First-in-human Study of AZD5153, A Small-molecule Inhibitor of Bromodomain Protein 4, in Patients with Relapsed/Refractory Malignant Solid Tumors and Lymphoma.

Introduction

The bromodomain and extraterminal (BET) family of proteins are epigenetic readers responsible for recruiting transcriptional machinery to active chromatin by binding to acetylated lysine residues on histone tails ( 1 ). Through this mechanism, they regulate various oncogenic programs by modifying transcription of key genes associated with cell-cycle progression and cell survival such as MYC and BCL-2 . The BET family includes four members, with each protein structure containing two tandem bromodomains (BD1, BD2) for binding to acetylated lysine. The most extensively studied BET family protein is BRD4: its overexpression is associated with development and proliferation of tumor types including renal cell, breast, and high-grade serous ovarian cancer (HGSOC; refs. 2, 3 ). In addition, BRD4 is involved in regulating the antitumor activity of natural killer cells ( 4 ), and in replication stress–induced DNA damage response (DDR; ref. 5 ) and homologous recombination–mediated DNA repair (HRR; ref. 6 ).

Targeting the bromodomains of BET proteins through pharmacologic modulation with BET inhibitors (BETi) has emerged as an anticancer approach ( 1 ). A number of pan-BETi and BRD4-specific inhibitors are under investigation as potential therapeutic agents for solid tumors and hematologic malignancies ( 7–13 ) based on preclinical data demonstrating antitumor activity in leukemias and lymphomas ( 14, 15 ), and in breast, ovarian, pancreatic, prostate, and lung cancers ( 3 ). Clinical activity for BETi as single agents has been reported in nuclear protein in testis (NUT) carcinoma and other MYC -driven cancers ( 10, 12 ), as well as in acute myeloid leukemia (AML; ref. 16 ). However, in general, single-agent activity has been limited, and clinical studies have also shown an apparent BETi class effect of exposure-dependent thrombocytopenia ( 17 ) and a limited therapeutic window for some agents ( 8, 11 ).

Nonetheless, preclinical studies have shown that BET inhibition provides additive or synergistic antitumor effects with other anticancer agents, including PARP inhibitors (PARPi; refs. 18–20 ), gemcitabine ( 21 ), DDR-targeted agents ( 5 ), cyclin-dependent kinase inhibitors (CDKi; ref. 22 ), BCL-2 inhibitors ( 23 ), WEE1 inhibitors ( 24 ), Aurora A kinase inhibitors ( 25 ), histone deacetylase inhibitors ( 26 ), hypomethylating agents ( 14 ), and JAK inhibitors ( 27 ). Reflecting these findings, BETi studies have shown clinical activity in triple-negative breast cancer (TNBC) in combination with the PARPi talazoparib ( 7 ), in AML with the BCL-2 inhibitor venetoclax ( 9 ), and in myelofibrosis with the JAK inhibitor ruxolitinib ( 28, 29 ).

Many of the agents investigated clinically are pan-BETi or specific inhibitors of the BD2 domain; a potential approach for increasing potency and antitumor activity is to target both BD1 and BD2 with a single agent ( 3 ). One such bivalent BETi in clinical development is AZD5153, a novel, reversible BRD4 inhibitor that has demonstrated enhanced antitumor activity compared with monovalent BETi in cancer models ( 30 ). AZD5153 was developed for oral administration as a cocrystal; the chemical structure has been reported previously ( 30 ). Preclinical studies have demonstrated in vitro and in vivo activity with AZD5153 alone against HGSOC ( 2 ), prostate cancer ( 31 ), human thyroid carcinoma ( 32 ), AML ( 33 ), and MYC -translocated T-lineage acute lymphoblastic leukemia ( 34 ), and in combination with the PARPi BMN673 in colorectal cancer ( 18 ) and with other PARPi ( 35 ), the CDKi dinaciclib in neuroblastoma ( 36 ), the DDR-targeted agent AZD6738 in ovarian cancer ( 5 ), the WEE1 inhibitor AZD1775 in non–small cell lung cancer ( 24 ), venetoclax in venetoclax-resistant AML ( 37 ), and the BCL-2 inhibitor AZD4320 in diffuse large B-cell lymphoma ( 23 ). Furthermore, preclinical work has suggested that BRD4 inhibition with AZD5153 results in activation of an antitumor immune response and sensitizes ovarian cancer cells to anti-programmed death receptor ligand 1 (PD-L1) therapy ( 38 ). Notably, translational modeling using preclinical study data suggested that although AZD5153 was likely to be associated with reductions in clinical platelet counts, per the BETi class effect of exposure-dependent thrombocytopenia ( 17 ), they would be within the normal range at predicted clinically effective doses ( 39 ).

This first-in-human, phase I, multicenter, dose-escalation study ( NCT03205176 ) was conducted to determine the MTD and recommended phase II dose (RP2D) of AZD5153 as monotherapy and in combination with the PARPi olaparib, as well as the safety, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity in patients with relapsed and/or refractory solid tumors or lymphoma.

Materials and Methods

Study design and treatment

This open-label study was conducted at four sites in the United States and Canada. The primary objective was to determine the safety profile, tolerability, and MTD of AZD5153 monotherapy in patients with malignant solid tumors or lymphomas and of AZD5153 plus olaparib in patients with platinum-resistant (progression within 6 months following last platinum-based regimen) or platinum-refractory [lack of at least a partial response (PR)] HGSOC, refractory TNBC, metastatic castrate-resistant prostate cancer (mCRPC), or pancreatic ductal adenocarcinoma (PDAC). The secondary objectives included single-dose and multiple-dose pharmacokinetic parameters of AZD5153 and its coformer alone and in combination with olaparib, assessment of the effect of AZD5153 alone or with olaparib on QTc interval, and evaluation of preliminary antitumor activity. Exploratory objectives included pharmacodynamic effects (peripheral biomarkers of target engagement) in whole blood, the impact of therapy on biological pathways (e.g., immune microenvironment, DDR) in whole blood and tumor biopsies, and exploration of potential biomarkers of response/resistance. AZD5153 was supplied by AstraZeneca as a dry-filled capsule containing 1, 5, or 20 mg of drug substance. Experimental details for the synthesis of AZD5153 were previously described by Bradbury and colleagues ( 33 ). Commercially available olaparib was supplied by AstraZeneca as 100 and 150 mg tablets.

Dose escalation of AZD5153 proceeded in two parts. First, patients received oral AZD5153 monotherapy once daily or twice daily continuously in 21-day cycles until disease progression or unacceptable toxicity. Dose escalation proceeded from 2 mg once daily (based on preclinical exposure and toxicity data) via a Bayesian continual reassessment method, enrolling 3 to 6 patients evaluable for dose-limiting toxicity (DLT) at each dose level (Supplementary Fig. S1). Once monotherapy dose escalation reached 10 mg twice daily, dose escalation in the second part commenced at the same dose of AZD5153 in combination with oral olaparib 300 mg twice daily in continuous or intermittent (2 weeks on/1 week off) cycles. AZD5153 10 mg twice daily was selected as the starting dose in the combination therapy cohort as its clinical exposure is equivalent to preclinical exposure causing tumor growth inhibition in animal models. Subsequent dose levels were determined on the basis of emerging safety and pharmacokinetic data from ongoing monotherapy and combination therapy cohorts and could include lower AZD5153 doses and intermittent dosing schedules. All decisions on dose escalation/de-escalation were made by a Safety Review Committee (SRC).

Patients

Adult patients were eligible if they were intolerant of, or had tumors refractory to, existing therapies known to provide clinical benefit, and had adequate hematologic, hepatic, and renal function (Supplementary Table S1). Additional eligibility criteria included adequately controlled blood pressure, ejection fraction >50% at baseline, Eastern Cooperative Oncology Group performance status of 0 or 1, predicted life expectancy of ≥ 3 months, ≤5 prior lines of treatment (solid tumors only; no restriction for lymphoma), a minimum washout period following prior PARPi therapy of ≥14 days/≥5 half-lives or until resolution of toxicity, and no prior chemotherapy, radiotherapy, hormonal therapy, immunotherapy, or investigational drugs within 21 days/5 half-lives of enrollment. Patients were excluded if they were receiving strong or moderate inhibitors/inducers of CYP3A4/5, drugs that are sensitive substrates of the transporters P-gp, UGT1A1, BCRP, OATP1B1, OAT3, OCT1, OCT2, MATE1, or MATE2K, or any herbal preparations/medications; or had a mean resting corrected QTc interval > 450 ms on three electrocardiograms, any clinically important abnormalities in cardiac rhythm, or any risk factors for QTc prolongation or arrhythmic events (including receipt of drugs that prolong QT interval or induce torsades de pointes). All patients provided written, informed consent, and the study was performed in accordance with the Declaration of Helsinki and the International Council for Harmonization on Good Clinical Practice and any applicable regulatory requirements.

For the monotherapy cohort, patients required a histologically/cytologically confirmed locally advanced or metastatic solid tumor with ≥1 measurable lesion [by CT per RECIST v1.1 ( 40 )] or lymphoma of any histology [with documented analysis of bone marrow infiltration on biopsy within 3 months of enrolment or able to undergo a new biopsy if previous procedure performed >3 months prior to enrolment, and ≥1 lesion assessable by CT or PET per the revised International Working Group (IWG) criteria ( 41 )] that was refractory to standard therapies or for which no standard therapies existed. For the combination therapy cohort, patients had to have histologically/cytologically confirmed platinum-resistant or platinum-refractory HGSOC, fallopian cancer, or primary peritoneal cancer in the relapsed setting; TNBC refractory to standard therapies or for which no standard therapies existed; refractory mCRPC; or PDAC with progression on standard treatment. They required ≥1 measurable lesion [per RECIST v1.1 ( 40 )] and ≥1 disease site for baseline and on-treatment tumor biopsy. Prior response to olaparib or other PARPi was not required.

Outcomes and assessments

Safety, DLT, and MTD determination

Safety was assessed through 30 days after the end of treatment; adverse events (AE) were graded using the NCI Common Terminology Criteria for Adverse Events version 4.03, and relatedness to study drug was determined by the investigators. Blood samples were collected every cycle for determination of clinical chemistry, hematology, 4-β-hydroxy cholesterol, and coagulation. Triplicate 12-lead safety electrocardiograms were obtained prior to dosing on day 1 of every cycle, at the end-of-treatment visit, and at progression-free follow-up visits. DLTs were defined as toxicities not clearly related to progressive disease or an extraneous cause that occurred during cycle 1, and included grade ≥4 neutropenia for >7 days; febrile neutropenia; grade 3/4 thrombocytopenia with clinically significant bleeding (e.g., drop in hemoglobin >2 points due to bleeding, or requiring red blood cell transfusion); grade ≥4 anemia; grade ≥3 nonhematologic toxicity (excluding alopecia); any clinically significant/unacceptable toxicity that worsened from baseline, that did not respond to supportive care, that resulted in dosing schedule disruption for >14 days, or that was judged to be a DLT by the investigator in collaboration with the medical monitor, or the SRC; and inability to receive 75% of the planned dose in cycle 1 due to treatment-related toxicity. The MTD for the monotherapy and combination therapy cohorts was determined as the highest respective AZD5153 doses at which the predicted probability of a DLT was ≤25% per the Bayesian adaptive model.

Pharmacokinetics

Blood and urine samples were collected on days 1 and 14 for characterizing single-dose and multiple-dose pharmacokinetics of AZD5153, its coformer, and olaparib using a validated bioanalytical method. Specifically, plasma (K 2 EDTA) samples (25 μL) were analyzed for AZD5153 with a fully validated method (in accordance with the FDA, Bioanalytical Method Validation; Guidance for Industry, 2018) with a calibration range of 0.0144 to 14.4 nmol/L AZD5153. Concentrations were calculated with reference to a calibration series, constructed by adding known amounts of each compound to control plasma and processing these standards in parallel with samples from the study. Following addition of stable label internal standard AZD5153-d4 to calibration, quality control and study samples, all samples were subjected to supported liquid extraction. Extracts were then assayed by reversed-phase high-performance liquid chromatography with Turbo Ion Spray MS-MS with mass transitions of m/z 480.2→395.2 and 484.2→399.2 monitored for AZD5153 and the internal standard, respectively. All samples were assayed within the known stability period for AZD5153 in plasma.

Pharmacodynamics

For the analysis of peripheral biomarkers of target engagement, blood samples for whole blood RNA analysis were collected at screening, and then on days 1 and 14 of cycle 1 predose and at 2, 3, 6, and 24 hours postdose. Blood samples (2×2.5 mL) were collected in Paxgene tubes (BD Biosciences), which contain a proprietary reagent for stabilization of intracellular RNA immediately upon collection, at screening, and then on days 1 and 14 of cycle 1 predose and at 2, 3, 6, and 24 hours postdose. The blood samples were not fractionated as cells were lysed as soon as blood was collected into the tubes. Samples were frozen after collection at −20°C for 24 hours and −70°C thereafter. Primary samples were shipped frozen on dry ice to Covance CLS (now part of LabCorp) on the day of collection and backup samples were similarly shipped via the next available shipment.

The samples were analyzed by quantitative PCR to assess modulation of BRD4 target genes, including CCR2 , CD274 , HEXIM1 , and HIST2H2BF , following AZD5153 dosing. Pharmacokinetic plasma samples collected predose and 2 and 3 hours postdose on day 1, cycle 1 were repurposed for longitudinal analysis of cytokine levels using a 53-biomarker Human InflammationMAP v.1.1 Luminex panel and the IL6 single-molecule array assay, with data visualization using Spotfire analysis. Longitudinal analyses were done with normalization to the average value of each cytokine concentration or to the 90th percentile plasma values in healthy volunteers, and by comparing with predose levels. Analyses were grouped by cohorts receiving similar AZD5153 doses.

Antitumor activity

Tumor assessment (solid tumors: CT scan or MRI of the chest and abdomen/pelvis; lymphoma: PET scan) was performed at baseline (within 28 days prior to first dose of study drug), and then every 6 weeks for 1 year and thereafter every 12 weeks until disease progression. For patients with lymphoma, a bone marrow biopsy within 3 months of enrollment or at screening was required; bone marrow aspiration and biopsy were performed every 6 weeks if required to confirm a complete response. Response was assessed per RECIST v1.1 ( 40 ) for patients with solid tumors and per revised IWG criteria ( 41 ) for patients with lymphoma.

Statistical analysis

Primary endpoints were analyzed using summary statistics. The total number of patients enrolled reflected the number of patients per cohort in cohorts required in the dose-escalation portions of the study, based on emerging safety and pharmacokinetic data. The DLT-evaluable population included patients who completed all safety evaluations in cycle 1 and received ≥75% of planned doses of AZD5153 alone or with ≥75% of planned doses of olaparib, or who experienced a DLT during cycle 1. The safety population included all patients who received ≥1 dose of AZD5153; the pharmacokinetic population included patients in the safety population who provided ≥1 evaluable pharmacokinetic sample; the response-evaluable population included patients in the safety population who had a baseline tumor assessment.

Data availability statement

Data underlying the findings described in this article may be obtained in accordance with AstraZeneca's data sharing policy described at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure . Data for studies directly listed on Vivli can be requested through Vivli at www.vivli.org . Data for studies not listed on Vivli could be requested through Vivli at https://vivli.org/members/enquiries-about-studies-not-listed-on-the-vivli-platform/ . AstraZeneca's Vivli member page is also available outlining further details: https://vivli.org/ourmember/astrazeneca/ .

Results

Patient characteristics and disposition

Between June 30, 2017 and April 19, 2021, 49 patients were enrolled, 34 to monotherapy and 15 to combination therapy. In the monotherapy cohort, patients were enrolled to eight AZD5153 dose levels between 2 mg once daily and 40 mg once daily. In the combination therapy cohort, patients were enrolled to three AZD5153 dose levels (10 mg twice daily, 5 mg twice daily, 10 mg once daily) in combination with olaparib 300 mg twice daily (Supplementary Fig. S1).

Patient demographics and baseline characteristics are summarized in Table 1 , overall and by cohort (representativeness of study participants is described in Supplementary Table S2). The majority of patients (79.6%) were female, and 59.2% were aged ≥65 years. The most common cancers in the monotherapy cohort were uterus/endometrial (26.5%), lung (17.6%), ovarian (14.7%), and colon (11.8%) cancer; in the combination therapy cohort all patients had ovarian (60.0%) or pancreatic (40.0%) cancer. Most patients (93.9%) had distant metastases at enrollment. A majority (65.3%) had received ≥3 prior systemic therapies.

At data cutoff (December 23, 2021), all 49 patients had discontinued due to disease progression ( n = 36), physician decision ( n = 5), patient withdrawal ( n = 4), or AEs ( n = 3), with 1 patient lost to follow-up.

Dose escalation and DLTs

In the monotherapy cohort, 32 of 34 patients were DLT-evaluable; 2 patients were excluded due to receiving <75% of the expected dose of AZD5153 in cycle 1. No DLTs were reported in 9 evaluable patients dosed at 2, 5, and 10 mg once daily, or in 4 evaluable patients in the 10 mg twice daily cohort. At the next dose level, 20 mg twice daily, 2 patients had DLTs: a treatment-related AE (TRAE) of grade 4 thrombocytopenia that resolved following dose reduction to 10 mg; and a TRAE of grade 3 diarrhea that resolved following dose interruption and reduction. Dosing was de-escalated to 15 mg twice daily and 30 mg once daily, and no DLTs were reported in 6 and 3 evaluable patients, respectively, or in 4 evaluable patients dosed at the next dose level, 40 mg once daily. However, based on TRAEs requiring discontinuation, interruption, or dose reduction at this dose level, and on the totality of safety, pharmacokinetic, and pharmacodynamic data, the RP2D was determined to be 30 mg once daily or 15 mg twice daily for AZD5153 monotherapy.

In the combination therapy cohort, 13 patients were DLT-evaluable; 2 patients were excluded because of receiving < 75% of the expected dose of AZD5153 in cycle 1. All 3 patients dosed at AZD5153 10 mg twice daily reported DLTs of grade 3 ( n = 1) or grade 4 ( n = 2) thrombocytopenia. The grade 3 thrombocytopenia resolved following dose interruption, while one grade 4 event was a TRAE that resolved following dose interruption (and subsequent reduction to 5 mg) and the other was a treatment-emergent AE (TEAE) that had not resolved at data cutoff following dose interruption. The AZD5153 dose was subsequently de-escalated to 5 mg twice daily. No DLTs were seen in 4 evaluable patients; however, due to early discontinuation for poor tolerability in 2 patients, a dose of 10 mg once daily on an intermittent schedule (days 1–14 of 21-day cycles) was explored. Two DLTs were reported in 6 evaluable patients at this dose level, as they did not receive >75% of olaparib doses during cycle 1 due to decreased platelet count that led to interruption of olaparib. However, neither patient had any bleeding or other complications, and while no formal MTD was declared, the SRC selected this dose as the RP2D for combination treatment.

Treatment exposure and safety

In the AZD5153 monotherapy cohort, median treatment duration was 1.38 months (range, 0.3–18.0); 4 (11.8%) patients remained on treatment for ≥6.0 months. Mean relative dose intensity of AZD5153 was 88.43%. Overall, 32 of 34 (94.1%) patients reported ≥1 TEAE, most commonly fatigue (38.2%), thrombocytopenia, diarrhea (each 32.4%), nausea, and decreased appetite (each 26.5%; Table 2 ). Grade ≥3 TEAEs were reported by 19 (55.9%) patients, including thrombocytopenia (14.7%), anemia (8.8%), and fatigue (5.9%). The most common TRAEs were fatigue (35.3%), diarrhea, and thrombocytopenia (each 29.4%).

Serious TEAEs were reported in 7 patients receiving AZD5153 monotherapy, none of which were TRAEs ( Table 2 ). The only TEAE leading to death was sepsis that occurred 22 days after discontinuing AZD5153 and starting carboplatin therapy. Three (8.8%) patients discontinued AZD5153 due to AEs: 2 in the 20 mg twice daily cohort due to TEAEs of grade 1 autoantibody test (investigator decision to discontinue) and grade 3 hip fracture, and 1 in the 40 mg once daily cohort due to a TRAE of grade 2 fatigue; 22 (64.7%) patients had dose interruptions due to TEAEs, and 5 (14.7%) had dose reductions due to TEAEs of thrombocytopenia ( n = 4) and diarrhea ( n = 1).

In the combination therapy cohort, median treatment duration was 1.41 months (range, 0.1–8.7); 1 (6.7%) patient remained on treatment for ≥ 6.0 months. Mean relative dose intensity of AZD5153 was 81.78% and of olaparib was 77.39%. All 15 patients reported ≥1 TEAE, most commonly nausea (66.7%), fatigue (53.3%), dysgeusia, vomiting (each 40.0%), thrombocytopenia, and platelet count decreased (each 33.3%; Table 2 ). Grade ≥3 TEAEs were reported by 10 (66.7%) patients, including thrombocytopenia (26.7%), hyponatremia (20.0%), and fatigue and nausea (each 13.3%). The most common TRAEs were nausea (60.0%), dysgeusia (40.0%), and fatigue, vomiting, and platelet count decreased (each 33.3%).

Serious TEAEs were reported in 3 (20.0%) patients receiving combination therapy, including one TRAE of nausea ( Table 2 ). No patients died or discontinued AZD5153 or olaparib due to AEs; 12 (80%) patients had dose interruptions due to TEAEs. One (6.7%) patient had dose reductions of AZD5153 and olaparib due to a TEAE of hyponatremia and a TRAE of thrombocytopenia, and 1 (6.7%) had a dose reduction of AZD5153 due to a TRAE of fatigue. Three (6.1%) patients reported other significant AEs: syncope ( n = 1); sinus tachycardia and QT prolonged ( n = 1); and tachycardia ( n = 1). All 3 patients received AZD5153 monotherapy.

To characterize the kinetics of thrombocytopenia with AZD5153 alone and in combination with olaparib, evaluable platelet counts from blood samples obtained during treatment were analyzed to identify the nadir, percentage change from predose sample on day 1, cycle 1, and time to nadir and recovery. Figure 1A shows mean changes in platelet count over time during treatment; Fig. 1B plots the relationship of AZD5153 exposure to percentage change from baseline to nadir in platelet count. Baseline platelet count was similar across dose levels and among patient subgroups defined by maximum grade of thrombocytopenia on treatment (Supplementary Fig. S2). A dose-dependent impact on platelet count was seen with AZD5153 monotherapy, and to a greater extent in combination with olaparib. Median time to platelet count nadir was 3.4 weeks (5th to 95th percentile range: 2.0–8.9); median time to recovery (platelet count >150 × 10 9 /L) was 2.1 weeks (5th to 95th percentile range 1.0–6.4; Supplementary Fig. S3).

Pharmacokinetics

The pharmacokinetics of AZD5153 and its coformer were determined after single and multiple dosing alone or with olaparib ( Fig. 2 ; Table 3 ). After single-dose monotherapy, AZD5153 was rapidly absorbed, with a median T max of 0.5 to 3 hours. Following T max , AZD5153 levels declined with a mean terminal elimination half-life (t½λz) of 1.8 to 5.4 hours. Following multiple-dose monotherapy, AZD5153 geometric mean exposure generally increased with dose. Consistent with the short half-life, there was no evidence of accumulation on once daily or twice daily dosing schedules. Overall variability in AZD5153 pharmacokinetics was high; %CV for C max and AUCs was 26% to 95% across cohorts.

AZD5153 pharmacokinetics in combination with olaparib was assessed in a limited number of patients and was consistent with pharmacokinetics observed in monotherapy. With both monotherapy and combination therapy, renal excretion of unchanged AZD5153 was very low, with geometric mean cumulative recoveries of <2% of the dose, across the dose ranges tested.

Olaparib pharmacokinetics was evaluated in a limited number of patients in the combination cohort after multiple doses of AZD5153. Median T max was 0.5 to 1.0 hours; geometric mean C max was 4.9 to 11.2 μg/mL. Olaparib pharmacokinetics did not appear to be affected by coadministration with AZD5153. Plasma concentration–time curves are shown in Supplementary Fig. S4.

The AZD5153 coformer was absorbed rapidly in plasma, independent of dose after single or multiple administration of AZD5153 monotherapy, with a median T max of 0.5 to 1.0 hours. Levels then declined rapidly with an estimated mean t½λz of 1.0 to 4.7 hours. There was no consistent evidence of accumulation on once daily or twice daily dosing schedules. Coformer pharmacokinetics were available for only 1 to 3 patients receiving combination treatment with olaparib, all of whom received AZD5153 10 mg twice daily; single- and multiple-dose profiles appeared generally similar to those of monotherapy.

Pharmacodynamics and pharmacokinetic/pharmacodynamic modeling

Target engagement was evaluated in the monotherapy and combination therapy cohorts. Dose-dependent modulation of BRD4-related biomarkers was observed in peripheral blood samples, offering preliminary evidence of target engagement in this anatomical compartment. Quantitative PCR analysis of samples collected on days 1 and 14 following AZD5153 dosing demonstrated concentration-dependent modulation of BRD4 target genes, specifically downregulation of CCR2 and CD274 , and upregulation of HEXIM1 and HIST2H2BF ( Fig. 3 ). The maximum effect was observed 2 to 3 hours after dosing, with a return to baseline at 24 hours and no signs of accumulation between days 1 and 14 (Supplementary Fig. S5).

Analysis of cytokine levels and their regulators in plasma samples from 32 consenting patients in the monotherapy cohorts through 0 to 3 hours postdose showed a decrease in monocyte chemoattractant protein-1 (MCP-1) and a modest increase in matrix metalloproteinase-9 (MMP-9) in the higher-dose (20–40 mg) AZD5153 cohorts, when data were normalized to average patient values. Consistently, a decrease in MCP-1 was seen on the analysis of all cohorts (2–40 mg) normalized to the 90% highest values of biomarkers from healthy volunteers. Plasma levels of cytokines and their regulators relative to predose values across all cohorts (2–40 mg) showed a decrease in MCP-1, MMP-3, and macrophage inflammatory protein-1 beta (MIP-1β) on treatment (Supplementary Fig. S6A); analyses restricted to the higher-dose (20–40 mg) cohorts demonstrated these changes with similar or greater confidence ( r 2 ; Supplementary Fig. S6B). The decreases in plasma levels of MCP-1, MMP-3, and MIP-1β were also seen with greater confidence in analyses restricted to 0 to 2 hours postdose (Supplementary Fig. S6C).

Clinical exposures to AZD5153 were evaluated in the context of preclinical doses at which pharmacodynamic modulation was demonstrated, specifically the HEXIM1 threshold (defined as the lowest concentration at which a change from baseline can be detected) and the IC 50 of HRR (derived from an in vitro reporter assay system). Clinical exposures at AZD5153 doses of 10 to 15 mg corresponded to exposures in mice using doses of 0.038 and 0.075 mg/kg, at which both the HEXIM1 threshold and the HRR IC 50 were exceeded (Supplementary Fig. S7). Clinical concentrations of AZD5153 following a 10 mg dose remained above the HEXIM1 threshold for 5.19 hours (4.16–12.93) and above the HRR IC 50 for 11.19 hours (7.97–23.48), compared with 3.7 hours and 11 hours, respectively, in preclinical studies in mice at 0.038 mg/kg (Supplementary Table S3).

Antitumor activity

No objective responses were seen in 33 evaluable patients in the AZD5153 monotherapy cohort. In the combination therapy cohort, 1 patient with metastatic BRCA-negative PDAC (6.7%) who received AZD5153 10 mg once daily on the intermittent schedule had a PR at 4.1 months from the first dose of treatment; the duration of response was 4.2 months. Best percentage change in target lesion size in response-evaluable patients (Supplementary Fig. S8) included a reduction of >10% in 2 patients (6.1%) in the monotherapy cohort and in 3 patients (20%) in the combination therapy cohort. Overall, disease control at 6 weeks was seen in 16 (48.5%) and 4 (26.7%) patients in the AZD5153 monotherapy and combination therapy cohorts, respectively; duration of therapy by response to treatment is shown in Supplementary Fig. S9.

Discussion

This first-in-human study of the novel, bivalent, reversible BRD4 inhibitor AZD5153 for relapsed and/or refractory solid tumors or lymphoma identified RP2Ds of 30 mg once daily or 15 mg twice daily for monotherapy and 10 mg once daily on an intermittent dosing schedule (2 weeks on, 1 week off) in combination with olaparib. Although the MTD was not reached during monotherapy dose escalation, the RP2D was determined on the basis of the totality of safety, pharmacokinetic, and pharmacodynamic data. The tolerability profile was very similar using the 15 mg twice daily and 30 mg once daily dosing schedules; pharmacokinetic and pharmacodynamic data suggested no obvious advantage for twice daily versus once daily dosing. Thus, from a practical perspective, 30 mg once daily was selected as the monotherapy RP2D to support patient dosing compliance. In the first combination therapy cohort (AZD5153 10 mg twice daily plus olaparib), all 3 patients experienced DLTs of thrombocytopenia. Therefore, the next combination cohort used AZD5153 5 mg twice daily, which resulted in no DLTs, although decreased platelets were observed in some patients. The SRC concluded that AZD5153 5 mg twice daily plus olaparib was unlikely to be tolerated over multiple cycles, due to the risk of thrombocytopenia, and patients were enrolled into the third combination therapy cohort using an intermittent schedule [AZD5153 10 mg once daily (2 weeks on, 1 week off) plus olaparib]. While 2 of 7 patients experienced DLTs (platelet count decreased) in this cohort, the SRC deemed it tolerated because neither patient had any bleeding or other complications and concluded that further exploration of this combination could be considered in future studies, with appropriate medical management. In terms of AZD5153 target engagement, pharmacodynamic analyses demonstrated the anticipated inhibition of BRD4. Preliminary antitumor activity was seen, including a PR in a patient with PDAC.

The safety profile of AZD5153 monotherapy generally reflected previously reported safety profiles for BETi in hematologic malignancies and solid tumors, with common hematologic TEAEs including thrombocytopenia and anemia, and non-hematologic TEAEs including fatigue, diarrhea, and nausea ( 9, 17, 42 ). Thrombocytopenia was the most commonly reported grade ≥3 TEAE and DLT, notably at higher doses on a twice daily schedule, which is consistent with clinical data on other BETi and the apparent class effect ( 8, 13, 17 ). Nevertheless, these events were manageable on a continuous dosing schedule. Furthermore, analysis of platelet count kinetics showed a time to nadir of approximately 3 weeks and a recovery time of 2 weeks to >150 × 10 9 /L, similar to the exposure-proportional decreases and rapid recovery seen with another BETi, ODM-207 ( 8 ). Other early-phase trials of the BETi RO6870810 have reported DLTs including liver toxicities, congestive heart failure, angina pectoris, hypertension, and febrile pneumonia in relapsed/refractory AML/myelodysplastic syndromes ( 16 ), multiple myeloma ( 43 ), and diffuse large B-cell lymphoma in combination with venetoclax and rituximab ( 44 ); however, such toxicities were seen only rarely in the current study. There were no notable trends in electrocardiograms over time in any treatment cohort, although 3 patients had cardiac events (syncope, sinus tachycardia/QT prolonged, and tachycardia; all in the monotherapy group).

AZD5153 exposure generally increased with increasing doses across the dose range of 2 to 40 mg, with minimal accumulation following repeated dosing, which informed the selection of 30 mg once daily or 15 mg twice daily as the monotherapy RP2D. No change in AZD5153 pharmacokinetics was observed in combination with olaparib, and similarly olaparib pharmacokinetics were consistent with those for olaparib monotherapy ( 45 ). Strong evidence of peripheral target engagement was observed at AZD5153 doses ≥10 mg, including dose-dependent modulation of the BRD4 target genes CCR2 , CD274 , HEXIM1 , and HIST2H2BF , although effects were not evaluated in tumor tissue due to lack of biopsies collected. However, preclinical studies have explored the relationship between AZD5153 pharmacokinetics and target engagement in blood and tumors in different xenograft models, establishing a good correlation between peripheral and tumor effects ( 30 ). HEXIM1 upregulation was much greater than reported with other BETi such as ABBV-075 and BI894999 ( 9, 11, 46, 47 ); this is associated with BRD4 inhibition causing replication stress through the release of P-TEFb from its inhibitor, HEXIM1 ( 48 ). The pharmacokinetic/pharmacodynamic relationship in the context of this key biomarker highlighted the need for an AZD5153 dose of ≥10 mg to achieve concentrations required for HEXIM1 upregulation, informing the use of 10 mg once daily on an intermittent schedule as a de-escalation dose in the combination cohorts. Furthermore, as previously seen in NUT carcinomas ( 10 ), reduction of MCP-1 can be used as a pharmacodynamic biomarker, as can reductions in MMP3 and MIP-1β, other chemokines involved in macrophage recruitment at sites of inflammation.

The limited antitumor activity seen despite HEXIM1 upregulation suggests that, while this transcriptional biomarker may be useful for determining target engagement, it might not be well suited to evaluating antitumor effects of AZD5153 in combination therapy approaches. However, the role of BRD4 inhibition and HEXIM1 upregulation in inducing a homologous recombination–deficient phenotype supports the rational combination of BETi with PARPi in various tumor types, including ovarian cancer ( 35, 49 ), TNBC ( 7 ), and PDAC ( 50 ). Indeed, the only objective response in the current study was a PR in a patient with metastatic relapsed/refractory PDAC receiving AZD5153 10 mg once daily on the intermittent schedule plus olaparib, with no objective responses observed with AZD5153 monotherapy. Modest monotherapy responses have been observed with other BETi in hematologic malignancies or rare tumors such as NUT-midline carcinomas ( 17 ); however, both preclinical data and clinical experience suggest that BET inhibition will be optimal in combination with other agents ( 7, 17 ).

Supplementary Material

Supplementary Tables and Figures

Acknowledgments

This study was sponsored by AstraZeneca.

Medical writing support for the development of this article, under the direction of the authors, was provided by Stephen Hill, PhD, of Ashfield MedComms (Macclesfield, UK), an Inizio company, and was funded by AstraZeneca. We thank Helena Edlund, AstraZeneca R&D, Gothenburg, Sweden, Gregory O'Connor, Oncology R&D, AstraZeneca, Waltham, MA, US, and Michael Davies, Oncology R&D, Cambridge, UK for their valuable contributions to the study.

The publication costs of this article were defrayed in part by the payment of publication fees. Therefore, and solely to indicate this fact, this article is hereby marked “advertisement” in accordance with 18 USC section 1734.

Footnotes

Note: Supplementary data for this article are available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/).

Authors' Disclosures

E.P. Hamilton reports grants and other support from AstraZeneca during the conduct of the study; grants from Abbvie, Acerta Pharma, Accutar Biotechnology, ADC Therapeutics, AKESOBIO Australia, Amgen, Aravive, ArQule, Artios, Arvinas, AtlasMedx, BeiGene, Black Diamond, Bliss BioPharmaceuticals, Boehringer Ingelheim, Cascadian Therapeutics, Clovis, Compugen, Context Therapeutics, Cullinan, Curis, CytomX, Dana-Farber Cancer Institute, Dantari, Deciphera, Duality Biologics, eFFECTOR Therapeutics, Elucida Oncology, EMD Serono, FujiFilm, G1 Therapeutics, H3 Biomedicine, Harpoon, Hutchinson MediPharma, Immunogen, Immunomedics, Incyte, Infinity Pharmaceuticals, InvestisBio, Jacobio, Karyopharm, K-Group Beta, Kind Pharmaceuticals, Leap Therapeutics, Lycera, Mabspace Biosciences, Macrogenics, MedImmune, Merus, Millennium, Molecular Templates, Nucana, OncoMed, Onconova Therapeutics, Oncothyreon, ORIC Pharmaceuticals, Orinove, PharmaMar, Pieris Pharmaceuticals, Pionyr Immunotherapeutics, Plexxikon, Prelude Therapeutics, Profound Bio, Radius Health, Regeneron, Repertoire Immune Medicine, Rgenix, Sermonix Pharmaceuticals, Shattuck Labs, StemCentRx, Sutro, Syndax, Syros, Taiho, TapImmune, Tesaro, Tolmar, Torque Therapeutics, Treadwell Therapeutics, Verastem, Zenith Epigenetics, Zymeworks; grants and other support from AstraZeneca, Daiichi Sankyo, Ellipses Pharma, Lilly, Loxo Oncology, Mersana, Novartis, Olema, Orum Therapeutics, Pfizer, Relay Therapeutics, Roche/Genentech, SeaGen; other support from Greenwich LifeSciences, iTeos, Janssen, Stemline Therapeutics, Theratechnologies, Tubulis, and Verascity Science outside the submitted work. J.S. Wang reports other support from AstraZeneca and AstraZeneca outside the submitted work. A.M. Oza reports grants from AstraZeneca during the conduct of the study; personal fees from Morphosys outside the submitted work; and Steering Committee and PI on trials with AstraZeneca, GSK, Clovis. M.R. Patel reports other support from AstraZeneca during the conduct of the study. S.V. Ulahannan reports grants from AbbVie, Inc, Adlai Nortye, ArQule, Inc, AstraZeneca, Atreca, Boehringer Ingelheim, Bristol Myers Squibb, Celgene Corporation, Ciclomed LLC, Erasca, Evelo Biosciences, Inc, Exelexis, G1 Therapeutics, Inc, GlaxoSmithKline, IGM Biosciences, Incyte, Isofol, Klus Pharma, Inc, Macrogenics, Merck Co. Inc, Mersana Therapeutics, OncoMed Pharmaceuticals, Inc, Pfizer, Regeneron, Inc, Revolution Medicines, Inc, Synermore Biologics Co, Takeda, Tarveda Therapeutics, Tesaro, Tempest, Vigeo Therapeutics, Inc; other support from Eisai, AstraZeneca, and IgM Biosciences during the conduct of the study; grants from AbbVie, Inc, Adlai Nortye, ArQule, Inc, AstraZeneca, Atreca, Boehringer Ingelheim, Bristol Myers Squibb, Celgene Corporation, Ciclomed LLC, Erasca, Evelo Biosciences, Inc, Exelexis, G1 Therapeutics, Inc, GlaxoSmithKline, IGM Biosciences, Incyte, Isofol, Klus Pharma, Inc, Macrogenics, Merck Co. Inc, Mersana Therapeutics, OncoMed Pharmaceuticals, Inc, Pfizer, Regeneron, Inc, Revolution Medicines, Inc, Synermore Biologics Co, Takeda, Tarveda Therapeutics, Tesaro, Tempest, Vigeo Therapeutics, Inc; other support from Eisai, AstraZeneca, and IgM Biosciences outside the submitted work. T. Bauer reports grants from AstraZeneca during the conduct of the study; personal fees from Pfizer, Lilly, Bristol Myers Squibb, AstraZeneca, GuardantHealth, Foundation Medicine, and Bayer outside the submitted work. J. Zeron-Medina reports personal fees from AstraZeneca during the conduct of the study; personal fees from AstraZeneca outside the submitted work. G. Fabbri reports other support from AstraZeneca during the conduct of the study; other support from AstraZeneca outside the submitted work; and G. Fabbri is employed by AstraZeneca and holds shares. P. Marco-Casanova reports other support from AstraZeneca outside the submitted work. G. Moorthy reports other support from AstraZeneca during the conduct of the study; other support from AstraZeneca outside the submitted work. M.M. Hattersley reports personal fees from AstraZeneca outside the submitted work; in addition, M.M. Hattersley has a patent for WO2021074769A1 issued. G.M. Littlewood reports personal fees from AstraZeneca outside the submitted work. P. Mitchell reports other support from AstraZeneca during the conduct of the study. G.P. Pouliot reports personal fees from AstraZeneca during the conduct of the study; personal fees from AstraZeneca outside the submitted work; in addition, G.P. Pouliot has a patent for dose schedule of AZD5153/olaparib combination issued. K.N. Moore reports personal fees from Aadi, AstraZeneca, Alkemeres, Aravive, Blueprint Pharma, Caris, Duality, Eisai, GOG Partners, Immunogen, Mereo, Mersana, Myriad, Novartis, OncXerna, OncoNova, Panavance, VBL Therapeutics, and Zentalis; grants and personal fees from Clovis, GSK, Genentech/Roche, Merck, Lilly, Verastem during the conduct of the study. No disclosures were reported by the other authors.

Authors' Contributions

E.P. Hamilton: Resources, data curation, supervision, investigation, writing–review and editing. J.S. Wang: Investigation, writing–review and editing. A.M. Oza: Resources, investigation, writing–review and editing. M.R. Patel: Data curation, formal analysis, supervision, investigation, writing–review and editing. S.V. Ulahannan: Data curation, formal analysis, investigation, writing–review and editing. T. Bauer: Resources, investigation, writing–review and editing. J.L. Karlix: Conceptualization, data curation, investigation, methodology, writing–review and editing. J. Zeron-Medina: Conceptualization, investigation, writing–review and editing. G. Fabbri: Data curation, formal analysis, investigation, writing–original draft, writing–review and editing. P. Marco-Casanova: Data curation, formal analysis, supervision, methodology, writing–review and editing. G. Moorthy: Conceptualization, data curation, formal analysis, visualization, methodology, writing–original draft, writing–review and editing. M.M. Hattersley: Conceptualization, data curation, formal analysis, investigation, writing–review and editing. G.M. Littlewood: Data curation, supervision, project administration, writing–review and editing. P. Mitchell: Formal analysis, writing–review and editing. J. Saeh: Data curation, formal analysis, investigation, writing–review and editing. G.P. Pouliot: Conceptualization, data curation, formal analysis, supervision, investigation, writing–review and editing. K.N. Moore: Supervision, investigation, writing–review and editing.

References

1. Kulikowski E, Rakai BD, Wong NCW. Inhibitors of bromodomain and extra-terminal proteins for treating multiple human diseases. Med Res Rev 2021;41:223–45.

2. Rhyasen GW, Yao Y, Zhang J, Dulak A, Castriotta L, Jacques K, et al. BRD4 amplification facilitates an oncogenic gene expression program in high-grade serous ovarian cancer and confers sensitivity to BET inhibitors. PLoS One 2018;13:e0200826.

3. Shorstova T, Foulkes WD, Witcher M. Achieving clinical success with BET inhibitors as anti-cancer agents. Br J Cancer 2021;124:1478–90.

4. Cribbs AP, Filippakopoulos P, Philpott M, Wells G, Penn H, Oerum H, et al. Dissecting the role of BET bromodomain proteins BRD2 and BRD4 in human NK cell function. Front Immunol 2021;12:626255.

5. Zhang J, Dulak AM, Hattersley MM, Willis BS, Nikkila J, Wang A, et al. BRD4 facilitates replication stress-induced DNA damage response. Oncogene 2018;37:3763–77.

6. Mio C, Gerratana L, Bolis M, Caponnetto F, Zanello A, Barbina M, et al. BET proteins regulate homologous recombination-mediated DNA repair: BRCAness and implications for cancer therapy. Int J Cancer 2019;144:755–66.

7. Aftimos P, Oliveira M, Punie K, Boni V, Hamilton E, Gucalp A, et al. A phase 1b/2 study of the BET inhibitor ZEN003694 in combination with talazoparib for treatment of patients with TNBC without gBRCA1/2 mutations [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8–11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS11-10.

8. Ameratunga M, Brana I, Bono P, Postel-Vinay S, Plummer R, Aspegren J, et al. First-in-human phase 1 open label study of the BET inhibitor ODM-207 in patients with selected solid tumours. Br J Cancer 2020;123:1730–6.

9. Borthakur G, Odenike O, Aldoss I, Rizzieri DA, Prebet T, Chen C, et al. A phase 1 study of the pan-bromodomain and extraterminal inhibitor mivebresib (ABBV-075) alone or in combination with venetoclax in patients with relapsed/refractory acute myeloid leukemia. Cancer 2021;127:2943–53.

10. Piha-Paul SA, Hann CL, French CA, Cousin S, Brana I, Cassier PA, et al. Phase 1 study of molibresib (GSK525762), a bromodomain and extra-terminal domain protein inhibitor, in NUT carcinoma and other solid tumors. JNCI Cancer Spectr 2020;4:pkz093.

11. Postel-Vinay S, Herbschleb K, Massard C, Woodcock V, Soria JC, Walter AO, et al. First-in-human phase I study of the bromodomain and extraterminal motif inhibitor BAY 1238097: emerging pharmacokinetic/pharmacodynamic relationship and early termination due to unexpected toxicity. Eur J Cancer 2019;109:103–10.

12. Shapiro GI, LoRusso P, Dowlati A, T Do K, Jacobson CA, Vaishampayan U, et al. A Phase 1 study of RO6870810, a novel bromodomain and extra-terminal protein inhibitor, in patients with NUT carcinoma, other solid tumours, or diffuse large B-cell lymphoma. Br J Cancer 2021;124:744–53.

13. Aggarwal RR, Schweizer MT, Nanus DM, Pantuck AJ, Heath EI, Campeau E, et al. A phase Ib/IIa study of the pan-BET inhibitor ZEN-3694 in combination with enzalutamide in patients with metastatic castration-resistant prostate cancer. Clin Cancer Res 2020;26:5338–47.

14. Pericole FV, Lazarini M, de Paiva LB, Duarte A, Vieira Ferro KP, Niemann FS, et al. BRD4 inhibition enhances azacitidine efficacy in acute myeloid leukemia and myelodysplastic syndromes. Front Oncol 2019;9:16.

15. Trabucco SE, Gerstein RM, Evens AM, Bradner JE, Shultz LD, Greiner DL, et al. Inhibition of bromodomain proteins for the treatment of human diffuse large B-cell lymphoma. Clin Cancer Res 2015;21:113–22.

16. Roboz GJ, Desai P, Lee S, Ritchie EK, Winer ES, DeMario M, et al. A dose escalation study of RO6870810/TEN-10 in patients with acute myeloid leukemia and myelodysplastic syndrome. Leuk Lymphoma 2021;62:1740–8.

17. Sun Y, Han J, Wang Z, Li X, Sun Y, Hu Z. Safety and efficacy of bromodomain and extra-terminal inhibitors for the treatment of hematological malignancies and solid tumors: a systematic study of clinical trials. Front Pharmacol 2020;11:621093.

18. Zhang P, Li R, Xiao H, Liu W, Zeng X, Xie G, et al. BRD4 inhibitor AZD5153 suppresses the proliferation of colorectal cancer cells and sensitizes the anticancer effect of PARP inhibitor. Int J Biol Sci 2019;15:1942–54.

19. Wilson AJ, Stubbs M, Liu P, Ruggeri B, Khabele D. The BET inhibitor INCB054329 reduces homologous recombination efficiency and augments PARP inhibitor activity in ovarian cancer. Gynecol Oncol 2018;149:575–84.

20. Karakashev S, Zhu H, Yokoyama Y, Zhao B, Fatkhutdinov N, Kossenkov AV, et al. BET bromodomain inhibition synergizes with PARP inhibitor in epithelial ovarian cancer. Cell Rep 2017;21:3398–405.

21. Miller AL, Garcia PL, Fehling SC, Gamblin TL, Vance RB, Council LN, et al. The BET inhibitor JQ1 augments the antitumor efficacy of gemcitabine in preclinical models of pancreatic cancer. Cancers 2021;13:3470.

22. Kharenko OA, Patel RG, Calosing C, van der Horst EH. Combination of ZEN-3694 with CDK4/6 inhibitors reverses acquired resistance to CDK4/6 inhibitors in ER-positive breast cancer. Cancer Gene Ther 2022;29:859–69.

23. Takimoto-Shimomura T, Tsukamoto T, Maegawa S, Fujibayashi Y, Matsumura-Kimoto Y, Mizuno Y, et al. Dual targeting of bromodomain-containing 4 by AZD5153 and BCL2 by AZD4320 against B-cell lymphomas concomitantly overexpressing c-MYC and BCL2. Invest New Drugs 2019;37:210–22.

24. Takashima Y, Kikuchi E, Kikuchi J, Suzuki M, Kikuchi H, Maeda M, et al. Bromodomain and extraterminal domain inhibition synergizes with WEE1-inhibitor AZD1775 effect by impairing nonhomologous end joining and enhancing DNA damage in nonsmall cell lung cancer. Int J Cancer 2020;146:1114–24.

25. Yi JS, Sias-Garcia O, Nasholm N, Hu X, Iniguez AB, Hall MD, et al. The synergy of BET inhibitors with aurora a kinase inhibitors in MYCN-amplified neuroblastoma is heightened with functional TP53. Neoplasia 2021;23:624–33.

26. Gusyatiner O, Bady P, Pham MDT, Lei Y, Park J, Daniel RT, et al. BET inhibitors repress expression of interferon-stimulated genes and synergize with HDAC inhibitors in glioblastoma. Neuro Oncol 2021;23:1680–92.

27. Yumeen S, Mirza FN, Lewis JM, King ALO, Kim SR, Carlson KR, et al. JAK inhibition synergistically potentiates BCL2, BET, HDAC, and proteasome inhibition in advanced CTCL. Blood Adv 2020;4:2213–26.

28. Harrison CN, Gupta VK, Gerds AT, Rampal R, Verstovsek S, Talpaz M, et al. Phase III MANIFEST-2: pelabresib + ruxolitinib vs placebo + ruxolitinib in JAK inhibitor treatment-naive myelofibrosis. Future Oncol 2022;18:2987–97.

29. Mascarenhas J, Kremyanskaya M, Patriarca A, Harrison C, Bose P, Rampal RK, et al. MPN-375 BET inhibitor pelabresib (CPI-0610) combined with ruxolitinib in patients with myelofibrosis - JAK inhibitor-naie or with suboptimal response to ruxolitinib - preliminary data from the MANIFEST study. Clin Lymphoma Myeloma Leuk 2022;22:S335–S6.

30. Rhyasen GW, Hattersley MM, Yao Y, Dulak A, Wang W, Petteruti P, et al. AZD5153: a novel bivalent BET bromodomain inhibitor highly active against hematologic malignancies. Mol Cancer Ther 2016;15:2563–74.

31. Shen G, Chen J, Zhou Y, Wang Z, Ma Z, Xu C, et al. AZD5153 inhibits prostate cancer cell growth in vitro and in vivo . Cell Physiol Biochem 2018;50:798–809.

32. Xu K, Chen D, Qian D, Zhang S, Zhang Y, Guo S, et al. AZD5153, a novel BRD4 inhibitor, suppresses human thyroid carcinoma cell growth in vitro and in vivo . Biochem Biophys Res Commun 2018;499:531–7.

33. Bradbury RH, Callis R, Carr GR, Chen H, Clark E, Feron L, et al. Optimization of a series of bivalent triazolopyridazine based bromodomain and extraterminal inhibitors: the discovery of (3R)-4-[2-[4-[1-(3-Methoxy-[1,2,4]triazolo[4,3-b]pyridazin-6-yl)-4-piperidyl]phen oxy]ethyl]-1,3-dimethyl-piperazin-2-one (AZD5153). J Med Chem 2016;59:7801–17.

34. Tosello V, Milani G, Martines A, Macri N, Van Loocke W, Matthijssens F, et al. A novel t(8;14)(q24;q11) rearranged human cell line as a model for mechanistic and drug discovery studies of NOTCH1-independent human T-cell leukemia. Cells 2018;7:160.

35. Sun C, Yin J, Fang Y, Chen J, Jeong KJ, Chen X, et al. BRD4 inhibition is synthetic lethal with PARP inhibitors through the induction of homologous recombination deficiency. Cancer Cell 2018;33:401–16.

36. Huang M, Zeki J, Sumarsono N, Coles GL, Taylor JS, Danzer E, et al. Epigenetic targeting of TERT-associated gene expression signature in human neuroblastoma with TERT overexpression. Cancer Res 2020;80:1024–35.

37. Andersen CL, Christie AL, Rosen A, Maratea K, Hattersley M, Travers J, et al. Identification of novel combination therapies active in BCL2 inhibitor-resistant patient-derived AML models. Blood 2019;134:1273.31698435

38. Li X, Fu Y, Yang B, Guo E, Wu Y, Huang J, et al. BRD4 inhibition by AZD5153 promotes antitumor immunity via depolarizing M2 macrophages. Front Immunol 2020;11:89.

39. Collins TA, Hattersley MM, Yates J, Clark E, Mondal M, Mettetal JT. Translational modeling of drug-induced myelosuppression and effect of pretreatment myelosuppression for AZD5153, a selective BRD4 inhibitor. CPT Pharmacometrics Syst Pharmacol 2017;6:357–64.

40. Eisenhauer EA, Therasse P, Bogaerts J, Schwartz LH, Sargent D, Ford R, et al. New response evaluation criteria in solid tumours: revised RECIST guideline (version 1.1). Eur J Cancer 2009;45:228–47.

41. Cheson BD, Pfistner B, Juweid ME, Gascoyne RD, Specht L, Horning SJ, et al. Revised response criteria for malignant lymphoma. J Clin Oncol 2007;25:579–86.

42. Cousin S, Blay JY, Brana Garcia I, de Bono JS, Le Tourneau C, Moreno V, et al. Safety, pharmacokinetic, pharmacodynamic and clinical activity of molibresib for the treatment of nuclear protein in testis carcinoma and other cancers: results of a phase I/II open-label, dose escalation study. Int J Cancer 2022;150:993–1006.

43. Ramasamy K, Nooka A, Quach H, Htut M, Popat R, Liedtke M, et al. A phase 1b dose-escalation/expansion study of BET inhibitor RO6870810 in patients with advanced multiple myeloma. Blood Cancer J 2021;11:149.

44. Dickinson M, Briones J, Herrera AF, Gonzalez-Barca E, Ghosh N, Cordoba R, et al. Phase 1b study of the BET protein inhibitor RO6870810 with venetoclax and rituximab in patients with diffuse large B-cell lymphoma. Blood Adv 2021;5:4762–70.

45. Fong PC, Boss DS, Yap TA, Tutt A, Wu P, Mergui-Roelvink M, et al. Inhibition of poly(ADP-ribose) polymerase in tumors from BRCA mutation carriers. N Engl J Med 2009;361:123–34.

46. Lin X, Huang X, Uziel T, Hessler P, Albert DH, Roberts-Rapp LA, et al. HEXIM1 as a robust pharmacodynamic marker for monitoring target engagement of BET family bromodomain inhibitors in tumors and surrogate tissues. Mol Cancer Ther 2017;16:388–96.

47. Tontsch-Grunt U, Traexler PE, Baum A, Musa H, Marzin K, Wang S, et al. Therapeutic impact of BET inhibitor BI 894999 treatment: backtranslation from the clinic. Br J Cancer 2022;127:577–86.

48. Bowry A, Piberger AL, Rojas P, Saponaro M, Petermann E. BET inhibition induces HEXIM1- and RAD51-dependent conflicts between transcription and replication. Cell Rep 2018;25:2061–9.

49. Lui GYL, Shaw R, Schaub FX, Stork IN, Gurley KE, Bridgwater C, et al. BET, SRC, and BCL2 family inhibitors are synergistic drug combinations with PARP inhibitors in ovarian cancer. EBioMedicine 2020;60:102988.

50. Miller AL, Fehling SC, Garcia PL, Gamblin TL, Council LN, van Waardenburg R, et al. The BET inhibitor JQ1 attenuates double-strand break repair and sensitizes models of pancreatic ductal adenocarcinoma to PARP inhibitors. EBioMedicine 2019;44:419–30.

Associated Data

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