Influence of genetic polymorphisms on imatinib concentration and therapeutic response in patients with chronic-phase chronic myeloid leukemia.

BACKGROUND: Diminished bioavailability of imatinib in leukemic cells contributes to poor clinical response. We examined the impact of genetic polymorphisms of imatinib on the pharmacokinetics and clinical response in 190 patients with chronic myeloid leukaemia (CML). METHODS: Single nucleotide polymorphisms were genotyped using pyrophosphate sequencing. Plasma trough levels of imatinib were measured using liquid chromatography-tandem mass spectrometry. RESULTS: Patients carrying the TT genotype for ABCB1 (rs1045642, rs2032582, and rs1128503), GG genotype for CYP3A5-rs776746 and AA genotype for ABCG2-rs2231142 polymorphisms showed higher concentration of imatinib. Patients with T allele for ABCB1 (rs1045642, rs2032582, and rs1128503), A allele for ABCG2-rs2231142, and G allele for CYP3A5-rs776746 polymorphisms showed better cytogenetic response and molecular response. In multivariate analysis, carriers of the CYP3A5-rs776746 G allele exhibited higher rates of complete cytogenetic response (CCyR) and major molecular response (MMR). Similarly, patients with the T allele of ABCB1-rs1045642 and rs1128503 demonstrated significantly increased CCyR rates. Patients with the A allele of ABCG2-rs2231142 were associated with higher MMR rates. The AA genotype for CYP3A5-rs776746, and the CC genotype for ABCB1-rs104562, and rs1128503 polymorphisms were associated with a higher risk of imatinib failure. Patients with the G allele for CYP3A5-rs776746 exhibited a higher incidence of anemia, and T allele for ABCB1-rs2032582 demonstrated an increased incidence of diarrhea. CONCLUSIONS: Genotyping of ABCB1, ABCG2, and CYP3A5 genes may be considered in the management of patients with CML to tailor therapy and optimize clinical outcomes.

Incidence of pleural effusion with dasatinib and the effect of switching therapy to a different TKI in patients with chronic phase CML.

Dasatinib is one of the second generation tyrosine kinase inhibitors (TKI) which is approved for the treatment of patients with chronic phase CML (CP-CML) both in the front line and in the second line setting. Pleural effusion (PE) is a unique toxicity associated with dasatinib use. Our aim was to study the incidence of pleural effusion in our cohort of patients who were treated with dasatinib for CP-CML and the safety upon TKI switch. A total of 390 patients were treated with dasatinib during their course of treatment for CP-CML. A total of 69 patients (17.6%) developed any grade of PE. About 33 (48%) patients developed CTCAE grade 2 PE, 34 (49%) grade 3 and only 1 patient developed grade 4 PE. Recurrence of PE was observed in 34 (49%) patients. While only 12 patients (17.3%) continued using dasatinib after development of PE, dasatinib was discontinued in the other 57 patients. Therapy was switched to bosutinib in 13 patients out of which 6 (46%) patients re-developed PE. While only 12.5% patients developed re-accumulation of pleural fluid in patients switched to imatinib, none of the patients switched to nilotinib re-developed PE. A change in TKI to bosutinib was associated with a 46% risk of recurrence of PE in patients who develop PE on dasatinib for the treatment of CP-CML. The incidence of recurrent PE was markedly lower in patient switched to imatinib or nilotinib.

Efficacy and safety of bosutinib in patients treated with prior imatinib and/or dasatinib and/or nilotinib: Subgroup analyses from the phase 4 BYOND study.

The BYOND study evaluated the efficacy and safety of bosutinib 500 mg once daily in patients with chronic myeloid leukemia (CML) resistant/intolerant to prior tyrosine kinase inhibitors (TKIs). These post-hoc analyses assessed the efficacy and safety of bosutinib by resistance or intolerance to prior TKIs (imatinib-resistant vs dasatinib/nilotinib-resistant vs TKI-intolerant), and cross-intolerance between bosutinib and prior TKIs (imatinib, dasatinib, nilotinib), in patients with Philadelphia chromosome-positive chronic phase CML. Data are reported after ≥3 years' follow-up. Of 156 patients with Philadelphia chromosome-positive chronic phase CML, 53 were imatinib-resistant, 29 dasatinib/nilotinib-resistant, and 74 intolerant to all prior TKIs; cumulative complete cytogenetic response rates at any time were 83.7%, 61.5%, and 86.8%, and cumulative major molecular response rates at any time were 72.9%, 40.7%, and 82.4%, respectively. Of 141, 95, and 79 patients who received prior imatinib, dasatinib, and nilotinib, 64 (45.4%), 71 (74.7%), and 60 (75.9%) discontinued the respective TKI due to intolerance; of these, 2 (3.1%), 5 (7.0%), and 0 had cross-intolerance with bosutinib. The response rates observed in TKI-resistant and TKI-intolerant patients, and low cross-intolerance between bosutinib and prior TKIs, further support bosutinib use for patients with Philadelphia chromosome-positive chronic phase CML resistant/intolerant to prior TKIs. TRIAL REGISTRATION: ClinicalTrials.gov: NCT02228382.

Navigating the Management of Chronic Phase CML in the Era of Generic BCR::ABL1 Tyrosine Kinase Inhibitors.

Over the past several years, advances in research, treatment, and market dynamics have impacted treatment strategies in chronic myeloid leukemia in chronic phase (CML-CP). They include the broader availability of cost-effective generic imatinib, and soon other generic second-generation tyrosine kinase inhibitors (TKIs). Access to affordable generics means that all patients with CML-CP should have access to safe and highly effective lifelong therapies. When overall survival is the treatment endpoint, imatinib provides a good treatment value. Second-generation TKIs may be the best frontline strategy when treatment-free remission is the goal. Recent studies have shown maintained efficacy and reduced toxicity when TKIs are used at reduced dosing. Reduced-dose schedules of second-generation TKIs (which are less toxic and induce faster deep molecular responses) may render generic second-generation TKIs a more attractive treatment option. Adjusting the dose of TKI in the presence of mild-to-moderate, or even severe but reversible, adverse events may be preferable to switching to a different TKI. The selection of second-line and beyond therapies depends on the evolving patterns observed with frontline treatment. Dose-adjusted ponatinib schedules have demonstrated improved efficacy and safety in patients resistant to second-generation TKIs or those with T315I-mutated disease. For asciminib, longer-term follow-up is needed to better evaluate its safety and efficacy compared with ponatinib. Allogeneic stem cell transplantation represents a valid alternative to newer-generation TKIs, with a better treatment value when TKIs are priced at >$40,000/year.

Chronic Myeloid Leukemia, Version 2.2024, NCCN Clinical Practice Guidelines in Oncology.

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.

Chronic myeloid leukemia diagnosed in pregnancy: management and outcome of 87 patients reported to the European LeukemiaNet international registry.

The management of chronic myeloid leukemia (CML) diagnosed during pregnancy is a rare and challenging situation. We report the treatment and outcome of 87 cases diagnosed in chronic phase from 2001-2022 derived from the largest international observational registry, supported by the European LeukemiaNet (ELN), of 400 pregnancies in 299 CML women. Normal childbirth occurred in 76% without an increased rate of birth abnormalities or life-threatening events, including in patients untreated or treated with interferon-α and/or imatinib in 2nd-3rd trimester. The low birth weight rate of 12% was comparable to that seen in the normal population. Elective and spontaneous abortions occurred in 21% and 3%, respectively. The complete hematologic response rate before labor was 95% with imatinib and 47% with interferon only. No disease progression during pregnancy was observed, 28% of the patients switched their therapy at varying times after delivery. Treatment options balance the efficacy and safety for mother and infant: interferon-α can commence in the 1st trimester and continued throughout in cases of good disease control and tolerability. Because of limited placental crossing, selected tyrosine kinase inhibitors (imatinib and nilotinib) seem to be safe and effective options in 2nd and 3rd trimester while hydroxycarbamide offers few benefits.

Prognostic Impact of Bone Marrow Fibrosis and Effects of Tyrosine Kinase Inhibitors on Bone Marrow Fibrosis in Chronic Myeloid Leukemia.

BACKGROUND: Myelofibrosis is reported in around 40% of newly diagnosed chronic myeloid leukemia (CML) patients and have an important role in the pathobiology and prognosis of CML. This retrospective study aimed to evaluate the effects of bone marrow (BM) fibrosis on disease prognosis and the effects of specific tyrosine-kinase inhibitors (TKIs) on BM fibrosis in CML patients. METHODS: The study included 96 patients (>18 years) diagnosed with chronic phase (CP) CML. The clinical and demographic information were collected from the medical files. Post-treatment BM aspirate and core biopsy samples were analyzed for the presence of fibrosis and dysplasia. RESULTS: The mean age of the study patients was 52.69 years; 47.9% of the patients were female. At the onset, 53 (63.1%) patients had BM fibrosis. The difference in the overall survival of the patients with respect to BM fibrosis grades was significant (p = .001). Within the BM fibrosis grade groups, there were significant differences between grade 0 vs. grade 2, grade 0 vs. grade 3, and grade 1 vs. grade 3 (p = .005, p = .002, and p = .003 respectively) There was no significant association between the presence of BM fibrosis at the onset and not responding to first-line therapy (p = .724). Moreover, no significant association was found between the presence of BM fibrosis at the onset and molecular (p = .623) or cytogenetic response (p = .535) to first-line therapy. Additionally, the association between the type of second-line and third-line therapy and molecular response (p = .773 and p = .424, respectively) or cytogenetic response (p = .298 and p = .641) was not significant. CONCLUSION: Although BM fibrosis seems to be a crucial complication of CML with a poor prognosis, it can be reversed via TKI treatment which may result in improved survival. It might be considered to check the BM for this complication on a regular basis during therapies to test its prognostic influence in CML patients in prospective controlled trials. Further studies focused on this issue are required to utilize BM fibrosis as a candidate prognostic factor.

Dose modification dynamics of ponatinib in patients with chronic-phase chronic myeloid leukemia (CP-CML) from the PACE and OPTIC trials.

Ponatinib, the only approved all known-BCR::ABL1 inhibitor, is a third-generation tyrosine-kinase inhibitor (TKI) designed to inhibit BCR::ABL1 with or without any single resistance mutation, including T315I, and induced robust and durable responses at 45 mg/day in patients with CP-CML resistant to second-generation TKIs in the PACE trial. However, cardiovascular toxicities, including arterial occlusive events (AOEs), have emerged as treatment-related AEs within this class of TKIs. The OPTIC trial evaluated the efficacy and safety of ponatinib using a novel, response-based, dose-reduction strategy in patients with CP-CML whose disease is resistant to ≥2 TKIs or who harbor T315I. To assess the dose-response relationship and the effect on the safety of ponatinib, we examined the outcomes of patients with CP-CML enrolled in PACE and OPTIC who received 45 mg/day of ponatinib. A propensity score analysis was used to evaluate AOEs across both trials. Survival rates and median time to achieve ≤1% BCR::ABL1IS in OPTIC were similar or better than in PACE. The outcomes of patients with T315I mutations were robust in both trials. Patients in OPTIC had a lower exposure-adjusted incidence of AOEs compared with those in PACE. This analysis demonstrates that response-based dosing for ponatinib improves treatment tolerance and mitigates cardiovascular risk.

Impact of age and comorbidities on the efficacy and tolerability of bosutinib in previously treated patients with chronic myeloid leukemia: results from the phase 4 BYOND study.

In the phase 4 BYOND trial, patients with pretreated chronic myeloid leukemia (CML) received bosutinib (starting dose: 500 mg/day). Efficacy and safety after ≥3 years of follow-up in 156 patients with Philadelphia chromosome-positive chronic phase CML by age and Charlson Comorbidity Index scores (without the age component; mCCI) is reported. Cumulative major molecular response rates at any time on treatment were 73.6%, 64.5%, and 74.1% in patients <65, 65-74, and ≥75 years of age, and 77.9%, 63.0%, and 59.3% in patients with mCCI scores 2, 3, and ≥4, respectively. Patients <65, 65-74, and ≥75 years of age experienced grade 3/4 treatment-emergent adverse events (TEAEs) at rates of 74.7%, 78.8%, and 96.4% and permanent discontinuations due to AEs at rates of 22.1%, 39.4%, and 46.4%, respectively. In patients with mCCI 2, 3, and ≥4, respective rates of grade 3/4 TEAEs were 77.8%, 77.8%, and 86.7%, and permanent discontinuations due to AEs were 25.3%, 33.3%, and 43.3%. In conclusion, a substantial proportion of patients maintained/achieved cytogenetic and molecular responses across age groups and mCCI scores. Older patients (≥75 years) and those with high comorbidity burden (mCCI ≥4) may require more careful monitoring due to the increased risk of TEAEs. Clinicaltrials.gov: NCT02228382.

[Optimizing the use of bosutinib in patients with chronic-phase chronic myeloid leukemia: Recommendations of a panel of experts from the Fi-LMC (French CML working group)]. / Optimisation du bosutinib dans la leucémie myéloïde chronique : recommandations du Fi-LMC (France Intergroupe des leucémies myéloïdes chroniques).

The treatment of chronic myeloid leukemia relies on orally available tyrosine kinase inhibitors targeting the BCR::ABL1 oncoprotein. Bosutinib is a second generation adenosine triphosphate-competitive inhibitor approved for use in frontline adult chronic phase-chronic myeloid leukemia and all phases-chronic myeloid leukemia in the second line setting or beyond. Its efficacy was demonstrated in several pivotal clinical trials at 400mg once daily in the first line context and at 500mg once daily beyond first line. Bosutinib-related adverse events frequently occur early after treatment initiation and include gastro-intestinal symptoms and cytolytic hepatitis. These drug-related adverse events must be properly managed in order to preserve safety, efficacy and treatment acceptability. The French chronic myeloid leukemia study group gathered a panel of experts in hematology, pharmacology and hepatology in order to elaborate practical recommendations on the management of bosutinib treatment. These recommendations aim at optimizing the short and long-term tolerance and benefit/risk balance of bosutinib, mainly focusing at gastro-intestinal and liver toxicities.

Bosutinib in Resistant and Intolerant Pediatric Patients With Chronic Phase Chronic Myeloid Leukemia: Results From the Phase I Part of Study ITCC054/COG AAML1921.

PURPOSE: Bosutinib is approved for adults with chronic myeloid leukemia (CML): 400 mg once daily in newly diagnosed (ND); 500 mg once daily in resistant/intolerant (R/I) patients. Bosutinib has a different tolerability profile than other tyrosine kinase inhibitors (TKIs) and potentially less impact on growth (preclinical data). The primary objective of this first-in-child trial was to determine the recommended phase II dose (RP2D) for pediatric R/I and ND patients. PATIENTS AND METHODS: In the phase I part of this international, open-label trial (ClinicalTrials.gov identifier: NCT04258943), children age 1-18 years with R/I (per European LeukemiaNet 2013) Ph+ CML were enrolled using a 6 + 4 design, testing 300, 350, and 400 mg/m2 once daily with food. The RP2D was the dose resulting in 0/6 or 1/10 dose-limiting toxicities (DLTs) during the first cycle and achieving adult target AUC levels for the respective indication. As ND participants were only enrolled in phase II, the ND RP2D was selected based on data from R/I patients. RESULTS: Thirty patients were enrolled; 27 were evaluable for DLT: six at 300 mg/m2, 11 at 350 mg/m2 (one DLT), and 10 at 400 mg/m2 (one DLT). The mean AUCs at 300 mg/m2, 350 mg/m2, and 400 mg/m2 were 2.20 µg h/mL, 2.52 µg h/mL, and 2.66 µg h/mL, respectively. The most common adverse event was diarrhea (93%; ≥grade 3: 11%). Seven patients stopped because of intolerance and eight because of insufficient response. Complete cytogenetic and major molecular response to bosutinib appeared comparable with other published phase I/II trials with second-generation TKIs in children. CONCLUSION: Bosutinib was safe and effective. The pediatric RP2D was 400 mg/m2 once daily (max 600 mg/d) with food in R/I patients and 300 mg/m2 once daily (max 500 mg/d) with food in ND patients, which achieved targeted exposures as per adult experience.

Real-World Effectiveness of Dasatinib Versus Imatinib in Newly Diagnosed Patients With Chronic Myeloid Leukemia.

INTRODUCTION: Limited data exist comparing dasatinib with imatinib in clinical practice. This study assessed real-world outcomes associated with first-line (1L) dasatinib or imatinib treatment of chronic myeloid leukemia (CML). PATIENTS AND METHODS: This retrospective, observational, United States multisite cohort study analyzed electronic medical record data from adults with Philadelphia chromosome-positive (Ph+) CML in the chronic phase (CML-CP) after 1L dasatinib or imatinib between January 2014 and September 2018. Rates of and times to major molecular response (MMR) and deep molecular response (DMR) were assessed overall and in subgroups (low vs. intermediate/high risk, aged <65 vs. ≥65 years, low/normal vs. high body mass index [BMI]). RESULTS: The dasatinib cohort (n = 309) experienced higher rates of MMR (n = 304, 79% vs. 65%, P < .001) and DMR (44% vs. 25%, P < .001) vs. the imatinib cohort with shorter median times to MMR (11.9 vs. 14.7 months, P < .001) and DMR (30.3 vs. 66.1 months, P < .001). Patients with intermediate-/high-risk disease and those aged <65 years had higher MMR and DMR rates and achieved response earlier with dasatinib (P < .01). Patients with low-risk disease treated with dasatinib had higher rates of DMR (60% vs. 32%, P = .01). Across BMI strata, rates of MMR and DMR were higher with dasatinib (P < .05). CONCLUSIONS: Patients with CML-CP treated with 1L dasatinib achieved higher rates of, with shorter times to, MMR and DMR versus 1L imatinib. These clinically meaningful improvements were observed across subgroups.

[To compare the efficacy and incidence of severe hematological adverse events of flumatinib and imatinib in patients newly diagnosed with chronic phase chronic myeloid leukemia].

Objective: To analyze and compare therapy responses, outcomes, and incidence of severe hematologic adverse events of flumatinib and imatinib in patients newly diagnosed with chronic phase chronic myeloid leukemia (CML) . Methods: Data of patients with chronic phase CML diagnosed between January 2006 and November 2022 from 76 centers, aged ≥18 years, and received initial flumatinib or imatinib therapy within 6 months after diagnosis in China were retrospectively interrogated. Propensity score matching (PSM) analysis was performed to reduce the bias of the initial TKI selection, and the therapy responses and outcomes of patients receiving initial flumatinib or imatinib therapy were compared. Results: A total of 4 833 adult patients with CML receiving initial imatinib (n=4 380) or flumatinib (n=453) therapy were included in the study. In the imatinib cohort, the median follow-up time was 54 [interquartile range (IQR), 31-85] months, and the 7-year cumulative incidences of CCyR, MMR, MR(4), and MR(4.5) were 95.2%, 88.4%, 78.3%, and 63.0%, respectively. The 7-year FFS, PFS, and OS rates were 71.8%, 93.0%, and 96.9%, respectively. With the median follow-up of 18 (IQR, 13-25) months in the flumatinib cohort, the 2-year cumulative incidences of CCyR, MMR, MR(4), and MR(4.5) were 95.4%, 86.5%, 58.4%, and 46.6%, respectively. The 2-year FFS, PFS, and OS rates were 80.1%, 95.0%, and 99.5%, respectively. The PSM analysis indicated that patients receiving initial flumatinib therapy had significantly higher cumulative incidences of CCyR, MMR, MR(4), and MR(4.5) and higher probabilities of FFS than those receiving the initial imatinib therapy (all P<0.001), whereas the PFS (P=0.230) and OS (P=0.268) were comparable between the two cohorts. The incidence of severe hematologic adverse events (grade≥Ⅲ) was comparable in the two cohorts. Conclusion: Patients receiving initial flumatinib therapy had higher cumulative incidences of therapy responses and higher probability of FFS than those receiving initial imatinib therapy, whereas the incidence of severe hematologic adverse events was comparable between the two cohorts.

Long-term Results of Imatinib Discontinuation in Patients with Chronic-phase Chronic Myeloid Leukemia: A National Multicenter Prospective Study

Objective: The discovery of imatinib was a milestone for chronic myeloid leukemia (CML). As the life expectancy of CML patients has approached that of the general population, research has shifted towards improving quality of life and economic considerations. After 2010, it was shown that some patients could maintain molecular response even after discontinuing imatinib. This national multicenter prospective cohort study aimed to observe the long-term consequences of discontinuing imatinib therapy in adult chronic-phase CML patients. Materials and Methods: We enrolled 41 CML patients from 4 different centers in this non-randomized single-arm trial. Molecular responses of all patients were re-evaluated using real-time polymerase chain reaction at a single center. The median follow-up time after imatinib discontinuation was 48 months (minimum-maximum: 6-81 months). Results: The rate of molecular relapse-free survival at 48 months was 33.2% (confidence interval: 48.2-18.2). Twenty-seven of 41 patients lost their major molecular response, treatment was started again, and deep molecular response was re-achieved with imatinib in all cases. There was no significant relationship between molecular relapse and clinical factors such as duration of treatment or molecular response status. Discontinuing imatinib resulted in savings of approximately 4,392,000 Turkish lira or 245,150 US dollars. Conclusion: Tyrosine kinase inhibitor discontinuation with close molecular monitoring is a safe option and provides important national economic benefits for chronic phase CML patients. This approach should be considered for all eligible patients. This is the first tyrosine kinase inhibitor discontinuation study from Türkiye.

Validation of imatinib therapy failure score (IMTF) in chronic phase chronic myeloid leukemia in real life practice.

The outcome of chronic myeloid leukemia (CML) patients improved in the last decade. Clinical prognostic scoring systems aim to provide information about survival in the long-term, without determining from baseline the subset of patients who require a strictly monitoring because at increased risk of failure. Imatinib, the first-generation tyrosine kinase inhibitor (TKI), is still widely used as frontline treatment: recently, the imatinib therapy failure (IMTF) score was proposed to identify the failure free survival. Aim of our study was to validate this index in a large cohort of patients treated with imatinib.

Acquired miR-142 deficit in leukemic stem cells suffices to drive chronic myeloid leukemia into blast crisis.

The mechanisms underlying the transformation of chronic myeloid leukemia (CML) from chronic phase (CP) to blast crisis (BC) are not fully elucidated. Here, we show lower levels of miR-142 in CD34+CD38- blasts from BC CML patients than in those from CP CML patients, suggesting that miR-142 deficit is implicated in BC evolution. Thus, we create miR-142 knockout CML (i.e., miR-142-/-BCR-ABL) mice, which develop BC and die sooner than miR-142 wt CML (i.e., miR-142+/+BCR-ABL) mice, which instead remain in CP CML. Leukemic stem cells (LSCs) from miR-142-/-BCR-ABL mice recapitulate the BC phenotype in congenic recipients, supporting LSC transformation by miR-142 deficit. State-transition and mutual information analyses of "bulk" and single cell RNA-seq data, metabolomic profiling and functional metabolic assays identify enhanced fatty acid ß-oxidation, oxidative phosphorylation and mitochondrial fusion in LSCs as key steps in miR-142-driven BC evolution. A synthetic CpG-miR-142 mimic oligodeoxynucleotide rescues the BC phenotype in miR-142-/-BCR-ABL mice and patient-derived xenografts.

Population modeling of bosutinib exposure-response in patients with newly diagnosed chronic phase chronic myeloid leukemia.

BACKGROUND: The BELA and BFORE trials compared bosutinib starting doses of 500 mg once daily (QD) and 400 mg QD, respectively, with imatinib in adults with newly diagnosed chronic phase chronic myeloid leukemia (CP-CML). The B1871048 trial evaluated bosutinib 400 mg QD in Japanese patients with newly diagnosed CP-CML. AIM: This analysis assessed the impact of a lower bosutinib starting dose on key efficacy and safety outcomes. MATERIALS & METHODS: A pharmacokinetic model was used to estimate metrics of bosutinib exposure, and logistic regression was used to investigate relationships with efficacy (cumulative major molecular response [MMR] and cumulative complete cytogenetic response [CCyR]) and safety outcomes (eight prespecified adverse events). RESULTS: Totals of 573 and 574 patients were included in the efficacy and safety endpoint analyses, respectively. Cumulative MMR and CCyR were similar across studies. Log(Ctrough ) and log(Cavg ) were significant predictors of MMR and CCyR, and the probability of achieving MMR or CCyR increased 1.3-fold or 2.7-fold for every 1 unit increase in log(Ctrough ) or log(Cavg ), respectively. An exposure-response relationship was identified between time-to-event and risk of diarrhea, nausea, and vomiting. Significant relationships were also observed between time-to-event and log(Cavg ), Ctrough , and Cavg with diarrhea, nausea, and vomiting, respectively. DISCUSSION: A bosutinib exposure-response relationship with safety and efficacy was observed. CONCLUSION: Compared with 500 mg QD, a bosutinib starting dose of 400 mg QD improved tolerability in some patients with newly diagnosed CP-CML without compromising efficacy. CLINICALTRIALS: gov identifiers: NCT00574873; NCT02130557; NCT03128411.

Step-in dosing of bosutinib in pts with chronic phase chronic myeloid leukemia (CML) after second-generation tyrosine kinase inhibitor (TKI) therapy: results of the Bosutinib Dose Optimization (BODO) Study.

The approved dose of bosutinib in chronic phase CML is 400 mg QD in first-line and 500 mg QD in later-line treatment. However, given that gastrointestinal (GI) toxicity typically occurs early after treatment initiation, physicians often tend to start therapy with lower doses although this has never been tested systematically in prospective trials in the Western world. The Bosutinib Dose Optimization (BODO) Study, a multicenter phase II study, investigated the tolerability and efficacy of a step-in dosing concept of bosutinib (starting at 300 mg QD) in chronic phase CML patients in 2nd or 3rd line who were intolerant and/or refractory to previous TKI treatment. Of 57 patients included until premature closure of the study due to slow recruitment, 34 (60%) reached the targeted dose level of 500 mg QD following the 2-weekly step-in dosing regimen. While the dosing-in concept failed to reduce GI toxicity (grade II-IV, primary study endpoint) to < 40% (overall rate of 60%; 95% CI: 45-74%), bosutinib treatment (mean dosage: 403 mg/day) showed remarkable efficacy with a cumulative major molecular remission (MMR) rate of 79% (95% CI: 66 to 88%) at month 24. Of thirty patients refractory to previous therapy and not in MMR at baseline, 19 (64%) achieved an MMR during treatment. GI toxicity did not significantly impact on patient-reported outcomes (PRO) and led to treatment discontinuation in only one patient. Overall, the results of our trial support the efficacy and safety of bosutinib after failure of second-generation TKI pre-treatment. Trial registration: NCT02577926.