Supplementary Table 1. Statistical Assumption and Sample Size Estimates for MUCE Design

Supplementary Table 2. TEAEs Occurring in at Least 15% of Dose Escalation Patients

Purpose: In preclinical models, glucocorticoid receptor (GR) signaling drives resistance to taxane chemotherapy in multiple solid tumors via upregulation of antiapoptotic pathways. ORIC-101 is a potent and selective GR antagonist that was investigated in combination with taxane chemotherapy as an anticancer regimen preclinically and in a phase 1 clinical trial.Patients and Methods: The ability of ORIC-101 to reverse taxane resistance was assessed in cell lines and xenograft models, and a phase 1 study (NCT03928314) was conducted in patients with advanced solid tumors to determine the dose, safety, and antitumor activity of ORIC-101 with nab-paclitaxel.Results: ORIC-101 reversed chemoprotection induced by glucocorticoids in vitro and achieved tumor regressions when combined with paclitaxel in both taxane-na & iuml;ve and -resistant xenograft models. In the phase 1 study, 21 patients were treated in dose escalation and 62 patients were treated in dose expansion. All patients in dose expansion had previously progressed on a taxane-based regimen. In dose escalation, five objective responses were observed. A preplanned futility analysis in dose expansion showed a 3.2% (95% confidence interval, 0.4-11.2) objective response rate with a median progression-free survival of 2 months (95% confidence interval, 1.8-2.8) across all four cohorts, leading to study termination. Pharmacodynamic analysis of tissue and plasma showed GR pathway downregulation in most patients in cycle 1.Conclusions: ORIC-101 with nab-paclitaxel showed limited clinical activity in taxane-resistant solid tumors. Despite clear inhibition of GR pathway signaling, the insufficient clinical signal underscores the challenges of targeting a single resistance pathway when multiple mechanisms of resistance may be in play.Significance: Glucocorticoid receptor (GR) upregulation is a mechanism of resistance to taxane chemotherapy in preclinical cancer models. ORIC-101 is a small molecule GR inhibitor. In this phase 1 study, ORIC-101 plus nab-paclitaxel did not show meaningful clinical benefit in patients who previously progressed on taxanes despite successful GR pathway downregulation.

GR antagonism by ORIC-101 overcomes taxane resistance in preclinical models. A and B, Effect of ORIC-101 on dexamethasone-induced chemoprotection in vitro as measured by (A) caspase 3/7 apoptosis assays and (B) colony formation assays, in three TNBC lines (HCC1806, MDA-MB-231, Hs578T), three PDAC lines (BxPC3, SW1990, PSN1), and ovarian cancer line COV362. Veh: vehicle; Dex: 30 nmol/L dexamethasone; 101: 0.5 μmol/L ORIC-101; Chemo = 100 nmol/L paclitaxel + 100 nmol/L gemcitabine; PTX = 100 nmol/L paclitaxel; DTX = 100 nmol/L docetaxel; Gem = 100 nmol/L gemcitabine. A, The caspase activities of Veh were assigned as 1, and the values for other conditions were relative to Veh. One representative experiment with three biological repeats is shown (mean ± SEM). *, P < 0.05; **, P < 0.01; ***, P < 0.001 by one-way ANOVA using Tukey’s test to correct for multiple comparisons. B, One representative experiment with three biological repeats is shown. Numbers in white indicate the percentage of confluency quantitated by Celigo S. C, Effect of ORIC-101 on paclitaxel response in taxane-naïve HCC1806 TNBC xenografts in cortisol-treated mice. Mice were treated with paclitaxel 20 mg/kg by intraperitoneal injection every 3 days for a total of eight cycles (20 mg/kg, IP, Q3D × 8), cortisol (100 mg/L in drinking water, ad libitum) or ORIC-101 75 mg/kg by oral administration twice daily (75 mg/kg, PO, BID) starting on day 0 for the duration of the study. Arrowheads indicate PTX dosing days. Data are displayed as mean ± SEM. D and E, Effect of ORIC-101 in paclitaxel-relapsed HCC1806 TNBC xenografts in cortisol-treated mice. D, Animals were dosed with paclitaxel (15 mg/kg, IP, Q3Dx5) as indicated by the black arrowheads or ORIC-101 (150 mg/kg, PO, QD) as indicated by gray line. n = 15 in each group. Data is displayed as mean ± SEM. E, PFS, defined as the time elapsed between treatment initiation of the second cycle of paclitaxel and tumor progression or death from any cause, as a percentage of all animals in each cohort. A Kaplan–Meier plot was constructed to show the percentage of animals remaining in the study following treatment (P < 0.0001 by log-rank test). F, Overall survival, defined as the time elapsed between treatment initiation of the second cycle of paclitaxel and death from any cause as a percentage of all animals in each cohort, was not significantly different between the cohorts (by log-rank test).

Somatic alterations in the oncogenic kinase AKT1 have been identified in a broad spectrum of solid tumours. The most common AKT1 alteration replaces Glu17 with Lys (E17K) in the regulatory pleckstrin homology domain1, resulting in constitutive membrane localization and activation of oncogenic signalling. In clinical studies, pan-AKT inhibitors have been found to cause dose-limiting hyperglycaemia2-6, which has motivated the search for mutant-selective inhibitors. We exploited the E17K mutation to design allosteric, lysine-targeted salicylaldehyde inhibitors with selectivity for AKT1 (E17K) over wild-type AKT paralogues, a major challenge given the presence of three conserved lysines near the allosteric site. Crystallographic analysis of the covalent inhibitor complex unexpectedly revealed an adventitious tetrahedral zinc ion that coordinates two proximal cysteines in the kinase activation loop while simultaneously engaging the E17K-imine conjugate. The salicylaldimine complex with AKT1 (E17K), but not that with wild-type AKT1, recruits endogenous Zn2+ in cells, resulting in sustained inhibition. A salicylaldehyde-based inhibitor was efficacious in AKT1 (E17K) tumour xenograft models at doses that did not induce hyperglycaemia. Our study demonstrates the potential to achieve exquisite residence-time-based selectivity for AKT1 (E17K) by targeting the mutant lysine together with Zn2+ chelation by the resulting salicylaldimine adduct.

TRAEs occurring in at least 10% of dose expansion patients or grade 3 in severity treated at the RP2D

Abstract A synthetic lethal interaction between polo-like kinase 4 (PLK4) and elevated TRIM37 was discovered in breast cancer and neuroblastoma (Meitinger et al. 2020; Yeow et al. 2020). High TRIM37 renders cells dependent on PLK4, a kinase that controls centriole duplication. Amplification and copy number gains of the 17q23 amplicon, where TRIM37 resides, are common in breast cancer and neuroblastoma and associated with early relapse and poor prognosis, making PLK4 a promising new synthetic lethal target for these patients. The development candidate ORIC-613 is an orally bioavailable, potent and exquisitely selective small molecule inhibitor of PLK4, which is synthetic lethal in TRIM37 high cells. ORIC-613 is highly selective against the kinome, including against the closely related aurora and PLK families. ORIC-613 ADME/PK profile includes high cell permeability and low potential for drug-drug interactions based on CYP profiling. ORIC-613 blocked PLK4 trans-autophosphorylation of phosphodegrons, leading to stabilization of PLK4, thus directly demonstrating target engagement in cells. PLK4 protein stabilization correlated with cell viability for ORIC-613, providing a quantifiable pharmacodynamic (PD) association with antitumor activity. Cell viability assessment in cancer cell lines revealed that ORIC-613 showed greater potency in TRIM37 high versus TRIM37 low cell lines. Importantly, ORIC-613 induced significantly greater apoptosis in TRIM37 high versus low cancer cell lines as measured by caspase 3/7 assay. We confirmed that ORIC-613 activity is on-target using an engineered cell line system of PLK4 G95L, in which the leucine mutation maintains enzymatic function but blocks compound binding. In cell viability assays, ORIC-613 was potent in the parental cells and lost activity in G95L cells. Analysis of genomic data from tumors indicates that TRIM37 copy number amplification and gain is prevalent across numerous cancers. Oral dosing of ORIC-613 resulted in tumor growth inhibition and regressions in TRIM37 high xenograft breast tumors with no body weight loss. In summary, ORIC-613 is a potential first- and best-in-class development candidate, with exquisite selectivity for PLK4, which demonstrates synthetic lethality in TRIM37 high tumors and has the potential to benefit these patients. Citation Format: Kyle A. Edgar, Siobhan McRee, Gina Andretta, Chelsea Chen, Christophe Colas, Wei Fang, Wayne Kong, Jason Long, Fang Liu, Jared Moore, Aleskandr Pankov, Dan Shore, Joanne Tan, Robert Warne, Livia Ulicna, Rakesh Vekariya, Anneleen Daemen, F Romero, Melissa R. Junttila, Lori S. Friedman. ORIC-613, a potential first- and best-in-class, orally bioavailable, potent and selective PLK4 inhibitor with synthetic lethality in TRIM37 high cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 594.

Study disposition flow diagram of patient disposition. Note: int, intermittent regimen of ORIC-101 administered 5 days on, 2 days off for 21 days out of 28-day cycles; cont, continuous regimen of ORIC-101 administered for 21 days out of 28-day cycles; AE, adverse event; clin, clinical; OST, other solid tumors; PD, progressive disease; radiog, radiographic.

Baseline characteristics and demographics

Amplification and copy number gains of the 17q23 amplicon are common in breast cancer and neuroblastoma and have been associated with early relapse and poor prognosis (Ganesan et al 2012; Takita et al. 2017). A synthetic lethal interaction of PLK4 with 17q23 amplicon-driven overexpression of TRIM37 was discovered in these tumor types (Meitinger et al. 2020; Yeow et al. 2020). High levels of TRIM37 prevented acentrosomal spindle assembly and rendered cells mitotically vulnerable to inhibition of polo-like kinase 4 (PLK4), a serine/threonine protein kinase that controls centriole duplication. We have discovered that exquisitely selective small molecule inhibitors of PLK4, which are highly selective against the kinome including against the closely related aurora kinases and PLK1-3, display this synthetic lethal interaction with TRIM37, while less selective inhibitors do not. PLK4 protein levels are regulated through proteasomal degradation induced by PLK4 trans-autophosphorylation of the phosphodegron. PLK4 inhibition results in blocked trans-autophosphorylation leading to stabilization of PLK4, thus directly demonstrating target engagement in cells. Importantly, PLK4 protein stabilization correlated with cell viability for selective PLK4 inhibitors but not for less selective compounds, providing a quantifiable pharmacodynamic (PD) association with antitumor activity. Cell viability assessment in cancer cell lines revealed that highly selective PLK4 inhibitors showed greater potency in TRIM37 high cancer cell lines as compared to TRIM37 low cell lines. In contrast, less selective compounds, including from the clinical literature, did not display differential potency in TRIM37 high versus low cancer cell lines. Additionally, selective PLK4 inhibition induced significantly greater apoptosis in TRIM37 high versus low cancer cell lines as measured with a caspase 3/7 assay. We confirmed that only selective PLK4 inhibitors are synthetic lethal with TRIM37 amplification using an engineered cell line system of PLK4 G95L, in which the Leucine mutation blocks compound binding but allows the PLK4 enzyme to function. In cell viability assays, selective PLK4 inhibitors were potent in the parental G95 cells and lost activity in L95 cells, unlike less selective inhibitors whose potency did not depend on PLK4. Oral dosing of a selective PLK4 inhibitor resulted in tumor growth inhibition in TRIM37 high xenograft tumors with no body weight loss. In summary, we have discovered that highly selective small molecule inhibitors of PLK4 confirm the potential of the synthetic lethal impact in treating tumors with high levels of TRIM37. Citation Format: Siobhan K. McRee, Chelsea Chen, Christophe Colas, Wie Fang, Wayne Kong, Fang Liu, Jason Long, Jared Moore, Alex Pankov, Dan Shore, Joanne Tan, Robert Warne, Rakesh Vekariya, Amy Young, Anneleen Daemen, Anthony Romero, Melissa R. Junttila, Lori S. Friedman, Kyle A. Edgar. Selective PLK4 inhibition demonstrates synthetic lethality in TRIM37 amplified neuroblastoma and breast cancer models while less selective inhibitors do not. [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 4998.

Amplification and copy number alterations of the 17q23 amplicon are common in breast cancer and neuroblastoma and have been associated with early relapse and poor prognosis. Recent work identified a key vulnerability associated with amplicon-driven overexpression of TRIM37 in these tumor types (Meitinger et al. 2020; Yeow et al. 2020). High levels of TRIM37 prevent acentrosomal spindle assembly and render cells mitotically vulnerable to inhibition of polo-like kinase 4 (PLK4), a serine/threonine protein kinase that controls centrosome duplication. We have discovered potent small molecule inhibitors of PLK4 that are highly selective against the kinome, including against the closely related aurora kinases and PLK1-3. Self-regulation of PLK4 protein levels occurs through proteasomal degradation induced by PLK4 trans-autophosphorylation. ORIC PLK4 inhibitors blocked trans-autophosphorylation leading to stabilization of PLK4, thus directly demonstrating target inhibition in cells. Importantly, PLK4 inhibitor induced PLK4 protein stabilization correlated with cell viability, providing a quantifiable pharmacodynamic (PD) association with antitumor activity. Cell viability assessment across a cancer cell line panel revealed that the highly selective ORIC PLK4 inhibitors showed greater potency in TRIM37 high cancer cell lines as compared to TRIM37 low cell lines. In contrast, less selective compounds, including from the clinical literature, did not display differential potency in TRIM37 high versus low cancer cell lines. Importantly, cell potency in TRIM37 high cancer cells was rescued with knockdown of TRIM37, illustrating that selective PLK4 inhibitors are synthetic lethal with TRIM37 amplification. Oral administration of ORIC PLK4 inhibitors resulted in regressions of TRIM37 high xenograft tumors, with corresponding PD effects and no body weight loss. In summary, we have discovered novel, potent, highly selective small molecule inhibitors of PLK4 that are orally bioavailable and confirmed the potential for this new target in treating tumors with high levels of TRIM37. Citation Format: Kyle A. Edgar, Amy Young, Jared Moore, Xi Chen, Wei Fang, Jae H. Chang, Wayne Kong, Jason E. Long, Aleksandr Pankov, Anneleen Daemen, Daniel G. Shore, Robert Warne, Paul Gibbons, Chudi O. Ndubaku, Melissa R. Junttila, Lori S. Friedman. Discovery of novel, highly selective inhibitors of PLK4 that demonstrate in vivo regressions in TRIM37 high xenografts [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 2633.

The adenosinergic pathway represents an attractive new therapeutic approach in cancer immunotherapy. In this pathway, ecto-5-nucleotidase CD73 has the unique function of regulating production of immunosuppressive adenosine (ADO) through the hydrolysis of AMP. CD73 is overexpressed in many cancers, resulting in elevated levels of ADO that correspond to poor patient prognosis. Therefore, reducing the level of ADO via inhibition of CD73 is a potential strategy for treating cancers. Based on the binding mode of adenosine 5'-(α,β-methylene)diphosphate (AOPCP) with human CD73, we designed a series of novel monophosphonate small-molecule CD73 inhibitors. Among them, OP-5244 (35) proved to be a highly potent and orally bioavailable CD73 inhibitor. In preclinical studies, 35 completely inhibited ADO production in both human cancer cells and CD8+ T cells. Furthermore, 35 lowered the ratio of ADO/AMP significantly and reversed immunosuppression in mouse models, indicating its potential as an in vivo tool compound for further development.

The 59 ecto-nucleotidase CD73 is dynamically expressed in distinct biological contexts as a means to increase the adenosine metabolite, which functions to limit immune activation and prevent excessive inflammation. CD73 activity is required for the final step of adenosine production. In the context of tumors, excessive CD73-mediated adenosine generation impairs anti-tumor immune responses. Here, we show that an orally bioavailable small molecule inhibitor of CD73 can prevent adenosine generation, relieve adenosine-driven immunosuppression within the tumor in vivo and generate anti-tumor efficacy. In vitro analysis confirmed the substantial suppressive effects of adenosine on murine CD8+ T cells, cross-presenting dendritic cells, and macrophages. NECA, a stable analog of adenosine, impaired immature bone-marrow precursor differentiation into CD103+ dendritic cells, a subset which is critical for tumor-derived antigen presentation to naive T cells. Interestingly, NECA also inhibited the ability of macrophages to upregulate the M1 marker, CD80, in both the presence and absence of additional polarizing stimuli. Furthermore, OR-558, a CD73 small molecule inhibitor, could fully inhibit CD73-mediated adenosine production and completely restore T cell activation at sub-nanomolar concentrations. Prior work in CD73 germline knock-out animals has shown that EG7 syngeneic tumor growth is highly dependent on CD73. Building on this knowledge, we next we sought to evaluate CD73 inhibition on AMP to adenosine conversion ex vivo in EG7 syngeneic tumor extracts and indeed observed that OR-558 treatment could significantly impair adenosine production within the tumor milieu. This finding translated to the in vivo tumor setting, where single agent anti-tumor efficacy was observed with continuous OR-558 treatment. Anti-tumor efficacy coincided with significantly decreased intra-tumoral adenosine levels and immune modulation, such as increased intratumoral T cell activation, dendritic cell maturation, and M1 macrophage polarization. Lastly, we determined the bioavailability of orally dosed OR-558 in EG7 tumor-bearing mice and found that significant single agent anti-tumor efficacy was also achievable with once-daily oral dosing of OR-558. Taken together, these data demonstrate that adenosine has pleiotropic immunosuppressive effects and inhibition of CD73-mediated adenosine production in vivo is sufficient to reverse these immune effects and enhance anti-tumor immunity. These results support clinical development of orally bioavailable CD73 small molecule inhibitors. Citation Format: Todd Metzger, Brian Blank, Brenda Chan, Chelsea Chen, Yuping Chen, Xiaohui Du, Frank Duong, Lori Friedman, Melissa Junttila, Hiro Kawai, Wayne Kong, Jared Moore, Johnny Pham, Yosup Rew, Daqing Sun, Jessica Sun, Dena Sutimantanapi, Kejia Wu, Chien-Hung Yeh, Natalie Yuen, Tatiana Zavorotinskaya. An orally bioavailable inhibitor of CD73 reverts intratumoral immunosuppression and promotes anti-tumor responses [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 LB-115.

Abstract ORIC-101 is a novel and selective glucocorticoid receptor (GR) antagonist currently in Ph1 clinical evaluation in solid tumors. In preclinical models, ORIC-101 potently sensitized triple-negative breast cancer (TNBC) cells to chemotherapy by inhibiting GR-mediated resistance through the epithelial-to-mesenchymal transition and anti-apoptosis pathways, both in vitro and in vivo. To inform the clinical development of ORIC-101, we identified pharmacodynamic (PD) biomarkers and established a relationship between those biomarkers, pharmacokinetics (PK), and efficacy in preclinical models. Using genome-wide profiling, we developed a GR activation signature that includes the direct GR transcriptional targets FKBP5 and GILZ, and subsequently validated both genes as ORIC-101 PD biomarkers in a panel of cell lines. We demonstrated that FKBP5 and GILZ are transcriptionally induced by glucocorticoids in a dose-dependent manner, and that the degree of their transcriptional activation is correlated with basal levels of GR in these models. We showed that ORIC-101 robustly inhibits the transcriptional induction of FKBP5 and GILZ and fully reverses GR-mediated chemoresistance in vitro and in vivo. Furthermore, FKBP5 and GILZ are reliable PD biomarkers for ORIC-101 in human-derived peripheral blood mononuclear cells (PBMCs). Importantly, by integrating PK, PD, and efficacy results from numerous preclinical studies, we captured the relationship between ORIC-101 PK, PD biomarker modulation, and chemopotentiation. Altogether, FKBP5 and GILZ mRNA levels are robust PD biomarkers to measure GR pathway engagement and modulation which corresponds with efficacy in response to GR antagonist treatment in preclinical models. These findings will guide the clinical development of ORIC-101 in TNBC. Citation Format: Haiying Zhou, Qiuping Ye, Aleksandr Pankov, Wayne Kong, Shravani Barkund, Lori S. Friedman, Jessica D. Sun, Omar Kabbarah. ORIC-101 robustly inhibits the glucocorticoid pathway and overcomes chemoresistance in triple-negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-03-24.

Abstract Adenosine has emerged as a key immunosuppressive metabolite within the tumor microenvironment (TME). A persistently elevated concentration of adenosine in TME can impair immune control of tumor growth by diminishing cytotoxic T-cell responses and function of natural killer cells while augmenting the suppressive activity of myeloid and regulatory T-cells. The ectonucleotidase, CD73 mediates the final dephosphorylation step in the conversion of extracellular ATP to adenosine. Overexpression of CD73 is observed in many solid tumors and correlates with unfavorable clinical outcome. We aimed to overcome adenosine-driven immunosuppression by developing an orally bioavailable, best-in-class, small molecule inhibitor of CD73. Here, we show superior potency of our selective AMP-competitive CD73 inhibitor in blocking adenosine generation by multiple cell types. CD73 inhibitor activity was assessed by directly measuring the generation of adenosine from AMP by LC-MS/MS. In CD73 expressing cells, potent and complete inhibition of CD73 ectonucleotidase activity was observed. To test the functional consequence of CD73 inhibition, we interrogated the effects of CD73 inhibitors on CD8+ T-cell function upon exposure to AMP. CD73 expressed on T-cells is sufficient to drive adenosine generation from AMP resulting in severely suppressed proliferation, diminished production of inflammatory cytokines and reduced expression of activation markers. Our inhibitors successfully counteracted the effects of AMP and completely rescued all aspects of CD8+ T-cell activation. Interestingly, we found that the concentration of AMP in tumors may vary from micromolar to millimolar levels, underscoring the necessity of AMP-competitive CD73 inhibitors to be efficacious in a high AMP environment. We demonstrated that nanomolar concentrations of our CD73 inhibitors can efficiently rescue T-cell function in the presence of millimolar AMP concentrations. We are currently conducting biophysical studies to better understand this unique property of our inhibitors. We next aimed to identify an adenosine responsive gene signature in cytotoxic T-cells. RNA sequencing analysis of primary anti-CD3/28/2 activated CD8+ T-cells from human peripheral blood mononuclear cells revealed a unique set of genes persistently and similarly altered in response to both adenosine and AMP. Finally, we demonstrated that CD73 inhibitors can completely block gene expression changes of this AMP/adenosine-response signature. Discovery of an AMP/adenosine-response gene signature may help identify patients whose tumors harbor elevated adenosine signaling and would benefit from an orally bioavailable small molecule inhibitor of CD73 to reverse immunosuppression. Citation Format: Tatiana Zavorotinskaya, Brian Blank, Brenda Chan, Chelsea Chen, Yuping Chen, Xiaohui Du, Frank Duong, Lori Friedman, Tom Huang, Melissa R. Junttila, Wayne Kong, Todd C. Metzger, Jared T. Moore, Daqing Sun, Jessica Sun, Dena Sutimantanapi, Natalie Yuen. CD73 inhibition with a novel orally bioavailable small molecule blocks adenosine production and rescues T-cells activation [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 1023.

Abstract Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer and one of the most lethal cancers, with a 5-year survival rate of 8%. Chemotherapy remains the main treatment option for patients with advanced and metastatic tumors. However, intrinsic resistance to chemotherapeutics and lack of effective targeted therapies are major factors contributing to the dismal prognosis. Activation of glucocorticoid receptor (GR) signaling confers resistance to chemotherapy in solid tumors, making GR antagonism an attractive combination treatment strategy to overcome chemotherapeutic resistance. ORIC-101 is a novel selective GR antagonist under clinical evaluation in combination with anticancer therapies. We previously reported that ORIC-101 can sensitize triple-negative breast cancer cells to chemotherapy by reversing multiple GR-modulated pathways. Here, we investigate the effects of ORIC-101 in preclinical models of PDAC. Employing in vitro functional assays and gene expression analysis, ORIC-101 exhibited chemo-potentiation in a panel of PDAC cell lines. Biomarker analysis of transcription activity following ORIC-101 treatment in vitro confirmed pharmacodynamic (PD) modulation of core GR target genes, indicative of suppressed GR signaling. Extending these findings in vivo across several PDAC xenograft models (SW1990, BxPC3, and HPAC) revealed that ORIC-101 blocks GR transcriptional activity induced by dexamethasone in a dose-dependent manner. The PD modulation observed in vivo correlated with ORIC-101 plasma exposure. Consistent with ORIC-101's ability to suppress GR activity, in vivo efficacy studies in combination with paclitaxel significantly inhibited PDAC tumor growth compared to the paclitaxel control group. These results in PDAC preclinical models support the clinical development of ORIC-101 in overcoming GR-driven chemoresistance. A phase 1b study of ORIC-101 in combination with nab-paclitaxel in patients with advanced or metastatic solid tumors is ongoing (NCT03928314). Citation Format: Jessica D. Sun, Haiying Zhou, Wayne Kong, Natalie Yuen, Frank L. Duong, Shravani Barkund, Aleksandr Pankov, Dan McWeeney, Qiuping Ye, Omar Kabbarah, Lori S. Friedman, Anneleen Daemen, Melissa Junttila. ORIC-101 overcomes glucocorticoid receptor-mediated chemoresistance in pancreatic cancer models [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 4123.

Abstract CD73 has emerged as an attractive target for cancer immunotherapy. CD73 (ecto-5-nucleotidase) is a glycosyl phosphatidyl inositol (GPI)-anchored cell surface protein and catalyzes the hydrolysis of AMP into immunosuppressive adenosine and inorganic phosphate. CD73 is widely overexpressed in tumor microenvironments (TME) of many cancers, resulting in elevated levels of extra cellular adenosine (ADO). ADO plays a critical role in tumor progression through immune suppression, chemotherapy resistance, metastasis and angiogenesis. Therefore, reducing the level of adenosine via inhibition of CD73 has become a potential strategy for treating cancers. Here we report our medicinal chemistry efforts in developing orally available small molecule CD73 inhibitors. Based on the binding mode of adenosine 5'-(α,β-methylene)diphosphate (APCP) with CD73, we designed a novel series of monophosphate CD73 inhibitors, which are highly potent and orally bioavailable. In preclinical studies, OP-5244 inhibited ADO production completely in human cancer cells and CD8+ T cells. It also showed dose-dependent inhibitory effects on CD73 activity in various tumors ex vivo. Furthermore, OP-5244 showed PK/PD efficacy through lowering of ADO/AMP ratio and reversal of immunosuppression in vivo. Citation Format: Xiaohui Du, Brian Blank, Brenda Chan, Xi Chen, Yuping Chen, Frank Duong, Lori Friedman, Tom Huang, Melissa R. Junttila, Wayne Kong, Todd Metzger, Jared Moore, Daqing Sun, Jessica Sun, Dena Sutimantanapi, Natalie Yuen, Tatiana Zavorotinskaya. Orally available small molecule CD73 inhibitor reverses immunosuppression through blocking of adenosine production [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 1037.

Abstract Preclinical studies have shown that GR activation leads to decreased response to antimetabolites, taxanes, and platinum agents, while GR inhibition enhances therapeutic efficacy. The novel, selective GR antagonist ORIC-101 is under clinical evaluation in combination with anticancer therapies. In this study we set out to assess which cancer types and chemotherapeutics are responsive to combination with ORIC-101. Specifically, we employed caspase assays, in vitro and in vivo tumor growth inhibition studies, and transcriptional profiling in a panel of preclinical models spanning triple-negative breast, ovarian, non-small cell lung cancers, pancreatic ductal adenocarcinoma, hepatocellular carcinoma, sarcoma, and renal cell carcinoma. We found that ORIC-101 reverses GR-mediated antiapoptosis effects towards diverse chemotherapeutics, including paclitaxel, gemcitabine, and cisplatin, across the seven cancer types. Furthermore, ORIC-101 completely overcomes GR-driven chemoprotection and tumor growth in colony formation assays in vitro and in xenograft studies in vivo. At the molecular level, transcriptional profiling and pathway enrichment analysis showed that ORIC-101 fully reverses GR-activated pathways that are directly involved in drug resistance, such as epithelial-to-mesenchymal transition and antiapoptosis, supporting a pan-cancer role of GR as a mediator of therapy resistance. Altogether, ORIC-101, a selective and potent GR antagonist, overcomes resistance to common chemotherapeutics across multiple cancer models. Clinical evaluation of ORIC-101 in combination with nab-paclitaxel is currently ongoing in advanced solid tumors. Citation Format: Haiying Zhou, Shravani Barkund, Aleksandr Pankov, Ganapati Hegde, Wayne Kong, Padmini Narayanan, Jessica D. Sun, Omar Kabbarah, Lori S. Friedman, Anneleen Daemen. ORIC-101 overcomes resistance to diverse chemotherapeutics across cancer types [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 4121.