Single-agent Treatment Research Articles

Adjuvant Chemotherapy and Outcomes in Older Adult Patients With Biliary Tract Cancer

The association of adjuvant chemotherapy (AC) with survival in the general population of patients with resected biliary tract cancer (BTC) remains controversial. As such, the role of this treatment in the treatment of older adult patients (aged ≥70 years) needs to be evaluated. To describe the patterns of use of AC and compare survival outcomes of AC and observation in older adult patients following resection of BTC. This retrospective cohort study included 8091 older adult patients with resected BTC with data available in the National Cancer Database from January 1, 2004, to December 31, 2019. Patients were divided into 2 cohorts: AC and observation. The AC cohort was subdivided into single-agent and multiagent AC treatment. Adjuvant chemotherapy vs observation following BTC resection. The primary outcome was overall survival (OS) of patients who received AC compared with observation following resection of BTC as evaluated using Kaplan-Meier estimates and multivariable Cox proportional hazards regression models. Inverse probability of treatment weighting and propensity score matching were performed to address indication bias. Between 2004 and 2019, of 8091 older adult patients with resected BTC identified (median [range] age, 77 [70-90] years; 5136 women [63.5%]; 2955 men [36.5%]), only one-third (2632 [32.5%]) received AC. There was an increase in the use of AC across the study period from 20.7% (n = 495) in 2004 to 2009 to 41.2% (n = 856) in 2016 to 2019. Age 80 years or older (odds ratio, 0.29; 95% CI, 0.25-0.33; P < .001) and gallbladder primary site (odds ratio, 0.71; 95% CI, 0.61-0.83; P < .001) were associated with a lower odds of AC. Following inverse probability of treatment weighting, as a composite, AC was not associated with improved survival (median OS, 20.5 months; 95% CI, 19.2-21.7 months) compared with observation (median OS, 19.0 months; 95% CI, 18.1-20.3 months). A longer median OS was associated with single-agent AC (21.5 months; 95% CI, 19.9-24.0 months) but not multiagent AC (19.1 months; 95% CI, 17.5-21.1 months) compared with observation (median OS, 17.3 months; 95% CI, 16.1-18.4 months). This improvement in OS with single-agent AC was not apparent on multivariable analysis (hazard ratio [HR], 0.97; 95% CI, 0.89-1.05; P = .44). However, age at diagnosis of 80 years or older (HR, 1.35; 95% CI, 1.28-1.42; P < .001) and treatment at nonacademic centers (HR, 1.14; 95% CI, 1.07-1.20, P < .001) were associated with worse OS. In this cohort study of older adult patients, AC was not associated with an improvement in survival compared with observation following BTC resection. These findings suggest the need for further study of AC for older adult patients who may benefit after curative intent surgery for BTC.

Vertical pathway inhibition of receptor tyrosine kinases and BAD with synergistic efficacy in triple negative breast cancer

Aberrant activation of the PI3K/AKT signaling axis along with the sustained phosphorylation of downstream BAD is associated with a poor outcome of TNBC. Herein, the phosphorylated to non-phosphorylated ratio of BAD, an effector of PI3K/AKT promoting cell survival, was observed to be correlated with worse clinicopathologic indicators of outcome, including higher grade, higher proliferative index and lymph node metastasis. The structural optimization of a previously reported inhibitor of BAD-Ser99 phosphorylation was therefore achieved to generate a small molecule inhibiting the phosphorylation of BAD at Ser99 with enhanced potency and improved oral bioavailability. The molecule 2-((4-(2,3-dichlorophenyl)piperazin-1-yl)(pyridin-3-yl)methyl) phenol (NCK) displayed no toxicity at supra-therapeutic doses and was therefore assessed for utility in TNBC. NCK promoted apoptosis and G0/G1 cell cycle arrest of TNBC cell lines in vitro, concordant with gene expression analyses, and reduced in vivo xenograft growth and metastatic burden, demonstrating efficacy as a single agent. Additionally, combinatorial oncology compound library screening demonstrated that NCK synergized with tyrosine kinase inhibitors (TKIs), specifically OSI-930 or Crizotinib in reducing cell viability and promoting apoptosis of TNBC cells. The synergistic effects of NCK and TKIs were also observed in vivo with complete regression of a percentage of TNBC cell line derived xenografts and prevention of metastatic spread. In patient-derived TNBC xenograft models, NCK prolonged survival times of host animals, and in combination with TKIs generated superior survival outcomes to single agent treatment. Hence, this study provides proof of concept to further develop rational and mechanistic based therapeutic strategies to ameliorate the outcome of TNBC.

Beyond PD(L)-1 Blockade in Microsatellite-Instable Cancers: Current Landscape of Immune Co-Inhibitory Receptor Targeting.

High microsatellite instability (MSI-H) derives from genomic hypermutability due to deficient mismatch repair function. Colorectal (CRC) and endometrial cancers (EC) are the tumor types that more often present MSI-H. Anti-PD(L)-1 antibodies have been demonstrated to be agnostically effective in patients with MSI-H cancer, but 50-60% of them do not respond to single-agent treatment, highlighting the necessity of expanding their treatment opportunities. Ipilimumab (anti-CTLA4) is the only immune checkpoint inhibitor (ICI) non-targeting PD(L)-1 that has been approved so far by the FDA for MSI-H cancer, namely, CRC in combination with nivolumab. Anti-TIM3 antibody LY3321367 showed interesting clinical activity in combination with anti-PDL-1 antibody in patients with MSI-H cancer not previously treated with anti-PD(L)-1. In contrast, no clinical evidence is available for anti-LAG3, anti-TIGIT, anti-BTLA, anti-ICOS and anti-IDO1 antibodies in MSI-H cancers, but clinical trials are ongoing. Other immunotherapeutic strategies under study for MSI-H cancers include vaccines, systemic immunomodulators, STING agonists, PKM2 activators, T-cell immunotherapy, LAIR-1 immunosuppression reversal, IL5 superagonists, oncolytic viruses and IL12 partial agonists. In conclusion, several combination therapies of ICIs and novel strategies are emerging and may revolutionize the treatment paradigm of MSI-H patients in the future. A huge effort will be necessary to find reliable immune biomarkers to personalize therapeutical decisions.

Dual TTK/PLK1 inhibition has potent anticancer activity in TNBC as monotherapy and in combination.

Threonine tyrosine kinase (TTK) and polo-like kinase 1 (PLK1) are common essential kinases that collaborate in activating the spindle assembly checkpoint (SAC) at the kinetochore, ensuring appropriate chromosome alignment and segregation prior to mitotic exit. Targeting of either TTK or PLK1 has been clinically evaluated in cancer patients; however, dual inhibitors have not yet been pursued. Here we present the in vitro and in vivo characterization of a first in class, dual TTK/PLK1 inhibitor (BAL0891). Mechanism of action studies utilized biochemical kinase and proteomics-based target-engagement assays. Cellular end-point assays included immunoblot- and flow cytometry-based cell cycle analyses and SAC integrity evaluation using immunoprecipitation and immunofluorescence approaches. Anticancer activity was assessed in vitro using cell growth assays and efficacy was evaluated, alone and in combination with paclitaxel and carboplatin, using mouse models of triple negative breast cancer (TNBC). BAL0891 elicits a prolonged effect on TTK, with a transient activity on PLK1. This unique profile potentiates SAC disruption, forcing tumor cells to aberrantly exit mitosis with faster kinetics than observed with a TTK-specific inhibitor. Broad anti-proliferative activity was demonstrated across solid tumor cell lines in vitro. Moreover, intermittent intravenous single-agent BAL0891 treatment of the MDA-MB-231 mouse model of TNBC induced profound tumor regressions associated with prolonged TTK and transient PLK1 in-tumor target occupancy. Furthermore, differential tumor responses across a panel of thirteen TNBC patient-derived xenograft models indicated profound anticancer activity in a subset (~40%). Using a flexible dosing approach, pathologically confirmed cures were observed in combination with paclitaxel, whereas synergy with carboplatin was schedule dependent. Dual TTK/PLK1 inhibition represents a novel approach for the treatment of human cancer, including TNBC patients, with a potential for potent anticancer activity and a favorable therapeutic index. Moreover, combination approaches may provide an avenue to expand responsive patient populations.

Dual role of CD73 as a signaling molecule and adenosine-generating enzyme in colorectal cancer progression and immune evasion.

Metastasis and limited benefits of immune checkpoint blockade are two obstacles to the battle against colorectal cancer (CRC). CD73, encoded by the gene 5'-Nucleotidase Ecto (NT5E), is a major enzyme that generates extracellular adenosine. However, whether CD73 affects cancer progression and immune response in CRC remains unclear. Here, the clinical significance of CD73 was assessed in human CRC specimens using immunohistochemistry and bioinformatic analyses. We demonstrated that CD73 is elevated in CRC tissues, particularly in those with metastasis, and correlates with poor prognosis. Gain- and loss-of-function experiments demonstrate that tumor CD73 supports tumor progression and impairs the viability and effector functions of CD8+ T cells. Targeting CD73 on CRC cells reduces their malignant phenotypes and improves the anti-cancer response of CD8+ T cells in the tumor microenvironment (TME). Moreover, the combination of CD73 blockade and PD-1 inhibitors exhibited enhanced anti-cancer effects when compared to a single-agent treatment. Thus, CD73 may be a promising target in the treatment of CRC.

An In Silico Platform to Predict Cardiotoxicity Risk of Anti-tumor Drug Combination with hiPSC-CMs Based In Vitro Study

ObjectiveAntineoplastic agent-induced systolic dysfunction is a major reason for interruption of anticancer treatment. Although targeted anticancer agents infrequently cause systolic dysfunction, their combinations with chemotherapies remarkably increase the incidence. Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) provide a potent in vitro model to assess cardiovascular safety. However, quantitatively predicting the reduction of ejection fraction based on hiPSC-CMs is challenging due to the absence of the body's regulatory response to cardiomyocyte injury.MethodsHere, we developed and validated an in vitro-in vivo translational platform to assess the reduction of ejection fraction induced by antineoplastic drugs based on hiPSC-CMs. The translational platform integrates drug exposure, drug-cardiomyocyte interaction, and systemic response. The drug-cardiomyocyte interaction was implemented as a mechanism-based toxicodynamic (TD) model, which was then integrated into a quantitative system pharmacology-physiological-based pharmacokinetics (QSP-PBPK) model to form a complete translational platform. The platform was validated by comparing the model-predicted and clinically observed incidence of doxorubicin and trastuzumab-induced systolic dysfunction.ResultsA total of 33,418 virtual patients were incorporated to receive doxorubicin and trastuzumab alone or in combination. For doxorubicin, the QSP-PBPK-TD model successfully captured the overall trend of systolic dysfunction incidences against the cumulative doses. For trastuzumab, the predicted incidence interval was 0.31–2.7% for single-agent treatment and 0.15–10% for trastuzumab-doxorubicin sequential treatment, covering the observations in clinical reports (0.50–1.0% and 1.5–8.3%, respectively).ConclusionsIn conclusion, the in vitro-in vivo translational platform is capable of predicting systolic dysfunction incidence almost merely depend on hiPSC-CMs, which could facilitate optimizing the treatment protocol of antineoplastic agents.

The ERK inhibitor LY3214996 augments anti-PD-1 immunotherapy in preclinical mouse models of BRAFV600E melanoma brain metastasis.

Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment; however, only a subset of patients with brain metastasis (BM) respond to ICI. Activating mutations in the mitogen-activated protein kinase signaling pathway are frequent in BM. The objective of this study was to evaluate whether therapeutic inhibition of extracellular signal-regulated kinase (ERK) can improve the efficacy of ICI for BM. We used immunotypical mouse models of BM bearing dual extracranial/intracranial tumors to evaluate the efficacy of single-agent and dual-agent treatment with selective ERK inhibitor LY3214996 (LY321) and anti-programmed death receptor 1 (PD-1) antibody. We verified target inhibition and drug delivery, then investigated treatment effects on T-cell response and tumor-immune microenvironment using high-parameter flow cytometry, multiplex immunoassays, and T-cell receptor profiling. We found that dual treatment with LY321 and anti-PD-1 significantly improved overall survival in 2 BRAFV600E-mutant murine melanoma models but not in KRAS-mutant murine lung adenocarcinoma. We demonstrate that although LY321 has limited blood-brain barrier (BBB) permeability, combined LY321 and anti-PD-1 therapy increases tumor-infiltrating CD8+ effector T cells, broadens the T-cell receptor repertoire in the extracranial tumor, enriches T-cell clones shared by the periphery and brain, and reduces immunosuppressive cytokines and cell populations in tumors. Despite the limited BBB permeability of LY321, combined LY321 and anti-PD-1 treatment can improve intracranial disease control by amplifying extracranial immune responses, highlighting the role of extracranial tumors in driving intracranial response to treatment. Combined ERK and PD-1 inhibition is a promising therapeutic approach, worthy of further investigation for patients with melanoma BM.

Abstract A117: Evaluation of nab-sirolimus in combination with PI3K pathway inhibitors to overcome PI3K/mTOR resistance in PI3K-mutant breast cancer cell lines

Abstract Background: The PI3K-AKT-mTOR pathway is frequently activated in many cancer types and plays a central role in tumorigenesis. However, clinical use of therapies targeting this pathway is limited by compensatory vertical and horizontal feedback activation loops, which limit antitumor efficacy and lead to drug resistance. Combination therapy strategies employing simultaneous inhibition of multiple PI3K-AKT-mTOR pathway elements may overcome these resistance mechanisms and improve antitumor activity. nab-Sirolimus is a novel albumin-bound nanoparticle form of the mTOR inhibitor sirolimus that has significantly greater tumor accumulation, mTOR target suppression, and improved antitumor effects compared with conventional first generation mTOR inhibitors in preclinical models. Here, we analyzed the effects of nab-sirolimus combinations in PI3K-mutant breast cancer (BrCa) cells. Methods: PI3K mutated BrCa cell lines (MDA-MD-453, hormone receptor [HR]-; and MDA-MB-361, HR+) were incubated for 5 days with increasing concentrations of nab-sirolimus, the PI3K pathway inhibitors gedatolisib and alpelisib, or the AKT inhibitors miransertinib and capivasertib. The antiproliferative and cytotoxic effects of single agent and combination treatment were assessed using cell viability and cell death assays. Cell signaling was analyzed by western blot. Results: The antiproliferative effects of gedatolisib at low doses (2.5-10 nM) were enhanced by 61-71% in combination with nab-sirolimus (20 or 80 nM) in MDA-MB-453 cells. Limited cell death (4.2-9.6%) was observed in HR- MDA-MB-453 cells with low doses (2.5, 5, and 10 nM) of gedatolisib alone. In contrast, and despite the well-established cytostatic action of mTOR inhibitors, the addition of 20 and 80 nM nab-sirolimus led to high levels of cell death (up to 48.9%). Similar results were observed with alpelisib at 1 µM in combination with nab-sirolimus (20 or 80 nM), and also with capivasertib (1 µM) or miransertib (250 nM) combined with 80 nM nab-sirolimus. Western blot analysis demonstrated that gedatolisib or alpelisib alone each triggered upregulation of p4EBP1 whereas nab-sirolimus treatment alone activated a negative feedback loop through increased pAKT. Importantly, these compensatory feedback activation loops were both reversed by the combination of PI3K inhibitors and nab-sirolimus. Similar cell death and cell viability results were observed with nab-sirolimus plus PI3K inhibitors (gedatolisib or alpelisib) and AKT inhibitors (capivasertib or miransertib) in HR+ MDA-MB-361 cells. Conclusions: The antitumor effects of PI3K and AKT inhibitors were enhanced by the addition of the novel mTOR inhibitor nab-sirolimus. The improved effectiveness of the PI3K and mTOR inhibitor combination was due to the reciprocal overcoming of resistance mechanisms induced by single agent treatment. These data support a vertical PI3K pathway inhibition strategy using nab-sirolimus and PI3K/AKT inhibitors in PIK3CA-mutated BrCa, regardless of HR status. Citation Format: Sean Wallace, Khine Nyein Myint, Shihe Hou, Maria Zalath, Andrew Kwon, Brian McMorran, Igor Vivanco. Evaluation of nab-sirolimus in combination with PI3K pathway inhibitors to overcome PI3K/mTOR resistance in PI3K-mutant breast cancer cell lines [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A117.

Abstract A079: FHD286 is a BRG1/BRM ATPase inhibitor showing efficacy in NSCLC models and is applicable to NSCLC patients both as a single agent treatment and in combination with current standards of care

Abstract The BAF (BRG/BRM-associated factors) complex plays a critical role in shaping the chromatin landscape. The two mutually exclusive ATPases BRM/BRG1 (SMARCA2/4, respectively) drive chromatin remodeling activity in the BAF complex. Genetic alterations in the SMARCA4 gene, encoding BRG1, are found in approximately 10% of non-small cell lung cancer (NSCLC) patients, leaving this subset of BRG1-deficient tumors highly susceptible to inhibition of BRM (Hoffman, 2014; Oike, 2013). However, BRG1 can also have oncogenic activity in NSCLC (Li, 2019) and can serve as a predictive biomarker for chemotherapy outcome in patients (Bell, et al 2015), rationalizing the use of a dual BRG1/BRM ATPase inhibitor (FHD286) in NSCLC patients in combination with chemotherapy. Here, we demonstrate that a panel of in vitro and in vivo NSCLC models respond to BAF ATPase inhibition as a single agent treatment, irrespective of SMARCA4 mutation status. Analysis of gene expression and dependency data suggests that FHD286 sensitivity correlates with activity of genes related to DNA damage response and repair. We furthermore demonstrate an enhancing effect on tumor growth inhibition in vitro and in vivo driven by apoptosis and cell cycle arrest when combining dual FHD286 with current first and second line standards of care. Collectively, these results indicate a path forward for the development of FHD-286, a clinical stage BRM/BRG1 ATPase inhibitor, for the treatment of NSCLC patients both as a single agent treatment and in combination with current standards of care. Citation Format: Oliver Mikse, Ammar Adam, GiNell Elliott, Dave Lahr, Victoria Amaral, Priyadharshini Viswanathan, Liv Johannessen, Hafiz Ahmad, Jessica Wan, Steven Bellon, Murphy Hentemann. FHD286 is a BRG1/BRM ATPase inhibitor showing efficacy in NSCLC models and is applicable to NSCLC patients both as a single agent treatment and in combination with current standards of care [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr A079.

Abstract B163: Discovery and characterization of OKI-219, an orally bioavailable H1047R-mutant-selective inhibitor of PI3Kα

Abstract Mutations in PI3Kα lead to constitutive activation of the PI3K/AKT/mTOR pathway and are found in approximately 13% of human cancers, with the PI3KαH1047R mutation being the most common. Targeting PI3Kα in cancer is a therapeutically proven strategy, with the currently approved drug alpelisib showing clinical efficacy alone or in combination with other therapies. However, treatment with non-mutant selective PI3Kα inhibitors, such as alpelisib, is associated with significant toxicities such as hyperglycemia due to on-target inhibition of the wild-type enzyme, which often leads to dose modification or discontinuation. Therefore, there is a significant need to develop new PI3Kα-targeted therapies that can avoid or minimize on-target toxicity and improve the safety and clinical benefit for patients. OKI-219 is a PI3KαH1047R mutant-selective inhibitor, with ~100-fold cellular selectivity for the H1047R mutation over wild-type and biochemical selectivity across a 412 kinase panel, with no other kinases showing &amp;gt;30% inhibition at 1 µM. In vitro, OKI-219 drives decreased phosphorylated AKT (pAKT) and decreased proliferation selectively in PI3KαH1047R mutant cell lines across several tumor types. In vivo, as a monotherapy, OKI-219 demonstrates dose-dependent antitumor activity in multiple human CDX and PDX tumor xenograft models, with regression rates up to 100% in PI3KαH1047R heterozygous (T47D) and homozygous (SUM185PE) CDX models, at doses that show no sign of the metabolic dysfunction (increased glucose or insulin) that is associated with wild-type protein inhibition. The in vivo antitumor activity correlates with pathway inhibition, measured by decreased pAKT in tumors. In addition to the monotherapy efficacy observed, OKI-219 in combination with the selective estrogen receptor degrader (SERD) fulvestrant showed significant combination benefit leading to tumor regressions in the H1047R-mutated ER+HER2- breast cancer model xxT47D, at doses where no regressions were observed with single agent treatment. These data support the hypothesis that OKI-219 will offer improved efficacy and a wider therapeutic window compared to non-mutant selective PI3Kα inhibitors. This hypothesis will be tested, as OKI-219 is moving into clinical investigation. Citation Format: Molly A Taylor, Qian Zhao, David Mareska, Maria Hoh, Yevgeniy Izrayelit, Kevin Litwiler, Mark L Boys, Rich Woessner, Duncan Walker, Jennifer Diamond, James D Winkler. Discovery and characterization of OKI-219, an orally bioavailable H1047R-mutant-selective inhibitor of PI3Kα [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B163.

Abstract B147: Preclinical evaluation of XPO1 inhibition with topoisomerase-I (topo-I) inhibition in colorectal cancer (CRC) cell lines and patient-derived xenograft (PDX) models

Abstract Background: Resistance to topo-I inhibitors is of significant importance in treating patients with metastatic CRC (mCRC). Selinexor and eltanexor are selective inhibitors of nuclear export, by binding to exportin 1 (XPO1, the primary nucleic export receptor, and is overexpressed in CRC). Eltanexor is an investigational XPO1 inhibitor, with similar mechanism and potency but improved tolerability in animal models. XPO1 inhibition results in nuclear localization of tumor suppressor proteins, oncoprotein mRNAs, and topoisomerases, and decreases DNA damage repair (DDR) response. Irinotecan is a topo-I inhibitor which induces DNA damage and is commonly used in mCRC. We hypothesized that XPO1 inhibition may improve response to topo-I inhibitor in mCRC by impairing the DDR response. Methods: The synergism of XPO1 inhibition (selinexor or eltanexor) with SN38 was assessed in CRC cell lines by CellTiter-Glo 2.0 and quantitated using Bliss Additivity Model using Synergy Finder 2.0. Each condition was plated either concurrent (both drugs for 72 hours) or sequential (SN38 for 24 hours then removed, followed by XPO1 inhibitor for 48 hours). Nude mice were implanted with one microsatellite stable CRC PDX model in the flanks followed by treatment with vehicle, XPO1 inhibitor, irinotecan (15 mg/kg intraperitoneal weekly), or combination. Tumor growth was measured by specific growth rate (SGR), within an IACUC-approved protocol. Tumor tissue was collected at day 7 for molecular analysis. Tissues were lysed and protein was run on 4%-12% SDS-PAGE Gel. p21 Waf/Cip and P-Histone H2A.X were used to determine DNA damage by western blot. P-Histone H2AX (pH2AX) was evaluated by immunofluorescence using primary conjugated P-Histone H2A.X antibody and DAPI for nuclear counter stain. Slides were imaged using Olympus iX83 microscope and analysis was performed using Olympus CellSens software. Results: In CRC cell lines, concurrent combination eltanexor and SN38 did not synergistically decrease viability but increased pH2AX compared to SN38 alone (~30-fold). However, sequential SN38 followed by eltanexor synergistically decreased viability at multiple dose levels; evaluation of pH2AX is ongoing. In PDX model CRC254, eltanexor (10 mg/kg and reduced to 7.5 mg/kg on day 8 to improve tolerability, orally 5 days per week) with irinotecan decreased SGR compared to irinotecan alone (SGR=0.007 vs 0.026, respectively, p=0.0003) and compared to eltanexor alone (SGR=0.029, p &amp;lt;0.0001). Combination treatment increased pH2AX and increased p21 expression compared to either single-agent treatment. Similar SGR results were observed with selinexor (5 mg/kg orally twice weekly). Conclusions: XPO1 inhibition and topo-I inhibition decreased CRC tumor growth in PDX models, presumably by increasing DNA double strand breaks. Cell line data suggests sequential dosing of topo-I inhibition followed by XPO1 inhibition may be effective. This work supports continued development of this combination in mCRC. Citation Format: Robert W Lentz, Adrian Dominguez, Stacey Bagby, Cameron Binns, Alexis Leal, Sunnie Kim, Sarah Lindsey Davis, Christopher H Lieu, Wells A Messersmith, Todd M Pitts. Preclinical evaluation of XPO1 inhibition with topoisomerase-I (topo-I) inhibition in colorectal cancer (CRC) cell lines and patient-derived xenograft (PDX) models [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B147.

Abstract A005: Synergistically Engaging a b-Selective IL-2 Agonist with PD1/PDL-1 Blockade in a Bifunctional Superkine, MDNA223

Abstract Introduction: Combination treatment with a long-acting IL-2 superkine (MDNA109FEAA-Fc; aka MDNA19) and anti-PD1 or anti-CTLA4 has shown clear evidence of synergy in blunting tumor growth. To further leverage this synergism, we designed MDNA223, a BiSKIT (Bifunctional SuperKine for ImmunoTherapy) comprising MDNA109FEAA with enhanced affinity for IL-2Rb and no binding to IL-2Ra, fused to either human or mouse anti-PD1. We present in vitro and in vivo characterization of MDNA223 and demonstrate its enhanced IL-2R agonism and effective PD1/PDL-1 blockade in multiple “hot” and “cold” syngeneic tumor models. Experimental Procedure: In vitro studies included human PBMCs and cell-based reporter assays. In vivo studies were conducted in CT26, B16F10, E0771 and TRAMP-C1 tumor models by intraperiotonneal (IP) administration. Intratumoral treatment was performed in a CT26 bilateral tumor model with or without a STING agonist. Analysis of tumor infiltrating lymphocytes (TILs) was performed using flow cytometry. Results: In studies with human PBMCs, MDNA223 showed increased p-STAT5 signaling in CD8+ T cells and reduced activity in Tregs compared to rhIL-2, consistent with its enhanced receptor selectivity. MDNA223 and anti-PD1 were similarly potent at PD1/PDL-1 blockade in a cell-based reporter assay. In mice, MDNA223 induced proliferation (based on Ki67 expression) and expansion of peripheral CD8+ T cells for over 7 days. IP treatment with MDNA223 resulted in significantly greater inhibition of CT26, B16F10, E0771 and TRAMP-C1 tumor growth when compared to combination of MDNA19 with anti-PD1 at equimolar dosage. This observation is consistent with the proposed cis-binding mechanism of MDNA223 to both, IL-2R and PD1 on the same effector immune cell. In a bilateral CT26 tumor model, IT treatment with MDNA223 not only inhibited the treated tumor but also exhibited an abscopal effect by slowing growth of the untreated tumor implanted on the opposite flank. TILs analysis of B16F10 melanoma following a single dose of MDNA223 showed increased infiltration of CD8+ T cells over Tregs compared to single agent treatment with MDNA19 or anti-PD1 as well as their combination. Treatment with MDNA223 also resulted in a larger population of functional effector CD8+ T cells expressing low levels of the Tim-3 exhaustion marker and high levels of the cytotoxic Granzyme-B protease. Conclusion: MDNA223 demonstrated superior therapeutic activity over the combination of MDNA19 and anti-PD1 in both immunologically ‘hot’ (CT26) and ‘cold’ (B16F10, E0771 and TRAMP-C1) tumor models. Additional studies with variants of MDNA223 capable of tumor selective targeting and/or conditional activation within the tumor micro-environment are in progress to maximize activity at the tumor site with tunable peripheral stimulation. Citation Format: Aanchal Sharma, Minh D To, Hardeep Kataria, Qian Liu, Rosemina Merchant, Fahar Merchant. Synergistically Engaging a b-Selective IL-2 Agonist with PD1/PDL-1 Blockade in a Bifunctional Superkine, MDNA223 [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2023 Oct 1-4; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2023;11(12 Suppl):Abstract nr A005.

Abstract C085: OPN-6602, a dual EP300/CBP bromodomain inhibitor modulates androgen-driven transcription, including MYC, in mCRPC

Abstract Metastatic castration-resistant prostate cancer (mCRPC) remains an urgent unmet medical need despite existing therapies that target androgen receptor (AR) signaling. Disease progression is commonly a result of acquired resistance to existing anti-androgen therapies. Biological models have revealed potential resistance mechanisms of CRPC through the reactivation of the AR pathway. Transcriptional coactivators CREB-binding protein (CBP) and E1A binding protein (EP300) are high value targets in mCRPC as they mediate androgen-dependent and -independent activity of the AR pathway. EP300 and CBP proteins harbor both histone acetyltransferase (HAT)- and bromo-domains, and the HAT activity of EP300 regulates AR function. EP300 bromodomain inhibition partially blocks its HAT activity, reducing AR-mediated gene expression and tumor growth. OPN-6602 and OPN-6742 are potent, selective, and orally active small molecule dual EP300/CBP bromodomain inhibitors which abrogate persistent AR signaling in CRPC by modulating H3K27 acetylation and the recruitment of EP300, AR full length (AR-FL), and AR variant 7 (AR-v7) to AR response elements. OPN-6602 and OPN-6742 obstruct the EP300 bromodomain leading to downregulation of the AR pathway and consequent anti-tumor effects in AR-dependent CRPC. OPN-6602 and OPN-6742 are highly selective (&amp;gt;100-fold) against other bromodomains based on a screening panel of 40 bromodomains. Biochemical screens using AlphaScreen technology show these compounds to be equipotent against EP300 and CBP. OPN-6602 is particularly potent by Surface Plasmon Resonance analysis, displaying a KD of 0.87 nM, with a fast association rate (1.5 E+06/Ms) and a slow dissociation rate (1.3 E-03/s). Consequently, OPN-6602 displays a noteworthy residence time of 13 minutes. Both compounds show an AR-selective mode of action with anti-proliferative activity in AR-dependent prostate cancer cell lines (e.g. VCaP, LNCaP, and 22Rv-1) but are inactive against AR-negative prostate cancer cell lines (e.g. DU145). VCaP and mCRPC patient-derived xenograft (PDX) RNA profiling provides evidence of a marked, dose-dependent, pharmacodynamic response indicative of EP300/CBP inhibition. In the VCaP xenograft model, OPN-6602 and OPN-6742 show dose-dependent tumor growth inhibition and corresponding pharmacodynamic responses with prostate-specific antigen level decreases and decreased H3K27 acetylation. In the QR (AR-v7+) PDX model of CRPC (post-androgen deprivation therapy), a synergistic effect was observed between OPN-6602 and enzalutamide. This combination further modulates the expression of AR-driven transcripts such as MYC compared to single agent treatments. The pharmacokinetic profiles of OPN-6602 and OPN-6742 are favorable for oral single daily dose administration due to a high Cmax and short half-life. Due to its higher potency, OPN-6602 has been chosen as clinical candidate and a first-in-human study will start in 2024. Citation Format: Bernice Matusow, Wayne Spevak, Chao Zhang, Yan Ma, Rafe Shellooe, Peipei Li, James Tsai, Pan- Yu Chen, Parmveer Singh, Jackie Walling, Christine Nichols, Jason Halladay, Kerry Inokuchi, Gaston Habets, Gideon Bollag. OPN-6602, a dual EP300/CBP bromodomain inhibitor modulates androgen-driven transcription, including MYC, in mCRPC [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C085.

Skp2 Inhibition Diminishes Essential Cell Survival Markers c-Maf and c-Myc, Enhancing Therapeutic Efficacy Against Drug Resistant Multiple Myeloma

Multiple Myeloma (MM) presents challenges as a hematologic malignancy, with drug resistance leading to limited curative options and disease relapse despite advancements in therapy. Understanding the molecular mechanisms driving MM's development and progression is vital for identifying new treatment approaches. Clinical and experimental evidence supports the role of S-phase kinase-associated protein 2 (Skp2) in driving the progression of several cancers, including MM. We interrogated a public microarray dataset derived from clinical specimens of MM patients and observed a significantly higher expression of Skp2 within the relapsed patient cohort (N=28) compared to the newly diagnosed group (N=63) (P=0.0041). Additionally, we observed elevated Skp2 levels and decreased P27 Kip1 levels in drug-resistant MM cell lines (MM.1R and RPMI 8226.R5) compared to their parental cell lines (MM.1S and RPMI 8226). Hence, a comprehensive understanding of Skp2's molecular functions in drug-resistant MM becomes paramount for facilitating the development of precision-targeted interventions. We investigated Skp2's molecular interactions in MM by performing a targeted knockdown with siRNA in drug-resistant and sensitive cell lines (OPM1, RPMI.8226, MM.1S, and MM.1R). Immunoblot analysis showed reduced STAT3 activation and decreased levels of cell survival markers c-Maf and c-Myc. Treatment with 10uM of the small molecule inhibitor SkpinC1 also inhibited STAT3 activation and led to significant reductions in c-Maf and c-Myc protein levels compared to the vehicle-treated groups. These findings hold immense significance as c-Maf and c-Myc are intricately associated with MM progression and poorer outcomes, although there is limited information on their regulation by the Skp2/P27 axis. Functionally, treatment of the MM cell lines with increasing dosages of SkpinC1 showed a progressive decrease in MM cell line survival, with IC50 values spanning 5-15uM, signifying the broad applicability of the inhibitor among the tested cell lines. Moreover, flow cytometry-based analysis of the surviving cell population demonstrated that SkpinC1 based inhibition of the Skp2/P27 axis considerably decreased the percentage of proliferating M-phase cells, while elevating the proportion of quiescent and apoptotic cells relative to the control group. At the molecular level, targeted inhibition of the Skp2/P27 axis by SkpinC1 caused the accumulation of cell cycle inhibitors P27 Kip1, P21 (Cip1/Waf1), and P57 Kip2, activation of the tumor suppressive TP53 protein with a simultaneous decrease in phospho-MDM2 levels in addition to an increase in the levels of apoptotic markers cleaved PARP and Caspase 3. From a clinical perspective, we also probed the applicability of Skp2 inhibition using SkpinC1 as a potential strategy for managing therapeutic resistance in MM. We treated multiple MM cell lines (OPM1, RPMI.8226, MM.1S and MM.1R) using a combination of Lenalidomide (an immune modulator) or Bortezomib (a proteasomal inhibitor) with SkpinC1 and compared it with single agent treatments. Both Lenalidomide/SkpinC1 as well as Bortezomib/SkpinC1 showed a strong dose dependent decrease in the percentage of surviving cells relative to the single agent treatments, thereby highlighting the remarkable potential of targeting the Skp2/P27 axis for clinical therapy in MM. To gain deeper insights into the molecular roles of Skp2/P27 axis inhibition by SkpinC1, we subjected drug-resistant MM.1R cells to 10uM SkpinC1 treatment for 24 hours, followed by single-cell transcriptome sequencing. This approach illuminated considerable heterogeneity between the drug-treated and control cells, accompanied by global changes in various signaling pathways associated with cell survival. In conclusion, the inhibition of Skp2 in MM cells exerts a significant impact on crucial cell survival pathways, notably c-Maf and c-Myc, thereby promoting apoptosis and offering a promising therapeutic avenue to combat drug resistance in MM. The precise targeting of Skp2 using small molecule inhibitors, such as SkpinC1, demonstrates substantial therapeutic potential, enhancing the efficacy of combinatorial treatment approaches for more effective interventions in MM.

Combination Therapy with Luspatercept and the Ferroportin Inhibitor Vamifeport Is Superior to Either Drug Alone in Improving Anemia and Reducing Myeloid Skewing in MDS

Background: Patients with myelodysplastic syndromes (MDS) are prone to develop iron overload as a consequence of ineffective erythropoiesis and chronic transfusion therapy. Although iron overload is a common feature in MDS, it has remained unclear whether and how iron excess is detrimental for MDS pathophysiology. Recently, we have shown that iron restriction by the oral ferroportin (FPN) inhibitor vamifeport improves anemia and reduces myeloid skewing, being of benefit for MDS as single treatment. Luspatercept is a recombinant fusion protein acting as TGF-β superfamily ligands trap which has recently gained FDA approval for the treatment of anemia in transfusion-dependent low-risk MDS patients. Luspatercept promotes erythropoietin (EPO)-independent maturation of late-stage erythroid cells, resulting in increased hemoglobin and red blood cells (RBCs) count. However, this drug - due to a lack of improvement in myeloid skewing and AML evolution - is considered a non-disease-modifying therapy. Aims: In this study we investigated the effect of a combined therapy using luspatercept and the FPN inhibitor vamifeport in a preclinical MDS mouse model, with the hypothesis that both drugs could have additive effects with further benefit for the disease. Methods: To this end, we administered the FPN inhibitor vamifeport in NUP98-HOXD13 MDS mice for 3 months (0.5 mg/ml into drinking water), combined with luspatercept for the last 2 months (5 mg/kg twice a week, subcutaneous injection), starting at 3 months of age. Mice receiving the combined treatment were compared to those untreated or receiving single treatments. Results: At steady-state MDS mice develop anemia, neutropenia and lymphopenia, together with an iron overload phenotype, hallmarked by inappropriately low hepcidin levels, elevated serum iron and transferrin saturation, non-transferrin-bound iron (NTBI) formation and tissue iron deposition. Vamifeport administration in MDS mice reduced serum iron and NTBI formation and prevented tissue iron loading, either as a single or combined treatment with luspatercept. Luspatercept and vamifeport, as single-agent treatment, ameliorated anemia and the maturation of bone marrow and splenic RBCs in MDS mice. The combined therapy further improved anemia compared to the treatments with either drugs alone, as suggested by the higher hemoglobin levels, hematocrit and RBC count, and the decreased number of early erythroid precursors, sign of more effective erythropoiesis. Importantly, vamifeport, but not luspatercept, significantly altered myeloid skewing in MDS, revealing a major role of the iron status in myeloid expansion. Myeloid bias, monitored as percentage of CD11b + Gr1 + myeloid cells in the bone marrow was attenuated by iron restriction in vamifeport-treated MDS mice compared to control and luspatercept-treated MDS animals. The combined treatment merkedly reduced myeloid skewing in MDS mice, similarly to the single vamifeport treatment. Furthermore, the number of immature cKit + myeloid blasts in the peripheral blood of MDS animals were decreased by vamifeport alone and in combination with luspatercept, but not by luspatercept alone. Finally, splenomegaly was reduced in MDS mice treated with vamifeport alone or in combination with luspatercept, confirming that iron restriction improves ineffective erythropoiesis and limits myeloid skewing. Overall, the combination therapy with vamifeport and luspatercept showed superior effects in improving anemia and myeloid bias as compared to single treatments. Conclusion: In conclusion, our results show that iron restriction by vamifeport enhances the erythroid maturation action of luspatercept, likely by improving iron utilization in erythroid cells and ameliorating their survival. Furthermore, vamifeport improves the myeloid skewing in the MDS model, suggesting disease-modifying activity as single agent as well as combined therapy with luspatercept. Together, these data prove that combo therapies aimed at restricting iron and boosting erythroid maturation may offer additive beneficial effects in MDS and provide pre-clinical evidence for combining iron restriction and TFG-β superfamily ligand-trap approaches as more effective therapeutic strategies for the treatment of MDS.

Variable Response of MLL-Rearranged Leukemia Cell Lines to Combinations of Menin, CDK9 and DOT1L Inhibitors

Background: MLL (Mixed Lineage Leukemia) rearrangements occur in approximately 10% of leukemias. Infant leukemia has a higher frequency of MLL rearrangement (MLL-r) than leukemia in other age groups. Despite intensified treatment in infant leukemia, outcomes remain poor. MLL-r leukemia depends on the interaction of MLL fusions with menin, DOT1L, and CDK9. Single-agent treatment with menin, DOT1L, and CDK9 inhibitors has shown promising results in preclinical studies, but their clinical efficacy has been limited by primary and acquired resistance. We hypothesized that combination therapy targeting multiple regulators, including menin, DOT1L, and CDK9, would provide a more effective treatment of MLL-r leukemia. Methods: We performed cell viability experiments on leukemia cell lines (MV4;11, MOLM13, RS4;11, THP1, SEM, KOPN8, NOMO1, HL60, ML2) with single, two and three drug combinations using a menin inhibitor (VTP50469), a DOT1L inhibitor (EPZ5676), and a CDK9 inhibitor (AZD4573). The single drug treatment durations with VTP50469, EPZ5676, and AZD4573 were 10 days, 14 days, and 3 days, respectively. The number of viable cells was determined by trypan blue exclusion staining. After the combination treatment, cells were washed with PBS, placed in fresh media for recovery and counted on day 4 or 6. The effectiveness of the combination treatments was determined using SynergyFinder 3.0 web application. Annexin V/PI and CD11b staining were performed using flow cytometry. To demonstrate MLL-menin binding inhibition, we generated an N-terminal FLAG-tagged MLL expression construct in leukemia cell lines and performed co-immunoprecipitation and western blot analysis. Results:We first determined theIC50 values for each inhibitor separately. Based on the IC50 values of VTP50469 (menin inhibitor), we categorized MLL-r cell lines into three groups: very sensitive (MOLM13 and MV4;11), moderately sensitive (RS4;11 and SEM) and resistant (THP1 and ML2) [Fig. A]. Sensitivity followed a similar pattern (MOLM13 and MV4;11 -sensitive, THP1-resistant) when MLL-r cell lines were treated with EPZ5676 (DOT1L Inhibitor). In contrast, AZD4573 demonstrated consistent efficacy across all MLL-r leukemia cell lines, with THP1 and MOLM13 being particularly sensitive with IC50 values in the low nanomolar (nM) range. After identifying the IC50 values of each inhibitor, we performed viability experiments using two and three drug combinations. The combination of VTP50469 (menin inhibitor) and EPZ5676 (DOT1L inhibitor) was superior in decreasing cell viability in MLL-r leukemia cell lines sensitive to VTP50469 (MV4;11, MOLM13 and RS4;11) but not effective in THP1 cells which are resistant to VTP50469 and EPZ5676 [Fig. B]. Synergy scores analyzed using the ZIP model showed additive effects in MOLM13 and a synergistic response in MV4;11 and RS4;11. After 14-17 days of treatment with EPZ5676 combined with VTP50469, MV4;11, MOLM13 and RS4;11 cells exhibited no recovery from treatment, indicating a profound and persistent antileukemia effect of the combination treatment. Conversely, the combination of VTP5069 (menin inhibitor) and AZD4573 (CDK9 inhibitor) showed a synergistic inhibitory effect on cell viability only in THP1 [Fig. B]. Compared to the single-drug treatments, we observed an increased rate of apoptosis and differentiation in THP1 cells treated with the combination of VTP50469 and AZD4573. The three-drug combination of EPZ5676, VTP50469, and AZD4573 was not superior to the two-drug combinations in any of the MLL-r cell lines examined. To characterize VTP50469 resistance, we analyzed the inhibition of MLL-menin binding using an MLL expression construct in VTP50469 sensitive and resistant cell lines treated with VTP50469 doses ranging between 5-500 nM. Following treatment with VTP50469, the level of expression of the MLL construct correlated with the sensitivity of MLL-r leukemia cell lines to the menin inhibitor. Conclusions: Based on our preclinical in vitro findings, the co-inhibition of menin-DOT1L or menin-CDK9 is a promising approach for the treatment of MLL-r leukemia. The varying responses of different MLL-r leukemia cell lines to drug combination treatment indicate that not all cases of MLL-r leukemia will respond uniformly to treatment combinations. Taken together, our data provide a strategy to determine optimal treatment combinations for personalized treatment of MLL-r leukemia.

Treatment of a TP53 isogenic AML Cell Line Model with Decitabine and All Trans-Retinoic Acid (ATRA) Targets MYC for Antileukemic Activity in a p53-Independent Fashion

Background The DECIDER randomized phase II trial showed that the addition of ATRA to decitabine (DAC) significantly improves survival and overall response rate (ORR) in newly diagnosed elderly AML patients (Lübbert et. al., J Clin Oncol. 2020), with a higher ORR in TP53-mutated (mostly heterozygous) compared to TP53 wildtype. Mechanisms of this in vivo synergism are under study, involving changes in global transcriptome and chromatin accessibility in both TP53wt and TP53mut AML cell lines (Meier et. al., Blood Cancer J. 2022). To further unravel the mechanism of action of DAC+ATRA (D+A) in AML, these studies are now extended to an isogenic TP53 model representing wt vs knock-out. Methods TP53 isogenic MOLM13 cells ( TP53+/+, TP53-/-, Boettcher et al., Science 2019) were treated with 100nM DAC by 3 daily pulses, 250nM ATRA on day 4, and studied for proliferation (EdU), by RNA-sequencing (RNA-seq) and immunofluorescence (IF) at 24, 48 and 72h post ATRA addition. RNA-seq data were analyzed after pre-processing (Cutadapt) and annotation (RNA star) by DEseq2 (adj p-value &amp;lt;0.05, fold change &amp;gt;2), functional enrichment analysis by pyGSEA on ‘50 Hallmark pathways’ using T-statistics on differentially expressed genes (DEGs). Results D+A reduced cell proliferation and increased apoptosis by 88% and 44% in TP53 +/+ cells, by 50% and 15% in TP53 -/- cells relative to control at 48h. By RNA-seq, the global transcriptomic profile of D+A was distinct from single-agent treatment at all 3 timepoints, as the majority of the DEGs were unique to the combination. D+A had 2250 unique DEGs (uDEGs) in TP53 +/+ cells (compared to 192 uDEGs for DAC, 249 uDEGs for ATRA); D+A had 1209 uDEGs in TP53 -/- cells (compared to 328 uDEGs with DAC and 197 uDEGs with ATRA) at 72h. By functional enrichment analysis, we found that D+A requires TP53 for antileukemic activity, as most proliferative pathways (e.g. hallmark G2M checkpoint, hallmark E2F targets) were depleted exclusively in a p53-dependent manner. Interestingly, D+A was able to induce an interferon response and deplete MYC target genes and mTOR signalling independent of p53. As MYC is a known target depleted by D+A, we investigated MYC (by IF) as an additional target for antileukemic activity. We found that global MYC levels were significantly depleted upon ATRA addition to DAC. ATRA depleted MYC levels independent of the TP53 status, while DAC depleted MYC in a p53-dependent manner (Fig. 1A). DAC was able to induce MYC T58 phosphorylation in both TP53 +/+ and TP53 -/- cells (Fig. 1B) but was only able to reduce MYC global levels in TP53+/+ cells, pointing towards a possible p53-dependent perturbation of proteasomal activity. FBXW7 (SCF complex), responsible for ubiquitinating pMYC T58, and USP28 (deubiquitinase) expression levels analysis revealed that USP28 is depleted upon DAC treatment, suggesting that FBXW7 should be able to mark pMYC T58 for ubiquitination and degradation, and further investigation is ongoing to determine proteasomal perturbation and how p53 loss is associated with it. Conclusions Our results represent a mechanistic exploration of how the addition of ATRA was able to enhance DAC's antileukemic activity in two polar opposite TP53 states (intact vs. null). D+A treatment induces a unique molecular signature compared to either drug and targets p53 for an antileukemic effect, but not exclusively, as MYC depletion as well as interferon induction is independent of p53. We also identified p53-dependent perturbation of proteasomal activity, as high amounts of pMYC T58 accumulate in TP53-/- cells upon D+A treatment, and hypothesize that pMYC T58 accumulation results in development of resistance to D+A. These studies will be extended to the most clinically relevant heterozygous TP53 hotspot mutations.

Oral Decitabine/Cedazuridine Vs Intravenous Decitabine for Acute Myeloid Leukemia: Final Results of a Randomized, Crossover, Registration-Enabling, Pharmacokinetics Study

Background: Parenterally administered hypomethylating agents (HMAs), decitabine (DEC) and azacitidine (AZA), are approved in Europe for adult patients with acute myeloid leukemia (AML) who are not candidates for standard induction chemotherapy as single agent or in combination with venetoclax. Cedazuridine(C) is a novel, potent, and safe inhibitor of cytidine deaminase (CDA) and when given in combination with decitabine, cedazuridine enables efficient oral availability of decitabine.ASTX727 (DEC-C) is a fixed-dose combination (FDC) tablet of 35 mg DEC and 100 mg cedazuridine, DEC-C has been approved for MDS in the US, Canada, and Australia. Here we present final results using DEC-C in an AML population appropriate for single-agent decitabine treatment. Aims: Describe the final clinical outcomes of patients with AML with additional analysis of genetic profiles. Methods: The ASCERTAIN study used a randomized two-period, two-sequence, two-treatment, crossover study design. Patients were randomized 1:1 to either Sequence A: DEC-C (35 mg DEC/100 mg cedazuridine) in Cycle 1 followed by IV-DEC at 20 mg/m 2 in Cycle 2, or Sequence B: receiving IV-DEC in Cycle 1 followed by DEC-C on Cycle 2 to compare pharmacokinetics (PK) [primary endpoint Area Under the Curve (AUC) equivalence over 5 days of dosing]. All patients received DEC-C from Cycle 3 until treatment discontinuation to assess safety and clinical efficacy. Patients were eligible as per the EMA-approved decitabine label (newly diagnosed AML who are not candidates for standard induction chemotherapy). Clinical responses were assessed according to modified International Working Group (IWG) 2003 response criteria. Pre-treatment peripheral blood was used for DNA isolation from leukocytes, and molecular abnormalities identified using a NGS hematologic malignancy panel. Cox-regression analysis on the various factors (eg binary mutational status, CR, etc.) was used for analyses of risk-factors for overall survival (OS). Results: 89 patients were randomized, of whom 87 were treated. The median age of patients was 78.0 years (range, 61 to 92) with 31 (35.6%) males and 56 (64.4%) females. Cytogenetic risk classification was poor-risk in 33 (37.9%), intermediate-risk in 45 (51.7%), and 9 (10.4%) not evaluated patients. For the primary endpoint, preliminary PK data was available from 69 patients who successfully completed PK assessments for both IV-DEC and DEC-C cycles, and the DEC AUC 0-24 (h*ng/mL) 5-Day geometric mean estimate was 904 for DEC-C and 907 for IV-DEC resulting in an oral/IV geometric LSM AUC ratio of 99.64% (90% CI of 91.23-108.8%). Safety findings were consistent with those anticipated for IV-DEC (related Grade ≥ 3 AEs in more than 10% were thrombocytopenia, neutropenia, anaemia, and febrile neutropenia). As of the database lock (25May2023), median follow up was 24.5 (20.2, 25.0) months (25% of 19.7 and 75% of 25.2 months). The best response was complete response (CR) in 19/87 (21.8%, 95% CI: 13.7, 32.0%); CR with incomplete blood cell count recovery (CRi) in 5 patients (5.7%); and CR with incomplete platelet recovery (CRp) in 2 (2.3%); resulting in composite response rate [CR + CRi] of 27.6%. The median overall survival was approximately 8.9 months (95% CI: 6.0, 13.1).These results obtained with DEC-C are consistent with those observed for IV-DEC. Multiple genes, including ASXL1, TP53, RUNX1, and SRSF2 genes were present in more than 20% of the AML patients. TP53 mutation was associated with worse survival. Summary/Conclusion: This randomized phase 3 study in AML patients not candidates for standard induction chemotherapy demonstrates that Daily X 5 dosing of the oral FDC of DEC-C resulted in an equivalent DEC AUC exposure to IV-DEC at 20 mg/m 2 over 5 days. Pharmacodynamic data showed similar demethylation rates (≤1.1% difference). In addition, safety findings and observed clinical activity (response rates and OS) are consistent with published data from IV-DEC, suggesting that DEC-C has the potential to be an oral alternative to the standard IV-DEC Daily×5 regimen. These findings support the use of DEC-C in patients with AML who are not candidates for standard induction chemotherapy.

Analysis of Safety and Efficacy of Avapritinib As Targeted Therapy for Pediatric Acute Myeloid Leukemia Patients with KIT Mutation after Transplantation

Objective: To investigate the safety and efficacy of Avapritinib in pediatric acute myeloid leukemia (AML) with KIT mutation after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Methods: The clinical data of 6 AML patients with KITmutation and RUNX1::RUNX1T1 fusion gene positive in Children's Hospital of Soochow University were retrospectively analyzed, including 2 cases of KIT:N822K, 3 cases of KIT: exon17 and 1 case of KIT: Asp816Tyr. After achieving complete remission in morphology, allo-HSCT was performed. The clinical outcomes of prophylactic therapy (2/6) and preemptive intervention (4/6) with Avapritinib after complete stem cell engraftment were observed, and the adverse events during treatment were recorded. Results: Adverse events occurred in 4 of the 6 patients, among whom neutropenia was the most common (4/6), followed by facial edema (2/6) and thrombocytopenia (1/6). 2 patients who received prophylactic treatment achieved morphological complete remission, and minimal residual disease (MRD), fusion gene and KIT mutations were all negative. 4 patients received preemptive intervention because of RUNX1::RUNX1T1 fusion gene turned positive after allo-HSCT, and 1 patient's RUNX1::RUNX1T1 turned negative after single-agent Avapritinib treatment for 2 months. 2 patients did not achieve continuous RUNX1::RUNX1T1 negative after preemptive therapy with Decitabine (DAC) and donor lymph infusion (DLI), and then was treated with Avapritinib, one's RUNX1::RUNX1T1 fusion achieved continuously negative after 1 month treatment of Avapritinib, the other's achieved continuous negative after 7 months treatment of Avapritinib. One patient was treated with Avapritinib after DAC and DLI as preemtive intervention, and RUNX1::RUNX1T1 fusion did not turn negative, but the relative value of RUNX1::RUNX1T1 fusion was lower than before and lived stable for more than 10 months. Conclusions: Avapritinib is safe and effective in the prophylactic and preemptive treatment of AML with KIT mutation after allo-HSCT in children, which provides a clinical drug for the prevention of relapse after transplantation.

Comparative Effectiveness of Ibrutinib Flexible Dosing Treatment Strategies on Time to Next Treatment in a Largely Community-Based Claims Database: A Target Trial Emulation Study

Introduction: Outside of a clinical trial setting, ibrutinib is the most well-characterized of the covalent Bruton's tyrosine kinase inhibitors used in the treatment of patients with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) in the first-line (1L) setting. However, the impact of ibrutinib dose adjustment on clinical outcomes remains to be defined. In this real-world effectiveness study, we compared time to next treatment (TTNT) as a proxy for disease progression for dose adjustment and standard dose treatment strategies in patients with CLL/SLL receiving 1L single-agent IBR. Methods: This study utilized the Komodo Health payer-complete dataset, derived from U.S. health insurance claims from &amp;gt;150 private insurers covering &amp;gt;160 million individuals from 2015-2023; 53% of these patients are from community centers. Adult patients with CLL/SLL were included if they initiated 1L single-agent IBR 420 mg/day between March 2016 - April 2023 (IBR initiation date = index date; 1L single-agent IBR was defined as no other CLL/SLL treatment in the 12-month baseline period or within 28 days after index). A target trial emulation (TTE) approach was utilized to compare TTNT, defined as the time between the index date to the initiation of a next line of therapy (LOT), for two treatment strategies: 1) Dose adjustment strategy, defined as a lead-in IBR treatment at 420mg/day for 3-12 months, followed by dose adjustment to &amp;lt;420mg/day until next LOT or IBR discontinuation; 2) Standard dose strategy, defined as a continuous IBR treatment at 420mg/day without any dose adjustment for &amp;gt;12 months until next LOT or IBR discontinuation. The TTE approach minimizes immortal time bias in a naïve observational analysis as patients in the dose adjustment cohort cannot initiate next LOT before dose adjustment occurs [Hernan et al. Am J Epidemiol. 2016]. To explicitly emulate a target trial, two clones were created for each patient, with one clone contributing person-time and event to each treatment strategy of interest, respectively. A clone was artificially censored when the actual treatment path deviated from the assigned treatment strategy. Selection bias due to artificial censoring was corrected using time-varying inverse probability of censoring weights (IPCW), accounting for post-index time-varying clinical factors related to IBR dose adjustment or IBR discontinuation. TTNT hazard ratio (HR; robust 95% confidence interval [CI]) was estimated using an IPCW-weighted pooled logistic regression model. Alternative lead-in periods with IBR standard dosing (3-6 and 3-9 months) were also evaluated. A subgroup analysis was conducted among patients with high cardiovascular (CV) risk, defined as having a preexisting CV comorbidity or a high CHA 2DS 2-Vasc risk score. Results: 3,342 adults initiated 1L single-agent IBR at 420 mg/day. Mean (standard deviation [SD]) age was 67.5 (10.6) years, 62% were male, and mean (SD) Quan-Charlson Comorbidity Index score was 3.0 (1.5). The median (interquartile range) follow-up duration was 19.6 (7.5, 35.0) months. During the study period, 463 patients (14%) initiated a subsequent LOT. The high CV risk subgroup consisted of 2,640 (79%) patients. In the overall study population, 608 (18%) patients experienced a dose adjustment after the index date. Of those, the dose adjustment occurred ≤3 months, ≤6 months, and ≤12 months post-index in 159 (26%), 300 (49%), and 440 (72%) patients, respectively, with dose used at the first reduction of 70 mg, 140 mg, or 280 mg in 4 (1%), 85 (14%), and 519 (85%) patients, respectively. The dose adjustment strategy (420 mg/day for 3-12 months followed by a reduced dose) was not associated with increased risk of initiating next LOT (adjusted HR [95% CI] 0.95 [0.80, 1.14]) compared to the continuous standard dose strategy; results for the alternative lead-in periods and the high CV risk subgroup were consistent with the primary scenario. Conclusions: In this real-world comparative effectiveness study with the majority of patients from community centers, dose adjustment of 1L single-agent IBR treatment for CLL/SLL is not associated with an increased risk of initiating next LOT when compared to continuous standard dose treatment. These findings suggest that a flexible dosing approach with IBR may be an effective option to maintain an optimal balance of clinical therapeutic efficacy and safety for patients with CLL/SLL in the 1L setting.