Major Molecular Response Research Articles

Real-World Safety and Clinical Response of Flumatinib in the Treatment of Chronic Myeloid Leukemia: A Retrospective Study

Objective: The objective of this retrospective study was to assess the effectiveness and safety of flumatinib in the treatment of chronic phase chronic myeloid leukemia (CML) in real-world settings. Methods: A total of 61 patients who received flumatinib as first-line therapy were compared with 92 patients who received first-line imatinib therapy. Furthermore, the 58 patients who received flumatinib as post-line therapy were divided into two groups based on the timing of switching to flumatinib: an early conversion group (n=18) and a late conversion group (n=40). The molecular responses and outcomes were assessed at multiple time points (3, 6, 9, and 12 months) during the treatment of flumatinib, along with the observation of adverse reactions. Results: In comparison to imatinib, the use of flumatinib as a first-line therapy demonstrated statistically significant increases in early molecular response (EMR), major molecular response (MMR), and deep molecular response (DMR) at various milestones (p<0.05). Additionally, the incidence of adverse events was lower in the flumatinib group, as evidenced by higher event-free survival (EFS) rates (83.6% vs. 39.1%, P=0.01) and a lower medication switching rate (90.2% vs. 31.5%, P<0.001). However, there were no significant differences observed in overall survival (OS) and progression-free survival (PFS) rates between the two groups (P>0.05). In the context of post-line therapy, a significant proportion of patients (72.2%) achieved EMR at 3 months, while 71.9% achieved MMR at 12 months when treated with flumatinib. Notably, the early conversion group exhibited higher rates of molecular response and demonstrated superior OS, PFS, and EFS at the 12-month mark compared to the late conversion group (P>0.05). Adverse events (AEs) commonly associated with flumatinib encompassed limb discomfort, gastrointestinal reactions, and elevated transaminase levels, with thrombocytopenia being the most frequently observed hematologic AE. Conclusion: Flumatinib exhibited notable efficacy and safety as a therapeutic option for patients with chronic phase CML, whether utilized as a first-line or post-line treatment. In comparison to imatinib, initial administration of flumatinib resulted in more profound and expeditious molecular responses. The utilization of flumatinib as a post-line therapeutic approach during the early stage of treatment exhibits a favorable influence on patient prognosis. However, no statistically significant disparity was noted when compared to the group receiving switch therapy during the late stage.

Clinical Determinants of Early Mortality Following Allotransplantation for Acute Lymphoblastic Leukemia in a Brazilian Multicenter Registry

Introduction: Allogeneic stem-cell transplantation (HSCT) continues to be a potentially curative approach for acute lymphoblastic leukemia (ALL). However, one of the primary challenges in HSCT remains the transplantation-related mortality (TRM), even though the overall complications and mortality rates have decreased over time. Notably, in developing countries, previous research on HSCT has highlighted that early mortality plays a significant role in their comparatively worse outcomes. Therefore, it is crucial to identify the factors involved in early mortality to enhance cure rates. Considering this, our study aims to investigate the risk factors associated with early mortality following HSCT for ALL in Brazilian centers. Methods: This is a retrospective registry study. Patients with ALL or ambiguous lineage leukemia above 16 years who underwent a first HSCT in 5 Brazilian centers between January 2007 and December 2017 were included. Early mortality (EM) was defined as death within 100 days from HSCT. A multivariable analysis (MVA) was performed using logistic regression, with the Akaike's information criteria used for model selection. A p-value<0.05 was considered statistically significant. Results: Overall, 275 patients were included in this study. Baseline characteristics are summarized in Table 1. The median age was 31y (range, 16-65) and 58.5% were male. The Philadelphia chromosome was reported in 35% and most patients were in first complete remission (CR1) (66%). Matched sibling donor (MSD), matched unrelated donor (MUD), mismatched unrelated donor (MMUD), haploidentical donor, and umbilical cord were reported in 53%, 19%, 9%, 19%, and 5%, respectively. The median donor age was 31y (range, 4-64) and 54.4% were male. EM rate was 24.4%. Univariate analysis pointed some factors statistically related to EM, as it follows: graft source (p<0.001), baseline KPS (p=0.03), gender (female vs. male, 16.7 vs 27.9%, p=0.03), Ph-positive status (p=0.03), refractory disease status (p=0.015), umbilical cord blood source (p=0.01), and donor age (p=0.08). There was no difference regarding EM rates between public and private centers (24.5 vs. 19%, p=0.463). The best multivariable model included gender, Ph-status, donor type and donor age as final variables for EM. In our cohort, Ph-positive status (OR = 2.83), donor age (OR = 1.05), and the use of MUD (OR = 3.68) were independently associated with early transplant-related mortality. Regarding the cause of EM, 69% were related to infection, and 19.5% were caused by acute GVHD. Interestingly, EM was higher in Ph-positive patients with no major molecular remission (BCR-ABL≥0.1%) - 40 vs. 3.6%, p=0.008). Cumulative incidence of acute GVHD at day 100 was 48.3% by competitive analysis. Only 3 out of 62 deaths in EM group were due to disease relapse. Remaining deaths were secondary to bacterial infection (52%), followed by acute GVHD (17.8%) and fungal infection (8.9%), mainly. Conclusions: This study represents the largest analysis in Brazil to assess early transplant-related mortality in ALL patients. Reducing EM rates is particularly important in resource-constrained settings to improve outcomes. While the overall patient characteristics were similar to other registry analyses, the EM rate in this study was higher than that reported in other cohorts worldwide. Notably, transplant-related factors such as donor age and type, in addition to Ph-positive status, were found to be associated with EM, outweighing previously known factors like conditioning intensity and the use of total body irradiation. These findings could aid in enhancing donor selection in Brazil and optimizing HSCT indications in specific subsets.

Lower-Initiating Dose of Bosutinib for Resistant or Intolerant to Prior Therapy Chronic Myeloid Leukemia Patients (BOGI trial): A Single-Arm, Multicenter, Phase II Trial

Introduction: The introduction of ABL1 tyrosine kinase inhibitors (TKIs) has markedly improved the survival outcomes in patients with chronic phase chronic myeloid leukemia (CML-CP). Second-generation TKIs are highly active for patients with newly diagnosed and resistant/intolerant CML-CP. Although bosutinib is generally safe, drug-related toxicities (DRTs) such as diarrhea or increased transaminase leading to treatment discontinuation, are often observed. The standard initial daily dosage of bosutinib is 400 mg for newly diagnosed or 500 mg for resistant/intolerant patients with CML-CP, whereas some experts suggest lower dose (200-300 mg) initiation is recommended to reduce adverse events (AEs). However, the safety and efficacy of lower dose initiation of bosutinib are unknown. Hence, we conducted a phase 2 study of BOsutinib Gradual Increase as a second/third-line treatment for CML-CP (BOGI trial, UMIN 000032282) to clarify whether a lower initiating dose of bosutinib (200 mg daily) would reduce discontinuation or interruption of treatment due to DRTs. Patients and methods We included CML patients who developed at least one line of treatment failure (resistant or intolerant), aged >18 years with an ECOG performance status of 0-2 and adequate organ function. After enrollment, the patients initiated 200 mg of bosutinib daily; subsequently, dose escalation was performed by 100 mg daily (up to 500 mg daily) every 2 weeks if no grade 3 or higher AEs occurred. BCR::ABL1 mRNA levels were measured by the standardized international scale at a central laboratory at 3, 6, 9, and 12 month since treatment initiation. The primary endpoint was the treatment discontinuation rate due to DRTs at 12 months. Secondary endpoints included the treatment interruption rate, mean bosutinib dosage, dosing days and relative dose intensity until 12 months, achievement of cytogenetic response (CCyR), cumulative rates of major molecular response (MMR) or deep molecular response (DMR). Sample size calculation was performed by research and biostatistics SWOG statistical tools (at null proportion = 0.32, alternative proportion = 0.14, one-sided α error = 5% and β error = 20%, power 80%) with the discontinuation rate of the previous Japanese phase 1/2 study of bosutinib as a reference (Nakaseko C, et al. Int J Hematol. 2015). Considering protocol deviations, sample size was 35 participants. Results Between Feb 4, 2019, and May 24, 2022, 35 patients enrolled from four Japanese hospitals. The median age was 61 years (range, 26 - 81 years); 19 patients were male and 16 were female and 16, 12, and 7 patients had low,intermediate, and high Sokal scores, respectively. Ten patients had hypertension, five had diabetes millitus, three had chronic heart disease, two had solid tumor, and one had cerebrovascular disease, respectively. Numbers of patients with previous TKIs were one for 19 (54%), two for 12 (34%) and three for 4 (11%), respectively and prior TKIs are imatinib (8, 23%), dasatinib (27, 77%), nilotinib (16, 46%) and bosutinib (1, 3%), respectively. In the intention to treat population, the bosutinib discontinuation rate at 12 months was 25.7% (95% CI, 15.6-39.3%) which is significantly lower than that of the previous report (v.s. 43.0%, p=0.019). Similarly, bosutinib discontinuation rate due to DRTs was 11.4% (95% CI, 5.2 - 23.2%), which is also significantly lower (v.s. 32%, p = 0.005). These results suggest lower initiating dose of bosutinib reduced bosutinib discontinuation rate due to DRTs, thus the primary endpoint was met. A total of 22 patients (62.9%) interrupted bosutinib at least once. Median bosutinib dosage, bosutinib dosing days and relative dose intensity until 12 months were 391.7 (204.9-477.3) mg/day, 351.0 (20-365) days and 78% (41-95), respectively. 28 patients (80.0%) achieved cytogenetic response (CCyR) at 6 months; cumulative incidence of MMR and DMR at 12 months were 23 (65.7%; 95%CI, 49.2-79.2%) and 15 (42.9%; 95%CI, 28.0-59.1%), indicating these secondary endpoints were comparable with the previous report. Grade 3 to 4 transaminase elevation was 20% which is comparable with the previous report (v.s. 29%, p=0.427), while a lower rate of diarrhea (3%; v.s. 25%, p=0.009) was notable. Conclusion The lower initiating dose followed by a gradual dose increase of bosutinib reduced the drug discontinuation rate due to severe DRTs, especially diarrhea, while efficacy was assured.

Flumatinib Versus Nilotinib for Newly Diagnosed Chronic Phase Chronic Myeloid Leukemia

Introduction Tyrosine kinase inhibitors (TKIs) have considerably improved the long-term clinical outcomes in patients with chronic phase chronic myeloid leukemia (CML-CP). Most of these patients receive 1 st generation TKI imatinib as first-line therapy; however, an increasing number of patients are now receiving 2 nd generation TKIs as first-line therapy, because of the more potent BCR-ABL1 inhibition with proven efficacy in patients resistant or intolerant to imatinib. Flumatinib is a novel 2 nd generation BCR-ABL1 TKI with promising efficacy and manageable safety in newly diagnosed CML-CP. Compared to imatinib, patients treated with flumatinib have achieved significantly higher rates of 12-month major molecular response (MMR) and complete cytogenetic response were observed in patients with CML-CP and that too within a shorter time duration. Though there have been many studies comparing 2 nd generation TKIs vs imatinib in CML-CP, studies comparing clinical outcomes between different 2 nd generation TKIs are scarce. Here, we report the real-world effectiveness and safety of flumatinib and nilotinib in patients with newly diagnosed CML-CP. Methods In this study, adult patients (≥18 years old) with newly diagnosed Philadelphia chromosome-positive (Ph+) CML-CP who received either 300 mg nilotinib twice daily or 600 mg flumatinib once daily, were included, with a follow-up duration of roughly 3 years (NCT04739826). The primary endpoint was the rate of MMR at 12 months as defined by European LeukemiaNet 2020 recommendations (BCR-ABL1 transcript level ≤0.1% in peripheral blood on RT-PCR assay on International Scale [IS]).The secondary endpoints were the rate of early molecular response (EMR) at 3 months (BCR-ABL1 IS ≤10%), the rate of molecular response at 6 months (BCR-ABL1 IS ≤ 1%) and safety (adverse events [AEs] reports in accordance to Common Terminology Criteria for Adverse Events, version 4.03). Results A total of 446 patients were enrolled in the study between November 2020 and August 2022, of which 150 and 296 patients were enrolled in nilotinib and flumatinib groups, respectively. The baseline characteristics were comparable between the two groups (Table 1). No significant difference in the rate of MMR was observed at 12 months between nilotinib and flumatinib (78% vs 80%; P=0.68) . Similarly, no significant difference was observed in the rate of EMR at 3 months (85% vs 89%; P=0.26) and the rate of optimal molecular response at 6 months (93% vs 92%; P=0.70; BCR-ABL1 is ≤1%) between the two groups. The overall safety profile was similar between the two groups. However, hyperbilirubinemia (47% vs 7%), increased ALT (33% vs 12%), increased AST (24% vs 9%), rash (30% vs 18%) and anemia (19% vs 10%) were more frequent in nilotinib group than flumatinib group, whereas diarrhea was lower in nilotinib than flumatinib (2.7% vs 8.8%). The incidence rate of grade 3-4 AEs were reported to be 13% in nilotinib group and 10% in flumatinib group. The safety of flumatinib was more favorable compared to nilotinib in terms of hepatic toxicities, skin toxicities, etc. (Figure 1). Conclusion The efficacy of flumatinib is comparable to nilotinib in Chinese patients with newly diagnosed Ph+ CML-CP. The overall incidences of grade 3-4 AEs were also accessible for the two drugs, nevertheless, a few AEs inclusively hepatic toxicity, anemia and skin toxicity were remarkably lower with flumatinib intervention.

Long-Term Follow-up of the AST Trial of Treatment-Free Remission in Chronic Myeloid Leukemia Patients

Background: Treatment-free remission (TFR) is a new goal for chronic myeloid leukemia (CML) patients who achieved a long deep molecular response (DMR) with better quality of life, reduced adverse events and high economic impact. The primary objective of the AST trial was to estimate molecular relapse rate at 24 month in CP-CML patients who discontinued TKI. Secondary objective to explore predictive markers for sustained TFR through clinical and immunological analysis ( innate inmune response). This update provides longer follow-up data and includes a new cohort of patients. Patients and Methods: AST-Argentina Stop Trial (NCT05926128) is a multicenter prospective study that included patients from 15 centers. Recruited patients ≥ 18 years, treated with TKI for at least 4 years, sustained MR 4.0 for ≥ 2 years and confirmed typical BCR-ABL1 b3a2 and/or b2a2 transcripts. Molecular studies were centralized in 2 internationally standardized laboratories and were performed monthly during the first 6 months, every 2 months until the first year, and every 3 months during the second year. TKI was restarted due to loss of major molecular response (MMR). Expression of multiple NK cell immunophenotypic markers(CD3-CD56+) was analyzed by flow cytometry at discontinuation time and 3 months later. The nonparametric Mann-Whitney test was used to compare the differences between relapsed and responding patients. Molecular relapse-free survival was estimated using the Kaplan-Meier method and optimal cut-off points were obtained using ROC curves. Comparisons between survival curves were made using the Log rank test method. The differences were considered statistically significant with p-values less than 0.05. Multivariate analysis was performed using the COX regression model. Results: A total of 81 patients divided into 2 cohorts were evaluated: 46 patients recruited between February 2018 and July 2020 (1st cohort) and 35 patients recruited between July 2022 and April 2023. Between these two periods, recruitment was stopped due to the COVID19 pandemic. This analysis focuses on the 1st cohort that has completed 24 months in the study. The median age was 57.5 years (24-86), median duration of treatment before discontinuation was 10.5 years (4.2-20). TKI treatment prior to discontinuation was as follows: Imatinib in 34 (73%) patients, Dasatinib 8 (17%), and Nilotinib 4 (9%). According to Sokal risk score: 22 (48%) were low risk, 14 (30%) intermediate, and 10 (22%) high risk. Seventeen patients (37%) lost MMR, leading to a 63% molecular relapse-free survival rate with a median follow-up of 47 months (41-52). All patients who lost MMR recovered it after restarting the same TKI, with a median time to response of 2.8 months (1-7). With a prolonged follow-up, 2 late relapses were observed (18 and 42 months) (Fig 1). For a univariate analysis, the continuous variables were dichotomized seeking to maximize the difference between the different cohorts. The differences were significant in the variables time in DMR (cut-off point: 51 months, p=0.0166)(HR=0.97 (0.94 - 0.99); p=0.013). Two of the NK cell markers showed significant differences between groups at month 3 after starting treatment, PD1 (Mann-Whitney p=0.035; Log-Rank test p=0.033) and NK-p44 (Mann-Whitney p=0.015; Log -Rank test p=0.020). Multivariate analysis using the Cox model that included variables as gender, age at diagnosis, time in DMR, time in TKI prior to discontinuation, Sokal score, and type of inhibitor, the clinical predictor of time in DMR was the only predictor, significantly associated with a higher rate of TFR, (HR = 0.97 (0.95 - 0.99); p=0.020). No patient experienced disease progression to advanced stages or death for any reason. Conclusion:This is the first multicenter study of TKI discontinuation in CML patients in Argentina showing that TKI can be safely discontinued in those who achieve and maintain a DMR before discontinuation. Molecular relapse-free survival rate was slightly higher than that reported in the international literature, and longer follow-up confirmed the sustained response. DMR before discontinuation showed to be a robust predictor of TFR. Although the sample size was increased, longer follow-up is needed to validate these findings in the second cohort. Potential advantages of TFR will not only impact in patients' quality of life but also show considerable reduction in the use of economic resources.

Impact of Mutations in Blood Cancer-Related Genes on Clinical Outcomes in Chronic Myeloid Leukemia in Chronic Phase (CML-CP) after ≥2 Tyrosine Kinase Inhibitors (TKIs) in the Ascembl Trial

CONCLUSIONS Somatic mutations in blood cancer-related genes are commonly detected in CML-AP. The most frequently mutated genes are RUNX1, ASXL1IKZF1 (submicroscopic deletions), and BCR:: ABL1 (kinase domain mutations). ASXL1 is the most frequently detected mutation at CML diagnosis (≈9%). However, the incidence and impact of mutations in blood cancer-related genes in patients (pts) with CML-CP previously treated with ≥2 TKIs have not been described since genomic studies have focused on pts at diagnosis or at progression. With >2 years of follow-up in the phase 3 ASCEMBL study, asciminib (ASC) has continued to demonstrate superior efficacy vs bosutinib (BOS) in pts with CML-CP after ≥2 prior TKIs, and analysis of cancer gene somatic mutations in this population has the potential to reveal additional insights into pts' response to study treatments or characteristics of the disease in later lines of therapy. Here we present a descriptive analysis of variants in the ASCEMBL pt population, including frequencies, co-occurrences, and association of mutations with clinical outcomes, specifically major molecular response (MMR) and treatment failure (TF; defined as discontinuation due to lack of efficacy or intolerance). Adults with CML-CP previously treated with ≥2 TKIs with intolerance of their last TKI or lack of efficacy per 2013 European LeukemiaNet recommendations and without BCR:: ABL1 T315I or V299L mutations were randomized 2:1 to ASC 40 mg twice daily or BOS 500 mg once daily. DNA was isolated from blood collected at baseline (BL) and end of treatment (EOT; defined as treatment discontinuation for any reason or completion of the study). A next-generation sequencing panel of 89 commonly mutated genes in blood cancers, including ABL1 and IKZF1 deletion, was used to detect somatic mutations that met criteria for pathogenicity. Only samples with BCR::ABL1IS ≥2%, which was the level demonstrated to detect mutations in leukemic cells, were tested. A multivariable Cox proportional hazards regression model adjusted for age, sex, treatment, and reason for prior TKI discontinuation (intolerance vs lack of efficacy) was used to determine the prognostic value of BL mutations. A total of 233 pts were randomized to ASC (n=157) or BOS (n=76). Of 162 pts (ASC, n=110; BOS, n=52) with available sequencing data at BL, 102 had ≥1 mutation: 69 (63%) on ASC and 33 (63%) on BOS. Overall, 159 mutations were detected in 23 genes at BL, ranging from 0 to 5 per pt. The median variant allele frequency (VAF) was 19.6% (range, 0.9%-58%). ASXL1 (in 31% of pts) and ABL1 kinase domain (in 17% of pts) mutations were the most frequently detected. Of 27 pts with ≥1 ABL1 mutation at BL, 85% had ≥1 other mutated cancer gene. Co-occurrence of ASXL1 and ABL1 mutations at BL was reported in 12 of 162 pts (7.4%), which was higher than the expected 2.9% based on these genes' individual frequencies in this data set. RUNX1 and IKZF1 mutations were rare in CML-CP at BL. Of 162 pts tested at BL, 73 had TF and available samples for analysis at EOT with only 3 pts discontinuing due to disease progression. The presence of any mutation at BL was significantly prognostic of TF in the total cohort of 162 pts (Figure 1). In an unadjusted analysis, the presence of an ASXL1 mutation with VAF >5% at BL was a prognostic factor of TF. In 73 pts with TF, most BL mutations were also detected at EOT (110/116 mutations in 48/54 carriers) (Figure 2). Of 15 pts who acquired ≥1 mutation at EOT, 9 acquired ABL1 mutations. No single mutations at an individual or gene level were prognostic of MMR. Mutations were not predictive of MMR or TF when pts were examined by their assigned treatment of ASC or BOS. ASXL1 mutations are most frequently detected at CML diagnosis and were enriched at BL in this study of pts with CML-CP previously treated with ≥2 TKIs, which is consistent with a role in TKI resistance. RUNX1 and IKZF1 mutations, which are associated with progression to accelerated or blast phase in CML, were very rare in this pt population, supporting their role in CML disease progression. The high frequency of co-occurrence of BCR:: ABL1 mutations and blood cancer gene mutations in CML-CP is an important finding since cancer gene mutations could modify response to TKIs in individual pts. The presence of any somatic blood cancer mutation at BL was prognostic of TF. These mutations may serve as potential biomarkers that can identify pts who may be at higher risk of TF in later lines of therapy.

Efficacy of Frontline Treatment with Initial Low-Dose Tyrosine-Kinase Inhibitors in Elderly Patients with Chronic Myeloid Leukemia: A “Campus CML” Study

Introduction Three TKIs, imatinib (IM), dasatinib (DAS) and nilotinib (NIL), are approved for frontline therapy in Italy. Choice of frontline TKI is based mainly on evaluation of patient's characteristics and clinical expectations. To avoid long term adverse events or potential drug interactions, elderly patients may start CML treatment with a frontline reduced dose of TKI (RD-TKI). Aim To analyse outcome of CP-CML patients aged over 65 years in a large and unselected cohort treated with RD-TKI. Methods We retrospectively evaluated 747 patients from 1/2012 to 12/2019 at 36 Hematology Centres participating at the “Campus CML” project. Results Clinical features for the whole cohort according to frontline TKI initial dose are reported in Table 1. Among all patients, 605 (81%) were treated with standard dose (SD) while the remaining 142 (19%) with reduced dose (RD). As to frontline TKI, 579 patients (77%) received IM and 158 (23%) a 2G-TKI (DAS n=78, 49%; NIL n=80, 51%). Of the 142 RD-TKI, 122 (85.9%) started with IM, 14 (9.9%) with DAS and 6 (4.2%) with NIL. Median RD was 100 mg for IM (range 100-300), 20 mg for DAS (range 20-50) and 250 mg for NIL (range 150-300). RD-TKI was mainly reported in IM treated patients (p=0.018), in elderly (p<0.001) and in patients with comorbidities, in particular diabetes (p=0.005) and ischemic heart disease (p=0.039). Number of concomitant drugs was also significantly associated with RD-TKI (p<0.001) probably to avoid drug interactions and subsequent toxicity. In detail, among RD-TKI, 41.1% of patients was treated with more than five concomitant drugs. Sokal score did not impact on TKI starting dose. No differences emerged between SD-TKI and RD-TKI in terms of haematological or extra-haematological toxicity. TKI frontline dose was not associated with difference in resistance, nor primary neither secondary resistance. Progression to blastic phase was reported in 1.2% of the whole population, none of which in RD-TKI. At 12 months no differences were noted in terms of achievement of major molecular response (MMR), obtained in 22.4% of SD-TKI treated patients and in 19% of RD-TKI treated patients. RD-TKI had inferior probability of deep molecular response (DMR) achievement (p=0.003), reported in 12.6% of patients. No differences were reported in 12-months cumulative rate of permanent discontinuation for any cause and for primary resistance between SD-TKI and RD-TKI as reported in Figure 1. Conclusions RD-TKI was a frontline treatment strategy used mainly in frail elderly patients, with more comorbidities and concomitant therapies. RD-TKI did not impact on primary resistance leading to TKI switch. While no differences were reported in the rate of MMR, the rate of 12-months DMR achievement was inferior in RD-TKI, but this result need to be confirmed with longer follow-up.

Evaluating Effectiveness and Safety of Flumatinib for Chronic Phase Chronic Myeloid Leukemia in (CML-CP) without Optimal Response (Warning, Failure) to Imatinib or/and Dasatinib

Introduction Flumatinib is a novel second-generation BCR-ABL1 targeted kinase inhibitors (TKI) with better efficacy and safety than first generation TKIs in first-line treatment of chronic myeloid leukemia in chronic phase (CML-CP). In the previous phase III study, newly diagnosed CML-CP patients receiving flumatinib achieved higher treatment responses and safety than imatinib. When it comes to the patients not achieving the optimal response to TKIs, flumatinib is potentially a better option, nonetheless the robust evidence is unavailable. This study reports the effectiveness and safety of switching to flumatinib in patients who have not achieved the optimal molecular response to imatinib or/and dasatinib. Methods This prospective, multicentre study enrolled Philadelphia Chromosome-Positive (Ph+) CML-CP patients aged ≥18 years and who failed to achieve the optimal response with imatinib or/and dasatinib between March 2021 to October 2022. All patients were treated with flumatinib 600 mg once a day and followed up to 24 months. The primary endpoint of the study was rate of major molecular response (MMR) at 12 months as defined by European LeukemiaNet 2020 recommendations (BCR-ABL1 transcript level ≤0.1% in peripheral blood on RT-PCR assay on International Scale [IS]) and safety was the secondary endpoint assessed with CTCAE 4.03 version. In addition, the optimal molecular response in either the warning or failure patients was evaluated at 3, 6 and 12 months respectively, after switching to flumatinib, and the difference in effectiveness was also analyzed from the available mutation subtypes. Results Overall, 94 patients with Ph+ CML-CP were included in the study. The median (range) age of the patients were 53 (19.0-84.0) years old and 61.7% of the patients were males. A total of 38 (40.4%) patients reported warning response from the previous TKIs whereas 56 (59.6%) of patients reported treatment failure to the previous TKIs. Seventy-seven (81.9%) patients have been treated with one TKI, either imatinib or dasatinib, and 17 (18.1%) have been treated with both prior to the study. Overall, 25 (54%) patients achieved MMR at 12-months follow-up compared to the baseline (Figure 1). The rates of optimal molecular response at 3- and 6-months were also improved compared to the baseline. The optimal molecular response was 76(88%) at 3 months, and 52(73%) at 6 months. Subgroup analysis with previous response to TKIs revealed that flumatinib improved the rates of optimal molecular response in both warning and failure groups. Switching to flumatinib from imatinib or/and dasatinib have been reported with an enhanced optimal molecular response in patients who experienced warning compared with those who had treatment failure after the TKIs with 38 (100%) vs 38 (79%), 29 (91%) vs 23 (59%) and 15 (68%) vs 10 (42%) at 3-, 6- and 12-months respectively (Figure 2). Similarly, the rates of optimal molecular response were improved in patients without mutations compared to those having mutations, 65 (90%) vs 9 (75%) at 3 months, 46 (77%) vs 5 (56%) at 6 months and 23 (59%) vs 1 (20%) at 12 months respectively. The most common adverse events (AEs) were diarrhea in 17 (18%), rash in 11 (12%), bloating in 11 (12%), and thrombocytopenia in 11 (12%) patients. Common hematological AEs of grade 3/4 were thrombocytopenia in 7 (7%), anemia in 3 (3%) and leucopenia in 1 (1%) patients. Conclusion For Ph+ CML-CP patients without the optimal molecular response in previous imatinib or/and dasatinib, flumatinib is a better alternative to the existing treatments. In addition, if the patients were switched to flumatinib earlier, the optimal response was achieved faster. The grade 3/4 AEs were mainly hematologically related, whereas the gastrointestinal events were mostly of grade 1-2.

HJKC3-007: Outcomes of Patients with Chronic Myeloid Leukemia in Chronic Phase Treated with Asciminib and Other Tyrosine Kinase Inhibitors in Routine Clinical Practice

Background and significance: There are typically high response rates to first line TKI therapies in chronic phase chronic myeloid leukemia (CP-CML). However, responses in later lines (second line and beyond) are diminished and highly dependent on the specific tyrosine kinase inhibitors (TKIs) used. Asciminib received FDA approval in October 2021 for the treatment of adult patients with Philadelphia chromosome-positive (Ph+) CML-CP who were previously treated with two or more TKIs, and in patients with Ph+ CML-CP with the T315I mutation. Our goal in this study is to evaluate the role of asciminib therapy for patients with CML beyond clinical studies, in routine clinical practice. Study Design and methods: Data for this study will be abstracted from the HJKC3 (H. Jean Khoury Cure CML Consortium) CML registry project (HJKC3-0005); the HJKC3 CML Registry is a collaborative academic multi-site registry. Patients will be consented to allow collection of both retrospective and prospective data for the HJKC3 CML Registry. The data forms and surveys will be built and managed through the Research Electronic Data Capture (REDCap), a secure web application managed by the Clinical & Translational Science Institute. Participating sites include members of the HJKC3 (curecml.org). This study will be an opportunity to evaluate asciminib usage in ‘real-world’ academic practices across the United States. This observational study will include cohorts of patients diagnosed with CP-CML previously treated with two or more tyrosine kinase inhibitors and/or receiving asciminib and/or those with a T315I mutation, not currently enrolled in a randomized controlled trial. The HJKC3 CML Registry intends to collect clinical and patient reported outcome (PRO) data. After obtaining patient consent, patients will be invited to complete PRO assessments. The study will attempt to collect PRO data regardless of disease or treatment status. PRO assessments will be primarily administered online, though study staff will offer alternatives (e.g., phone) for participants without internet access. Study subjects will be emailed a link to access a secure platform hosted by one of the study sites, Medical College of Wisconsin (MCW), using the REDCap platform. Study Objectives: The primary objective of the study is to describe characteristics of patients who were previously treated with two or more TKIs and treated with asciminib or with any other TKIs. The secondary objectives are to describe the clinical outcomes and PRO of those patients. Exploratory objectives include description of characteristics, treatment outcome and PRO for patients with T315I mutation. Statistical plan: The sample size of approximately 225 participants during the 5-year recruitment period is based on the available clinical expertise and ongoing recruitment data in the HJKC3 CML registry in lieu of statistical power analysis. We estimate that 150 patients in the HJKC3 CML registry will be treated with other TKI and 75 treated with asciminib. Among a total of 225 patients, we estimate that 75 patients with the T315I mutation will be enrolled in the registry. No formal statistical inference will be drawn to compare the outcomes between these two groups. Bayesian predictive probability (PP) will be utilized for the exploratory analysis of Major Molecular Response (MMR). Survival probabilities will be computed using the Kaplan-Meier method, and the p-values from the log-rank test will be provided. Different PRO domains of the patient's symptoms and functioning will be analyzed separately (e.g., depression separate from fatigue, separate from GI symptoms, etc.) since combining them into a summary score may dilute the effects of the individual (and not necessarily related) components and mask actual change. The main objective for the analyses of PRO data from the registry is to describe any differences by treatment type in patients treated with asciminib and other TKIs.

Long-Term Follow up for SWOG 1318: Combination of Dasatinib, Prednisone, and Blinatumomab for Older Patients with Philadelphia-Chromosome (Ph) Positive Acute Lymphoblastic Leukemia (ALL)

Tyrosine kinase inhibitors (TKIs) have improved the outcomes of patients with Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL). Many older patients (pts) are not good candidates for intensive chemotherapy and are treated with TKIs plus corticosteroids or low-intensity chemotherapy. Although the remission rates with this approach have been high, the median disease-free survival (DFS) has been short. Therefore, novel treatment strategies are needed. This trial evaluated the feasibility of combining the TKI dasatinib with prednisone and blinatumomab in older pts with Ph+ ALL. Here we present updated results (median follow-up, 4.3 years). Methods: This trial was activated through the NCTN in January 2015 and closed to accrual in April 2021. Pt eligibility included: age ≥ 65 years; Ph+ or Ph-like ALL (with dasatinib-sensitive fusions or mutations); newly diagnosed or relapsed/ refractory; no evidence of central nervous system (CNS) disease; and adequate organ function. Treatment: For induction, pts received dasatinib 140 mg/d orally (PO) Days 1-56 along with prednisone 60 mg/m 2/d PO Days 1-24. Pts achieving complete remission (CR) or CR with incomplete count recovery (CRi) (Day 28 or Day 56) continued dasatinib until Day 84, followed by 3 cycles of post-remission therapy (PRT) with blinatumomab/ dasatinib. Pts not achieving CR or CRi by Day 56 received re-induction with blinatumomab. The response rate was assessed on Day 35 of blinatumomab. Pts not achieving CR/ CRi could receive a second cycle of blinatumomab. This was followed by 3 cycles of PRT with blinatumomab/ dasatinib. Maintenance therapy consisted of prednisone 60 mg/m 2/d x 5 days every 28 days for a total of 18 cycles, along with dasatinib 140 mg po qd indefinitely. CNS prophylaxis included intrathecal (IT) methotrexate every 4-6 weeks x 8 doses. IT methotrexate was given at least 2 days apart from blinatumomab. Response was assessed at Days 28, 56, and 84, and additional time points were dependent on response. Minimal residual disease (MRD) was assessed centrally by multi-color flow cytometry on Day 28. Statistics: A total of 24 eligible patients were accrued. The primary objective was the feasibility of the combination therapy. The combination was to be deemed feasible if the dose-limiting toxicity (DLT) was < 33%. DLT included: > Grade 3 non-hematologic toxicities (excluding nausea, vomiting, diarrhea) and Grade 4 neutropenia lasting > 42 days. The primary results were reported in 2022 with a median of 2.7 years of follow-up. Herein, we report long-term outcomes for these patients. Results: The median age was 73 years (range 65-87). All pts had newly diagnosed Ph+ ALL; 79% of Ph+ pts had additional cytogenetic abnormalities. During induction, 2 pts experienced treatment-related non-hematologic Grade 4 toxicities. No Grade 4 or higher treatment-related non-hematologic toxicities occurred during post-remission therapy or maintenance. The toxicity of the combination was deemed acceptable. Twenty-two of 24 pts (92%) achieved a CR during dasatinib and prednisone induction therapy. Four did not receive PRT (2 due to adverse events, 1 to receive a transplant, and 1 because of insurance issues). Sixteen pts who achieved CR had MRD data. Six of 16 pts (38%) were MRD undetectable by multi-color flow cytometry on Day 28. Most sites also monitored patients' blood or bone marrow with real-time quantitative PCR to quantify the BCR-ABL1 transcript for molecular response. Of 19 patients analyzed, 17 (89%) were in a major or complete molecular remission at some time point after treatment, with at least 12 of these patients achieving complete molecular remission. Four patients remain on maintenance. The median follow- up for pts who are alive is 4.3 years (range 2.6-6.5 years). The median overall survival (OS) is 6.5 years (95% CI 3-NA) and the median DFS has not been reached as of June 29, 2023. Kaplan-Meier 3-year estimates of OS and DFS are 75% (95% CI 52%-88%) and 72% (95% CI 49%-87%), respectively (Figure). Of the 8 relapses, 4 patients were CD19+ and 3 had T315I mutations. Conclusions: Median DFS and OS with dasatinib and blinatumomab in this older group of Ph+ ALL patients remain excellent despite only 1 patient proceeding to an allogeneic transplant. Further correlative studies (single cell transcriptomics and DNA methylation sequencing) are being planned to evaluate predictors of relapse and will be presented at the meeting.

Identification of Individual Risk Factors for Treatment Free Remission (TFR) Failure in Chronic Phase Chronic Myeloid Leukemia (CP-CML) Patients: Predictive Models Developed on a Nationwide Clinical and Claim Database

Introduction Over the past decade, the landscape of CML has been radically improved by the introduction of Tyrosine Kinase Inhibitors (TKI). However, since prolonged TKI treatment would reduce compliance, with associated risk of relapse and progression, and increased toxicities, patients (pts) who achieve and maintain a deep molecular response can now attempt TKI treatment discontinuation to achieve TFR. As TFR attempts may fail due to loss of major molecular response and imply restart of TKI therapy, it is essential to study individual factors associated with TFR outcome and to develop predictive models to provide TFR outcome likelihood with respect to pts' characteristics. Methods Predictive models of TFR failure at 6, 12, 24 and 36 months after TFR attempts were developed on 2 populations: (i) on CP- CML pts managed in a reference center for CML who attempted TFR between January 2003 and January 2023, named CML-pts and (ii) on those CML-pts for which an individual indirect linkage to nationwide claim database succeeded, named CML-linked-pts. The model was thus developed based (i) on clinical data exclusively (demographics, CML characteristics, TKI lines, molecular response), and (ii) on clinical data combined with claim data, which provided information on comorbidities, other treatments than TKI and any healthcare resource use (HCRU) of interest. Correlation and features' predictive power was assessed through Pearson's correlation and predictive power scores (PPS). Logistic regression model and machine learning algorithms (k-nearest neighbor, support vector machine, single decision tree, random forest, multilayer perceptron, and gradient boosting machine) were used. Nested k-fold cross-validation (CV) was used to assess the robustness of the algorithms over all data and hyperparameter optimization was performed. Features' contribution to predict TFR outcomes were assessed using SHAP (“SHapley Additive exPlanations”) values. Results Analysis on (i) 208 CML-pts, who attempted 250 TFR - 208 first attempts (TFR 1), 42 second attempts (TFR 2). Median age was 59.6 (IQR:20.6) and 60.6 (IQR:18.2) years at TFR 1 and TFR 2, respectively, and M/F sex ratio was 1.17 and 1.1. The overall proportion of TFR failure was 35.6%, 43.6%, 46.8% and 48.8% at 6, 12, 24, and 36 months, respectively. Analysis on (ii) 118 CML-linked-ptss, who attempted 134 TFRs (110 TFR 1 24 TFR 2). Median age was 61.5 (IQR: 21.1) and 61.4 (IQR: 12.0) years at TFR 1 and TFR 2, respectively, and M/F sex ratio was 1.04 and 1.18. The proportion of TFR failure was 35.0%, 43.2%, 46.2% and 49.3% at 6, 12, 24 and 36 months, respectively. Studied predictive variables, in both populations (i) and (ii), had little correlation with TFR outcomes, ranging respectively from (i) -0.2 to 0.2 and (ii) -0.16 to +0.31, with poor predictive power (PPS from (i) 0 to 0.19, (ii) 0 to 0.25). Overall, predictive models hardly correctly predicted TFR failure - with sensitivity below 50% and were stronger at rather predicting absence of TFR failure - with specificity above 80%. Best performances were obtained with logistic regression model for both populations, for predicting at 6 and 12 months for population (i) and 6 months for population (ii). Accuracies were 72% for population (i) - with F1-score (i.e., model's ability to predict failure) of 50.0% at 6 months and 69.6% at 24 months -, and 77.8% for population (ii) - with F1-score 66.7% at 6 months. SHAP values showed that attempting a second TFR was the most predictive factor of TFR failure for both populations (i) and (ii) (see Figure 1). Sensitivity analyses considering only TFR 1 in the models showed no improvement in performance. Conclusion Although this study was conducted on one of the largest TFR cohorts ever studied, prediction abilities of the models for TFR failure at the different time points were not sufficient to be proposed as a decision support tool, when developed with either clinical data or with both clinical and claim data. The models were indeed able to predict success but did not manage to find patterns to predict failure; only TFR number had predictive power of TFR outcome. Besides, claim data did not provide HCRU-related predictive factors. Among study limits, this monocentric cohort would reflect homogeneous practices in a same center. Analysis on larger cohorts of patients from different centers would potentially allow the capture of more variability in clinical practices.

KF1601, a Novel Orally Bioavailable Inhibitor of BCR-ABL1 T315I without Inducing Thrombotic Microangiopathy

Targeting Bcr-Abl with tyrosine kinase inhibitors (TKIs) has revolutionized the treatment of chronic myeloid leukemia (CML) by significantly improving patients' survival. However, the gatekeeper mutation T315I confers resistance to TKIs targeting Bcr-Abl, presenting a formidable task in CML's clinical management. Ponatinib significantly reduces the mortality of CML patients with Bcr-Abl T315I, but often accompanies severe, life-threatening side effects. Herein, we report KF1601, a novel orally bioavailable TKI: 1) KF1601 inhibited kinase functions of both Bcr-Abl WT and Bcr-Abl T315I with nanomolar IC 50 values; 2) KF1601 and ponatinib had similar potency in terms of inhibiting CRKL phosphorylation, which correlates to major molecular responses in CML patients. 3) In murine models using Ba/F3 Bcr-Abl T315I cell line, it showed promising in vivo antitumor efficacy, comparable to that of ponatinib; 4) In animal models, it did not cause thrombotic microangiopathy, a major mechanism of ponatinib's toxicity. In summary, KF1601 is a promising drug candidate for safely treating CML patients with drug-resistant Bcr-Abl T315I mutation.

Chronic myeloid leukemia (CML) in children and adolescents-Clinicopathological findings.

Barely two per million Belgian children/adolescents are diagnosed with chronic myeloid leukemia (CML) annually. In this retrospective study, we aimed to investigate the diagnostic features, clinical and laboratory characteristics, and treatment outcome of this rare entity. Medical records of all pediatric CML patients (age ≤ 17 years) diagnosed at the University Hospitals Leuven between 1986 and 2021 were reviewed. Fourteen patients (median age at diagnosis 12.5 years) were included, all presenting in chronic phase. Five patients were diagnosed before 2003; main therapy included hydroxyurea (n = 5/5), interferon-alfa (n = 3/5) and allogeneic hematopoietic stem cell transplantation (allo-Tx) (n = 3/5). Complete hematologic response (CHR), complete cytogenetic response (CCyR) and major molecular response (MMR) was reached in resp. 4/5, 4/5 and in 2/3 of evaluable patients. Three patients progressed to accelerated/blast phase (median time 19 months) and 1/5 is alive and disease-free at last follow-up. Nine patients were diagnosed after 2003 and were treated with first generation (1°G) tyrosine kinase inhibitors (TKI): 3/9 subsequently underwent an allo-Tx, 4/9 were switched to 2°G TKI, one patient was additionally switched to 3°G TKI. CHR, CCyR and MMR was reached in 9/9, 9/9 and 8/9 of these patients. No progression to accelerated/blast phase was observed and none of these patients deceased. At last follow-up, 7/9 patients were in MMR or disease free, the two remaining patients did not reach or lost MMR, both related to compliance issues. Our study confirmed that TKI significantly improved the prognosis of pediatric CML. However, drug compliance poses a considerable challenge.

Cytogenetic and Molecular Remission in Chronic Myeloid Leukemia in Togo

The availability of tyrosine kinase inhibitors (TKIs) in Togo through the GIPAP program has revolutionized the management of chronic myeloid leukemia and increased patient life expectancy. However, diagnosis and molecular monitoring of therapeutic efficacy remain a real challenge due to the inaccessibility of cytogenetic and molecular biology tools. We’ve conducted, a cross-sectional, descriptive study that ran from December 21, 2022, to January 20, 2023, with the aim to evaluate the cytogenetic and molecular remission in CML patients followed at the CHU Campus de Lomé in Togo. Patients diagnosed with chronic-phase CML who had been treated for at least three months with imatinib or dasatinib and had achieved complete hematological remission were included. Dosage of BCR-ABL transcript levels was performed by RQ-PCR in Seattle, USA, using Dried Blood Spot. The transcript detection limit was 0.003% i.e., MR4. A total of 38 patients were included, 68.4% of them were treated with imatinib and 31.6% with dasatinib. In terms of remission, 28.9% had not achieve a partial cytogenetic remission while 15.8% of patients had achieved a MR4 remission and 7.9% a major molecular remission. Major molecular remission was achieved at a mean follow-up time of 95 months for patients taking imatinib and 22 months for those taking dasatinib. Patients in MR4 were on imatinib after a mean of 68 months. All in one, our study showed a high rate of treatment failure. Better access to cytogenetic and molecular biology tools is needed to improve management.

Comparison of BCR::ABL (P210) mRNA levels detected by dPCR and qPCR methods in patients with chronic myeloid leukemia

Objective: To compare digital polymerase chain reaction (dPCR) and real-time quantitative PCR (qPCR) measurements of BCR::ABL (P210) mRNA expression in patients with chronic myeloid leukemia (CML) . Methods: In this non-interventional, cross-sectional study, BCR::ABL (P210) mRNA was simultaneously measured by dPCR and qPCR in peripheral blood samples collected from patients with CML who underwent tyrosine kinase inhibitor therapy and who achieved at least a complete cytogenetic response from September 2021 to February 2023 at Peking University People's Hospital. The difference, correlation, and agreement between the two methods were evaluated using the Wilcoxon signed-rank test, Spearman's correlation, and Bland-Altman analysis, respectively. Results: In total, 459 data pairs for BCR::ABL mRNA expression measured by dPCR and qPCR from 356 patients with CML were analyzed. There was a significant difference in BCR::ABL mRNA expression between the two methods (P<0.001). When analyzed by the depth of the molecular response (MR), a significant difference only existed for patients with ≥MR4.5 (P<0.001). No significant difference was observed for those who did not achieve a major MR (no MMR; P=0.922) or for those who achieved a major MR (MMR; P=0.723) or MR4 (P=0.099). There was a moderate correlation between the BCR::ABL mRNA expression between the two methods (r=0.761, P<0.001). However, the correlation gradually weakened or disappeared as the depth of the MR increased (no MMR: r=0.929, P<0.001; MMR: r=0.815, P<0.001; MR4: r=0.408, P<0.001; MR4.5: r=0.176, P=0.176). In addition, the agreement in BCR::ABL mRNA expression between the two methods in those with MR4.5 was weaker than other groups (no MMR: ▉= 0.042, P=0.846; MMR:▉=0.054, P=0.229; MR4:▉=-0.020, P=0.399; MR4.5:▉=-0.219, P<0.001) . Conclusions: dPCR is more accurate than qPCR for measuring BCR::ABL (P210) mRNA expression in patients with CML who achieve a stable deep MR.

Comparison of Clinicopathological Parameters, and Treatment Responses in Younger and Older Chronic Myeloid Leukaemia Patients Treated with Imatinib

Introduction: Differences in baseline characteristics and response to treatment in different age groups of patients with chronic myeloid leukaemia (CML) in resource-limited countries have not been extensively studied. We aimed to determine the differences in clinicopathological parameters at diagnosis and response to imatinib in adult CML patients with younger (under 60 years; YCML) and older (60 years and older; OCML) age treated at our institution from March 2001 to March 2021. Methods: A retrospective analysis of consecutive adult CML patients receiving imatinib was performed. Clinicopathological parameters and treatment response were reviewed and analysed using hospital medical records and electronic data reports. Results: The median age at diagnosis was 50 years. OCML patients (n=17) had significantly more comorbidities. The YCML group (n=50) generally had a palpable spleen &gt;5cm from the costal margin, mild anaemia, hyperleukocytosis and thrombocytosis. A starting dose of 400 mg/day was observed in 84% of YCML and in 65% of OCML. Cumulative complete cytogenetic response was 50% in YCML versus 70.6% in OCML, p=0.158. OCML tended to have a higher percentage of major molecular response (MMR) (52.9% versus 32%) and a shorter time to MMR, 22 months (range 5-70) versus 35 months (range 8-53). OCML experienced more haematological and non-haematological treatment-related adverse events after imatinib therapy. Conclusion: Although OCML patients had more comorbidities and treatment intolerances, overall long-term treatment response was comparable to YCML. In OCML, a more personalised approach to initial and subsequent dosing of imatinib may be considered.

With up to 8 Years of Therapy, Asciminib (ASC) Monotherapy Demonstrated Continued Favorable Efficacy, Safety, and Tolerability in Patients (Pts) with Philadelphia Chromosome-Positive Chronic Myeloid Leukemia in Chronic Phase (Ph+ CML-CP) without the T315I Mutation: Final Results from the Phase 1 X2101 Study

CONCLUSIONS Tyrosine kinase inhibitors (TKIs) have extended the life expectancy for pts with CML, approximating that of the general population, and established BCR::ABL1-targeted therapies as the standard of care for CML. However, multi-TKI resistance and intolerance remain challenges that may lead to treatment (Tx) discontinuation. ASC is the first and only approved BCR::ABL1 inhibitor that Specifically Targets the ABL Myristoyl Pocket (STAMP) with higher selectivity for ABL, reducing off-target effects seen with TKIs. A follow-up analysis (median exposure: 4.2 y) of the phase 1 ASC study in pts with CML-CP without T315I after receiving ≥2 TKIs demonstrated durable efficacy and favorable tolerability, with nearly one-third of pts achieving deep molecular response by cutoff (Jan 6, 2021). Here we present final end-of-study (EOS) efficacy and safety results from the phase 1 ASC study in pts with CML-CP without the T315I mutation (cutoff: Mar 14, 2023). This analysis included adults with Ph+ CML-CP without the T315I mutation and an ECOG performance status of 0-2 who had relapsed disease or were refractory to or intolerant of ≥2 prior TKIs. Pts received ASC monotherapy at starting doses of 10-200 mg twice daily (BID) or 80-200 mg once daily (QD). The study started with dose escalation to estimate the maximum tolerated dose (MTD), followed by expansion to establish safety and tolerability of ASC. Dose adjustments were allowed if pts did not tolerate the dosing schedule. The EOS was declared when all pts completed ≥64 wks within the study or discontinued Tx; pts continuing to receive ASC at the EOS were provided continued access to ASC. A total of 115 pts were enrolled between Apr 2014 and Mar 2023. Across all starting doses, the median exposure duration was 5.9 y, with a maximum exposure of 8.4 y; 112 pts (97.4%) had received ≥2 prior TKIs and 82 (71.3%) had received ≥3 prior TKIs. By data cutoff, 70 pts (60.9%) who completed the study on ASC were provided continued access to ASC. Among 45 pts who ended Tx early, 15 (13.0%) and 8 (7.0%) ended due to adverse events (AEs) and disease progression, respectively. Efficacy of ASC at EOS was sustained and consistent with previous reports, with the majority of pts (65.1%) achieving major molecular response (MMR) by the cutoff. While most responses were observed by wk 48, cumulative MMR rates continued to increase up to wk 144 (Figure 1). The median time to MMR (range) was 58.3 (2-360) wks among pts who achieved MMR but were not in MMR at screening. Among the 56 pts who achieved MMR, 50 maintained or improved the response up to data cutoff. At wks 24, 48, and 96, respectively, 18.9%, 17.9%, and 23.6% of pts achieved MR 4 and 13.2%, 15.1%, and 18.9% achieved MR 4.5. Safety and tolerability of ASC improved with longer durations of exposure. The most frequent all-grade AEs included arthralgia (40.9%), increased lipase (39.1%), fatigue (38.3%), and headache (38.3%), and only 13.0% of pts experienced AEs leading to Tx discontinuation. Even with longer durations of Tx, AEs were less likely to occur after the first year on ASC (Figure 2). The safety and tolerability of ASC remained consistent with prior analyses; there were no new or worsening safety issues compared with those already known for ASC and no new on-Tx deaths. The MTD of ASC was not reached. Based on safety, tolerability, efficacy, and pharmacokinetic data, ASC 40 mg BID was selected as the recommended dose for expansion in adults with CML-CP without the T315I mutation. In this final analysis of the phase 1 ASC trial in pts with CML-CP without the T315I mutation, ASC continued to show favorable efficacy and sustained safety and tolerability over a median exposure duration of 5.9 y, with a maximum exposure of 8.4 y. Pts achieved high rates of MMR with nearly one-fourth of pts achieving deep molecular responses at wk 96, demonstrating durable efficacy of ASC over time. Even with longer exposures, the risk of AEs did not increase and there were no new or worsening safety issues. With ASC, most AEs occurred early, and no new late-emerging safety issues were seen, supporting ASC as a safe and tolerable long-term Tx, highly clinically relevant in the management of resistant/intolerant CML-CP. Based on results from this and the ASCEMBL study, 40 mg BID and 80 mg QD have since been approved for use in this pt population.

Efficacy of Consolidation Therapy with Ponatinib 15mg on Treatment-Free Remission Rate in Patients with Chronic Myeloid Leukemia. Results of the Ponazero Trial

Introduction: Discontinuation of tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML) has become part of routine clinical practice in recent years, thanks to growing evidence on their feasibility and safety. However, and despite adequate patient selection based on current recommendations, loss of response is observed in approximately 50% of patients. In this scenario, efforts are focused on finding strategies to increase the rate of successful discontinuations. Ponatinib has shown to induce deeper molecular responses compared with imatinib, but its risk of arterial occlusive events (AOE) limits its use in first line at its standard dose of 45mg. The risk of AOEs appears to be dose-related and following the results of the OPTIC study, dose reduction to 15mg in patients with good response is an increasingly popular strategy. Under these premises it has been postulated that a consolidation with ponatinib 15mg may increase the proportion of patients who could discontinue treatment successfully. Our aim is to evaluate the efficacy and safety of one year of consolidation therapy with ponatinib 15mg on treatment-free remission (TFR) rate in patients with CML who have achieved a deep molecular response with imatinib. Material and Methods: A multicenter open-label, single-arm, phase II, exploratory, prospective clinical trial (NCT 04043676) was conducted including patients with philadelphia-positive CML who met discontinuation criteria according to European LeukemiaNet recommendations, had received 4 years or more of imatinib therapy, with a documented grade 4 molecular response (MR4) at least 12 months prior to study entry. Uncontrolled arterial hypertension, active cardiovascular disease, or concomitant medication with potential for QTc prolongation were exclusion criteria. The study has two main phases: ponatinib consolidation (48 weeks), and ponatinib TFR phase (48 weeks); where patients remain without treatment. During the TFR phase, patients with a confirmed loss of MR4 or a single value above major molecular response (MMR) were scheduled to restart treatment with a TKI at investigator's discretion. The present abstract reports the results of the primary endpoint of the study; the proportion of patients with no loss of MR4 at the end of the TFR phase. Results: A total of 23 patients started treatment with ponatinib 15mg. One patient subsequently failed screening due to a major protocol deviation. Baseline patient characteristics were as follows: median age was 51.8 years (range 26-74), 65.2% were male. Ninety-five percent were Caucasian and 5% were Hispanic, ECOG was 0 in 83% and 1 in 17%, Sokal was low in 69.5%, intermediate in 17.5% and unknown in 13%. Eighteen patients were receiving imatinib 400mg daily (82%) at study entry, 2 patients 800mg and two 200mg. Median time on prior imatinib was 10 years (range 4-17), with a median time on MR4 of 3.6 years (range 1.9-13.3). Prior to initiation 13 patients (56.5%) had a grade 5 molecular response, 4 had a 4.5 molecular response (26%) and the remainder had a MR4. The adverse events (AEs) reported with ponatinib are summarized in Table 1, the most frequent being constipation (30%), asthenia (26%), myalgias and arthralgias (26% respectively) and skin rash (17%). A high rate of SARS-CoV2 infections was reported during the treatment period (26%), which should be interpreted considering that the study took place during the COVID-19 pandemic. Three patients out of 22 (13.6%) had serious AEs with ponatinib leading to treatment discontinuation; thrombophlebitis, erectile dysfunction, and intermittent claudication. Of the patients who entered the TFR phase, 14/19 (74%) continue with MMR without requiring treatment after a median follow-up of 12 months (68% with MR4) (table 1). Six patients (31%) lost MR4, five of them required reintroduction of an TKI (4 imatinib, 1 dasatinib; median time to reintroduction 5.4 months). All patients with MR4 loss were receiving the 400 mg dose of imatinib at study entry. All patients who restarted treatment recovered MMR. The sixth patient lost MR4 while maintaining an MMR without requiring treatment reinduction to date. Conclusions: Consolidation with 12 months of ponatinib 15mg in this study shows a high discontinuation success rate with an adequate safety profile, although not free of AEs. The results make this approach attractive for the design of further randomized clinical trials.

Tyrosine Kinase Inhibitor Withdrawal Syndrome in Chronic Myeloid Leukemia Patients Participants of Two Discontinuation Clinical Trials

Discontinuation of tyrosine kinase inhibitors (TKI) is currently one of the main goals in CML treatment. One of the known adverse events after TKI discontinuation is withdrawal syndrome (WS), which can occur in about 30% of patients (pts), characterized by musculoskeletal pain that begins or worsens weeks after interruption and may be more severe in some cases, but rarely leading to the need for TKI reintroduction. Some studies suggest TKI dose reduction or optimization before stopping treatment may reduce WS rates. Aims: To estimate the incidence of WS after TKI discontinuation in CML in two clinical trials and to correlate the incidence of these events with patients' characteristics and molecular relapse-free survival (MRFS). Methods: We analyzed two cohorts of CML patients of two prospective, single-arm, phase II clinical trials: EDI-PIO (Clinicaltrials.gov: NCT02852486) and DES-CML (ReBEC UTN code : U1111-1252-7312). In both trials, inclusion criteria were CML in the chronic phase, treated with TKI for at least three years, and with deep molecular response (MR4.5) for two years. In the first trial, TKI was discontinued after using three months of pioglitazone, and in the DES-CML trial, after reducing the dose of the TKI by 50% for six months before discontinuation. TKI was reintroduced if the patient lost MR4.0 (EDI-PIO trial) or major molecular response (MMR) (DES-CML trial). Adverse events related to WS were evaluated until the fourth month after discontinuation. WS was defined as the onset of new musculoskeletal pain and/or an increase in pre-existing pain and/or the need to start any pain medication. The adverse event classification followed the Common Terminology Criteria (CTCAE- Version 4.0), musculoskeletal and connective tissue disorder. The data were collected and stored using the REDcap Platform (by Vanderbilt). MRFS was defined by discontinuation date until the last seen date or loss of MR4.0/MMR. The Kaplan-Meier method was applied for OS, whereas Log-Rank tests were applied to compare its curves. All statistical analysis were done by IBM-SPSS v. 24 and considered significant p-value &amp;lt; 5%. Results: Between September 2016 and April 2023, we analyzed 63 patients, 32 from the DES-CML study and 31 from the EDI-PIO trial. The median age at discontinuation was 58 years (24-79), 59% male, 52% Sokal low-risk, 35% intermediate, and 13% high; at discontinuation, 94% of the patients were using Imatinib, 3% Dasatinib, 1.5% Bosutinib and 1.5% Nilotinib. The median duration of TKI treatment until discontinuation was 10 years (3-20). Withdrawal syndrome occurred in 41% of cases and was more frequent in females (58% vs. 42%, P=0.02). Fourteen pts from the EDI-PIO study (45%) and 12 (37.5%) from DES-CML developed WS (P=0.61). According to CTCAE, the events were classified as grade 1, 36%, and 33%, while grade 2 was 57% and 58%; and grade 3 was 7% and 8% (P=0.90), respectively, in EDI-PIO and DES-CML trials. Symptoms started at month 1 in 20% of the patients and 73% in months 2 and 3. Seventeen (30%) pts used anti-inflammatory drugs, analgesics, steroids, or muscle relaxants (64% EDI-PIO vs. 66% DES-CML, P=0.90). There was no need to reintroduce TKI for treating WS. Molecular relapse free-survival (MRFS) at 12 months was 72% (95% CI 60-84%), with no difference by protocol (75% DES-CML, 70% EDI-PIO). MRFS at 12 months was 73% and 74% in the group with or without WS, respectively (P=NS). Conclusions: The incidence and severity of WS were similar in the two trials, corroborating data from the literature. WS was more frequent in females. The dose reduction did not reduce WS rates. However, this condition was self-limited and managed with drugs, without reintroducing TKI. There was no difference in MRFS between the groups with or without WS.

Sustained Efficacy and Safety with Asciminib (ASC) after Almost 4 Years of Median Follow-up from Ascembl, a Phase 3 Study of ASC Vs Bosutinib (BOS) in Patients (Pts) with Chronic Myeloid Leukemia in Chronic Phase (CML-CP) after ≥2 Prior Tyrosine Kinase Inhibitors (TKIs): An End of Study Treatment (EOS Tx) Update, Including Results from Switch Population

CONCLUSIONS CML requires chronic therapy, emphasizing the need for Txs that are characterized by high, durable efficacy and a low adverse event (AE) burden. ASC, the first BCR::ABL1 inhibitor Specifically Targeting the ABL Myristoyl Pocket (STAMP), demonstrated significantly superior efficacy and better safety/tolerability compared with BOS in pts with CML-CP who received ≥2 prior TKIs in the phase 3 ASCEMBL study. Major molecular response (MMR) rate was 25.5% with ASC vs 13.2% with BOS at wk 24, meeting the primary objective, and 37.6% vs 15.8% at wk 96, meeting the key secondary objective. Despite the longer duration of exposure to ASC, safety/tolerability remained consistently better with ASC vs BOS, with fewer all-grade and grade ≥3 AEs and AEs leading to Tx discontinuation observed. After a median follow-up of 3.7 y, we report EOS Tx results from ASCEMBL (cutoff: March 22, 2023). We also report the first available data from pts who experienced Tx failure on BOS and switched to ASC. Adults (aged ≥18 y) with CML-CP after ≥2 prior TKIs, with intolerance or lack of efficacy per 2013 ELN recommendations were randomized 2:1 to receive either ASC 40 mg twice daily or BOS 500 mg once daily. Pts who met Tx failure criteria per 2013 ELN while on BOS could switch to ASC and were analyzed separately. Pts who discontinued BOS due to intolerance could not switch. EOS will occur 5 y from when the last enrolled pt received first Tx dose. A total of 233 pts were randomized to ASC (n=157) or BOS (n=76). The most common reason for discontinuation was lack of efficacy in 40 (25.5%) pts on ASC and 28 (36.8%) on BOS. At the time of EOS Tx cutoff, Tx with ASC and BOS was ongoing in 77 (49.4%) and 8 (10.5%) pts, respectively; pts deriving benefit from study Tx at EOS TX, per investigator assessment, continued receiving posttrial access. MMR rate at wk 156 continued to be higher with ASC (33.8%) than with BOS (10.5%) (Figure 1). The difference after adjusting for baseline (BL) major cytogenetic response was 23.2%(95% CI, 13.1%-33.2%; 2-sided P&amp;lt;.001). The BCR::ABL1IS ≤1% rate at wk 156 in pts without this level of response at BL also continued to be higher with ASC (43.0%) than with BOS (11.1%). Despite the longer median duration (range) of exposure to ASC (156.0 [0.1-256.3] wk) vs BOS (30.5 [1.0-239.3] wk), safety/tolerability of ASC continued to be better compared with BOS and were consistent with previous analyses. Two new pts had AEs leading to Tx discontinuation since the wk 96 cutoff (1 pt on ASC reported pregnancy; 1 pt on BOS reported diarrhea), and rates remained lower with ASC vs BOS (8.3% vs 27.6%). The most frequent (≥10%) grade ≥3 AEs with ASC vs BOS were thrombocytopenia (22.4% vs 9.2%), neutropenia (18.6% vs 14.5%), diarrhea (0% vs 10.5%), and increased alanine aminotransferase (0.6% vs 14.5%). Most AEs occurred within the first 6 months (Figure 2). Exposure-adjusted incidence rates of arterial occlusive events (AOEs) with ASC decreased since the wk 96 cutoff, from 3.0 to 2.2 per 100 pt-y, and no new AOEs occurred with ASC, indicating that the risk of AOEs did not increase over time. Among pts who discontinued Tx due to lack of efficacy or disease progression, no new mutations occurred since the wk 96 cutoff. Of 28 pts who discontinued BOS for lack of efficacy, 25 switched to ASC. Almost all switch pts (96%) had BL BCR::ABL1IS &amp;gt;10% prior to switch. No switch pts achieved MMR at or by wk 48 post switch. However, at wk 48, 24% achieved BCR::ABL1IS ≤10% and 8% achieved BCR::ABL1IS ≤1%. The safety profile of ASC in switch pts was consistent with that in pts receiving ASC in the randomized period. Most frequent (≥10%) grade ≥3 AEs were neutropenia (32.0%) and thrombocytopenia (24.0%). AEs leading to Tx discontinuation occurred in 8.0% of switch pts. With almost 4 y of follow-up in ASCEMBL, ASC continued to show greater efficacy and better safety/tolerability than BOS in pts with CML-CP after ≥2 prior TKIs. The robust safety profile of ASC was sustained through each analysis in ASCEMBL (wk 24, wk 96, and EOS Tx), confirming that pts receiving ASC can maintain a high level of response and continue Tx without experiencing late-emerging AEs. Results in the switch population support the use of ASC early in the Tx paradigm. ASCEMBL EOS Tx results continue to strongly support ASC as the therapy of choice for pts with suboptimal responses and/or intolerance to ≥2 prior TKIs, allowing more pts to remain on Tx and achieve their Tx goals without needing to switch.