Bridging horizons beyond CIRCULATE-Japan: a new paradigm in molecular residual disease detection via whole genome sequencing-based circulating tumor DNA assay

Circulating tumor DNA (ctDNA) is the fraction of cell-free DNA in patient blood that originates from a tumor. Advances in DNA sequencing technologies and our understanding of the molecular biology of tumors have increased interest in exploiting ctDNA to facilitate detection of molecular residual disease (MRD). Analysis of ctDNA as a promising MRD biomarker of solid malignancies has a central role in precision medicine initiatives exemplified by our CIRCULATE-Japan project involving patients with resectable colorectal cancer. Notably, the project underscores the prognostic significance of the ctDNA status at 4 weeks post-surgery and its correlation to adjuvant therapy efficacy at interim analysis. This substantiates the hypothesis that MRD is a critical prognostic indicator of relapse in patients with colorectal cancer. Despite remarkable advancements, challenges endure, primarily attributable to the exceedingly low ctDNA concentration in peripheral blood, particularly in scenarios involving low tumor shedding and the intrinsic error rates of current sequencing technologies. These complications necessitate more sensitive and sophisticated assays to verify the clinical utility of MRD across all solid tumors. Whole genome sequencing (WGS)-based tumor-informed MRD assays have recently demonstrated the ability to detect ctDNA in the parts-per-million range. This review delineates the current landscape of MRD assays, highlighting WGS-based approaches as the forefront technique in ctDNA analysis. Additionally, it introduces our upcoming endeavor, WGS-based pan-cancer MRD detection via ctDNA, in our forthcoming project, SCRUM-Japan MONSTAR-SCREEN-3.

Subcutaneous epcoritamab monotherapy in Japanese adults with relapsed/refractory diffuse large B-cell lymphoma

Epcoritamab is a subcutaneously administered CD3xCD20 bispecific Ab that showed deep, durable responses with a manageable safety profile in patients with relapsed or refractory (R/R) diffuse large B-cell lymphoma (DLBCL) in the global multicenter pivotal phase II trial EPCORE NHL-1. Here, we present results from the similar EPCORE NHL-3 phase I/II trial evaluating epcoritamab monotherapy in Japanese patients with R/R CD20+ B-cell non-Hodgkin's lymphoma previously treated with two or more lines of therapy. Epcoritamab was dosed subcutaneously in 28-day cycles; once weekly during cycles 1-3, every 2 weeks during cycles 4-9, and every 4 weeks from cycle 10 until disease progression or unacceptable toxicity. Step-up dosing and cytokine release syndrome (CRS) prophylaxis were used during treatment cycle 1. As of January 31, 2022, 36 patients received treatment with 48 mg epcoritamab monotherapy. At a median follow-up of 8.4 months, overall response and complete response rates by independent review committee were 55.6% and 44.4%, respectively. The median duration of response, duration of complete response, and overall survival were not reached at the time of data cut-off. The most common treatment-emergent adverse events of any grade were CRS (83.3%), injection-site reactions (69.4%), infections (44.4%), neutropenia (38.9%), hypokalemia (27.8%), and decreased lymphocyte count (25.0%). Cytokine release syndrome occurrence was predictable; events were primarily low grade (grade 1-2), all resolved, and none led to treatment discontinuation. These encouraging results are consistent with previous findings and support the ongoing clinical evaluation of epcoritamab for the treatment of R/R DLBCL, including in earlier treatment lines.

Selective MCL-1 inhibitor ABBV-467 is efficacious in tumor models but is associated with cardiac troponin increases in patients

BACKGROUND

MCL-1 is a prosurvival B-cell lymphoma 2 family protein that plays a critical role in tumor maintenance and survival and can act as a resistance factor to multiple anticancer therapies. Herein, we describe the generation and characterization of the highly potent and selective MCL-1 inhibitor ABBV-467 and present findings from a first-in-human trial that included patients with relapsed/refractory multiple myeloma (NCT04178902).

METHODS

Binding of ABBV-467 to human MCL-1 was assessed in multiple cell lines. The ability of ABBV-467 to induce tumor growth inhibition was investigated in xenograft models of human multiple myeloma and acute myelogenous leukemia. The first-in-human study was a multicenter, open-label, dose-escalation study assessing safety, pharmacokinetics, and efficacy of ABBV-467 monotherapy.

RESULTS

Here we show that administration of ABBV-467 to MCL-1-dependent tumor cell lines triggers rapid and mechanism-based apoptosis. In vivo, intermittent dosing of ABBV-467 as monotherapy or in combination with venetoclax inhibits the growth of xenografts from human hematologic cancers. Results from a clinical trial evaluating ABBV-467 in patients with multiple myeloma based on these preclinical data indicate that treatment with ABBV-467 can result in disease control (seen in 1 patient), but may also cause increases in cardiac troponin levels in the plasma in some patients (seen in 4 of 8 patients), without other corresponding cardiac findings.

CONCLUSIONS

The selectivity of ABBV-467 suggests that treatment-induced troponin release is a consequence of MCL-1 inhibition and therefore may represent a class effect of MCL-1 inhibitors in human patients.

Activity of eftozanermin alfa plus venetoclax in preclinical models and patients with acute myeloid leukemia

Activation of apoptosis in malignant cells is an established strategy for controlling cancer and is potentially curative. To assess the impact of concurrently inducing the extrinsic and intrinsic apoptosis-signaling pathways in acute myeloid leukemia (AML), we evaluated activity of the TRAIL receptor agonistic fusion protein eftozanermin alfa (eftoza; ABBV-621) in combination with the B-cell lymphoma protein-2 selective inhibitor venetoclax in preclinical models and human patients. Simultaneously stimulating intrinsic and extrinsic apoptosis-signaling pathways with venetoclax and eftoza, respectively, enhanced their activities in AML cell lines and patient-derived ex vivo/in vivo models. Eftoza activity alone or plus venetoclax required death receptor 4/5 (DR4/DR5) expression on the plasma membrane but was independent of TP53 or FLT3-ITD status. The safety/tolerability of eftoza as monotherapy and in combination with venetoclax was demonstrated in patients with relapsed/refractory AML in a phase 1 clinical trial. Treatment-related adverse events were reported in 2 of 4 (50%) patients treated with eftoza monotherapy and 18 of 23 (78%) treated with eftoza plus venetoclax. An overall response rate of 30% (7/23; 4 complete responses [CRs], 2 CRs with incomplete hematologic recovery, and 1 morphologic leukemia-free state) was reported in patients who received treatment with eftoza plus venetoclax and 67% (4/6) in patients with myoblasts positive for DR4/DR5 expression; no tumor responses were observed with eftoza monotherapy. These data indicate that combination therapy with eftoza plus venetoclax to simultaneously activate the extrinsic and intrinsic apoptosis-signaling pathways may improve clinical benefit compared with venetoclax monotherapy in relapsed/refractory AML with an acceptable toxicity profile. This trial was registered at www.clinicaltrials.gov as #NCT03082209.

Clinical utility of genomic profiling of AML using paraffin-embedded bone marrow clots: HM-SCREEN-Japan 01

Next-generation sequencing of AML has identified specific genetic mutations in AML patients. Hematologic Malignancies (HM)-SCREEN-Japan 01 is a multicenter study to detect actionable mutations using paraffin-embedded bone marrow (BM) clot specimens rather than BM fluid in AML patients for whom standard treatment has not been established. The purpose of this study is to evaluate the presence of potentially therapeutic target gene mutations in patients with newly diagnosed unfit AML and relapsed/refractory AML (R/R-AML) using BM clot specimens. In this study, 188 patients were enrolled and targeted sequencing was undertaken on DNA from 437 genes and RNA from 265 genes. High-quality DNA and RNA were obtained using BM clot specimens, with genetic alterations successfully detected in 177 patients (97.3%), and fusion transcripts in 41 patients (23.2%). The median turnaround time was 13 days. In the detection of fusion genes, not only common fusion products such as RUNX1-RUX1T1 and KMT2A rearrangements, but also NUP98 rearrangements and rare fusion genes were observed. Among 177 patients (72 with unfit AML, 105 with R/R-AML), mutations in KIT and WT1 were independent factors for overall survival (hazard ratio = 12.6 and 8.88, respectively), and patients with high variant allele frequency (≥40%) of TP53 mutations had a poor prognosis. As for the detection of actionable mutations, 38% (n = 69) of patients had useful genetic mutation (FLT3-ITD/TKD, IDH1/2, and DNMT3A^R822 ) for treatment selection. Comprehensive genomic profiling using paraffin-embedded BM clot specimens successfully identified leukemic-associated genes that can be used as therapeutic targets.

BATF epigenetically and transcriptionally controls the activation program of regulatory T cells in human tumors

Regulatory T (T_reg) cells suppress effective antitumor immunity in tumor-bearing hosts, thereby becoming promising targets in cancer immunotherapy. Despite the importance of T_reg cells in tumor immunity, little is known about their differentiation process and epigenetic profiles in the tumor microenvironment (TME). Here, we showed that T_reg cells in the TME of human lung cancers harbored a completely different open chromatin profile compared with CD8⁺ T cells, conventional CD4⁺ T cells in the TME, and peripheral T_reg cells. The integrative sequencing analyses including ATAC, single-cell RNA, and single-cell ATAC sequencing revealed that BATF, IRF4, NF-κB, and NR4A were important transcription factors for T_reg cell differentiation in the TME. In particular, BATF was identified as a key regulator, which leveraged T_reg cell differentiation through epigenetically controlling activation-associated gene expression, resulting in the robustness of T_reg cells in the TME. The single-cell sequencing approaches also revealed that tissue-resident and tumor-infiltrating T_reg cells followed a common pathway for differentiation and activation in a BATF-dependent manner heading toward T_reg cells with the most differentiated and activated phenotypes in tissues and tumors. BATF deficiency in T_reg cells remarkably inhibited tumor growth, and high BATF expression was associated with poor prognosis in lung cancer, kidney cancer, and melanoma. These findings indicate one of the specific chromatin remodeling and differentiation programs of T_reg cells in the TME, which can be applied in the development of T_reg cell-targeted therapies.

Asciminib vs bosutinib in CML patients pretreated with ≥2 tyrosine kinase inhibitors: Results from the Japanese subgroup analysis of ASCEMBL study

Asciminib, a first-in-class, allosteric inhibitor of BCR-ABL1 that acts by STAMP (Specifically Targeting the ABL Myristoyl Pocket), is a novel therapeutic option for patients with chronic myeloid leukemia (CML). In the global, phase 3, open-label ASCEMBL study in patients with CML in chronic phase (CML-CP) pretreated with ≥2 tyrosine kinase inhibitors (TKIs) (NCT03106779), asciminib (40 mg twice-daily) demonstrated significant superiority over the ATP-competitive TKI bosutinib (500 mg once daily) for the primary endpoint of major molecular response (MMR; BCR::ABL1 transcript levels on the international scale [BCR::ABL1^IS ] ≤0.1%) at week 24. Here, we report results from a descriptive subgroup analysis of Japanese patients enrolled in ASCEMBL study (data cut-off: May 25, 2020). Overall, 16 Japanese patients were randomized (asciminib, n = 13; bosutinib, n = 3). At week 24, the MMR rate with asciminib was 30.8% (4/13; 95% confidence interval [CI], 9.09-61.43). BCR::ABL1^IS ≤1% and complete cytogenic response (CCyR) at week 24 were 61.5% (8/13 patients) and 50.0% (4/8 patients), respectively. In the bosutinib group, no patient achieved MMR, CCyR, or BCR::ABL1^IS ≤1%, but results were limited by the low number of patients. The safety profile of asciminib was comparable to that previously observed in the overall study population. Findings from this Japanese subgroup analysis of the ASCEMBL study support the use of asciminib for the treatment of Japanese patients with CML-CP previously treated with ≥2 TKIs. ClinicalTrials.gov Identifier: NCT03106779.

Abstract 5185: First in human trial of off-the shelf iPS derived anti-GPC3 NK cells for recurrent ovarian clear cell carcinoma with peritoneal dissemination

Background: The development of chimeric antigen receptor (CAR) T cell therapy has introduced an effective strategy to guide and promote the immune response. Also, gene-engineering NK cells to express an exogenous CAR receptor allows the innate anti-tumor ability of NK cells to be directed against target tumor antigen. However, these autologous applications are limited by toxicities, restricted trafficking and infiltration into tumor, suboptimal persistence, and exhausted status of immune cells that may cause manufacturing failure. One approach to overcome those limitations is the development of “off-the-shelf” iPS-cell sources. The iCAR-ILC-N101 is an allogeneic human leukocyte antigen (HLA)-homozygous induced pluripotent stem cell (iPSC)-derived anti-glypican-3 (GPC3) CAR-expressing innate lymphoid cells/natural killer cell (ILC/NK), which has both antigen-specific and NK activating receptor-mediated cytotoxicity. The iCAR-ILC-N101 is produced from the established iPSC strain QHJI01s04, and there is theoretically no risk of developing graft-versus host disease because the product dose not have T cell receptor. The product has a relevant living period in the body, thereby has little concern about residual toxicity and reduces systemic side effects by topical treatment. GPC3 is a cancer-specific membranous protein that is expressed in hepatoblastoma, hepatocellular carcinoma and ovarian clear cell carcinoma (OCCC) but is not expressed in normal tissue. OCCC is a relatively rare malignancy and is associated with poor prognosis. Intraperitoneal administration of iCAR-ILC-N101 is expected to show antitumor activity for OCCC patients with peritoneal dissemination that express GPC3 and reduce systemic side effects, thereby ensuring safety and improving therapeutic efficacy. Preclinical study showed that intraperitoneal injection of iCAR-ILC-N101 for GPC3-positive ovarian tumor-bearing immunodeficient mouse model showed suppressed tumor growth.

Method: This is a first-in human phase 1 study to evaluate safety, toxicity and efficacy of the iCAR-ILC-N101 in patients with GPC3-positive advanced or recurrent OCCC harboring peritoneal dissemination. Major inclusion criteria include histologically diagnosed GPC3-positive advanced or recurrent OCCC with peritoneal dissemination who are resistant to standard therapy and have matched HLA-A24 or B52. The study includes 3 cohorts (cohort -1, 0.5x106 cells/kg; cohort 1, 1x106 cells/kg; cohort 2, 3x106 cells/kg) and starts with cohort 1. The iCAR-ILC-N101 is administered intraperitoneally once a week for 4 weeks; for the first patient in each cohort, patient is observed for 14 days for safety evaluation after the first administration and then receive iCAR-ILC-N101 on day15 and 22. Enrollment initiated in July 2021 and one patient was enrolled. No dose-limiting toxicity was observed. Clinical trial registry number: jRCT2033200431

Citation Format: Kenichi Harano, Shin Kaneko, Tetsuya Nakatsura, Junichiro Yuda, Nozomu Fuse, Akihiro Sato, Reiko Watanabe, Genichiro Ishii, Toru Mukohara, Hiroshi Tanabe, Yukiko Ishiguro, Hideki Furuya, Masashi Wakabayashi, Miki Fukutani, Manami Shimomura, Tatsuki Ueda, Shoichi Iriguchi, Ayako Kumagai, Kengo Nakagoshi, Aki Sasaki, Toshihiko Doi. First in human trial of off-the shelf iPS derived anti-GPC3 NK cells for recurrent ovarian clear cell carcinoma with peritoneal dissemination [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5185.

Molecular Classification and Overcoming Therapy Resistance for Acute Myeloid Leukemia with Adverse Genetic Factors

The European LeukemiaNet (ELN) criteria define the adverse genetic factors of acute myeloid leukemia (AML). AML with adverse genetic factors uniformly shows resistance to standard chemotherapy and is associated with poor prognosis. Here, we focus on the biological background and real-world etiology of these adverse genetic factors and then describe a strategy to overcome the clinical disadvantages in terms of targeting pivotal molecular mechanisms. Different adverse genetic factors often rely on common pathways. KMT2A rearrangement, DEK-NUP214 fusion, and NPM1 mutation are associated with the upregulation of HOX genes. The dominant tyrosine kinase activity of the mutant FLT3 or BCR-ABL1 fusion proteins is transduced by the AKT-mTOR, MAPK-ERK, and STAT5 pathways. Concurrent mutations of ASXL1 and RUNX1 are associated with activated AKT. Both TP53 mutation and mis-expressed MECOM are related to impaired apoptosis. Clinical data suggest that adverse genetic factors can be found in at least one in eight AML patients and appear to accumulate in relapsed/refractory cases. TP53 mutation is associated with particularly poor prognosis. Molecular-targeted therapies focusing on specific genomic abnormalities, such as FLT3, KMT2A, and TP53, have been developed and have demonstrated promising results.

[Tyrosine kinase inhibitors induce production of BCR-ABLIns35bp splicing variants via inhibition of RNA polymerase II on genomic BCR-ABL and cause unachieved deep molecular response and fluctuating minimal residual disease]

Deep sequence analysis for BCR-ABL revealed that native BCR-ABL decreased slowly after an exponential decrease within three months of tyrosine kinase inhibitor (TKI) treatment. BCR-ABL^Ins35bp was present at diagnosis and increased to account for 15-30% of total BCR-ABL when IS BCR-ABL was reduced to 1%. Native BCR-ABL and BCR-ABL^Ins35bp correspond to early relapse and fluctuating minimal residue disease, respectively, in the STOP-TKI trial. These findings highlight the clinical significance of quantifying BCR-ABL^Ins35bp. We discovered pseudosplice sites at both ends of 35 bp within ABL intron 8, and TKI off-target effect inhibited RNAPII S2P and reduced native BCR-ABL expression but induced BCR-ABL^Ins35bp mis-splicing.

Incidence of refractory cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation

Post-transplant cytomegalovirus (CMV) disease can be almost completely avoided by current infection control procedures. However, CMV reactivation occurs in more than half of patients, and some patients can develop clinically resistant CMV infections. Whether resistance is due to the host's immune status or a viral resistance mutation is challenging to confirm. Therefore, a prospective observational analysis of refractory CMV infection was conducted in 199 consecutive patients who received allogeneic hematopoietic stem cell transplantation at a single institution. Among them, 143 (72%) patients received anti-CMV drugs due to CMV reactivation, and only 17 (8.5%) exhibited refractory CMV infection. These patients had clinically refractory infection. However, viral genome analysis revealed that only one patient exhibited a mutation associated with the anti-CMV drug resistance. Clinical resistance was mainly correlated with host immune factors, and the incidence of resistance caused by gene mutations was low at the early stage after a transplantation.

Phase 1 first-in-human study of ABBV-184 monotherapy in adult patients with previously treated acute myeloid leukemia or non-small cell lung cancer

TPS2674

Background: Survivin, a member of the inhibitor of apoptosis protein family, is an attractive therapeutic target in cancer, due to its broad expression in solid tumors and hematologic malignancies but limited expression in normal tissues. Elevated survivin expression is associated with an increased invasive phenotype and worse clinical outcomes. ABBV-184 is a first-in-class T-cell receptor (TCR)/anti-cluster of differentiation 3 (CD3) bispecific molecule. It is composed of a soluble TCR that binds to a survivin-derived peptide bound to the class I MHC allele HLA-A2:01 expressed on tumor cells and to the CD3 receptor on T cells. Preclinical data have demonstrated that treatment with ABBV-184 results in T-cell activation, proliferation, and redirected cytotoxicity of HLA-A2:01–positive target cell lines. This first-in-human trial evaluates ABBV-184 monotherapy in patients with previously treated acute myeloid leukemia (AML) or non-small cell lung cancer (NSCLC). Methods: Patients (≥18 years, Eastern Cooperative Oncology Group performance status ≤2, HLA-A2:01 restricted genotype) with relapsed or refractory AML or NSCLC are currently enrolling in this phase 1 multicenter, open-label trial (NCT04272203), which includes parallel dose-escalation and dose-expansion phases for both diseases. Primary objectives are to determine the recommended phase 2 dose (RP2D) of ABBV-184 (dose escalation) and to assess its preliminary efficacy (dose expansion). Secondary objectives include safety, tolerability, pharmacokinetics (PK), and immunogenicity assessments (dose escalation and dose expansion) and duration of response (dose expansion). Patients will receive intravenous infusion of ABBV-184 once weekly. Dose escalation of ABBV-184 is guided by a Bayesian optimal interval design and the RP2D will be determined on the basis of clinical safety, PK, and pharmacodynamic data. For patients with AML, disease assessment is performed according to modified European LeukemiaNet-International Working Group criteria. For patients with NSCLC, response will be assessed using Response Evaluation Criteria In Solid Tumors (RECIST) v1.1 and immune RECIST. Treatment can continue until disease progression or intolerable toxicity. Biomarker assessments will include longitudinal profiling of peripheral blood immune cells and cytokines, analysis of HLA-A2 and survivin levels on AML bone marrow blasts and NSCLC tumor biopsies, and retrospective correlations of biomarker data with antitumor activity. Enrollment initiated in Sep 2020, with 7 patients enrolled as of Jan 2021. Clinical trial information: NCT04272203.

Brentuximab vedotin maintenance after autologous stem cell transplantation for refractory gray zone lymphoma with long-term remission

Gray zone lymphoma (GZL) is a rare type of B-cell lymphoma characterized by features of both diffuse large B-cell lymphoma and classical Hodgkin lymphoma (cHL). The prognosis of GZL is poorer than that of cHL and mediastinal large B-cell lymphoma. However, an optimal treatment strategy for relapsed/refractory (R/R) GZL has not been established in the clinical setting. The current study reported an excellent clinical response in a patient with R/R CD30-positive GZL who received brentuximab vedotin (BV) maintenance after autologous stem cell transplantation (ASCT). Although the patient was resistant to prior treatments, BV maintenance after ASCT achieved long-term remission. Hence, BV was determined to be a safe and effective therapeutic option for CD30-positive R/R GZL.

Molecular remission after combination therapy with blinatumomab and ponatinib with relapsed/refractory Philadelphia chromosome-positive acute lymphocytic leukemia: two case reports

Background

The outcomes of Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) can improve with allogeneic hematopoietic stem cell transplantation (HSCT) during the first complete remission after treatment with a tyrosine kinase inhibitor (TKI) combined with chemotherapy. However, frail patients who are not eligible for allogeneic HSCT or those with TKI-resistant mutations within the BCR–ABL kinase domain have a poor clinical course. Blinatumomab (BLIN) is a bispecific T-cell engager antibody construct that directs cytotoxic T cells to CD19-expressing B-ALL cells. To date, only a few studies have shown the safety and efficacy of Blinatumomab (BLIN) + TKI combination therapy for relapsed/refractory (R/R) Ph+ ALL. Here we report the case of two patients with R/R Ph+ ALL who were treated with BLIN + TKI with durable molecular response.

Case presentation

Patient 1: A 69-year-old Japanese male with R/R Ph+ ALL was treated with conventional chemotherapy and dasatinib in April 2016. In May 2018, he developed molecular relapse due to the acquisition of T315I during dasatinib maintenance therapy. Thereafter, he achieved molecular complete remission (mCR) after switching from dasatinib to ponatinib. However, he developed a second relapse after the emergence of triple compound mutations (G250E/D276G/T315I) in November 2018. He subsequently received a total of nine cycles of BLIN and ponatinib combination therapy, which resulted in sustained mCR without any adverse events. Patient 2: A 69-year-old Japanese female with R/R Ph+ ALL was treated with chemotherapy and imatinib in April 2008. She developed molecular relapse due to the emergence of the T315I mutation in October 2017. She achieved mCR after switching from imatinib to ponatinib. However, she developed a second relapse after acquiring ABL exon4 skipping in addition to T315I. She subsequently received a total of seven cycles of BLIN and ponatinib combination therapy, which resulted in sustained mCR.

Conclusion

In our two cases, BLIN + ponatinib combination therapy was highly effective for R/R Ph+ ALL without any incidence of severe adverse events. Further studies with larger cohorts are warranted to validate the safety and efficacy of this potent combination therapy.

Emerging Immunotherapy for Acute Myeloid Leukemia

Several immune checkpoint molecules and immune targets in leukemic cells have been investigated. Recent studies have suggested the potential clinical benefits of immuno-oncology (IO) therapy against acute myeloid leukemia (AML), especially targeting CD33, CD123, and CLL-1, as well as immune checkpoint inhibitors (e.g., anti-PD (programmed cell death)-1 and anti-CTLA4 (cytotoxic T-lymphocyte-associated protein 4) antibodies) with or without conventional chemotherapy. Early-phase clinical trials of chimeric antigen receptor (CAR)-T or natural killer (NK) cells for relapsed/refractory AML showed complete remission (CR) or marked reduction of marrow blasts in a few enrolled patients. Bi-/tri-specific antibodies (e.g., bispecific T-cell engager (BiTE) and dual-affinity retargeting (DART)) exhibited 11-67% CR rates with 13-78% risk of cytokine-releasing syndrome (CRS). Conventional chemotherapy in combination with anti-PD-1/anti-CTLA4 antibody for relapsed/refractory AML showed 10-36% CR rates with 7-24 month-long median survival. The current advantages of IO therapy in the field of AML are summarized herein. However, although cancer vaccination should be included in the concept of IO therapy, it is not mentioned in this review because of the paucity of relevant evidence.

[Successful treatment with silver nitrate chemical cauterization for paronychia and granulation in a patient with chronic lymphocytic leukemia undergoing ibrutinib therapy]

A 72-year-old man with leukocytosis, anemia, and lymphadenopathy was diagnosed with chronic lymphocytic leukemia (CLL) in August 2017 and was carefully monitored in a "watch-and-wait" manner until it became an "active disease." Ibrutinib (IBR) was initiated orally in July 2018 at a dose of 420 mg/day after disease progression due to chromosome 17p deletion (del 17p). The patient showed partial response after transient lymphocytosis while on IBR treatment. IBR induces paronychia and skin disorder due to the disruption of disulfide bonds between cysteine and inhibition of epidermal growth factor receptor due to the off-target effect. This results in reduced quality of life. In February 2019, paronychia (grade 1) developed in the patient's right foot's first toe; hence, topical gentamicin and taping therapy were performed. However, the symptoms persisted without any improvements. In July 2019, paronychia/granulation (grade 2) was aggravated and successfully treated with silver nitrate chemical cauterization and taping therapy. The patient was continuously treated with 420 mg/day IBR without dose reduction or discontinuation, resulting in successful disease control of CLL with del 17p.

[Disseminated aspergillosis due to Aspergillus udagawae during immunosuppressive treatment for myelodysplastic syndrome]

An 80 year old male who had received immunosuppressive therapy for myelodysplastic syndrome presented with fever, fatigue, and elevated serum Aspergillus antigen. Computed tomography revealed infiltrative shadows in the left lower lung and subcutaneous nodules. A polymerase chain reaction assay from lung and subcutaneous nodule samples identified the presence Aspergillus udagawae. A. udagawae is a cryptic species that shares similar morphological characteristics with A. fumigatus but genetically differs from the latter in its susceptibility to antifungal drugs. When immunosuppressed patients with hematological malignancies develop disseminated aspergillosis, biopsy and fungal tests are crucial to identify the causative fungus, including cryptic species, for deciding the appropriate therapeutic intervention.

Tyrosine kinase inhibitors induce alternative spliced BCR-ABLIns35bp variant via inhibition of RNA polymerase II on genomic BCR-ABL

To elucidate dynamic changes in native BCR-ABL and alternatively spliced tyrosine kinase inhibitor (TKI)-resistant but function-dead BCR-ABL^Ins35bp variant, following commencement or discontinuation of TKI therapy, each transcript was serially quantified in patients with chronic myeloid leukemia (CML) by deep sequencing. Because both transcripts were amplified together using conventional PCR system for measuring International Scale (IS), deep sequencing method was used for quantifying such BCR-ABL variants. At the initial diagnosis, 7 of 9 patients presented a small fraction of cells possessing BCR-ABL^Ins35bp , accounting for 0.8% of the total IS BCR-ABL, corresponding to actual BCR-ABL^Ins35bp value of 1.1539% IS. TKI rapidly decreased native BCR-ABL but not BCR-ABL^Ins35bp , leading to the initial increase in the proportion of BCR-ABL^Ins35bp . Thereafter, both native BCR-ABL and BCR-ABL^Ins35bp gradually decreased in the course of TKI treatment, whereas small populations positive for TKI-resistant BCR-ABL^Ins35bp continued fluctuating at low levels, possibly underestimating the molecular response (MR). Following TKI discontinuation, sequencing analysis of 54 patients revealed a rapid relapse, apparently derived from native BCR-ABL⁺ clones. However, IS fluctuating at low levels around MR4.0 marked a predominant persistence of cells expressing function-dead BCR-ABL^Ins35bp , suggesting that TKI resumption was unnecessary. We clarified the possible mechanism underlying mis-splicing BCR-ABL^Ins35bp , occurring at the particular pseudo-splice site within intron8, which can be augmented by TKI treatment through inhibition of RNA polymerase II phosphorylation. No mutations were found in spliceosomal genes. Therefore, monitoring IS functional BCR-ABL extracting BCR-ABL^Ins35bp would lead us to a correct evaluation of MR status, thus determining the adequate therapeutic intervention.

[Vascular adverse events of ponatinib during treatment of Philadelphia chromosome-positive leukemia: a retrospective single-institution analysis]

Ponatinib (PON) is a key drug for patients with second tyrosine kinase inhibitor (TKI)-resistant/intolerant Philadelphia chromosome-positive leukemia (Ph+ leukemia); however, the occurrence of vascular adverse events (VAEs) in patients treated with PON should be carefully monitored. A retrospective analysis involving seven patients treated with PON was conducted to elucidate the incidence rate and risk factor for the development of VAEs. In the present study, risk assessment and monitoring of VAEs were performed using SCORE Risk Chart and Suita Score (10-year risk for fatal cardiovascular event), respectively. Despite the prophylactic use of aspirin, cerebral infarction and unstable angina occurred in two patients. By contrast, deep vein thrombosis did not improve in a patient treated with edoxaban. Our data suggest that patients with Ph+ leukemia possessing risk factors, medical history of lifestyle diseases, and administration of long-term second TKI treatment require careful monitoring of VAEs and therapeutic intervention to lifestyle diseases.

[Hairy cell leukemia complicated by bone marrow necrosis following cladribine administration]

Classic hairy cell leukemia (classic HCL) is a rare disease associated with indolent mature B-cell lymphoma. A 50-year-old man presented with pancytopenia for 3 years and was diagnosed with classic HCL because his lymphoid cells showed a hairy morphology with oval nuclei and indistinct nucleoli both in the peripheral blood and bone marrow (BM) smears. Flow cytometric analysis revealed that these cells expressed CD11c, CD25, and CD103, and the Sanger sequence method detected BRAF V600E mutation. Cladribine (0.09 mg/kg/day) was initiated for 7 days via continuous intravenous injection. On day 13, the patient died from bloodstream infection caused by methicillin-resistant Staphylococcus epidermidis. Autopsy findings revealed BM necrosis without residual leukemia cells caused by classic HCL, severe infection, and agents, such as cladribine and granulocyte-colony stimulating factor; however, its cause remained undetermined. Both early diagnosis and immediate clinical intervention are required to improve the clinical outcomes in classic HCL. The cause of hematopoiesis disturbance should also be identified using BM biopsy or magnetic resonance imaging before initiating treatment in classic HCL with severe pancytopenia.

Persistent detection of alternatively spliced BCR-ABL variant results in a failure to achieve deep molecular response

Treatment with tyrosine kinase inhibitors (TKI) may sequentially induce TKI‐resistant BCR‐ABL mutants in chronic myeloid leukemia (CML). Conventional PCR monitoring of BCR‐ABL is an important indicator to determine therapeutic intervention for preventing disease progression. However, PCR cannot separately quantify amounts of BCR‐ABL and its mutants, including alternatively spliced BCR‐ABL with an insertion of 35 intronic nucleotides (BCR‐ABL^Ins35bp) between ABL exons 8 and 9, which introduces the premature termination and loss of kinase activity. To assess the clinical impact of BCR‐ABL mutants, we performed deep sequencing analysis of BCR‐ABL transcripts of 409 samples from 37 patients with suboptimal response to frontline imatinib who were switched to nilotinib. At baseline, TKI‐resistant mutations were documented in 3 patients, whereas BCR‐ABL^Ins35bp was detected in all patients. After switching to nilotinib, both BCR‐ABL and BCR‐ABL^Ins35bp became undetectable in 3 patients who attained complete molecular response (CMR), whereas in the remaining all 34 patients, BCR‐ABL^Ins35bp was persistently detected, and minimal residual disease (MRD) fluctuated at low but detectable levels. PCR monitoring underestimated molecular response in 5 patients whose BCR‐ABL^Ins35bp was persisted, although BCR‐ABL^Ins35bp does not definitively mark TKI resistance. Therefore, quantification of BCR‐ABL^Ins35bp is useful for evaluating “functional” MRD and determining the effectiveness of TKI with accuracy.

The ordered acquisition of Class II and Class I mutations directs formation of human t(8;21) acute myelogenous leukemia stem cell

The cellular properties of leukemia stem cells (LSCs) are achieved at least through Class I and Class II mutations that generate signals for enhanced proliferation and impaired differentiation, respectively. Here we show that in t(8;21) acute myelogenous leukemia (AML), hematopoietic stem cells (HSCs) transform into LSCs via definitively-ordered acquisition of Class II (AML1/ETO) and then Class I (c-KIT mutant) abnormalities. Six t(8;21) AML patients with c-KIT mutants maintaining > 3 years of complete remission were analyzed. At diagnosis, all single LSCs had both AML1/ETO and c-KIT mutations. However, in remission, 16 out of 1,728 CD34(+)CD38(-) HSCs and 89 out of 7,187 single HSC-derived myeloerythroid colonies from these patients had AML1/ETO, whose breakpoints were identical to those found in LSCs. These cells had wild-type c-KIT, which expressed AML1/ETO at a low level, and could differentiate into mature blood cells, suggesting that they may be the persistent preleukemic stem cells. Microarray analysis suggested that mutated c-KIT signaling provides LSCs with enhanced survival and proliferation. Thus, in t(8;21) AML, the acquisition of AML1/ETO is not sufficient, and the subsequent upregulation of AML1/ETO and the additional c-KIT mutant signaling are critical steps for transformation into LSCs.

Successful treatment of invasive zygomycosis based on a prompt diagnosis using molecular methods in a patient with acute myelogenous leukemia

Zygomycosis is a lethal and invasive mold infection that is often associated with hematological malignancies. The keys for successful treatment include making a rapid diagnosis and appropriately administering antifungal agents. We herein report the early diagnosis of a case of zygomycosis in a patient with acute myeloid leukemia using a deoxyribonucleic acid sequence analysis. We successfully performed allogeneic hematopoietic stem cell transplantation with the use of high-dose liposomal amphotericin B and granulocyte transfusion.

Hepatic portal venous gas associated with severe graft-versus-host disease of the gastrointestinal tract

We report a 67-year-old woman who was diagnosed with hepatic portal venous gas associated with severe graft-versus-host disease (GVHD) of the gastrointestinal tract. The patient received allogenic peripheral blood stem cell transplantation from a haploidentical son against Philadelphia chromosome-positive acute lymphocytic leukemia. The patient developed grade 3 intestinal GVHD on day 90 from the transplantation. On day 149, she presented septic shock and computed tomography (CT) scan revealed hepatic portal venous gas (HPVG); an ileocecal resection was performed immediately. The damage of gastrointestinal mucosa by GVHD resulted in the invasion of gas-producing bacteria. Although HPVG-associated gastrointestinal GVHD is extremely rare, we should pay special attention to this pathogenesis.

Fournier's gangrene in a patient receiving treatment for idiopathic thrombocytopenic purpura

We report the case of a 68-year-old man who was diagnosed with Fournier's gangrene (FG), which developed during immunosuppresive treatment for idiopathic thrombocytopenic purpura (ITP). The patient was administered steroids for ITP but on the 36th day, he developed FG and septic shock. We initiated antibiotic treatment and drained a periproctal abscess immediately. On day 53, extensive drainage to progressive FG and a splenectomy was performed, following which both FG and thrombocytopenia improved. This is the first case of FG has developing in a ITP patient. It appears that high-dose immunoglobulin therapy and splenectomy should be considered earlier especially for a patient complicated with FG.

[A case report of emergency mitral valve replacement for infective endocarditis in pregnancy]

Infective endocarditis is extremely rare in early pregnancy. We report an emergency mitral valve replacement performed successfully on a 16 week pregnant woman for infective endocarditis without preexisting heart disease. On admission, the patient was in acute heart failure, and the fetus had been already dead. Induced abortion was performed uneventfully 6 days after the cardiac operation.