, CER-1236 Tcells have the potential to achieve tumor control by eliciting both direct cytotoxic effects and indirect-mediated cross-priming.

SP-3164, a Novel Cereblon-Binding Protein Degrader, Shows Activity in Preclinical Lymphoma Models

Background: Targeted protein degradation (TPD) is attracting significant interest given the success of early protein degraders, e.g., lenalidomide and pomalidomide, and TPD's potential advantages over other therapeutic approaches. SP-3164, an oral, next-generation molecular glue, is currently in IND-enabling studies and is expected to enter the clinic in 2023. SP-3164 interacts with the cereblon (CRBN) component of a CRL4 E3 ligase, inducing recruitment of select proteins, i.e., Ikaros (IKZF1) and Aiolos (IKZF3), leading to their ubiquitination and proteasomal degradation. To date, most CRBN-binding compounds, including SP-3164, contain a chiral aminoglutarimide moiety and exist as (S)- and (R)-enantiomers. Studies have shown that in many of these CRBN-binding compounds, it is the (S)-enantiomer that binds to CRBN with increased affinity and thus may be the primary species resulting in the desired protein degradation and anti-cancer activity. However, the (S)- and (R)-enantiomers can chemically interconvert, preventing development of a single enantiomer. SP-3164 was designed using deuterium to stabilize the (S)-enantiomer with the potential for an improved therapeutic profile compared to the clinically studied racemate, avadomide. We previously demonstrated that compared to avadomide, SP-3164 shows increased binding affinity to CRBN, while the deuterium-stabilized (R)-enantiomer (SP-3165) does not bind CRBN at clinically relevant concentrations. Here, we further characterize SP-3164 pharmacological properties compared to avadomide, SP-3165, and lenalidomide, and demonstrate its activity in preclinical lymphoma models. Results: In addition to CRBN binding, efficiency of TPD is another critical parameter. In in vitro studies of diffuse large B cell lymphoma (DLBCL) cell lines of different subtypes (WSU-DLCL2, SU-DHL-5, SU-DHL-10 and U-2932), SP-3164 (500 nM) resulted in greater IKZF1 degradation at 6 hours (Figure 1A), when compared to avadomide (AVA, 1 µM) or lenalidomide (LEN, 10 µM). By contrast, SP-3165 (500 nM) did not result in meaningful IKZF1 depletion, further corroborating the (R)-enantiomer as the inactive species. Pharmacokinetics (PK) of SP-3164, SP-3165, and avadomide were studied in mice. Oral administration of either SP-3164 or SP-3165 resulted in increased exposure to the dosed enantiomer when compared to an equivalent dose of avadomide, and minimal exposure to the other enantiomer, while the elimination half-life of SP-3164 and SP-3165 was approximately half that of the enantiomers of avadomide. Therefore, SP-3164 has the potential to be administered at lower doses in clinic and provide a more flexible dosing regimen compared to avadomide, while still maintaining sufficient exposure for anticancer activity. The in vivo efficacy of SP-3164 for lymphoma was studied in a WSU-DLCL2 mouse xenograft model (Figure 1B). Compared to lenalidomide, SP-3164 exhibited significantly increased tumor growth inhibition (TGI). SP-3164 and avadomide showed similar activity at comparable doses and dosing regimens (SP-3164, 15 mg/kg QD, and avadomide, 30 mg/kg QD). SP-3165 lacked significant anti-cancer effects indicating that the (R)-enantiomer does not contribute to the direct anti-cancer activity of avadomide, as anticipated based on its lack of binding to CRBN. Due to the shorter elimination half-life of SP-3164 compared to avadomide, SP-3164 was also dosed BID. The SP-3164 BID treated group had the largest TGI, suggesting that the in vivo anti-cancer activity may be due to sustained exposure of SP-3164 at the tumor resulting in prolonged reduction of target protein levels. Conclusion: SP-3164 is a novel, CRBN-binding molecular glue with potential attractive therapeutic properties compared to the racemate, avadomide, and to lenalidomide. SP-3164 showed increased IKZF1 degradation efficiency compared to other molecular glues and significant anti-cancer activity as a monotherapy in an in vivo lymphoma mouse xenograft model. Future studies will evaluate SP-3164 efficacy and direct potential combinations to support clinical development of SP-3164 in DLBCL and other non-Hodgkin's lymphomas. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Targeting Sumoylation with Subasumstat (TAK-981), a Selective Inhibitor of SUMO-Activating Enzyme (SAE), Induces Mitochondrial Dysfunction in Preclinical Models of Non-Hodgkin Lymphoma (NHL)

SUMOylation is a post-translational modification which leads to covalent attachment of small ubiquitin-like modifiers (SUMO) proteins to lysine residues of a target protein. SUMOylation is essential for the regulation of genomic integrity, gene expression and intracellular signaling. Many tumors exhibit deregulation of SUMOylation pathway. Subasumstat, (TAK-981), a novel selective inhibitor of SUMO-activating enzyme (SAEi), has entered early phase II clinical trials. Here we studied SAEi in pre-clinical models of B-cell non-Hodgkin's lymphoma (NHL). TAK-981 was provided by Takeda Development Center Americas, Inc. (Lexington, MA). Diffuse large B-cell lymphoma (DLBCL) cell lines (OCI-LY3, VAL, U-2932, SU-DHL10), and primary mantle cell lymphoma (MCL) cells were assayed for survival, mitochondrial function, and metabolic phenotype. In vivo experiments were performed using DLBCL cell line xenografts and MCL PDX models. Treatment with TAK-981 restricted growth of DLBCL cell lines with an IC50~10 nM. SAEi led to rapid (within 2 h) protein desumoylation in a dose dependent manner, prominently in the ~90 kDa region. TAK-981 induced pronounced double strand DNA breaks in DLBCL cells (comet assay) and cell cycle arrest (propidium iodine). RNA-Seq and ATAC-Seq analysis of TAK-981-treated DLBCL cells revealed upregulation of the DNA damage, NF-κB, and OXPHOS signaling pathways. We noted that in addition to cytoplasmic proteins, mitochondrial proteins were heavily de-SUMOylated upon treatment of NHL cells with TAK-981. In vitro exposure to TAK-981 resulted in mitochondrial membrane depolarization, loss of mitochondrial integrity (by electron microscopy) and a change of mitochondrial dynamics as assessed by expression of mitochondrial proteins (eg, Drp1). Seahorse respirometry analysis revealed dramatic downmodulation of OXPHOS following SAEi. Furthermore, metabolomic profiling of DLBCL cells treated with TAK-981 showed downmodulation of TCA substrates, while glycolysis substrates remained unchanged. The mitochondrial disruption observed following TAK-981 treatment was accompanied by rapid accumulation of reactive oxygen species, a mechanism that has been previously shown to lead to DNA damage in cancer cells. Consistent with cell line data, exposure of primary MCL cells to TAK-981 in stromal conditions (CD40L- or BAFF expressing stroma) induced apoptosis and reduced OXPHOS. Next, we conducted genome-wide CRISPR-Cas9 loss-of-function library screens and identified that loss of genes in the NFκB, TP53, DNA damage and centromere/telomere gene pathways contributed to resistance to SAEi in DLBCL cells. By means of genetic knockout we demonstrated that TP53 and its transcriptional target BAX contributed to TAK-981-induced G2 arrest and apoptosis, further implicating mitochondrial dysfunction in sensitivity to SAEi. For in vivo experiments, we used DLBCL xenografts. OCI-LY3 and U-2932 cells were inoculated subcutaneously in NSG mice. Once tumors reached 100 mm3, mice received 10 twice-weekly IV doses of 7.5 mg/kg TAK-981 (over 5 weeks), leading to resolution of flank tumors and improved survival compared with control. Finally, we used an MCL PDX model where MCL cells were inoculated intravenously. Once cells became detectable in the blood, mice were treated as above. Treatment with TAK-981 resulted in delayed tumor expansion in blood and spleen and extended animal survival. TAK-981-exposed splenocytes exhibited a reduction of maximal respiration by Seahorse analysis. Conclusions. Pharmacologic SAEi with TAK-981 demonstrated pre-clinical activity in NHL models in vitro and in vivo, accompanied by DNA damage, mitochondrial dysfunction, and metabolic reprogramming.

Safety, Tolerability, Pharmacokinetics (PK) and Preliminary Antitumor Activity of the Cyclin-Dependent Kinase-9 (CDK9) Inhibitor AZD4573 in Relapsed/Refractory Hematological Malignancies: A Phase 1 First-in-Human Study

Introduction: CDK9, a serine/threonine kinase, regulates transcription elongation by phosphorylating RNA polymerase II at serine 2 (pSer2). Transient inhibition of CDK9 modulates expression of genes with short-lived transcripts and labile proteins, providing a potential therapeutic opportunity in tumors dependent upon oncogenes fitting these criteria. AZD4573 is a highly potent and selective CDK9 inhibitor that rapidly and preferentially decreases BCL2 family anti-apoptotic proteins MCL-1, BFL-1 as well as the oncogene MYC, inducing apoptosis in a broad range of human hematological malignant cell lines. AZD4573 monotherapy has shown antitumor effects associated with transient CDK9 inhibition in leukemia and lymphoma preclinical models. This multicenter, nonrandomized, open-label, phase 1 study (NCT03263637) was conducted to assess safety, tolerability, PK, pharmacodynamics (PD) and preliminary antitumor activity of AZD4573 in patients (pts) with relapsed or refractory hematological malignancies. Methods: The study comprised two parallel dose-escalation arms using a 3+3 design. Arm A included pts with diffuse large B-cell lymphoma (DLBCL), mantle cell lymphoma, or multiple myeloma. Arm B included pts with acute myeloid/lymphocytic leukemia, chronic myelomonocytic/lymphocytic leukemia, or hairy cell leukemia. Pts must have received at least 2 prior lines of therapy for the current histology. In each arm, pts received AZD4573 IV on an 8-week cycle using an intra-patient ramp up starting at 6 mg and increasing in 3 mg increments to a target dose of 18 mg (cohort 1) or 12 mg (cohort 2). The initial dosing regimen was 2 days on/12 days off but was changed to once weekly (QW) in cohort 1. Pts in Cohort 3 received AZD4573 9 mg QW on a 4-week cycle including intra-patient ramp up (3 mg, 6 mg, 9 mg). The primary objectives were to assess safety and to determine the biologically effective dose/maximum tolerated dose (MTD). Adverse events (AE) were assessed using CTCAE v4.03. Secondary/exploratory endpoints included PK, PD, and antitumor efficacy. Results: Overall, 44 pts were treated and evaluated for safety and efficacy: 22 each in Arms A and B. Median age was 69.0 years (range, 26.0 - 84.0), 65.9% were male, and median number of prior lines of therapy was 3 (range, 1-11). At data cutoff (Sept 30, 2021), all pts had discontinued treatment, mainly due to disease progression (47.7%) or AEs (22.7%). All pts had treatment-emergent adverse events (TEAEs) which were serious in 88.6%. The most common TEAEs were diarrhea (59.1%), pyrexia (52.3%) and nausea (50.0%). The most common TEAE that led to discontinuation was pneumonia (4.5%). Treatment-related AEs (TRAEs) occurred in 93.2% of pts and were serious in 59.1%, but none led to death. The most common TRAEs were diarrhea (50%), nausea (47.7%) and tumor lysis syndrome (TLS, 40.9%: laboratory TLS, 38.6%; clinical TLS, 6.8%) (Table 1). Elevated liver enzymes were transient and resolved spontaneously. These increases were assumed to be mainly due to down-modulation of hepatic transporter proteins and reduced enzyme clearance rather than direct hepatocellular cytotoxicity (based on clinical, in-vitro and in-silico assessments). Regarding MTD, the 18 mg dose was not tolerated in either arm (clinical TLS and acute kidney injury in Arm A; hypotension and liver injury in Arm B). AZD4573 12 mg was tolerated in Arm A, but not tolerated in Arm B due to clinical TLS (n=2). The recommended Phase 2 dose (RP2D) was 12 mg QW in Arm A and 9 mg QW in Arm B. AZD4573 showed dose-proportional increases in AUC and Cmax, with moderate PK variability (~30-60% CV), and a t1/2 of ~5 hrs. Furthermore, AZD4573 led to dose-dependent reduction in pSer2 (>75%) and MCL-1 (>70%) in peripheral blood as evidence of target engagement and mechanism of action. Median duration of exposure was 10.1 wks in Arm A (range, 1.0-130.1) and 5.2 wks in Arm B (range, 1.0-35.7). In Arm A, there was 1 complete and 1 partial response in 17 DLBCL pts. Median overall survival was not reached in Arm A and was 8.8 months in Arm B, with 7 (31.8%) deaths in each. Conclusion: AZD4573 had manageable safety and a PK profile suitable for QW dosing in a broad range of hematologic malignancies including lymphoma and leukemia. The reduction in pSer2 and MCL-1 supports the RP2D of 12 mg for lymphoma and 9 mg for leukemia. A combination study of AZD4573 and acalabrutinib (NCT04630756) is ongoing to further examine the DLBCL response signal seen in this study. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Evaluation of Epcoritamab and Rituximab Combination in Preclinical Models of B-Cell Non-Hodgkin's Lymphoma (NHL)

Background: Epcoritamab (Epco) is a CD3 bispecific antibody that induces selective, potent T-cell-mediated killing of CD20-positive malignant B-cells. In the phase 1/2 monotherapy study, subcutaneous administered Epco showed a favorable safety profile and promising efficacy, including complete responses in heavily pretreated patients with relapsed / refractory non-Hodgkin's lymphoma (Hutchings et al, Lancet 2021; Thieblemont et al, EHA 2022, LB2364; EPCORE NHL-1). Ongoing clinical studies combining Epco with standard-of-care therapies including combinations with Rituximab show promising preliminary anti-tumor activity in diffuse large B-cell lymphoma and follicular lymphoma (Falchi et al, ASCO 2022 abstracts 7523 and 7524; EPCORE NHL-2 arm 1 and 2; NCT04663347). Here we evaluated the competition for CD20 binding and functional interactions between these agents and modeled its impact on Epco, T-cell, and tumor cell trimer formation that drives Epco clinical activity. Aims: Investigate the preclinical binding and functional interaction between Epco and Rituximab to establish the potential for the combination of these agents in the treatment of B-cell NHL. Methods: Competition between Epco and Rituximab for binding to CD20 cells was assessed by Flow Cytometry after incubating the single labeled agent in the presence of increasing concentrations of the competitor and vice-versa (across 0.1 - 300 ug/ml evaluated for each agent), on a range of CD20 expressing lymphoma cell lines. Epco-induced-T cell activation and redirected T cell cytotoxicity was determined by co-culturing T cells with lymphoma cells with varying expression of CD20. Rituximab antibody-dependent cellular cytotoxicity (ADCC) activity was assessed by incubating fresh peripheral blood mononuclear cells with lymphoma cells in the presence of a CD3 control Epco antibody (DuoBody-ctrlxCD20). Data from binding and cytotoxicity was used to quantify the degree of binding curve shifts at different Rituximab:Epco concentrations as well as the impact on predicted trimer formation and cytotoxicity, based on modeling. Results: In binding assays, the addition of Rituximab resulted in a dose-dependent reduction of Epco binding to CD20 expressing lymphoma cell lines, with a significant reduction of Epco binding observed at clinically relevant Epco concentrations in cells with high CD20 expression levels (Figure 1). Similar binding interference interactions were observed for binding of Epco to cell lines with low and intermediate CD20 expression levels. Binding of Rituximab to cell lines expressing high CD20 levels was not significantly reduced by clinically relevant concentrations of Epco. In Epco functional studies, the addition of increasing concentrations of Rituximab did not affect Epco cytotoxic activity at clinically relevant range of Rituximab doses tested (Figure 2). Similarly, no effect of Rituximab on Epco-mediated T cell activation was observed at clinically relevant concentrations of Rituximab and Epco. ADCC activity at clinically relevant concentrations of Rituximab (10-250 ug/ml) was not impacted by incubation with the CD3 control Epco antibody (DuoBody-ctrlxCD20), even at concentrations exceeding the Epco clinical concentrations. Modeling and simulation of in vitro data showed that at clinically relevant concentration of Epco, the presence of clinically relevant concentration of Rituximab does not meaningfully impact Epco trimer formation, and the predicted trimer formation remains above EC90 relative to that needed for 50% cell kill. Conclusions: Our studies showed that while Rituximab exerts significant interference on Epco binding to CD20-expressing cells, tumor-cell cytotoxicity by Epco is minimally affected by clinically relevant concentrations of Rituximab. This conclusion is supported by preclinical modeling and simulations showing that Epco activity driven by trimer formation is not meaningfully impacted by clinical concentrations of Rituximab. Furthermore, we found a limited effect of Epco on Rituximab binding to CD20 and no impact on ADCC activity by Rituximab, thereby supporting potential synergy in the combination between these agents. Results from this study confirm the ability to combine Epco with CD20 antibodies, specifically with Rituximab, and the potential for synergistic activity of this combination. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal