Clinical Trials In Advanced Cancer Research Articles

Abstract PO3-27-08: Geographic Distribution and Accessibility of Clinical Trials for Advanced-Stage Breast Cancer in the United States: A Focus on Rural and Minority Health Disparities

Abstract Background: Our research examines the geographical distribution and accessibility of clinical trials for metastatic breast cancer patients in the U.S., spotlighting the challenges faced by rural communities and minority groups. Prior research indicated nearly half of these patients would have to commute over an hour to reach a trial site. [1] Our study provides a refreshed perspective on this issue, offering a more comprehensive analysis. Methods: Utilizing the ClinicalTrials.gov portal, we identified active interventional clinical trials for metastatic breast cancer patients as of November 25, 2022. We obtained distinct zip codes linked to these trials and, using 2020 census data, estimated the proportion of the U.S. populace residing within specific distances from these sites. Our analysis encompassed ethnicity, and other socio-economic parameters. Using GIS software, we also developed illustrative maps to visually represent the U.S. clinical trial accessibility landscape. Results: The majority of Americans diagnosed with metastatic breast cancer have clinical trials within their reach. A significant 81.8% of the U.S. populace resides within a 30-mile radius of a relevant clinical trial site. However, there is significant variation among ethnic groups, especially among American Indians, where 56.5% live within 30 miles of a clinical trial site. Conclusions: While a commendable 81.8% of the U.S. population resides within 30 miles of a metastatic breast cancer clinical trial site, our data underscores the uneven geographical spread of these trials. Our findings underscore the need for strategic initiatives to ensure clinical trials are within reach for every individual, irrespective of their location or background. Reference: 1. Galsky MD, Stensland KD, McBride RB, Latif A, Moshier E, Oh WK, Wisnivesky J. Geographic accessibility to clinical trials for advanced cancer in the United States. JAMA Intern Med. 2015 Feb;175(2):293-5. PMID: 25437434. Map of 30-, 60-, and 120-mile buffers from clinical trial sites open to patients with metastatic breast cancer. The U.S. Population living withing 30-, 60-, and 120-miles of an open clinical trial site for patients with metastatic breast cancer. Citation Format: Emily Westergard, Abigail Swenson, Zachary Schroeder, Wade Swenson. Geographic Distribution and Accessibility of Clinical Trials for Advanced-Stage Breast Cancer in the United States: A Focus on Rural and Minority Health Disparities [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-27-08.

Prospects for hypoxia-based drug delivery platforms for the elimination of advanced metastatic tumors: From 3D modeling to clinical concepts

Hypoxia is a unique characteristic of the solid tumor microenvironment. Hypoxia contributes to multi-drug resistance, metastasis and cancer relapse through numerous molecular pathways, but at the same time provides an opportunity for the development of novel drugs or modalities specifically targeting hypoxic tumor regions. Given the high significance of tumor hypoxia in therapeutic results, we here discuss a variety of hypoxia-adopted strategies, and their potential and utility in the treatment of deep-seated hypoxic tumor cells. We discuss the merits and demerits of these approaches, as well as their combination with other approaches such as photodynamic therapy. We also survey the currently available 3D hypoxia modeling systems, in particular organoid-based microfluidics. Finally, we discuss the potential and the current status of preclinical tumor hypoxia approaches in clinical trials for advanced cancer. We believe that multi-modal imaging and therapeutic hypoxia adopted drug delivery platforms could provide better efficacy and safety profiles, and more importantly personalized therapy. Determining the hypoxia status of tumors could offer a second chance for the clinical translation of hypoxia-based agents, such as hypoxia activated prodrugs (HAPs) from bench to bedside.

Abstract 5314: Selinexor, a selective inhibitor of nuclear export (SINE) compound, enhances the anti-tumor activity of Eribulin in leiomyosarcoma

Abstract Leiomyosarcoma (LMS) is a rare soft tissue sarcoma (STS) that begins in smooth muscle tissue and most often initiates in the abdomen or uterus. Compared with other uterine cancers, uterine LMS is an aggressive tumor associated with poor prognosis and has a high risk of recurrence and death, regardless of stage at presentation. Selinexor is a first-in-class selective inhibitor of nuclear export (SINE) compound that binds covalently to exportin 1, thereby reactivating tumor suppressor proteins and downregulating the expression of oncogenes and DNA damage repair (DDR) proteins. Selinexor has demonstrated preclinical activity in various cancer types, including STS, and is currently in Phase I and II clinical trials for advanced cancers (Marretta et al. 2021). In this study, we evaluated the effects of Selinexor in combination with Dacarbazine, Gemcitabine, Doxorubicin, Pazopanib, Eribulin, and Trabectedin in LMS cell lines. The effects on cell viability were evaluated by treating the LMS cell lines SK-UT1 (p53-mut) and SK-UT1-B (p53 WT) with Selinexor and different chemotherapy combinations. Treatment with these drugs significantly decreased the cell proliferation and survival of SK-UT1 and SK-UT1-B cell lines tested in vitro. However, this effect was enhanced in SK-UT1 cells following treatment in the combination of Selinexor with Eribulin and Doxorubicin. The effects of treatment were also evaluated in mouse xenograft models generated with SK-UT1 cell lines. Treatment with Selinexor combined with Eribulin showed synergistic effects on tumor growth inhibition in SK-UT1 derived xenografts which warrant further investigation of these combinations at the clinical level. Citation Format: Sonam Mittal, Ishaque Pulikkal, Hua Chang, Yosef Landesman, John Charlson, Sunila Pradeep. Selinexor, a selective inhibitor of nuclear export (SINE) compound, enhances the anti-tumor activity of Eribulin in leiomyosarcoma [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 5314.

Abstract 2231: Utility of plasma tumor fraction (TF) to inform sensitivity of FoundationOne Liquid CDx (F1LCDx)

Abstract Background: F1LCDx is an FDA-approved liquid biopsy test offering pan-tumor profiling of >300 genes with CDx indications for multiple cancer types. One key limitation is that sensitivity for detection of genomic alterations in ctDNA is impaired when the plasma tumor fraction (TF) is low. TF is known to vary in advanced cancer and has been correlated with overall survival (Stover, JCO, 2018). While some ctDNA assays use variant allele fraction (VAF) to quantify tumor content, such methods may be prone to interference from germline variants, copy number alterations and a limited number of mutations. We studied SNP aneuploidy to develop a variant-independent measure of TF which we hypothesized could inform assay sensitivity. Methods: For each liquid sample, coverages from heterozygous SNPs, across the genome, were used to measure allelic deviations from normal via a root-mean-square (RMS) metric. The relationship between RMS and TF was established based on a training data set of clinical samples with known TF that were diluted in silico. In this way, the RMS metric for any sample could be linked to a distribution of TF values. TF is reported when the lower bounds of the predicted TF distribution is >0%. Positive percentage agreement (PPA) of liquid NGS versus tissue genotype was studied in those with a TF reported vs TF not quantified. Results: For a pilot concordance analysis, we studied a real-world cohort of NSCLC patients where NGS was performed on both tissue and on a 70-gene ctDNA assay (FoundationOne®Liquid (F1L), median 314 days between results). Among 251 cases with tissue NGS showing an EGFR L858R or 19del mutation and a F1L result available, the EGFR mutation was detected 90% of the time (57/63) when TF was reported (range 13-74%) but was detected 51% of the time (96/188) when TF was not quantified. Next, we analyzed a cohort of 3 clinical trials in advanced cancers where tissue genotype was known and with F1LCDx results available, including studies of activating PIK3CA mutations in breast cancer, MET exon 14 mutations in NSCLC and BRCA1/2 mutations in prostate cancer. For the subset of patients with TF reported (range 9.6-72%), PPA was 94.7% (breast, n=38), 100% (NSCLC, n=19), and 90.1% (prostate, n=46), versus 66.7% (breast, n=33), 66.7% (NSCLC, n=45) and 89.6% (prostate, n=48) for TF not quantified. Conclusions: We describe a novel method to measure TF in plasma ctDNA based on aneuploidy, which may overcome some limitations of TF measurement based on VAF. When TF confirms tumor content, sensitivity of F1LCDx for short variant detection is excellent (90%-100%), suggesting reduced value from a reflex to tissue genotyping in the absence of a targetable genomic alteration. When TF is not quantified, sensitivity can be lower and the value of reflex to tissue genotyping may be heightened. Citation Format: Meijuan Li, Bernard Fendler, Lei Yang, Russell Madison, Brennan Decker, Ole Gjoerup, Kimberly McGregor, Aparna Aiyer, Jason Hughes, Priti Hegde, Christine Vietz, Geoffrey R. Oxnard. Utility of plasma tumor fraction (TF) to inform sensitivity of FoundationOne Liquid CDx (F1LCDx) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2231.

Molecular Dynamics Study on the Binding of an Anticancer DNA G-Quadruplex Stabilizer, CX-5461, to Human Telomeric, c-KIT1, and c-Myc G-Quadruplexes and a DNA Duplex.

DNA G-quadruplex (G4) stabilizer, CX-5461, is in phase I/II clinical trials for advanced cancers with BRCA1/2 deficiencies. A FRET-melting temperature increase assay measured the stabilizing effects of CX-5461 to a DNA duplex (∼10 K), and three G4 forming sequences negatively implicated in the cancers upon its binding: human telomeric (∼30 K), c-KIT1 (∼27 K), and c-Myc (∼25 K). Without experimentally solved structures of these CX-5461-G4 complexes, CX-5461's interactions remain elusive. In this study, we performed a total of 73.5 μs free ligand molecular dynamics binding simulations of CX-5461 to the DNA duplex and three G4s. Three binding modes (top, bottom, and side) were identified for each system and their thermodynamic, kinetic, and structural nature were deciphered. The molecular mechanics/Poisson Boltzmann surface area binding energies of CX-5461 were calculated for the human telomeric (-28.6 kcal/mol), c-KIT1 (-23.9 kcal/mol), c-Myc (-22.0 kcal/mol) G4s, and DNA duplex (-15.0 kcal/mol) systems. These energetic differences coupled with structural differences at the 3' site explained the different melting temperatures between the G4s, while CX-5461's lack of intercalation to the duplex explained the difference between the G4s and duplex. Based on the interaction insight, CX-5461 derivatives were designed and docked, showing higher selectivity to the G4s over the duplex.

Abstract 14: TRAIL inducing small molecule ONC201 prevents intestinal tumors in FAP mouse model

Abstract Colorectal cancer (CRC) is a major health problem globally. Preventing CRC in the general population, and especially in high-risk cohorts with colonic polyps, or its recurrence, is a high priority. ONC201, an orally active small molecule with robust antitumor activity, is currently in clinical trials for advanced cancers. The aim of this study was to determine the CRC preventive potential of ONC201 using the Apcmin/+ mouse model for CRC in familial adenomatous polyposis. First, the optimal and non-toxic doses of ONC201 were determined. C57BL/6J mice (n=6/group) were randomized, and five different doses of ONC201 (0-100mg/kg BW) were administered orally twice a week by gavage. After six weeks of treatment, all mice were euthanized, and tissues were analyzed for optimal dose and toxicity. Based on the body weight gain, gross organ weights at termination, blood profiling, plasma liver enzyme profile, and histopathological analysis, it was concluded that there were no toxicities associated with ONC201 within the tested dose range. For efficacy evaluation, Apcmin/+ male and female mice (n≥20) were grouped and ONC201 (0, 25 and 50 mg/kg BW) was administered by gavage, twice weekly for 14 weeks. At termination, intestinal tumors were evaluated for incidence and multiplicity to determine the efficacy of ONC201. Results indicate a strong suppressive effect of ONC201 against colonic and small intestinal (SI) tumor multiplicity in mice of both genders. Colonic tumor incidence was significantly reduced by >50% in ONC201-treated (50 mg/kg BW) male (40% in treated vs. 92% in control; p<0.0002) and female mice (30% in treated vs. 81% in control; p<0.001) when compared with placebo. Colonic tumor multiplicity was reduced by 68% in ONC201-treated (50 mg/kg BW) male mice (0.44 ± 0.11 in treated vs. 1.4 ± 0.14 in control; p<0.0001) and by 75% in female mice (0.30 ± 0.10 in treated vs. 1.19 ± 0.19 in control; p<0.0003). SI polyps were suppressed by up to 68% in both male mice (11.40 ± 1.19 in treated vs. 36.08 ± 2.62 in control; p<0.0001) and female mice (9.65 ± 1.15 in treated vs. 29.24 ± 2.51 in control; p<0.0001). Snap-frozen colon tumor samples were analyzed for various biomarkers. Western blot protein analysis of the tumors suggested a dose-dependent increase in TRAIL expression upon treatment with ONC201. Similar increases were observed for DR5 and cleaved caspase 8 protein expression. Cleaved caspase 7, caspase 3, FADD and p21 were found to be increased in the treated tumor samples when compared with control. Immunohistochemical analysis indicated a significant decrease in PCNA index in the ONC201-treated tumors compared with controls. Serum analysis indicated a decrease in pro-inflammatory biomarkers, such as IL1β, IL6, TNFα, G-CSF, and GM-CSF, in the ONC201-treated samples compared to controls. Overall, chronic oral administration of ONC201 demonstrated strong chemopreventive efficacy against intestinal tumorigenesis in the Apcmin/+ mouse model. (Supported by NCI HHSN 261201500038I) Citation Format: Chinthalapally V. Rao, Venkateshwar Madka, Yuting Zhang, Gopal Pathuri, Janani Panneerselvam, Nicole Stratton, Niklas K. Finnberg, Howard P. Safran, Jennifer Fox, Shizuko Sei, Elizabeth R. Glaze, Robert Shoemaker, Wafik S. El-Deiry. TRAIL inducing small molecule ONC201 prevents intestinal tumors in FAP mouse model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 14.

How is best supportive care provided in clinical trials for patients with advanced cancer? A review of registered protocols of clinical trials.

In 2012, 11 standards describing best supportive care (bsc) in clinical trials in advanced cancer were defined through consensus statements. The consensus included 15 key components. Our objective was to analyze whether clinical trials that involved patients with advanced cancer and that included bsc in at least 1 arm met the standards and contained the key components. We reviewed clinical trials registered in ClinicalTrials.gov, the isrctn (International Standard Randomised Controlled Trial Number) registry, the EU Clinical Trials Register, and the International Clinical Trials Registry Platform for 2012-2018. We selected only phase iii studies in patients with advanced cancer that included bsc in at least 1 arm. We describe the characteristics of the trials, together with the definition and components of bsc. We analyzed how the trials met the standards and adopted the key components of bsc. Of 193 trials retrieved, only 64 met the inclusion criteria; 36 of those trials (56%) had no definition of bsc. Less than 7% of the trials included even 3 of the 8 bsc standards that were defined to be included in the design of trials. Furthermore, trials mentioned only 5 of the 15 key components that the consensus defined to be fundamental, with symptom management appearing in 22% of trials and the other 4 components appearing in less than 8%. Most clinical trials registered during 2012-2018 that involved patients with cancer and an arm with bsc did not define the bsc concept. Hence, the design of those trials does not meet the consensus recommendations.

Abstract 249: Combination of ONC201 with radiation exhibits synergistic efficacy in high grade gliomas and other advanced cancers

Abstract Background: Radiation is widely administered in many treatment settings for solid tumors. ONC201 is the first small molecule DRD2 antagonist for oncology that is being investigated in advanced cancer clinical trials as a single agent. ONC201 has exhibited preclinical and clinical anti-tumor activity in high grade gliomas and its immunostimulatory activity involving natural killer (NK) cells has been recently reported. Given that ONC201 exhibits broad synergy with anti-cancer drugs, excellent safety, and single activity in tumor types where radiation is used routinely, we evaluated the combination of ONC201 with radiation. Methods: Cell viability was evaluated in human and/or mouse breast, prostate and high grade glioma cell lines in response to ONC201 (1 - 10uM), radiation (2- 10 Gy), or the combination. Incubation times ranged from 24 to 96 hours and the sequence of the two agents in combination was varied. Results: Cell viability assays for ONC201 in combination with radiation in breast or prostate cancer cell lines revealed a cytotoxic response to the combination that was superior to either single agent. Western blot analysis of PC3 cells showed a synergistic induction of CHOP and ATF6 that are components of the integrated stress response. In glioblastoma or diffuse intrinsic pontine glioma (DIPG) cell lines, combination indices computed from cell viability experiments indicated modest synergy (~0.7 CI) for the combination ranging between 1-5 µM ONC201 and 2-10 Gy. In MDA-MB-468 breast cancer cells, Western blot analysis demonstrated a striking induction of PARP cleavage, a marker of caspase-mediated apoptosis, with 2 µM ONC201 in combination with 2 Gy radiation, whereas either single agent produced minimal PARP cleavage. In 4T1 murine triple-negative breast cancer subcutaneous tumors, the combination of oral ONC201 and radiation produced antitumor effects at subtherapeutic doses that required CD4+ T cells and NK cells. Conclusions: ONC201 combined with radiation produced additive or synergistic anti-cancer effects in high grade glioma, breast and prostate cancer in vitro and increased anti-tumor efficacy in an in vivo model of breast cancer that involved immune cells. Citation Format: Rohinton S. Tarapore, Sachin Jhawar, Mark Stein, Andrew Zloza, Sabine Mueller, Jie Zhang, Francesca Amoroso, Ian Mills, Wolfgang Oster, Joshua Allen. Combination of ONC201 with radiation exhibits synergistic efficacy in high grade gliomas and other advanced cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 249.

Abstract 3877: IND-enabling characterization of DRD2/3 imipridone antagonist ONC206 for oncology

Abstract Dopamine receptor D2 (DRD2) is a G protein-coupled receptor that is overexpressed and critical for survival in several cancers. ONC201, an imipridone small molecule, is a DRD2/3 antagonist in Phase II advanced cancer clinical trials with a compelling safety and efficacy profile. We evaluated the binding target, anti-tumor activity, biodistribution and safety of ONC206, a chemical derivative of ONC201 with the same imipridone core structure. GPCR profiling with β-Arrestin recruitment revealed that ONC206 selectively antagonizes dopamine receptors DRD2 and DRD3. ONC206 exhibited a Ki of ~320nM for DRD2 with complete specificity across human GPCRs and complete DRD2 antagonism. Schild analyses of ONC206 in cAMP and β-Arrestin recruitment assays revealed hallmarks of non-competitive DRD2 antagonism, unlike antipsychotics but similar to ONC201. Shotgun mutagenesis across DRD2 identified 7 residues critical for ONC206-mediated antagonism at orthosteric and allosteric sites. While 6 mutated residues were also critical for ONC201-mediated antagonism, the impact and magnitude of different mutants varied between the two compounds and one of the allosteric residues was unique to ONC206. In vitro profiling of ONC206 in >1000 GDSC cancer cell lines demonstrated broad nanomolar efficacy (GI50 <78-889nM). TCGA and tissue microarrays analyses revealed that malignant DRD2 expression was highest in pheochromocytoma, high grade gliomas, neuroblastoma, medulloblastoma, Ewing’s sarcoma and cholangiocarcinoma. Accordingly, ONC206 demonstrated nanomolar in vitro sensitivity in these tumor types. Similar to ONC201, a DRD2+/DRD5- RNA expression signature in the GDSC panel predicted significantly enhanced ONC206 sensitivity. ONC206 reduced the viability of normal human fibroblasts at micromolar doses (GI50 > 5µM), suggesting a wide therapeutic window. Robust inhibition of tumor growth without body weight loss was observed in HuCCT1 cholangiocarcinoma and MHH-ES-1 Ewing’s sarcoma subcutaneous xenografts with 50-100 mg/kg oral ONC206 weekly or every 2 weeks. Biodistribution studies in Sprague-Dawley rats revealed a ~12 µM plasma Cmax with a half-life of ~6 hours upon a single oral dose of 50 mg/kg. Additionally, 5-10 fold higher ONC206 concentrations were observed in adrenal gland, bile duct, brain and bone marrow relative to plasma concentrations. GLP toxicology studies with weekly oral ONC206 in Sprague-Dawley rats and beagle dogs at doses above or equivalent to efficacious doses revealed no dose-limiting toxicities. In both species, observations at the highest dose were mild and reversible. The no observed adverse event level (NOAEL) was ≥ 16.7 mg/kg in dogs and ≥ 50 mg/kg in rats, which both correspond to a human dose of approximately 500 mg assuming standard allometric scaling. These results provide rationale for a 50 mg starting ONC206 dose in dose escalation clinical trials in patients with DRD2-dysregulated tumors. Citation Format: Varun V. Prabhu, Abed Rahman Kawakibi, Neel Madhukar, Mathew J. Garnett, Ultan McDermott, Cyril H. Benes, Lakshmi Anantharaman, Neil Charter, Sean Deacon, Alexander VanEngelenburg, Joseph B. Rucker, Benjamin J. Doranz, Jessica Rusert, Robert Wechsler-Reya, Olivier Elemento, Martin Stogniew, Wolfgang Oster, Sharon DeMorrow, R. Benjamin Free, David R. Sibley, Joshua E. Allen. IND-enabling characterization of DRD2/3 imipridone antagonist ONC206 for oncology [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3877.

DDIS-16. ONC201 IN COMBINATION WITH RADIATION EXHIBITS SYNERGISTIC EFFICACY IN HIGH GRADE GLIOMAS AND OTHER ADVANCED CANCERS

INTRODUCTION ONC201 is the first small molecule DRD2 antagonist for oncology that is being investigated as a single agent in advanced cancer clinical trials. Downstream of DRD2 antagonism, ONC201 activates the integrated stress response pathway and apoptosis. ONC201 has exhibited preclinical and clinical anti-tumor activity in high grade gliomas. Given that ONC201 exhibits broad synergy with anti-cancer drugs, excellent safety, and single agent activity in tumor types where radiation is used routinely, we evaluated the combination of ONC201 with radiation in solid tumors.

Abstract 4874: Receptor pharmacology and anti-cancer activity of selective DRD2/3 antagonist imipridone ONC206

Abstract Dopamine receptor D2 (DRD2) is a G protein-coupled receptor (GPCR) overexpressed in many cancers and its antagonism causes anti-tumor effects. ONC201, founding member of the imipridone class of small molecules, is a DRD2 antagonist in Phase II advanced cancer clinical trials. We evaluated the binding target and anti-tumor activity of ONC206, an ONC201 analog. An orphan small molecule target prediction algorithm revealed that ONC206, like ONC201, antagonizes DRD2. Experimental GPCR profiling using the PathHunter® β-Arrestin assay, confirmed that ONC206 selectively antagonizes D2-like (DRD2/3) but not D1-like (DRD 1/5) dopamine receptors. In this assay, ONC206 possesses a ~10-fold increased potency for DRD2 compared to ONC201 with a Ki of ~320nM with selectivity that was superior to approved antipsychotics. Shotgun mutagenesis across 350 amino acids of DRD2 identified 7 residues critical for ONC206-mediated antagonism of DRD2-induced calcium flux. Consistent with competitive inhibition, mutated residues were within the orthosteric binding site. While 6 mutated residues were also critical for ONC201 activity, one of the mutated residues was unique to ONC206, suggesting differentiated receptor pharmacology. TCGA analysis and immunohistochemistry of patient-derived tissue microarrays revealed DRD2 was overexpressed in neuroblastoma, sarcoma and pheochromocytoma specimens relative to normal tissues. In vitro profiling of ONC206 in the Genomic of Drug Sensitivity in Cancer collection of cell lines revealed broad nanomolar efficacy across most tumor types (GI50 <78-889nM) and ~5 to 20-fold improved potency relative to ONC201. Bone cancer and neuroblastoma were identified as the most ONC206-responsive solid tumor types that were comparatively less responsive to ONC201. Within bone cancer, Ewing's sarcoma (n=16) was most sensitive to ONC206 with nanomolar sensitivity (GI50 168-303nM) that was superior to ONC201. ONC206 was highly efficacious in neuroblastoma (n=35, GI50 87-589nM) including cell lines derived from metastatic sites and with MYCN amplification associated with poor prognosis. In the PC12 rat pheochromocytoma cell line ONC206 (GI50 200nM) was superior to ONC201. ONC206 time-course experiments revealed anti-cancer effects occurring at 48-72 post-treatment, similar to ONC201. In support of a wide therapeutic window, ONC206 reduced the viability of normal human fibroblasts at relatively high doses (GI50 > 5µM). Efficacy evaluation in the MHH-ES-1 Ewing's sarcoma xenograft model demonstrated that ONC206 (100 mg/kg PO every 10 days) causes significant tumor growth inhibition that was comparable to methotrexate (400 mg/kg, IP) while being better tolerated. Thus, imipridone ONC206 acts as a selective antagonist of DRD2/3 at nanomolar concentrations and may address tumor types where the properties of ONC201 do not permit for complete therapeutic engagement in vivo. Citation Format: Varun Vijay Prabhu, Neel Madhukar, Rohinton Tarapore, Mathew Garnett, Ultan McDermott, Cyril Benes, Neil Charter, Sean Deacon, Alexander VanEngelenburg, Joseph Rucker, Benjamin Doranz, Olivier Elemento, Wolfgang Oster, Martin Stogniew, Joshua Allen. Receptor pharmacology and anti-cancer activity of selective DRD2/3 antagonist imipridone ONC206 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4874.

Cancer stem cell-related gene expression as a potential biomarker of response for first-in-class imipridone ONC201 in solid tumors.

Cancer stem cells (CSCs) correlate with recurrence, metastasis and poor survival in clinical studies. Encouraging results from clinical trials of CSC inhibitors have further validated CSCs as therapeutic targets. ONC201 is a first-in-class small molecule imipridone in Phase I/II clinical trials for advanced cancer. We have previously shown that ONC201 targets self-renewing, chemotherapy-resistant colorectal CSCs via Akt/ERK inhibition and DR5/TRAIL induction. In this study, we demonstrate that the anti-CSC effects of ONC201 involve early changes in stem cell-related gene expression prior to tumor cell death induction. A targeted network analysis of gene expression profiles in colorectal cancer cells revealed that ONC201 downregulates stem cell pathways such as Wnt signaling and modulates genes (ID1, ID2, ID3 and ALDH7A1) known to regulate self-renewal in colorectal, prostate cancer and glioblastoma. ONC201-mediated changes in CSC-related gene expression were validated at the RNA and protein level for each tumor type. Accordingly, we observed inhibition of self-renewal and CSC markers in prostate cancer cell lines and patient-derived glioblastoma cells upon ONC201 treatment. Interestingly, ONC201-mediated CSC depletion does not occur in colorectal cancer cells with acquired resistance to ONC201. Finally, we observed that basal expression of CSC-related genes (ID1, CD44, HES7 and TCF3) significantly correlate with ONC201 efficacy in >1000 cancer cell lines and combining the expression of multiple genes leads to a stronger overall prediction. These proof-of-concept studies provide a rationale for testing CSC expression at the RNA and protein level as a predictive and pharmacodynamic biomarker of ONC201 response in ongoing clinical studies.

ONC201 Demonstrates Antitumor Effects in Both Triple-Negative and Non-Triple-Negative Breast Cancers through TRAIL-Dependent and TRAIL-Independent Mechanisms.

Breast cancer is a major cause of cancer-related death. TNF-related apoptosis-inducing ligand (TRAIL) has been of interest as a cancer therapeutic, but only a subset of triple-negative breast cancers (TNBC) is sensitive to TRAIL. The small-molecule ONC201 induces expression of TRAIL and its receptor DR5. ONC201 has entered clinical trials in advanced cancers. Here, we show that ONC201 is efficacious against both TNBC and non-TNBC cells (n = 13). A subset of TNBC and non-TNBC cells succumbs to ONC201-induced cell death. In 2 of 8 TNBC cell lines, ONC201 treatment induces caspase-8 cleavage and cell death that is blocked by TRAIL-neutralizing antibody RIK2. The proapoptotic effect of ONC201 translates to in vivo efficacy in the MDA-MB-468 xenograft model. In most TNBC lines tested (6/8), ONC201 has an antiproliferative effect but does not induce apoptosis. ONC201 decreases cyclin D1 expression and causes an accumulation of cells in the G1 phase of the cell cycle. pRb expression is associated with sensitivity to the antiproliferative effects of ONC201, and the compound synergizes with taxanes in less sensitive cells. All non-TNBC cells (n = 5) are growth inhibited following ONC201 treatment, and unlike what has been observed with TRAIL, a subset (n = 2) shows PARP cleavage. In these cells, cell death induced by ONC201 is TRAIL independent. Our data demonstrate that ONC201 has potent antiproliferative and proapoptotic effects in a broad range of breast cancer subtypes, through TRAIL-dependent and TRAIL-independent mechanisms. These findings develop a preclinical rationale for developing ONC201 as a single agent and/or in combination with approved therapies in breast cancer. Mol Cancer Ther; 16(7); 1290-8. ©2017 AACR.

Abstract 4147A: Potent anti-cancer activity of the imipridone ONC206: A selective dopamine D2-like receptor antagonist

Abstract DRD2 is a G protein-coupled receptor (GPCR) that is overexpressed in many cancers, controls an array of pro-survival signaling pathways, and its antagonism causes anti-cancer effects. ONC201, the founding member of the imipridone class of anti-cancer compounds, is a small molecule DRD2 antagonist that is in Phase I/II advanced cancer clinical trials. In this study, we evaluated the binding target and antitumor activity of ONC206, a chemical analogue of ONC201. An orphan small molecule target prediction algorithm revealed that ONC206, like ONC201, antagonizes DRD2. Experimental GPCR profiling using the PathHunter® β-Arrestin assay, determined that ONC206 selectively antagonizes the D2-like (DRD2/3/4), but not the D1-like (DRD 1/5), subfamily of dopamine receptors. ONC206 possesses a ~10-fold increased affinity for DRD2 compared to ONC201 with a Ki of ~320nM with selectivity that was superior to approved antipsychotics. The increased association rate for the ONC206-DRD2 interaction was responsible for the increased affinity, whereas the dissociation rate was similar to ONC201 and atypical antipsychotics that are well tolerated. TCGA analysis and immunohistochemistry of patient-derived tissue microarrays revealed DRD2 was overexpressed in neuroblastoma, sarcoma and pheochromocytoma specimens relative to normal tissues. In vitro efficacy profiling of ONC206 in the Genomic of Drug Sensitivity in Cancer collection of cell lines revealed broad efficacy across most tumor types (GI50 <78-889nM). Bone cancer and neuroblastoma were identified as the most ONC206-responsive solid tumor types that were comparatively less responsive to ONC201. Within bone cancer cell lines, Ewing’s sarcoma (n=16) was the most sensitive to ONC206 with nanomolar sensitivity (GI50 168-303nM) that was superior to ONC201. ONC206 was highly efficacious in neuroblastoma (n=35, GI50 87-589nM) including cell lines derived from metastatic sites and with MYCN amplification associated with poor prognosis. In the PC12 rat pheochromocytoma cell line ONC206 (GI50 200nM) was superior to ONC201. ONC206 time-course experiments revealed anti-cancer effects occurring at 48-72 post-treatment, similar to ONC201. In support of a wide therapeutic window, ONC206 reduced the viability of normal fibroblasts (HFF-1) at relatively high doses (GI50 > 5µM). Efficacy evaluations in MHH-ES-1 athymic nude mice xenografts demonstrated that ONC206 (100 mg/kg PO every 10 days) causes significant tumor growth inhibition that was comparable to methotrexate (400 mg/kg, IP) while being better tolerated. In summary, ONC206 is an imipridone that acts as a selective antagonist of DRD2 at nanomolar concentrations and has broad-spectrum anti-tumor activity. ONC206 may address tumor types where the properties of ONC201 do not permit for complete therapeutic engagement in vivo. Citation Format: Varun Vijay Prabhu, Neel Madhukar, Jessica Wagner, Rohinton Tarapore, Mathew Garnett, Ultan McDermott, Cyril Benes, Neil Charter, Sean Deacon, Alexander VanEngelenburg, Olivier Elemento, Wafik El-Deiry, Martin Stogniew, Wolfgang Oster, Joshua Allen. Potent anti-cancer activity of the imipridone ONC206: A selective dopamine D2-like receptor antagonist [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4147A. doi:10.1158/1538-7445.AM2017-4147A

Abstract 2792: The small molecule imipridone ONC201 is active in tumor types with dysregulation of the DRD2 pathway

Abstract ONC201 is the lead small molecule of the imipridone class of anti-cancer compounds that is currently being evaluated in phase I/II advanced cancer clinical trials. ONC201 is a highly selective antagonist of the G protein-coupled receptor dopamine receptor D2 (DRD2) that has exhibited promising anti-cancer efficacy and an exceptional safety profile. In the current study, we evaluated the influence of the DRD2 pathway on the responsiveness of tumors to ONC201 in preclinical and clinical studies. In vitro and in vivo studies have previously demonstrated robust ONC201 efficacy in glioblastoma (Allen et al 2013) and lymphoma (Ishizawa et al 2016) models. ONC201 Phase I trials have also revealed evidence of clinical benefit in endometrial cancer (Stein et al 2016). In vitro efficacy profiling of ONC201 in the Genomic of Drug Sensitivity in Cancer (GDSC) collection of cell lines confirmed broad-spectrum anti-cancer efficacy with particularly high sensitivity in lymphoma, neuroblastoma, endometrial and brain cancer. DRD2 is overexpressed in many cancers and DRD2 antagonism kills cancer cells via the same signaling pathways that are altered in response to ONC201. Results from the Project Achilles screen indicate that anti-cancer effects of DRD2 knockdown in various tumor types correlated with overall ONC201 efficacy. In particular, we noted that lymphoma cells are highly sensitive to DRD2 knockdown- a tumor type where ONC201 performs well. Gene expression analysis of samples in the Cancer Genome Atlas (TCGA) revealed high DRD2 expression in ONC201-sensitive tumor types, such as lymphoma and glioblastoma, and that high expression of DRD2 in glioma was associated with a poor prognosis. High DRD2 expression was also observed in neuroendocrine prostate cancer relative to other prostate cancer subtypes. In immunohistochemistry analyses of patient-derived tumor tissue microarrays, DRD2 overexpression was particularly noted in endometrial cancer, neuroblastoma and pheochromocytoma relative to normal tissues. The anti-cancer activity of ONC201 in pheochromocytoma and neuroendocrine prostate cancer was confirmed in cell viability assays. In ONC201-treated patients, ELISA was used to quantitate serum prolactin levels, a clinical biomarker of DRD2 antagonism. A 2-fold mean induction of prolactin, was detected in the serum of ONC201-treated patients, in accordance with physiological DRD2 antagonism. Interestingly, expression of DRD5 (a D1-like dopamine receptor), which counteracts DRD2 signaling, was significantly negatively correlated with ONC201 in vitro potency in the NCI60 and GDSC dataset (P <.05). Furthermore, a missense DRD5 mutation was identified in cancer cells with acquired resistance to ONC201. In conclusion, the DRD2 pathway is expressed in ONC201-sensiive tumors and may provide biomarkers of response. Citation Format: Neel Madhukar, Varun Vijay Prabhu, Etienne Dardenne, Faye Doherty, Alexander VanEngelenburg, Rohinton Tarapore, Mathew Garnett, Ultan McDermott, Cyril Benes, Wolfgang Oster, Wafik El-Deiry, Mark Stein, David Rickman, Joshua Allen, Olivier Elemento. The small molecule imipridone ONC201 is active in tumor types with dysregulation of the DRD2 pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2792. doi:10.1158/1538-7445.AM2017-2792

Abstract 1155: Potent anti-cancer effects of selective GPR132/G2A agonist imipridone ONC212 in leukemia and lymphoma

Abstract ONC201, founding member of the imipridone class of compounds, is a highly selective small molecule G protein-coupled receptor (GPCR) antagonist that is in Phase I/II advanced cancer clinical trials. In this study, we evaluated GPCR engagement and antitumor activity of ONC212, an imipridone that is a chemical analogue of ONC201. Experimental GPCR profiling using the PathHunter® β-Arrestin assay, determined that ONC212 is a selective agonist of the orphan GPCR GPR132/G2A. Multidose validation confirmed nanomolar GPR132 agonist activity (EC50 ~400nM). GPR132 is a stress-inducible orphan GPCR that causes G2/M arrest. The tumor suppressive role of GPR132 has been demonstrated most notably in lymphoid leukemia. Gene expression analysis of samples in the Cancer Genome Atlas (TCGA) revealed GPR132 is expressed in a range of tumor types with highest expression in leukemia and lymphoma. The in vitro efficacy of ONC212 was assessed in the Genomic of Drug Sensitivity in Cancer (GDSC) collection of cell lines (>1,000 cell lines). Cell viability assays were performed at 72 hours post-treatment to generate dose responses curves at concentrations from 78nM up to 20μM. ONC212 was broadly efficacious across most solid tumors and hematological malignancies in the low nanomolar range. Ranking the sensitivity of cancer lines to ONC212 by tumor type revealed that leukemia and lymphoma are the most responsive tumor types based on completeness of response (area under the dose-response curve). Interestingly, we also observed that high expression of GPR132 significantly correlated with ONC212 efficacy in GDSC cell lines, suggesting the importance of GPR132 agonist activity for ONC212 efficacy. ONC212 was tested in 62 human leukemia cell lines that included acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myelogenous leukemia (CML) and hairy cell leukemia. ONC212 demonstrated broad spectrum anti-leukemic activity and was equally efficacious across all leukemia subtypes tested. Most cell lines (60/62) were responsive to ONC212 with GI50 ranging from <78nM to 456nM. Within ALL, both B-cell and T-cell ALL were highly sensitive to ONC212. ONC212 reduced cell viability in AML independent of complex karyotypes and p53 mutations that are associated with poor clinical prognoses. ONC212 was also tested in 58 lymphoma cell lines comprised of anaplastic large cell lymphoma, Burkitt's lymphoma, cutaneous T-cell lymphoma (CTCL), diffuse large B-cell lymphoma (DLBCL), Mantle cell lymphoma (MCL), Follicular Lymphoma and Hodgkin’s lymphoma. ONC212 reduced cell viability in most cell lines (56/58) and was equally efficacious regardless of subtypes with GI50 ranging from <78nM to 261nM. Thus, GPR132 agonist ONC212 possesses robust anti-cancer activity in hematological malignancies irrespective of leukemia and lymphoma subtype and provides further validation of the anti-cancer efficacy of the novel imipridone class of small molecules. Citation Format: Varun Vijay Prabhu, Neel Madhukar, Rohinton Tarapore, Mathew Garnett, Ultan McDermott, Cyril Benes, Neil Charter, Sean Deacon, Wolfgang Oster, Michael Andreeff, Olivier Elemento, Martin Stogniew, Joshua Allen. Potent anti-cancer effects of selective GPR132/G2A agonist imipridone ONC212 in leukemia and lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1155. doi:10.1158/1538-7445.AM2017-1155

Feasibility and acceptability of a best supportive care (BSC) checklist among clinicians.

e21682 Background: Some clinical trials for advanced cancer compare experimental therapy to BSC. Usually BSC is not standardized across sites, consistent with best available evidence in palliative care practice, or described in sufficient detail. We developed a consensus-based checklist to document BSC delivery, including symptom management, decision making, and care planning. We hypothesized that BSC can be feasibly documented with this checklist consistent with Consolidated Standards Of Reporting Trials (CONSORT) statements. Methods: Clinicians at 4 academic centers were asked to complete the BSC checklist at each encounter with eligible cancer patients. Enrolled physicians completed a survey regarding use of the checklist during clinic appointments. Descriptive statistics and frequencies were generated. Results: 15 clinicians completed the checklist survey, 9 of whom were advanced practice providers. Mean age was 41 (SD = 7.9). Mean number of years in practice since fellowship for physicians was 7.2 (SD = 4.5). Represented were medical oncology (n = 8), gynecologic oncology (n = 4), palliative care (n = 2), and other (n = 1). For “overall impact on your delivery of supportive/palliative care,” 40% noted improved impact with the checklist. For “overall impact on your documentation of supportive/palliative care,” 46% noted improvement. Impact on “frequency of comprehensive symptom assessment” was 33% “increased.” Impact on “frequency with which you assessed for referral to support services” was 26% “increased.” Impact on “frequency with which you educated patients regarding goals of therapy” was 20% “increased.” No one noted decreased frequency or worsening impact. Regarding feasibility of integrating BSC in workflow, 73% agreed or strongly agreed that the BSC checklist could be easily integrated; 73% saw value in integration; and 80% found it easy to use. Conclusions: Clinicians viewed the BSC checklist favorably. While a small sample, this illustrates proof of concept, minor impact on provider workflow, and potential benefit to patients for use in a future randomized trial.

Single Agent and Combinatorial Efficacy of First-in-Class Small Molecule ONC201 in Acute Leukemia and Multiple Myeloma

ONC201 is the founding member of the imipridone class of anti-cancer small molecules that possess a unique core chemical structure. ONC201 is currently being evaluated in several Phase I/II clinical trials for advanced cancers. In the current study, we evaluated the single agent and combinatorial efficacy of ONC201 in preclinical models of acute leukemia and multiple myeloma (MM).In acute leukemia, we evaluated ONC201 anti-cancer effects in acute myeloid leukemia (AML) (Kasumi-1, HL60) and acute lymphoblastic leukemia (ALL) (Reh, Jurkat and MOLT-4) cell lines. We observed a time- and dose-dependent decrease in cell viability for every cell line in the panel (EC50 1-5 µM). Vincristine-resistant cells HL60/VCR were also sensitive to single agent ONC201 with EC50 values on par with corresponding vincristine-sensitive parental cells. Dose- and time-dependent induction of apoptosis was noted in Western blot analysis of caspase-3 cleavage in AML cell lines treated with 2.5 µM or 5 µM of ONC201 for 48 hr. Western Blot analysis further demonstrated inhibition of Akt and Foxo3a phosphorylation in Kasumi-1 cells, in line with the previously reported late-stage signaling effects of ONC201 in solid tumor cells (Allen et al, 2013). Sub-G1 analysis indicated that ONC201 induces apoptosis in ALL cells and a pan-caspase inhibitor reduced ONC201-mediated apoptosis. Western blot analysis revealed ONC201-mediated apoptosis involves PARP cleavage and caspase-9 activation in ALL cells. Anti-apoptotic Bcl-2 family members Bcl-2 and Bcl-xl were downregulated while the pro-apoptotic Bcl-2 family member Bim is upregulated in response to ONC201 treatment in ALL cells. ONC201 also downregulates the inhibitor of apoptosis (IAP) family proteins cIAP1 and cIAP2 in ALL cells. We observed inhibition of Akt phosphorylation upon ONC201 treatment of ALL cells. Fresh AML patient cells were also found to be sensitive to ONC201 in cell viability and caspase 3/7 activity assays at 5µM.We observed that independent clones of cancer cells with acquired resistance to ONC201 were more sensitive to cytarabine compared to parental ONC201-sensitive cancer cells. In addition, ONC201 demonstrated synergistic reduction in cell viability in combination with cytarabine in AML cell lines. Determination of combination indices (CI) revealed synergy at several concentrations (CI 0.336-0.75 in CMK cells). Also, ONC201 combined additively with midostaurin in CMK cells and vincristine in HL60/VCR cells. Thus, ONC201 is a promising combinatorial partner for AML therapies based on these preclinical sensitization results.In accordance with ONC201-mediated activation of the integrated stress response that B cells are highly sensitive to (Kline et al and Ishizawa et al, 2016), MM was identified as one of the most ONC201-sensitive tumor types in the Genomics of Drug Sensitivity in Cancer collection of cell lines. Three human MM cell lines were used for validation (KMS18, MM.1S and RPMI-8226), which revealed a time- and dose-dependent decrease in cell viability (EC50 1-2.5 µM). Bortezomib-resistant cells MM.1S 33X were sensitive to ONC201 as a single agent with EC50 values comparable to bortezomib-sensitive parental cells. We observed an average of 10-fold induction of ONC201-mediated apoptosis using Sub-G1 analyses in MM cells at 5 µM, 48 hrs post-treatment. Rescue of ONC201-mediated apoptosis was demonstrated using the pan-caspase inhibitor (Z-VAD-FMK). In addition, Western blot analysis in MM cells indicated a dose-dependent decrease in the anti-apoptotic protein XIAP which is a key mediator of apoptosis inhibition and is reported to be highly up-regulated in MM cells. Furthermore, ONC201 demonstrated synergistic reduction in cell viability at various concentrations in combination with either ixazomib or dexamethasone, which are used in the clinical treatment of MM, in RPMI8226 cells (CI 0.228-0.75). Also, ONC201 combined additively with bortezomib in RPMI8226 and MM.1S 33X cells.In summary, these preclinical studies support the ongoing ONC201 single agent trials in acute leukemias and MM. Our findings suggest that ONC201 may be an important therapeutic option for patients with hematological malignancies who have developed resistance to approved therapies. Additionally, our results point to specific standard-of-care therapies that may be combined with ONC201 to exert durable responses without adding to the burden of toxicity. DisclosuresPrabhu:Oncoceutics: Employment. Tarapore:Oncoceutics: Employment, Equity Ownership. Oster:Oncoceutics: Employment, Equity Ownership. Allen:Oncoceutics: Employment, Equity Ownership. El-Deiry:Oncoceutics: Equity Ownership.

Potent Anti-Leukemic Effects of Small Molecule ONC212, a Member of the Imipridone Class of Anti-Cancer Compounds

ONC201, the founding member of the imipridone class of anti-cancer compounds, is a highly selective small molecule GPCR antagonist that is in Phase I/II advanced cancer clinical trials. In this study, we evaluated the anti-cancer effects of ONC212, an ONC201 analogue that possess the same unique core chemical structure shared by imipridones.The in vitro efficacy of ONC212 was assessed in the Genomics of Drug Sensitivity in Cancer collection of cell lines (>1,000 cell lines). Cell viability assays were performed to generate dose responses curves at concentrations from 78nM upto 20uM and at 72 hours post-treatment. ONC212 was broadly efficacious across most solid tumors and hematological malignancies in the low nanomolar range. Ranking the ONC212 sensitivity dataset revealed that leukemia is the most responsive tumor type based on completeness of response (area under the dose-response curve, AUC).ONC212 was tested in 65 leukemia cell lines in this study that is comprised of acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myelogenous leukemia (CML) and hairy cell leukemia. ONC212 demonstrated broad spectrum anti-leukemic activity and was equally efficacious across all leukemia subtypes tested, in terms of AUC. Most cell lines (63/65) were responsive to ONC212 with GI50 ranging from <78nM to 312nM. Within ALL, both B-cell and T-cell ALL were highly sensitive to ONC212. ONC212 reduced cell viability in AML independent of complex karyotypes that are associated with poor clinical prognoses.Thus, ONC212 possesses robust anti-leukemic activity irrespective of subtype and provides further validation of the anti-cancer efficacy of the novel imipridone class of small molecules. DisclosuresPrabhu:Oncoceutics: Employment. Tarapore:Oncoceutics: Employment, Equity Ownership. El-Deiry:Oncoceutics: Equity Ownership. Stogniew:Oncoceutics Inc.: Employment, Equity Ownership. Oster:Oncoceutics: Employment, Equity Ownership. Allen:Oncoceutics: Employment, Equity Ownership.

Abstract 3022: BAY 1143572, a first-in-class, highly selective, potent and orally available inhibitor of PTEFb/CDK9 currently in Phase I, shows convincing anti-tumor activity in preclinical models of acute myeloid leukemia (AML)

Abstract PTEFb/CDK9 mediated transcription of short-lived anti-apoptotic survival proteins like Mcl-1 and Myc, plays a critical role in cancer cell growth and survival in various tumor entities including AML. In addition, these survival proteins exhibit important functions in the development of resistance to chemotherapy. In contrast to pan-CDK inhibitors, to our knowledge PTEFb selective inhibitors have not been explored for clinical utility. We report the preclinical activity of BAY 1143572, a novel selective PTEFb/CDK9 inhibitor (AACR; Cancer Res 2015;75(15 Suppl):Abstract nr DDT02-02) currently being investigated in Phase I clinical trials in advanced cancer (NCT01938638) and acute leukemia (NCT02345382) in various in vitro, ex vivo and in vivo models of AML. BAY 1143572 inhibited the proliferation of 7 MLL-rearrangements positive and negative AML cell lines with a median IC50 of 385 nM (range 230-1100 nM) and induced apoptosis. Furthermore, BAY 1143572 showed potent in vitro activity in 8 out of 10 non-MLL-rearranged patient derived AML samples incl. NPM1 mutant and Flt3-ITD positive samples derived from intermediate and high risk patients. Moreover, we elucidated the dynamic changes of the cellular proteome/phosphoproteome upon pharmacological and genetic PTEFb inhibition and identified PTEFb interaction partners in various AML in vitro models. These analyses uncover the oncogenic PTEFb-dependent signaling networks and substantiate the molecular rationale for the use of PTEFb inhibitors in this indication. When applied in vivo, BAY 1143572 exhibited single agent efficacy at tolerated doses in 4 out of 5 AML xenograft tumor models in mice and in 2 out of 2 AML xenograft tumor models in rats upon once daily oral administration. Of note, partial or even complete remissions could be achieved in several models. Furthermore, intermittent dosing schedules with up to 4 days treatment pauses were feasible in terms of efficacy and tolerability. Using MOLM-13 xenografts in mice and rats to address the in vivo MoA of BAY 1143572, a transient inhibition of RNA polymerase II phosphorylation, MYC mRNA and protein levels, MCL-1 mRNA and protein levels, and an induction of apoptosis was documented. In conclusion, our data provide the rationale for the initiation of clinical development of BAY 1143572 as a potent and highly selective inhibitor of PTEFb/CDK9 with first-in-class potential for the treatment of AML patients. A phase I clinical trial to determine the safety, tolerability and recommended Phase 2 dose in this indication is ongoing (NCT02345382). Citation Format: Arne Scholz, Thomas Oellerich, Akhtar Hussain, Sarah Lindner, Ulrich Luecking, Annette O. Walter, Peter Ellinghaus, Ray Valencia, Franz von Nussbaum, Dominik Mumberg, Michael Brands, Stuart Ince, Hubert Serve, Karl Ziegelbauer. BAY 1143572, a first-in-class, highly selective, potent and orally available inhibitor of PTEFb/CDK9 currently in Phase I, shows convincing anti-tumor activity in preclinical models of acute myeloid leukemia (AML). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3022.