Hepatotoxicity as dose-limiting toxicity of the combination of bosutinib and atezolizumab in patients with chronic myeloid leukemia. Results of the ZEROLMC study.

In the field of chronic myeloid leukemia (CML), new strategies are needed to increase the rate of successful treatment discontinuations, a crucial goal in this disease. Anti-PD-L1 checkpoint inhibitors are a promising therapeutic approach in CML after the demonstration of an increase of these inhibitory molecules in patients with CML. A phase Ib/II (NCT04793399, registration date March 11, 2021) open-label exploratory trial has been conducted to evaluate the safety of atezolizumab, a humanized anti-PD-L1 antibody, in combination with bosutinib in patients with newly diagnosed chronic phase CML. A total of 36 patients were planned to be enrolled, but the study had to be prematurely terminated due to safety concerns. Nine patients were included in the study, and only 8 went on to receive the combination with atezolizumab. There were a total of 44 adverse events (AEs) during the study period. The most frequent were gastrointestinal (50%), mostly mild (86% grade 1-2). The most serious AEs were hepatic. There were 17 hepatic AEs in 5 patients. Of the hepatic AEs 5 were during the bosutinib monotherapy phase and 12 during the combination phase (AST increase x4, ALT increase x4, blood bilirubin increase x1, alkaline phosphatase elevation x2, GGT increase x2), most of them grade 3-4. There were 2 patients who presented a dose-limiting toxicity; a grade 3 elevation of transaminases, that led to premature termination of the study. The combination of atezolizumab with bosutinib presents hepatotoxicity as a dose-limiting effect and therefore we do not recommend to explore this combination in future studies.

The prognostic impact of non-driver gene mutations and variant allele frequency in primary myelofibrosis.

Prognostic impact of non-MPN driver gene mutations in primary myelofibrosis. MIPSS70: Mutation-Enhanced International Prognostic Score System.

Biomarkers of Response to Venetoclax Therapy in Acute Myeloid Leukemia.

Recent progress in the use of massive sequencing technologies has greatly enhanced our understanding of acute myeloid leukemia (AML) pathology. This knowledge has in turn driven the development of targeted therapies, such as venetoclax, a BCL-2 inhibitor approved for use in combination with azacitidine, decitabine, or low-dose cytarabine for the treatment of newly diagnosed adult patients with AML who are not eligible for intensive chemotherapy. However, a significant number of AML patients still face the challenge of disease relapse. In this review, we will explore biomarkers that may predict disease progression in patients receiving venetoclax-based therapy, considering both clinical factors and genetic changes. Despite the many advances, we conclude that the identification of molecular profiles for AML patients who will respond optimally to venetoclax therapy remains an unmet clinical need.

Treatment-free remission after dasatinib in patients with chronic myeloid leukaemia in chronic phase with deep molecular response: Final 5-year analysis of DASFREE.

Patients with chronic myeloid leukaemia in chronic phase (CML-CP) who have a sustained deep molecular response (DMR) are eligible to discontinue treatment and attempt treatment-free remission (TFR). In the DASFREE study (ClinicalTrials.gov; NCT01850004), the 2-year TFR rate after dasatinib discontinuation was 46%; here we present the 5-year update. Patients with a stable DMR after ≥2 years of dasatinib therapy discontinued treatment and were followed for 5 years. At a minimum follow-up of 60 months, in 84 patients discontinuing dasatinib, the 5-year TFR rate was 44% (n = 37). No relapses occurred after month 39 and all evaluable patients who relapsed and restarted dasatinib (n = 46) regained a major molecular response in a median of 1.9 months. The most common adverse event during the off-treatment period was arthralgia (18%, 15/84); a total of 15 withdrawal events were reported in nine patients (11%). At the 5-year final follow-up, almost half of the patients who discontinued dasatinib after a sustained DMR maintained TFR. All evaluable patients who experienced a relapse quickly regained a DMR after restarting dasatinib, demonstrating that dasatinib discontinuation is a viable and potentially long-term option in patients with CML-CP. The safety profile is consistent with the previous report.

Molecular Studies for the Early Detection of Philadelphia-Negative Myeloproliferative Neoplasms.

JAK2 V617F is the predominant driver mutation in patients with Philadelphia-negative myeloproliferative neoplasms (MPN). JAK2 mutations are also frequent in clonal hematopoiesis of indeterminate potential (CHIP) in otherwise "healthy" individuals. However, the period between mutation acquisition and MPN diagnosis (known as latency) varies widely between individuals, with JAK2 mutations detectable several decades before diagnosis and even from birth in some individuals. Here, we will review the current evidence on the biological factors, such as additional mutations and chronic inflammation, which influence clonal expansion and may determine why some JAK2-mutated individuals will progress to an overt neoplasm during their lifetime while others will not. We will also introduce several germline variants that predispose individuals to CHIP (as well as MPN) identified from genome-wide association studies. Finally, we will explore possible mutation screening or interventions that could help to minimize MPN-associated cardiovascular complications or even delay malignant progression.

Real-world analysis of main clinical outcomes in patients with polycythemia vera treated with ruxolitinib or best available therapy after developing resistance/intolerance to hydroxyurea.

BACKGROUND: Ruxolitinib is approved for patients with polycythemia vera (PV) who are resistant/intolerant to hydroxyurea, but its impact on preventing thrombosis or disease-progression is unknown. METHODS: A retrospective, real-world analysis was performed on the outcomes of 377 patients with resistance/intolerance to hydroxyurea from the Spanish Registry of Polycythemia Vera according to subsequent treatment with ruxolitinib (n = 105) or the best available therapy (BAT; n = 272). Survival probabilities and rates of thrombosis, hemorrhage, acute myeloid leukemia, myelofibrosis, and second primary cancers were calculated according to treatment. To minimize biases in treatment allocation, all results were adjusted by a propensity score for receiving ruxolitinib or BAT. RESULTS: Patients receiving ruxolitinib had a significantly lower rate of arterial thrombosis than those on BAT (0.4% vs 2.3% per year; P = .03), and this persisted as a trend after adjustment for the propensity to have received the drug (incidence rate ratio, 0.18; 95% confidence interval, 0.02-1.3; P = .09). There were no significant differences in the rates of venous thrombosis (0.8% and 1.1% for ruxolitinib and BAT, respectively; P = .7) and major bleeding (0.8% and 0.9%, respectively; P = .9). Ruxolitinib exposure was not associated with a higher rate of second primary cancers, including all types of neoplasia, noncutaneous cancers, and nonmelanoma skin cancers. After a median follow-up of 3.5 years, there were no differences in survival or progression to acute leukemia or myelofibrosis between the 2 groups. CONCLUSIONS: The results suggest that ruxolitinib treatment for PV patients with resistance/intolerance to hydroxyurea may reduce the incidence of arterial thrombosis. LAY SUMMARY: Ruxolitinib is better than other available therapies in achieving hematocrit control and symptom relief in patients with polycythemia vera who are resistant/intolerant to hydroxyurea, but we still do not know whether ruxolitinib provides an additional benefit in preventing thrombosis or disease progression. We retrospectively studied the outcomes of 377 patients with resistance/intolerance to hydroxyurea from the Spanish Registry of Polycythemia Vera according to whether they subsequently received ruxolitinib (n = 105) or the best available therapy (n = 272). Our findings suggest that ruxolitinib could reduce the incidence of arterial thrombosis, but a disease-modifying effect could not be demonstrated for ruxolitinib in this patient population.

Validation of thrombotic risk factors in 1381 patients with essential thrombocythaemia: A multicentre retrospective real-life study.

Thrombosis and haemorrhage are frequent in patients with essential thrombocythaemia (ET). The 2016 revised International Prognostic Score for Thrombosis in Essential Thrombocythaemia-thrombosis (r-IPSET-t) score stratifies patients into very-low- (VLR), low- (LR), intermediate- (IR) and high-risk (HR) groups. We validated the r-IPSET-t in the biggest population of patients with ET (n = 1381) to date and found it to be a better fit than the earlier IPSET-t score. With an average follow-up of 87.7 months, there were 0.578 thrombotic events/person-year and 0.286 bleeding events/person-year after diagnosis. The 10-year thrombosis-free survival was 88% and 99% for the r-IPSET-t LR and VLR groups (p < 0.001). Cytoreduction was a thrombotic risk factor in younger patients (aged <60 years, hazard ratio 9.49, p = 0.026; aged ≥60 years, hazard ratio 1.04, p = 0.93). In multivariable Cox regression analysis, anti-aggregation after diagnosis was protective for thrombosis (hazard ratio 0.31, p = 0.005) but a risk factor for major bleeding (hazard ratio 10.56, p = 0.021). Of the IPSET-t HR and LR groups, 132/780 and 249/301 were re-classified as LR and VLR respectively (p < 0.001). The European LeukemiaNET (ELN) does not recommend aspirin for VLR patients but in this real-life analysis 83.1% of VLR patients received it. Our results validate the r-IPSET-t score as more predictive for thrombosis than the ELN-recommended IPSET-t and raise concerns about unnecessary cytoreductive and anti-aggregative therapy.

Predictors of thrombosis and bleeding in 1613 myelofibrosis patients from the Spanish Registry of Myelofibrosis.

Available data have proved insufficient to develop consensus recommendations on the prevention of thrombosis and bleeding in myelofibrosis (MF). We evaluated the incidence and risk factors of vascular complications in 1613 patients from the Spanish Myelofibrosis Registry. Over a total of 6981 patient-years at risk, 6.4% of the study population had at least one thrombotic event after MF diagnosis, amounting to an incidence rate of 1.65 per 100 patient-years. Prior history of thrombosis, the JAK2 mutation, and the intermediate-2/high-risk International Prognostic Scoring System (IPSS) categories conferred an increased thrombotic risk after adjustment for the risk-modifying effect of anti-thrombotic and cytoreductive treatments. History of thrombosis and the JAK2 mutation allowed us to pinpoint a group of patients at higher risk of early thrombosis. No decreased incidence of thrombosis was observed while patients were on anti-thrombotic or cytoreductive treatment. An increased risk of venous thrombosis was found during treatment with immunomodulatory agents. A total of 5.3% of patients had at least one episode of major bleeding, resulting in an incidence rate of 1.5 events per 100 patient-years. Patients in the intermediate-2/high-risk IPSS categories treated with anti-coagulants had an almost sevenfold increased risk of major bleeding. These findings should prove useful for guiding decision-making in clinical practice.

Low-risk polycythemia vera treated with phlebotomies: clinical characteristics, hematologic control and complications in 453 patients from the Spanish Registry of Polycythemia Vera.

Hematological control, incidence of complications, and need for cytoreduction were studied in 453 patients with low-risk polycythemia vera (PV) treated with phlebotomies alone. Median hematocrit value decreased from 54% at diagnosis to 45% at 12 months, and adequate hematocrit control over time (< 45%) was observed in 36%, 44%, and 32% of the patients at 6, 12, and 24 months, respectively. More than 5 phlebotomies per year in the maintenance phase were required in 19% of patients. Worsening thrombocytosis, age > 60 years, and microvascular symptoms constituted the main indications for starting cytoreduction. Median duration without initiating cytoreduction was significantly longer in patients younger than 50 years (< 0.0001). The incidence rate of thrombosis under phlebotomies alone was 0.8% per year and the estimated probability of thrombosis at 10 years was 8.5%. The probability of arterial thrombosis was significantly higher in patients with arterial hypertension whereas there was a trend to higher risk of venous thrombosis in cases with high JAK2V617F allele burden. Rates of major bleeding and second primary neoplasm were low. With a median follow-up of 9 years, survival probability at 10 years was 97%, whereas the probability of myelofibrosis at 10 and 20 years was 7% and 20%, respectively. Progression to acute myeloid leukemia was documented in 3 cases (1%). Current management of low-risk PV patients is associated with low rate of thrombosis and long survival. New treatment strategies are needed for improving hematological control and, in the long term, reducing progression to myelofibrosis.

Discontinuation of Tyrosine Kinase Inhibitors in Patients with Chronic Myeloid Leukemia: a Review of the Biological Factors Associated with Treatment-Free Remission.

PURPOSE OF REVIEW: Clinical factors alone do not enable us to differentiate which patients will maintain treatment-free remission (TFR) from those who are likely to relapse. Thus, patient-specific factors must also play a role. This review will update the reader on the most recent studies presenting biological factors that can help predict tyrosine kinase inhibitor (TKI) discontinuation success. RECENT FINDINGS: Cellular and molecular factors with a suggested role in TFR include immune factors and leukemic stem cell (LSC) persistence; the BCR::ABL1 transcript type, halving time, and BCR::ABL1 DNA and RNA positivity; as well as other molecular factors such as somatic mutations, RNA expression, and telomere length. Our review presents several biomarkers with predictive value for TFR but also highlights areas of unmet need. Future discontinuation guidelines will likely include biological factors for the personalization of TFR prediction. However, it will be important that such advances do not prevent more patients from making a TKI discontinuation attempt.

The risk of thrombosis in essential thrombocythemia is associated with the type of CALR mutation: A multicentre collaborative study.

OBJECTIVES: In patients with essential thrombocythemia (ET), after the JAK2V617F driver mutation, mutations in CALR are common (classified as type 1, 52-bp deletion or type 2, 5-bp insertion). CALR mutations have generally been associated with a lower risk of thrombosis. This study aimed to confirm the impact of CALR mutation type on thrombotic risk. METHODS: We retrospectively investigated 983 ET patients diagnosed in Spanish and Polish hospitals. RESULTS: With 7.5 years of median follow-up from diagnosis, 155 patients (15.8%) had one or more thrombotic event. The 5-year thrombosis-free survival (TFS) rate was 83.8%, 91.6% and 93.9% for the JAK2V617F, CALR-type 1 and CALR-type 2 groups, respectively (P = .002). Comparing CALR-type 1 and CALR-type 2 groups, TFS for venous thrombosis was lower in CALR-type 1 (P = .046), with no difference in TFS for arterial thrombosis observed. The cumulative incidence of thrombosis was significantly different comparing JAK2V617F vs CALR-type 2 groups but not JAK2V617F vs CALR-type 1 groups. Moreover, CALR-type 2 mutation was a statistically significant protective factor for thrombosis with respect to JAK2V617F in multivariate logistic regression (OR: 0.45, P = .04) adjusted by age. CONCLUSIONS: Our results suggest that CALR mutation type has prognostic value for the stratification of thrombotic risk in ET patients.

Recent Advances in the Use of Molecular Analyses to Inform the Diagnosis and Prognosis of Patients with Polycythaemia Vera.

Genetic studies in the past decade have improved our understanding of the molecular basis of the BCR-ABL1-negative myeloproliferative neoplasm (MPN) polycythaemia vera (PV). Such breakthroughs include the discovery of the JAK2V617F driver mutation in approximately 95% of patients with PV, as well as some very rare cases of familial hereditary MPN caused by inherited germline mutations. Patients with PV often progress to fibrosis or acute myeloid leukaemia, both associated with very poor clinical outcome. Moreover, thrombosis and major bleeding are the principal causes of morbidity and mortality. As a result of increasingly available and economical next-generation sequencing technologies, mutational studies have revealed the prognostic relevance of a few somatic mutations in terms of thrombotic risk and risk of transformation, helping to improve the risk stratification of patients with PV. Finally, knowledge of the molecular basis of PV has helped identify targets for directed therapy. The constitutive activation of the tyrosine kinase JAK2 is targeted by ruxolitinib, a JAK1/JAK2 tyrosine kinase inhibitor for PV patients who are resistant or intolerant to cytoreductive treatment with hydroxyurea. Other molecular mechanisms have also been revealed, and numerous agents are in various stages of development. Here, we will provide an update of the recent published literature on how molecular testing can improve the diagnosis and prognosis of patients with PV and present recent advances that may have prognostic value in the near future.

Prognostic risk models for transplant decision-making in myelofibrosis.

Prognostic models are widely used in clinical practice for transplant decision-making in myelofibrosis (MF). We have compared the performance of the International Prognostic Scoring System (IPSS), dynamic IPSS (DIPSS), and DIPSS-plus in a series of 544 patients with primary or secondary MF aged ≤ 70 years at the time of diagnosis. The median projected survival of the overall series was 9.46 years (95% confidence interval 7.44-10.59). Median survival for the highest risk groups was less than 4 years in the three prognostic models. By contrast, the projected survival for patients in the intermediate-2 categories by the IPSS, DIPSS, and DIPSS-plus was 6.6, 5.6, and 6.5 years, respectively. The number of patients in the intermediate-2 and high-risk categories was smaller in the DIPSS than in the IPSS or the DIPSS-plus. The IPSS and DIPSS-plus were the best models to discriminate between the intermediate-1 and intermediate-2 risk categories, which is a critical cut-off point for patient selection to transplant. Among patients assigned at diagnosis to the intermediate-2 or high-risk groups by the IPSS, DIPSS, and DIPSS-plus, only 17, 21, and 20%, respectively, were subsequently transplanted. In conclusion, in our contemporary series of younger MF patients only the highest risk categories of the current prognostication systems have a median survival below the 5-year threshold recommended for considering transplantation. Patient selection for transplantation can significantly differ depending on which prognostication model is used for disease risk stratification.

Drug-to-drug interactions of tyrosine kinase inhibitors in chronic myeloid leukemia patients. Is it a real problem?

With tyrosine kinase inhibitors (TKI), chronic myeloid leukemia (CML) patients are achieving similar rates of survival to the general population and some treatment aspects such as adherence and drug-to-drug interactions (DDI) are becoming increasingly important. Our aim was to investigate the frequency and real clinical consequences of DDI between TKI and concurrent medications in CML. We performed a retrospective multicenter study including 105 patients receiving 134 TKI treatments. Sixty-three patients (60%) had at least one potential DDI. The mean number of concomitant medications was 4.8 (0-19). The mean number of DDI by TKI treatment was 1.2 (0-8); it increased with the number of concomitant medications and age in a significant manner. A total of 159 DDI were detected, involving 55 different drugs. The most common drug classes involved were proton pump inhibitors, statins, and antidepressants. A DDI-related clinical effect (toxicity and/or lack of efficacy) was suspected during the common course of patient follow-up in only five patients (4.7%). This number increased to 20% when data were centrally reviewed. Most of the adverse events (AE) attributed to DDIs were mild. The most common were diarrhea, vomiting, edema, cramps, and transaminitis. Nilotinib and dasatinib showed a tendency towards a higher risk of DDI compared with imatinib. There were no significant differences in AE frequency or in treatment response between patients with or without DDI. Due to their frequency, and their potential to cause clinically relevant effects, DDI are an important aspect of CML management.

Risk of thrombosis according to need of phlebotomies in patients with polycythemia vera treated with hydroxyurea.

Hematocrit control below 45% is associated with a lower rate of thrombosis in polycythemia vera. In patients receiving hydroxyurea, this target can be achieved with hydroxyurea alone or with the combination of hydroxyurea plus phlebotomies. However, the clinical implications of phlebotomy requirement under hydroxyurea therapy are unknown. The aim of this study was to evaluate the need for additional phlebotomies during the first five years of hydroxyurea therapy in 533 patients with polycythemia vera. Patients requiring 3 or more phlebotomies per year (n=85, 16%) showed a worse hematocrit control than those requiring 2 or less phlebotomies per year (n=448, 84%). There were no significant differences between the two study groups regarding leukocyte and platelet counts. Patients requiring 3 or more phlebotomies per year received significantly higher doses of hydroxyurea than the remaining patients. A significant higher rate of thrombosis was found in patients treated with hydroxyurea plus 3 or more phlebotomies per year compared to hydroxyurea with 0-2 phlebotomies per year (20.5% vs. 5.3% at 3 years; P<0.0001). In multivariate analysis, independent risk factors for thrombosis were phlebotomy dependency (HR: 3.3, 95%CI: 1.5-6.9; P=0.002) and thrombosis at diagnosis (HR: 4.7, 95%CI: 2.3-9.8; P<0.0001). The proportion of patients fulfilling the European LeukemiaNet criteria of resistance/intolerance to hydroxyurea was significantly higher in the group requiring 3 or more phlebotomies per year (18.7% vs. 7.1%; P=0.001) mainly due to extrahematologic toxicity. In conclusion, phlebotomy requirement under hydroxyurea therapy identifies a subset of patients with increased proliferation of polycythemia vera and higher risk of thrombosis.

Antiplatelet therapy versus observation in low-risk essential thrombocythemia with a CALR mutation.

The role of antiplatelet therapy as primary prophylaxis of thrombosis in low-risk essential thrombocythemia has not been studied in randomized clinical trials. We assessed the benefit/risk of low-dose aspirin in 433 patients with low-risk essential thrombocythemia (271 with a CALR mutation, 162 with a JAK2(V617F) mutation) who were on antiplatelet therapy or observation only. After a follow up of 2215 person-years free from cytoreduction, 25 thrombotic and 17 bleeding episodes were recorded. In CALR-mutated patients, antiplatelet therapy did not affect the risk of thrombosis but was associated with a higher incidence of bleeding (12.9 versus 1.8 episodes per 1000 patient-years, P=0.03). In JAK2(V617F)-mutated patients, low-dose aspirin was associated with a reduced incidence of venous thrombosis with no effect on the risk of bleeding. Coexistence of JAK2(V617F)-mutation and cardiovascular risk factors increased the risk of thrombosis, even after adjusting for treatment with low-dose aspirin (incidence rate ratio: 9.8; 95% confidence interval: 2.3-42.3; P=0.02). Time free from cytoreduction was significantly shorter in CALR-mutated patients with essential thrombocythemia than in JAK2(V617F)-mutated ones (median time 5 years and 9.8 years, respectively; P=0.0002) and cytoreduction was usually necessary to control extreme thrombocytosis. In conclusion, in patients with low-risk, CALR-mutated essential thrombocythemia, low-dose aspirin does not reduce the risk of thrombosis and may increase the risk of bleeding.

Critical review of clinical data and expert-based recommendations for the use of bosutinib in the treatment of chronic myeloid leukemia.

Chronic myeloid leukemia (CML), characterized by the presence of the BCR::ABL1 fusion gene, has undergone a transformative shift with the introduction of tyrosine kinase inhibitors (TKIs). The current availability of six different TKIs (imatinib, dasatinib, nilotinib, bosutinib, ponatinib, and asciminib) in clinical practice makes it important to know their efficacy and toxicity profile for treatment optimization. This review examines the latest insights regarding the use of bosutinib in CML treatment. Clinical trials have demonstrated the effectiveness of bosutinib, positioning it as a first-line treatment that can induce sustained molecular responses. Importantly, it can also be effective in patients who have experienced treatment failure or intolerance with prior TKIs, revealing the potential of bosutinib also in second- and later-line settings. Even in the advanced phase of CML, bosutinib has demonstrated its capacity to achieve molecular responses, expanding its usefulness. Real-world evidence studies echo these findings, emphasizing bosutinib's effectiveness in achieving deep molecular responses, maintaining remissions, and serving as an alternative for patients intolerant or resistant to other TKIs as a second-line therapy. Notably, one of the greatest strengths of bosutinib is its favorable safety profile, in particular the low incidence of vascular complications with its use, which is undoubtedly a comparative advantage over other TKIs. In summary, the latest research highlights the versatility of bosutinib in CML treatment and underscores its pivotal role in optimizing patient management in challenging cases. Continuing research and investigation will further establish bosutinib's place in the evolving landscape of CML therapy, offering an alternative for CML patients across different treatment stages.