Role of platelet count in a murine stasis model of deep vein thrombosis

Platelets are core components of thrombi but their effect on thrombus burden during deep vein thrombosis (DVT) has not been fully characterized. We examined the role of thrombopoietin-altered platelet count on thrombus burden in a murine stasis model of DVT. To modulate platelet count compared to baseline, CD1 mice were pretreated with thrombopoietin antisense oligonucleotide (THPO-ASO, 56% decrease), thrombopoietin mimetic (TPO-mimetic, 36% increase), or saline (within 1%). Thrombi and vein walls were examined on postoperative days (POD) 3 and 7. Thrombus weights on POD 3 were not different between treatment groups (p = .84). The mean thrombus weights on POD 7 were significantly increased in the TPO-mimetic cohort compared to the THPO-ASO (p = .005) and the saline (p = .012) cohorts. Histological grading at POD 3 revealed a significantly increased smooth muscle cell presence in the thrombi and CD31 positive channeling in the vein wall of the TPO-mimetic cohort compared to the saline and THPO-ASO cohorts (p < .05). No differences were observed in histology on POD 7. Thrombopoietin-induced increased platelet count increased thrombus weight on POD 7 indicating platelet count may regulate thrombus burden during early resolution of venous thrombi in this murine stasis model of DVT.

Prognostic impact of chronic lymphocytic leukemia comorbidity index in a young population: a real-world evidence study of a national gulf region cohort

In chronic lymphocytic leukaemia (CLL), comorbidities assessed by the CLL comorbidity index (CLL-CI) have been associated with outcomes in Western cohorts. We conducted a retrospective analysis of an unselected Middle Eastern cohort of newly diagnosed CLL patients seen at the Kuwait Cancer Control Center (n = 300). Compared to Western studies, these Middle Eastern patients were diagnosed at a younger age (median of 59) and had a higher comorbidity burden (69% non-low risk CLL-CI). A higher CLL-CI score was independently associated with significantly shorter event-free survival and greater risk of death. Our analysis demonstrates that CLL-CI is a valuable tool for comorbidity assessment and prognostic influence in (relatively young) Middle Eastern CLL patients.

Predicting Stage Progression in Binet Stage a Chronic Lymphocytic Leukemia

INTRODUCTION

The variable clinical course of chronic lymphocytic leukemia (CLL) and the lack of consensus on follow-up and treatment strategies have necessitated a prognostic model for identifying high-risk patients at the time of diagnosis.

METHODS

We involved a retrospective analysis of demographic and clinical characteristics of 212 patients diagnosed with Binet stage A CLL and thus eligible for risk stratification by both the International Prognostic Score for Early-stage CLL (IPS-E) and the alternative IPS-E (AIPS-E). We evaluated the applicability of these prognostic indices in our young, Middle Eastern cohort (median age 59 at diagnosis).

RESULTS

During the study period with a median follow-up of 3.5 years, 67 patients (32 %) experienced progression to first treatment and cumulative incidence of treatment was 13 % at 1 year and 28 % at 3 years after diagnosis. Sixty-nine (51 % of the 136 with a known value) patients harbored an unmutated immunoglobulin heavy chain gene (IGHV) and 21 (10 %) an 11q or 17p deletion with 11 % lacking FISH results. For each early-stage CLL prognostic index, more patients were identified as high-risk for disease progression (51 % of 124 patients evaluable for IPS-E; 42 % of 109 patients evaluable for AIPS-E) than intermediate-risk and low-risk. Multivariable models involving the IPS-E and AIPS-E components revealed that unmutated IGHV and elevated absolute lymphocyte count were significant predictors of earlier treatment requirement. Both prognostic scores were discriminative of time to first treatment (log-rank p < 0.001; c-statistics of 0.74 for IPS-E and 0.69 for AIPS-E).

CONCLUSION

Although clarity on clinical behavior with regard to initiation of treatment remains elusive, IPS-E and AIPS-E are valuable tools for identifying high-risk patients.

Clinical Correlates of Venetoclax-Based Combination Sensitivities to Augment Acute Myeloid Leukemia Therapy

The BCL2 inhibitor venetoclax combined with the hypomethylating agent azacytidine shows significant clinical benefit in a subset of patients with acute myeloid leukemia (AML); however, resistance limits response and durability. We prospectively profiled the ex vivo activity of 25 venetoclax-inclusive combinations on primary AML patient samples to identify those with improved potency and synergy compared with venetoclax + azacytidine (Ven + azacytidine). Combination sensitivities correlated with tumor cell state to discern three patterns: primitive selectivity resembling Ven + azacytidine, monocytic selectivity, and broad efficacy independent of cell state. Incorporation of immunophenotype, mutation, and cytogenetic features further stratified combination sensitivity for distinct patient subtypes. We dissect the biology underlying the broad, cell state-independent efficacy for the combination of venetoclax plus the JAK1/2 inhibitor ruxolitinib. Together, these findings support opportunities for expanding the impact of venetoclax-based drug combinations in AML by leveraging clinical and molecular biomarkers associated with ex vivo responses.

SIGNIFICANCE

By mapping drug sensitivity data to clinical features and tumor cell state, we identify novel venetoclax combinations targeting patient subtypes who lack sensitivity to Ven + azacytidine. This provides a framework for a taxonomy of AML informed by readily available sets of clinical and genetic features obtained as part of standard care. See related commentary by Becker, p. 437 . This article is featured in Selected Articles from This Issue, p. 419.

A retrospective validation of the IPSS-M molecular score in primary and therapy-related myelodysplastic syndromes (MDS)

A molecular scoring system (IPSS-M) was recently proposed for myelodysplastic syndrome (MDS). We conducted a retrospective study of adults with MDS referred 2019-2021. The primary outcomes were leukemia-free survival (LFS) and overall survival (OS). One hundred and forty-four patients diagnosed between 2011 and 2021 were analyzed. After IPSS-M re-stratification, 33% of patients were up-staged and 11% down-staged. Median follow-up was 2.8 years and 53 patients died (37%). Cumulative incidence of acute myeloid leukemia (AML) transformation was 20% at 3 years post-diagnosis. International Prognostic Scoring System (IPSS), revised version (IPSS-R) was significantly associated with LFS (log-rank p = 9.2e-05; 'very high' vs. 'low' risk HR = 3.85, p = 5.8e-04) and OS (log-rank p = 7.2e-06; 'very high' vs. 'low' HR = 5.09, p = 1.7e-04). IPSS-M was also a significant predictor of LFS (log-rank p = 1.1e-06; 'very high' vs. 'low' HR = 4.97, p = 2.2e-05) and OS (log-rank p = 4.8e-07; 'very high' vs. 'low' HR = 6.42, p = 2.5e-05) while providing better discrimination than IPSS-R for both outcomes. This mutation-incorporating prognostic index has greater discriminative potential than IPSS-R to predict AML transformation and any-cause mortality.

A validated composite comorbidity index predicts outcomes of CAR T-cell therapy in patients with diffuse large B-cell lymphoma

Chimeric antigen receptor T-cell therapy (CART) has extended survival of patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL). However, limited durability of response and prevalent toxicities remain problematic. Identifying patients who are at high risk of disease progression, toxicity, and death would inform treatment decisions. Although the cumulative illness rating scale (CIRS) has been shown to correlate with survival in B-cell malignancies, no prognostic score has been independently validated in CART recipients. We retrospectively identified 577 patients with relapsed/refractory DLBCL indicated for CART at 9 academic centers to form a learning cohort (LC). Random survival forest modeling of overall survival (OS) and progression-free survival (PFS) was performed to determine the most influential CIRS organ systems and severity grades. The presence of a severe comorbidity (CIRS score ≥ 3) in the respiratory, upper gastrointestinal, hepatic, or renal system, herein termed "Severe4," had the greatest impact on post-CART survival. Controlling for other prognostic factors (number of prior therapies, Eastern Cooperative Oncology Group performance status, BCL6 translocation, and molecular subtype), Severe4 was strongly associated with shorter PFS and OS in the LC and in an independent single-center validation cohort (VC). Severe4 was also a significant predictor of grade ≥3 cytokine release syndrome in the LC, while maintaining this trend in the VC. Thus, our results indicate that adverse outcomes for patients with DLBCL meant to receive CART can be predicted using a simplified CIRS-derived comorbidity index.

Real-World Evaluation of Disease Progression After CDK 4/6 Inhibitor Therapy in Patients With Hormone Receptor-Positive Metastatic Breast Cancer

BACKGROUND

Cyclin-dependent kinase 4/6 inhibitors (CDKi) have changed the landscape for treatment of patients with hormone receptor positive, human epidermal growth factor receptor 2-negative (HR+/HER-) metastatic breast cancer (MBC). However, next-line treatment strategies after CDKi progression are not yet optimized. We report here the impact of clinical and genomic factors on post-CDKi outcomes in a single institution cohort of HR+/HER2- patients with MBC.

METHODS

We retrospectively reviewed the medical records of patients with HR+/HER2- MBC that received a CDKi between April 1, 2014 and December 1, 2019 at our institution. Data were summarized using descriptive statistics, the Kaplan-Meier method, and regression models.

RESULTS

We identified 140 patients with HR+/HER2- MBC that received a CDKi. Eighty percent of patients discontinued treatment due to disease progression, with a median progression-free survival (PFS) of 6.0 months (95% CI, 5.0-7.1), whereas those that discontinued CDKi for other reasons had a PFS of 11.3 months (95% CI, 4.6-19.4) (hazard ratio (HR) 2.53, 95% CI, 1.50-4.26 [P = .001]). The 6-month cumulative incidence of post-CDKi progression or death was 51% for the 112 patients who progressed on CDKi. Patients harboring PTEN mutations pre-CDKi treatment had poorer clinical outcomes compared to those with wild-type PTEN.

CONCLUSION

This study highlights post-CDKi outcomes and the need for further molecular characterization and novel therapies to improve treatments for patients with HR+/HER2- MBC.

Secondary fusion proteins as a mechanism of BCR::ABL1 kinase-independent resistance in chronic myeloid leukaemia

Drug resistance in chronic myeloid leukaemia (CML) may occur via mutations in the causative BCR::ABL1 fusion or BCR::ABL1-independent mechanisms. We analysed 48 patients with BCR::ABL1-independent resistance for the presence of secondary fusion genes by RNA sequencing. We identified 10 of the most frequently detected secondary fusions in 21 patients. Validation studies, cell line models, gene expression analysis and drug screening revealed differences with respect to proliferation rate, differentiation and drug sensitivity. Notably, expression of RUNX1::MECOM led to resistance to ABL1 tyrosine kinase inhibitors in vitro. These results suggest secondary fusions contribute to BCR::ABL1-independent resistance and may be amenable to combined therapies.

Integrative analysis of drug response and clinical outcome in acute myeloid leukemia

Acute myeloid leukemia (AML) is a cancer of myeloid-lineage cells with limited therapeutic options. We previously combined ex vivo drug sensitivity with genomic, transcriptomic, and clinical annotations for a large cohort of AML patients, which facilitated discovery of functional genomic correlates. Here, we present a dataset that has been harmonized with our initial report to yield a cumulative cohort of 805 patients (942 specimens). We show strong cross-cohort concordance and identify features of drug response. Further, deconvoluting transcriptomic data shows that drug sensitivity is governed broadly by AML cell differentiation state, sometimes conditionally affecting other correlates of response. Finally, modeling of clinical outcome reveals a single gene, PEAR1, to be among the strongest predictors of patient survival, especially for young patients. Collectively, this report expands a large functional genomic resource, offers avenues for mechanistic exploration and drug development, and reveals tools for predicting outcome in AML.

Molecular alterations associated with rapid progression following CDK4/6 inhibitors (CDKi) in metastatic hormone receptor–positive breast cancer (mHRBC)

1054

Background: Combination of CDKi with endocrine therapy is a key treatment for mHRBC due to survival benefit and favorable safety profile. However, progressive disease inevitably develops and outcomes after CDKi discontinuation (dc) are not well-described. Within our institution, we previously reported clinical characteristics and outcomes for a cohort of 140 mHRBC patients who received CDKi therapy. Median progression-free survival (PFS) and overall survival (OS) post-CDKi dc were 7.0 and 15.4 months, respectively. However, 29% experienced rapid progression or death within 4 months following CDKi dc. Molecular predictors of rapid progression after CDKi are unknown and may help define therapies to improve outcomes. In this study, we sought to identify molecular predictors for rapid disease progression after CDKi dc in mHRBC. Methods: We identified within our cohort 34 patients with mHRBC who progressed on CDKi with next-generation sequencing (NGS) performed on pre-CDKi tissue samples. PFS and OS, measured from CDKi dc, were analyzed with the Kaplan-Meier estimator and log-rank test. Rapid progression was analyzed with logistic regression and Fisher’s exact test to evaluate association between pre-CDKi tumor mutation and rapid progression post-CDKi. Results: NGS of pre-CDKi tumor biopsies found 12 genes ( FGF3, FGF4, FGFR, PIK3CA, PTEN, AKT, RB1, CDKN2A, MYC, CCND1, ESR1, TP53) that were altered in ≥3 of the 34 patients. The six patients (18%) with a PTEN mutation (mut) had a median PFS of 3 months and median OS of 4 mo. In comparison, median PFS and OS of PTEN wild-type (wt) patients were 7 mo. (log-rank p=0.008) and 21 mo. (log-rank p<0.001), respectively. Moreover, those with PTENmut tumors were more likely to experience rapid progression compared to PTENwt (odds ratio = 7.0, 95% CI: 1.1 – 60.5, p=0.048). Notably, in the 10 rapid progression patients with pre-CDKi NGS results, alterations to PI3K pathway constituents were prevalent: PTENmut (40%), FGFRmut (50%), AKTmut (20%) and PIK3CAmut (40%). Conclusions: PI3K pathway alterations are prevalent in mHRBC patients who develop rapid progression post-CDKi dc, with PTENmut being the most significant predictor. These hypothesis-generating findings provide the basis for ongoing investigations to find clinical and molecular biomarkers that can help improve outcomes for mHRBC at risk of rapid progression post-CDKi therapy.[Table: see text]

Monocytic differentiation and AHR signaling as Primary Nodes of BET Inhibitor Response in Acute Myeloid Leukemia

To understand mechanisms of response to BET inhibitors (BETi), we mined the Beat AML functional genomic dataset and performed genome-wide CRISPR screens on BETi- sensitive and BETi- resistant AML cells. Both strategies revealed regulators of monocytic differentiation, SPI1, JUNB, FOS, and aryl-hydrocarbon receptor signaling (AHR/ARNT), as determinants of BETi response. AHR activation synergized with BETi while inhibition antagonized BETi-mediated cytotoxicity. Consistent with BETi sensitivity dependence on monocytic differentiation, ex vivo sensitivity to BETi in primary AML patient samples correlated with higher expression of monocytic markers CSF1R, LILRs, and VCAN. In addition, HL-60 cell line differentiation enhanced its sensitivity to BETi. Further, screens to rescue BETi sensitivity identified BCL2 and CDK6 as druggable vulnerabilities. Finally, monocytic AML patient samples refractory to venetoclax ex vivo were significantly more sensitive to combined BETi + venetoclax. Together, our work highlights mechanisms that could predict BETi response and identifies combination strategies to overcome resistance.

The Chronic Lymphocytic Leukemia Comorbidity Index (CLL-CI): A Three-Factor Comorbidity Model

PURPOSE

Comorbid medical conditions define a subset of patients with chronic lymphocytic leukemia (CLL) with poor outcomes. However, which comorbidities are most predictive remains understudied.

EXPERIMENTAL DESIGN

We conducted a retrospective analysis from 10 academic centers to ascertain the relative importance of comorbidities assessed by the cumulative illness rating scale (CIRS). The influence of specific comorbidities on event-free survival (EFS) was assessed in this derivation dataset using random survival forests to construct a CLL-specific comorbidity index (CLL-CI). Cox models were then fit to this dataset and to a single-center, independent validation dataset.

RESULTS

The derivation and validation sets comprised 570 patients (59% receiving Bruton tyrosine kinase inhibitor, BTKi) and 167 patients (50% receiving BTKi), respectively. Of the 14 CIRS organ systems, three had a strong and stable influence on EFS: any vascular, moderate/severe endocrine, moderate/severe upper gastrointestinal comorbidity. These were combined to create the CLL-CI score, which was categorized into 3 risk groups. In the derivation dataset, the median EFS values were 58, 33, and 20 months in the low, intermediate, and high-risk groups, correspondingly. Two-year overall survival (OS) rates were 96%, 91%, and 82%. In the validation dataset, median EFS values were 81, 40, and 23 months (two-year OS rates 97%/92%/88%), correspondingly. Adjusting for prognostic factors, CLL-CI was significantly associated with EFS in patients treated with either chemo-immunotherapy or with BTKi in each of our 2 datasets.

CONCLUSIONS

The CLL-CI is a simplified, CLL-specific comorbidity index that can be easily applied in clinical practice and correlates with survival in CLL.

The AML microenvironment catalyzes a stepwise evolution to gilteritinib resistance

Our study details the stepwise evolution of gilteritinib resistance in FLT3-mutated acute myeloid leukemia (AML). Early resistance is mediated by the bone marrow microenvironment, which protects residual leukemia cells. Over time, leukemia cells evolve intrinsic mechanisms of resistance, or late resistance. We mechanistically define both early and late resistance by integrating whole-exome sequencing, CRISPR-Cas9, metabolomics, proteomics, and pharmacologic approaches. Early resistant cells undergo metabolic reprogramming, grow more slowly, and are dependent upon Aurora kinase B (AURKB). Late resistant cells are characterized by expansion of pre-existing NRAS mutant subclones and continued metabolic reprogramming. Our model closely mirrors the timing and mutations of AML patients treated with gilteritinib. Pharmacological inhibition of AURKB resensitizes both early resistant cell cultures and primary leukemia cells from gilteritinib-treated AML patients. These findings support a combinatorial strategy to target early resistant AML cells with AURKB inhibitors and gilteritinib before the expansion of pre-existing resistance mutations occurs.

Real-world analysis of disease progression after CDK 4/6 inhibitor (CDKi) therapy in patients with hormone receptor positive (HR+)/HER2- metastatic breast cancer (MBC)

e13030

Background: CDKi with endocrine therapy (ET) is approved treatment of metastatic HR+/HER2- breast cancer based on PFS benefit vs ET alone. Outcomes data following CDKi discontinuation (dc) is limited, with trials ongoing in this setting. The reported phenomenon of rapid progression within 4 months of CDKi dc raises concern over CDKi impact on HR+/HER2- MBC biology. This study aims to define outcomes after CDKi dc and identify predictors of progression. Methods: This is a retrospective review of women ≥18 years with HR+/HER2- MBC who received CDKi between 4/1/14 and 12/1/19. Patient and tumor characteristics, pre and post CDKi tx, and reason for CDKi dc were collected. Time to event outcomes from date of CDKi dc (primary = PFS, secondary = Overall Survival, OS) were analyzed with Kaplan Meier estimators and Cox regression. Results: Analysis included 140 patients (median age 65 years), with most MBC (84%) arising from earlier stage disease. 51% of MBCs had visceral disease, and 66% received tx prior to CDKi. The most common CDKi was palbociclib (93%); and most common ET were letrozole (52%) and fulvestrant (40%). Median CDKi tx duration was 9 months (3.5 – 17.4) with 80% dc due to progression. Post CDKi txs included chemotherapy (44%), ET (24%), targeted tx (21%), no further tx (7%) and CDKi tx (4%). Median follow up was 12 months. mPFS post CDKi dc were 6.5 months (95% CI: 5.0 – 7.9) and 11.3 months (95% CI: 4.6 – 23.7) in patients who dc CDKi due to progression or other reasons, respectively (HR 1.77, 95%CI: 1.10-2.85). Among 112 patients who progressed on CDKi, estimated 4-month incidence of post CDKi progression or death was 31% (Table ). mOS post CDKi dc was 15.4 months (95%CI: 13.3-19.0) and mOS post CDKi initiation was 26.5 months (95% CI: 23.3 – 34.3). Visceral disease (HR 1.45, 95%CI: 1.01-2.08) and progression as reason for CDKi dc (HR 1.77, 95%CI: 1.1-2.85) were predictors of PFS (p < 0.05). Receiving fulvestrant with CDKi (HR 1.42, 95%CI: 0.96-1.0), prior chemotherapy in the metastatic setting (HR = 1.39, 95% CI: 0.90 – 2.14), and shorter CDKi duration were associated with non-significant increased risk of PFS. Conclusions: Rapid progression or death at 4 months occurred in 31% of MBCs following CDKi dc due to progression. Ongoing studies to define clinical and molecular characteristics of rapidly progressing tumors are underway to develop targeted tx approaches and improve outcomes.[Table: see text]

Abstract LT022: The AML microenvironment catalyzes a step-wise evolution to gilteritinib resistance

In acute myeloid leukemia (AML), activating mutations in FLT3 are the most common genetic abnormality. Multiple FLT3 inhibitors have been developed, including the FDA-approved inhibitor gilteritinib. However, AML patients only respond to gilteritinib for approximately 6 months due to the emergence of drug resistance. While gilteritinib eliminates blasts in peripheral circulation, residual blasts in the bone marrow microenvironment are protected by cytokines and growth factors. Persistence of these residual cells represents early resistance to treatment. How these cells adapt to survive in the marrow microenvironment remains unclear, but over time resistant subclones resume growth and lead to relapsed disease. At relapse, many patients have intrinsic resistance mutations, what we term late resistance. In this study, we used a stepwise model that charts the temporal evolution of early to late gilteritinib resistance. To recapitulate early resistance, we cultured the FLT3-ITD+ AML cell lines, MOLM-14 and MV4;11, with exogenous microenvironmental ligands that allow cells to become resistant to gilteritinib in a ligand-dependent manner. After 7 weeks, all cultures with ligand resumed growth (early resistance), whereas cells without ligand never resumed growth. Following ligand withdrawal, the cells become transiently sensitive to gilteritinib but resumed growth after 2 months (late resistance). We comprehensively analyzed early and late resistance by integrating whole exome sequencing, CRISPR/Cas9 screening, proteomics, metabolomics, and small-molecule inhibitor screening. Early resistance is characterized by slowly dividing cells and metabolic reprogramming, particularly with respect to lipid metabolism. Early resistant cultures also became uniquely dependent on Aurora kinase B (AURKB) for survival. We then validated these findings in primary AML cells from patients (N=11) treated with gilteritinib and found that early resistant cells demonstrated reduced cell cycle and alterations in lipid metabolism. Gene expression analysis of sequential stromal cell samples from AML patients (N=13) pre- and post gilteritinib treatment showed an increase in lipid metabolism following gilteritinib treatment, indicating that the microenvironment is also dynamic and in crosstalk with neighboring AML cells. Primary early resistant AML cells also became dependent on AURKB signaling, and were exquisitely sensitive to the combination of AURKB inhibitors and gilteritinib. In contrast, late resistance is driven by an expansion of pre-existing NRAS mutant subclones, consistent with the resistance profile of AML patients on gilteritinib. Metabolic reprogramming continued to evolve in late resistance with further dependence upon lipid metabolism. Our study provides mechanistic understanding of how the marrow microenvironment contributes to extrinsic early resistance, which then leads to late intrinsic resistance. We also define a unique vulnerability to AURKB inhibitors in early resistance that may thwart the expansion of late resistant NRAS subclones.

Citation Format: Sunil K. Joshi, Tamilla Nechiporuk, Daniel Bottomly, Paul Piehowski, Julie A. Reisz, Janét Pittsenbarger, Andy Kaempf, Sara J.C. Gosline, Yi-Ting Wang, Tao Liu, Cristina E. Tognon, Angelo D’Alessandro, Jeffrey W. Tyner, Shannon K. McWeeney, Karin D. Rodland, Brian J. Druker, Elie Traer. The AML microenvironment catalyzes a step-wise evolution to gilteritinib resistance [abstract]. In: Proceedings of the AACR Virtual Special Conference on the Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; 2021 Jan 11-12. Philadelphia (PA): AACR; Cancer Res 2021;81(5 Suppl):Abstract nr LT022.

CDK 4/6 inhibitors are associated with a high incidence of thrombotic events in women with breast cancer in real-world practice

PURPOSE

Cyclin-dependent kinase (CDK) 4/6 inhibitors are integral treatment for advanced hormone receptor positive breast cancer; however, venous thromboembolic events (VTE) occurred in 1%-5% of clinical trial patients. Thrombosis rates in the real-world setting remain unclear. We aimed to define the rate of thromboembolic events, risk factors for thrombosis on CDK 4/6 inhibitors and evaluate the Khorana VTE risk score as a predictive tool for VTE in patients on CDK 4/6 therapy.

METHODS

Multicenter retrospective analysis of adult breast cancer patients prescribed palbociclib, ribociclib, or abemaciclib. The primary endpoint was thrombosis during treatment or within 30 days of CDK inhibitor discontinuation. Cox regression was used to model time-to-thrombosis, starting from a patient's initiation of CDK 4/6 therapy. The extended Kaplan-Meier method and Cox modeling were used to assess the effect of time-varying thrombosis status on overall survival.

RESULTS

Two hundred and sixty-six patients were included (89% on palbociclib, 14% on abemaciclib, 7% on ribociclib). Twenty-nine thrombotic events occurred in 26 (9.8%) women. Of these events, 72% were venous and 34% were arterial. The 1-year incidence of thrombosis was 10.4% overall, 10.9% on palbociclib, 8.3% on ribociclib, and 4.8% on abemaciclib. Hemoglobin less than 10 g/dL was a statistically significant predictor of thrombosis (HR 3.53, P: .014). Khorana score ranged from 0-3, with the majority between 0 and 1 and was not predictive of VTE. Thrombosis was associated with reduced overall survival (HR 1.28, P: .128, median 7.3 months) compared to not having a CDK-associated clot (median 35.7 months).

DISCUSSION

VTE in our analysis is higher than reported in clinical trials and arterial thrombosis comprised over one-third of events. The highest incidence was with palbociclib, followed by ribociclib. Khorana score did not predict VTE risk. Larger, real-world studies are needed. The role for prophylactic anticoagulation is yet to be defined in this patient population.

Abstract 08: Advancing precision medicine combination drug screening: A miniaturized single-cell imaging platform for evaluating immunotherapy-small molecule combination therapeutics in individuals

Major efforts are under way to develop combination therapies to target multiple biologic pathways for effective synergistic cell killing and decrease the risk of cancer relapse. However, a major technical challenge is the lack of screening platforms that allow assessment of optimal combinations directly in individuals. Flow cytometry is a widely used option; however, the large amount of sample required limits the number of drug combinations that can be tested on primary patient samples. Moreover, many protein targets, especially intracellular proteins (e.g., phosphoproteins, immune modulatory molecules) are often present at low levels, making it challenging to detect via flow cytometry or other means—especially in conditions of drug inhibition whereby signal cannot be conclusively discriminated from background noise. We have developed a next-gen miniaturized single-cell imaging platform that evaluates the effect of drug combinations in primary patient tumor and immune cells, with quantitative detection sensitivity and single-cell granularity. We demonstrate the use of this platform technology to screen interactions between targeted agents and immune checkpoint inhibitors (ICIs) in individuals with acute myeloid leukemia (AML). In many tumor types, including AML, targeting tumor cells with small-molecule drugs while concomitantly inducing an antitumor immune response has the possibility of synergistic activities that avoid therapeutic resistance (1). However, many of the pathways of proliferation and survival that are targeted with small-molecule drugs are also important for the ability of tumor-reactive T cells to expand and function (2). For this reason, there is a distinct possibility that many drugs designed to kill tumor cells will also impair T-cell responses and thus not be compatible with immunotherapies such as ICIs. We show how platform functional readouts of ex vivo T-cell activation and tumor-cell killing, along with conventional and machine learning image-based single-cell analysis, provide new information on the effect of specific combination/single agents in individuals. We report observations of ICI rescue of T-cell proliferation and the synergistic effects of TIM3, MEK, and other combination agents. These results demonstrate the advantages of this precision technology to obtain new functional information that helps identify promising combinations—and to do so directly on samples that represent the functional and genetic diversity seen in AML (3).

References: 1. Hughes PE et al. Targeted therapy and checkpoint immunotherapy combinations for the treatment of cancer. Trends in Immunotherapy 2016. 2. Zitvogel L et al. Immunological aspect of cancer chemotherapy. Nature Reviews Immunology 2008. 3. Tyner JW et al. Functional genomic landscape of acute myeloid leukaemia. Nature 2018.

Note: This abstract was not presented at the conference.

Citation Format: Thomas Jacob, Yunqi Yan, Yoko Kosaka, Sophia Jena, Stephen E. Kurtz, Andy Kaempf, Tomi Mori, Young Hwan Chang, Bill H. Chang, Uma Borate, Elie Traer, Shannon K. McWeeney, Jody Martin, Jeffrey W. Tyner, Evan F. Lind, Tania Q. Vu. Advancing precision medicine combination drug screening: A miniaturized single-cell imaging platform for evaluating immunotherapy-small molecule combination therapeutics in individuals [abstract]. In: Proceedings of the AACR Special Conference on Advancing Precision Medicine Drug Development: Incorporation of Real-World Data and Other Novel Strategies; Jan 9-12, 2020; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_1):Abstract nr 08.

Simultaneous kinase inhibition with ibrutinib and BCL2 inhibition with venetoclax offers a therapeutic strategy for acute myeloid leukemia

Acute myeloid leukemia (AML) results from the enhanced proliferation and impaired differentiation of hematopoietic stem and progenitor cells. Using an ex vivo functional screening assay, we identified that the combination of the BTK inhibitor ibrutinib and BCL2 inhibitor venetoclax (IBR + VEN), currently in clinical trials for chronic lymphocytic leukemia (CLL), demonstrated enhanced efficacy on primary AML patient specimens, AML cell lines, and in a mouse xenograft model of AML. Expanded analyses among a large cohort of hematologic malignancies (n = 651 patients) revealed that IBR + VEN sensitivity associated with selected genetic and phenotypic features in both CLL and AML specimens. Among AML samples, 11q23 MLL rearrangements were highly sensitive to IBR + VEN. Analysis of differentially expressed genes with respect to IBR + VEN sensitivity indicated pathways preferentially enriched in patient samples with reduced ex vivo sensitivity, including IL-10 signaling. These findings suggest that IBR + VEN may represent an effective therapeutic option for patients with AML.

Contrast-Enhanced Ultrasound to Detect Early Microvascular Changes in Skeletal Muscle after High-Dose Radiation Treatment

The biological response of normal tissue to high-dose radiation treatment remains poorly understood. Alterations to the microenvironment, specifically the microvasculature, have been implicated as a significant contributor to tumoral cytotoxicity. We used contrast-enhanced ultrasound (CEU) perfusion imaging, which is uniquely suited to assess functional status of the microcirculation, to measure microvascular blood flow after high-dose irradiation to normal skeletal muscle tissue in a murine model. Proximal hindlimbs of wild-type C57Bl/6 mice were irradiated with a single fraction using 6 MV photons, 1 cm bolus and a dynamic wedge. Quantitative perfusion CEU imaging of the skeletal muscle was performed at days 1 and 8 postirradiation in three different regions of interest (ROIs): 1. 15 Gy external-beam irradiated leg; 2. 12 Gy irradiated 5 mm proximal area; 3. single ROI in the nonirradiated contralateral (CL) hindlimb. Perfusion imaging was also performed in the hindlimb of nonirradiated mice. CEU time-intensity data were analyzed to measure microvascular blood flow (MBF, also referred to as perfusion), and its parametric components of microvascular flux rate and functional microvascular blood volume (MBV). Plasma measurements of two potent vasoconstrictors, endothelin-1 and angiotensin II, were also performed to assess systemic response. CEU perfusion imaging values for the 12 and 15 Gy irradiated limb regions were pooled. At day 1, MBF in the irradiated limb was significantly lower than in the CL limb (P = 0.016) but quite similar to the nonirradiated mice. At day 8, both limbs of irradiated mice exhibited a trend towards lower MBF than the limbs of nonirradiated mice (28% decrease in mean MBF, P = 0.149 for CL; 39% decrease, P = 0.065 for irradiated limb). Compared to nonirradiated animals, the reduction in perfusion in irradiated limbs at day 8 may have been more influenced by the microvascular flux rate (25% decrease in the mean, P = 0.079) than the MBV (12% decrease in the mean, P = 0.328). Examination of vasoactive compounds revealed that the average plasma concentration for endothelin-1 at day 8 postirradiation was significantly higher in 14 irradiated animals than in 4 nonirradiated animals (3.07 pg/ ml vs. 2.51 pg/ml; P = 0.011). Up to day 8 after high-dose irradiation, flow deficits in irradiated muscle appear to be a consequence of increased vascular resistance more so than loss or functional de-recruitment of microvascular units.

Abstract 1340: High NK cell number predicts poor overall survival in de novo treatment naive acute myeloid leukemia

Introduction Acute myeloid leukemia (AML) is a deadly disease associated with high mortality and morbidity. Previous studies report defects in NK cell maturation and function in AML patients leading to innate immune evasion. Considering that the number of NK cells may be an important indicator of innate immune regulation of AML, our group sought to understand the prognostic significance of NK cell number in de novo AML patients.

Methods Patient samples were obtained from the Oregon Health and Science University (OHSU) Pathology Department between September 2010 and March 2016. This cohort study includes 82 newly diagnosed adult AML patients who had a bone marrow biopsy that was subjected to flow cytometry and a targeted-NGS panel within 30 days prior to induction treatment. Patients were excluded if they had antecedent hematological diseases or therapy-related AML. Bone marrow immunophenotyping was performed using the Ion Torrent PGM platform. Absolute numbers of NK cells were estimated from flow cytometric analysis of the bone marrow samples whereby lymphocytes were identified based on CD45 staining and light side scatter and NK cells were defined as CD3-/CD56+.

Results This retrospective cohort of 82 newly diagnosed AML patients were 53.7% male with a median age of 61 years (range 18 - 83). Using 2017 ELN risk stratification guidelines, 36.6% of patients were classified as favorable, 26.8% as intermediate, and 36.6% as adverse. Absolute NK cell numbers in the bone marrow ranged from 1 to 896 cells/μl with a median of 98. When stratifying NK cells by staining intensity to identify subpopulations, the number of CD56 bright NK cells ranged from 0 to 69 cells/μl (median 3) and the number of CD56 dim NK cells ranged from 1 to 585 cells/μl (median 77). Overall survival (OS) was measured from diagnosis to date of death or last contact and varied from 1 day to 5.7 years (median 20.5 months). There were 3 deaths in the first week after diagnosis. Separate Cox proportional hazards regression models were applied to each NK cell group in both the univariable and multivariable settings, with the latter models accounting for patient age and ELN risk. Higher absolute numbers of NK cells (CD3-/CD56+) were significantly correlated with worse OS in both model settings, with a multivariable p-value of 0.001. The number of bright NK cells was a significant predictor of OS in the univariable model but lost significance when controlling for other variables. However, similar to the number of all NK cells and contrary to previous reports, higher counts of dim NK cells were significantly associated with shorter survival times, with a multivariable p-value of 0.001.

Conclusions In this study, we show that higher NK cell numbers at diagnosis are associated with worse OS and thus play an important role in prognostication for AML patients. This association with survival is most evident in patients at least 60 years old or those with intermediate or adverse ELN risk.

Citation Format: Weiwei Wang, Guang Fan, Andy Kaempf, evan Lind, Tomi Mori, Byung Park, Jennifer Saultz. High NK cell number predicts poor overall survival in de novo treatment naive acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1340.

High T cell percentage predicts improved overall survival in de novo Acute Myeloid Leukemia

Intro

Acute myeloid leukemia (AML) is associated with defects in innate and adaptive immunity leading to immune evasion and leukemia survival. Given the important connection between the immune system and AML, our group sought to understand the prognostic significance of immune subsets in the bone marrow.

Methods

Patient samples were obtained from the Oregon Health and Science University (OHSU) pathology department between September 2010 and March 2016. This cohort study includes 82 newly diagnosed adult AML patients who had a bone marrow biopsy that was subjected to flow cytometry and a targeted-NGS panel.

Results

This retrospective cohort of 82 newly diagnosed AML patients was 53.7% male with a median age of 61 years (range 18 – 83). Using 2017 ELN risk guidelines, 40% of patients were classified as favorable, 24% as intermediate, and 35% as adverse. The percent T cells of lymphocytes ranged from 41.0 to 90.9 (median 72.5). The percent of NK cells ranged from 2.1 to 22.6 (median 8.7). Separate Cox regression models were applied to each immune cell group in both the univariable and multivariable settings, with the latter models accounting for patient age and ELN risk. Higher T cell percentages were correlated with longer survival, even when adjusting for age and ELN risk (p=0.024; HR=0.87 [95% CI: 0.78 – 0.98] for each 5-unit increase). Conversely, in the absence of other patient features, higher NK cell percentages were predictive of worse OS (p=0.015).

Conclusions

In this study, we show that higher T cell percentages at diagnosis are associated with improved OS. This association is most evident in patients at least 60 years old or those with intermediate ELN risk.

Abstract P6-18-26: Ado-trastuzumab for the treatment of metastatic HER2-amplified breast cancer patients previously treated with pertuzumab

BACKGROUND: Ado-trastuzumab (T-DM1) is an antibody-drug conjugate of trastuzumab and a cytotoxic microtubule-inhibitory agent, emtansine. T-DM1 is approved for the treatment of advanced HER2-amplified breast cancer that progressed following trastuzumab-based therapies based on improvement in progression-free survival (PFS) and overall survival (OS) compared to the therapy of physician choice. However, T-DM1 trials were conducted prior to the widespread adoption of docetaxel, trastuzumab, and pertuzumab as standard frontline therapy for advanced HER2-amplified breast cancer. As such, none of the patients enrolled on T-DM1 studies had been exposed to pertuzumab, and the clinical benefit of T-DM1 in patients previously treated with pertuzumab therapy is unknown.

METHODS: We completed a retrospective review of patients at our institution over the age of 18 with metastatic HER2-amplified breast cancer treated with pertuzumab prior to T-DM1 between February 2013 and May 2018. Data was collected on patient and tumor characteristics, number and duration of therapies in the metastatic setting, and clinical outcomes. The primary endpoint of this study was PFS in patients given T-DM1 after earlier exposure to pertuzumab. Secondary endpoints included overall response rate (ORR), prolonged duration of T-DM1 therapy (&gt; 6 months), and OS. Adverse events following T-DM1 were collected using CTCAE 4.03, with a focus on cardiac dysfunction and peripheral neuropathy. Patient features and outcomes were summarized with descriptive statistics and time-to-event measures were analyzed using the Kaplan-Meier method and log-rank test.

RESULTS: Twenty patients met the inclusion criteria and are included in this study. The patient population consisted of 18 non-Hispanic white and 2 black women, with a median age of 58.5 (range 34-68) years. The number of prior systemic therapies (excluding pertuzumab) ranged from 0-8 with a median of 1 therapy. The duration of T-DM1 therapy (started, on average, 24 months after metastatic diagnosis) ranged from &lt; 1 month to 3.5 years with a median of 6 months. T-DM1 therapy was overall very well tolerated, with all adverse events being grade ≤2. Of note, 2 patients had grade 2 neuropathy, and one patient had grade 1 cardiotoxicity, without any change in left ventricular ejection.

Among 18 patients evaluable for response, ORR was 16.7% (95% CI: 3.6% to 41.4%), with 3 patients achieving a partial response. No complete responses were noted. 10/18 (55.6%) patients had prolonged duration of therapy with T-DM1. Median follow-up time after initiation of T-DM1 was 15 months and 6/20 (30%) patients died while under observation. At the time of data cut-off, 10/20 patients had disease progression on T-DM1. Median PFS was 16 months, with a 1-year PFS rate of 54.5% (95% CI: 36.4% to 81.7%). The 1-year OS rate was 75.0% (95% CI: 58.2% to 96.6%). Patients with liver metastases (n=8) had a significantly worse PFS (p=0.003).

CONCLUSION: T-DM1 following pertuzumab is well tolerated and shows excellent efficacy in the treatment of HER2-positive metastatic breast cancer. Comparing T-DM1 following pertuzumab to T-DM1 in pertuzumab-naïve patients should be explored in this patient population.

Citation Format: Al Rabadi LS, Kaempf A, Lim JY, Saraceni MM, Savin MA, Mitri ZI. Ado-trastuzumab for the treatment of metastatic HER2-amplified breast cancer patients previously treated with pertuzumab [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 P6-18-26.

CSF1R inhibitors exhibit antitumor activity in acute myeloid leukemia by blocking paracrine signals from support cells

To identify new therapeutic targets in acute myeloid leukemia (AML), we performed small-molecule and small-interfering RNA (siRNA) screens of primary AML patient samples. In 23% of samples, we found sensitivity to inhibition of colony-stimulating factor 1 (CSF1) receptor (CSF1R), a receptor tyrosine kinase responsible for survival, proliferation, and differentiation of myeloid-lineage cells. Sensitivity to CSF1R inhibitor GW-2580 was found preferentially in de novo and favorable-risk patients, and resistance to GW-2580 was associated with reduced overall survival. Using flow cytometry, we discovered that CSF1R is not expressed on the majority of leukemic blasts but instead on a subpopulation of supportive cells. Comparison of CSF1R-expressing cells in AML vs healthy donors by mass cytometry revealed expression of unique cell-surface markers. The quantity of CSF1R-expressing cells correlated with GW-2580 sensitivity. Exposure of primary AML patient samples to a panel of recombinant cytokines revealed that CSF1R inhibitor sensitivity correlated with a growth response to CSF1R ligand, CSF1, and other cytokines, including hepatocyte growth factor (HGF). The addition of CSF1 increased the secretion of HGF and other cytokines in conditioned media from AML patient samples, whereas adding GW-2580 reduced their secretion. In untreated cells, HGF levels correlated significantly with GW-2580 sensitivity. Finally, recombinant HGF and HS-5-conditioned media rescued cell viability after GW-2580 treatment in AML patient samples. Our results suggest that CSF1R-expressing cells support the bulk leukemia population through the secretion of HGF and other cytokines. This study identifies CSF1R as a novel therapeutic target of AML and provides a mechanism of paracrine cytokine/growth factor signaling in this disease.

IFNγ-activated dermal lymphatic vessels inhibit cytotoxic T cells in melanoma and inflamed skin

Mechanisms of immune suppression in peripheral tissues counteract protective immunity to prevent immunopathology and are coopted by tumors for immune evasion. While lymphatic vessels facilitate T cell priming, they also exert immune suppressive effects in lymph nodes at steady-state. Therefore, we hypothesized that peripheral lymphatic vessels acquire suppressive mechanisms to limit local effector CD8+ T cell accumulation in murine skin. We demonstrate that nonhematopoietic PD-L1 is largely expressed by lymphatic and blood endothelial cells and limits CD8+ T cell accumulation in tumor microenvironments. IFNγ produced by tissue-infiltrating, antigen-specific CD8+ T cells, which are in close proximity to tumor-associated lymphatic vessels, is sufficient to induce lymphatic vessel PD-L1 expression. Disruption of IFNγ-dependent crosstalk through lymphatic-specific loss of IFNγR boosts T cell accumulation in infected and malignant skin leading to increased viral pathology and tumor control, respectively. Consequently, we identify IFNγR as an immunological switch in lymphatic vessels that balances protective immunity and immunopathology leading to adaptive immune resistance in melanoma.

Functional genomic landscape of acute myeloid leukaemia

The implementation of targeted therapies for acute myeloid leukaemia (AML) has been challenging because of the complex mutational patterns within and across patients as well as a dearth of pharmacologic agents for most mutational events. Here we report initial findings from the Beat AML programme on a cohort of 672 tumour specimens collected from 562 patients. We assessed these specimens using whole-exome sequencing, RNA sequencing and analyses of ex vivo drug sensitivity. Our data reveal mutational events that have not previously been detected in AML. We show that the response to drugs is associated with mutational status, including instances of drug sensitivity that are specific to combinatorial mutational events. Integration with RNA sequencing also revealed gene expression signatures, which predict a role for specific gene networks in the drug response. Collectively, we have generated a dataset-accessible through the Beat AML data viewer (Vizome)-that can be leveraged to address clinical, genomic, transcriptomic and functional analyses of the biology of AML.