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Genetic mutations associated with acute myeloid leukemia (AML) also occur in age-related clonal hematopoiesis, often in the same individual. This makes confident assignment of detected variants to malignancy challenging. The issue is particularly crucial for AML posttreatment measurable residual disease monitoring, where results can be discordant between genetic sequencing and flow cytometry. We show here that it is possible to distinguish AML from clonal hematopoiesis and to resolve the immunophenotypic identity of clonal architecture. To achieve this, we first design patient-specific DNA probes based on patient's whole-genome sequencing and then use them for patient-personalized single-cell DNA sequencing with simultaneous single-cell antibody–oligonucleotide sequencing. Examples illustrate AML arising from DNMT3A- and TET2-mutated clones as well as independently. The ability to personalize single-cell proteogenomic assessment for individual patients based on leukemia-specific genomic features has implications for ongoing AML precision medicine efforts.Significance:This study offers a proof of principle of patient-personalized customized single-cell proteogenomics in AML including whole-genome sequencing–defined structural variants, currently unmeasurable by commercial “off-the-shelf” panels. This approach allows for the definition of genetic and immunophenotype features for an individual patient that would be best suited for measurable residual disease tracking.

Supplementary Data

Supplementary Table 1. Characteristics of all patients studied.

Purpose: Clinical trials of ibrutinib combined with anti-CD20 monoclonal antibodies (mAb) for chronic lymphocytic leukemia (CLL) report encouraging results. Paradoxically, in preclinical studies, in vitro ibrutinib was reported to decrease CD20 expression and inhibit cellular effector mechanisms. We therefore set out to investigate effects of in vivo ibrutinib treatment that could explain this paradox.Experimental Design: Patients received single-agent ibrutinib (420 mg daily) on an investigator-initiated phase II trial. Serial blood samples were collected pretreatment and during treatment for ex vivo functional assays to examine the effects on CLL cell susceptibility to anti-CD20 mAbs.Results: We demonstrate that CD20 expression on ibrutinib was rapidly and persistently downregulated (median reduction 74%, day 28, P < 0.001) compared with baseline. Concomitantly, CD20 mRNA was decreased concurrent with reduced NF-κB signaling. An NF-κB binding site in the promoter of MS4A1 (encoding CD20) and downregulation of CD20 by NF-κB inhibitors support a direct transcriptional effect. Ex vivo, tumor cells from patients on ibrutinib were less susceptible to anti-CD20 mAb-mediated complement-dependent cytotoxicity than pretreatment cells (median reduction 75%, P < 0.001); however, opsonization by the complement protein C3d, which targets cells for phagocytosis, was relatively maintained. Expression of decay-accelerating factor (CD55) decreased on ibrutinib, providing a likely mechanism for the preserved C3d opsonization. In addition, ibrutinib significantly inhibited trogocytosis, a major contributor to antigen loss and tumor escape during mAb therapy.Conclusions: Our data indicate that ibrutinib promotes both positive and negative interactions with anti-CD20 mAbs, suggesting that successfully harnessing maximal antitumor effects of such combinations requires further investigation. Clin Cancer Res; 22(1); 86–95. ©2015 AACR.

Supplementary Figure 1. Uniform CD20 loss from the surface of primary CLL cells after in vivo exposure to ibrutinib. Supplementary Figure 2. Loss of CD20 on ibrutinib and basal CD20 expression levels do not correlate with high risk prognostic factors. Supplementary Figure 3. Selective NF-κB inhibitor diminishes CD20 cell surface expression. Supplementary Figure 4. Complement regulatory proteins membrane cofactor protein and protectin are not consistently inhibited by ibrutinib.

Supplementary Figure S1. Ibrutinib alters the absolute expression of inflammatory cytokines and chemokines in serum from patients with CLL. Supplementary Figure S2. Ibrutinib treatment reduces tumor burden. Supplementary Figure S3. Both CD4+ and CD8+ T cell subsets are decreased on ibrutinib. Supplementary Figure S4. Grading of macrophage interaction with CLL cells in bone marrow specimens. Supplementary Figure S5. Ibrutinib alters the absolute expression of chemokines in bone marrow supernatant from patients with CLL.

Purpose: Chronic lymphocytic leukemia (CLL) cells depend on microenvironmental interactions for proliferation and survival that are at least partially mediated through B-cell receptor (BCR) signaling. Ibrutinib, a Bruton tyrosine kinase inhibitor, disrupts BCR signaling and leads to the egress of tumor cells from the microenvironment. Although the on-target effects on CLL cells are well defined, the impact on the microenvironment is less well studied. We therefore sought to characterize the in vivo effects of ibrutinib on the tumor microenvironment.Experimental Design: Patients received single-agent ibrutinib on an investigator-initiated phase II trial. Serial blood and tissue samples were collected pretreatment and during treatment. Changes in cytokine levels, cellular subsets, and microenvironmental interactions were assessed.Results: Serum levels of key chemokines and inflammatory cytokines decreased significantly in patients on ibrutinib. Furthermore, ibrutinib treatment decreased circulating tumor cells and overall T-cell numbers. Most notably, a reduced frequency of the Th17 subset of CD4+ T cells was observed concurrent with reduced expression of activation markers and PD-1 on T cells. Consistent with direct inhibition of T cells, ibrutinib inhibited Th17 differentiation of murine CD4+ T cells in vitro. Finally, in the bone marrow microenvironment, we found that ibrutinib disaggregated the interactions of macrophages and CLL cells, inhibited secretion of CXCL13, and decreased the chemoattraction of CLL cells.Conclusions: In conjunction with inhibition of BCR signaling, these changes in the tumor microenvironment likely contribute to the antitumor activity of ibrutinib and may impact the efficacy of immunotherapeutic strategies in patients with CLL. Clin Cancer Res; 22(7); 1572–82. ©2015 AACR.See related commentary by Bachireddy and Wu, p. 1547

Supplementary Table S1: Evaluation of serum cytokine levels on ibrutinib Supplementary Table S2: Evaluation of chemoattractant levels in bone marrow supernatant on ibrutinib supplementary figure legends for supplementary figures S1-S5

Conflict of Interest Form from Disruption of in vivo Chronic Lymphocytic Leukemia Tumor–Microenvironment Interactions by Ibrutinib – Findings from an Investigator-Initiated Phase II Study

Supplementary Figures Legends from Interactions between Ibrutinib and Anti-CD20 Antibodies: Competing Effects on the Outcome of Combination Therapy

Genetic mutations associated with acute myeloid leukemia (AML) also occur in age-related clonal hematopoiesis, often in the same individual. This makes confident assignment of detected variants to malignancy challenging. The issue is particularly crucial for AML posttreatment measurable residual disease monitoring, where results can be discordant between genetic sequencing and flow cytometry. We show here that it is possible to distinguish AML from clonal hematopoiesis and to resolve the immunophenotypic identity of clonal architecture. To achieve this, we first design patient-specific DNA probes based on patient's whole-genome sequencing and then use them for patient-personalized single-cell DNA sequencing with simultaneous single-cell antibody–oligonucleotide sequencing. Examples illustrate AML arising from DNMT3A- and TET2-mutated clones as well as independently. The ability to personalize single-cell proteogenomic assessment for individual patients based on leukemia-specific genomic features has implications for ongoing AML precision medicine efforts. Significance: This study offers a proof of principle of patient-personalized customized single-cell proteogenomics in AML including whole-genome sequencing–defined structural variants, currently unmeasurable by commercial “off-the-shelf” panels. This approach allows for the definition of genetic and immunophenotype features for an individual patient that would be best suited for measurable residual disease tracking.

There is no standard or widely effective treatment of patients with moderate aplastic anemia (MAA) or hypo-productive uni-lineage cytopenias (UC). Eltrombopag (EPAG), a small molecule thrombopoietin mimetic, has previously been shown to result in durable multi-lineage hematologic responses with low toxicity in patients with refractory severe aplastic anemia (SAA). Its safety and efficacy in MAA are unknown. This prospective phase 2 study enrolled previously untreated and treated MAA and UC patients with clinically relevant cytopenias. EPAG was administered at doses escalating from 50 to 300 mg/d. Hematologic responses were assessed at 16 to 20 weeks. Responding patients were continued on EPAG until reaching defined robust or stable blood counts. EPAG was reinstituted for relapse. Thirty-four patients were enrolled between 2012 and 2017, including 31 with MAA and 3 with UC. Seventeen patients responded in at least 1 eligible lineage by the primary end point. A striking improvement in anemia was observed in a patient with Diamond-Blackfan anemia. EPAG was well tolerated, and it was discontinued for robust or stable blood counts in 12 of 17 patients after a median of 8 months. A majority required re-initiation of EPAG for declining counts, and all regained response. Two of 34 patients developed non–chromosome 7 bone marrow cytogenetic abnormalities while taking EPAG, without dysplasia or increased blasts. Somatic mutation allele frequencies in cancer genes did not increase overall on EPAG. EPAG is a well-tolerated oral treatment of cytopenias in patients with MAA/UC. This trial was registered at www.clinicaltrials.gov as #NCT01328587.

Acute myeloid leukemia (AML) is a genetically heterogeneous disease that is characterized by abnormal clonal proliferation of myeloid progenitor cells found predominantly within the bone marrow (BM) and blood. Recent studies suggest that genetic and phenotypic alterations in the BM microenvironment support leukemogenesis and allow leukemic cells to survive and evade chemotherapy-induced death. However, despite substantial evidence indicating the role of tumor–host interactions in AML pathogenesis, little is known about the complex microenvironment of the BM. To address this, we performed novel proteomic profiling of the noncellular compartment of the BM microenvironment in patients with AML (n = 10) and age- and sex-matched healthy control subjects (n = 10) using an aptamer-based, highly multiplexed, affinity proteomics platform (SOMAscan). We show that proteomic assessment of blood or RNA-sequencing of BM are suboptimal alternate screening strategies to determine the true proteomic composition of the extracellular soluble compartment of AML patient BM. Proteomic analysis revealed that 168 proteins significantly differed in abundance, with 91 upregulated and 77 downregulated in leukemic BM. A highly connected signaling network of cytokines and chemokines, including IL-8, was found to be the most prominent proteomic signature associated with AML in the BM microenvironment. We report the first description of significantly elevated levels of the myelosuppressive chemokine CCL23 (myeloid progenitor inhibitory factor-1) in both AML and myelodysplastic syndrome patients and perform functional experiments supportive of a role in the suppression of normal hematopoiesis. This unique paired RNA-sequencing and proteomics data set provides innovative mechanistic insights into AML and healthy aging and should serve as a useful public resource.

Background Coronavirus disease 2019 (COVID-19) requiring hospitalization is characterized by robust antibody production, dysregulated immune response, and immunothrombosis. Fostamatinib is a novel spleen tyrosine kinase inhibitor that we hypothesize will ameliorate Fc activation and attenuate harmful effects of the anti-COVID-19 immune response. Methods We conducted a double-blind, randomized, placebo-controlled trial in hospitalized adults requiring oxygen with COVID-19 where patients receiving standard of care were randomized to receive fostamatinib or placebo. The primary outcome was serious adverse events by day 29. Results A total of 59 patients underwent randomization (30 to fostamatinib and 29 to placebo). Serious adverse events occurred in 10.5% of patients in the fostamatinib group compared with 22% in placebo (P = .2). Three deaths occurred by day 29, all receiving placebo. The mean change in ordinal score at day 15 was greater in the fostamatinib group (-3.6 ± 0.3 vs -2.6 ± 0.4, P = .035) and the median length in the intensive care unit was 3 days in the fostamatinib group vs 7 days in placebo (P = .07). Differences in clinical improvement were most evident in patients with severe or critical disease (median days on oxygen, 10 vs 28, P = .027). There were trends toward more rapid reductions in C-reactive protein, D-dimer, fibrinogen, and ferritin levels in the fostamatinib group. Conclusion For COVID-19 requiring hospitalization, the addition of fostamatinib to standard of care was safe and patients were observed to have improved clinical outcomes compared with placebo. These results warrant further validation in larger confirmatory trials. Clinical Trials Registration Clinicaltrials.gov, NCT04579393.

High-risk cytogenetics and minimal residual disease (MRD) after chemoimmunotherapy (CIT) predict unfavorable outcome in chronic lymphocytic leukemia (CLL). This phase 2 study investigated risk-adapted CIT in treatment-naïve CLL (NCT01145209). Patients with high-risk cytogenetics received induction with fludarabine, cyclophosphamide, and ofatumumab. Those without high-risk cytogenetics received fludarabine and ofatumumab. After induction, MRD positive (MRD+) patients received 4 doses of ofatumumab consolidation. MRD negative (MRD−) patients had no intervention. Of 28 evaluable for response, all responded to induction and 10 (36%) achieved MRD−. Two-year progression-free survival (PFS) was 71.4% (CI(95), 56.5–90.3%). There was no significant difference in median PFS between high-risk and standard-risk group. Ofatumumab consolidation didn’t convert MRD+ to MRD−. In MRD+ group, we saw selective loss of CD20 antigens during therapy. In conclusion, risk-adapted CIT is feasible in treatment-naïve CLL. Ofatumumab consolidation didn’t improve depth of response in MRD+ patients. Loss of targetable CD20 likely reduces efficacy of consolidation therapy.

Genetic mutations associated with acute myeloid leukemia can also be detected in age-related clonal hematopoiesis, making confident assignment of detected variants to malignancy challenging particularly in the post-treatment setting. This has implications for measurable residual disease monitoring, where the relationship between sequencing and flow cytometry is also imperfect. We show, using whole-genome-sequencing informed patient-personalized single-cell DNA and antibody-oligonucleotide sequencing, that it is possible to resolve immunophenotypic identity of clonal architecture.

Immune dysregulation in chronic lymphocytic leukemia (CLL) contributes to a high rate of infections and morbidity. The Bruton tyrosine kinase (BTK) inhibitors ibrutinib and acalabrutinib mark major breakthroughs in the treatment of CLL, however many patients require long-term therapy with these agents. Despite receiving effective therapy for CLL, patients on BTK inhibitors remain immunocompromised and at risk of infectious complications. We previously reported that treatment of CLL with ibrutinib leads to partial reconstitution of humoral immunity and fewer infections during the first two years of therapy. It is currently unclear whether the positive effects of ibrutinib on the immune system are sustained during long-term therapy. Acalabrutinib is a newer, more selective BTK inhibitor than ibrutinib; however a detailed evaluation of the immunologic impact of acalabrutinib therapy is lacking. Herein, utilizing two independent trials, we assessed the immunological effects and infectious risk of ibrutinib and acalabrutinib treatment in patients with CLL.

The powerful “graft versus leukemia” effect thought partly responsible for the therapeutic effect of allogeneic hematopoietic cell transplantation in acute myeloid leukemia (AML) provides rationale for investigation of immune-based therapies in this high-risk blood cancer. There is considerable pre-clinical evidence for potential synergy between PD-1 immune checkpoint blockade and the hypomethylating agents already commonly used for this disease. We report here the results of 17-H-0026 (PD-AML, NCT02996474), an investigator sponsored, single-institution, single-arm open-label ten-subject pilot study to test the feasibility of the first-in-human combination of pembrolizumab and decitabine in adult patients with refractory or relapsed AML (R-AML). In this cohort of previously treated patients, this novel combination of anti-PD-1 and hypomethylating therapy was feasible and associated with a best response of stable disease or better in 6 of 10 patients. Considerable immunological changes were identified using TCRβ sequencing as well as single-cell immunophenotypic and RNA expression analyses on sorted CD3+ T cells in patients who developed immune-related adverse events (irAEs) during treatment. Clonal T cell expansions occurred at irAE onset; single-cell sequencing demonstrated that these expanded clones were predominately CD8+ effector memory T cells with high cell surface PD-1 expression and transcriptional profiles indicative of activation and cytotoxicity. In contrast, no such distinctive immune changes were detectable in those experiencing a measurable anti-leukemic response during treatment. Addition of pembrolizumab to ten-day decitabine therapy was clinically feasible in patients with R-AML, with immunological changes from PD-1 blockade observed in patients experiencing irAEs.One Sentence SummaryAML patients receiving a novel combination of a PD-1 immune checkpoint inhibitor with a hypomethylating agent demonstrated clear evidence of induced immunological responses in those developing autoimmune toxicity during treatment but not in those demonstrating an anti-leukemic response.

Chronic lymphocytic leukemia (CLL) is a progressive malignancy of mature B-cells that involves the peripheral blood (PB), lymph nodes (LNs) and bone marrow (BM). Although the majority of CLL cells are in a resting state, small populations of proliferating cells exist; however, the anatomical site of active cell proliferation remains to be definitively determined. Based on findings that CLL cells in LNs have increased expression of B-cell activation genes, we tested the hypothesis that the fraction of 'newly born' cells would be highest in the LNs. Using a deuterium oxide (2H) in vivo labeling method in which patients consumed deuterated (heavy) water (2H2O), we determined CLL cell kinetics in concurrently obtained samples from LN, PB and BM. The LN was identified as the anatomical site harboring the largest fraction of newly born cells, compared to PB and BM. In fact, the calculated birth rate in the LN reached as high a 3.3% of the clone per day. Subdivision of the bulk CLL population by flow cytometry identified the subpopulation with the CXCR4dimCD5bright phenotype as containing the highest proportion of newly born cells within each compartment, including the LN, identifying this subclonal population as an important target for novel treatment approaches.

Purpose: Chronic lymphocytic leukemia (CLL) cells depend on microenvironmental interactions for proliferation and survival that are at least partially mediated through B-cell receptor (BCR) signaling. Ibrutinib, a Bruton tyrosine kinase inhibitor, disrupts BCR signaling and leads to the egress of tumor cells from the microenvironment. Although the on-target effects on CLL cells are well defined, the impact on the microenvironment is less well studied. We therefore sought to characterize the in vivo effects of ibrutinib on the tumor microenvironment. Experimental Design: Patients received single-agent ibrutinib on an investigator-initiated phase II trial. Serial blood and tissue samples were collected pretreatment and during treatment. Changes in cytokine levels, cellular subsets, and microenvironmental interactions were assessed. Results: Serum levels of key chemokines and inflammatory cytokines decreased significantly in patients on ibrutinib. Furthermore, ibrutinib treatment decreased circulating tumor cells and overall T-cell numbers. Most notably, a reduced frequency of the Th17 subset of CD4+ T cells was observed concurrent with reduced expression of activation markers and PD-1 on T cells. Consistent with direct inhibition of T cells, ibrutinib inhibited Th17 differentiation of murine CD4+ T cells in vitro. Finally, in the bone marrow microenvironment, we found that ibrutinib disaggregated the interactions of macrophages and CLL cells, inhibited secretion of CXCL13, and decreased the chemoattraction of CLL cells. Conclusions: In conjunction with inhibition of BCR signaling, these changes in the tumor microenvironment likely contribute to the antitumor activity of ibrutinib and may impact the efficacy of immunotherapeutic strategies in patients with CLL. Clin Cancer Res; 22(7); 1572–82. ©2015 AACR. See related commentary by Bachireddy and Wu, p. 1547

Eltrombopag (EPAG) received approval from the US Food and Drug Administration for the treatment of refractory severe aplastic anemia (rSAA) based on treatment of 43 patients with doses escalating from 50 to 150 mg daily for 12 weeks. Response kinetics suggested that more prolonged administration of EPAG at a dose of 150 mg could speed and improve response rates. We enrolled 40 patients with rSAA in a study of EPAG 150 mg daily, with a primary end point of response at 24 weeks. Twenty (50%) of 40 patients responded at 24 weeks; 5 (25%) of 20 would have been deemed nonresponders at 12 weeks, the end point of the previous study. Fifteen of the 19 responding patients continuing on EPAG had drug discontinued for robust response; 5 of the 15 required EPAG re-initiation for relapse, with all recovering response. To analyze risk of clonal progression, we combined long-term data from the 83 patients with rSAA enrolled in both studies. Evolution to an abnormal karyotype occurred in 16 (19%), most within 6 months of EPAG initiation. Targeted deep sequencing/whole-exome sequencing was performed pre-EPAG and at primary response end point and/or time of clonal evolution or longest follow-up. Cytogenetic evolution did not correlate with mutational status, and overall mutated allele fractions of myeloid cancer genes did not increase on EPAG. In summary, extended administration of EPAG at a dose of 150 mg for 24 weeks rescued responses in some patients with rSAA not responding at 12 weeks. The temporal relationship between clonal evolution and drug exposure suggests that EPAG may promote expansion of dormant preexisting clones with an aberrant karyotype. The studies were registered at www.clinicaltrials.gov as #NCT00922883 and #NCT01891994.

Immune stimulation contributes to lenalidomide’s antitumor activity. Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of mature, autoreactive B cells in secondary lymphoid tissues, blood, and bone marrow and progressive immune dysfunction. Previous studies in CLL indicated that lenalidomide can repair defective T cell function in vitro. Whether T cell activation is required for clinical response to lenalidomide remains unclear. In this study, we report changes in the immune microenvironment in patients with CLL treated with single-agent lenalidomide and associate the immunologic effects of lenalidomide with antitumor response. Within days of starting lenalidomide, T cells increased in the tumor microenvironment and showed Th1-type polarization. Gene expression profiling of pretreatment and on-treatment lymph node biopsy specimens revealed upregulation of IFN-γ and many of its target genes in response to lenalidomide. The IFN-γ–mediated Th1 response was limited to patients achieving a clinical response defined by a reduction in lymphadenopathy. Deep sequencing of TCR genes revealed decreasing diversity of the T cell repertoire and an expansion of select clonotypes in responders. To validate our observations, we stimulated T cells and CLL cells with lenalidomide in culture and detected lenalidomide-dependent increases in T cell proliferation. Taken together, our data demonstrate that lenalidomide induced Th1 immunity in the lymph node that is associated with clinical response.

The safety and efficacy of ibrutinib (420 mg) in chronic lymphocytic leukemia (CLL) were evaluated in a phase 2 study; 51 patients had TP53 aberration (TP53 cohort) and 35 were enrolled because of age 65 years or older (elderly cohort). Both cohorts included patients with treatment-naive (TN) and relapsed/refractory (RR) CLL. With the median follow-up of 4.8 years, 49 (57.0%) of 86 patients remain on study. Treatment was discontinued for progressive disease in 20 (23.3%) patients and for adverse events in 5 (5.8%). Atrial fibrillation occurred in 18 (20.9%) patients for a rate of 6.4 per 100 patient-years. No serious bleeding occurred. The overall response rate at 6 months, the primary study endpoint, was 95.8% for the TP53 cohort (95% confidence interval, 85.7%-99.5%) and 93.9% for the elderly cohort (95% confidence interval, 79.8%-99.3%). Depth of response improved with time: at best response, 14 (29.2%) of 48 patients in the TP53 cohort and 9 (27.3%) of 33 in the elderly cohort achieved a complete response. Median minimal residual disease (MRD) in peripheral blood was 3.8 × 10-2 at 4 years, with MRD-negative (

Acquired aplastic anemia results from immune-mediated destruction of bone marrow. Immunosuppressive therapies are effective, but reduced numbers of residual stem cells may limit their efficacy. In patients with aplastic anemia that was refractory to immunosuppression, eltrombopag, a synthetic thrombopoietin-receptor agonist, led to clinically significant increases in blood counts in almost half the patients. We combined standard immunosuppressive therapy with eltrombopag in previously untreated patients with severe aplastic anemia.We enrolled 92 consecutive patients in a prospective phase 1-2 study of immunosuppressive therapy plus eltrombopag. The three consecutively enrolled cohorts differed with regard to the timing of initiation and the duration of the eltrombopag regimen (cohort 1 received eltrombopag from day 14 to 6 months, cohort 2 from day 14 to 3 months, and cohort 3 from day 1 to 6 months). The cohorts were analyzed separately. The primary outcome was complete hematologic response at 6 months. Secondary end points included overall response, survival, relapse, and clonal evolution to myeloid cancer.The rate of complete response at 6 months was 33% in cohort 1, 26% in cohort 2, and 58% in cohort 3. The overall response rates at 6 months were 80%, 87%, and 94%, respectively. The complete and overall response rates in the combined cohorts were higher than in our historical cohort, in which the rate of complete response was 10% and the overall response rate was 66%. At a median follow-up of 2 years, the survival rate was 97%; one patient died during the study from a nonhematologic cause. Marked increases in bone marrow cellularity, CD34+ cell number, and frequency of early hematopoietic progenitors were noted. Rates of relapse and clonal evolution were similar to our historical experience. Severe rashes occurred in two patients, resulting in the early discontinuation of eltrombopag.The addition of eltrombopag to immunosuppressive therapy was associated with markedly higher rates of hematologic response among patients with severe aplastic anemia than in a historical cohort. (Funded by the National Heart, Lung, and Blood Institute; ClinicalTrials.gov number, NCT01623167 .).

Ibrutinib and other targeted inhibitors of B-cell receptor signaling achieve impressive clinical results for patients with chronic lymphocytic leukemia (CLL). A treatment-induced rise in absolute lymphocyte count (ALC) has emerged as a class effect of kinase inhibitors in CLL and warrants further investigation. We here report correlative studies in 64 patients with CLL treated with ibrutinib. We quantified tumor burden in blood, lymph nodes, spleen, and bone marrow, assessed phenotypic changes of circulating cells, and measured whole blood viscosity. With just one dose of ibrutinib the average increase in ALC was 66%, and in over 40% of patients the ALC peaked within 24 hours of initiating treatment. Circulating CLL cells on day 2 showed increased Ki67 and CD38 expression, indicating an efflux of tumor cells from the tissue compartments into the blood. The kinetics and degree of the treatment-induced lymphocytosis was highly variable; interestingly in patients with a high baseline ALC the relative increase was mild and resolution rapid. After two cycles of treatment the disease burden in lymph node, bone marrow, and spleen decreased irrespective of the relative change in ALC. Whole blood viscosity was dependent on both ALC and hemoglobin. No adverse events were attributed to the lymphocytosis.

Introduction Immune dysregulation is a hallmark of CLL, making these patients particularly vulnerable to infectious complications. Patients with CLL are at increased risk of developing varicella zoster virus (VZV) reactivation (shingles) due to their advanced age and immunocompromised status. A new recombinant (non-live) adjuvanted shingles vaccine (SHINGRIX; RZV) has the potential to reduce VZV reactivation, without the risk of giving a live vaccine to immunocompromised individuals. RZV is proven to reduce the risks of herpes zoster and postherpetic neuralgia in healthy adults ≥ 50 years of age, however its efficacy in immunocompromised individuals, including CLL, remains unknown. We report preliminary safety and efficacy of RZV in treated and untreated CLL patients. Methods In this phase II open-label study (NCT03702231), patients with CLL who were either treatment naïve or receiving treatment with a Bruton's tyrosine kinase inhibitor (BTK-I) (ibrutinib or acalabrutinib) received 2 doses of RZV via intramuscular injection at 0- and 3-months. Subjects were followed for 6 months and received assessment of serologic response at 3- and 6-months. Based on results of prior published studies, serologic response was defined as a ≥ four-fold rise in VZV anti-glycoprotein E (anti-gE) blood IgG serum titer after completing the RZV vaccine series. Additionally, serologic response was analyzed 3 months following the first vaccine administration to study the kinetics of the humoral vaccine response. All subjects completed an adverse event (AE) diary documenting any local (injection site) or systemic AE that started within 7 days after receiving the first and second vaccine dose. The data reported herein are as of July 12th 2019; updated results will be presented at the meeting. Results Safety data are available on 57 subjects who received at least one vaccine dose. The most frequent local and systemic AEs were injection site pain (67%), injection site reaction (32%) and generalized myalgias (25%) (Table 1). All adverse reactions were grade 1-2, except for 2 (4%) grade 3 reactions. No serious AEs were reported. All AEs resolved or returned to baseline within 7 days of vaccine administration. Seven subjects have completed the primary endpoint and have had serologic response assessment at 6-months. Serologic responses were observed in 3 (43%) patients. All patients (n = 7) achieved ≥ 2.2-fold rise in VZV anti-gE titers at 6-months. Preliminary analysis of 3-month samples (n = 43) shows early evidence of increasing titers after the first dose of RZV. Conclusions RZV administration appears to be safe in CLL patients that are treatment naïve or receiving treatment with a BTK-I. Compared to previously reported toxicities in the healthy population, no increase in frequency or severity of AEs were observed. Preliminary data suggests that RZV induces humoral immune responses in patients with CLL. Disclosures Wiestner: Pharmayclics: Research Funding; Acerta: Research Funding; Merck: Research Funding; Nurix: Research Funding.

The bone marrow (BM) microenvironment is increasingly recognized as an important contributor to acute myeloid leukemia (AML) pathogenesis. However, despite growing interest in characterizing different components and cellular architecture of the BM niche and their biological significance in leukemogenesis, the proteomic constitution of the BM extracellular compartment that distinguishes a leukemic niche from its normal counterpart has not yet been fully described. We therefore performed a quantitative, large-scale proteomic analysis of 1,305 human proteins of the non-cellular compartment of BM (plasma) samples from ten relapsed or refractory AML patients and from ten age- and sex-matched healthy donors (HDs) using an aptamer-based, highly multiplexed, affinity proteomics platform (SOMAscan). This screen identified a total of 168 differentially abundant proteins, of which 91 were significantly more and 77 proteins significantly less abundant in leukemic BM compared with healthy marrow (FC ≥ 1.5, FDR ≤ 0.05). Comparative analysis of BM plasma and peripheral blood (PB) serum samples from the same AML patients and HDs revealed 65 similarly regulated proteins (37 up-regulated vs. 28 down-regulated) and 1 differently regulated protein between the two compartments. Out of the total 168 proteins, 102 proteins were specifically dysregulated only in the BM compartment. TruSeq Stranded Total RNA-sequencing (Illumina) was also performed using paired-end 75bp sequencing on a HiSeq 3000. RNA was isolated from PAXgene BM RNA tubes (Qiagen) collected in parallel with samples for proteomic analysis. Results of analysis of differentially expressed transcripts only partially overlapped with those candidates identified from our validated proteomic approach, indicating that sequencing of RNA derived from cellular sources of BM may be a suboptimal screening strategy to determine the true proteomic composition of the extracellular compartment of the AML marrow microenvironment. In addition to several previously reported proteins, our proteomics screen discovered numerous aberrantly expressed proteins in leukemic marrow whose role in AML pathogenesis is currently unknown. Using pathway analysis, we identified sets of proteins enriched for specific biological pathways including RAS, ephrin, PDGF, PI3K/AKT, MAPK, Notch, TLR, JAK-STAT, NFκB, Rap1, and Tie2 signaling pathways. A systems biology analysis approach revealed the highly connected network of cytokines and chemokines as the most striking AML-associated proteomic alteration in the BM. We identified IL-8 as a differentially expressed and key central molecule of this network in AML, consistent with recent reports. Importantly, we also identified significantly elevated levels of CKβ8 and CKβ8-1, alternatively spliced isoforms of the myelosuppressive chemokine CCL23 also known as myeloid progenitor inhibitory factor 1 (MPIF-1) or CKβ8, in both leukemic marrow and PB serum samples (Figure 1). Given the critical importance of cytopenias, often disproportional to the degree of leukemic marrow involvement, in the morbidity and mortality of patients with myelodysplastic syndrome (MDS) and AML, we subsequently confirmed this striking finding by performing orthogonal validation in a larger cohort of MDS and AML patients using an ELISA-based immunoassay. This novel finding suggests the possibility that CCL23 may play a role in suppression of normal hematopoiesis in MDS and AML. In support of this hypothesis, we demonstrated in vitro myelosuppressive effects of CCL23 isoforms on colony formation by human CD34+ hematopoietic stem and progenitor cells (HSPCs) in an in vitro colony forming unit assay, resulting in an approximately 2.5-fold decrease in CFU-GM and an evident decrease in CFU-GEMM counts. In summary, our broad and quantitative proteomic dataset of extracellular factors present in leukemic and normal aging bone marrow has already provided novel mechanistic insights into AML pathogenesis and should serve, together with paired RNA-sequencing information, as a useful public resource for the research community. Disclosures Lai: Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Speakers Bureau; Astellas: Speakers Bureau; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees. Hourigan:SELLAS Life Sciences Group AG: Research Funding; Merck, Sharpe & Dohme: Research Funding.

Introduction: Anti-CD20 monoclonal antibodies (mAb) are an essential component of CLL therapy. Addition of anti-CD20 mAb to induction chemotherapy improves progression-free survival (PFS) and overall survival (OS) in treatment-naïve CLL. Patients who achieve minimal residual disease negativity (MRD-) after induction chemoimmunotherapy (CIT) have prolonged PFS and OS. It is unclear, whether an extended therapy with an anti-CD20 mAb after induction CIT can improve the depth of response and long-term outcomes in patients with detectable residual disease (MRD+). Here we report results from a phase II study using risk-adapted, ofatumumab-based CIT induction followed by ofatumumab maintenance in treatment-naïve CLL patients. (NCT01145209) Methods: Treatment-naïve CLL patients were stratified twice: first, based on pre-treatment FISH, and second, based on post-induction peripheral blood (PB) MRD status. Patients with high-risk FISH (17p or 11q deletion) received up to 6 cycles of fludarabine, cyclophosphamide and ofatumumab (FCO). Patients without high-risk FISH received fludarabine, and ofatumumab (FO). Ofatumumab was dosed at 300mg for the first cycle, and 1000mg for subsequent cycles. After induction, patients were re-stratified based on PB MRD status using flow cytometry. MRD- was defined Results: We enrolled 32 patients. Twenty-eight patients received 3 or more cycles of induction CIT and were evaluable for outcomes. The overall response rate was 100%, including 8 (28.6%) patients achieving a complete response. The median PFS was 42.8 months and was significantly longer for patients who achieved MRD- after induction CIT compared to those with MRD+ (Not reached vs 36.2 months, p Antigen loss through Fc-gamma receptor-mediated uptake of antibody-antigen complexes into effector cells, referred to as trogocytosis, allows tumor cells to escape antibody-dependent cytotoxicity. At the same time, trogocytosis contributes to rapid clearance of circulating mAb. Investigating whether residual cells still expressed CD20, we measured expression of CD20 on CLL cells at the end of CIT. Most residual CLL in PB showed virtually complete loss of CD20 expression. We also stained BM biopsies obtained after 3 and 6 cycles of CIT for CD20 confirming absent or markedly reduced CD20 expressions on residual CD79+ CLL cells. In addition, the median trough level of ofatumumab on day 28 of each cycle increased with each advancing cycle (0, 13, and 51 mcg/mL after cycle 1, 2, and 3, respectively). Similarly, clearance of ofatumumab below the limit of detection (< 0.5mcg/mL) was observed in 60% of patients after the initial dose, and only 20% after cycle 3. Conclusions: Scaling intensity of CIT to genetic risk profiles achieved comparable outcomes for high-risk and standard-risk patients. MRD- remissions were associated with superior PFS, irrespective of the induction CIT regimen used. Maintenance therapy with ofatumumab did not improve the depth of response in MRD+ patients. Antibody induced antigen loss on tumor cells limits the efficacy of anti-CD20 mAbs even in settings with low tumor burden. Disclosures Farooqui: Merck: Employment. Lindorfer:Genmab: Research Funding. Wiestner:Pharmayclics: Research Funding; Acerta: Research Funding; Merck: Research Funding; Nurix: Research Funding.

Acute myeloid leukemia (AML) is a genetically heterogenous and often fatal cancer of the hematopoietic system. Even after achieving an initial complete remission, more than half of such AML patients experience clinical relapse due to the persistence of “minimal” residual disease (MRD). Ex-vivo studies have hypothesized that the interactions between residual leukemic cells and the local microenvironment in the bone marrow may play a key role in their survival and chemoresistance. Therefore, we performed for the first time a global examination of the proteomic profile of the bone marrow microenvironment in AML patients using a highly multiplexed method based on the ability of slow off-rate modified aptamers (modified small single-stranded oligonucleotides) to bind target proteins with high specificity and affinity at slow dissociation rates. Ten relapsed/refractory adult AML patients and age-matched healthy subject controls were recruited, under an IRB-approved protocol, for research bone marrow aspirate (BMA) and blood serum collection. The supernatant resulting from centrifugation of BMA and serum samples were processed and analyzed on a SOMAscan™ hybridization microarray platform for the detection and quantification of 1,305 target proteins (Somalogic, CO). Data was corrected using Hybridization Control and Median Signal Normalization methods. Significant differences were found between AML and healthy donor bone marrow, such that 133 analytes were differentially expressed in the AML group (Wilcoxon rank sum test FDR p1.5); 85 over-expressed and 48 under-expressed. In addition to proteins already known to be elevated in AML patients (eg: Erythropoietin, Thrombopoietin, Hepcidin and Ferritin) and dysregulation of pathways previously identified as disease relevant (eg: Arginase), we also discovered multiple statistically significant differences in levels of soluble proteins that are not currently known to be associated with AML pathogenesis or treatment. Comparative analysis between blood serum and bone marrow determined that 82 of the 133 candidates have differential expression that was specifically restricted to the bone marrow. The STRING database was queried for pathway analysis of enriched protein sets in the AML group and clustered analytes with molecular functions including cytokine activity (GO:0005125, n=11, p=1.93e-08), cytokine receptor binding (GO:0005126, n=12, p=3.17e-08) and signal transducer activity (GO:0004871, n=19, p=9.23e-05). Using a high-throughput proteomic technology we have identified an AML bone marrow microenvironment-specific profile comprised of both proteins with known implications in leukemic pathogenesis and also several novel candidates from biologically plausible pathways that, once validated, may provide mechanistic insight and opportunity for therapeutic targeting. Citation Format: Bogdan Popescu, Katherine Lindblad, Giovanna Fantoni, Gege Gui, Janet Valdez, Meghali Goswami, Christin DeStefano, Catherine Lai, Angélique Biancotto, Julián Candia, Foo Cheung, Julie Thompson, Laura W. Dillon, Christopher S. Hourigan. Highly multiplexed proteomic assessment of the human acute myeloid leukemia bone marrow microenvironment [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 3756.

Disease progression in patients with chronic lymphocytic leukemia (CLL) treated with ibrutinib has been attributed to histologic transformation or acquired mutations in BTK and PLCG2. The rate of resistance and clonal composition of PD are incompletely characterized. We report on CLL patients treated with single-agent ibrutinib on an investigator-initiated phase 2 trial. With median follow-up of 34 months, 15 of 84 evaluable patients (17.9%) progressed. Relapsed/refractory disease at study entry, TP53 aberration, advanced Rai stage, and high β-2 microglobulin were independently associated with inferior progression-free survival (P < .05 for all tests). Histologic transformation occurred in 5 patients (6.0%) and was limited to the first 15 months on ibrutinib. In contrast, progression due to CLL in 10 patients (11.9%) occurred later, diagnosed at a median 38 months on study. At progression, mutations in BTK (Cys481) and/or PLCG2 (within the autoinhibitory domain) were found in 9 patients (10.7%), in 8 of 10 patients with progressive CLL, and in 1 patient with prolymphocytic transformation. Applying high-sensitivity testing (detection limit ∼1 in 1000 cells) to stored samples, we detected mutations up to 15 months before manifestation of clinical progression (range, 2.9-15.4 months). In 5 patients (6.0%), multiple subclones carrying different mutations arose independently, leading to subclonal heterogeneity of resistant disease. For a seamless transition to alternative targeted agents, patients progressing with CLL were continued on ibrutinib for up to 3 months, with 19.8 months median survival from the time of progression. This trial was registered at www.clinicaltrials.gov as #NCT01500733.

Background: Bruton tyrosine kinase (BTK) is a critical component of B-cell receptor signaling and a validated target for CLL. Acalabrutinib is a highly selective, potent, covalent BTK inhibitor, which has shown promising efficacy and safety in patients with CLL, including high-risk patients. We present preliminary efficacy, safety, and pharmacodynamic results from an ongoing single-center, open-label, phase 2 study of acalabrutinib monotherapy in patients with R/R and high-risk, TN CLL. Methods: Patients with R/R or high-risk (chromosome 17p deletion [del17p] or mutation in TP53 or NOTCH1) TN CLL/small lymphocytic lymphoma (SLL) who met International Workshop on Chronic Lymphocytic Leukemia (IWCLL) 2008 criteria for treatment and had an Eastern Cooperative Oncology Group performance status ≤2 were eligible. Patients who had prior BTK inhibitor therapy were excluded. Patients were randomized to receive oral acalabrutinib 100 mg twice daily (BID) or 200 mg daily (QD) until progressive disease or unacceptable toxicity. The primary endpoint was investigator-assessed overall response rate (ORR) by IWCLL 2008 criteria with modification for lymphocytosis. Secondary endpoints included safety and BTK occupancy. BTK occupancy was measured with a biotin-tagged analogue probe in peripheral blood cells at drug trough time points after 3 days of dosing and after 1, 6, and 12 mo of treatment. BTK occupancy in lymph node samples was measured at drug trough time points after 3 days of dosing. Results: Forty-six patients were enrolled and treated (100 mg BID, n=22; 200 mg QD, n=24). The median age was 64 years (range, 45-83), and 35% (16/46) were TN. Approximately 39% of patients (25% of TN) had bulky lymph nodes ≥5 cm, 37% (50% of TN) had Rai stage III-IV disease at baseline, 76% (88% of TN) had unmutatedIGHV, 21% (40% of TN) had del(17p), 21% (23% of TN) had TP53 mutation, and 47% (54% of TN) had NOTCH1 mutation. As of April 13, 2018, the median time on study for all treated patients was 20 mo (range 1-39), with 89% (41/46) remaining on acalabrutinib. Two patients (9%) in the BID group and 3 patients (13%) in the QD group discontinued treatment due to an adverse event (AE; n=1), progressive disease (n=1), and other reasons (n=3). The patient who discontinued due to progressive disease (BID group) achieved partial response at 2 mo and developed Richter transformation at 6 mo. The ORR was 90% (95% CI: 76, 97) for efficacy evaluable patients (N=39), defined per protocol as patients who had ≥ 6 mo of acalabrutinib (Table). ORR was 95% (75, 100) and 84% (60, 97) for the BID and QD group, respectively. For the intent-to-treat population (N=46), ORR was 80% (66, 91). Most AEs were grade 1/2 and did not require dose delays or modifications. The most common AEs (all grades; >25%) were headache (63%), contusion (50%), diarrhea (43%), upper respiratory tract infection (43%), arthralgia (33%), influenza-like illness (28%), maculo-papular rash (28%), myalgia (26%), and nausea (26%). Grade 3/4 AEs occurred in 33% (15/46) of patients (BID, 27% [6/22]; QD, 38% [9/24]), most commonly (>10%) infections (13%; urinary tract infection, lung infection, hepatitis B reactivation, which led to treatment discontinuation and fatal hepatic failure after 10 mo of treatment, and an invasive pulmonary aspergillosis at 2 mo in the setting of prolonged neutropenia and recent systemic corticosteroid use that led to treatment discontinuation) and neutropenia (11%). Approximately 33% (15/46) of patients (BID, 23% [5/22]; QD, 42% [10/24]) reported serious AEs (all grades), most commonly (>5%) lung infection (7%). No atrial fibrillation was reported, and one grade 1 atrial flutter occurred (BID). On day 4 of cycle 1, median trough BTK occupancy was significantly higher for the BID group versus the QD group in the peripheral blood (95% vs 87%; P Conclusion: Acalabrutinib monotherapy produced high ORR in R/R and high-risk TN CLL, with an acceptable safety profile. The study was not designed to detect a statistically significant difference in clinical outcomes between the dosing groups. Near complete target coverage (>95%) was more rapidly achieved with 100 mg BID than 200 mg QD dosing in the lymph node and peripheral blood. Disclosures Nierman: National Institutes of Health: Employment. Covey:Acerta Pharma: Employment; AstraZeneca: Equity Ownership. Hamdy:Acerta Pharma: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: various patents for ACP-196. Izumi:Acerta Pharma: Employment, Equity Ownership, Patents & Royalties: Acerta Pharma, various patents for ACP-196. Liu:Acerta Pharma: Employment. Patel:Acerta Pharma: Employment, Equity Ownership. Wiestner:Pharmacyclics LLC, an AbbVie Company: Research Funding.

Background: The powerful "graft versus leukemia" effect thought partly responsible for the therapeutic effect of allogeneic hematopoietic stem cell transplantation in reducing relapse of high-risk acute myeloid leukemia (AML) provides the rationale for the investigation of immune-based therapy in those with relapsed or refractory AML. There is considerable pre-clinical evidence for potential synergy between PD-1 checkpoint blockade and hypomethylating agents. Aims: To determine the feasibility of a novel combination of pembrolizumab and decitabine in relapsed/refractory adult AML patients. Methods: 17-H-0026, (PD-AML, NCT02996474) was an investigator sponsored, single-institution, single-arm open-label ten subject study approved by the NHLBI IRB and conducted in accordance with the Declaration of Helsinki (FDA IND: 131826). Pembrolizumab 200 milligrams was administered intravenously on day 1 of every three-week cycle, with decitabine 20 milligrams per meter squared administered on days 8-12 and 15-19 (i.e.: total of 10 days) of alternative cycles starting with cycle 1. Up to eight cycles (24 weeks) of therapy were given. Results: Ten high-risk patients (median age 62, range 30-81) were enrolled, seven with refractory disease (including two with therapy-related myeloid neoplasm) and three with early relapse (less than 6 months from completion of last therapy). This novel combination therapy was well tolerated, with a toxicity profile largely consistent with that expected from decitabine. No grade 5 adverse events occurred. Most grade 4 adverse events were hematological. Non-hematological grade 4 events were seen in only two subjects; febrile neutropenia, hypotension and sepsis in one, and sepsis in the other. Two patients suffered from hypothyroidism as an immune-related adverse event (after 2 and 4 cycles respectively) and a third patient developed central diabetes insipidus thought possibly associated with pembrolizumab. In summary, 4 of the 10 patients had stable disease at the end of 8 cycles (24 weeks), 4 progressed prior to cycle 8, 1 patient was taken off study due to grade 4 toxicity (sepsis) in cycle 5 in a morphological leukemic free state (MLFS) and 1 patient achieved an MRD negative complete response at the end of 8 cycles. Specifically, a 74 year-old male patient, enrolled at second relapse, achieved a CR3 lasting 337 days (compared with prior CR2 of 185 days) which was MRD negative at the end of eight cycles, and was still alive 14 months from start of treatment. A 81 year old male patient, with refractory treatment related myeloid neoplasm achieved a MRD-negative MLFS but was removed from study early due to grade 4 toxicity. The 4 patients with stable disease at the end of planned eight cycles included a 71 year-old male patient in early first relapse who decreased blasts from 4.4% at enrollment to 0.1% at the end of 8 cycles. Median overall survival for patients on this study was 7 months (range 2 to ongoing at 14 months) with a median time of follow-up in survivors of 13 months (range 7-14 months). Updated survival data will be reported at the meeting. Additional planned laboratory correlates include assessment of changes in leukemic clonality, T-cell receptor repertoire diversity and bone marrow-resident immune cell profiles during therapy. Conclusion/summary: This first proof of principle study demonstrates the feasibility of the combination of pembrolizumab and decitabine in relapsed/refractory adult AML patients. . Table. Table. Disclosures No relevant conflicts of interest to declare.

Eltrombopag (EPAG) received FDA approval for treatment of refractory severe aplastic anemia (rSAA) in 2014, based on our phase I/II dose escalation trial of single agent EPAG for patients failing one or more treatment cycles with ATG/cyclosporine (Olnes NEJM 2012; Desmond Blood 2014). There is no standard treatment for patients with moderate aplastic anemia (MAA) or hypo-productive uni-lineage cytopenias (MAA/UC), conditions that can also impact on morbidity, mortality and quality of life. To explore the safety and effectiveness of EPAG in MAA/UC, we conducted a phase II study of EPAG given at escalating doses from 50-300mg/day (25-150mg/day for East Asians) through a primary hematologic response endpoint at 16-20 weeks (NCT 01328587). 34 patients enrolled between February 2012 and March 2017. 27 had never been treated with ATG/CSA IST. Responding patients could continue EPAG treatment on an extension arm. The drug was well-tolerated in 33/34 patients, with 1 patient coming off study at 10 weeks for nausea and vomiting. 25 patients reached the maximal dose. The median duration of follow-up in all patients was 16 months, and 27 months in responding patients. 17 of 34 (50%) of patients met criteria for response at the primary endpoint in at least one initially protocol-qualifying lineage (Hb 1.5 gr/dL increase in Hb or > 50% reduction in transfusions), including a patient with RSP19-mutated Diamond-Blackfan anemia. 7/24 with severe thrombocytopenia had a platelet response (>20,000/ul or transfusion-independence). 2/13 with both severe anemia and thrombocytopenia had bi-lineage responses at the primary endpoint, and an additional 5 went on to bi-lineage responses during the extension period. 3 patients without a response to EPAG were later treated with ATG/CSA and responded. EPAG was discontinued in 11/17 (65%) responding patients upon achievement of robust blood counts (Hb > 10mg/dL, platelets > 50,000/uL, and ANC > 1000) or stable blood counts for 6 months in 1 patient (6%) after a median duration of drug administration of 8 months (2-14 months) (Fig 1). In contrast to our prior experience in rSAA, the majority of patients still being followed on study after drug discontinuation (8/10) needed to have EPAG re-initiated for declining counts at a median of 6 months (2-38) later. All 8 responded again, with 4/8 able to discontinue EPAG after a second robust or stable response. 2/34 patients (6%) developed marrow cytogenetic abnormalities while on drug in contrast to 16/83 (16%) rSAA patients treated with EPAG in our prior studies. Both MAA patients were responders and neither had dysplastic changes or increased blasts. Patient # 5 had +8 in 7/20 metaphases at 22m, went off drug and relapsed, and EPAG was restarted off protocol. Repeat cytogenetics on EPAG were normal. Patient #20 had del13q in 5/20 metaphases at 9.5m, EPAG was stopped, and repeat cytogenetics off drug were normal. Of note, patient #12 had a robust response and had been off drug for 25m when counts declined and BM revealed dysplastic changes with no increase in blasts and normal cytogenetics. The acquisition and selection of somatic mutations, particularly in myeloid candidate genes (MCG) recurrently mutated in MDS/AMLhas been proposed to be an initiating step in clonal evolution. We performed targeted next generation exome sequencing (NGS) of 66 MCG and additional genes previously found to be somatically-mutated in SAA (Yoshizato, NEJM, 2015) pre-EPAG treatment and at the primary response endpoint of 16-20 weeks. Only 5 patients showed somatic mutations in these genes at baseline (SETBP1, CBL, SF3B1, PPMID, EP300). There were no significant changes in VAF. 2 mutations became detectable on EPAG (BCOR, and DNMT3A transiently), and 1 disappeared (SF3B1). In summary, administration of EPAG at escalating doses up to of 300mg/day was well-tolerated and 50% of patients with MAA/UC had clinically-meaningful responses, including those not previously treated with IST. The responses were durable, often robust, although frequently required ongoing EPAG treatment, in contrast to the experience in rSAA. Clonal cytogenetic evolution was rare, with no instances of chromosome 7 abnormalities, and there was no consistent expansion of MCG somatically-mutated clone size in patients during EPAG treatment. Figure. Figure. Disclosures Winkler: National Institute of Health: Research Funding. Young:CRADA with Novartis: Research Funding; GlaxoSmithKline: Research Funding; National Institute of Health: Research Funding. Dunbar:National Institute of Health: Research Funding.

Introduction Immune dysregulation in chronic lymphocytic leukemia (CLL) contributes to a high rate of infections and morbidity. We previously reported that treatment of CLL with ibrutinib, a Bruton tyrosine kinase (BTK) inhibitor, leads to partial reconstitution of humoral immunity and fewer infections, especially in patients who achieved a ≥50% increase in serum IgA levels. Acalabrutinib is also an irreversible BTK inhibitor that is more selective than ibrutinib and has demonstrated safety and efficacy in the treatment of relapsed or refractory CLL. It is currently unclear how the increased specificity of acalabrutinib affects immune reconstitution and infection rates. We assessed the immunological impact of acalabrutinib in patients with CLL treated with single-agent acalabrutinib. Methods Samples originated from a phase 2, single-center trial studying acalabrutinib 100 mg twice daily (BID) or acalabrutinib 200 mg once daily (QD) in patients with relapsed/refractory (RR) CLL or high-risk, treatment naïve (TN) CLL (chromosome 17p deletion or mutation in TP53 or NOTCH1) (NCT02337829). Patients who received at least 6 months of acalabrutinib and had paired longitudinal data available were included in the analyses. Patients receiving IV immunoglobulin replacement were excluded from analysis of IgG levels. Additionally, patients with detectable monoclonal IgG, IgA and/or IgM proteins on serum immunofixation were excluded from analysis of the corresponding immunoglobulin isotype. The analysis of free light chains was stratified based on k or λ restriction of CLL cells determined by flow cytometry. Immunohistochemical staining of bone marrow biopsies was performed: T cell numbers were estimated by CD3 staining and the degree of CD68-positive macrophage extensions in contact with CLL cells were semi-quantitatively assessed on a scale from 0 (no extensions) to 4 (maximum number of extensions). The Wilcoxon signed-rank test and the Mann-Whitney U test were used to compare paired and unpaired data, respectively. Differences in the rate of infection between groups were examined using the Cox regression model for recurrent events. Results Serum IgA levels increased as early as 3 months after the initiation of acalabrutinib (median increase 35.7%, P = .0001), with levels sustained up to 24 months (Figure 1), whereas serum IgG and IgM levels were not affected by acalabrutinib. There was no difference (P > .05) in IgA, IgG, IgM trend between TN or RR CLL. Furthermore, there was no difference (P > .05) in IgA, IgG and IgM trends between patients treated with QD compared to BID dosing of acalabrutinib. Among 20 k-restricted and 18 λ-restricted CLL cases, the involved (tumor-derived) free light chain was elevated at baseline and trended toward the normal range after 3 months of acalabrutinib therapy consistent with an anti-tumor effect (k: median decrease 55.4%; P < .0001 and λ: median decrease 49.1%; P = .0003). The uninvolved free light chain did not change (P > .05). Peripheral blood CD3+, CD4+ and CD8+ T cell counts were elevated above the laboratory reference range at baseline and normalized after 6 months (CD4+ median decrease 49.2%; P = .0074 and CD8+ median decrease 54.8%; P = .003). T cell numbers in the bone marrow did not appreciably change. However, treatment-induced changes of the immune microenvironment were apparent in tumor-macrophage interactions. At baseline, macrophages tightly interacted with CLL cells, often with multiple podocytes making contact with CLL cells. On acalabrutinib, we observed a decrease in these macrophage podocyte interactions (P = .0007). At a median follow-up of 20 months, 31 (68.9%) patients developed a total of 68 infections, including 7 (10.3%) grade 3 and 1 (1.5%) grade 4 infections. Patients with superior immune reconstitution, as defined by an increase in serum IgA of ≥ a median of 36% from baseline to 3 months, had a significantly lower rate of infections (risk ratio = 0.52, P = 0.029). Conclusions These data indicate that acalabrutinib allows for partial reconstitution of humoral and cell-mediated immunity and disrupts macrophage-CLL cell interaction in the bone marrow microenvironment in patients with CLL. Furthermore, acalabrutinib did not interfere with uninvolved free light chains, suggesting that acalabrutinib selectively inhibits CLL B-cells and does not impair normal B-cell function. Disclosures Izumi: Acerta Pharma: Employment, Equity Ownership, Patents & Royalties: Acerta Pharma, various patents for ACP-196. Hamdy:Acerta Pharma: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: Acerta Pharma, various patents for ACP-196. Wiestner:Pharmacyclics LLC, an AbbVie Company: Research Funding.

Chronic lymphocytic leukemia (CLL) is characterized by immune dysregulation, often including hypogammaglobulinemia, which contributes to a high rate of infections and morbidity. Ibrutinib, a covalent inhibitor of Bruton tyrosine kinase (BTK), inhibits B-cell receptor signaling and is an effective, US Food and Drug Administration (FDA)-approved treatment of CLL. Inactivating germline mutations in BTK cause a severe B-cell defect and agammaglobulinemia. Therefore, we assessed the impact of ibrutinib on immunoglobulin levels, normal B cells, and infection rate in patients with CLL treated with single-agent ibrutinib on a phase 2 investigator-initiated trial. Consistent with previous reports, immunoglobulin G (IgG) levels remained stable during the first 6 months on treatment, but decreased thereafter. In contrast, there were a transient increase in IgM and a sustained increase in IgA (median increase 45% at 12 months, P < .0001). To distinguish the effects on clonal B cells from normal B cells, we measured serum free light chains (FLCs). In κ-clonal CLL cases, clonal (κ) FLCs were elevated at baseline and normalized by 6 months. Nonclonal (λ) FLCs, which were often depressed at baseline, increased, suggesting the recovery of normal B cells. Consistently, we observed normal B-cell precursors in the bone marrow and an increase in normal B-cell numbers in the peripheral blood. Patients with superior immune reconstitution, as defined by an increase in serum IgA of ≥50% from baseline to 12 months, had a significantly lower rate of infections (P = .03). These data indicate that ibrutinib allows for a clinically meaningful recovery of humoral immune function in patients with CLL. This trial was registered at www.clinicaltrials.gov as #NCT015007330.

Purpose: Clinical trials of ibrutinib combined with anti-CD20 monoclonal antibodies (mAb) for chronic lymphocytic leukemia (CLL) report encouraging results. Paradoxically, in preclinical studies, in vitro ibrutinib was reported to decrease CD20 expression and inhibit cellular effector mechanisms. We therefore set out to investigate effects of in vivo ibrutinib treatment that could explain this paradox. Experimental Design: Patients received single-agent ibrutinib (420 mg daily) on an investigator-initiated phase II trial. Serial blood samples were collected pretreatment and during treatment for ex vivo functional assays to examine the effects on CLL cell susceptibility to anti-CD20 mAbs. Results: We demonstrate that CD20 expression on ibrutinib was rapidly and persistently downregulated (median reduction 74%, day 28, P < 0.001) compared with baseline. Concomitantly, CD20 mRNA was decreased concurrent with reduced NF-κB signaling. An NF-κB binding site in the promoter of MS4A1 (encoding CD20) and downregulation of CD20 by NF-κB inhibitors support a direct transcriptional effect. Ex vivo, tumor cells from patients on ibrutinib were less susceptible to anti-CD20 mAb-mediated complement-dependent cytotoxicity than pretreatment cells (median reduction 75%, P < 0.001); however, opsonization by the complement protein C3d, which targets cells for phagocytosis, was relatively maintained. Expression of decay-accelerating factor (CD55) decreased on ibrutinib, providing a likely mechanism for the preserved C3d opsonization. In addition, ibrutinib significantly inhibited trogocytosis, a major contributor to antigen loss and tumor escape during mAb therapy. Conclusions: Our data indicate that ibrutinib promotes both positive and negative interactions with anti-CD20 mAbs, suggesting that successfully harnessing maximal antitumor effects of such combinations requires further investigation. Clin Cancer Res; 22(1); 86–95. ©2015 AACR.

Summary Background Patients with chronic lymphocytic leukaemia (CLL) with TP53 aberrations respond poorly to first-line chemoimmunotherapy, resulting in early relapse and short survival. We investigated the safety and activity of ibrutinib in previously untreated and relapsed or refractory CLL with TP53 aberrations. Methods In this investigator-initiated, single-arm phase 2 study, we enrolled eligible adult patients with active CLL with TP53 aberrations at the National Institutes of Health Clinical Center (Bethesda, MD, USA). Patients received 28-day cycles of ibrutinib 420 mg orally once daily until disease progression or the occurrence of limiting toxicities. The primary endpoint was overall response to treatment at 24 weeks in all evaluable patients. This study is registered with ClinicalTrials.gov, number NCT01500733, and is fully enrolled. Findings Between Dec 22, 2011, and Jan 2, 2014, we enrolled 51 patients; 47 had CLL with deletion 17p13.1 and four carried a TP53 mutation in the absence of deletion 17p13.1. All patients had active disease requiring therapy. 35 enrolled patients had previously untreated CLL and 16 had relapsed or refractory disease. Median follow-up was 24 months (IQR 12·9–27·0). 33 previously untreated patients and 15 patients with relapsed or refractory CLL were evaluable for response at 24 weeks. 32 (97%; 95% CI 86–100) of 33 previously untreated patients achieved an objective response, including partial response in 18 patients (55%) and partial response with lymphocytosis in 14 (42%). One patient had progressive disease at 0·4 months. 12 (80%; 95% CI 52–96) of the 15 patients with relapsed or refractory CLL had an objective response: six (40%) achieved a partial response and six (40%) a partial response with lymphocytosis; the remaining three (20%) patients had stable disease. Grade 3 or worse treatment-related adverse events were neutropenia in 12 (24%) patients (grade 4 in one [2%] patient), anaemia in seven (14%) patients, and thrombocytopenia in five (10%) patients (grade 4 in one [2%] patient). Grade 3 pneumonia occurred in three (6%) patients, and grade 3 rash in one (2%) patient. Interpretation The activity and safety profile of single-agent ibrutinib in CLL with TP53 aberrations is encouraging and supports its consideration as a novel treatment option for patients with this high-risk disease in both first-line and second-line settings. Funding Intramural Research Program of the National Heart, Lung, and Blood Institute and the National Cancer Institute, Danish Cancer Society, Novo Nordisk Foundation, National Institutes of Health Medical Research Scholars Program, and Pharmacyclics Inc.

SummaryA major goal of systems biology is the development of models that accurately predict responses to perturbation. Constructing such models requires the collection of dense measurements of system states, yet transformation of data into predictive constructs remains a challenge. To begin to model human immunity, we analyzed immune parameters in depth both at baseline and in response to influenza vaccination. Peripheral blood mononuclear cell transcriptomes, serum titers, cell subpopulation frequencies, and B cell responses were assessed in 63 individuals before and after vaccination and were used to develop a systematic framework to dissect inter- and intra-individual variation and build predictive models of postvaccination antibody responses. Strikingly, independent of age and pre-existing antibody titers, accurate models could be constructed using pre-perturbation cell populations alone, which were validated using independent baseline time points. Most of the parameters contributing to prediction delineated temporally stable baseline differences across individuals, raising the prospect of immune monitoring before intervention.

The major complication of severe aplastic anemia is clonal evolution, defined as any new cytogenetic abnormality or progression to MDS/AML, which occurs in about 15% of SAA patients, usually many months to years after the diagnosis. Eltrombopag, a thrombopoietin receptor agonist, appears capable of stimulating hematopoietic stem cell proliferation in patients with bone marrow failure. Addition of eltrombopag to standard immunosuppressive treatment (IST) with horse antithymocyte globulin (hATG) and cyclosporine (CsA) markedly increases hematologic response rates in treatment-naive SAA, with overall response rates up to 90% and complete response rates approaching 60% (Townsley DM et al, ASH 2015, clinicaltrials.gov NCT01623167). In comparison, IST alone achieves 60% overall response rates, of which 10% are complete (Scheinberg Blood 2012). Somatic mutations in myeloid cancer candidate genes are present in one-third of patients after IST alone (Yoshizato T et al, NEJM 2015). Specific subsets of mutations were associated with clinical outcomes: a group including ASXL1 and DNMT3A with a poor response to IST, inferior survival, and clonal evolution, while BCOR and PIGA were associated with good response and favorable outcomes. Monosomy 7, the most prevalent cytogenetic abnormality defining clonal evolution, can develop in the absence of gene mutations, underscoring the non-determinative and complex role mutations play in clonal evolution (Dumitriu B et al, Blood 2015). Of patients with disease refractory to IST who were subsequently treated with single-agent eltrombopag, 19% (8/43) developed cytogenetic abnormalities, usually within the first year of treatment, but only rarely with morphologic changes consistent with MDS/AML (Desmond R et al, Blood 2014). The frequency of somatic mutations following treatment with eltrombopag added to IST in treatment-naïve SAA patients is unknown. We used amplicon-based next-generation sequencing to assess mutations in 54 candidate genes recurrently mutated in myeloid neoplasms. Bone marrow cells of 90 subjects who had been treated with IST/eltrombopag were obtained at 6 months following treatment initiation, or at the time of clonal evolution. At least one detectable mutation was identified in 21 (23%) subjects. All 21 patients had exhibited a hematologic response to treatment by 6 months; of those patients with somatic mutations, 14 of 19 (74%) had a complete hematologic response. In comparison, of the 69 patients who lacked mutations, 20 (29%) had a complete response. Nine different genes were mutated in total, with the most frequent genes being ASXL1 and BCOR. BCOR was associated with more robust responses (6 of 7 had a complete response) and younger age (range 12 - 49 years; Table). One subject with a longstanding history of JAK2-positive essential thrombocytosis and myelofibrosis at baseline had two additional mutations detectable following treatment, TET2 and ASXL1. With a median follow up of 21 months, clonal cytogenetic evolution occurred in 7/90 (8%) subjects. Three of seven patients also had a mutation in a myeloid cancer gene (two with DNMT3A and one with ASXL1/RUNX1); in the other four, no somatic mutation was detected, either at the 6-month time point or at time of cytogenetic evolution. Four patients had monosomy or partial deletion of chromosome 7: one patient had complex (t(3;3)(q21;q26), -7), one patient had deletion 13q that later disappeared, and one patient had trisomy 6 and trisomy 15 in 2 metaphases. The patient with complex cytogenetics did not have somatic mutations detected at evolution, and she later died due to relapsed AML following transplant. The rates of somatic mutations in myeloid cancer genes and of cytogenetic evolution in patients treated with IST/eltrombopag do not appear to be higher than we and others have reported in aplastic anemia treated with standard IST, without eltrombopag (Kulasekararaj AG et al, Blood 2014). The distribution of genes mutated and the allelic frequency of these mutations also were similar to patients treated with standard IST. These results suggest that the benefits of a higher response rate and quality of response associated with the addition of eltrombopag to IST for the initial treatment of SAA are not associated with a higher risk of clonal progression. Disclosures Townsley: GSK/Novartis: Research Funding. Cooper:GSK/Novartis: Research Funding. Winkler:GSK/Novartis: Research Funding. Scheinberg:Novartis: Consultancy, Speakers Bureau. Rios:GSK/Novartis: Research Funding. Weinstein:GSK/Novartis: Research Funding. Desierto:GSK/Novartis: Research Funding. Fernandez Ibanez:GSK/Novartis: Research Funding. Dunbar:GSK/Novartis: Research Funding. Ma:Neogenomics Laboratories: Employment. Albitar:Neogenomics Laboratories: Employment, Equity Ownership. Young:GSK/Novartis: Research Funding.

Introduction: Progressive disease on ibrutinib is an emerging area of an unmet need. The key mechanism of ibrutinib resistance is driven by the growth of subclones with BTK and/or PLCG2 mutations under selective pressure from therapy [Woyach JA et al, N Engl J Med 2014; Burger et al, Nat Commun 2016]. It is unclear, however, how to effectively discriminate patients who are at risk of progression during ibrutinib. Established prognostic factors in CLL were developed in the context of chemoimmunnotherapy, and only limited data are available on predictive values of complex karyotype [Thompson et al, Cancer 2015] and deletion 17p [Byrd et al, Blood 2015] in patients receiving ibrutinib. To determine predictive values of conventional prognostic factors in CLL, we performed multivariate analyses of factors relevant to progression-free survival (PFS) on ibrutinib. Methods and Patients: 84 evaluable CLL patients received single-agent ibrutinib 420mg once daily under a phase II investigator-initiated trial (NCT01500733). 3-year safety and efficacy results from this trial were previously reported [Farooqui et al, 2015 ASH Annual Meeting Abstract 2937]. Briefly, eligible patients had either TP53 aberration (deletion 17p by FISH or TP53 mutation by targeted sequencing) or were 65 years or older. The study included both treatment-naive and relapsed/refractory patients. Metaphase karyotype was not routinely performed. The study was approved by the institutional review board, and conducted in accordance with the Declaration of Helsinki. Cox regression models were used to identify independent predictors of progression. Probability of PFS was estimated by the Kaplan-Meier method. Log-rank test was used to compare PFS probabilities between subgroups. Statistical analyses were performed using R statistical software version 3.2.3. Result: At the median follow up of 34.3 months, 19 (22.6%) of 84 evaluable patients progressed or died on study; 15 (17.9%) patients progressed and 4 (4.8%) additional patients died due to reasons unrelated to progression. Independent factors of PFS identified from univariate analysis were; TP53 aberration, prior treatment, advanced Rai stage (III/IV) and high beta-2 microgloblin (B2M) (>4mg/L or = Conclusion: This is the first integrated risk scoring system developed from patients receiving ibrutinib If confirmed in independent cohorts this model could enable early risk stratification for treatment trials with combination regimens or with alternative targeted agents. Conversely, the absence of adverse prognostic factors can be used to identify a subgroup who may benefit from single-agent ibrutinib and can potentially discontinue therapy if deep responses are achieved after long-term ibrutinib. Disclosures Farooqui: Merck: Employment. Wiestner:Pharmacyclics: Research Funding; Acerta Pharma: Research Funding.

Importance Ibrutinib, a Bruton tyrosine kinase inhibitor, is a new targeted agent approved by the US Food and Drug Administration for the treatment of chronic lymphocytic leukemia (CLL), mantle cell lymphoma, and Waldenstrom macroglobulinemia. Ibrutinib is overall well tolerated but long-term treatment is required until disease progression or intolerable toxic effects occur. Little is known regarding its cutaneous adverse effects. Objective To describe the hair and nail manifestations associated with the long-term use of ibrutinib for the treatment of CLL. Design, Setting, and Participants Prospective study of 66 patients with CLL enrolled in a single-arm phase 2 clinical trial of ibrutinib for CLL between March 2014 and October 2015 at the National Institutes of Health. Main Outcomes and Measures The primary outcome, nail and hair changes associated with ibrutinib therapy, was assessed by an 11-question survey. In addition, the severity of nail changes was determined from a 0 to 3 rating scale for both onychoschizia and onychorrhexis. Results Among 66 patients (43 men and 23 women with ages ranging from 55 to 85 years), 44 (67%) reported brittle fingernails at a median of 6.5 (95% CI, 6-12) months after starting ibrutinib therapy. Fifteen patients (23%) developed brittle toenails after a median of 9 (95% CI, 6-15) months of ibrutinib therapy. Textural hair changes were reported in 17 patients (26%), at a median of 9 (95% CI, 6-12) months of ibrutinib treatment. Conclusions and relevance Hair and nail abnormalities are commonly associated with ibrutinib and appear several months after initiating therapy. Ibrutinib inhibits Bruton tyrosine kinase by covalently binding to cysteine 481. Whether ibrutinib affects the hair and nails by binding and altering cysteine-rich proteins of hair and nails or by means of another mechanism remains unknown. Trial Registration clinicaltrials.gov Identifier:NCT01500733

Background In chronic lymphocytic leukemia lenalidomide causes striking immune activation, possibly leading to clearance of tumor cells. We conducted this study to investigate the mechanism of action of lenalidomide and the basis for its unique toxicities in chronic lymphocytic leukemia.Design and Methods Patients with relapsed chronic lymphocytic leukemia were treated with lenalidomide 20 mg (n=10) or 10 mg (n=8) daily for 3 weeks on a 6-week cycle. Correlative studies assessed expression of co-stimulatory molecules on tumor cells, T-cell activation, cytokine levels, and changes in lymphocyte subsets.Results Lenalidomide upregulated the co-stimulatory molecule CD80 on chronic lymphocytic leukemia and mantle cell lymphoma cells but not on normal peripheral blood B cells in vitro. T-cell activation was apparent in chronic lymphocytic leukemia, weak in mantle cell lymphoma, but absent in normal peripheral blood mononuclear cells and correlated with the upregulation of CD80 on B cells. Strong CD80 upregulation and T-cell activation predicted more severe side effects, manifesting in 83% of patients as a cytokine release syndrome within 8–72 h after the first dose of lenalidomide. Serum levels of various cytokines, including tumor necrosis factor-α, increased during treatment. CD80 upregulation on tumor cells correlated with rapid clearance of leukemic cells from the peripheral blood. In contrast, neither the severity of the cytokine release syndrome nor the degree of T-cell activation in vitro correlated with clinical response.Conclusions Upregulation of CD80 on tumor cells and T-cell activation correlate with unique toxicities of lenalidomide in chronic lymphocytic leukemia. However, T-cell activation appears to be dispensable for the drug’s anti-tumor effects. This provides a rationale for combinations of lenalidomide with fludarabine or alemtuzumab.

Immunosuppressive treatment (IST) with horse antithymocyte globulin (hATG) and cyclosporine (CsA) for severe aplastic anemia (SAA) has a 60-65% rate of overall hematologic response (OR) and approximately 10% complete response (CR). These rates have remained stable over the last three decades despite efforts to improve upon this regimen (Scheinberg Blood 2012). Eltrombopag (EPAG), an oral thrombopoietin receptor agonist has activity in refractory SAA producing hematologic responses, the majority multilineage, in about 40% of patients when administered as a single agent (Olnes NEJM 2012; Desmond Blood 2014). We conducted an investigator-initiated, phase II, single-center trial to test the efficacy of adding EPAG to h-ATG/CsA (clinicaltrials.gov, NCT01623167), using a triple cohort design to optimize the regimen. Eighty-eight patients with treatment-naive SAA have been enrolled from July 2012 to October 2015. All received standard h-ATG and CsA. EPAG was administered at 150 mg daily to three consecutive cohorts: in the first (n=30) and second (n=31) cohorts, EPAG was introduced after hATG, from day 14 until 6 months (cohort 1) or 3 months (cohort 2), due to initial concern of hepatotoxicity. In the third cohort, EPAG was concurrent with hATG on day 1 and continued for 6 months (n=27). As analysis of our previous IST trials suggested that CR correlates with better survival and less evolution to MDS/AML, the primary endpoint in the current protocol was CR at 6 months. Baseline enrollment characteristics were similar across cohorts: median age was 31 years (range 3 – 82; 20% were 1%. EPAG was well tolerated when combined with CsA and hATG; 2 patients discontinued EPAG for severe cutaneous reactions, and 6 patients withdrew before 6 months due to refractoriness (n=4) or evolution to MDS (n=2). OR and CR were higher at 3 months and 6 months for all cohorts compared to historic rates (Table): OR at 6 months was 80%, 87% and 92%, respectively for the three cohorts; CR at 6 months was 33%, 26%, and 54%, respectively. For all patients evaluable to date, OR at 3 and 6 months of 80% and 85% and CR rates of 28 and 34% were higher when compared to our historical rates (p Improvements in blood counts among partial responders were robust by 3 months in all cohorts: median ANC 1790/ul; hemoglobin 10 gm/dL; and platelets 60,500/ul. For patients with very severe neutropenia (ANC500/uL was 47 days for all cohorts (n=23), and 35 days for cohort 3 (n=7). Among responders, median time to transfusion-independence for platelets was 32 days and for red cells 42 days. Serial BM biopsies showed improved cellularity in 80% without increased fibrosis. Median increase from baseline in BM CD34+ cells, as measured by flow cytometry, was 17-fold and 4-fold at 3 months for cohorts 1 and 2 respectively (p At median follow up 15 months (range 1 – 42 m), cytogenetic abnormalities have occurred in 7 patients: 4 monosomy or partial deletion of chromosome 7, 1 complex (t(3;3)(q21;q26), -7), 1 deletion 13q that later normalized, and 1 subject with trisomy 6 and trisomy 15 in 2 metaphases. We sequenced 54 candidate genes, recurrently mutated in MDS/AML: somatic mutations were not identified in 4 of 7 subjects prior to treatment or at the time of cytogenetic evolution. Clonal evolution to MDS occurred at a similar frequency compared to our historic experience with standard IST. Addition of EPAG to IST markedly increases overall and complete hematologic response rates in treatment-naive SAA. These results suggest that immediate institution of EPAG with IST may salvage and expand residual hematopoietic stem cells in aplastic anemia, accelerating the rate and quality of hematopoietic recovery. Rapid blood count improvement and reduced transfusion burden support early use of EPAG for patients with newly diagnosed severe aplastic anemia. Disclosures: Townsley: Novartis: Research Funding ; GSK: Research Funding. Off Label Use: Eltrombopag (Promacta) is not FDA approved for treatment naive aplastic anemia. Dumitriu:Novartis: Research Funding ; GSK: Research Funding. Winkler:GSK: Research Funding ; Novartis: Research Funding. Larochelle:Novartis: Research Funding ; GSK: Research Funding. Dunbar:Novartis: Research Funding ; GSK: Research Funding. Young:Novartis: Research Funding ; GSK: Research Funding.

INTRODUCTION: Ibrutinib is FDA approved for patients (pts) with CLL who are previously treated or have deletion (del) 17p. Data on depth and durability of response beyond the first 2 years of therapy are limited. Here we compare the response of pts with and without del17p with long follow-up(f/u). PATIENTS AND METHODS: This investigator-initiated phase II trial (NCT01500733) enrolled 86 pts (Cohort 1: no del17p, n=35; Cohort 2: del17p n=51). Both treatment (tx) naïve (TN) and relapsed refractory (R/R) pts with active disease were eligible. Response was assessed by computed tomography (CT), physical exam, bone marrow (BM) biopsy, and routine clinical and laboratory studies. Spleen volume (SV) was calculated from CT scans using a General Electric Advanced Workstation Server. Eight color flow cytometry (FC) on peripheral blood (PB) and BM was performed at yearly intervals. Wilcoxon rank-sum test was used to examine the differences between the two cohorts. RESULTS: Median f/u for all pts currently on study was 36 months (mo). Among pts with no del17p 24 (69%) pts completed 2 years(y) and 12 (34%) pts completed 3y. 33 (65%) pts with del17p completed 2y and 18 (35%) pts completed 3y. Median age was 66y (33-85) and 70% had Rai stage III/IV. Most adverse events were grade ≤2, most commonly (>25%) diarrhea, nail ridging, arthralgias, rash, bruising, and cramps. Tx-related non hematologic toxicities grade ≥3 occurred in The estimated progression free survival and overall survival at 36 mo is 82% and 88%. A total of 81 pts (n=33 (no del17p), n=48 (del17p)) were evaluable for response (2 enrollment deviations, 1 malignancy, 2 deaths before 6 mo). 5 (6%) deaths occurred on study (4 infections not tx-related, 1 possibly tx-related sudden death). 2 (2%) pts were primary refractory and 7 (8%) pts had progressive disease (PD) after initial response (3 CLL, 2 PLL, 2 Richter's transformation). Best response was complete response (CR) in 17 (21%) pts, partial response (PR) in 60 (74%), and stable disease (SD) and progressive disease (PD) each in 2 (2%) pts. Median time to best response was 2y. Responses for TN vs R/R pts were: 20 vs 23% CR, 78% vs 68% PR, 0% vs 6% SD, 2% vs 3% PD, and for no del17p vs del17p: 21% vs 21% CR, 73% vs 75% PR, 3% vs 2% each with SD and PD. There were no statistically significant differences in response rates by prior tx or del17p status. Disease control in all evaluable tissue sites were compared between the two cohorts based on del17p status (no del17p vs del17p) (Table): median reduction in lymphadenopathy 89% (59-100) vs 82% (22-100), median reduction in SV 94% (26-100) vs 98% (37-100), median reduction in tumor infiltration in the BM was 90% (11-99) vs 88% (28-100), and ALC response showed a median reduction of 97% (range: +44% to -99%) and 95% (range: +119% to -99%). Table. Median tumor reduction at best response. Compartment All pts NO DEL17p DEL 17p P Nodal 85% (n=79) 89% (n=32) 82% (n=47) 0.01 Spleen 98% (n=67) 94% (n=28) 98% (n=39) 0.3 BM 89% (n=73) 90% (n=31) 88% (n=42) 0.6 ALC 96% (n=81) 97% (n=33) 95% (n=48) 0.16 We quantified depth of response by measuring the degree of flow cytometric minimal residual disease (MRD) (CLL % of leukocytes). The median MRD at 1y (n=51), 2y (n=46), and 3y (n=24) in PB was 41%, 12%, and 8% respectively. Median MRD values at 1y (n=17), 2y (n=32), and 3y (n=15) in BM was 12%, 8%, and 7%. There was no significant difference in MRD levels in pts by prior tx status. However, pts with no del17p tended to have less residual disease measured by FC than pts with del17p. For example, at 2y MRD levels in PB were 6.4% vs 16% and in BM 4.7% vs 11.1%, respectively (P =0.02). At 3y one patient with no del17p achieved near MRD negativity in PB at 0.018%, and MRD negativity in the BM at 0.007%. CONCLUSION: With continued therapy 95% of pts achieved a response by iwCLL criteria and the depth of response improved with 21% CRs irrespective of the presence of del17p. However, all patients remained MRDpositive. With a median f/u of 36 mo, responses were durable in the majority of pts, with secondary resistance developing in 8% of pts. Research supported by the Intramural Research Program of NHLBI. We thank our patients for participation. We acknowledge Pharmacyclics for providing study drug. Disclosures Off Label Use: Ibrutinib is approved for CLL patients with relapsed refractory disease and patients with deletion 17p CLL. Some of the patients on this abstract from this clinical trial are treatment naive CLL patients without 17p deletion. . Wiestner:Pharmacyclics: Research Funding.

INTRODUCTION: Ibrutinib is approved for treatment (tx) of CLL in patients (pts) with previously treated disease and CLL with deletion (del) 17p. It has shown substantial improvements in progression free survival (PFS) and overall survival (OS) with a tolerable safety profile. Atrial fibrillation (Afib) has been observed in pts treated with ibrutinib, particularly in pts with cardiac risk factors, acute infections, and history of Afib. In the RESONATE study 3% of pts on ibrutinib developed Afib (median follow-up (f/u) 8.6 months (mo)) while 1% of pts on ofatumumab (median f/u 5.3 mo) developed Afib. Here we assessed the incidence of Afib in an independent cohort of pts with long f/u enrolled in our investigator-initiated trial of single agent ibrutinib. PATIENTS AND METHODS: This phase II trial (NCT01500733) enrolled 86 pts (Cohort 1: ≥ 65 years old (yo) without del 17p (n=35); Cohort 2: ≥ 18 yo with presence of del 17p (n=51)) who were treated with ibrutinib 420 mg daily continuously. Treatment-naive and previously treated pts in need of treatment (tx) were eligible. Safety data for Afib was compiled on all pts who received tx. All pts who developed Afib (per patient report or incidental finding) stopped ibrutinib therapy and underwent a cardiology evaluation which may have included an echocardiogram, stress test, and/or holter monitor at the discretion of the evaluating cardiologist. The annualized exposure adjusted incidence rate of Afib was estimated and compared between subgroups. RESULTS: At a median follow-up of 28 mo, 14 (16%) of 86 patients were found to have Afib while on study, 11 pts were ≥65 yo; 3 pts < 65 yo. In 9 (10%) pts this was the first recorded event, while 5 (6%) had a prior history of Afib. One patient developed Afib during pneumonia and in all other pts no contributing factors were identified. The median time to the first event on study was 18.24 (IQR: 10.8-26.0) mo. The annualized incidence was 0.052 (95% CI, 0.024- 0.099) events per person-year of treatment exposure among pts (n=81) without a prior history of Afib, 0.061 (95% CI: 0.025-0.126) in pts ≥65 yo (n=52), and 0.035 (95% CI: 0.004-0.125) in pts In 11 (79%) of 14 pts Afib was grade 2, and in 3 (21%) grade 3. The grade 3 events required hospitalization and control of Afib through intravenous medications. All 3 pts had resolution of Afib and completed cardiology evaluation prior to restarting ibrutinib at a lower dose (280 mg), one received only aspirin (ASA) 81 mg, one received ASA 81 mg and an antiarrhythmic (sotalol), and one patient was anticoagulated with apixaban. Of 11 pts with grade 2 events, 6 (55%) pts currently do not have any symptoms or EKG findings of Afib, 3 (27%) pts intermittently have symptoms or EKG findings of Afib, and 2 (18%) pts have ongoing Afib. All of these 11 pts restarted ibrutinib at the same dose (420 mg); 5 received ASA 81 mg, 2 were on dabigatran transiently and then continued ASA 81 mg, and the other 4 pts started apixiban. F/u on apixiban ranges from 7-17 mo with no bleeding-related adverse events grade >1. CONCLUSION: The rate of Afib in this study at 16% is higher than previously reported, likely due to longer f/u. Indeed, the estimated Afib rate at 17 mo in RESONATE was 5.1%, similar to 5.6% at the same timepoint in our study. The annualized incidence rate of Afib in our study at 0.052 (95% CI, 0.024- 0.099) is higher than the estimated rate of 0.0124 per person-year in the general population (Schnabel et al, Lancet 2015). Given that the rate of Afib is higher in illness, longer follow-up in randomized studies will be needed to distinguish disease from drug-related factors. Notably, none of our pts had to discontinue ibrutinib because of Afib. Furthermore, there is currently no evidence that the severity of Afib in pts on ibrutinib differs from the general population. Given that the majority of our patients have del 17p and/or previously treated disease we feel that the risk-benefit profile favors continued ibrutinib treatment. In a small number of pts and with limited duration of observation we have not noted any serious bleeding complications in pts on ibrutinib and concurrent apixaban or 81 mg ASA. Research supported by the Intramural Research Program of NHLBI. We thank our patients for participation. We acknowledge Pharmacyclics for providing study drug. Disclosures Wiestner: Pharmacyclics: Research Funding.

Maestría en Educación con Campo en Desarrollo Curricular