DeAngelo, Daniel J.

Background and Rationale: Systemic mastocytosis (SM) is a clonal hematologic neoplasm characterized by abnormal accumulation of mast cells which can lead to symptoms related to mast cell degranulation and/or, in the case of advanced systemic mastocytosis (AdvSM), organ dysfunction due to mast cell infiltration. AdvSM is a category of SM comprised of aggressive systemic mastocytosis (ASM), mast cell leukemia (MCL), and SM with an associated hematologic neoplasm (SM-AHN). Among these, SM-AHN is the most common subtype, accounting for approximately 70% of AdvSM. A KIT D816V mutation found in up to 95% of SM cases is the primary oncogenic driver, making it a key therapeutic target. Avapritinib, a highly potent and selective inhibitor of D816V mutant KIT, has demonstrated high rates of rapid, deep, and durable responses in all AdvSM subtypes, including SM-AHN (Gotlib et al. Nature Medicine, 2021; DeAngelo et al., Nature Medicine, 2021). However, despite showing prolonged OS and low risk of progression of the SM component, some patients (20%) exhibit progression of the AHN component, including transformation to AML. In some patients, combination therapy with avapritinib and AHN-directed therapy may therefore be necessary for optimal control of SM-AHN. Hypomethylating agents (HMA) form the backbone of therapy for advanced myelodysplastic syndrome (MDS) and myelodysplastic/myeloproliferative neoplasm (MDS/MPN); hematologic neoplasms most likely to co-occur with SM in patients (pts) with SM-AHN. To date, the combination of HMA and KIT inhibitors has not been clinically evaluated. In this study, we aim to assess the safety and tolerability of the combination of avapritinib and decitabine in patients with SM-AHN. Study design and Methods: The primary objective of the study is to establish the recommended dose (RP2D) of avapritinib in combination with decitabine based on dose-limiting toxicity, overall safety, and clinical activity data. A dose evaluation steering committee (DESC) comprised of participating investigators will review the totality of safety and efficacy data to determine RP2D. Secondary endpoints include SM overall response rate by the end of 6 cycles by the m-IWG consensus criteria and proposed ECNM-AIM criteria (Gotlib et al., J Allergy Clin Immunol Pract, 2022) and incidence/frequency of adverse events. Exploratory endpoints include patient reported outcomes, PFS, OS, and correlative biomarkers linked to mast cell disease or AHN. Pts with a diagnosis of SM-AHN by the WHO 2022 criteria will be eligible for inclusion. Pts must have any of the following myeloid AHN per WHO 2022 criteria: MDS, CMML, MDS/MPN with neutrophilia, MDS/MPN with SF3B1 mutation and thrombocytosis, or MDS/MPN-NOS. Patients with MDS must have intermediate, high- or very-high risk by IPSS-R. Patients with very-low or low-risk MDS by IPSS-R must be intolerant/refractory to ESA or have serum EPO > 200 U/L. A baseline platelet count of ≥ 75 x 109/L and ≥ 25 x 109/L will be required for inclusion in the dose-finding and the dose-expansion phases, respectively. Key exclusion criteria include a diagnosis of AML, history of intracranial hemorrhage, prior treatment with avapritinib or decitabine with documented progression in SM or AHN component, respectively, or treatment with alternative KIT inhibitor or azacitidine within 4 weeks of study treatment initiation. In the dose finding part of the study, a Bayesian adaptive design will be employed to assess different doses of avapritinib (50 to 200 mg PO daily) in combination with fixed doses of decitabine (oral decitabine/cedazuridine: 35/100 mg/day or intravenous decitabine: 20 mg/m2/day on days 1-5) in a 28-day treatment cycle. Close attention will be paid to treatment-emergent thrombocytopenia with protocol-driven treatment holds and dose modification strategies employed when platelet count drops below 50 x 109/L. After RP2D is determined, an additional 10 patients will be enrolled in the dose expansion phase. Patients with platelet count ≥ 25 x 109/L and < 75 x 109/L, will receive lead-in dosing with decitabine or decitabine/cedazuridine with the ability to add avapritinib if sufficient platelet thresholds are achieved. Planned correlative studies include serial single-cell multi-omics utilizing scDNA-seq and immunophenotyping to assess impact of combination treatment on a molecularly complex disease state. This study is currently open to accrual (NCT06327685).

Background and Significance: Systemic mastocytosis (SM) is a rare heterogeneous disease characterized by the aberrant accumulation of neoplastic mast cells (MC). In about 95% of adult patients, SM is driven by a gain-of-function mutation (D816V) in exon 17 of KIT. Advanced SM (AdvSM) is a life-threatening form of SM and includes three subtypes: aggressive SM (ASM), SM with an associated hematologic neoplasm (SM-AHN), and mast cell leukemia (MCL). Despite improvement in disease control with approval of tyrosine kinase inhibitors (TKIs), there is still unmet need for improved tolerability and efficacy in AdvSM treatments. Bezuclastinib, an oral and selective type 1 TKI that potently inhibits KIT D816V, is being studied in patients diagnosed with AdvSM in the Apex study (NCT04996875). Results from the Part 1 dose optimization portion of Apex were presented previously. Part 1 randomized 32 patients 1:1:1:1 to receive bezuclastinib at 50, 100, or 200 mg BID or 400 mg QD. Initial results from the Part 1 dose optimization portion of the Apex trial in patients with AdvSM demonstrated encouraging safety profile and signs of clinical activity, as well as deep reductions across biomarkers of MC burden including bone marrow MC burden, serum tryptase levels, and KIT D816V variant allele fraction (VAF). In addition, 94%, 93%, and 100% of patients demonstrated ≥50% reduction in serum tryptase, KIT D816V VAF, and bone marrow MC burden, respectively. Exposure achieved with 100 mg BID of bezuclastinib original formulation resulted in optimal efficacy and safety outcomes. 150 mg QD of an optimized formulation is expected to deliver bezuclastinib exposures consistent with the 100 mg BID of the original formulation. Part 2 is further evaluating the efficacy and safety of bezuclastinib in patients with AdvSM at the selected Part 2 dose of 150mg QD of the optimized formulation. Study Design and Methods: Apex is a multicenter, Phase 2 open-label study of bezuclastinib in patients with AdvSM as defined per the WHO criteria. Enrollment includes previously treated and treatment-naïve patients. Part 2 is enrolling approximately 65 patients including up to 15 patients without measurable mIWG C-findings. The Part 2 expansion portion of the Apex study is designed to evaluate the efficacy and safety of bezuclastinib in patients with AdvSM, including ASM, SM-AHN, or MCL. Key eligibility criteria include measurable disease (centrally adjudicated) according to modified IWG-MRT-ECNM criteria and clinically acceptable laboratory values including platelet count ≥50,000/µL. The primary efficacy endpoint of Part 2 is overall response rate (ORR = complete response [CR] + complete remission with partial hematologic recovery [CRh] + partial response [PR] + clinical improvement [CI]) per mIWG-MRT-ECNM criteria according to mIWG-MRT-ECNM response criteria and will be confirmed by a Central Response Review Committee. Secondary endpoints include further characterization of safety and tolerability, pure pathologic response, biomarker response (including changes in bone marrow MC burden, serum tryptase level, and KIT D816V mutational burden), duration of response, time to response, progression-free survival, and overall survival (OS). Apex Part 2 is actively enrolling. Study sites are enrolling in North America, Asia-Pacific, and Europe. In addition, a high-risk SM-AHN sub-study assessing the safety and feasibility of the combination of bezuclastinib 150 mg QD and azacitidine may enroll up to 20 patients who are currently receiving or indicated for azacitidine and have biopsy-proven SM with an associated high- or very high-risk myeloid neoplasm. Patients with SM-AHN from Part 1 or Part 2 who have demonstrated AHN progression may enroll in an additional rollover cohort to receive bezuclastinib with concomitant azacitidine or hydroxyurea.

Introduction: Inotuzumab ozogamicin (INO) is an antibody targeting CD22 conjugated with a cytotoxic antitumor antibiotic (calicheamicin) approved for treatment of relapsed/refractory CD22 positive B-cell acute lymphoblastic leukemia (ALL) (Kantarjian et al. NEJM 2017). CD22 is expressed on the surface of lymphoblasts in ALL (~95%). Young adult patients (pts) 18-39 years (yrs) treated on the pediatric regimen CALGB 10403 resulted in a 3-yr event-free survival (EFS) of 59% (95% CI: 52-67%) and an estimated 3-yr overall survival (OS) of 73% (95% CI: 68-78%) (Stock et al. Blood 2019). Alliance A041501(NCT03150693), a phase 3 NCTN sponsored cooperative group trial was conducted to determine if the addition of INO to the CALGB 10403 pediatric regimen would significantly improve EFS. Methods: Eligibility included pts 18-39 years with newly diagnosed CD22 positive ALL, defined as baseline expression in > 20% of lymphoblasts by local institution. Pts with Burkitt-type ALL, BCR::ABL1 positive ALL, or Down syndrome were excluded. Eligible pts received the CALGB 10403 regimen modified to omit extended induction, include dexamethasone as opposed to prednisone as steroid backbone, cap the pegaspargase dose to 3750 units, and adding rituximab for pts with CD20 expression (> 20%). An amendment added blinatumomab for minimal residual disease (MRD) positivity. Pts achieving a complete remission (CR/CRi) or partial remission (PR) were eligible for randomization. Following a 6 pt safety run-in with INO, pts were randomized 1:1 to receive INO or continue CALGB 10403 backbone. Two cycles of INO (1.5 mg/m2/cycle) were administered following induction in the experimental arm. Pts were stratified by age, disease status post induction (M0/M1 vs M2), CD20 status, and LDA Card, which tests for the Ph-like status. The primary endpoint was to determine if the addition of INO would improve the EFS of the pediatric regimen CALGB 10403 without censoring for stem cell transplant (SCT). Key secondary endpoints included the impact of INO on disease-free survival (DFS), OS, and MRD. The Alliance Data and Safety Monitoring Board halted enrollment after 273 out of a planned 341 pts were registered because of increased grade (gr) 5 events in the INO arm compared with the control arm. Results: 273 pts were enrolled between 6/15/2018, and 5/24/2022. Median age was 27.0 yrs, 65.2% were White, 30.4% were Hispanic, and 63.4% were male. Baseline CSF analysis revealed 14% with CNS-2/3 disease. The overall CR rate was 86.8% (82.8-90.8%). 46 pts were not randomized due to death (5), withdrawal (6), ineligibility (3), toxicity (5), receipt of non-protocol therapy (8), progression (5), and other (14). 227 eligible pts were randomized 1:1 to receive INO (N=111) or not (N=116)). For randomized pts, 92.5% achieved M0/M1 marrow status, 48.9% had a positive LDA Card defining Ph-like ALL, 50.7% were CD20 positive. Only 36 pts (13%) received a SCT. With a median follow up of 28.3 months for randomized pts, 3-yr EFS was 69.0% (59.1-80.5%) for the INO arm and 66.7% (57.1-78.1%) for the control (HR=0.97; 0.58-1.63). Similarly, the 3-yr OS was 79.4% (71.0-88.7%) for the INO arm and 80.3% (71.9-89.6%) for the control (HR=1.05; 0.55-2.01). The MRD undetectable rate at Course II Day 56 was 80.6% in the INO arm and 74.2% in the control arm. Univariate analysis suggests improved EFS with INO in pts with a positive LDA card (Ph-like ALL) and of Hispanic ethnicity. There were 22 gr 5 events, 7 occurred prior to randomization. Of the 15 gr 5 events on the randomized cohort, 12 were reported in the INO arm and 3 in the control arm. Of the 12 gr 5 events in the INO arm, all occurred during intensive consolidation courses complicated by prolonged pancytopenia infection/sepsis (8), hepato-biliary in setting of infection (2), multi-organ failure (1), or post-surgical complication (1). These events occurred after INO during Course II (3), Course III (5), or Course IV (4). Conclusions: Although this trial did not meet the primary EFS endpoint for the addition of INO to the pediatric regimen CALGB 10403, these data provide compelling evidence for continued use of pediatric regimens in young adults with ALL as the EFS and OS compares favorably with prior published results. INO may still be efficacious if late toxicity can be mitigated. A pilot study is planned that will decrease INO dose, add 2 cycles of blinatumomab and strict infectious prophylaxis guidelines. Support: U10CA180821, U10CA180882

The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for acute lymphoblastic leukemia (ALL) provide recommendations for management of ALL, with a focus on the classification of ALL subtypes based on immunophenotype and cytogenetic/molecular markers; risk assessment and stratification for risk-adapted therapy; treatment strategies for Philadelphia chromosome (Ph)-positive and Ph-negative ALL for both adolescent and young adult and adult patients; and supportive care considerations. This selection from the NCCN Guidelines for ALL focuses on treatment recommendations for adults with newly diagnosed Ph-negative ALL based on current evidence.

TPS6585 Background: Despite improved outcomes with azacitidine (AZA) and venetoclax (VEN) in newly diagnosed (ND) unfit acute myeloid leukemia (AML), only a subset of patients (pts) respond (CR 37%; CR/CRi 66%) and long-term survival remains inadequate (mOS <15m, DiNardo NEJM 2020). The measurable residual disease (MRD)-negative rate was 41% in AZA-VEN treated pts in VIALE-A which was associated with improved survival (Pratz JCO 2022). CD123 is expressed on the majority of AML blasts and leukemic stem cells while minimally expressed on normal hematopoietic stem cells (Kovtun Blood Adv 2018). Pivekimab sunirine (PVEK, IMGN632) is an antibody-drug conjugate comprising a high-affinity CD123 antibody, cleavable linker, and an indolinobenzodiazepine pseudodimer (IGN) payload. The IGN payload alkylates DNA and causes single strand breaks without crosslinking. IGNs are designed to have high potency against tumor cells, while demonstrating less toxicity to normal marrow progenitors than other DNA-targeting payloads. Clinical data from the first 50 pts in the dose expansion cohorts 1 and 2 with ND AML demonstrated a 76% (22/29) MRD negativity rate (by flow cytometry, negativity threshold <0.1%) (Daver ASH 2023), supporting the continued enrollment of the PVEK+AZA+VEN triplet and further evaluation of the regimen’s antileukemia activity and safety in consideration of potential registration-enabling trials. Methods: This is an open-label, multicenter, phase 1b/2 study of PVEK administered in a combination with AZA+VEN in pts with ND CD123-positive (CD123+ by flow cytometry or IHC) AML, with no prior treatment with hypomethylating agents (HMA). Pts will receive the recommended phase 2 dose of PVEK 0.045 mg/kg IV as a < 30-minute outpatient infusion on day 7, AZA 75 mg/m2 SC or IV daily on days 1 to 7, and VEN 400 mg PO daily for up to 28 days in a 28-day cycle. During cycle 1, a bone marrow evaluation at or around day 21 is required to inform VEN dose duration. Current eligibility criteria for continued enrollment of AML patients unfit for intensive chemotherapy include age ≥ 75 years old, or age < 75 years old with ECOG 2-3, or at least one defined comorbidity. The primary study objectives are to assess antileukemia clinical activity (composite CR [complete remission] rate, overall response rate, duration of remission) and MRD-negativity rates. Key secondary objectives are safety and tolerability, pharmacokinetics and immunogenicity. The PVEK+AZA+VEN triplet in pts with ND unfit AML is currently enrolling across sites in France, Germany, Italy, Spain, UK and USA. Clinical trial information: NCT04086264 .

Chronic myeloid leukemia (CML) is defined by the presence of Philadelphia chromosome resulting from a reciprocal translocation between chromosomes 9 and 22 [t9;22] that gives rise to a BCR::ABL1 fusion gene. CML occurs in 3 different phases (chronic, accelerated, and blast phase) and is usually diagnosed in the chronic phase in developed countries. Tyrosine kinase inhibitor (TKI) therapy is a highly effective treatment option for patients with chronic phase–CML. The primary goal of TKI therapy in patients with chronic phase–CML is to prevent disease progression to accelerated phase–CML or blast phase–CML. Discontinuation of TKI therapy with careful monitoring is feasible in selected patients. This manuscript discusses the recommendations outlined in the NCCN Guidelines for the diagnosis and management of patients with chronic phase–CML.

Background: Obe-cel is an autologous chimeric antigen receptor (CAR) T cell product with a novel CD19 binding domain CAT conferring a fast antigen off-rate designed to mitigate safety concerns and improve persistence over approved CD19 CAR T therapies. Early results from the pivotal FELIX study Phase IIA cohort (N=94) were recently presented (Roddie C et al. J Clin Oncol 2023;41[16 Suppl]:7000). We report findings from a pooled analysis of all patients (pts) treated to date with obe-cel in the FELIX Phase Ib/II study (NCT04404660), with a focus on pts with low leukemia burden prior to obe-cel infusion. Methods: The FELIX study enrolled adults with R/R B-ALL at screening with either morphological disease ≥5% bone marrow (BM) blasts (Cohort A), or in ≥2 nd complete remission (CR)/CR with incomplete hematologic recovery (CRi) with measurable residual disease (MRD) (Cohort B), or with isolated extramedullary disease (EMD) (Cohort C). The Phase Ib part of the study enrolled Cohorts A and B; the Phase II part enrolled Cohorts A, B, and C. CAR T products were generated from leukapheresis material using an automated process. Pts received bridging therapy as needed and lymphodepletion with fludarabine (4 × 30mg/m 2) and cyclophosphamide (2 × 500mg/m 2). A target dose of 410 × 10 6 CAR T cells was infused as a split dose on Days 1 and 10 based on pre-lymphodepletion BM blast burden. The primary endpoint was overall remission rate (best response of CR/CRi by independent review). Secondary endpoints included duration of remission (DoR), MRD negative remission rate, safety, and CAR T expansion/persistence. This pooled analysis included data from pts treated with obe-cel across all cohorts in the Phase Ib/II parts of the study. Low leukemia burden was defined as morphological remission per investigator assessment (&lt;5% BM blasts without EMD) as measured at screening or at the start of lymphodepletion. Results: Between September 2020 and December 2022, 152 pts were enrolled and underwent leukapheresis. As of 16 March 2023, obe-cel was successfully administered to 126/152 (83%) pts (Phase Ib: Cohort A n=13, B n=3; Phase II: Cohort A n=94, B n=9, C n=7). Baseline characteristics at screening (n=126): median age 46.5 (range 20-81) yrs; Philadelphia positive B-ALL 27%; median 2 (range 1-6) prior lines of therapy; prior blinatumomab/inotuzumab 42%/32%; median BM blast burden 37% (range 0-100) including 23% pts with EMD; prior allogeneic stem cell transplant 44%. At a median follow up of 11.0 (range 0.9-30.6) months, the CR/CRi rate was 77% (95/124 response evaluable pts) with CR rate 57% (71/124). Among MRD evaluable responders, 96% achieved MRD negative status by central flow cytometry analysis. Median DoR was not reached at the current follow up. Low rates of Grade (Gr) ≥3 cytokine release syndrome (CRS; 2.4%) and/or Gr ≥3 immune effector cell associated neurotoxicity syndrome (ICANS; 7.1%) were observed. CAR T expansion was similar across the Phase Ib/II cohorts and CAR T persistence was ongoing in the majority of responders at the current follow up. Preliminary data indicate favorable efficacy and safety in pts with low leukemia burden prior to obe-cel infusion. Among 12 pts with MRD at screening (Cohort B), two pts were not evaluable and 9/10 evaluable pts achieved CR/CRi, with 100% achieving MRD negative status by central flow cytometry analysis post obe-cel. Median DoR was not reached at the current follow up. In this subset, no Gr ≥3 CRS was observed; one pt had Gr ≥3 ICANS. In a subset of 28 pts (across all cohorts) in morphological remission at the time of lymphodepletion, 24/27 (89%) response evaluable pts achieved CR/CRi and 100% of MRD evaluable responders achieved MRD negative CR/CRi by central flow cytometry analysis post obe-cel. Median DoR was not reached at the current follow up. In this subset, no pts experienced Gr ≥3 CRS/ICANS. Conclusions:This pooled analysis of data from all pts treated to date in the FELIX study demonstrates high rates of CR/CRi after obe-cel treatment, durable responses (median DoR not reached), and a favorable safety profile. Preliminary data suggest better outcomes in pts with low leukemia burden at screening/lymphodepletion, with higher rates of deep MRD negative complete remission, median DoR not reached at the current follow up, no Gr ≥3 CRS and one Gr ≥3 ICANS. These data support further exploration of CAR T therapy earlier in the treatment algorithm for adults with ALL.

Background and Rationale: Systemic mastocytosis (SM) is a clonal hematologic neoplasm characterized by abnormal accumulation of mast cells which can lead to symptoms related to mast cell degranulation and/or, in the case of advanced systemic mastocytosis (AdvSM), organ dysfunction due to mast cell infiltration. AdvSM is a category of SM comprised of aggressive systemic mastocytosis (ASM), mast cell leukemia (MCL), and SM with an associated hematologic neoplasm (SM-AHN). Among these, SM-AHN is the most common subtype, accounting for approximately 70% of AdvSM. A KIT D816V mutation found in up to 95% of SM cases is the primary oncogenic driver, making it a key therapeutic target. Avapritinib, a highly potent and selective inhibitor of D816V mutant KIT, has demonstrated high rates of rapid, deep, and durable responses in all AdvSM subtypes, including SM-AHN. However, a recent analysis of the EXPLORER study showed that avapritinib-treated patients were still at risk for progression of the AHN component, despite continued control of mast cell disease burden, indicating that combination therapy is likely to be required for optimal control of SM-AHN due to its inherent molecular complexity. Hypomethylating agents (HMA) form the backbone of therapy for advanced myelodysplastic syndrome (MDS) and myelodysplastic/myeloproliferative neoplasm (MDS/MPN), hematologic neoplasms most likely to co-occur with SM in patients (pts) with SM-AHN. To date, the combination of HMA and KIT inhibitors has not been clinically evaluated. In this study, we aim to assess the safety and tolerability of the combination of avapritinib and decitabine in patients with SM-AHN. Study design: The primary objective of the study is to establish the recommended dose (RP2D) of avapritinib in combination with decitabine based on dose-limiting toxicity, overall safety, and clinical activity data. A dose evaluation steering committee (DESC) comprised of participating investigators will review the totality of safety and efficacy data to determine RP2D. Secondary endpoints include SM overall response rate by the end of 6 cycles by the m-IWG consensus criteria and proposed ECNM-AIM criteria ( Gotlib et al., J Allergy Clin Immunol Pract, 2022), as well as incidence and frequency of adverse events. Exploratory endpoints will consist of patient reported outcomes, progression free survival, overall survival, and correlative biomarkers linked to mast cell disease or AHN. Adult pts with a diagnosis of SM-AHN by the WHO 2022 classification criteria will be eligible for inclusion. Eligible pts must have any of the following myeloid AHN per WHO 2022 criteria: MDS, chronic myelomonocytic leukemia, MDS/MPN with neutrophilia, MDS/MPN with SF3B1 mutation and thrombocytosis, or MDS/MPN- not otherwise specified. Patients with MDS must have intermediate, high- or very-high risk by IPSS-R. Patients with very-low or low-risk MDS by IPSS-R must be intolerant/refractory to ESA or have serum EPO &gt; 200 U/L. A baseline platelet count of ≥ 75 x 10 9/L and ≥ 25 x 10 9/L will be required for inclusion in the dose-finding and the dose-expansion phases, respectively (Figure). Key exclusion criteria include a diagnosis of acute myeloid leukemia, history of intracranial hemorrhage or risk of major hemorrhage, prior treatment with avapritinib or decitabine with documented progression in SM or AHN component, respectively, or history of treatment with alternative KIT inhibitor or azacitidine within 4 weeks of study treatment initiation. In the dose finding part of the study, a Bayesian adaptive design will be employed to assess different doses of avapritinib (50 to 200 mg PO daily) in combination with fixed doses of decitabine (oral decitabine/cedazuridine: 35/100 mg/day or intravenous decitabine: 20 mg/m 2/day on days 1-5) in a 28-day treatment cycle. Close attention will be paid to treatment-emergent thrombocytopenia with protocol-driven treatment holds and dose modification strategies employed when platelet count drops below 50 x 10 9/L. After RP2D is determined, an additional 10 patients will be enrolled in the dose expansion phase. Patients with platelet count ≥ 25 x 10 9/L and &lt; 75 x 10 9/L, will receive lead-in dosing with decitabine or decitabine/cedazuridine with the ability to add avapritinib if sufficient platelet thresholds are achieved. This study will open at 7 sites in the United States and is anticipated to open in January 2024.