Activity In Preclinical Models Research Articles

The selective 5-HT1F receptor agonist lasmiditan inhibits trigeminal nociceptive processing: Implications for migraine and cluster headache.

Lasmiditan is a novel selective 5-HT1F receptor agonist, recently approved for acute treatment of migraine. 5-HT1F receptors are widely expressed in the CNS and trigeminovascular system. Here, we have explored the therapeutic effects of 5-HT1F receptor activation in preclinical models of migraine and cluster headache. Electrical stimulation of the dura mater or the superior salivatory nucleus in anaesthetised rats evoked trigeminovascular or trigeminal-autonomic reflex activation at the level of the trigeminocervical complex. Additionally, cranial autonomic manifestations in response to trigeminal-autonomic reflex activation were measured, via anterior choroidal blood flow alterations. These responses were then challenged with lasmiditan. We explored the tissue distribution of mRNA for 5-HT1F receptors in human post-mortem tissue and of several 5-HT1 receptor subtypes in specific tissue beds. Lasmiditan dose-dependently reduced trigeminovascular activation in a preclinical model of migraine. Lasmiditan also reduced superior salivatory nucleus-evoked activation of the trigeminal-autonomic reflex, but had no effect on cranial autonomic activation. mRNA profiling in human tissue showed expression of the 5-HT1F receptor in several structures relevant for migraine and cluster headache. Our data suggest that lasmiditan acts, at least in part, as an anti-migraine agent by reducing trigeminovascular activation. Furthermore, our results highlight a clear action for lasmiditan in a preclinical model of cluster headache. Given the proven translational efficacy of this model, our data support the potential utility of lasmiditan as a therapeutic option for the acute treatment of cluster headache attacks. This article is part of a themed issue on Advances in Migraine and Headache Therapy (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.3/issuetoc.

CC-99282 is a Novel Cereblon (CRBN) E3 Ligase Modulator (CELMoD) Agent with Enhanced Tumoricidal Activity in Preclinical Models of Lymphoma

CC-99282 is a novel, oral CELMoD ® agent currently under investigation in phase 1 clinical studies in patients with relapsed or refractory (R/R) non-Hodgkin lymphomas (NHL) and chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). Mechanistically, CC-99282 interacts with the CRL4 CRBN E3 ubiquitin ligase substrate receptor CRBN to induce recruitment and ubiquitin-mediated proteasomal degradation of transcription factors Ikaros and Aiolos. The design intent for CC-99282 included efficient absorption, deep tissue distribution, and prolonged exposure to optimize activity in bulky lymphoma lesions. Recently, we reported that CC-99282 shows potent antitumor activity in different preclinical models of diffuse large B cell lymphoma (DLBCL; Lopez-Girona, et al. Hematol Oncol. 2021). Here, we provide an expanded analysis of CC-99282 activity as a monotherapy, as well as examine its synergistic activity with anti-CD20 antibody treatment, in preclinical models of NHL including DLBCL and follicular lymphoma (FL).Compared with existing agents targeting Ikaros/Aiolos that show activity in hematologic malignancies, such as lenalidomide, avadomide, and iberdomide (CC-220), CC-99282 induced a more rapid, deep, and sustained degradation of Ikaros/Aiolos, causing derepression of cyclin-dependent kinase (CDK) inhibitors and interferon-stimulated genes (IRF7, IFIT3, and DDX58), and the reduction of the highly critical oncogenic factors c-Myc and IRF4. These molecular changes were followed by potent, 10- to 100-fold enhanced, autonomous cell killing and induction of apoptosis (Figure). Our results show that these effects were independent of the cell of origin (activated B cell [ABC; TMD8 cell line], germinal center B cell [GCB; WSU-DLCL2 cell line], or primary mediastinal B cell lymphoma [PMBL] subtypes of DLBCL) or presence of high-risk chromosomal translocations (MYC, BCL2, and/or BCL6), as observed in a panel of 36 lymphoma cell lines that included DLBCL and FL cell lines. In vivo, CC-99282 demonstrated robust tissue distribution that favored target tissues and exhibited antitumor activity resulting in improved tumor regression and tumor-free animals in several lymphoma xenograft models, including an intracranial xenograft model. This strong antitumor activity was observed using various continuous and intermittent dosing paradigms.The potent, direct autonomous cell-killing activity of CC-99282 was augmented when CC-99282 was combined with the anti-CD20 antibody rituximab. In vitro combination studies of CC-99282 with rituximab in lymphoma cell lines demonstrated enhanced cell killing by human natural killer (NK) cells, macrophage-mediated phagocytosis, antibody-dependent cellular cytotoxicity (ADCC), and antibody-dependent cellular phagocytosis (ADCP). In FL and DLBCL cell lines, we showed that the combination of CC-99282 with rituximab resulted in increases in both NK-mediated ADCC and macrophage-mediated ADCP of up to 20% compared with rituximab treatment alone. In vivo, combination treatment with CC-99282 and rituximab induced dose-dependent tumor growth inhibition in WSU-DLCL2 and RL (FL) xenograft models. In the WSU-DLCL2 model, CC-99282 (1 mg/kg) or rituximab (10 mg/kg) monotherapy resulted in modest tumor growth inhibition, whereas the combination of CC-99282 (1 mg/kg) and rituximab (10 mg/kg) resulted in tumor regression in 100% of animals. Similar results were obtained in FL xenograft models using the RL cell line, where combinations of CC-99282 (1 mg/kg) with rituximab (25 mg/kg) induced complete tumor regression in 100% of animals.In conclusion, CC-99282 is a novel CELMoD agent with an improved substrate degradation profile compared with existing Ikaros/Aiolos-degrading agents. CC-99282 demonstrated enhanced antiproliferative and apoptotic activities across a broad range of lymphoma cells and a robust distribution profile that favors target tissues such as lymphoid organs. In addition, CC-99282 acts synergistically in combination with anti-CD20 monoclonal antibody treatment. Collectively, these data support the clinical investigation of CC-99282 as monotherapy and in combination with rituximab in patients with R/R NHL. [Display omitted] DisclosuresCarrancio: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Groocock: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Janardhanan: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Jankeel: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Galasso: Ryan Galasso: Current Employment, Current equity holder in publicly-traded company. Guarinos: Bristol Myers Squibb: Current Employment. Narla: Bristol Myers Squibb: Current Employment. Groza: Bristol Myers Squibb: Current Employment. Leisten: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Pierce: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Rolfe: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Lopez-Girona: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company.

A Phase 1 Dose-Escalation Study of the Oral CDK Inhibitor Voruciclib in Patients with Relapsed/Refractory B-Cell Malignancies or Acute Myeloid Leukemia (AML): Preliminary Results of the Completed Dose Escalation Stage in AML

A Phase 1 Dose-Escalation Study of the Oral CDK Inhibitor Voruciclib in Patients with Relapsed/Refractory B-Cell Malignancies or Acute Myeloid Leukemia (AML): Preliminary Results of the Completed Dose Escalation Stage in AML

Dominant Expression of PVRIG and TIGIT Inhibitory Pathways in Bone Marrow of Multiple Myeloma Patients

IntroductionBlocking inhibitory immune checkpoints holds promise to treat multiple myeloma (MM) patients. However, currently available checkpoint inhibitors have not shown significant clinical benefits for MM patients, warranting the need for alternative checkpoint blockers. The immune checkpoint TIGIT was recently shown to be the most upregulated immune inhibitory receptor on CD8+ T cells in MM patients' bone marrow (BM), compared to other checkpoints (Guillerey C., Blood. 2018). Preclinical models demonstrated the dominant effects of TIGIT blockade or depletion, by significantly improving mice survival, reducing myeloma cell numbers and exhausted T cell hallmarks (Minnie S., Blood. 2018). As a result, several clinical trials using anti-TIGIT monoclonal antibodies have been recently initiated in MM patients.The DNAM-1 family, in addition to TIGIT, also includes the inhibitory receptor PVRIG, that competes with the co-activating receptor DNAM-1 for the binding to the shared ligand PVRL2, similarly to the TIGIT/PVR/DNAM-1 interaction. Accordingly, TIGIT and PVRIG co-blockade were shown to synergize in enhancing T cell activity and anti-tumor activity in preclinical models (Whelan S., Cancer Immunol. Res. 2019). PVRL2 together with PVR (ligand of TIGIT) were shown to be highly expressed on plasma cells and on CD14+ cells in BM of MM patients (Lozano E., Clin. Cancer Res. 2020). This study aimed at evaluating DNAM-1 axis receptors expression in MM patients' BM.MethodsFresh BM aspirates were collected from 21 MM patients with progressive disease (PD) or in complete response (CR) after obtaining IRB approval. BM mononuclear cells were isolated and single cell suspensions were obtained followed by staining with anti-human antibodies to evaluate DNAM-1 axis members and PD-1 expression. BM biopsies from 6 MM patients (each patient had 4 core on the Tissue Micro-Array T291 USBiomax) were stained for PVRL2 expression by immuno-histochemistry (IHC).ResultsFlow cytometry analysis of PD-1 and DNAM-1 axis receptors revealed a significant lower fraction of PD1+ cells among cell populations examined compared with other receptors. TIGIT expression was the highest on NK, CD8+ and NKT cells compared to CD4+ T cells, which is in line with previous published data (Lozano E. Clin. Cancer Res. 2020). In contrast, DNAM-1 was expressed on CD8+ T, NK and NKT cells with prominent high expression on CD4+ T cells (Fig 1A). The highest expression among the receptors was of PVRIG on all lymphoid populations, except CD4+ where DNAM-1 was more highly expressed. Importantly, 50% of CD8+ T cells co-expressed TIGIT and PVRIG, supporting a combinatorial therapeutic approach (Fig. 1B).Additionally, the expression of the PVRL2 ligand on MM plasma and endothelial cells was demonstrated by IHC. FACS analysis further supported PVRL2 expression on plasma cells in MM BM (Fig 2).A higher expression of PVRIG, TIGIT and PD-1 was present on DNAM-1 negative CD8+ T cells (Fig 3A, B), suggesting accumulation of exhausted cells in MM tumor microenvironment (TME) as previously described (Minnie S., Blood. 2018). PVRIG had significantly higher expression on DNAM+ cells, compared to PD-1 and TIGIT (Fig 3C), suggesting the potential of its blockade to enhance DNAM-1 activation and subsequent proliferation of earlier differentiated memory cells in MM TME. Finally, CR patients had a trend for higher DNAM-1 expression on CD8+ T cells compared to those with PD (Fig 3D). This is consistent with other reports in mice showing that the expression of DNAM-1 negatively correlates with BM myeloma cell numbers (Minnie S., Blood. 2018).ConclusionsDNAM-1 axis receptors are dominantly expressed on lymphocytes in BM of MM patients, with PVRIG exhibiting the most prominent expression. The reduced expression of DNAM-1 in PD patients' TME, compared to CR patients, suggests a link between DNAM-1 axis and clinical outcomes. Recent data suggest TIGIT is an attractive target for blockade in MM. Our new findings highlight for the first time the dominant expression of PVRIG, as well as TIGIT, and suggest that combined blockade of TIGIT with PVRIG may potentially benefit MM patients, placing the DNAM-1 axis as a dominant pathway in MM therapy. [Display omitted] DisclosuresFrenkel: Compugen Ltd.: Current Employment, Other: in the event of frontal participation, I will be reimbursed for my travel expenses by Compugen Ltd.. Alteber: Compugen Ltd.: Current Employment. Cojocaru: Compugen Ltd.: Current Employment. Ophir: Compugen Ltd.: Current Employment.

NL-201, a De Novo Agonist of IL-2 and IL-15 Receptors, Demonstrates Synergistic Antitumor Activity with Anti-PD-1 Checkpoint Inhibitor Therapy in a Preclinical Non-Hodgkin Lymphoma Model

NL-201 is a potent, selective, and long-acting computationally designed alpha-independent agonist of the IL-2 and IL-15 receptors that is being developed as an immunotherapy for cancer. NL-201 binds to the beta and gamma subunits, selectively stimulating dose-dependent expansion and tumor infiltration of cytotoxic CD8+ T cells and natural killer (NK) cells, thereby enhancing the immune response to the tumor. Absence of binding to the IL-2 alpha subunit reduces the undesirable effects of traditional IL-2 therapies, such as vascular leak syndrome and expansion of immunosuppressive regulatory T cells. In this abstract, we demonstrate that NL-201, alone or in combination, demonstrates robust antitumor activity in preclinical models of non-Hodgkin lymphoma (NHL).We have previously demonstrated that NL-201 has marked antitumor activity in multiple syngeneic tumor models, including the A20 lymphoma model. These observations in lymphoma have been extended to explore the effects of NL-201 in combination with anti-mPD-1 checkpoint inhibitor therapy in vivo. In this model, NL-201 and anti-mPD-1 demonstrated tumor growth inhibition and increased median survival (21 days each vs 17 days as observed in control) when given alone. In combination, NL-201 and anti-mPD-1 resulted in increased antitumor activity and significant prolongation of survival (>51 days). We have also demonstrated that NL-201 does not directly induce signaling or cell death in B cell−derived NHL, suggesting that the observed antitumor activity is due to activation of non-malignant host immune cells.Additional in vitro and in vivo NHL models are being tested to enhance understanding of the interaction between NL-201 and other approved therapies within the hematopoietic tumor microenvironment. These data will be used to design future clinical trials of NL-201 in novel regimens to treat hematological malignancies. DisclosuresHuard: Neoleukin Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company, Patents & Royalties. Tatalick: Neoleukin Therapeutics, Inc.: Consultancy, Current equity holder in publicly-traded company, Other: Independent paid nonclinical consultant for Neoleukin. Walkey: Neoleukin Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company, Current holder of stock options in a privately-held company. Swanson: Neoleukin Therapeutics, Inc.: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties.

Multi-Modal Targeting of FLT3 with Chimeric Antigen Receptor T Cell Immunotherapy and Tyrosine Kinase Inhibition in High-Risk Pediatric Leukemias

Background:Clinical outcomes for children with FLT3-mutant AML and infants with KMT2A-rearranged (KMT2A-R) B-ALL remain dismal. These leukemias share a common feature of aberrant activation of FLT3 kinase signaling, which occurs by activating FLT3 mutations in AML and by overexpression of wild-type FLT3 in KMT2A-R ALL. Several FLT3 tyrosine kinase inhibitors (FLT3i) are approved for adults with FLT3-mutant AML, but potential efficacy against KMT2A-R ALL remains incompletely characterized and may differ from responses in AML. We previously developed and preclinically validated chimeric antigen receptor (CAR) T cells directed against FLT3 (FLT3CART), which importantly showed potent anti-leukemia activity in preclinical models of both childhood FLT3-mutant AML and infant KMT2A-R ALL (Chien CD et al. ASH 2016). In the current studies, we hypothesized that combinatorial targeting of these two high-risk leukemia subtypes with FLT3CART and the selective next-generation FLT3i gilteritinib would have superior activity and potentially mitigate therapeutic resistance now known to occur with kinase inhibitors or CAR T cell immunotherapy.Methods and Results:We first assessed in vitro sensitivity of human FLT3-mutant AML and KMT2A-R ALL cell lines to gilteritinib, a second-generation selective FLT3i with established clinical activity in FLT3-mutant AML and unknown activity in KMT2A-R ALL. As detrimental effects of kinase inhibitors (e.g., dasatinib, ruxolitinib) upon CAR T cells have been reported, we evaluated for similar effects with gilteritinib co-incubated in vitro with CD3/CD28-bead activated healthy human donor T cells. However, we observed minimal deleterious effects of gilteritinib on normal T cell viability, immunophenotype, and IL-2 and interferon-gamma (IFNg) production. We validated combinatorial effects of gilteritinib and FLT3CART-induced cytotoxicity against FLT3-mutant AML and KMT2A-R ALL cell lines in vitro without impairment of IL-2/IFNg production. We then assessed this dual therapy approach in luciferase+ FLT3-mutant AML (MOLM14) and KMT2A-R ALL (SEM) cell line murine xenograft models. As predicted, both FLT3CART and gilteritinib monotherapies transiently inhibited in vivo leukemia proliferation, although leukemia progression eventually occurred. Conversely, FLT3CART and gilteritinib combination therapy strikingly induced enhanced and sustained leukemia clearance in all assessed AML and ALL cell line xenograft models (Figure 1). Confirmatory studies in our established childhood FLT3-mutant AML and KMT2A-R ALL patient-derived xenograft (PDX) models have also demonstrated potent anti-leukemia efficacy of combined FLT3CART and gilteritinib therapy.Earlier-generation FLT3i have been reported to increase cell surface FLT3 expression on FLT3-mutant AML cells. Given the known importance of target antigen site density for CAR T cell efficacy, we reasoned that a sequential approach to dual therapy with FLT3i ‘priming’ followed by FLT3CART may be superior to a simultaneous treatment strategy. In vitro studies with leukemia cell lines and in vivo studies with PDX models indeed confirmed gilteritinib-induced increases in FLT3 surface antigen density in FLT3-mutant AML cells. Intriguingly, we observed contrasting effects in KMT2A-R ALL cell lines and PDX with decreased surface FLT3 expression upon gilteritinib exposure. Ongoing studies are currently validating gilteritinib priming for FLT3CART given these initial data suggesting potentially divergent sequencing approaches in FLT3-mutant AML versus KMT2A-R ALL.Conclusions:Taken together, our preclinical studies demonstrate that dual targeting with FLT3CART immunotherapy and gilteritinib is a promising therapeutic strategy in FLT3-mutant AML and, importantly, also in KMT2A-R ALL. Notably, we also report minimal negative effects of gilteritinib on FLT3CART, suggesting that FLT3i may be used to enhance CAR T cell immunotherapy without inhibiting T cell function. Phase 1 clinical trials of FLT3CART will open soon for adults and children with FLT3-mutant AML and/or KMT2A-R ALL. [Display omitted] DisclosuresFry: Sana Biotechnology: Current Employment, Current equity holder in publicly-traded company; ElevateBio: Research Funding. Tasian: Kura Oncology: Consultancy; Aleta Biotherapeutics: Consultancy; Gilead Sciences: Research Funding; Incyte Corporation: Research Funding.

Co-Expression of an shRNA Targeting MICA/Micb Improves the Clinical Activity of a NKG2D-Based CAR T in Patients with Relapsed / Refractory AML/MDS

While CAR T cell therapy has delivered impressive clinical efficacy in B cell malignancies, similar levels of clinical activity have not been demonstrated in acute myeloid leukemia (AML). One underlying reason for this lack of translation is the relative paucity of validated CAR T targets. Major Histocompatibility Complex Class 1 related proteins MICA and MICB along with the UL16 binding proteins 1-6 (ULBP1-6) are frequently over-expressed on AML and myelodysplastic syndrome (MDS) blasts. The Natural Killer Group 2D (NKG2D) is a single receptor able to bind MICA, MICB and ULBP1-6, thus providing a potentially powerful approach that could be exploited to target this family of targets thereby providing a novel CAR T approach for AML/MDS.Expressing the NKG2D receptor fused to the human CD3z cytoplasmic domain generates a CAR that, when expressed in primary T cells, generates a CAR T product (termed CYAD-01) that showed good anti-tumor activity in preclinical models. In clinical trials, CYAD-01 showed a good tolerability profile but with a disappointing level of clinical activity when combined with cyclophosphamide / fludarabine preconditioning (DEPLETHINK trial, NCT03466320).We hypothesised that the transient expression of MICA/MICB on the CAR T itself may inhibit the activity of the NKG2D CAR through self-targeting and consequent fratricide. We developed a single shRNA able to knockdown both MICA and MICB. Co-expression of this shRNA with the NKG2D CAR generated a second generation CAR T product termed CYAD-02 which was examined in a highly similar AML/MDS patient population and preconditioning regimen as employed in the DEPLETHINK trial.CYAD-02 was evaluated in the the first-in-human CYCLE-1 trial (NCT04167696) in patients with r/r AML/MDS. The dose-escalation phase evaluated three dose-levels (DL) (1x10 8, 3x10 8 and 1x10 9 total cells per infusion), administered as a single infusion after standard preconditioning chemotherapy (cyclophosphamide 300 mg/m²/day and fludarabine 30 mg/m²/day, daily for 3 days) according to a classic 3+3 design.As of July 2021, 11 patients have been treated with CYAD-02 at the different dose-levels (3 at each DL1 and 2 and 5 at DL3). In terms of safety and tolerability, there was no evidence of a differential safety profile of CYAD-02 within the CYCLE-1 trial as compared to that observed in the CYAD-01 clinical trial. Of note, five patients enrolled in all 3 DLs experienced Grade ≥ 3 adverse events (AE) at least possibly related to CYAD-02 (cytokine release syndrome, febrile neutropenia, white blood cell count decreased, infusion related reaction).With respect to clinical activity, seven patients in total achieved stable disease (2 at DL1, 3 at DL2 and 2 at DL3) with 4 demonstrating evidence of transient blast reduction or anti-leukemic activity (decrease of at least 50% of the bone marrow blasts). In addition, two MDS patients at DL3 achieved a marrow complete response. Overall, this suggests dose dependent response to CYAD-02. Furthermore, patients receiving CYAD-02 cells seem to display a greater duration of response and stronger blast reduction as compared to patients who received CYAD-01 in DEPLETHINK.Interestingly, peak engraftment levels were higher for CYAD-02 compared to CYAD-01 at the same dose (DEPLETHINK trial). At DL3, CYAD-02 cells could be readily detected in peripheral blood of 4/5 patients through month 2. In addition, and unlike what is reported in B cell CAR T-cells trials, there was very limited evidence of elevated homeostatic cytokines (IL-7/IL-15) following CyFlu administration with IL-15 not detected in any of the patients and IL-7 showing only a minor increase in 2 patients.The knockdown of MICA/MICB appears to have a positive contribution to the initial clinical activity of CYAD-02 as compared to that achieved with the first generation CYAD-01 CAR T, together with good safety and tolerability. The lack of homeostatic cytokines after preconditioning, likely limiting the engraftment and activity of CAR T cells, may be related to the biology of myeloid malignancies. One approach to further drive the potency of NKG2D-based CAR T cells would likely be armoring the CAR T through using the T cell as a vehicle to secrete cytokines alongside the CAR. Overall, shRNA knockdown technology provides a means to modify CAR T function and here shows that single shRNA can target two independent genes to enhance the phenotype of the CAR Ts. DisclosuresDeeren: Alexion: Consultancy; BMS: Consultancy; Incyte: Consultancy; Novartis: Consultancy; Sanofi: Consultancy, Research Funding; Sobi: Consultancy; Takeda: Consultancy. Lin: AbbVie, Aptevo Therapeutics, Astellas Pharma, Bio-Path Holdings, Celgene, Celyad, Genentech-Roche, Gilead Sciences, Incyte, Jazz Pharmaceuticals, Novartis, Ono Pharmaceutical, Pfizer, Prescient Therapeutics, Seattle Genetics, Tolero, Trovagene: Research Funding. Alcantar-Orozco: Celyad Oncology: Current Employment. Dheur: Celyad Oncology: Current Employment. Breman: Celyad Oncology: Current Employment. Braun: Celyad Oncology: Current Employment. Lonez: Celyad Oncology: Current Employment. Gilham: Celyad Oncology: Current Employment. Flament: Celyad Oncology: Current Employment. Lehmann: Celyad Oncology: Current Employment.

Nx-5948, a Selective Degrader of BTK with Activity in Preclinical Models of Hematologic and Brain Malignancies

Bruton's tyrosine kinase (BTK) plays a key role in cell survival in B cell malignancies, and covalent inhibitors of BTK, such as ibrutinib and acalabrutinib, have proven efficacious in chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL), marginal zone lymphoma (MZL), and Waldenstrom's macroglobulinemia (WM). BTK inhibitors have also demonstrated clinical activity in small trials of patients with relapsed/refractory primary central nervous system lymphoma. The long-term efficacy of BTK inhibitors is limited by the emergence of resistance mutations, most commonly at C481 of BTK. These mutations preclude formation of a covalent bond with BTK and lead to diminished efficacy and disease progression. Several noncovalent BTK inhibitors, which do not require covalent binding to C481, are currently being investigated in clinical trials as potential therapies for patients with relapsed and refractory disease. However, other mutations have been shown to decrease the in vitro activity of these non-covalent BTK inhibitors, suggesting that mutations may ultimately limit the effectiveness of these compounds as well.Small molecule-induced protein degradation offers a unique approach to target BTK for the treatment of B-cell malignancies. Chimeric Targeting Molecules (CTMs) catalyze ubiquitylation and proteasomal degradation of target proteins and are comprised of a target binding element (“hook”), a linker, and ubiquitin ligase binding element (“harness”). NX-5948 is a CTM that contains a BTK hook linked to a cereblon (CRBN) harness. While some CRBN-binding drugs, such as lenalidomide and pomalidomide, promote the degradation of neo-substrate proteins, such as the transcription factors Aiolos and Ikaros, NX-5948 has been engineered to avoid Aiolos and Ikaros degradation and therefore does not possess IMiD activity.Preclinical studies have shown that NX-5948 catalyzes the degradation of 50% of cellular BTK (DC 50) at < 1 nM concentrations in lymphoma cell lines and peripheral blood mononuclear cells (PBMCs). NX-5948 impairs viability in the BTK-dependent ABC-DLBCL cell line, TMD8 (EC 50: < 10 nM after 72 hours). Importantly, NX-5948 induces degradation of the mutated BTK-C481S in cells and inhibits proliferation of BTK-C481S mutant TMD8 cells more effectively than ibrutinib (NX-5948 EC 50 values of < 10 nM versus > 1 μM for ibrutinib). NX-5948 also catalyzes selective degradation of BTK. In an unbiased proteomics experiment, NX-5948 treatment of TMD8 cells demonstrates robust BTK degradation without significant downregulation of other off-target proteins.Oral administration of NX-5948 in mice leads to dose-proportional exposure in plasma and BTK degradation to <10% of baseline levels in circulating and splenic B cells. In a TMD8 xenograft model in mice containing the BTK-C481S mutation, daily oral administration of NX-5948 resulted in superior tumor growth inhibition (TGI) as compared to ibrutinib. Following a single oral dose of NX-5948 in cynomolgus monkeys, BTK degradation to <10% of baseline levels is observed in the circulating B cells.In addition, NX-5948 penetrates the central nervous system (CNS) and demonstrates activity in a model of brain malignancies. Following oral dosing of NX-5948 to mice, NX-5948 was detectable in the cerebrospinal fluid at a comparable level to the unbound concentration of NX-5948 in mouse plasma. In an intracranial TMD8 xenograft model, treatment with NX-5948 resulted in degradation of BTK in intracranial TMD8 cells, decreased intracranial tumor burden and improved survival relative to treatment with vehicle.The potent BTK degradation activity of NX-5948 and the ability of this molecule to penetrate the CNS supports its development for the treatment of B-cell malignancies, including CNS lymphoma. DisclosuresRobbins: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Noviski: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Rountree: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Tan: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Brathaban: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Ingallinera: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Karr: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Kelly: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Konst: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Ma: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Tenn-McClellan: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. McKinnell: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Perez: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Guiducci: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Hansen: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company. Sands: Nurix Therapeutics: Current Employment, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees.

SY5609, a Potent and Selective CDK7 Inhibitor, Potentiates BTK Inhibitor Activity in Mantle Cell Lymphoma Preclinical Models

Introduction: CDK7 is a key regulator of transcription and cell cycle progression and has been implicated in multiple tumor types driven by aberrant transcriptional (e.g., MYC-, ESR1-activation) and/or aberrant cell cycle control (e.g., loss of RB pathway checkpoint function) mechanisms. SY-5609 is a potent and selective CDK7 inhibitor currently in development in patients with solid tumors (NCT04247126). To assess the potential for SY-5609 development in heme malignancies, we evaluated SY-5609 activity in preclinical models of mantle cell lymphoma (MCL). MCL is an aggressive B cell lymphoma driven by genetic alterations in RB pathway genes (e.g. CCND1, RB1, CDKN2A) and by hyper-activation of B-cell receptor (BCR) signaling leading to activation of NF-kB-dependent transcriptional programs that drive cell proliferation and survival. Our results support evaluation of SY-5609 in MCL patients and highlight the potential for combining SY-5609 with Bruton's Tyrosine Kinase (BTK) inhibitors, inhibitors of BCR signal transduction approved for treatment of MCL.Methods: SY-5609 in vitro antiproliferative activity was assessed in a panel of 7 MCL cell lines by evaluating growth rate inhibition (GR) curve metrics GR 50 (drug concentration at which growth rate is inhibited by 50%) and GR max (maximum depth of response) after 5-days of treatment. SY-5609 pharmacodynamic (PD) responses and combination activity with the BTK inhibitor acalabrutinib were further assessed in MCL cell line Mino-1. PD activity was assessed by measuring transcriptional changes in POLR2A using a NanoString-based PD assay from the SY-5609 solid tumor trial. Combination activity in vitro was assessed by comparing GR curve metrics between acalabrutinib, SY-5609, and acalabrutinib in combination with SY-5609. Expression of CCND1 and E2F1, a key transcriptional regulator of DNA replication commitment and progression, were assayed via western blot. Combination activity in vivo was assessed in mice bearing Mino-1 xenograft tumors by comparing tumor growth rate inhibition (GRI) and body weight change in mice treated with acalabrutinib (15mg/kg, QD) and/or SY-5609 (0.5mg/kg, BID, days 1-7 and 15-21) over 25 days.Results: SY-5609, as a single agent, potently inhibited proliferation of all 7 MCL cell lines tested with a GR 50 geometric-mean of 7 nM (range: 2 to 20 nM) and a GR max geometric-mean of -0.2 (range: -0.6 to 0.2). In MCL cell line Mino-1, SY-5609 induced a dose-dependent increase in POLR2A expression to levels associated with SY-5609 antiproliferative activity in Mino-1 cells in vitro and to levels comparable with those observed in peripheral blood mononuclear cells (PBMCs) collected from SY-5609 solid tumor trial patients. In combination with acalabrutinib, SY-5609 demonstrated synergistic antiproliferative activity in Mino-1 cells in vitro, a dose-dependent decrease in acalabrutinib GR 50 (up to ~2-fold at the highest SY-5609 concentration tested, 5nM), and a dose-dependent increase in GR max (up to ~10-fold). In addition, the combination of SY-5609 and acalabrutinib caused dose-dependent decreases in CCND1 and E2F1 protein expression in vitro, which were not observed with either single agent alone. Finally, in mice bearing Mino-1 xenografts, the combination of SY-5609 and acalabrutinib significantly (p < 0.01) increased tumor GRI relative to each single agent at the doses and regimens tested and was well tolerated (no difference in body weight changes relative to vehicle treated mice).Conclusions: SY-5609 is a potent and selective CDK7 inhibitor that demonstrates antiproliferative activity in MCL cells in vitro, associated with PD changes comparable to those observed in patients enrolled in the SY-5609 solid tumor trial (ENA, 2020). The combination of SY-5609 and acalabrutinib is synergistic in MCL cells in vitro and inhibits expression of key cell cycle regulatory proteins CCND1 and E2F1 at concentrations that are preclinically subtherapeutic for either single agent alone. The combination of SY-5609 and acalabrutinib is also significantly more effective at inhibiting MCL xenograft growth in vivo than either single agent. These results support evaluation of SY-5609, including in combination with BTK inhibitors, in patients with mantle cell lymphoma. DisclosuresJohannessen: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Henry: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Sawant: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. D'Ippolito: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Ke: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Lefkowitz: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Eaton: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Dworakowski: Syros Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Rosario: Syros Pharmaceuticals: Current Employment. Hodgson: Syros Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company.

Combination of Loncastuximab Tesirine and Polatuzumab Vedotin Shows Increased Anti-Tumor Activity in Pre-Clinical Models of Non-Hodgkin Lymphoma

Loncastuximab tesirine-lpyl (formerly ADCT-402) is an antibody-drug conjugate (ADC) comprising a humanised anti-CD19 monoclonal antibody conjugated to the pyrrolobenzodiazepine (PBD) dimer-based payload tesirine. Once bound to CD19 on the cell membrane, loncastuximab tesirine is rapidly internalised and the released PBD dimer warhead causes interstrand DNA crosslinks which ultimately trigger cell death. Pre-clinically, loncastuximab tesirine has shown potent and specific anti-tumor activity in lymphoma models both as single agent and in combination with other approved drugs, like venetoclax, idelalisib and bendamustine (Zammarchi, Corbett et al. 2018, Tarantelli, Spriano et al. 2019). Loncastuximab tesirine has been recently approved by the United States Food and Drug Administration (FDA) for the treatment of relapsed or refractory (r/r) diffuse large B-cell lymphoma (DLBCL) and it is currently being tested in multiple clinical trials, either as monotherapy or in combination with other anti-lymphoma drugs.Polatuzumab vedotin is an ADC composed of a humanized anti-CD79b monoclonal antibody conjugated to monomethyl auristatin E (vcMMAE) and it is approved by the FDA for treatment of r/r DLBCL when used in combination with bendamustine and rituximab.Here, we investigated the in vitro and in vivo anti-tumor activity of loncastuximab tesirine combined with polatuzumab vedotin in pre-clinical models of non-Hodgkin lymphoma (NHL).In vitro, the combination of loncastuximab tesirine and polatuzumab vedotin was tested in three human-derived, CD19 and CD79b-positive NHL cell lines (WSU-DLCL2, TMD8 and Ramos) and it resulted in synergistic (TMD8 and Ramos) and additive (WSU-DLCL2) activity, as assessed by the Chou-Talalay method.Quantification of cell viability (propidium iodide [PI]-negative and Annexin V-negative) and early/late apoptosis (Annexin V-positive and PI-negative/ Annexin V-positive and-PI positive) on TMD8 and Ramos cells treated with loncastuximab tesirine, polatuzumab vedotin or the combination of the two agents showed a significant reduction of viable cells accompanied by an increase in apoptotic cells in the combination setting compared to the single agents.In vivo, loncastuximab tesirine was tested either alone (0.25 or 0.5 mg/kg, single dose) or in combination with polatuzumab vedotin (1 mg/kg, single dose) in the WSU-DLCL2 xenograft model. At the highest dose of loncastuximab tesirine, combination with polatuzumab vedotin resulted in improved anti-tumor activity and superior response rate compared to the 2 agents in monotherapy. All treatment regimens were well tolerated by the mice, as assessed by body weight measurements and frequent observation for signs of treatment-related side effects.In conclusion, the combination of loncastuximab tesirine and polatuzumab vedotin resulted in improved anti-tumor activity both in vitro and in vivo in lymphoma preclinical models and it was well tolerated. Altogether, these novel pre-clinical data warrant translation of the combination of loncastuximab tesirine and polatuzumab vedotin into the clinic for the treatment of NHL. DisclosuresSachini: ADC Therapeutics: Current Employment, Current equity holder in publicly-traded company. Jabeen: ADC Therapeutics: Current Employment, Current equity holder in publicly-traded company. van Berkel: ADC Therapeutics: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Zammarchi: ADC Therapeutics: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties.

279 ILT3 blockade reduces tumor blast cells in acute myeloid leukemia PBMC and inhibits tumor cell growth in a humanized AML tumor model

BackgroundImmunoglobulin-like transcript 3 (ILT3), an immune-inhibitory receptor expressed on myeloid cells, is highly expressed in acute myeloid leukemia (AML) with monocytic differentiation (M4 and M5 subtypes) and clinically is negatively correlated with overall survival. We examined the effects of a highly selective and potent chimeric anti-ILT3 mAb (c52B8) on tumor cell survival/growth and human immune cell modulation in AML PBMC and AML tumor cell lines in pre-clinical in vitro and in vivo models.MethodsILT3 mRNA and cell surface expression levels were measured by RNAseq and FACS, respectively. PBMC from AML patients with different levels of ILT3 cell surface expression were treated with c52B8 in vitro.A systemic AML model was generated by IV inoculation of NSG mice with luciferase-transfected MV-4-11 human AML cells, with or without human PBMC engraftment. Tumor bearing mice were treated weekly with c52B8, modified to contain the human Fc of either the IgG1 or IgG4 subclass. MV-4-11 growth in vivo was measured by bioluminescence imaging (BLI).CyTOF was performed to phenotype AML PBMC in in vitro culture and bone marrow samples from the systemic MV-4-11 model after the treatment.THP-1 cells/human T cell co-cultures stimulated with anti-CD3/CD28 antibodies were treated with c52B8. Human T cell activity was assessed by levels of IFNγ production in the culture using MSD ELISA.ResultsIn ILT3 high AML patient PBMC, c52B8 treatment in vitro decreased the frequency of tumor blasts, modulated Tregs, and increased monocytic myeloid cells. In the MV-4-11 model, weekly treatment with c52B8 significantly reduced tumor burden in vivo, regardless of the IgG subclass. Importantly, tumor cell growth inhibition by c52B8 occurred in the absence of human PBMC. Additional post-mortem CyTOF analysis of bone marrow cells from MV-4-11/human PBMC inoculated mice confirmed a reduction in MV-4-11 cells, identified by CD3-CD19- human myeloid cells following c52B8 treatment. In THP-1/human T cell co-cultures, c52B8 treatment reversed THP-1 induced T cell suppression, as measured by enhanced IFNγ production.ConclusionsAnti-ILT3 mAb (c52B8) is efficacious in blocking progression of AML with monocytic differentiation by directly influencing tumor cell growth and enhancing human T cell activity in pre-clinical models. These studies support a potential role for this compound in humans.Ethics ApprovalAll animal work was reviewed and approved by Merck IACUC before experiments were conducted.

Reversal of Bortezomib-Induced Neurotoxicity by Suvecaltamide, a Selective T-Type Ca-Channel Modulator, in Preclinical Models.

Simple SummaryChemotherapy-induced peripheral neurotoxicity (CIPN) is a side-effect of anti-cancer medications, which can lead to pain, disruptions to movement, and eventually results in the need to interrupt or stop chemotherapy. This study sought to test whether the drug suvecaltamide could help to reduce the impact of the chemotherapy agent bortezomib (BTZ) on symptoms of CIPN using animal models and human cells. Suvecaltamide did reverse negative changes in nerve conduction velocity and intraepidermal nerve fiber density indicative of CIPN in rats, and did not interfere with the anti-cancer effect of BTZ. These results indicate that suvecaltamide could potentially be useful for patients experiencing CIPN, although further mechanistic and molecular studies in vitro and in vivo are required before clinical trials.This study evaluated suvecaltamide, a selective T-type calcium channel modulator, on chemotherapy-induced peripheral neurotoxicity (CIPN) and anti-cancer activity associated with bortezomib (BTZ). Rats received BTZ (0.2 mg/kg thrice weekly) for 4 weeks, then BTZ alone (n = 8) or BTZ+suvecaltamide (3, 10, or 30 mg/kg once daily; each n = 12) for 4 weeks. Nerve conduction velocity (NCV), mechanical threshold, β-tubulin polymerization, and intraepidermal nerve fiber (IENF) density were assessed. Proteasome inhibition was evaluated in peripheral blood mononuclear cells. Cytotoxicity was assessed in human multiple myeloma cell lines (MCLs) exposed to BTZ alone (IC50 concentration), BTZ+suvecaltamide (10, 30, 100, 300, or 1000 nM), suvecaltamide alone, or vehicle. Tumor volume was estimated in athymic nude mice bearing MCL xenografts receiving vehicle, BTZ alone (1 mg/kg twice weekly), or BTZ+suvecaltamide (30 mg/kg once daily) for 28 days, or no treatment (each n = 8). After 4 weeks, suvecaltamide 10 or 30 mg/kg reversed BTZ-induced reduction in NCV, and suvecaltamide 30 mg/kg reversed BTZ-induced reduction in IENF density. Proteasome inhibition and cytotoxicity were similar between BTZ alone and BTZ+suvecaltamide. BTZ alone and BTZ+suvecaltamide reduced tumor volume versus the control (day 18), and BTZ+suvecaltamide reduced tumor volume versus BTZ alone (day 28). Suvecaltamide reversed CIPN without affecting BTZ anti-cancer activity in preclinical models.

Direct AMPK Activation Corrects NASH in Rodents Through Metabolic Effects and Direct Action on Inflammation and Fibrogenesis.

No approved therapies are available for nonalcoholic steatohepatitis (NASH). Adenosine monophosphate–activated protein kinase (AMPK) is a central regulator of cell metabolism; its activation has been suggested as a therapeutic approach to NASH. Here we aimed to fully characterize the potential for direct AMPK activation in preclinical models and to determine mechanisms that could contribute to efficacy for this disease. A novel small‐molecule direct AMPK activator, PXL770, was used. Enzyme activity was measured with recombinant complexes. De novo lipogenesis (DNL) was quantitated in vivo and in mouse and human primary hepatocytes. Metabolic efficacy was assessed in ob/ob and high‐fat diet–fed mice. Liver histology, biochemical measures, and immune cell profiling were assessed in diet‐induced NASH mice. Direct effects on inflammation and fibrogenesis were assessed using primary mouse and human hepatic stellate cells, mouse adipose tissue explants, and human immune cells. PXL770 directly activated AMPK in vitro and reduced DNL in primary hepatocytes. In rodent models with metabolic syndrome, PXL770 improved glycemia, dyslipidemia, and insulin resistance. In mice with NASH, PXL770 reduced hepatic steatosis, ballooning, inflammation, and fibrogenesis. PXL770 exhibited direct inhibitory effects on pro‐inflammatory cytokine production and activation of primary hepatic stellate cells. Conclusion: In rodent models, direct activation of AMPK is sufficient to produce improvements in all core components of NASH and to ameliorate related hyperglycemia, dyslipidemia, and systemic inflammation. Novel properties of direct AMPK activation were also unveiled: improved insulin resistance and direct suppression of inflammation and fibrogenesis. Given effects also documented in human cells (reduced DNL, suppression of inflammation and stellate cell activation), these studies support the potential for direct AMPK activation to effectively treat patients with NASH.

10P DS-6000a, a novel CDH6-targeting antibody-drug conjugate with a novel DNA topoisomerase I inhibitor DXd, demonstrates potent antitumor activity in preclinical models

Human Cadherin 6 (CDH6) is a single transmembrane protein consisting of 790 amino acids classified into the type 2 cadherin family. Human CDH6 is specifically expressed in the brain and kidneys during the development phase and has been reported to systemically decrease CDH6 expression in the adult body. CDH6 expression is increased specifically in renal cell carcinoma (RCC) and ovarian cancer (OVC). Therefore, CDH6 could be an attractive target for cancer therapy. We created DS-6000a, a CDH6-targeting antibody-drug conjugate (ADC) using an enzymatically cleavable tetrapeptide-based linker, and a high drug-to-antibody ratio (DAR 7 to 8) with a novel DNA topoisomerase I inhibitor (DXd).

13P SY-5609, a highly potent and selective oral CDK7 inhibitor, exhibits robust antitumor activity in preclinical models of KRAS mutant cancers as a single agent and in combination with chemotherapy

Mutational KRAS activation drives oncogenic processes including aberrant cell cycle progression. CDK7 inhibition has been shown to target two fundamental processes in cancer: transcription and cell cycle control. SY-5609 is a CDK7 inhibitor in development in patients with solid tumors including pancreatic and lung cancers (NCT04247126). Here we report on SY-5609 preclinical activity in models of KRAS-mutant pancreatic ductal adenocarcinoma (PDAC) and non-small-cell lung cancer (NSCLC).

1554TiP A randomized phase II study to investigate the efficacy and safety of the tumor-targeting human antibody-cytokine fusion protein L19TNF in previously treated patients with advanced or metastatic soft tissue sarcoma

Although tumor necrosis factor (TNF) is one of the most potent antitumor cytokines, its unacceptable toxicities do not allow for systemic administration of therapeutically active doses. L19TNF is a fully human antibody-cytokine fusion protein, composed of the neovascular targeting antibody fragment scFv(L19) fused to human recombinant TNF, that selectively delivers therapeutically relevant doses of TNF to the tumor tissue while sparing normal tissues. L19TNF has demonstrated substantial therapeutic activity in preclinical models of sarcoma when administered alone or in combination with chemotherapy, leading to hemorrhagic tumor necrosis and immune-mediated tumor rejection.

PTG-100, an Oral α4β7 Antagonist Peptide: Preclinical Development and Phase 1 and 2a Studies in Ulcerative Colitis

Oral therapies targeting the integrin α4β7 may offer unique advantages for the treatment of inflammatory bowel disease. We characterized the oral α4β7 antagonist peptide PTG-100 in preclinical models and established safety, pharmacokinetic/pharmacodynamic relationships, and efficacy in a phase 2a trial in patients with ulcerative colitis (UC). Invitro studies measured binding properties of PTG-100. Mouse studies measured biomarkers and drug concentrations in blood and tissues. The phase 1 study involved healthy volunteers. In phase 2a, patients with moderate to severe active UC were randomized to receive PTG-100 (150, 300, or 900 mg) or placebo once daily for 12-weeks. PTG-100 potently and selectively blocks α4β7. Oral dosing of PTG-100 in mice showed high levels of target engagement and exposure in gut-associated lymphoid tissues. In healthy volunteers, PTG-100 showed dose-dependent increases in plasma exposure and blood target engagement. Although this phase 2a study initially did not meet the primary endpoint, a blinded reread of the endoscopy videos by a third party indicated clinical efficacy in conjunction with histologic remission at doses correlating with less than 100% receptor occupancy in peripheral blood. PTG-100 showed local gastrointestinal tissue target engagement and inhibition of memory T-cell trafficking in mice. It was safe and well tolerated in phase 1 and 2 studies. Phase 2a data are consistent with biological and clinical response and showed a dose response reflecting similar activities in preclinical models and healthy individuals. These data suggest that local gut activity of an oral α4β7 integrin antagonist, distinct from full target engagement in blood, are important for efficacy and the treatment of UC. (ClinicalTrials.gov, Number NCT02895100; EudraCT, Number 2016-003452-75).

Cytolytic Activity of CAR T Cells and Maintenance of Their CD4+ Subset Is Critical for Optimal Antitumor Activity in Preclinical Solid Tumor Models.

Simple SummaryAdoptively transferred T cells expressing recombinant chimeric antigen receptors (CAR T cells) have been approved for the therapy of hematological malignancies of the B cell lineage. However, CAR T cell therapy for patients with solid tumors so far has shown limited benefits. Correlative clinical studies of patients with hematological malignancies have suggested that less differentiated CAR T cells have improved anti-leukemic activity. We have therefore investigated the role of differentiation on the anti-tumor activity of CAR T cells targeting the solid tumor antigen HER2 in preclinical models. We utilized different activation/expansion protocols, and explored whether different co-stimulatory domains in the CAR construct influence the short- and long-term efficacy of HER2-CAR T cells. We demonstrate that the CAR T cell product with the highest proportion of effector cells and maintaining a good balance of CD4+/CD8+ cells is the most effective against solid tumors both in vitro and in vivo.Correlative clinical studies of hematological malignancies have implicated that less differentiated, CD8+-dominant CAR T cell products have greater antitumor activity. Here, we have investigated whether the differentiation status of CAR T cell products affects their antitumor activity in preclinical models of solid tumors. We explored if different activation/expansion protocols, as well as different co-stimulatory domains in the CAR construct, influence the short- and long-term efficacy of CAR T cells against HER2-positive tumors. We generated T cell products that range from the most differentiated (CD28.z; OKT3-antiCD28/RPMI expansion) to the least differentiated (41BB.z; OKT3-RetroNectin/LymphoONE expansion), as judged by cell surface expression of the differentiation markers CCR7 and CD45RA. While the effect of differentiation status was variable with regard to antigen-specific cytokine production, the most differentiated CD28.z CAR T cell products, which were enriched in effector memory T cells, had the greatest target-specific cytolytic activity in vitro. These products also had a greater proliferative capacity and maintained CD4+ T cells upon repeated stimulation in vitro. In vivo, differentiated CD28.z CAR T cells also had the greatest antitumor activity, resulting in complete response. Our results highlight that it is critical to optimize CAR T cell production and that optimal product characteristics might depend on the targeted antigen and/or cancer.

Selective Inhibition of the Second Bromodomain of BET Family Proteins Results in Robust Antitumor Activity in Preclinical Models of Acute Myeloid Leukemia.

Dual bromodomain BET inhibitors that bind with similar affinities to the first and second bromodomains across BRD2, BRD3, BRD4, and BRDT have displayed modest activity as monotherapy in clinical trials. Thrombocytopenia, closely followed by symptoms characteristic of gastrointestinal toxicity, have presented as dose-limiting adverse events that may have prevented escalation to higher dose levels required for more robust efficacy. ABBV-744 is a highly selective inhibitor for the second bromodomain of the four BET family proteins. In contrast to the broad antiproliferative activities observed with dual bromodomain BET inhibitors, ABBV-744 displayed significant antiproliferative activities largely although not exclusively in cancer cell lines derived from acute myeloid leukemia and androgen receptor positive prostate cancer. Studies in acute myeloid leukemia xenograft models demonstrated antitumor efficacy for ABBV-744 that was comparable with the pan-BET inhibitor ABBV-075 but with an improved therapeutic index. Enhanced antitumor efficacy was also observed with the combination of ABBV-744 and the BCL-2 inhibitor, venetoclax compared with monotherapies of either agent alone. These results collectively support the clinical evaluation of ABBV-744 in AML (Clinical Trials.gov identifier: NCT03360006).

Anti-tumor effects of RTX-240: an engineered red blood cell expressing 4-1BB ligand and interleukin-15

Recombinant agonists that activate co-stimulatory and cytokine receptors have shown limited clinical anticancer utility, potentially due to narrow therapeutic windows, the need for coordinated activation of co-stimulatory and cytokine pathways and the failure of agonistic antibodies to recapitulate signaling by endogenous ligands. RTX-240 is a genetically engineered red blood cell expressing 4-1BBL and IL-15/IL-15Rα fusion (IL-15TP). RTX-240 is designed to potently and simultaneously stimulate the 4-1BB and IL-15 pathways, thereby activating and expanding T cells and NK cells, while potentially offering an improved safety profile through restricted biodistribution. We assessed the ability of RTX-240 to expand and activate T cells and NK cells and evaluated the in vivo efficacy, pharmacodynamics and tolerability using murine models. Treatment of PBMCs with RTX-240 induced T cell and NK cell activation and proliferation. In vivo studies using mRBC-240, a mouse surrogate for RTX-240, revealed biodistribution predominantly to the red pulp of the spleen, leading to CD8 + T cell and NK cell expansion. mRBC-240 was efficacious in a B16-F10 melanoma model and led to increased NK cell infiltration into the lungs. mRBC-240 significantly inhibited CT26 tumor growth, in association with an increase in tumor-infiltrating proliferating and cytotoxic CD8 + T cells. mRBC-240 was tolerated and showed no evidence of hepatic injury at the highest feasible dose, compared with a 4-1BB agonistic antibody. RTX-240 promotes T cell and NK cell activity in preclinical models and shows efficacy and an improved safety profile. Based on these data, RTX-240 is now being evaluated in a clinical trial.