Small-molecule MDM2 Inhibitor Research Articles

10014-CBMS-2 CONCURRENT TARGETING OF MDM4 AND MDM2 USING CEP-1347 AS AN EFFECTIVE THERAPEUTIC STRATEGY FOR P53 WILD-TYPE MALIGNANT BRAIN TUMORS

Abstract The development of MDM4 inhibitors as an approach to reactivating p53 in human cancer is attracting increasing attention; however, whether they affect the function of MDM2 and how they interact with MDM2 inhibitors remain unknown. We addressed this question in the present study using CEP-1347, an inhibitor of MDM4 protein expression. The effects of CEP-1347, the genetic and/or pharmacological inhibition of MDM2, and their combination on the p53 pathway in malignant brain tumor cell lines expressing wild-type p53 were investigated by RT-PCR and Western blot analyses. The growth inhibitory effects of CEP-1347 alone or in combination with MDM2 inhibition were examined by dye exclusion and/or colony formation assays. The treatment of malignant brain tumor cell lines with CEP-1347 markedly increased MDM2 protein expression, while blocking CEP-1347-induced MDM2 overexpression by genetic knockdown augmented the effects of CEP-1347 on the p53 pathway and cell growth. Blocking the MDM2-p53 interaction using the small molecule MDM2 inhibitor RG7112, but not MDM2 knockdown, reduced MDM4 expression. Consequently, RG7112 effectively cooperated with CEP-1347 to reduce MDM4 expression, activate the p53 pathway, and inhibit cell growth. The present results suggest CEP-1347-induced MDM2 overexpression combined with the selective inhibition of MDM2's interaction with p53, while preserving its ability to inhibit MDM4 expression, as a novel and rational strategy to effectively reactivate p53 in wild-type p53 cancer cells.

Antagonizing MDM2 Overexpression Induced by MDM4 Inhibitor CEP-1347 Effectively Reactivates Wild-Type p53 in Malignant Brain Tumor Cells.

The development of MDM4 inhibitors as an approach to reactivating p53 in human cancer is attracting increasing attention; however, whether they affect the function of MDM2 and how they interact with MDM2 inhibitors remain unknown. We addressed this question in the present study using CEP-1347, an inhibitor of MDM4 protein expression. The effects of CEP-1347, the genetic and/or pharmacological inhibition of MDM2, and their combination on the p53 pathway in malignant brain tumor cell lines expressing wild-type p53 were investigated by RT-PCR and Western blot analyses. The growth inhibitory effects of CEP-1347 alone or in combination with MDM2 on inhibition were examined by dye exclusion and/or colony formation assays. The treatment of malignant brain tumor cell lines with CEP-1347 markedly increased MDM2 protein expression, while blocking CEP-1347-induced MDM2 overexpression by genetic knockdown augmented the effects of CEP-1347 on the p53 pathway and cell growth. Blocking the MDM2-p53 interaction using the small molecule MDM2 inhibitor RG7112, but not MDM2 knockdown, reduced MDM4 expression. Consequently, RG7112 effectively cooperated with CEP-1347 to reduce MDM4 expression, activate the p53 pathway, and inhibit cell growth. The present results suggest the combination of CEP-1347-induced MDM2 overexpression with the selective inhibition of MDM2's interaction with p53, while preserving its ability to inhibit MDM4 expression, as a novel and rational strategy to effectively reactivate p53 in wild-type p53 cancer cells.

A phase 2 study of alrizomadlin (APG-115) in combination with pembrolizumab in patients with unresectable or metastatic cutaneous melanoma that has failed immuno-oncologic (IO) drugs.

9559 Background: Alrizomadlin is a novel, orally active small-molecule MDM2 inhibitor that activates p53-mediated apoptosis in tumor cells, also functions as a host immunomodulator, and may restore antitumor activity in patients with cancer that has progressed on PD-1/PD-L1 inhibitors. Alrizomadlin is currently being investigated for treatment of patients with unresectable or metastatic cutaneous melanoma that progressed on prior immunotherapy. Methods: This multicenter clinical trial was conducted in the United States and Australia in patients with unresectable or metastatic cutaneous melanoma that had progressed on PD-1/PD-L1 immunotherapy. Eligible patients had an ECOG performance status of 0-2. Alrizomadlin 150 mg was administered orally every other day for 2 consecutive weeks, with 1 week off, and pembrolizumab 200 mg intravenously for 30 minutes on Day 1 of a 21-day cycle. Results: As of December 12, 2022, preliminary and interim results are reported for 31 patients with cutaneous melanoma, of whom 21 were male and 10 female, with a median (range) age of 65 (27-84) years. Treatment-related adverse events (TRAE) of any grade ( > 10%) for either alrizomadlin or pembrolizumab were reported in 30/31 (96.8%) patients. These AEs included nausea (71%), vomiting (38.7%), fatigue (35.5%), thrombocytopenia (32.3%), diarrhea (25.8%), neutropenia (19.4%), decreased appetite (16.1%), and decreased leukocyte count (12.9%). A total of 4/31 (12.9%) patients reported treatment-related serious AEs, including anemia, thrombocytopenia, deep vein thrombosis, joint effusion, pulmonary embolism, and vomiting. In 26 efficacy-evaluable patients, the confirmed overall response rate (ORR; partial response [PR] + complete response [CR]) was 23.1%, including 2 patients reporting CRs and 4 reporting PRs based on RECIST v.1.1. The initial analysis indicated that the ORR observed in patients whose disease had failed IO treatment was primarily due to alrizomadlin combined with pembrolizumab, not the delayed effect of prior immunotherapy. Conclusions: Alrizomadlin combined with pembrolizumab is well tolerated and demonstrates clinical efficacy in these patients with highly refractory unresectable or metastatic cutaneous melanoma that had progressed on PD-1/PD-L1 immunotherapy. Internal study identifier: APG-115-US002. Clinical trial information: NCT03611868 .

Combination Therapy With MDM2 and MEK Inhibitors Is Effective in Patient-Derived Models of Lung Adenocarcinoma With Concurrent Oncogenic Drivers and MDM2 Amplification

IntroductionAlthough targeted therapies have revolutionized the therapeutic landscape of lung adenocarcinomas (LUADs), disease progression on single-agent targeted therapy against known oncogenic drivers is common, and therapeutic options after disease progression are limited. In patients with MDM2 amplification (MDM2amp) and a concurrent oncogenic driver alteration, we hypothesized that targeting of the tumor-suppressor pathway (by means of restoration of p53 using MDM2 inhibition) and simultaneous targeting of co-occurring MAPK oncogenic pathway might represent a more durably effective therapeutic strategy. MethodsWe evaluated genomic next-generation sequencing data using the Memorial Sloan Kettering Cancer Center-Integrated Mutation Profiling of Actionable Cancer Targets platform to nominate potential targets for combination therapy in LUAD. We investigated the small molecule MDM2 inhibitor milademetan in cell lines and patient-derived xenografts of LUAD with a known driver alteration and MDM2amp. ResultsOf 10,587 patient samples from 7121 patients with LUAD profiled by next-generation sequencing, 6% (410 of 7121) harbored MDM2amp. MDM2amp was significantly enriched among tumors with driver alterations in METex14 (36%, p < 0.001), EGFR (8%, p < 0.001), RET (12%, p < 0.01), and ALK (10%, p < 0.01). The combination of milademetan and the MEK inhibitor trametinib was synergistic in growth inhibition of ECLC5-GLx (TRIM33-RET/MDM2amp), LUAD12c (METex14/KRASG12S/MDM2amp), SW1573 (KRASG12C, TP53 wild type), and A549 (KRASG12S) cells and in increasing expression of proapoptotic proteins PUMA and BIM. Treatment of ECLC5-GLx and LUAD12c with single-agent milademetan increased ERK phosphorylation, consistent with previous data on ERK activation with MDM2 inhibition. This ERK activation was effectively suppressed by concomitant administration of trametinib. In contrast, ERK phosphorylation induced by milademetan was not suppressed by concurrent RET inhibition using selpercatinib (in ECLC5-GLx) or MET inhibition using capmatinib (in LUAD12c). In vivo, combination milademetan and trametinib was more effective than either agent alone in ECLC5-GLx, LX-285 (EGFRex19del/MDM2amp), L13BS1 (METex14/MDM2amp), and A549 (KRASG12S, TP53 wild type). ConclusionsCombined MDM2/MEK inhibition was found to have efficacy across multiple patient-derived LUAD models harboring MDM2amp and concurrent oncogenic drivers. This combination, potentially applicable to LUADs with a wide variety of oncogenic driver mutations and kinase fusions activating the MAPK pathway, has evident clinical implications and will be investigated as part of a planned phase 1/2 clinical trial.

Abstract 6127: MDM2 inhibition in combination with MEK inhibition in pre-clinical models of lung adenocarcinomas with MDM2 amplification

Abstract The eventual development of resistance to single-agent targeted therapies in lung adenocarcinomas (LUAD) is inevitable, and new strategies are needed. We hypothesize that combination therapies aimed at a known driver and a distinct targetable alteration could prolong time on oral targeted therapy. In an analysis of 7636 patients with LUAD who underwent MSK-IMPACT large panel NGS testing, 5.5% (416/7636) harbored MDM2 amplification (MDM2amp), a known mechanism of TP53 inactivation. MDM2amp was over-represented among tumors with alterations in METex14 (34.4%, p&amp;lt;0.001), EGFR (10%, p&amp;lt;0.001), RET (11%, p&amp;lt;0.05), and ALK (9.9%, p&amp;lt;0.002). The small molecule MDM2 inhibitor milademetan (mila) caused growth inhibition as a single-agent in MDM2amp patient-derived cell lines with concurrent kinase alterations including ECLC5-GLx (MDM2amp/TRIM33::RET/TP53 wildtype (WT)) and LUAD12c (MDM2amp/METex14/KRASG12S/TP53 WT). Mila also caused growth inhibition in a cell line with KRASG12C and WT TP53 without MDM2amp (SW1573 (KRASG12C/TP53WT)), but not in cell lines with TP53 mutations (LUAD-002AS1 (KIF5B::RET/TP53P128fs, H1792 (KRASG12C/TP53 splice site mut)). Treatment of ECLC5-GLx and LUAD12c with mila resulted in restoration of ERK phosphorylation, confirming a previous report of ERK activation upon MDM2 inhibition. At 48 hours, ERK phosphorylation was suppressed by concurrent mila and MEK inhibition using trametinib (tram). In contrast, ERK phosphorylation was not suppressed by concurrent mila and KIF5B::RET inhibition using selpercatinib (in ECLC5-GLx) or MET inhibition using capmatinib (in LUAD12c). The combination of mila+tram was synergistic in slowing growth of ECLC5-GLx, LUAD12c, and SW1573 cells, and increased expression of pro-apoptotic proteins PUMA and BIM, beyond that achieved by either agent alone. In ECLC5-GLx, mila+tram also caused increased apoptotic cells measured by Annexin-V compared to either agent alone (combination p&amp;lt;0.01 compared to mila, p&amp;lt;0.001 compared to tram). In vivo, combination mila+tram was more effective than mila or tram alone in ECLC5-GLx (p&amp;lt;0.0001 and p&amp;lt;0.0001, respectively), LX-285 (EGFRex19del/MDM2amp) (p&amp;lt;0.0001 and p&amp;lt;0.0001, respectively), and L-13BS1 (model resistant to capmatinib) (METex14/MDM2amp) (p&amp;lt;0.05 and p&amp;lt;0.0001, respectively). These results suggest that combined MDM2/MEK inhibition is effective in patient-derived LUAD models harboring MDM2amp. This combination, potentially applicable to LUADs with a wide variety of oncogenic driver mutations and kinase fusions will be investigated as part of a phase 1/2 clinical trial. Citation Format: Arielle Elkrief, Vladimir Markov, Álvaro Quintanal-Villalonga, Rebecca Caeser, Pawel Sobczuk, Emily Cheng, Alexander Drilon, Gregory J. Riely, William W. Lockwood, Elisa de Stanchina, Charles M. Rudin, Igor Odintsov, Romel Somwar. MDM2 inhibition in combination with MEK inhibition in pre-clinical models of lung adenocarcinomas with MDM2 amplification [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6127.

MDM2 inhibitors, nutlin-3a and navtemadelin, retain efficacy in human and mouse cancer cells cultured in hypoxia

Activation of p53 by small molecule MDM2 inhibitors can induce cell cycle arrest or death in p53 wildtype cancer cells. However, cancer cells exposed to hypoxia can develop resistance to other small molecules, such as chemotherapies, that activate p53. Here, we evaluated whether hypoxia could render cancer cells insensitive to two MDM2 inhibitors with different potencies, nutlin-3a and navtemadlin. Inhibitor efficacy and potency were evaluated under short-term hypoxic conditions in human and mouse cancer cells expressing different p53 genotypes (wild-type, mutant, or null). Treatment of wild-type p53 cancer cells with MDM2 inhibitors reduced cell growth by > 75% in hypoxia through activation of the p53–p21 signaling pathway; no inhibitor-induced growth reduction was observed in hypoxic mutant or null p53 cells except at very high concentrations. The concentration of inhibitors needed to induce the maximal p53 response was not significantly different in hypoxia compared to normoxia. However, inhibitor efficacy varied by species and by cell line, with stronger effects at lower concentrations observed in human cell lines than in mouse cell lines grown as 2D and 3D cultures. Together, these results indicate that MDM2 inhibitors retain efficacy in hypoxia, suggesting they could be useful for targeting acutely hypoxic cancer cells.

Characterize Biomarkers and Mechanisms of Resistance for MDM2 Inhibitors in AML

Acute myeloid leukemia (AML) is a molecularly and clinically heterogeneous disease with an aggressive phenotype and poor prognosis. Inactivation of the wild-type p53, through upregulation of the TP53 negative regulator MDM2, is observed in around 50% of AML patients, providing a rationale for targeting MDM2 for the treatment of AML. Small molecule inhibitors of MDM2, including Idasanutlin, have shown efficacy as monotherapy and in combinations. However, patients exhibit heterogeneous responses with frequent drug resistance. We integrated ex vivo drug sensitivity assay, clinical parameters, whole exome sequence (WES), RNAseq, cytokine stimulation, and CRISPR/Cas9 dropout screening data to identify biomarkers that predict idasanutlin response and to elucidate the underlying drug-resistant mechanisms. Surprisingly, besides TP53 itself, we did not find an essential role in losing any of the major TP53 downstream targets alone leading to Idasanutlin resistance from Idasanutlin treated resistant cell lines, CRISPR screening, or individually targeted knockout experiments. Besides TP53 mutations, other major AML mutations, including RAS pathway mutations do not drive Idasanutlin resistance indicated by the patient sample functional screening data and in vitro mutation overexpression models. We observed instead that AML with a high differentiation or mature myeloid signature: including low blast, a high percentage of monocytes/granulocytes/T cells, AML FAB M4/M5 morphology, and a high expression of a myeloid immune signature gene are relatively resistant to Idasanutlin. We further characterized that both healthy/leukemia-associated T cells, granulocytes, and monocytes are intrinsically resistant to idasnutlin due to low expression levels of MDM2 and/or TP53. To examine whether the presence of differentiated cells protects leukemia blast cells from Idasanutlin, we performed a co-culture drug treatment experiment. Strikingly, only leukemia-associated monocytes, but not healthy monocytes, healthy/leukemia T cells or granulocytes, or leukemia blast cells protected leukemia blast cells from apoptosis in the presence or absence of Idasanutlin. Similar results were obtained for the other two MDM2 inhibitors, AMG232 and DS-3032b, and a BCL2 inhibitor, venetoclax. To further uncover which cytokines secreted from the leukemia-associated monocytes confer MDM2 inhibitor resistance, we tested 11 common cytokines, including IL-1a, IL-1b, IL-3, IL-6, IL-8, M-CSF GM-CSF, FLT3, MCP-1, TNFa, and SCF. We observed that IL-1α, IL-1β, IL-3, and GM-CSF markedly induced idasanutlin treatment resistance for AML, but not ALL or CLL patient cells. Interestingly, IL-1α and IL-1β only protect leukemia blasts, but not healthy CD34 hematopoietic stem and progenitor cells from Idasanutlin-induced apoptosis. We further performed RNAseq and immunoblots on IL-1α and IL-1β treated AML, CLL, and ALL cells. We observed the major TP53 downstream pathways remain activated by idasanutlin in the presence of IL-1α and IL-1β. Interestingly, GATA2 is significantly upregulated in IL-1α and IL-1β treated AML, but not CLL or ALL cells in the presence or absence of Idasanutlin. Furthermore, overexpressing GATA2 conferred Idasanutlin resistance at high concentrations. Finally, we observed that combining a FLT3/IRAK dual inhibitor, pacritinib, or an IRAK1 /IL-1 receptor antagonist, anakinra, partially rescued IL-1α and IL-1β mediated drug resistance of MDM2 inhibitors. As such, we uncovered the role of leukemia-associated monocyte in driving intrinsic and extrinsic MDM2 inhibitor resistance and the potential underlying mechanisms.

CTNI-26. SURGICAL WINDOW OF OPPORTUNITY TRIAL OF NAVTEMADLIN (KRT 232; AMG232) IN PATIENTS WITH RECURRENT GLIOBLASTOMA

Abstract BACKGROUND KRT232 is an orally bioavailable, selective small molecule inhibitor of MDM2 that blocks the protein-protein interaction between MDM2 and p53. We performed a surgical window of opportunity trial of KRT232 in patients with recurrent GBM. METHODS The primary endpoint was to determine the tumor tissue concentration of KRT232. Prior to surgery, patients received KRT232 at either 120mg (n = 10, minimal dose that is consistently associated with alterations in serum MIC-1) or 240mg (n = 10; recommended phase 2 dose as monotherapy) for two days prior to surgical resection. Surgery was performed 3-6 hours following the last administration of KRT232. Tissue was analyzed for KRT232 concentration by LC/MS and for correlative studies. Participants with TP53 wild-type tumors were eligible to continue KRT232 following recovery from surgery at the RP2D of 240mg QD x 7 days q3weeks. RESULTS Twenty-one patients were enrolled from July 2018 to April 2020. One patient was deemed ineligible after surgery due to non-GBM tumor. Study met the prespecified criteria of target intra-tumor drug concentration of ≥ 25nM in contrast enhancing tissue in more than 50% of the patients in the 120mg cohort (67.1 ± 42.7nM in 8/10 patients) and 240mg (328.7 ± 468.1nM in 10/10 patients) cohort. Serum MIC-1 fold-changes from baseline (FCB) approximately 24 hours after a single dose of KRT232 were higher in the 240mg cohort (9.1 ± 4.1-FCB) than the 120mg cohort (3.6 ± 2.0-FCB). CDKN1A (p21), a downstream marker of p53, was significantly upregulated in analyzed participants whose GBM was TP53 wildtype, but not in TP53 mutant GBM or control samples (GBM treated with standard of care). CONCLUSION KRT232 at both 120mg and 240mg achieves adequate tumor tissue penetration and affects downstream pathways in TP53 wildtype GBM. The study has moved to Alliance to complete a phase 1 study of radiation + KRT232 in patients with newly diagnosed MGMT unmethylated GBM.

The inhibition of MDM2 slows cell proliferation and activates apoptosis in ADPKD cell lines.

Autosomal dominant polycystic kidney disease (ADPKD) is characterised by progressive cysts formation and renal enlargement that in most of cases leads to end stage of renal disease (ESRD). This pathology is caused by mutations of either PKD1 or PKD2 genes that encode for polycystin-1 (PC1) and polycystin-2 (PC2), respectively. These proteins function as receptor-channel complex able to regulate calcium homeostasis. PKD1/2 loss of function impairs different signalling pathways including cAMP and mTOR that are considered therapeutic targets for this disease. In fact, Tolvaptan, a vasopressin-2 antagonist that reduces cAMP levels, is the only drug approved for ADPKD treatment. Nevertheless, some ADPKD patients developed side effects in response to Tolvaptan including liver damage. Conversely, mTOR inhibitors that induced disease regression in ADPKD animal models failed the clinical trials. Here, we show that the inhibition of mTOR causes the activation of autophagy in ADPKD cells that could reduce therapy effectiveness by drug degradation through the autophagic vesicles. Consistently, the combined treatment with rapamycin and chloroquine, an autophagy inhibitor, potentiates the decrease of cell proliferation induced by rapamycin. To overcome the dangerous activation of autophagy by mTOR inhibition, we targeted MDM2 (a downstream effector of mTOR signalling) that is involved in TP53 degradation by using RG7112, a small-molecule MDM2 inhibitor used for the treatment of haematologic malignancies. The inhibition of MDM2 by RG7112 prevents TP53 degradation and increases p21 expression leading to the decrease of cell proliferation and the activation of apoptosis. The targeting of MDM2 by RG7112 might represent a new therapeutic option for the treatment of ADPKD.

Application of In Silico Filtering and Isothermal Titration Calorimetry for the Discovery of Small Molecule Inhibitors of MDM2.

The initial discovery phase of protein modulators, which consists of filtering molecular libraries and in vitro direct binding validation, is central in drug discovery. Thus, virtual screening of large molecular libraries, together with the evaluation of binding affinity by isothermal calorimetry, generates an efficient experimental setup. Herein, we applied virtual screening for discovering small molecule inhibitors of MDM2, a major negative regulator of the tumor suppressor p53, and thus a promising therapeutic target. A library of 20 million small molecules was screened against an averaged model derived from multiple structural conformations of MDM2 based on published structures. Selected molecules originating from the computational filtering were tested in vitro for their direct binding to MDM2 via isothermal titration calorimetry. Three new molecules, representing distinct chemical scaffolds, showed binding to MDM2. These were further evaluated by exploring structure-similar chemical analogues. Two scaffolds were further evaluated by de novo synthesis of molecules derived from the initial molecules that bound MDM2, one with a central oxoazetidine acetamide and one with benzene sulfonamide. Several molecules derived from these scaffolds increased wild-type p53 activity in MCF7 cancer cells. These set a basis for further chemical optimization and the development of new chemical entities as anticancer drugs.

Abstract 4001: Evaluation of novel therapeutics using the Mayo Clinic GBM Patient-Derived Xenograft (PDX) collection

Abstract The Mayo Clinic collection of patient-derived xenograft (PDXs) has been developed from the direct implantation of glioblastoma (GBM) samples into immunodeficient mice. Over 105 models have been extensively characterized with regards to histology, invasion, flank and orthotopic growth rates, and molecular profiling. Evaluation of orthotopic tumors demonstrated infiltration of tumor cells into the brain parenchymal in 90% of models with contralateral hemisphere involvement in 64%. Extensive molecular profiling confirmed the PDX collection captures the genetic heterogeneity of GBM, with the majority of typical molecular alterations seen at a frequency similar to the TCGA including gain of chromosome 7 and loss of chromosome 10. TERT promoter mutations (86%) and homozygous deletion of CDKN2A (70%) were the most frequent. Additional alterations in the p53 pathway included TP53 mutations (36%) and MDM2/4 amplification (10%/2%). IDH mutations were found in three models while MGMT promoter methylation was observed in 45% of PDXs. The available molecular sequencing results are viewable on cBioPortal. These genetically diverse models are extremely useful for biomarker discovery and efficacy evaluations. Using an innovative 1x1x1 PDX preclinical trial design, we are establishing a workflow to evaluate control and drug treatment in an individual animal across PDX lines in the flank. As our first use of this strategy, a small molecule MDM2 inhibitor was evaluated in 17 PDX lines with variable MDM2 and TP53 statuses. Tumors harboring MDM2 amplification without TP53 mutation (n=5) showed profound response, with 4 PDXs showing a complete response that lasted &amp;gt;150 days. Response in TP53 wild-type tumors lacking MDM2 amplification was variable, with a 1.9 to 4.8 fold longer time to endpoint (mean 3; median 2.7). A more traditionally powered intracranial efficacy study performed with one MDM2 amplified (GBM108) and two non-amplified (GBM14, GBM10) PDX lines confirmed these findings of reduced and more variable response to therapy in MDM2 non-amplified TP53 wild-type tumors. Future studies will aim to examine novel biomarkers indicative of therapeutic response to better understand molecular features associated with MDM2 inhibitor efficacy. With over 20 years of experience, our group has extensive expertise in development of clinically relevant study designs focused on examining efficacy, tolerability, and pharmacokinetic/pharmacodynamic assessments. Our diverse collection of clinically relevant GBM PDX models provides a highly sought-after resource which has been utilized by the pharmaceutical community with 58 working relationships to date (26 contracts, 32 collaborations). Through these collaborations, we aim to expand the use of our highly characterized GBM PDX panel for biomarker discovery using similar strategies. Citation Format: Danielle M. Burgenske, Ann C. Mladek, Shulan Tian, Mark A. Schroeder, Zeng Hu, Brett L. Carlson, Paul A. Decker, Jeanette E. Eckel-Passow, Rachael Vaubel, Jann N. Sarkaria. Evaluation of novel therapeutics using the Mayo Clinic GBM Patient-Derived Xenograft (PDX) collection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4001.

Using CDKN2A loss in the context of wildtype TP53 to predict sensitivity for the MDM2 inhibitor milademetan.

3136 Background: MDM2 is an E3 ubiquitin ligase that plays a critical role in the degradation of the tumor suppressor p53. Milademetan (RAIN-32) is an orally available, small molecule inhibitor of MDM2 that disrupts the MDM2-p53 complex thereby restoring p53 activity. Approximately 50% of tumors harbor wildtype (WT) TP53 and thus may be susceptible to strategies that reactivate p53. The CDKN2A gene is altered in more than 15% of all tumors (TCGA PanCancer Atlas) and encodes two proteins, p14ARF and p16, which are inhibitors of p53 and cyclin dependent kinases, respectively. Given the role of p14ARF in regulating the MDM2-p53 pathway, we investigated the use of CDKN2A loss in the context of WT TP53 as a strategy for selection of patients who might benefit from milademetan. Methods: N/A. Results: We evaluated the sensitivity of 215 cancer cell lines to milademetan treatment (Ishizawa et al., 2018) by CDKN2A and TP53 status. The median IC50 of CDKN2A homozygous (HZ) loss vs. non-HZ loss was 8,620 vs. 10,000 nM. However, when we assessed CDKN2A HZ loss with WT TP53 versus mutant TP53 the median IC50 was 79.5 vs. 10,000 nM demonstrating that the use of both CDKN2A and TP53 was better able to discriminate sensitive vs. resistant cell lines. To validate these in vitro findings, we tested milademetan in 5 xenograft models with CDKN2A HZ loss and WT TP53, all of which demonstrated tumor growth inhibition with milademetan. As suppression of p53 activity by MDM2 amplification (Kato et al. 2017) or CDKN2A loss (Adib et al. 2021) has been associated with resistance to immune checkpoint inhibitors (ICI), we also tested the combination of anti-PD1 with milademetan in the colon-26 syngeneic model ( CDKN2A HZ loss) and observed a significant enhancement in tumor growth inhibition compared to milademetan or anti-PD1 alone. Based on the differential sensitivity to milademetan using both CDKN2A loss and WT TP53 status we evaluated TCGA Pan-Cancer Atlas data to estimate the frequency of these genetic co-alterations. Among solid tumors types the most frequent percentage of these co-alterations included glioblastoma, mesothelioma, melanoma, bladder, sarcoma, pancreatic and NSCLC. Overall, the percentage of all tumors with co-alteration of CDKN2A HZ loss and WT TP53 was 6.2%. Patients with CDKN2A HZ loss had a significantly worse overall survival than those without CDKN2A HZ loss (median OS of 29.7 vs. 97.4 months, p &lt; 0.0001), and this was maintained when accounting for tumor type in multivariate analysis (p &lt; 0.0001). Conclusions: Milademetan showed evidence of preclinical anti-tumor activity across multiple tumor types with CDKN2A loss and WT TP53. In vivo data supported potential synergy of milademetan with an ICI in this genetic subset. A clinical trial evaluating the safety and efficacy of milademetan plus atezolizumab in advanced solid tumors with CDKN2A HZ loss and WT TP53 (MANTRA-4) is planned.

Abstract P210: MDM2 gene amplification as a predictive biomarker for the MDM2 inhibitor milademetan

Abstract MDM2 is an E3 ubiquitin ligase that plays a critical role in the degradation of the tumor suppressor p53. Milademetan (RAIN-32) is an orally available, small molecule inhibitor of MDM2 that disrupts the MDM2-p53 protein complex thereby restoring p53 expression and activity. Milademetan has demonstrated anti-tumor activity in de-differentiated liposarcoma, a tumor type characterized by MDM2 gene amplification (amp) and WT TP53, in the phase I study of monotherapy milademetan (NCT01877382). Here we investigate the use of MDM2 gene amplification as a predictive biomarker for the selection of patients with advanced cancers who might benefit from milademetan. In this study we evaluated milademetan in MDM2 gene amp cancer models from a variety of tumor types using both in vitro assays, including 2D viability assays and organoid models, as well as in vivo patient-derived xenografts. We employed a mutual exclusivity analysis between MDM2 copy number (CN) and TP53 mutation status using publicly available next generation sequencing data to derive an optimal MDM2 CN threshold for patient selection and present clinical data from patients with MDM2 amp tumors treated with milademetan in the phase 1 study (NCT01877382). Three cell lines, CCFSTTG1 (astrocytoma), DKMG (glioblastoma), and SJSA1 (osteosarcoma), with MDM2 amp were identified and demonstrated inhibition of cell proliferation by milademetan with GI50 &amp;lt;100 nM. Evidence of MDM2 target engagement and activation of p53 was demonstrated through induction of p21 and PUMA, transcriptional targets of p53. Four patient-derived organoid models from diverse cancers (2 lung adenocarcinoma, 1 cholangiocarcinoma, and 1 renall cell carcinoma) were identified with MDM2 amp and WT TP53 and demonstrated differential selectivity compared to non-MDM2 amp models also with WT TP53 (head and neck scquamous cell carcinoma, endometrial carcinoma). Xenograft models from tumor types including gastric, lung adenocarcinoma and osteosarcoma with MDM2 amp showed dose-dependent anti-tumor activity to milademetan in vivo. Induction of MIC-1, a p53 target gene, was observed in vivo following milademetan dosing. An MDM2 CN threshold of ≥ 12 was derived using mutual exclusivity analysis using the AACR Genie dataset across solid tumor types. Using TCGA Pan-Cancer Atlas dataset, we identified 1.1% of cancers that met the criteria of MDM2 CN ≥ 12 and WT TP53. Finally, 3 patients (breast cancer, synovial sarcoma, and small cell lung cancer) with MDM2 CN ≥ 12 were previously enrolled on the U101 study of milademetan, Schedule D (3 days on 11 days off), which was determined to be the dose schedule for future clinical trials, and all 3 patients experienced tumor reduction with 2 patients demonstrating a partial response and 1 confirmed partial response. Milademetan shows evidence of preclinical and clinical anti-tumor activity in genetically selected tumors using MDM2 amp and WT TP53 as selection criteria. A basket study evaluating milademetan in solid tumors with MDM2 CN ≥ 12 and WT TP53 (MANTRA-2) is planned. Citation Format: Vijaya G. Tirunagaru, Mrinal M. Gounder, Prasanna R. Kumar, David S. Hong, Robert C. Doebele. MDM2 gene amplification as a predictive biomarker for the MDM2 inhibitor milademetan [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P210.

Abstract P215: The MDM2 inhibitor milademetan induces synthetic lethality in GATA3 mutant, ER positive breast cancer

Abstract GATA3 is mutated, predominantly via frameshift (fs) mutations, in 15-18% of estrogen receptor (ER)-positive breast cancers and GATA3 mutations define a subset of patients with poor response to hormonal therapy. Importantly, GATA3 mutations are not currently targetable. Computational analysis of the data from the large-scale, deep RNAi screen project DRIVE led to the identification of MDM2 as a synthetic lethal partner in a GATA3 mutant ER+ breast cancer cell line. The objective of this study was to evaluate the activity of milademetan (RAIN-32), an orally available, small molecule inhibitor of MDM2 in GATA3 mutant ER+ breast cancer. Here, we evaluated the effect of MDM2 silencing in ER+, GATA3 mutant breast cancer cell line MCF-7 harboring a loss-of-function mutation (p.D335Gfs) that has been recurrently observed in breast cancer patients and tested the antitumoral activity of milademetan in vitro (MCF-7 cell line) ex vivo (patient derived organoids; PDO) and in vivo (cell line-derived xenograft and patient-derived xenograft (PDX) models). Additionally, we hypothesized that the synthetic lethality is p53 dependent and to this aim we explored the p53 dependent effects of milademetan inhibition by determining the effect of MDM2 loss in the absence of p53 and analyzing the expression of p53-target genes. Finally, we evaluated the impact of GATA3 mutations on survival in breast cancer using TCGA and AACR Genie datasets.MDM2 silencing significantly reduced cell proliferation in MCF-7. This effect was shown to be p53 dependent as p53 knockdown reversed the effect of MDM2 loss. MCF-7 cell line was also sensitive to milademetan in vitro. Finally, we tested milademetan in ER+ breast cancer models (PDO and a fulvestrant-resistant PDX) harboring a GATA3fs mutation and wild type TP53. Treatment of these models displayed dose-dependent anti-tumor activity to milademetan ex vivo and in vivo. Sequencing data analyses of the publicly available datasets revealed lower survival in GATA3 mutant breast cancer and mutual exclusivity with TP53 mutations. In conclusion, MDM2 deficiency leads to synthetic lethality in GATA3 mutant breast cancers. Milademetan shows evidence of antitumor activity in genetically selected ER+ breast tumors with GATA3 mutations. These data provide evidence for clinical exploration of milademetan in ER+, GATA3 mutant breast cancer refractory to current therapies. Citation Format: Vijaya G. Tirunagaru, Gaia Bianco, Charlotte K. Y. Ng, Elisabetta Marangoni, Salvatore Piscuoglio, François-Clément Bidard, Robert C. Doebele. The MDM2 inhibitor milademetan induces synthetic lethality in GATA3 mutant, ER positive breast cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P215.

The Discovery of Potential MDM2 Inhibitors: A Combination of Pharmacophore Modeling, Virtual Screening, Molecular Docking Studies, and in vitro/in vivo Biological Evaluation

Small-molecule inhibitors of MDM2 that block the MDM2-p53 protein-protein interaction have been considered as potential therapeutic agents for the treatment of cancer. Here, we identify five highly potent inhibitors of MDM2 (termed as WY 1-5) that display significant inhibitory effects on MDM2-p53 interaction by using a combined strategy of pharmacophore modeling, virtual screening, and molecular docking studies. Among them, WY-5 is the most active MDM2 inhibitor with an IC50 value of 14.1±2.8 nM. Moreover, WY-5 significantly up-regulate the protein level of p53 in SK-Hep-1 cells harboring wild-type p53. In vitro anticancer study reveals that WY-5 markedly inhibits the survival of SK-Hep-1 cells. In vivo anticancer study suggests that WY-5 significantly inhibits the growth of SK-Hep-1 cells-derived xenograft in nude mice, with no observable toxicity. Our results demonstrate that WY-5 may be a promising candidate for the treatment of cancer harboring wild-type p53.

EXTH-20. SINGLE-CELL DRUG ACTIVITY MAPPING IN GLIOBLASTOMA IDENTIFIES EXTENDED DRUG RESPONSE HETEROGENEITY AND THERAPY-INDUCED CELLULAR PLASTICITY

Abstract Glioblastoma (GBM) remains a highly malignant and incurable brain tumour. The inability to achieve clinical improvements in GBM treatment can be attributed to the excessive heterogeneity and plasticity of GBM cells, which is reflected by the presence of various cellular states within each tumour. How each of these tumour cell subtypes respond to therapy remains largely unknown. In this work, we developed a functional diagnostic analysis pipeline to measure therapeutic activity in GBM tumour cells at single-cell resolution using mass cytometry by time-of-flight (CyTOF). By applying an optimised GBM-specific and therapy-tailored antibody panel, we measured therapeutic activity upon exposure to ionising radiation (RT) or a small molecule MDM2 inhibitor (AMG232) in a cohort of patient-derived GBM cell lines (n=14). As such, extended heterogeneity in drug responsiveness was reflected by diverse degrees of alterations in cell cycle progression and apoptotic signalling, in addition to shifts in tumoral phenotypic states implying therapy-induced plasticity. A similar approach was used to measure drug activity in freshly resected tumour samples (n=18) harvested from different tumour regions (core or invasive front) within hours following surgery. Accordingly, we identified highly variable fractions of responsive tumour and microenvironmental cell populations in a patient-specific way. The ability to measure drug activity at single-cell resolution in a patient-tailored manner by applying a genotype-agnostic method, paves the way for advanced precision cancer medicine in GBM by offering a novel approach to more precisely select eligible patients for prospective clinical trials.

MDM2/X Inhibitors as Radiosensitizers for Glioblastoma Targeted Therapy.

Inhibition of the MDM2/X-p53 interaction is recognized as a potential anti-cancer strategy, including the treatment of glioblastoma (GB). In response to cellular stressors, such as DNA damage, the tumor suppression protein p53 is activated and responds by mediating cellular damage through DNA repair, cell cycle arrest and apoptosis. Hence, p53 activation plays a central role in cell survival and the effectiveness of cancer therapies. Alterations and reduced activity of p53 occur in 25-30% of primary GB tumors, but this number increases drastically to 60-70% in secondary GB. As a result, reactivating p53 is suggested as a treatment strategy, either by using targeted molecules to convert the mutant p53 back to its wild type form or by using MDM2 and MDMX (also known as MDM4) inhibitors. MDM2 down regulates p53 activity via ubiquitin-dependent degradation and is amplified or overexpressed in 14% of GB cases. Thus, suppression of MDM2 offers an opportunity for urgently needed new therapeutic interventions for GB. Numerous small molecule MDM2 inhibitors are currently undergoing clinical evaluation, either as monotherapy or in combination with chemotherapy and/or other targeted agents. In addition, considering the major role of both p53 and MDM2 in the downstream signaling response to radiation-induced DNA damage, the combination of MDM2 inhibitors with radiation may offer a valuable therapeutic radiosensitizing approach for GB therapy. This review covers the role of MDM2/X in cancer and more specifically in GB, followed by the rationale for the potential radiosensitizing effect of MDM2 inhibition. Finally, the current status of MDM2/X inhibition and p53 activation for the treatment of GB is given.

Preliminary results of a phase II study of alrizomadlin (APG-115), a novel, small-molecule MDM2 inhibitor, in combination with pembrolizumab in patients (pts) with unresectable or metastatic melanoma or advanced solid tumors that have failed immuno-oncologic (I-O) drugs.

2506 Background: Alrizomadlin (APG-115) restores TP53 function, activating p53-mediated apoptosis in tumor cells with wild-type TP53 and/or MDM2 amplification. Alrizomadlin also functions as a host immunomodulator and hence may restore antitumor activity in pts with cancers failing PD-1/PD-L1 blockade. Methods: This US multicenter trial assessed alrizomadlin combined with pembrolizumab in pts with unresectable/metastatic melanoma or advanced solid tumors that had failed I-O drugs; or pts with malignant peripheral nerve sheath tumor (MPNST), liposarcoma, or ATM mutant solid tumors that had failed any standard therapy. Eligible pts had ECOG performance status of 0-2 and no CNS metastases. The phase II study cohorts included pts with melanoma, NSCLC, solid tumor with ATM mutation, well-differentiated/dedifferentiated liposarcoma, urothelial carcinoma, and MPNST. Alrizomadlin was administered orally at 150 mg once every other day for 2 consecutive weeks with 1 week off and pembrolizumab at 200 mg via IV infusion for 30 minutes on Day 1 of a 21-day cycle. Results: As of December 25, 2020, 84 pts had been treated in 6 cohorts: melanoma (n = 26), NSCLC (n = 23), ATM mutation (n = 9), liposarcoma (n = 14), urothelial (n = 9), and MPNST (n = 3). In the PD-1/PD-L1 inhibitor-failed melanoma cohort, there was 1 confirmed partial response (PR) out of 5 pts with uveal melanoma, 2 PR (1 confirmed and 1 unconfirmed) of 5 pts with mucosal melanoma, and 1 confirmed PR of 11 pts with cutaneous melanoma. ORR in the melanoma cohort was 17.4% (4/23 evaluable pts), and the disease control rate was 60.9% (14/23). In the MPNST cohort, 1 of 3 pts had an unconfirmed ongoing PR. In I-O drug-failed NSCLC (n = 14 evaluable) and urothelial (n = 5 evaluable) cohorts, each reported 1 confirmed PR. Common treatment (alrizomadlin or pembrolizumab)-related adverse events (TRAEs) (≥ 10%) were nausea (63.1%), thrombocytopenia (36.9%), vomiting (33.3%), fatigue (31.0%), decreased appetite (27.4%), diarrhea (21.4%), neutropenia (15.4%), and anemia (11.9%). Grade ≥ 3 TRAEs (≥ 5%) included thrombocytopenia (20.2%), neutropenia (14.2%), and anemia (8.3%). Eleven pts discontinued treatment due to AEs: 5 were treatment related, including 2 grade 4 thrombocytopenia, and 1 each of grade 2 vomiting, grade 2 fatigue, and grade 2 posterior reversible encephalopathy syndrome (PRES). Three treatment-related SAEs were PRES, pyrexia, and asthenia. Conclusions: Alrizomadlin combined with pembrolizumab is well tolerated and may restore antitumor effects in pts with cancer resistant to or intolerant of I-O drugs, as suggested by preliminary antitumor activities in multiple tumor types. Internal study identifiers: APG-115-US-002; Keynote MK-3475-B66. Clinical trial information: NCT03611868.

TMOD-15. EFFICACY OF THE MDM2 INHIBITOR KRT-232 IN GLIOBLASTOMA PATIENT-DERIVED XENOGRAFT MODELS

Abstract Non-genotoxic reactivation of p53 by MDM2 inhibitors represents a promising therapeutic strategy for tumors with wild-type TP53, particularly tumors harboring MDM2 amplification. MDM2 controls p53 levels by targeting it for degradation, while disruption of the MDM2-p53 interaction causes rapid accumulation of p53 and activation of the p53 pathway. We examined the efficacy of the small molecule MDM2 inhibitor KRT-232, alone and in combination with radiation therapy (RT), in MDM2-amplified and/or p53 wildtype patient-derived xenograft (PDX) models of glioblastoma in vitro and in vivo. In vitro, glioblastoma PDX explant cultures showed sensitivity to KRT-232, both tumors with MDM2 amplification (GBM108 and G148) and non-amplified but TP53-wildtype lines (GBM10, GBM14, and GBM39), with IC50s ranging from 300-800 nM in FBS culture conditions. A TP53 p.F270C mutant PDX (GBM43) was inherently resistant, with IC50 &amp;gt;3000 nM. In the MDM2-amplified GBM108 line, KRT-232 led to a robust (5-6 fold) induction of p53-target genes p21, PUMA, and NOXA, with initiation of both apoptosis and senescence. Expression of p21 and PUMA was greater with KRT-232 in combination with RT (25-35 fold induction), while stable knock-down of p53 in GBM108 led to complete resistance to KRT-232. In contrast, GBM10 showed lower induction of p21 and PUMA (2-3 fold) and was more resistant to KRT-232. In an orthotopic GBM108 xenograft model, treatment with KRT-232 +/- RT for one week extended survival from 22 days (placebo) to 46 days (KRT-232 alone); combination KRT-232 + RT further extended survival (77 days) over RT alone (31 days). KRT-232 is an effective treatment in a subset of glioblastoma pre-clinical models alone and in combination with RT. Further studies are underway to understand the mechanisms conferring innate sensitivity or resistance to KRT-232.

Effect of Food on MDM2 Inhibitor KRT-232 Pharmacokinetics and Macrophage Inhibitory Cytokine-1 (MIC-1) Response in Healthy Volunteers

Background: KRT-232 is a potent, selective, orally available, small-molecule drug that binds to mouse double minute 2 homolog (MDM2) and inhibits its interactions with tumor suppressor protein p53. KRT-232 is under development for treatment of myeloproliferative neoplasms, acute myeloid leukemia, and Merkel cell carcinoma. Increased serum MIC-1 (pg/mL) is a pharmacodynamic (PD) marker of p53-mediated activity in patients treated with KRT-232 (Allard,HemaSphere, 2020;4:S1, Abstract EP519). The aim of this study was to assess the safety and effect of a high-fat meal on KRT-232 pharmacokinetics (PK) and MIC-1 PD of a new tablet formulation in healthy volunteers. This is the first characterization of a MDM2-inhibitor-induced MIC-1 response in healthy volunteers. Methods: KRT-232-105 was a single-center, open-label, 60-mg single-dose, 3-treatment, 4-period, and 3-sequence study with a partial replicate crossover design. Volunteers (N=30) were randomized to three treatment groups: A: new tablet, fasted (reference, dosed twice in Periods 2-4); B: new tablet, 30 min after a high-fat, high-calorie meal (test 1, dosed once in periods 2-4); C: current tablet, fasted (test 2, period 1 only). Plasma KRT-232, its acyl glucuronide metabolite (M1) and serum MIC-1 concentrations were measured over 0-96 h. Urine from group C was collected over 0-48 h. Doses were one week apart. All volunteers had aH pyloribreath test and were genotyped for UGT1A1*28 polymorphisms. Results: Volunteers were 43% female, 7% African American and 77% Hispanic/Latino. Mean age was 38.1 y (range, 18-54), and mean body mass index was 26.9 kg/m2 (range, 21.4-30.9). No deaths, serious adverse events (SAEs), or discontinuations were reported. Twenty-one treatment-emergent AEs (TEAEs) were observed in 13 (43%) volunteers; constipation was the most frequent AE, followed by headache. All TEAEs were grade 1 (n=17) or grade 2 (n=4: 1 headache event [possibly study drug-related] and 3 events of headache, influenza-like illness, and pharyngitis). Mean (SD) concentration-time plots of KRT-232 and M1 were similar across the 3 groups (Figure 1a and b). A second peak was observed, consistent with enterohepatic recirculation. With a meal (test 1), KRT-232 geometric least-squares mean (GLSM) maximum concentration (Cmax) was similar (431 and 442 ng/mL (GLSM ratio [90% CI], 103% [87.4-121]) and KRT-232 GLSM area under the curve (AUC0-t) decreased from 2858 to 2325 ng∙h/mL (GLSM ratio [90% CI], 81.4 [76.2-86.9]). Median time of Cmax (Tmax) was 2 h fasted and 3 h fed. Geometric mean half life (t1/2) was unchanged (17.0 vs 17.1 h). Under fasting conditions, the current tablet (C, test 2) vs new tablet (A, reference), KRT-232 GLSM Cmax decreased from 431 to 337 ng/mL (GLSM ratio [90% CI], 78.4% [72.0-85.3]) and KRT-232 GLSM AUC0-t had a possible small decrease (2858 and 2455 ng∙h/mL, GLSM ratio [90% CI], 85.9 [80.5-91.7]). Median Tmax (~2 h) and geometric mean t1/2 (17 h) were unchanged. The fraction of the KRT-232 dose in urine as KRT-232 and M1 was negligible at 0.0201% and 0.0220% of dose, respectively. KRT-232 is a carboxylic acid with pH-dependent solubility that increases with increasing pH.H pyloriinfection, which can increase stomach pH, did not have any discernable impact on KRT-232 PK. KRT-232 and M1 exposure in heterozygous UGT1A1*28 poor metabolizers (6/7 TA repeats, N=16) was generally comparable to exposure in wild-type (WT) UGT1A1*28 (6/6 TA repeats, N=12) subjects. MIC-1 concentrations in serum were variable and followed the PK time course with a median Tmax lag of ~8-12 h. Group A: Mean Cmax 2115 pg/mL, C0 (Baseline) 170 pg/mL, AUC0-T 89267 pg*h/mL and mean t1/2 27 h. MIC-1 Cmax and AUC were generally comparable over 96 h across groups (Figure 1c).Figure 1dshows the statistically significant correlation between KRT-232 AUC0-t and MIC-1 AUC0-t. Conclusions: Based on generally comparable PK, KRT-232 can be administered with or without food, and no dose adjustment is warranted with a new tablet formulation. KRT-232 PK was not affected byH pylori, inferring that higher gastric pH did not alter absorption of KRT-232. KRT-232 exposure in UGT1A1*28 heterozygous poor metabolizers was generally comparable to WT UGT1A1*28 wild type healthy volunteers. The 60-mg KRT-232 dose elicited a reproducible and robust MIC-1 response that correlated with KRT-232 exposure, indicating MDM2-p53 target engagement. Disclosures Wong: Kartos Therapeutics:Current Employment;AbbVie Biotherapeutics:Ended employment in the past 24 months.Krejsa:Kartos Therapeutics:Current Employment;AstraZeneca:Current equity holder in publicly-traded company;Seattle Genetics:Current equity holder in publicly-traded company;Acerta Pharma:Current equity holder in private company.Lee:Kartos Therapeutics:Current Employment.Harris:Gilead Sciences:Current equity holder in publicly-traded company;Kartos Therapeutics:Current Employment, Current equity holder in private company;BeiGene:Ended employment in the past 24 months;Clovis:Current equity holder in publicly-traded company, Ended employment in the past 24 months.Simard:Certara:Current Employment;AltaScience:Ended employment in the past 24 months.Wang:Certara:Current Employment.Rubets:Certara:Current Employment.Allard:Certara:Consultancy, Ended employment in the past 24 months;CytomX Therapeutics:Ended employment in the past 24 months;Telios Pharma:Current Employment, Current equity holder in private company.Podoll:IV/PO, LLC:Consultancy.O'Reilly:Celerion:Current Employment.Slatter:Amgen:Divested equity in a private or publicly-traded company in the past 24 months;Kartos Therapeutics:Current Employment;AstraZeneca:Current equity holder in publicly-traded company. OffLabel Disclosure: Yes, KRT-232 is an investigational small molecule MDM2 inhibitor.