Core-binding factor leukemia hijacks the T-cell-prone PU.1 antisense promoter

The blood system serves as a key model for cell differentiation and cancer. It is orchestrated by precise spatiotemporal expression of crucial transcription factors. One of the key master regulators in the hematopoietic systems is PU.1. Reduced levels of PU.1 are characteristic for human acute myeloid leukemia (AML) and are known to induce AML in mouse models. Here, we show that transcriptional downregulation of PU.1 is an active process involving an alternative promoter in intron 3 that is induced by RUNX transcription factors driving noncoding antisense transcription. Core-binding factor (CBF) fusions RUNX1-ETO and CBFβ-MYH11 in t(8;21) and inv(16) AML, respectively, activate the PU.1 antisense promoter that results in a shift from sense toward antisense transcription and myeloid differentiation blockade. In patients with CBF-AML, we found that an elevated antisense/sense transcript and promoter accessibility ratio represents a hallmark compared with normal karyotype AML or healthy CD34+ cells. Competitive interaction of an enhancer with the proximal or the antisense promoter forms a binary on/off switch for either myeloid or T-cell development. Leukemic CBF fusions thus use a physiological mechanism used by T cells to decrease sense transcription. Our study is the first example of a sense/antisense promoter competition as a crucial functional switch for gene expression perturbation by oncogenes. Hence, this disease mechanism reveals a previously unknown Achilles heel for future precise therapeutic targeting of oncogene-induced chromatin remodeling.

Talazoparib versus chemotherapy in patients with germline BRCA1/2-mutated HER2-negative advanced breast cancer: final overall survival results from the EMBRACA trial

BACKGROUND

In EMBRACA, talazoparib prolonged progression-free survival versus chemotherapy (hazard ratio [HR] 0.542 [95% confidence interval (CI) 0.413-0.711]; P < 0.0001) and improved patient-reported outcomes (PRO) in germline BRCA1/2 (gBRCA1/2)-mutated advanced breast cancer (ABC). We report final overall survival (OS).

PATIENTS AND METHODS

This randomized phase III trial enrolled patients with gBRCA1/2-mutated HER2-negative ABC. Patients received talazoparib or physician's choice of chemotherapy. OS was analyzed using stratified HR and log-rank test and prespecified rank-preserving structural failure time model to account for subsequent treatments.

RESULTS

A total of 431 patients were entered in a randomized study (287 talazoparib/144 chemotherapy) with 412 patients treated (286 talazoparib/126 chemotherapy). By 30 September 2019, 216 deaths (75.3%) occurred for talazoparib and 108 (75.0%) chemotherapy; median follow-up was 44.9 and 36.8 months, respectively. HR for OS with talazoparib versus chemotherapy was 0.848 (95% CI 0.670-1.073; P = 0.17); median (95% CI) 19.3 months (16.6-22.5 months) versus 19.5 months (17.4-22.4 months). Kaplan-Meier survival percentages (95% CI) for talazoparib versus chemotherapy: month 12, 71% (66% to 76%)/74% (66% to 81%); month 24, 42% (36% to 47%)/38% (30% to 47%); month 36, 27% (22% to 33%)/21% (14% to 29%). Most patients received subsequent treatments: for talazoparib and chemotherapy, 46.3%/41.7% received platinum and 4.5%/32.6% received a poly(ADP-ribose) polymerase (PARP) inhibitor, respectively. Adjusting for subsequent PARP and/or platinum use, HR for OS was 0.756 (95% bootstrap CI 0.503-1.029). Grade 3-4 adverse events occurred in 69.6% (talazoparib) and 64.3% (chemotherapy) patients, consistent with previous reports. Extended follow-up showed significant overall improvement and delay in time to definitive clinically meaningful deterioration in global health status/quality of life and breast symptoms favoring talazoparib versus chemotherapy (P < 0.01 for all), consistent with initial analyses.

CONCLUSIONS

In gBRCA1/2-mutated HER2-negative ABC, talazoparib did not significantly improve OS over chemotherapy; subsequent treatments may have impacted analysis. Safety was consistent with previous observations. PRO continued to favor talazoparib.

Abstract P6-18-12: EMBRACA: Efficacy and safety of talazoparib or physician's choice of therapy in patients with advanced breast cancer and a germline BRCA1/2 mutation: A regional analysis

Background: Talazoparib (TAL) prevents DNA damage repair by inhibiting poly (ADP-ribose) polymerase (PARP) enzymes and trapping PARP on DNA, resulting in cell death in BRCA1/2-mutated cells.

Methods: EMBRACA is an open-label, randomized, 2-arm phase 3 trial in which efficacy and safety of TAL (1 mg/d) were compared with physician's choice of therapy (PCT; capecitabine, eribulin, gemcitabine, vinorelbine) in patients (pts) with locally advanced or metastatic breast cancer (ABC) and a germline BRCA mutation (gBRCAm). Outcomes were assessed by region of the world (North America [NA]; Europe [EU]; rest of world [ROW]). Progression-free survival (PFS), objective response rate (ORR), and clinical benefit rate (CBR) at 24 wks were assessed; safety was also assessed.

Results: 431 pts were randomized 2:1. Pt characteristics were well balanced, although a higher percentage of pts in ROW had more severe disease (eg, triple-negative breast cancer [TNBC], Disease-free interval [DFI]&lt;12 mo, more distant metastases, more disease sites) and were on average younger than pts in NA/EU. TAL provided improvement in PFS, ORR, and CBR in all regions vs PCT. The most common toxicities with TAL included anemia, neutropenia, thrombocytopenia, fatigue, and nausea for all regions. Alopecia was less frequent with TAL in EU/ROW. Serious adverse events for pts receiving TAL were more frequent in EU than NA/ROW. Incidences of adverse events associated with permanent treatment discontinuation in pts receiving TAL were low in all regions and generally lower than for PCT.

Table 1CategoryNA* (N=156)EU* (N=190)ROW* (N=85)Mean age, years49.049.244.2Race, %   White76.971.152.9Black5.8-3.5Asian5.8-42.4Not reported-27.4-TNBC, %424447BRCA1**, %414748BRCA2**, %595352DFI&lt;12 mo, %313444Distant metastases, %949397≥3 disease sites, %474049PFS, (hazard ratio [HR]; [95% CI]); P value0.46 [0.29-0.74] P=.00090.52 [0.33-0.80]; P&lt;.0030.57 [0.31-1.07] ;P=.08ORR (odds ratio [OR] [95% CI]); P value5.54 [2.4-16.1];P&lt;.00013.75 [1.57-9.87]; P=.0016.7 [1.61-28.39]; P=.001CBR (OR [95% CI]); P value4.71 [2.20-10.57]; P&lt;.00013.39 [1.56-7.36]; P=.00075.70 [1.70-17.13]; P=.002Hematologic AEs, %   Anemia50.558.642.6Neutropenia31.332.346.3Thrombocytopenia28.322.635.2Nonhematologic AEs, %   Fatigue59.643.650.0Nausea47.545.957.4Headache32.330.837.0Alopecia34.320.320.4Serious adverse events, %25.340.622.2Treatment discontinuation, n/N, (%)   TAL7/99 (7.1)12/133 (9.0)3/54 (5.6)PCT7/43 (16.3)3/54 (5.6)2/29 (6.9)AE, adverse event; CI, confidence interval; *NA (United States); EU (Belgium, France, Germany, Ireland, Italy, Poland, Spain, United Kingdom, Russia, Ukraine, Israel); ROW (Brazil, Korea, Australia, Taiwan).**Central laboratory.

Conclusions: In pts with gBRCAm ABC, TAL demonstrated significant improvements in clinical outcomes compared with PCT regardless of the region of the world in which they lived. However, slight differences among the regions in baseline characteristics were noted, possibly due to regional variation in diagnosis and detection of gBRCAm ABC as well as different treatment paradigms for metastatic breast cancer.

Funding: Medivation LLC, acquired by Pfizer.

Citation Format: Mina L, Lee K-H, Gonçalves A, Woodward N, Hurvitz SA, Diab S, Yerushalmi R, Goodwin A, Moreira Costa Zorzetto M, Kim S-B, Czibere A, Tudor IC, Gauthier E, Litton JK, Ettl J. EMBRACA: Efficacy and safety of talazoparib or physician's choice of therapy in patients with advanced breast cancer and a germline BRCA1/2 mutation: A regional analysis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-18-12.

Abstract OT3-03-02: A phase 2, open-label, single-arm, multi-center study of talazoparib for neoadjuvant treatment of germline BRCA1/2 mutation patients with early-stage triple-negative breast cancer (TNBC)

Background: Approximately 15% of all breast cancers are triple negative and deleterious BRCA1/2 mutations are found in ˜11% of unselected TNBC. In the phase 3 EMBRACA trial (NCT01945775), the poly (ADP-ribose) polymerase (PARP) inhibitor talazoparib was superior to chemotherapy in prolonging progression-free survival in BRCA1/2 mutation patients with advanced breast cancer. A recent pilot study (NCT02282345) of 20 patients, explored the feasibility of neoadjuvant talazoparib in BRCA1/2 mutation patients; pathologic complete response (pCR) was reported at 53% with 6 months of single agent talazoparib.

Trial Design: This phase 2, single-arm, open-label, multi-center study has a Simon 2-stage design. Eligible pts have stage I-III invasive TNBC (ER and PR &lt;10%), with germline BRCA1/2 mutations who are suitable for neoadjuvant therapy. Pts will receive talazoparib 1 mg daily for 24 weeks, followed by breast surgery, which should occur within 4 to 6 weeks of the last dose. Ultrasound will be performed serially to assess tumor response. The primary objective is to evaluate pCR after 24 weeks of neoadjuvant talazoparib. pCR (ypT0/is ypN0) will be assessed by independent central review. Safety will also be assessed. Pts will be followed for at least 5 years to assess long term outcomes (event-free and overall survival). After surgery, any further adjuvant therapy will be given at the discretion of the treating physician. Pt reported outcomes will be assessed electronically including the global health status/quality of life, functions, and symptoms using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaires C30 and BR23. Plasma pharmacokinetic (PK) samples for determination of talazoparib concentrations will be collected at defined timepoints to describe the steady-state PK of talazoparib. Exploratory biomarker research will also take place. Approximately 122 men and women will be enrolled in the study, of which 112 evaluable pts are planned. With 112 evaluable pts and one interim futility look, the null hypothesis that the true pCR rate is 35% will be tested against a 1-sided alternative. This design yields a 1-sided type 1 error rate of 2.5% and power of 90% when the true pCR rate is 50%. An interim analysis will be performed to evaluate the efficacy of talazoparib after 28 evaluable pts undergo talazoparib treatment for 24 weeks, followed by surgery, and are assessed for pCR by central review. This trial is currently recruiting and is registered at clinicaltrials.gov (NCT03499353).

Funding: This study is sponsored by Pfizer, Inc.

Citation Format: Litton J, Symmans F, Gogineni K, Saltzman M, Telli ML, Usha L, Chakrabarti J, Tudor IC, Quek RG, Czibere A. A phase 2, open-label, single-arm, multi-center study of talazoparib for neoadjuvant treatment of germline BRCA1/2 mutation patients with early-stage triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT3-03-02.

Abstract P6-15-02: Phenotypically distinct HRG positive cancer cells impact standard of care therapies in metastatic breast cancer models

ErbB3 is a member of the human epidermal growth factor receptor (ErbB or HER) family which is comprised of four receptors (ErbB1-4). A defining feature of the ErbB network is that two members of the family, ErbB2 and ErbB3, are non-autonomous. ErbB2 lacks the capacity to interact with a growth-factor ligand, whereas the kinase activity of ErbB3 is defective. Heregulin (HRG), the ErbB3 ligand, has been identified as a potent driver of proliferation and enhanced survival. HRG expression leads to a distinct tumor cell phenotype characterized by an inability to respond to the effects of numerous Standard of Care (SOC) therapies, including chemotherapies, anti-hormonal agents and other targeted therapeutics.

In surveys of HRG expression, we have shown the presence of HRG+ cells in approximately 50% of the cases of most solid tumor types. We hypothesize that these HRG+ cells are protected from the effects of SOC therapy and continue to proliferate even in the presence of SOC, resulting in limited clinical benefit. In this model, if HRG activity is blocked, HRG+ cells become susceptible to SOC, resulting in enhanced clinical benefit. Seribantumab is a fully human anti-ErbB3 monoclonal antibody designed to block HRG activity by inhibiting the binding of HRG to ErbB3. In the presence of seribantumab, HRG+ tumor cells are predicted to be able to respond to co-administered SOC therapy.

For hormone receptor positive (HR+) breast cancer, hormone deprivation strategies have proven clinical benefit in the adjuvant and metastatic settings. Unfortunately, clinical benefit from these therapies can be short-lived in some patients. Optimal clinical management of these patients requires a comprehensive molecular understanding of the drivers of rapid clinical progression. We and others have found that HRG mRNA expression measured in tumor samples defines a subgroup of patients who derive only limited clinical benefit from SOC when compared to patients whose tumors do not express HRG. This was observed in a previously published Phase 2 clinical study with exemestane, and preclinically with multiple classes of anti-hormonal agents, including letrozole and fulvestrant -- treatments that currently represent the mainstay of treatment options for HR+, HER2 negative (HER2-) advanced breast cancer.

Here we will present data supporting the hypothesis that phenotypically distinct HRG+ cells in breast cancer models persist despite treatment with SOC and various novel classes of therapy. We will also show that the addition of the anti-ErbB3 antibody seribantumab to these other therapies promotes sustained treatment responses. Continued expansion of HRG+ cells could be the key to rapid clinical progression in breast cancer patients treated with SOC therapy. These findings support the development of seribantumab in combination with anti-hormonal agents in a planned Phase 3 clinical trial in HR+, HER2- advanced breast cancer.

Citation Format: Finn GJ, Zhang H, Blois A, Mathews SE, Kudla AJ, Baum JS, Demars NA, Cieslewicz MJ, Czibere A. Phenotypically distinct HRG positive cancer cells impact standard of care therapies in metastatic breast cancer models [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-15-02.

Azacitidine and donor lymphocyte infusions as first salvage therapy for relapse of AML or MDS after allogeneic stem cell transplantation

The combination of azacitidine and donor lymphocyte infusions (DLI) as first salvage therapy for relapse after allogeneic transplantation (allo-HSCT) was studied in 30 patients with acute myeloid leukemia (AML; n=28) or myelodysplastic syndromes (MDS; n=2) within a prospective single-arm multicenter phase-II trial. Treatment schedule contained up to eight cycles azacitidine (100 mg/m(2)/day, days 1-5, every 28 days) followed by DLI (from 1-5 × 10(6) to 1-5 × 10(8) CD3(+)cells/kg) after every second azacitidine cycle. A median of three courses azacitidine (range 1-8) were administered, and 22 patients (73%) received DLI. Overall response rate was 30%, including seven complete remissions (CRs, 23%) and two partial remissions (7%). Five patients remain in CR for a median of 777 days (range 461-888). Patients with MDS or AML with myelodysplasia-related changes were more likely to respond (P=0.011), and a lower blast count (P=0.039) as well as high-risk cytogenetics (P=0.035) correlated with the likelihood to achieve CR. Incidence of acute and chronic graft-versus-host disease was 37% and 17%, respectively. Neutropenia and thrombocytopenia grade III/IV occurred during 65% and 63% of treatment cycles, while infections were the most common grade III/IV non-hematological toxicity. Azacitidine and DLI as salvage therapy is safe, induces long-term remissions and may become an alternative for patients with AML or MDS relapsing after allo-HSCT.

Bendamustine in patients with relapsed or refractory multiple myeloma

Objective

In patients with multiple myeloma, bendamustine monotherapy is effective as 1^st and 2^nd line therapy. However, data for patients with advanced multiple myeloma is rare.

Methods

In this retrospective analysis we have identified 39 patients with relapsed or refractory multiple myeloma by means of case research, who have been treated at our institution with bendamustine as salvage therapy. After in median 2 lines of prior therapy (range:1-5) patients received in median 3 (range: 1-10) cycles of bendamustine. Bendamustine dosage was 80-150 mg on day 1+2 of a monthly cycle. Bendamustine was administered as monotherapy in 39% of patients, whereas 61% received concomitant steroids.

Results

Toxicity was mild to moderate. Response rates were as follows: 3% vgPR, 33% PR, 18% MR, 26% SD and 20% PD. The median event-free and overall survival were 7 and 17 months, respectively.

Conclusions

In conclusion, in patients with advanced multiple myeloma bendamustine is effective and associated with mild toxicity. Therefore, the role of bendamustine in patients with multiple myeloma should be investigated in further clinical trials.

The hematopoietic stem cell in chronic phase CML is characterized by a transcriptional profile resembling normal myeloid progenitor cells and reflecting loss of quiescence

We found that composition of cell subsets within the CD34+ cell population is markedly altered in chronic phase (CP) chronic myeloid leukemia (CML). Specifically, proportions and absolute cell counts of common myeloid progenitors (CMP) and megakaryocyte-erythrocyte progenitors (MEP) are significantly greater in comparison to normal bone marrow whereas absolute numbers of hematopoietic stem cells (HSC) are equal. To understand the basis for this, we performed gene expression profiling (Affymetrix HU-133A 2.0) of the distinct CD34+ cell subsets from six patients with CP CML and five healthy donors. Euclidean distance analysis revealed a remarkable transcriptional similarity between the CML patients' HSC and normal progenitors, especially CMP. CP CML HSC were transcriptionally more similar to their progeny than normal HSC to theirs, suggesting a more mature phenotype. Hence, the greatest differences between CP CML patients and normal donors were apparent in HSC including downregulation of genes encoding adhesion molecules, transcription factors, regulators of stem-cell fate and inhibitors of cell proliferation in CP CML. Impaired adhesive and migratory capacities were functionally corroborated by fibronectin detachment analysis and transwell assays, respectively. Based on our findings we propose a loss of quiescence of the CML HSC on detachment from the niche leading to expansion of myeloid progenitors.