Discovery of 1'-(1-phenylcyclopropane-carbonyl)-3H-spiro[isobenzofuran-1,3'-pyrrolidin]-3-one as a novel steroid mimetic scaffold for the potent and tissue-specific inhibition of 11β-HSD1 using a scaffold-hopping approach

11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) has been identified as the primary enzyme responsible for the activation of hepatic cortisone to cortisol in specific peripheral tissues resulting in the concomitant antagonism of insulin action within these tissues. Dysregulation of 11β-HSD1, particularly in adipose tissues, has been associated with metabolic syndrome and type 2 diabetes mellitus. Therefore, inhibition of 11β-HSD1 with a small nonsteroidal molecule is therapeutically desirable. Implementation of a scaffold-hopping approach revealed a three-point pharmacophore for 11β-HSD1 that was utilized to design a steroid mimetic scaffold. Reiterative optimization provided valuable insight into the bioactive conformation of our novel scaffold and led to the discovery of INCB13739. Clinical evaluation of INCB13739 confirmed for the first time that tissue-specific inhibition of 11β-HSD1 in patients with type 2 diabetes mellitus was efficacious in controlling glucose levels and reducing cardiovascular risk factors.

Discovery of a novel 2-spiroproline steroid mimetic scaffold for the potent inhibition of 11β-HSD1

11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) has been identified as the primary enzyme responsible for the activation of hepatic cortisone to cortisol in specific peripheral tissues, resulting in the concomitant antagonism of insulin action within these tissues. Dysregulation of 11β-HSD1, particularly in adipose tissues, has been associated with a variety of ailments including metabolic syndrome and type 2 diabetes mellitus. Therefore, inhibition of 11β-HSD1 with a small nonsteroidal molecule is therapeutically desirable. Implementation of a scaffold-hopping approach revealed a 3-point pharmacophore for 11β-HSD1 that was utilized to design a 2-spiroproline derivative as a steroid mimetic scaffold. Reiterative optimization provided valuable insight into the bioactive conformation of our novel scaffold and led to the discovery of several leads, such as compounds 39 and 51. Importantly, deleterious hERG inhibition and pregnane X receptor induction were mitigated by the introduction of a 4-hydroxyl group to the proline ring system.

Characterization of INCB086550: A Potent and Novel Small-Molecule PD-L1 Inhibitor

Blocking the activity of the programmed cell death protein 1 (PD-1) inhibitory receptor with therapeutic antibodies against either the ligand (PD-L1) or PD-1 itself has proven to be an effective treatment modality for multiple cancers. Contrasting with antibodies, small molecules could demonstrate increased tissue penetration, distinct pharmacology, and potentially enhanced antitumor activity. Here, we describe the identification and characterization of INCB086550, a novel, oral, small-molecule PD-L1 inhibitor. In vitro, INCB086550 selectively and potently blocked the PD-L1/PD-1 interaction, induced PD-L1 dimerization and internalization, and induced stimulation-dependent cytokine production in primary human immune cells. In vivo, INCB086550 reduced tumor growth in CD34+ humanized mice and induced T-cell activation gene signatures, consistent with PD-L1/PD-1 pathway blockade. Preliminary data from an ongoing phase I study confirmed PD-L1/PD-1 blockade in peripheral blood cells, with increased immune activation and tumor growth control. These data support continued clinical evaluation of INCB086550 as an alternative to antibody-based therapies.

SIGNIFICANCE

We have identified a potent small-molecule inhibitor of PD-L1, INCB086550, which has biological properties similar to PD-L1/PD-1 monoclonal antibodies and may represent an alternative to antibody therapy. Preliminary clinical data in patients demonstrated increased immune activation and tumor growth control, which support continued clinical evaluation of this approach. See related commentary by Capparelli and Aplin, p. 1413. This article is highlighted in the In This Issue feature, p. 1397.

A human CD137×PD-L1 bispecific antibody promotes anti-tumor immunity via context-dependent T cell costimulation and checkpoint blockade

Immune checkpoint inhibitors demonstrate clinical activity in many tumor types, however, only a fraction of patients benefit. Combining CD137 agonists with these inhibitors increases anti-tumor activity preclinically, but attempts to translate these observations to the clinic have been hampered by systemic toxicity. Here we describe a human CD137xPD-L1 bispecific antibody, MCLA-145, identified through functional screening of agonist- and immune checkpoint inhibitor arm combinations. MCLA-145 potently activates T cells at sub-nanomolar concentrations, even under suppressive conditions, and enhances T cell priming, differentiation and memory recall responses. In vivo, MCLA-145 anti-tumor activity is superior to immune checkpoint inhibitor comparators and linked to recruitment and intra-tumor expansion of CD8 + T cells. No graft-versus-host-disease is observed in contrast to other antibodies inhibiting the PD-1 and PD-L1 pathway. Non-human primates treated with 100 mg/kg/week of MCLA-145 show no adverse effects. The conditional activation of CD137 signaling by MCLA-145, triggered by neighboring cells expressing >5000 copies of PD-L1, may provide both safety and potency advantages.

Discovery of Pemigatinib: A Potent and Selective Fibroblast Growth Factor Receptor (FGFR) Inhibitor

Aberrant activation of FGFR has been linked to the pathogenesis of many tumor types. Selective inhibition of FGFR has emerged as a promising approach for cancer treatment. Herein, we describe the discovery of compound 38 (INCB054828, pemigatinib), a highly potent and selective inhibitor of FGFR1, FGFR2, and FGFR3 with excellent physiochemical properties and pharmacokinetic profiles. Pemigatinib has received accelerated approval from the U.S. Food and Drug Administration for the treatment of adults with previously treated, unresectable locally advanced or metastatic cholangiocarcinoma with a FGFR2 fusion or other rearrangement. Additional clinical trials are ongoing to evaluate pemigatinib in patients with FGFR alterations.

INCB054828 (pemigatinib), a potent and selective inhibitor of fibroblast growth factor receptors 1, 2, and 3, displays activity against genetically defined tumor models

Alterations in fibroblast growth factor receptor (FGFR) genes have been identified as potential driver oncogenes. Pharmacological targeting of FGFRs may therefore provide therapeutic benefit to selected cancer patients, and proof-of-concept has been established in early clinical trials of FGFR inhibitors. Here, we present the molecular structure and preclinical characterization of INCB054828 (pemigatinib), a novel, selective inhibitor of FGFR 1, 2, and 3, currently in phase 2 clinical trials. INCB054828 pharmacokinetics and pharmacodynamics were investigated using cell lines and tumor models, and the antitumor effect of oral INCB054828 was investigated using xenograft tumor models with genetic alterations in FGFR1, 2, or 3. Enzymatic assays with recombinant human FGFR kinases showed potent inhibition of FGFR1, 2, and 3 by INCB054828 (half maximal inhibitory concentration [IC₅₀] 0.4, 0.5, and 1.0 nM, respectively) with weaker activity against FGFR4 (IC₅₀ 30 nM). INCB054828 selectively inhibited growth of tumor cell lines with activation of FGFR signaling compared with cell lines lacking FGFR aberrations. The preclinical pharmacokinetic profile suggests target inhibition is achievable by INCB054828 in vivo with low oral doses. INCB054828 suppressed the growth of xenografted tumor models with FGFR1, 2, or 3 alterations as monotherapy, and the combination of INCB054828 with cisplatin provided significant benefit over either single agent, with an acceptable tolerability. The preclinical data presented for INCB054828, together with preliminary clinical observations, support continued investigation in patients with FGFR alterations, such as fusions and activating mutations.

Abstract 541: An unbiased screen identifies a CD137xPD-L1 bispecific IgG1 antibody with unique T cell activation and binding properties

CD137 (4-1BB) is a transmembrane costimulatory receptor on T and NK cells that enhances adaptive immune responses and is a critical mediator of antitumor immunity. CD137 signaling requires receptor clustering normally facilitated by the trimeric CD137 ligand (CD137L). Alternatively, CD137 signaling can be triggered either directly by agonistic monoclonal antibodies (mAbs) or indirectly via crosslinking of CD137 binding mAbs by Fcγ receptors on neighboring cells. The development of CD137 targeted agents for cancer therapy has been hampered by on-target off-tumor toxicity in the case of agonist, monospecific, bivalent mAbs or limited antitumor activity in the case of crosslinking mAbs. To address the issues of toxicity and efficacy a highly selective and potent CD137xPD-L1 bispecific antibody (bAb) was identified by applying an unbiased functional screening approach. Collections of common light chain Fabs recognizing CD137 and PD-L1 were produced based on antibody panels from immunized MeMo® mice. A large and diverse panel of CD137xPD-L1 bAbs was then produced by combining different CD137 and PD-L1 Fabs based on epitope and sequence diversity in the IgG1 Biclonics® format. The bAbs were screened for activity in reporter cell lines expressing the receptors. This unbiased combinatorial screening identified a CD137xPD-L1 bAb (MCLA-145) for which CD137 mediated activation is dependent on the presence of PD-L1 on a neighboring cell and, as such, the antibody acts in ‘trans’. Flow cytometry experiments demonstrated that MCLA-145 is fully cross-reactive to cynomolgus monkey CD137 and PD-L1. The CD137 Fab arm blocks the interaction of CD137 with CD137L as demonstrated in a competition assay by flow cytometry. The PD-L1 Fab arm blocks the interaction between PD-1 and PD-L1 as demonstrated in ELISA. Binding epitopes were mapped by shotgun mutagenesis using a flow-based screen. In addition, hydrogen-deuterium exchange experiments were performed to map the binding domain on CD137. Data show that MCLA-145 binds the ligand binding domain of CD137 domain (CRDII). The PD-L1 Fab arm binds PD-L1 in the PD-1 binding N-terminal V domain. Both epitope mapping data sets are consistent with the CD137 and PD-L1 ligand blocking activity of MCLA-145. Monovalent binding affinities were measured by surface plasma resonance (SPR) and radioactive iodine labeling and demonstrated affinities in the low nM (CD137) and subnanomolar (PD-L1) range. SPR experiments also confirmed that MCLA-145 was able to bind simultaneously to both CD137 and PD-L1 recombinant proteins. The unique binding properties of MCLA-145 may result in an increased therapeutic window by specifically activating CD137 expressing cells in the tumor niche where PD-L1 is expressed while simultaneously blocking inhibitory input from the PD-1/PD-L1 axis.

Citation Format: Cecile A. Geuijen, Paul Tacken, Rinse Klooster, Horacio Nastri, Shaun Stewart, Jing Zhou, Steve Wang, Cheng-Yen Huang, Arjen Kramer, Linda Kaldenberg-Hendriks, John de Kruif, Renate den Blanken-Smit, Vanessa Zondag-van de Zande, Abdul Basmeleh, Willem Bartelink, Patrick Mayes, Gregory Hollis, Reid Huber, Mark Throsby. An unbiased screen identifies a CD137xPD-L1 bispecific IgG1 antibody with unique T cell activation and binding properties [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 541.

Abstract 4480: Preclinical characterization of potent and selective oral PD-L1 small-molecule antagonists

Monoclonal antibodies against PD-L1 or PD-1 have been approved for the treatment of multiple tumor histologies by virtue of their ability to restore T cell effector function, increase T cell proliferation and enhance infiltration of tumor-reactive T cells. A small molecule approach to PD-(L)1 axis blockade may offer distinct benefits over the use of monoclonal antibodies including improved tissue penetration, titratability, absence of immunogenicity, ease of administration, and potential for fixed dose oral-oral therapeutic combinations. We have identified a novel class of small molecule PD-L1 antagonists that are capable of functional PD-(L)1 axis blockade by virtue of their ability to induce PD-L1 internalization. In vitro, select small molecules demonstrate high affinity to human PD-L1, potently disrupt the PD-L1:PD-1 interaction (<4nM), and inhibit Src homology region 2 domain-containing phosphatase (SHP2) recruitment to PD-1 (<10nM). As a result, PD-1-mediated suppression of nuclear factor of activated T cells (NFAT) activation is reduced and IFNγ production by T cells is restored. These bioactive small molecule PD-L1 antagonists are shown to reduce surface PD-L1 levels in tumor cells and peripheral blood monocytes with IC50s ranging from 1-250nM, providing an in vivopharmacodynamic biomarker for compound activity. Using humanized NSG mice bearing MDA-MB-231 tumors, oral administration of small molecule PD-L1 antagonists for 28 days demonstrated a dose-dependent reduction in tumor growth with a concomitant and dose-dependent increase in the number of tumor-infiltrating T cells. These data were concordant with the dose-dependent reduction of surface PD-L1 levels seen on both tumor cells and tumor associated macrophages at the end of the study. Similar data, including dose-dependent tumor growth inhibition, PD-L1 internalization and increase in tumor-infiltrating T cells, were also obtained using a murine MC38 xenograft system genetically engineered to over express human PD-L1. No in vivo activity was observed when tumors were treated in immunocompromised mice, confirming the pharmacologic dependency on a competent immune system. Finally, these oral PD-L1 small molecule antagonists demonstrated equivalent anti-tumor activity in preclinical tumor models when compared head-to-head to clinically approved PD-(L)1 axis targeting monoclonal antibodies. In conclusion, effective PD-(L)1 axis blockade and functional activation of the immune system can be achieved in vivo through this novel series of orally bioavailable small molecule PD-L1 antagonists, supporting the clinical evaluation of the mechanism as a novel approach to immune therapy.

Citation Format: Liang-Chuan S. Wang, Holly Koblish, Yue Zhang, Ashwini Kulkarni, Maryanne Covington, Karen Gallagher, Gengjie Yang, Jonathan Rios-Doria, Christina Stevens, Michael Hansbury, Sybil O'Connor, Yan-ou Yang, Sharon Diamond, Krista Burke, Kaijiong Xiao, Jingwei Li, Wenqing Yao, Liangxing Wu, Peggy Scherle, Gregory Hollis, Reid Huber. Preclinical characterization of potent and selective oral PD-L1 small-molecule antagonists [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4480.

Abstract 4483: Novel small-molecule antagonists of the PD-1/PD-L1 axis that mediate cell surface PD-L1 dimerization and internalization

Blocking the PD-(L)1 immune checkpoint axis with therapeutic antibodies against either the receptor or the ligand has proven to be an effective treatment modality for multiple cancer histologies. We describe the identification and characterization of novel small molecule antagonists of the PD-(L)1 axis that function by inducing dimerization and subsequent internalization of the PD-L1 protein, effectively depleting the ligand from the cell membrane and preventing PD-1 activation on T cells. Compound-dependent PD-L1 dimerization was characterized using several biophysical techniques including fluorescence resonance energy transfer (FRET) measurements, size exclusion chromatography and thermal shift analysis. Experimental evidence demonstrates compound-dependent dimer conformation with slow dissociation kinetics and significantly enhanced thermal stability. Many of the PD-L1-directed small molecules blocked binding of soluble PD-1 to either native PD-L1 expressed on cancer cell lines or PD-L1 expressed in CHO cells with low nanomolar potency. However, only a subset of the small molecules caused loss of cell surface PD-L1 in a time- and concentration-dependent manner. Importantly, there was a strict correlation between the promotion of PD-L1 internalization secondary to dimerization and the induction of an NFAT response element-luciferase reporter gene. Strikingly, only those small molecules that could produce a specific dimeric PD-L1 conformation as measured using FRET were associated with functional activity in cells, suggesting that PD-L1 dimerization was necessary but not sufficient for internalization and cellular activity. A cell-active tool compound (cell binding IC50 <5 nM, internalization EC50 <10 nM) was fluorescently labeled to enable direct visualization of intracellular trafficking. Confocal microscopy with this PD-L1 antagonist showed time-dependent increases in intracellular fluorescence in PD-L1 expressing, but not PD-L1 deleted, cells. The internalized antagonist showed punctate staining coincident with markers of the early endosome, and independent studies confirmed that the internalized PD-L1 also trafficked to the early endosome. By disrupting the suppressive activity of PD-L1 on PD-1, these inhibitors result in functional activation of T cells in ex vivo cellular assays in a manner equivalent to antibodies directed against either PD-1 or PD-L1. In summary, we have identified a series of potent, small molecule PD-L1 antagonists that induce dimerization of the protein; inhibitors that trigger an appropriate dimeric conformation can also induce PD-L1 internalization thereby alleviating PD-L1-induced suppression of T cell activation.

Citation Format: Phillip C.C. Liu, Richard Wynn, Liangxing Wu, Alla Volgina, Nina Zolotarjova, Luping Lin, Pramod Thekkat, Alex Margulis, Ronald Klabe, Wenqing Yao, Kaijiong Xiao, Jingwei Li, Xin He, Mark Rupar, Hong Chang, Paul Waeltz, Yanlong Li, Peggy Scherle, Reid Huber, Gregory Hollis. Novel small-molecule antagonists of the PD-1/PD-L1 axis that mediate cell surface PD-L1 dimerization and internalization [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4483.

Abstract 539: A bispecific Fc-silenced IgG1 antibody (MCLA-145) requires PD-L1 binding to activate CD137

CD137 (4-1BB) is a transmembrane costimulatory receptor on T and NK cells that enhances adaptive immune responses and is a critical mediator of antitumor immunity. The development of CD137 targeted agents for cancer therapy has been hampered by on-target off-tumor toxicity in the case of agonist monospecific, bivalent mAbs or limited antitumor activity in the case of crosslinking mAbs. Here we have developed an Fc-silenced bispecific IgG1 antibody to CD137 and PD-L1 with monovalent binding specificity to each target. MCLA-145 drives transactivation of CD137 in the vicinity of cells expressing PD-L1, such as in the immunosuppressive tumor microenvironment. The degree of CD137 agonistic activity in T cells correlated with the expression level of PD-L1 on neighboring cells, as demonstrated in transactivation assays whereby reporter T cells were co-cultured with cells expressing different levels of PD-L1. PD-L1 expression as low as 6000 receptors per cell was sufficient to activate CD137 in neighboring T cells. In contrast, MCLA-145 blocked PD-1 signaling without requirement for CD137 binding in a PD-1/PD-L1 reporter assay. CD137 signaling was induced by MCLA-145 in multiple primary human immune cell assays including the mixed lymphocyte reaction, human PBMC, and whole blood SEB stimulation assays. MCLA-145 reversed T cell suppression mediated by M2 macrophages or Tregs, in vitro. In addition, MCLA-145 enhanced Ag-specific expansion and differentiation of human naïve CD8+ T cells in vitro.

In vivo, MCLA-145 treatment resulted in significant tumor immune activation and antitumor responses in two separate humanized mouse tumor models. In one model, human T cells expressing NY-ESO specific TCR were adoptively transferred to mice bearing A549 tumors which expressed NY-ESO antigen and human PD-L1. MCLA-145 treatment at 5 mg/kg resulted in 54% tumor growth inhibition (TGI) as compared to T cell only treated mice. In the tumors of MCLA-145 treated mice, the percentage of NY-ESO specific CD8+ T cells were significantly increased compared to controls. In a second model, mice engrafted with human CD34+ cells were implanted with the breast tumor cell line MDA-MB-231. MCLA-145 at 0.5 mg/kg and 5 mg/kg induced significant tumor growth inhibition (55 and 57% respectively) as compared to vehicle control or Fc-silenced huIgG1 controls. Additionally, two out of nine animals in the 5 mg/kg MCLA-145-treated group had complete tumor regression. MCLA-145 increased the number of infiltrating CD8+ T cells, as well as the percentage of central memory CD8+ T cells. The cured animals were then re-challenged with MDA-MB-231 tumor cells, and tumors of previously cured mice were rejected as compared to no growth inhibition in treatment-naïve CD34+ NSG mice. In conclusion, these data support the clinical evaluation of MCLA-145 as a novel, PD-L1 dependent CD137 agonist immune therapy.

Citation Format: Patrick Mayes, Paul Tacken, Steve Wang, Pieter-Fokko van Loo, Thomas Condamine, Hans van der Maaden, Eric Rovers, Steef Engels, Floris Fransen, Ashwini Kulkarni, Yao-bin Liu, Arpita Mondal, Leslie Hall, Soyeon Kim, Marina Martinez, Shaun O'Brien, Edmund Moon, Steven Albelda, Peggy Scherle, Gregory Hollis, Reid Huber, Mark Throsby, Cecile A. Geuijen. A bispecific Fc-silenced IgG1 antibody (MCLA-145) requires PD-L1 binding to activate CD137 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 539.

The Novel Bromodomain and Extraterminal Domain Inhibitor INCB054329 Induces Vulnerabilities in Myeloma Cells That Inform Rational Combination Strategies

PURPOSE

Bromodomain and extraterminal domain (BET) proteins regulate the expression of many cancer-associated genes and pathways; BET inhibitors have demonstrated activity in diverse models of hematologic and solid tumors. We report the preclinical characterization of INCB054329, a structurally distinct BET inhibitor that has been investigated in phase I clinical trials.

EXPERIMENTAL DESIGN

We used multiple myeloma models to investigate vulnerabilities created by INCB054329 treatment that could inform rational combinations.

RESULTS

In addition to c-MYC, INCB054329 decreased expression of oncogenes FGFR3 and NSD2/MMSET/WHSC1, which are deregulated in t(4;14)-rearranged cell lines. The profound suppression of FGFR3 sensitized the t(4;14)-positive cell line OPM-2 to combined treatment with a fibroblast growth factor receptor inhibitor in vivo. In addition, we show that BET inhibition across multiple myeloma cell lines resulted in suppressed interleukin (IL)-6 Janus kinase-signal transducers and activators of transcription (JAK-STAT) signaling. INCB054329 displaced binding of BRD4 to the promoter of IL6 receptor (IL6R) leading to reduced levels of IL6R and diminished signaling through STAT3. Combination with JAK inhibitors (ruxolitinib or itacitinib) further reduced JAK-STAT signaling and synergized to inhibit myeloma cell growth in vitro and in vivo. This combination potentiated tumor growth inhibition in vivo, even in the MM1.S model of myeloma that is not intrinsically sensitive to JAK inhibition alone.

CONCLUSIONS

Preclinical data reveal insights into vulnerabilities created in myeloma cells by BET protein inhibition and potential strategies that can be leveraged in clinical studies to enhance the activity of INCB054329.

Abstract 1893: The evaluation of INCB059872, an FAD-directed inhibitor of LSD1, in preclinical models of T-ALL

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological tumor that is derived from the clonal expansion of immature T-cell progenitors. Multiple genetic and epigenetic alterations are attributed to the development of malignant T cell transformation. Among these, there is supporting evidence for a role of lysine specific demethylase (LSD1) in T-ALL. Oncogenic transcription factors, such as TAL-1, Notch, and ZEB2, form a complex with LSD1 to alter gene expression in T-ALL cells. In addition, LSD1 is aberrantly expressed in ALL, including B-ALL and T-ALL. Furthermore, the overexpression of LSD1 under control of the Sca-1 promoter in transgenic mice triggered T leukemogenesis via acquisition of self-renewal activity and alteration in the differentiation program to T-cell lineages. Together with the known function of LSD1 in regulating the activity of self-renewal in hematological malignancies, these studies prompted evaluation of the efficacy of the potent, selective, and orally bioavailable FAD-directed LSD1 inhibitor, INCB059872, in preclinical models of T-ALL. Expression of LSD1 was abundant in human-T-ALL cell lines as detected by immunoblotting. In vitro, INCB059872 treatment significantly inhibited the proliferation of a subset of human T-ALL cell lines. In vivo, once daily oral administration of INCB059872 inhibited tumor growth significantly in multiple human T-ALL subcutaneous xenograft models including Molt-4, RPMI-8402, CCRF-HSB-2, and CCRF-CEM, but was ineffective against DND-41 xenografts. The anti-tumor efficacy observed with INCB059872 had no clear genetic correlation with Notch mutation status of T-ALL tumors. Combination efficacy studies of INCB059872 with standard care of agents or targeted therapeutic agents in T-ALL models are currently being evaluated. These data suggest exploring the potential clinical development of INCB059872 as a therapy for T-ALL patients.

Citation Format: Melody Diamond, Yvonne Lo, Antony Chadderton, Min Ye, Valerie Roman, Michael Weber, Chunhong He, Liangxing Wu, Swamy Yeleswaram, Alan Roberts, Wenqing Yao, Gregory Hollis, Reid Huber, Peggy Scherle, Bruce Ruggeri, Sang Hyun Lee. The evaluation of INCB059872, an FAD-directed inhibitor of LSD1, in preclinical models of T-ALL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1893.

Abstract 3819: INCAGN02385 is an antagonist antibody targeting the co-inhibitory receptor LAG-3 for the treatment of human malignancies

Lymphocyte activation gene 3 (LAG-3) is a cell surface receptor that negatively regulates antigen-specific T cell responses. LAG-3 expression is generally restricted to populations of recently activated and chronically stimulated exhausted T cells, and is often correlated with general T cell dysfunction across several human malignancies. Accordingly, the LAG-3 pathway has been identified as a potential barrier to productive tumor-specific T cell immunity generated by PD-1/PD-L1 blockade. The antitumor activity from targeting the LAG-3 pathway in preclinical models has provided further rationale for pharmacologic modulation of the LAG-3 axis in cancer patients. INCAGN02385 is an Fc-engineered IgG1κ antibody chosen for development based on its high-affinity binding to human LAG-3, cross-reactivity with cynomolgus monkey LAG-3, and ability to potently block LAG-3 binding with its MHC class II ligand. INCAGN02385 also enhances T cell responsiveness to TCR stimulation alone or in combination with PD-1/PD-L1 axis blockade. Evaluation of INCAGN02385 in cynomolgus monkeys was well-tolerated and demonstrated the expected pharmacokinetic profile. Altogether, these data support assessment of INCAGN02385 in patients with advanced or metastatic solid tumors.

Citation Format: David Savitsky, Rebecca Ward, Christina Riordan, Cornelia Mundt, Shawn Jennings, Joe Connolly, Mark Findeis, Michele Sanicola, Dennis Underwood, Horacio Nastri, Peggy Scherle, Gregory Hollis, Reid Huber, Robert Stein, Marc van Dijk, Nicholas S. Wilson. INCAGN02385 is an antagonist antibody targeting the co-inhibitory receptor LAG-3 for the treatment of human malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3819.

Abstract 3825: INCAGN02390, a novel antagonist antibody that targets the co-inhibitory receptor TIM-3

Unprecedented rates of durable clinical responses have been observed for antibody-based therapeutics targeting immune checkpoint proteins such as cytotoxic T lymphocyte antigen-4 (CTLA-4) or programmed death receptor-1 (PD-1). Nonetheless, a significant number of patients experience de novo resistance or relapse due to adaptive resistance mechanisms. T-cell immunoglobulin and mucin domain containing-3 (TIM-3) is an inhibitory receptor involved in immune tolerance often co-opted by tumors to prevent successful antitumor responses. Accordingly, TIM-3 is frequently expressed on myeloid and so-called exhausted T and NK cells within the tumor microenvironment. Targeting the TIM-3 pathway in preclinical models has provided additional rationale for pharmacologic modulation of this axis in cancer patients. INCAGN02390 is a novel and fully human Fc-engineered IgG1κ antibody developed to antagonize the TIM-3 pathway for the treatment of human malignancies. INCAGN02390 forms a high-affinity interaction with TIM-3, occluding access to the CC'-FG binding cleft and blocking phosphatidylserine binding. In addition, INCAGN02390 elicits rapid receptor internalization, potentially obviating interactions with other described or undescribed ligands. INCAGN02390 also enhances IFN-γ production from T cells undergoing tonic TCR stimulation when combined with PD-1 blockade. Finally, to demonstrate combinatorial potential, we show potent antitumor activity of an anti-mouse TIM-3 antibody in concert with other checkpoint antibodies in vivo. In summary, these data support assessment of INCAGN02390 in patients with advanced or metastatic solid tumors.

Citation Format: Jeremy Waight, Priyadarshini Iyer, Ekaterina Breous-Nystrom, Christina Riordan, Mark Findeis, Dennis Underwood, Joseph Connolly, Michele Sanicola-Nadel, Horacio Nastri, Peggy Scherle, Gregory Hollis, Reid Huber, Robert Stein, Mark van Dijk, Nicholas S. Wilson. INCAGN02390, a novel antagonist antibody that targets the co-inhibitory receptor TIM-3 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3825.

Abstract 1888: The FAD-directed LSD1 specific inhibitor, INCB059872, is a promising epigenetic agent for AML therapy by inducing differentiation of leukemic stem/progenitor cells

Numerous studies have elucidated that the most pivotal functions of lysine specific demethylase-1 (LSD1) are associated with regulating normal or malignant hematopoiesis by maintaining stem cell self-renewal and regulating myeloid differentiation. In preclinical models, studies with either pharmacological inhibition or genetic knockdown of LSD1 demonstrated that LSD1 is essential for differentiation of progenitor cells during normal hematopoiesis. In the clinic, AML manifests itself via clonal expansion of abnormal differentiation and proliferation of myeloid cells and, therefore, the inhibition of LSD1 activity with small molecule inhibitors could be a promising therapeutic approach for AML. Previously, we reported upon the identification of a flavin adenine dinucleotide (FAD) directed LSD1 specific inhibitor, INCB059872, which is efficacious in preclinical mouse models utilizing human AML cell lines and primary AML cells by inducing cell differentiation as indicated by the induction of CD11b and CD86 markers. Using a larger panel of myeloid and HSC flow cytometry markers, our currents efforts expanded upon these observations to ascertain whether INCB059872 enhanced lineage commitment at hematopoietic stem cell (HSC) and/ or promoted monocytic/granulocytic differentiation of human primary AML cells ex vivo and in human systemic AML PDX models. In both human AML PDX models and human primary AML samples, INCB059872 increased myeloid differentiation with increasing populations of monocytes (CD14+) and granulocytes (CD15+). Furthermore, INCB059872 induced the differentiation of early hematopoietic progenitors, CD34+/CD38- to more committed CD34+/CD38+ multipotent/oligopotent progenitors, which in turn gave rise to lineage specific progenitors in the human AML PDX models. These studies support further exploration of INCB059872 as a promising novel epigenetic agent for AML therapy whose mechanism of action lies in part through the induction of differentiation of leukemic stem/progenitor cells to more committed hematopoietic lineages.

Citation Format: Antony Chadderton, Min Ye, Melody Diamond, Valerie Roman, Michael Weber, Chunhong He, Liangxing Wu, Swamy Yeleswaram, Alan Roberts, Wenqing Yao, Gregory Hollis, Reid Huber, Peggy Scherle, Bruce Ruggeri, Sang Hyun Lee. The FAD-directed LSD1 specific inhibitor, INCB059872, is a promising epigenetic agent for AML therapy by inducing differentiation of leukemic stem/progenitor cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1888.

Abstract A168: The LSD1 specific inhibitor INCB059872 enhances the activity of mechanistically distinct immunotherapeutic agents in the syngeneic 4T1 mouse mammary tumor model

Despite the successes of immune checkpoint blockade for the treatment of a variety of cancers, effective combinatorial therapy strategies are needed to achieve more durable and complete clinical responses in patients. Pharmacologically inducing a more permissive tumor microenvironment to enhance patient responsiveness to immune modulatory therapies may offer a rational approach to address this medical need. In particular, targeting immune suppressive myeloid cells, including myeloid-derived suppressor cells (MDSC), tumor-associated macrophages (TAM), and polymorphonuclear (PMN) cells in the tumor microenvironment may enhance the effectiveness of immune checkpoint blockade. Since MDSCs abundantly infiltrate syngeneic 4T1 mammary tumors compared with other commonly used syngeneic tumor models, this model was chosen for testing the hypothesis that the modulation of MDSC activity enhances antitumor activity driven by adaptive immunity. We have recently demonstrated (#4635, AACR 2017) that the selective Lysine Specific Demethylase 1 (LSD1) inhibitor, INCB059872, redirected myeloid differentiation toward monocyte/macrophages in vitro and in vivo and reduced the PMN-MDSC population in the syngeneic 4T1 murine mammary tumor model. The combination of INCB059872 and PD1/PDL1 axis blockade enhanced antitumor activity and was well tolerated in this model. In this study, we further tested if modulation of MDSCs with INCB059872 could enhance the effect of mechanistically distinct immunotherapeutic agents. The combination of INCB059872 with agonist anti-OX40 or anti-GITR T cell costimulatory monoclonal antibodies significantly augmented antitumor efficacy in the 4T1 model. These results consistently demonstrated that the inhibition of immune suppressive MDSCs increased antitumor activity of immune checkpoint modulatory monoclonal antibodies. Next, we tested the combination of INCB059872 with small-molecule inhibitors targeting the tumor microenvironment. The combination of INCB059872 with highly selective small-molecule immunotherapeutic inhibitors such as epacadostat (IDO1 inhibitor) and ruxolitinib (JAK1/JAK2 inhibitor) demonstrated similar marked increases in antitumor efficacy. The studies to understand mechanism of enhanced activity are under way. In summary, consistent with previous findings, the combination of INCB059872 with a variety of mechanistically distinct immunotherapeutic agents significantly enhanced antitumor efficacy in the syngeneic 4T1 murine mammary tumor model. These results strongly support the hypothesis that reshaping the tumor microenvironment by redirecting myeloid differentiation as a result of LSD1 inhibition enhances the responsiveness of the tumor microenvironment to immunotherapies, supporting the therapeutic rationale for the combination of an LSD1 inhibitor with various immunotherapeutic agents to improve clinical responses in cancer patients.

Citation Format: Sang Hyun Lee, Melody Diamond, Antony Chadderton, Thomas Condamine, Huiqing Liu, Valerie Roman, Jin Lu, Yan Zhang, Maxim Soloviev, Chunhong He, Liangxing Wu, Holly Koblish, Timothy Burn, Andrew Combs, Swamy Yeleswaram, Alan Roberts, Wenqing Yao, Gregory Hollis, Reid Huber, Peggy Scherle, Bruce Ruggeri. The LSD1 specific inhibitor INCB059872 enhances the activity of mechanistically distinct immunotherapeutic agents in the syngeneic 4T1 mouse mammary tumor model [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A168.

Abstract 531: Activity of the selective FGFR 1, 2 and 3 inhibitor INCB054828 in genetically-defined models of triple-negative breast cancer

Activation of the Fibroblast Growth Factor (FGF)-FGF Receptor (FGFR) signaling axis occurs in many human cancers. In preclinical models, cell lines with genetic aberrations in FGF/FGFR genes are preferentially inhibited by compounds that selectively target the FGFR kinase. INCB54828 is a potent, selective, and reversible inhibitor of FGFR1, 2 and 3 that is currently in Phase 2 clinical trials for advanced malignancies characterized by FGF-FGFR alterations. In this study, we investigated the efficacy of INCB054828 in models of triple-negative breast cancer (TNBC).

FGFR1 and FGFR2 are amplified in approximately 4% and 5% of TNBC, respectively, and oncogenic fusion proteins including FGFR3-TACC3 have also been identified in some TNBC specimens. To profile the activity of INCB054828, we screened a panel of diverse TNBC cell lines that are representative of each of the four subtypes of TNBC. Three human TNBC lines MFM223, SUM185 and SUM52PE were highly sensitive to INCB054828 in viability assays. Each of these responsive cell lines has a known alteration in FGFR, whereas TNBC lines lacking any aberrations in FGF/FGFR genes were refractory to growth inhibition. Inhibition of cell viability was associated with suppression of growth promoting pathways including Ras-MAPK. To confirm this association in vivo, four PDX models of TNBC were tested: two chemo-refractory models with FGFR1 amplification (CNV = 4 and 6) and two without any known FGF/FGFR alterations. Both of the models with FGFR1 copy number gain showed a response to INCB054828 as monotherapy with 36 and 78% tumor growth inhibition that was statistically significant vs vehicle control (P<0.05 and p<0.001, respectively). At the maximally efficacious dose of 1 mg/kg daily, neither PDX model lacking FGF/FGFR alteration responded to the treatment. Finally to assess the effect of the microenvironment on drug sensitivity, mouse 4T1 breast cancer cells were orthotopically implanted into the mammary fat pad; under these conditions, 4T1 tumors retained sensitivity to a standard dose of INCB054828. In summary these results demonstrate that the FGFR1/2/3 inhibitor INCB054828 is highly active against models of TNBC with genetic alterations in FGFR genes, and confirms the importance of patient stratification strategies for clinical trials with FGFR targeted therapies.

Citation Format: Phillip C.C. Liu, Brian D. Lehmann, Bruce Ruggeri, Darlise DiMatteo, Johanna M. Schafer, Jin Lu, Sang Hyun Lee, Luping Lin, Timothy C. Burn, Melody Diamond, Alla Volgina, Liangxing Wu, Gregory Hollis, Reid Huber, Jennifer A. Pietenpol, Peggy Scherle. Activity of the selective FGFR 1, 2 and 3 inhibitor INCB054828 in genetically-defined models of triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 531. doi:10.1158/1538-7445.AM2017-531

Abstract 1162: The evaluation of INCB059872, an FAD-directed covalent inhibitor of LSD1, in preclinical models of Ewing sarcoma

Ewing sarcoma is a rare bone cancer affecting predominantly children. The chromosomal translocation of chromosomes 11 and 22 results in the EWS/FLI gene fusion oncoprotein that is associated with ~85% of Ewing sarcoma cases. The EWS/FLI fusion protein is involved in deregulating gene expression and consequently causing cellular transformation. It was previously reported that lysine specific demethylase 1 (LSD1) regulates EWS/FLI transcriptional activity via its functional interaction through the NuRD co-repressor complex. We therefore evaluated whether inhibition of LSD1 could have anti-tumor effects in Ewing sarcomas that express the EWS/FLI fusion oncoprotein. INCB059872 is a potent, selective, and orally available FAD-directed covalent inhibitor of LSD1. To investigate the potential utility of INCB059872 in Ewing sarcoma, the A673 cell line having the characteristic chromosomal translocation was chosen as the experimental model system. INCB059872 inhibition of LSD1 did not significantly alter A673 proliferation in vitro. However, INCB059872 inhibited oncogenic transformation as determined by colony formation clonogenicity assays. NKX.2.2 was previously identified as a critical downstream target molecule of the EWS-FLI fusion oncoprotein that is required for transformation. A significant downregulation of NKX2.2 was observed in A673 cells treated with INCB059872, suggesting that INCB059872 mediates its effects through modulation of the EWS/FLI -NKX2.2 axis. Oral administration of INCB059872 significantly suppressed the growth of both A673 and SK-ES Ewing sarcoma xenografts in vivo. In addition, in vivo efficacy was evaluated in patient derived xenograft (PDX) models that were developed from relapsed tumor tissues of Ewing sarcoma patients. Notably, a subset of PDX models having EWS/FLI translocations (3/6) exhibited significant tumor growth inhibition at well-tolerated doses of INCB059872. Molecular signatures obtained from RNA-Seq data with these PDX models exhibited intrinsic differences between responders and non-responders, suggesting additional molecular or genetic variations may contribute to their sensitivity to INCB059872. Studies identifying potential candidate molecular mechanisms are underway. Together, these data suggest that INCB059872 may be therapeutically efficacious in a subset of Ewing sarcoma patients.

Citation Format: Valerie Dostalik Roman, Min Ye, Huiqing Liu, Melody Diamond, Antony Chadderton, Yvonne Lo, Xuesong M. Liu, Jin Lu, Chunhong He, Liangxing Wu, Timothy Burn, Richard Wynn, Wenqing Yao, Gregory Hollis, Gregory Hollis, Peggy Scherle, Bruce Ruggeri, Sang Hyun Lee. The evaluation of INCB059872, an FAD-directed covalent inhibitor of LSD1, in preclinical models of Ewing sarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1162. doi:10.1158/1538-7445.AM2017-1162

Abstract 2100: Selective inhibition of FGFR4 by INCB062079 is efficacious in models of FGF19- and FGFR4-dependent cancers

Aberrant signaling through Fibroblast Growth Factor Receptors (FGFR) has been reported in multiple types of human cancers. FGFR4 signaling contributes to the development and progression of subsets of cancer: in approximately 10 percent of hepatocellular carcinoma (HCC), genetic amplification of FGF19, encoding an endocrine FGF ligand that activates FGFR4-KLB receptors, has been reported. In models with this alteration, FGF19-FGFR4 signaling is oncogenic and antagonism of the FGF19-FGFR4 axis has been shown to be efficacious suggesting that selective targeting of FGFR4 may be an effective strategy for malignancies with FGFR4 activation.

We describe the preclinical characterization of INCB062079 a potent and selective inhibitor of the FGFR4 kinase. In biochemical assays INCB062079 inhibited FGFR4 with low nM potency and exhibited at least 250-fold selectivity against other FGFR kinases and greater than 800-fold selectivity against a large kinase panel. This selectivity derives from the ability of INCB062079 to bind irreversibly to Cys552, a residue within the active site of FGFR4 that is non-conserved among other FGFR receptors. Covalent binding of INCB062079 to Cys552 was demonstrated using a LC/MS/MS-based proteomic analysis that confirmed specificity for the target Cys. In assays using HCC cells with autocrine production of FGF19, INCB062079 inhibited the autophosphorylation of FGFR4 and blocked signal transduction by FGFR4 to downstream markers of pathway activation. Cancer cell lines that have amplification and expression of FGF19 are uniquely sensitive to growth inhibition by INCB062079 (EC50 less than 200 nM) compared with HCC cell lines or normal cells without FGF19-FGFR4 dependence (EC50 > 5000 nM) confirming selectivity for FGFR4. In vivo, oral administration of INCB062079 inhibited the growth and induced significant regressions of subcutaneous xenograft tumors dependent upon FGFR4 activity at doses that were well-tolerated (10-30 mg/kg BID) and did not result in a significant increase in serum phosphate levels which is observed with FGFR1/2/3 inhibition. Suppression of tumor growth correlated with pharmacodynamic inhibition of FGFR4 signaling. Collectively, these preclinical studies demonstrate that INCB062079 potently and selectively inhibits models of FGF19-FGFR4-dependent cancers in vitro and in vivo, supporting clinical evaluation in patients harboring oncogenic FGFR4 activation.

Citation Format: Phillip C.C. Liu, Liang Lu, Kevin Bowman, Matthew C. Stubbs, Liangxing Wu, Darlise DiMatteo, Sindy Condon, Ronald Klabe, Ding-Quan Qian, Xiaoming Wen, Paul Collier, Karen Gallagher, Michael Hansbury, Xin He, Bruce Ruggeri, Yan-ou Yang, Maryanne Covington, Timothy C. Burn, Sharon Diamond-Fosbenner, Richard Wynn, Reid Huber, Wenqing Yao, Swamy Yeleswaram, Peggy Scherle, Gregory Hollis. Selective inhibition of FGFR4 by INCB062079 is efficacious in models of FGF19- and FGFR4-dependent cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2100. doi:10.1158/1538-7445.AM2017-2100

Abstract 2618: Agonist antibodies targeting OX40 and GITR enhance the activity of the IDO1-selective inhibitor epacadostat in preclinical models

The majority of immunotherapeutic agents developed thus far either attempt to stimulate a more productive anti-tumor immune response or to inhibit key proteins in the immunosuppressive tumor milieu. PD-1/PD-L1 axis blockade, CTLA-4 blockade and IDO1 inhibition are examples of the latter approach and have been utilized to reverse the suppressive tumor microenvironment, resulting in clinical benefit for cancer patients. Recent clinical and preclinical data have also demonstrated that combining these approaches results in enhanced therapeutic benefit. Notably, the IDO1-selective inhibitor epacadostat has been shown to increase the efficacy of two checkpoint inhibitors, the anti-CTLA-4 antibody ipilimumab and the anti-PD-1 antibody pembrolizumab, in patients with melanoma. Because both checkpoint receptors and IDO1 serve as negative regulators of the immune response, we also explored the ability of IDO1 inhibition to combine with agents that directly activate T cells through costimulatory receptors of the tumor necrosis factor receptor (TNFR) superfamily. Rodent active surrogate agonist antibodies to 4-1BB, OX40 and GITR were tested with epacadostat in multiple preclinical models. In the B16-SIY melanoma model that does not express IDO1 in tumor cells, both epacadostat and anti-OX40 had little effect, but the combination resulted in enhanced efficacy. This was associated with increased infiltrates of CD8+ T cells and decreased numbers of FoxP3+ TILs. Increased numbers of SIY-reactive T cells were found in both the tumor and the TDLN post-therapy. In contrast, epacadostat did not provide any enhancement to the activity seen with 4-1BB. Clear combinatorial effects were seen with anti-GITR and epacadostat in the more inflamed, IDO1-expressing PAN02 pancreatic cancer model. These data suggest that IDO1 inhibition can be effective in combination with agents that agonize T cell costimulatory receptors as well as with agents that block coinhibitory receptors.

Citation Format: Holly K. Koblish, Brendan Horton, Michael Hansbury, Sybil O'Connor, Kerri Lasky, Christina Stevens, Thomas Condamine, Leslie Hall, Liang-Chuan Wang, Yue Zhang, Horacio Nastri, Gregory Hollis, Reid Huber, Thomas Gajewski, Peggy Scherle. Agonist antibodies targeting OX40 and GITR enhance the activity of the IDO1-selective inhibitor epacadostat in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2618. doi:10.1158/1538-7445.AM2017-2618

Abstract 2032: Combination of epigenetic regulation via LSD1 inhibition with signal transduction inhibitors significantly enhances anti-tumor activity in models of hematologic malignancies

Combinatorial therapeutic strategies have achieved improved response rates and durability of responses in several malignancies either by selectively targeting distinct and non-overlapping oncogenic signaling pathways (e.g. PARP and phosphoinositide 3-kinase (PI3K) inhibition in subsets of breast and ovarian cancers), or alternatively, inhibiting distinct nodal points of regulation in common oncogenic signaling pathways (e.g BRaf and MEK inhibition in subsets of melanoma). Recent data suggest that deregulated epigenetic modifications may be just as significant as genetic mutations in driving cancer development and growth by inhibition of tumor suppressor activity and activation of oncogenic pathways. We therefore hypothesized that an epigenetic regulator could potentiate the efficacy of a protein kinase inhibitor to result in robust tumor growth inhibition. We previously reported that the potent and selective LSD1 inhibitor INCB059872 potently inhibited tumor growth in multiple tumor xenograft models of AML and SCLC as a single agent and in a combination with standard of care of agents. In this study, we explored the anti-tumor effect of combining INCB059872 and various signal transduction pathway inhibitors, including the PIM kinase inhibitor INCB053914, the JAK1/2 inhibitor ruxolitinib, or the PI3K delta-selective inhibitor INCB050465 in models of human hematologic malignancies. Each of these therapeutic combinations significantly inhibited tumor growth in the Molm-16 human AML xenograft model. Mechanistic studies suggested that MYC expression levels were downregulated by these combinations both in vitro and in vivo. Treatment with INCB059872 alone or in combination with signal transduction kinase inhibitors significantly downregulated cytokines levels, particularly IL-10, sCD40L, and MCP-1 in Molm-16 tumors. These data suggest that the combination of an LSD1 inhibitor and signal transduction inhibitor can co-regulate key tumor intrinsic and extrinsic pathways involved in paracrine or autocrine signaling in AML. In addition to the improved efficacy observed in AML models, the combination of INCB059872 with the PI3Kdelta inhibitor INCB050465 enhanced tumor growth inhibition in the Will-2 xenograft model (GCB subtype, double hit lymphoma), whereas the activity of these single agents were modest in this particular subtype of lymphoma. Additional mechanistic studies are ongoing to further understand the molecular bases of these observations. Taken together, these data suggest that targeting distinct epigenetic and oncogenic signaling pathways may potentiate anti-tumor efficacy and overcome intrinsic resistance mechanisms in specific hematologic malignancies.

Citation Format: Sang Hyun Lee, Matthew Stubbs, Ashish Juvekar, Melody Diamond, Antony Chadderton, Robert Collins, Xiaoming Wen, Holly Koblish, Chunhong He, Liangxing Wu, Richard Wynn, Andrew Combs, Chu-Biao Xue, Wenqing Yao, Gregory Hollis, Reid Huber, Peggy Scherle, Bruce Ruggeri. Combination of epigenetic regulation via LSD1 inhibition with signal transduction inhibitors significantly enhances anti-tumor activity in models of hematologic malignancies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2032. doi:10.1158/1538-7445.AM2017-2032

Abstract 143: Preclinical studies on potential therapeutic combination partners for the potent and selective PI3Kδ inhibitor INCB050465 in DLBCL

The delta isoform of PI3K (PI3Kδ) plays an essential role in B-cell development and function by mediating the signaling of key receptors on B cells. Increased malignant B cell proliferation and survival has also been associated with aberrant activation of PI3Kδ, making selective inhibition of this isoform an attractive therapeutic approach for the treatment of B cell malignancies. INCB050465 is a potent inhibitor of PI3Kδ, with a >20,000 fold selectivity over other PI3K isoforms. Emerging clinical data indicate that INCB050465 monotherapy is well tolerated and results in promising clinical responses in patients with various lymphoma histologies, including those with DLBCL. We therefore sought to explore rational combination strategies for INCB050465 using mouse xenograft models of ABC-subtype (HBL-1), GCB-subtype (Pfeiffer), and GCB/double-hit (WILL-2) human DLBCL, evaluating standard of care agents such as bendamustine and rituximab, as well as with targeted agents. PIM inhibition is a logical addition to PI3Kδ inhibition as a therapeutic approach as both kinases play a critical role in the AKT signaling pathway, having overlapping substrates. Likewise BET inhibition is a rational addition to PI3Kδ inhibition in “double-hit” DLBCL due to de-regulation of MYC transcriptional activity. In vivo studies performed in the Pfeiffer xenograft model demonstrate that INCB050465 combined with the pan-PIM inhibitor INCB053914 yielded complete tumor regressions. This profound decrease in tumor cell survival was due in part to the significant reduction in pBAD levels resulting from dual PIM and PI3Kδ inhibition. Despite modest single agent activity in vivo, the combination of INCB050465 with BET inhibitors, INCB054329 or INCB057643, resulted in significant anti-tumor efficacy in all of the DLBCL models studied, and caused a marked repression in tumor MYC expression. To study the transcriptional effects of combining PI3Kδ and BET inhibitors in this lymphoma model, WILL-2 xenograft tumors from mice treated with single dose INCB050465, INCB054329, the combination, or vehicle control were analyzed by RNAseq. INCB050465 enhanced the ability of INCB054329 to repress a MYC-driven transcriptional program, and the combination also regulated multiple developmental and inflammatory pathways. Together, these data support the clinical evaluation of the PI3Kδ inhibitor INCB050465 as part of a combination regimen with PIM or BET inhibitors for the treatment of DLBCL.

Citation Format: Matthew C. Stubbs, Robert Collins, Leslie Hall, Alla Volgina, Holly Koblish, Sang Hyun Lee, Timothy Burn, Phillip C. Liu, Jin Lu, Eddy Yue, Yun-Long Li, Andrew P. Combs, Wenqing Yao, Gregory Hollis, Reid Huber, Bruce Ruggeri, Peggy Scherle. Preclinical studies on potential therapeutic combination partners for the potent and selective PI3Kδ inhibitor INCB050465 in DLBCL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 143. doi:10.1158/1538-7445.AM2017-143

Abstract 3643: INCAGN1876, a unique GITR agonist antibody that facilitates GITR oligomerization

Glucocorticoid-induced TNFR family related protein (GITR, CD357 or TNFRSF18) is a member of the tumor necrosis factor receptor superfamily (TNFRSF). Like other T cell co-stimulatory TNFR family members, GITR utilizes multiple oligomerization states to regulate the initiation of downstream signaling during T cell activation by antigen presenting cells (APCs). The formation of receptor superclusters, comprised of two or more trimeric molecules, has been defined for multiple TNFRs as a means of regulating downstream signal amplification. For co-stimulatory TNFRs, like GITR, CD137 and OX40, signaling outcomes in T cells are primarily mediated via the NFκB pathway that promotes cell survival and effector cell activities in response to suboptimal T cell receptor (TCR) stimulation. It has been hypothesized that the manipulation of the oligomeric states of co-stimulatory TNFRs using antibodies may have therapeutic utility in enhancing the activity of tumor-reactive T cells, either as single agents or in combination with other immunomodulatory or immune education strategies. Here we describe a structure-based analysis of two functionally distinct classes of anti-human GITR antibodies that stabilize unique conformational states of the receptor. INCAGN1876, a human IgG1 monoclonal anti-GITR antibody, was found to engage a conformational epitope located within a β-turn of the extracellular domain of GITR. This antibody binding site modified the equilibrium of GITR monomer, dimer and trimers to promote receptor oligomerization, resulting in downstream NFκB signaling. Notably, this mode of INCAGN1876 receptor engagement enabled it to effectively activate the GITR pathway in recently primed T cells. By contrast, a second reference anti-GITR antibody required concomitant TCR co-engagement in order to modulate the GITR pathway. High content confocal analysis was used to evaluate the kinetics of GITR clustering by both classes of anti-GITR antibody, confirming our T cell functional analysis. The ability of INCAGN1876 to engage and effectively activate GITR on recently primed T cells may enable them to overcome suppressive features of the tumor microenvironment. Notably, INCAGN1876 was shown to promote T cell co-stimulation both as a single agent and in combination with other antibodies targeting PD-1, CTLA-4 and OX40. Finally, we compared the pharmacologic activity of INCAGN1876 to Fc variants of this antibody with diminished binding to the inhibitory Fcγ receptor (FcγR), CD32B. The superiority of an IgG1 antibody in these assays was consistent with the potential to achieve optimal GITR clustering by FcγRs, while maintaining the potential for FcγR-mediated effector cell activity directed toward intratumoral GITRhigh regulatory T cells. INCAGN1876 is currently under evaluation in Phase 1/2 studies in subjects with advanced metastatic solid tumors (NCT02697591).

Citation Format: Ana M. Gonzalez, Mariana L. Manrique, Lukasz Swiech, Thomas Horn, Jeremy Waight, Yuqi Liu, Shiwen Lin, Dennis Underwood, Ekaterina Breous, Olivier Leger, Volker Seibert, Taha Merghoub, Roberta Zappasodi, Gerd Ritter, David Schaer, Kevin N. Heller, Kimberli Brill, Peggy Scherle, Gregory Hollis, Reid Huber, Marc van Dijk, Jennifer Buell, Robert Stein, Nicholas S. Wilson. INCAGN1876, a unique GITR agonist antibody that facilitates GITR oligomerization [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3643. doi:10.1158/1538-7445.AM2017-3643

Abstract 3780: Activity of the BET inhibitor INCB054329 in models of lymphoma

Inhibitors of the BET family of Bromodomain proteins have been shown to be growth inhibitory across a spectrum of tumor types due to their ability to regulate expression of key survival and cell fate determining genes such as c-myc. Among the various tumor histologies, hematologic malignancies are among the most sensitive cancers to BET inhibition. INCB054329 is a novel, non-benzodiazepine, selective BET inhibitor that is undergoing Phase 1 clinical trials and that has shown encouraging in vitro and in vivo preclinical activity in several models of hematologic malignancy. In the current study, the activity of INCB054329 was evaluated in models of B cell malignancy. INCB54329 effectively inhibited the in vitro growth of a panel of cell lines representing both Hodgkin and non-Hodgkin lymphoma. Treated cells arrested primarily in G1 with sensitive lines also exhibiting dose and time-dependent apoptosis. Within a panel of double-hit lymphoma cell lines, which have activating chromosomal rearrangements in both c-myc and bcl-2, INCB054329 potently inhibited cell growth and was more effective than antagonists of BTK, bcl-2, PIM and PI3Kδ. INCB054329 also showed in vivo efficacy in models of diffuse large B-cell lymphoma (DLBCL). As a single agent, oral administration of INCB054329 inhibited tumor growth in Pfeiffer (GBC) and WILL-2 (GCB, double-hit) subcutaneous xenograft models. The in vivo combination of bendamustine with INCB054329 enhanced anti-tumor efficacy compared with either agent alone in the Pfeiffer model, and the combination was well tolerated. A rational, targeted combination strategy was evaluated involving INCB054329 and a selective, orally active PI3Kδ inhibitor, INCB050465, which is currently in clinical trials in B cell malignancies. Combining INCB054329 with PI3Kδ inhibition markedly enhanced anti-tumor efficacy, increasing the incidence of partial tumor regressions in vivo. In this model, both INCB054329 and INCB050465 treatment led to a reduction in c-Myc protein levels, suggesting a convergence between modulation of BET transcriptional regulation and the PI3Kδ pathway. These data suggest that clinical investigation of INCB054329, both as monotherapy and in combination with standard of care or novel targeted therapies, in several classes of B cell lymphoma, including high risk double hit lymphoma, is warranted.

Citation Format: Matthew Stubbs, Robert Collins, Alla Volgina, Mike Liu, Margaret Favata, Mark Rupar, Xiaomng Wen, Richard Sparks, Thomas Maduskuie, Maryanne Covington, Timothy Burn, Bruce Ruggeri, Andrew P. Combs, Wenqing Yao, Reid Huber, Gregory Hollis, Peggy Scherle, Phillip CC Liu. Activity of the BET inhibitor INCB054329 in models of lymphoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3780.

Abstract 4904: The BET inhibitor INCB054329 enhances the activity of checkpoint modulation in syngeneic tumor models

Inhibitors of the BET family of bromodomain proteins have been shown to be growth inhibitory across a spectrum of tumor types due to their ability to regulate the expression of key survival and cell fate determining genes such as c-myc. In addition to their role in cancer, studies using genetic knockdown and small molecule inhibitors have demonstrated that targeting BET proteins controls the expression of pro-inflammatory cytokine genes in macrophages and is therapeutic in models of acute inflammation. These data suggest that in addition to their tumor intrinsic effects, BET inhibitors may also regulate the cytokine milieu within the tumor microenvironment and have immunomodulatory activity in cancer. To study this aspect, we evaluated INCB054329, a novel and selective BET inhibitor currently in Phase 1 trials, alone and in combination either with epacadostat, a highly selective IDO1 inhibitor, or with PD-1/PD-L1 axis blockade in syngeneic tumor models using immunocompetent animals. When used alone, INCB054329 suppressed a panel of cytokines and chemokines in a whole blood assay, confirming that INCB054329 can antagonize a pro-inflammatory response. The potency of INCB054329 in reducing the levels of these inflammatory mediators in the whole blood assay was similar to that for inhibition of c-myc, suggesting that the effects were on-target. INCB054329 was capable of inhibiting the growth of multiple syngeneic tumor models in immunocompetent mice, whereas only modest tumor growth inhibition was observed in immunodeficient mice and a lack of activity was observed in vitro, supporting the immunomodulatory activity of the compound. Because maximal in vivo tumor growth inhibition required an intact immune system, we investigated the impact of INCB054329 on various immune cell subsets, both in vitro and in vivo. Of note, increases in effector T cell populations were observed and efforts are ongoing to further characterize the tumor infiltrating immune cells following INCB054329 treatment. The mechanistic complimentarity of this novel BET inhibitor-mediated immunomodulation was also evaluated in combination with other therapeutically relevant mechanisms, including IDO1 inhibition and PD-1 axis blockade. Enhanced efficacy was observed with all INCB054329-containing regimens. These data demonstrate for the first time that BET inhibition can suppress tumor growth through both tumor-intrinsic and immune modulatory mechanisms, and support the potential of epigenetic-based, immunotherapy combinations as a novel approach to cancer therapy.

Citation Format: Holly K. Koblish, Michael Hansbury, Leslie Hall, Liang-Chuan Wang, Yue Zhang, Maryanne Covington, Timothy Burn, Mark Rupar, Christine Gardiner, Thomas Condamine, Kerri Lasky, Matthew C. Stubbs, Eddy Yue, Richard Sparks, Richard Sparks, Thomas Maduskuie, Andrew P. Combs, Gregory Hollis, Reid Huber, Phillip CC Liu, Peggy Scherle. The BET inhibitor INCB054329 enhances the activity of checkpoint modulation in syngeneic tumor models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4904.

Abstract 4696: The LSD1 inhibitor INCB059872 is synergistic with ATRA in models of non-APL acute myelogenous leukemia

Acute myeloid leukemia (AML) is a disease characterized by the expansion of a hematopoietic stem cell like population caused in part by a block of myeloid differentiation. In AML, an altered epigenetic landscape, often arising from genetic lesions in epigenetic regulators, enforces an oncogenic expression profile and suppresses myeloid differentiation. Lysine specific demethylase 1 (LSD1) catalyzes the demethylation of lysine 4 and 9 of histone H3 through an FAD-dependent redox process. Aberrant LSD1 activity has been proposed to maintain oncogenic programs and prevent differentiation of multiple subtypes of AML. Intriguingly, recent studies indicate that LSD1 inhibition can reactivate an all-trans retinoic acid (ATRA)-dependent differentiation program in non-acute promyelocytic leukemia (APL) hematologic malignancies, a genetically heterogeneous group of blood cancers that normally respond poorly to ATRA therapy. In this study, we assessed the in vitro and in vivo effects of combining ATRA with INCB059872, a potent and selective FAD-directed LSD1 inhibitor, in non-APL AML models. As a single agent, INCB059872 induced differentiation of AML cells and when combined with ATRA, synergistically promoted differentiation as indicated by induction of CD86 and CD11b expression. In addition, the combination of INCB059872 and ATRA increased apoptosis in a panel of non-APL AML cell lines. Similarly, the combination significantly increased the fraction of CD86+CD11b+ cells and reduced cell viability in a panel of primary AML cells ex vivo. These effects in both human AML cell lines and human primary AML cells were observed across distinct FAB subtypes and genetic mutation profiles. Microarray profiling coupled with bioinformatic analysis of MV-4-11 cells demonstrated that the number of regulated genes related to differentiation and apoptotic pathways was markedly elevated in cells treated with the combination of LSD1 inhibition and ATRA relative to single agents. The synergistic increase in levels of myeloid lineage transcription factors GFI1, PU.1, CEBP and a decrease in levels of the oncogene c-MYC in the combination groups were validated by q-RT-PCR and western blot analyses. In vivo, the combination of INCB059872 and ATRA enhanced CD86 and CD11b induction and reduced tumor growth in the THP-1 xenograft model of AML compared with monotherapy. Similarly, oral administration of INCB059872 and ATRA in PDX mouse models markedly increased levels of CD11b+ cells in bone marrow. Collectively, these data underscore the synergy that can exist between LSD1 inhibition and retinoic acid receptor agonism, and provide a scientific rationale for the clinical evaluation of INCB059872 and ATRA in non-APL AML patients.

Citation Format: Min Ye, Mike Liu, Jin Lu, Yvonne Lo, Margaret Favata, Gengjie Yang, Melody Diamond, Valerie Dostalik, Paul Waeltz, Melissa Ann Fischer, Chunhong He, Liangxing Wu, Xiaochuan Shan, Hong Chang, Maryanne Covington, Yanlong Li, Tim Burn, Richard Wynn, Wenqing Yao, Gregory Hollis, Reid Huber, Peggy Scherle, Michael Savona, Martin Carroll, Bruce Ruggeri, Sang Hyun Lee. The LSD1 inhibitor INCB059872 is synergistic with ATRA in models of non-APL acute myelogenous leukemia. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4696.

Abstract 3204: INCAGN01949: an anti-OX40 agonist antibody with the potential to enhance tumor-specific T-cell responsiveness, while selectively depleting intratumoral regulatory T cells

OX40 (CD134, TNFRSF4) is a T cell co-stimulatory receptor that potentiates T cell receptor (TCR) signaling during CD4+ and CD8+ T cell priming, effector cell differentiation and memory T cell recall responses. In preclinical mouse tumor models, surrogate anti-OX40 agonist antibodies have shown remarkable single agent anti-tumor efficacy, as well as the ability to combine effectively with other immunomodulatory antibodies and immune education strategies, such as therapeutic cancer vaccines. Agonistic antibodies targeting OX40 are predicted to counteract the immunosuppressive tumor microenvironment and promote tumor-specific T cell immunity via two primary mechanisms: 1) binding and activating OX40 signaling in tumor-specific effector and memory T cells, thereby enhancing their responsiveness to tumor-associated antigens, and 2) co-engaging Fcγ receptors expressed by tumor-associated effector cells, and facilitating the selective depletion of intratumoral regulatory T cells.

INCAGN01949 is a novel fully human IgG1 monoclonal antibody identified using the Retrocyte Display™ platform that is being developed for the treatment of advanced malignancies. INCAGN01949 recognizes human and cynomolgus monkey OX40 with comparable binding affinity. INCAGN01949 has been optimized to potently mediate receptor forward signaling under conditions of suboptimal TCR stimulation, leading to features like enhanced production of TNFα and IFNγ, and concomitant suppression of IL-10. INCAGN01949 achieves this functionality through OX40 clustering and downstream activation of the NFκB pathway in T cells, which is sustained across a broad range of antibody concentrations. Consistent with mouse preclinical tumor models, OX40 was found to be selectively overexpressed by intratumoral regulatory T cells from a variety of primary human tumor samples. Commensurate with its human IgG1 Fc region, INCAGN01949 can effectively co-engage activating Fcγ receptors on immune effector cells, including natural killer cells and macrophages. Therefore INCAGN01949 has the potential to mediate selective effector cell activity toward intratumoral populations of regulatory T cells.

The biophysical and functional attributes of INCAGN01949 make it suited for clinical development, both as a single agent and in combination with other immunomodulatory antibodies or immune education strategies.

Citation Format: Ana Maria Gonzalez, Mariana L. Manrique, Ekaterina Breous, David Savitsky, Jeremy Waight, Randi Gombos, Yuqi Liu, Shiwen Lin, Taha Merghoub, Daniel Hirschhorn-Cymerman, Gerd Ritter, Jedd Wolchok, Peggy Scherle, Gregory Hollis, Reid Huber, Marc Van Dijk, Robert Stein, Nicholas S. Wilson. INCAGN01949: an anti-OX40 agonist antibody with the potential to enhance tumor-specific T-cell responsiveness, while selectively depleting intratumoral regulatory T cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3204.

Abstract 3220: A novel agonist antibody (INCAGN01876) that targets the costimulatory receptor GITR

Activation of costimulatory receptors of the tumor necrosis factor receptor (TNFR) superfamily in T cells is considered a promising alternative approach to potentiate anti-tumor immunity that may complement strategies focused on the blockade of co-inhibitory pathways such PD-1/PDL1. Glucocorticoid-induced TNFR-related protein (GITR, CD357 or TNFRSF18) is an important T cell costimulatory receptor that can potentiate T cell receptor (TCR) signaling during CD4+ and CD8+ T cell priming, effector cell differentiation and memory T cell recall responses. In humans GITR expression is generally restricted to subsets of T cells responding to TCR stimulation, and is co-expressed with OX40. Like other TNFR family members, GITR co-stimulation can enhance T cell responsiveness to suboptimal TCR signaling by activating the NFκB pathway, leading to enhanced cytokine responses and survival. GITR signaling in T cells may also promote resistance to the immune suppressive effects of regulatory T cells, thereby enhancing T cell responsiveness to weakly immunogenic tumor-associated antigens. INCAGN01876 is a humanized IgG1 monoclonal antibody being developed for the treatment of advanced malignancies. INCAGN01876 potently binds to human and non-human primate GITR but does not cross-react with related TNFR family members. INCAGN01876 has been optimized to mediate receptor forward signaling under suboptimal TCR stimulatory conditions, leading to increased production of TNFα and IFNγ by both CD4+ and CD8+ T cells. INCAGN01876 achieves this functionality by virtue of its ability to facilitate GITR clustering in TCR-stimulated T lymphocytes. In mouse preclinical tumor models, GITR was found to be selectively overexpressed by intratumoral regulatory T cells, a finding that was also observed in primary human tumor samples from diverse tumor types. In mouse models, this feature enabled a surrogate anti-GITR antibody to co-engage activating Fcγ receptors expressed by tumor-associated effector cells, and mediate the selective depletion of intratumoral regulatory T cells. Consistent with this, INCAGN01876 was designed to co-engage activating Fcγ receptors and was shown to efficiently mediate immune effector cell mechanisms, including ADCC and ADCP. Taken together, the biophysical and functional attributes of INCAGN01876 make it ideally suited for clinical development, both as a single agent and in combination with other immunomodulatory agents.

Citation Format: Ana Maria Gonzalez, Ekaterina Breous, Mariana L. Manrique, David Savitsky, Jeremy Waight, Randi Gombos, Yuqi Liu, Shiwen Lin, Olivier Leger, Volker Seibert, Takemasa Tsuji, Taha Merghoub, Sadna Budha, Roberta Zappasodi, Gerd Ritter, Jedd Wolchok, Peggy Scherle, Gregory Hollis, Reid Huber, Marc Van Dijk, Robert Stein, Nicholas Wilson. A novel agonist antibody (INCAGN01876) that targets the costimulatory receptor GITR. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3220.

Abstract B191: Preclinical assessment of targeting the PI3K/AKT pathway in combination with other signal transduction pathway inhibitors

Inhibitors targeting the phosphoinositide 3-kinase (PI3K)/serine-threonine protein kinase B (AKT) pathway have been developed and have shown efficacy in inhibiting tumor growth both in preclinical models and in the clinic. The effectiveness of PI3K/AKT inhibitors, however, is attenuated by the activation of alternative signaling pathways. Conversely, the PI3K/AKT pathway is considered to be a resistance mechanism for other therapeutic or cytotoxic agents. Therefore, understanding these mechanisms may help to inform the most optimal combinations for advancement into clinical studies. Here, we explored the potential of targeting the JAK/STAT or PIM signaling pathways in combination with a novel, potent and selective AKT inhibitor, INCB047775. Consistent with published data, pharmacological inhibition of AKT by INCB047775 caused the upregulation of PIM kinases. The combined therapies of PIM inhibition and AKT inhibition exhibited significant synergistic anti-tumor effects. Combination of PIM inhibition with AKT inhibition resulted in synergistic induction of apoptosis in cancer cells. Similarly, the combination of JAK tyrosine kinase inhibition with INCB047775 exerted synergistic inhibition of the proliferation of multiple myeloma cell lines. Similar data were observed with an inhibitor of PI3Kδ in combination with both PIM and JAK inhibition, demonstrating significant crosstalk between the PI3K/AKT pathway and other critical signaling pathways. These data provide the rationale for combinatorial therapies with inhibitors targeting JAK or PIM kinases with PI3K/AKT pathway inhibitors in the clinic.

Citation Format: Sang Hyun Lee, Holly Koblish, Xiangdong Liu, Haifen Ye, Jun Li, Xuesong Liu, Melody Diamond, Yue Zhang, Leslie Hall, Valerie Dostalik, Margaret Favata, Elham Behshad, Richard Wynn, Yun-long Li, Andrew Combs, Chu-Bio Xue, Wenqing Yao, Gregory Hollis, Reid Huber, Peggy Scherle. Preclinical assessment of targeting the PI3K/AKT pathway in combination with other signal transduction pathway inhibitors. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B191.

Abstract C103: The combination of PI3kδ-selective inhibition and immunomodulation shows efficacy in solid tumor models

Understanding the in vivo responses to immunoregulatory agents provides a basis for building more efficacious combination regimens. Pharmacologic inhibition of the oncogenic PI3Kδ pathway has been shown to be active in patients with hematopoietic malignancies. Recently, genetic inactivation of PI3Kδ in mice was shown to delay the growth of solid tumors, through the inactivation of Treg-mediated suppression of cytotoxic CD8+ T cell responses, suggesting that it may have additional utility in this patient population. We identified a similar immunomodulatory role for the PI3Kδ-selective inhibitor INCB050465 in a preclinical model of pancreatic cancer, where an increase in the number of CD8+ T cells, a decrease in the number of suppressor cells and efficacy were seen. Therefore we explored the potential of INCB050465 in additional preclinical solid tumor models, alone and in combination with other immunotherapeutic agents. INCB050465 inhibited tumor growth in multiple established tumor models which are not dependent upon oncogenic PI3K signaling. Tumor growth inhibition was not observed in these models in immunocompromised mice, demonstrating that the anti-tumor effects of these agents require an intact immune system. To further investigate immune-mediated mechanisms, tumors were analyzed for modulation of gene expression and immune phenotype after mice received short-term treatment. INCB050465 was shown to significantly downregulate the T cell gene signature in tumors, and this was primarily due to depletion of CD4+CD25+FoxP3+ regulatory T cells. As seen previously, the number of CD8+ T cells was shown to be higher in INCB050465-treated tumors. The combination of PI3Kδ and JAK inhibition resulted in enhanced activity in a T-cell-inflamed model by reducing both Treg and M2 macrophages, which promotes re-activation of both CD4+ and CD8+ T cells. In addition, PI3Kδ inhibition and PD-L1 blockade resulted in enhanced efficacy by depleting Treg and prolonging T cell response over time. In summary, pharmacological inhibition of PI3Kδ can enhance anti-tumor immunity by depleting Treg while increasing the numbers of cytotoxic CD8+ T cells. These data support clinical evaluation of the mechanism, and further studies to understand the molecular basis of efficacy and complex cellular responses may provide rationale to identify individuals who may benefit from PI3Kδ inhibitor-based immunotherapy combinations in the clinic.

Citation Format: Holly K. Koblish, Liang-Chuan Wang, Michael Hansbury, Yue Zhang, Gengjie Yang, Timothy Burn, Paul Waeltz, Mark Rupar, Eddy Yue, Brent Douty, Thomas Maduskuie, Nikoo Falahatpisheh, Yun-long Li, Andrew Combs, Gregory Hollis, Reid Huber, Peggy Scherle. The combination of PI3kδ-selective inhibition and immunomodulation shows efficacy in solid tumor models. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C103.

Abstract 771: Preclinical characterization of the selective FGFR inhibitor INCB054828

Aberrant signaling through Fibroblast Growth Factor Receptors (FGFR) has been reported in multiple types of human cancers. Genomic analyses of squamous cell lung, gastric and urothelial tumors have revealed recurrent genetic alterations in FGFR1, FGFR2 and FGFR3 genes, respectively. FGFR proteins contribute to the development of malignancies by promoting tumor cell proliferation, survival, and migration and supporting angiogenesis. Therefore targeting FGFR kinases may provide therapeutic benefit to patients with cancers that have genetic alterations in genes encoding components of the FGF-FGFR axis. INCB054828 is a potent inhibitor of FGFR1, FGFR2, and FGFR3 that has selective pharmacological activity against cancer cells with FGFR alterations.

In vitro, INCB054828 potently inhibited the kinase activity of recombinant FGFR1, FGFR2 and FGFR3 enzymes and was highly selective against a panel of kinases including VEGFR2. In cellular assays, INCB054828 inhibited the autophosphorylation of FGFR proteins with low nanomolar IC50 values and blocked signal transduction by FGFR to downstream markers of pathway activation. Cancer cell lines that have genetic alterations in FGFR1, FGFR2 and FGFR3 were uniquely sensitive to growth inhibition by INCB054828, with IC50 values generally in the range of 3-50 nM, compared with cancer cell lines or normal cells without FGFR dependence (IC50 > 1500 nM). In vivo, once-daily oral administration of INCB054828 inhibited the growth of tumors that are dependent upon FGFR1, FGFR2 and FGFR3 activity at tolerated doses. Suppression of tumor growth was dose-dependent and correlated with pharmacodynamic inhibition of FGFR. Collectively, these preclinical studies demonstrate that INCB054828 potently and selectively inhibits models of FGFR-dependent cancers in vitro and in vivo, supporting the compound's clinical evaluation in patients harboring oncogenic FGFR activation.

Citation Format: Phillip CC Liu, Liangxing Wu, Holly Koblish, Kevin Bowman, Yue Zhang, Ronald Klabe, Lynn Leffet, Darlise DiMatteo, Mark Rupar, Karen Gallagher, Michael Hansbury, Colin Zhang, Chunhong He, Paul Collier, Maryanne Covington, Richard Wynn, Swamy Yeleswaram, Kris Vaddi, Timothy Burn, Wenqing Yao, Reid Huber, Peggy Scherle, Gregory Hollis. Preclinical characterization of the selective FGFR inhibitor INCB054828. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 771. doi:10.1158/1538-7445.AM2015-771

Abstract 691: Activity of the BET inhibitor INCB054329 in models of multiple myeloma

Multiple myeloma (MM) is a disease of plasma cell transformation. Current therapy for MM is initially effective, but nearly all tumors relapse, making new therapeutic options a necessity. Due to their efficacy in MM models, small molecule inhibitors of Bromodomain and Extra Terminal (BET) proteins have generated much interest as potential therapeutic agents for MM. Efficacy from BET inhibitors in MM is thought to be driven by their ability to reduce transcript levels of the c-myc oncogene. Current MM standard of care (SoC) therapeutics include lenalidomide (Revlimid, Celgene), bortezomib (Velcade, Takeda), and Melphalan (Alkeran, GlaxoSmithKline). In preparation for potential clinical studies, these MM SoC agents were each combined with a potent pan-BET inhibitor, INCB054329, for in vitro and in vivo studies. In vitro, treatment of MM cell lines with INCB054329 inhibited expression of c-MYC, induced HEXIM1 levels and inhibited cell growth with potencies less than 200 nM. Combination of INCB054329 with SoC therapeutics showed synergistic effects in blocking MM cell proliferation. INA-6 and MM1.S mouse xenograft models of MM were utilized to study the effects of the combination of INCB054329 with the MM SoC agents in vivo. In each instance (INCB054329/lenalidomide, INCB054329/bortezomib, INCB054329/melphalan), additive to synergistic effects, as measured by inhibition of subcutaneous tumor growth, were seen in both models of MM. Since lenalidomide has recently been shown to bind the ubiquitin ligase cereblon (CRBN), leading to the degradation of two Ikaros family members, IKZF1 and IKZF3, that are essential to B cell fate and survival, we examined whether there could be functional overlap between BET inhibition and the downstream effects of lenalidomide. From MM1.S xenograft pharmacodynamic assays, we found a synergistic repression of c-MYC protein levels at 3hr post dose for the combination of INCB054329 and lenalidomide. Interestingly, the sharp decline in c-MYC protein levels in the MM1.S model appears to be independent of the IRF4 pathway, as IRF4 protein levels do not decrease until 24 hrs post dose of lenalidomide. Overall, our data indicate that INCB054329 may provide a novel combination partner with current standard of care therapies for MM, and support the clinical evaluation of the compound within the anti-myeloma treatment landscape.

Citation Format: Matthew Stubbs, Xiaoming Wen, Valerie Dostalik, Sybil O'Connor, Eian Caulder, Alla Vogina, Thomas Maduskuie, Richard Sparks, Taisheng Huang, Nikoo Falahatpisheh, Padmaja Polam, Chu-Biao Xue, Xuesong M. Liu, Timothy Burn, Kris Vaddi, Andrew P. Combs, Reid Huber, Gregory Hollis, Peggy Scherle, Phillip CC Liu. Activity of the BET inhibitor INCB054329 in models of multiple myeloma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 691. doi:10.1158/1538-7445.AM2015-691

Abstract 3525: The BET inhibitor INCB054329 is efficacious as a single agent or in combination with targeted agents in colorectal cancer models

The Bromodomain and extra-terminal (BET) family of proteins consists of BRD2, BRD3, BRD4 and BRDT. Each BET protein contains two bromodomains (BD1 and BD2) that recognize acetylated histones at enhancer and promoter regions of a select number of genes. BET proteins function as transcriptional regulators that are critical for the expression of oncogenes such as c-Myc; thus, BET proteins are important for cancer cell proliferation and survival. We have identified INCB054329, a potent and selective BET protein inhibitor that targets BD1 and BD2 of BRD2, BRD3 and BRD4. In this study, we characterized the pharmacology of INCB054329 in solid tumor cell lines. In a panel of colon cancer cell lines, more than 50% are sensitive to INCB054329 treatment with IC50 values below 500 nM in cell proliferation assays. INCB054329 down-regulated c-Myc expression, and induced cell cycle arrest and apoptosis in sensitive colon cancer cell lines. Moreover, INCB54329 was efficacious in the RKO colon cancer xenograft model. To understand whether BRD inhibition would synergize with other signaling pathway inhibitors and standard of care agents for colon cancer, we employed a high throughput combination screening strategy. Several combinations were active in a panel of colon cancer cell lines and demonstrated synergistic interactions based on combination index values. As an example, strong synergy was observed between INCB054329 and MEK inhibitors. The combination of INCB054329 and MEK inhibitors synergistically blocked expression of c-Myc protein and inhibited the MEK/ERK signaling pathway. Our data suggest the potential utilization of INCB054329 as a single agent or in combination with other targeted therapies for the treatment of colon cancer.

Citation Format: Xuesong Liu, Jun Li, Xin He, Matthew Stubbs, Margaret Favata, Xiaoming Wen, Hong Chang, Beth R. Rumberger, Yanlong Li, Thomas Maduskuie, Richard Sparks, Nikoo Falahatpisheh, Padmaja Polam, Andrew P. Combs, Reid Huber, Gregory Hollis, Peggy Scherle, Phillip C. Liu. The BET inhibitor INCB054329 is efficacious as a single agent or in combination with targeted agents in colorectal cancer models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3525. doi:10.1158/1538-7445.AM2015-3525

The Janus kinase 2 inhibitor fedratinib inhibits thiamine uptake: a putative mechanism for the onset of Wernicke's encephalopathy

The clinical development of fedratinib, a Janus kinase (JAK2) inhibitor, was terminated after reports of Wernicke's encephalopathy in myelofibrosis patients. Since Wernicke's encephalopathy is induced by thiamine deficiency, investigations were conducted to probe possible mechanisms through which fedratinib may lead to a thiamine-deficient state. In vitro studies indicate that fedratinib potently inhibits the carrier-mediated uptake and transcellular flux of thiamine in Caco-2 cells, suggesting that oral absorption of dietary thiamine is significantly compromised by fedratinib dosing. Transport studies with recombinant human thiamine transporters identified the individual human thiamine transporter (hTHTR2) that is inhibited by fedratinib. Inhibition of thiamine uptake appears unique to fedratinib and is not shared by marketed JAK inhibitors, and this observation is consistent with the known structure-activity relationship for the binding of thiamine to its transporters. The results from these studies provide a molecular basis for the development of Wernicke's encephalopathy upon fedratinib treatment and highlight the need to evaluate interactions of investigational drugs with nutrient transporters in addition to classic xenobiotic transporters.

Validation of standards for quantitative assessment of JAK2 c.1849G>T (p.V617F) allele burden analysis in clinical samples

The substitution of valine with phenylalanine at amino acid 617 of the Janus kinase 2 (JAK2) gene (JAK2 p.V617F) occurs in a high proportion of patients with myeloproliferative neoplasms (MPNs). The ability to accurately measure JAK2 p.V617F allele burden is of great interest given the diagnostic relevance of the mutation and the ongoing clinical evaluation of JAK inhibitors. A main hurdle in developing quantitative assays for allele burden measurement is the unavailability of accurate standards for both assay validation and use in a standard curve for quantification. We describe our approach to the validation of standards for quantitative assessment of JAK2 p.V617F allele burden in clinical MPN samples. These standards were used in two JAK2 p.V617F assays, which were used to support clinical studies of ruxolitinib (Jakafi(®)) in myelofibrosis, a real-time polymerase chain reaction assay for initial screening of all samples, and a novel single-nucleotide polymorphism typing (SNaPshot)-based assay for samples with less than 5% mutant allele burden. Comparisons of allele burden data from clinical samples generated with these assays show a high degree of concordance with each other and with a pyrosequencing-based assay used for clinical reporting from an independent laboratory, thus providing independent validation to the accuracy of these standards.

Identification and characterization of INCB9471, an allosteric noncompetitive small-molecule antagonist of C-C chemokine receptor 5 with potent inhibitory activity against monocyte migration and HIV-1 infection

C-C chemokine receptor 5 (CCR5) is a clinically proven target for inhibition of HIV-1 infection and a potential target for various inflammatory diseases. In this article, we describe 5-[(4-{(3S)-4-[(1R,2R)-2-ethoxy-5-(trifluoromethyl)-2,3-dihydro-1H-inden-1-yl]-3-methylpiperazin-1-yl}-4-methylpiperidin-1-yl)carbonyl]-4,6-dimethylpyrimidine dihydrochloride (INCB9471), a potent and specific inhibitor of human CCR5 that has been proven to be safe and efficacious in viral load reduction in phase I and II human clinical trails. INCB9471 was identified using a primary human monocyte-based radioligand competition binding assay. It potently inhibited macrophage inflammatory protein-1β-induced monocyte migration and infection of peripheral blood mononuclear cells by a panel of R5-HIV-1 strains. The results from binding and signaling studies using incremental amounts of INCB9471 demonstrated INCB9471 as a noncompetitive CCR5 inhibitor. The CCR5 residues that are essential for interaction with INCB9471 were identified by site-specific mutagenesis studies. INCB9471 rapidly associates with but slowly dissociates from CCR5. When INCB9471 was compared with three CCR5 antagonists that had been tested in clinical trials, the potency of INCB9471 in blocking CCR5 ligand binding was similar to those of 4,6-dimethyl-5-{[4-methyl-4-((3S)-3-methyl-4-{(1R0-2-(methyloxy)-1-[4-(trifluoromethyl) phenyl]ethyl}-1-piperazingyl)-1-piperidinyl]carbonyl}pyrimidine (SCH-D; vicriviroc), 4-{[4-({(3R)-1-butyl-3-[(R)-cyclohexyl(hydroxyl)methyl]-2, 5-dioxo-1,4,9-triazaspiro[5.5]undec-9-yl}methyl)phenyl]oxy}benzoic acid hydrochloride (873140; aplaviroc), and 4,4-difluoro-N-((1S)-3-{(3-endo)-3-[3-methyl-5-(1-methylethyl)-4H-1,2,4-triazol-4-yl]-8-azabicyclo[3.2.1]oct-8-yl}-1-phenylpropyl)cyclohexanecarboxamide (UK427857; maraviroc). Its inhibitory activity against CCR5-mediated Ca(2+) mobilization was also similar to those of SCH-D and 873140. Further analysis suggested that INCB9471 and UK427857 may have different binding sites on CCR5. The significance of two CCR5 antagonists with different binding sites is discussed in the context of potentially overcoming drug-resistant HIV-1 strains.

11β-Hydroxysteroid dehydrogenase type 1 inhibition in type 2 diabetes mellitus

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) catalyses the intracellular conversion of inert cortisone to physiologically active cortisol, functioning to enhance local cortisol action beyond what would be predicted based on simple plasma exposures. Adipose tissue overexpression of 11β-HSD1 in rodents to levels observed in human obesity can lead to a near complete metabolic syndrome phenotype, and inhibition of 11β-HSD1 has been proposed to be of potential therapeutic benefit to patients with type 2 diabetes mellitus (T2DM). Recently published clinical results with the selective 11β-HSD1 inhibitor, INCB13739, have, for the first time, provided evidence substantiating this hypothesis, and suggest that 11β-HSD1 activity may be important in regulating glycaemia and cardiometabolic risk. In patients with T2DM failing metformin monotherapy, INCB13739 treatment achieves significant reductions in haemoglobin A1c (HbA1c) and fasting plasma glucose (FPG), and when present improves hyperlipidaemia and hypertriglyceridaemia. Interestingly, these positive effects are observed primarily in subjects categorized as obese (body mass index, BMI > 30 kg/m²) and not in subjects categorized as overweight (BMI ≤ 30 kg/m²), underscoring the likely importance of adipose tissue 11β-HSD1 activity to the cardiometabolic sequelae of obesity. This review summarizes the therapeutic rationale for 11β-HSD1 inhibition, and describes in detail the metabolic and endocrinologic changes observed in patients with T2DM treated with INCB13739.

Discovery of INCB9471, a Potent, Selective, and Orally Bioavailable CCR5 Antagonist with Potent Anti-HIV-1 Activity

To identify a CCR5 antagonist as an HIV-1 entry inhibitor, we designed a novel series of indane derivatives based on conformational considerations. Modification on the indane ring led to the discovery of compound 22a (INCB9471) that exhibited high affinity for CCR5, potent anti-HIV-1 activity, high receptor selectivity, excellent oral bioavailability, and a tolerated safety profile. INCB9471 has entered human clinical trials.

The 11-beta-hydroxysteroid dehydrogenase type 1 inhibitor INCB13739 improves hyperglycemia in patients with type 2 diabetes inadequately controlled by metformin monotherapy

OBJECTIVE

11-Beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) converts inactive cortisone into active cortisol, thereby amplifying intracellular glucocorticoid action. The efficacy and safety of the 11betaHSD1 inhibitor INCB13739 were assessed when added to ongoing metformin monotherapy in patients with type 2 diabetes exhibiting inadequate glycemic control (A1C 7-11%).

RESEARCH DESIGN AND METHODS

This double-blind placebo-controlled paralleled study randomized 302 patients with type 2 diabetes (mean A1C 8.3%) on metformin monotherapy (mean 1.5 g/day) to receive one of five INCB13739 doses or placebo once daily for 12 weeks. The primary end point was the change in A1C at study end. Other end points included changes in fasting glucose, lipids, weight, adverse events, and safety.

RESULTS

After 12 weeks, 200 mg of INCB13739 resulted in significant reductions in A1C (-0.6%), fasting plasma glucose (-24 mg/dl), and homeostasis model assessment-insulin resistance (HOMA-IR) (-24%) compared with placebo. Total cholesterol, LDL cholesterol, and triglycerides were all significantly decreased in hyperlipidemic patients. Body weight decreased relative to placebo after INCB13739 therapy. A reversible dose-dependent elevation in adrenocorticotrophic hormone, generally within the normal reference range, was observed. Basal cortisol homeostasis, testosterone in men, and free androgen index in women were unchanged by INCB13739. Adverse events were similar across all treatment groups.

CONCLUSIONS

INCB13739 added to ongoing metformin therapy was efficacious and well tolerated in patients with type 2 diabetes who had inadequate glycemic control with metformin alone. 11BetaHSD1 inhibition offers a new potential approach to control glucose and cardiovascular risk factors in type 2 diabetes.

Combined inhibition of Janus kinase 1/2 for the treatment of JAK2V617F-driven neoplasms: selective effects on mutant cells and improvements in measures of disease severity

PURPOSE

Deregulation of the Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway is a hallmark for the Philadelphia chromosome-negative myeloproliferative diseases polycythemia vera, essential thrombocythemia, and primary myelofibrosis. We tested the efficacy of a selective JAK1/2 inhibitor in cellular and in vivo models of JAK2-driven malignancy.

EXPERIMENTAL DESIGN

A novel inhibitor of JAK1/2 was characterized using kinase assays. Cellular effects of this compound were measured in cell lines bearing the JAK2V617F or JAK1V658F mutation, and its antiproliferative activity against primary polycythemiavera patient cells was determined using clonogenic assays. Antineoplastic activity in vivo was determined using a JAK2V617F-driven xenograft model, and effects of the compound on survival, organomegaly, body weight, and disease-associated inflammatory markers were measured.

RESULTS

INCB16562 potently inhibited proliferation of cell lines and primary cells from PV patients carrying the JAK2V617F or JAK1V658F mutation by blocking JAK-STAT signaling and inducing apoptosis. In vivo, INCB16562 reduced malignant cell burden, reversed splenomegaly and normalized splenic architecture, improved body weight gains, and extended survival in a model of JAK2V617F-driven hematologic malignancy. Moreover, these mice suffered from markedly elevated levels of inflammatory cytokines, similar to advanced myeloproliferative disease patients, which was reversed upon treatment.

CONCLUSIONS

These data showed that administration of the dual JAK1/2 inhibitor INCB16562 reduces malignant cell burden, normalizes spleen size and architecture, suppresses inflammatory cytokines, improves weight gain, and extends survival in a rodent model of JAK2V617F-driven hematologic malignancy. Thus, selective inhibitors of JAK1 and JAK2 represent a novel therapy for the patients with myeloproliferative diseases and other neoplasms associated with JAK dysregulation.