Current evidence on the efficacy and safety of generic imatinib in CML and the impact of generics on health care costs

A safety review of tyrosine kinase inhibitors for chronic myeloid leukemia

INTRODUCTION

Since the introduction of first tyrosine kinase inhibitor (TKI) imatinib, the treatment of chronic myeloid leukemia (CML) has reached excellent survival expectancies. Long survival rates bring about issues regarding TKI safety.

AREAS COVERED

The aim of this review is to compare the side effects of current TKIs both in the first and later lines and outline a safety andprofile of CML treatment. Seminal studies on TKIs and other newer drugs and extended follow-up of these studies; real-life data of each drug were usedduring the course of this. PubMed was used as a search database and onlyarticles in English were included.

EXPERT OPINION

With longer follow-up CML patients, resistant slowgrade adverse events seem to be the major obstacle in the way of treatmentefficacy. If efficacy is the priority, vigorous treatment of side effect and administration of full dose TKI are reasonable. But when treatment goals are reached, dose modifications or alternative treatment regimens may be acceptedpossible. More studies are needed on dose modification protocols and potential benefits and safety of treatment-free remission.

Therapeutic drug monitoring of imatinib - how far are we in the leukemia setting?

INTRODUCTION

Tyrosine kinase inhibitors (TKIs) have revolutionized survival rates of chronic myeloid leukemia (CML) and Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL) and replaced hematopoietic stem cell transplantation (hSCT) as the key treatment option for these patients. More recently, the so-called Philadelphia chromosome-like (Ph-like) ALL has similarly benefitted from TKIs. However, many patients shift from the first generation TKI, imatinib, due to treatment-related toxicities or lack of treatment efficacy. A more personalized approach to TKI treatment could counteract these challenges and potentially be more cost-effective. Therapeutic drug monitoring (TDM) has led to higher response rates and less treatment-related toxicity in adult CML but is rarely used in ALL or in childhood CML.

AREAS COVERED

This review summarizes different antileukemic treatment indications for TKIs with focus on imatinib and its pharmacokinetic/-dynamic properties as well as opportunities and pitfalls of TDM for imatinib treatment in relation to pharmacogenetics and co-medication for pediatric and adult Ph+/Ph-like leukemias.

EXPERT OPINION

TDM of imatinib adds value to standard monitoring of ABL-class leukemia by uncovering non-adherence and potentially mitigating adverse effects. Clinically implementable pharmacokinetic/-dynamic models adjusted for relevant pharmacogenetics could improve individual dosing. Prospective trials of TDM-based treatments, including both children and adults, are needed.

Identification by molecular dynamic simulation and in vitro validation of SISB-A1, N-[1-(4-bromophenyl)-3-methyl-1H-pyrazol-5-yl]-2-[(2-oxo-4-phenyl-2H-chromen-7-yl) oxy], as an inhibitor of the AblT315I mutant kinase to combat imatinib resistance in chronic myeloid leukemia

The discovery of imatinib, a specific inhibitor of Abl kinase, revolutionized the therapeutic approach to chronic myeloid leukemia (CML); however, its efficacy can be impeded by the emergence of novel mutations within the kinase domain, particularly AblT315I, that lead to the development of drug resistance. It therefore remains necessary to identify specific inhibitors that can effectively target imatinib-resistant CML harboring the AblT315I mutation. A natural product library sourced from the ZINC database was screened against the experimental structure of AblT315I kinase to identify compounds that selectively target the mutated kinase. The top-scoring compound was empirically tested for inhibition of AblT315I kinase using a luminescence-based kit and for impact on cellular proliferation using the BaF3-BCR-ABL-T315I stable cell line. Computational docking and molecular dynamic simulations identified the compound SISB-A1, N-[1-(4-bromophenyl)-3-methyl-1H-pyrazol-5-yl]-2-[(2-oxo-4-phenyl-2H-chromen-7-yl)oxy] acetamide, to effectively bind the catalytic domain of the mutant AblT315I kinase. Moreover, SISB-A1 exhibited greater preference than imatinib for amino acid residues of the mutant kinase's active site, including isoleucine 315. MMPBSA-based Gibbs binding free energy estimation predicted SISB-A1 to have a free energy of -51.5 versus -65.0 kcal/mol for the conventional AblT315I inhibitor ponatinib. Cell proliferation assays showed SISB-A1 to have a GI50 of 164.0 nM against the ABL-T315I stable cell line, whereas imatinib had a GI50 of 5035 nM. The IC50 value obtained for SISB-A1 against the AblT315I kinase was 197.9 nM. The results indicate SISB-A1 to have a notable ability to bind the catalytic domain of the AblT315I mutant kinase and effectively suppress its activity, thereby surpassing the associated resistance to imatinib. Continued advancement of this lead compound has the potential to yield innovative therapeutics for imatinib-resistant CML.

Determinants of frontline tyrosine kinase inhibitor choice for patients with chronic-phase chronic myeloid leukemia: A study from the Registro Italiano LMC and Campus CML

BACKGROUND

Imatinib, dasatinib, and nilotinib are tyrosine kinase inhibitors (TKIs) approved in Italy for frontline treatment of chronic-phase chronic myeloid leukemia (CP-CML). The choice of TKI is based on a combined evaluation of the patient's and the disease characteristics. The aim of this study was to analyze the use of frontline TKI therapy in an unselected cohort of Italian patients with CP-CML to correlate the choice with the patient's features.

METHODS

A total of 1967 patients with CP-CML diagnosed between 2012 and 2019 at 36 centers throughout Italy were retrospectively evaluated; 1089 patients (55.4%) received imatinib and 878 patients (44.6%) received a second-generation (2G) TKI.

RESULTS

Second-generation TKIs were chosen for most patients aged <45 years (69.2%), whereas imatinib was used in 76.7% of patients aged >65 years (p < .001). There was a predominant use of imatinib in intermediate/high European long-term survival risk patients (60.0%/66.0% vs. 49.7% in low-risk patients) and a limited use of 2G-TKIs in patients with comorbidities such as hypertension, diabetes, chronic obstructive pulmonary disease, previous neoplasms, ischemic heart disease, or stroke and in those with >3 concomitant drugs. We observed a greater use of imatinib (61.1%) in patients diagnosed in 2018-2019 compared to 2012-2017 (53.2%; p = .002). In multivariable analysis, factors correlated with imatinib use were age > 65 years, spleen size, the presence of comorbidities, and ≥3 concomitant medications.

CONCLUSIONS

This observational study of almost 2000 cases of CML shows that imatinib is the frontline drug of choice in 55% of Italian patients with CP-CML, with 2G-TKIs prevalently used in younger patients and in those with no concomitant clinical conditions. Introduction of the generic formulation in 2018 seems to have fostered imatinib use.

Fine-tuning of frontline tyrosine kinase inhibitor (TKI) therapy in chronic-phase chronic myeloid leukemia: The choice of the right TKI for the right patient

In an era when tyrosine kinase inhibitors are gaining acceptance in the treatment scene of chronic‐phase chronic myeloid leukemia, this editorial focuses on the search for the optimal patient‐based frontline treatment option while evaluating a recent study by Tiribelli and colleagues, which is published in this issue of Cancer.

The Economic Burden of Chronic Myeloid Leukemia in Patients with Later Lines: Findings from a Real-World Analysis in Italy

INTRODUCTION

Chronic myeloid leukemia (CML) is a hematopoietic myeloproliferative disorder that accounts for 20% of all leukemias of adults. The introduction of tyrosine kinase inhibitors (TKIs) (imatinib, bosutinib, dasatinib, nilotinib, ponatinib) has yielded significant benefits for patients with CML in terms of survival and quality of life. This real-world analysis evaluated the economic burden for managing patients with CML in 2nd or ≥ 3rd TKI lines in Italian settings of clinical practice.

METHODS

A retrospective observational analysis was performed exploiting the administrative databases of a sample of entities covering around 15 million inhabitants. From 2015 to 2018, the study included adult patients with at least one prescription for TKIs, (and for some TKI with at least one hospitalization discharge diagnosis for CML, or at least one prescription for BCR-ABL examination). The index date was the first TKI prescription. Healthcare resource consumption and costs for patients with CML in 2nd and ≥ 3rd line treatment with TKIs were analyzed for drug prescriptions, hospitalizations, specialist visits, and diagnostic services.

RESULTS

In total 635 patients were included, 491 in 2nd line and 144 in 3rd line with TKIs. Dasatinib was the most frequently prescribed drug in 2nd line (28.9%) and imatinib in later lines (26.4%). With progressing lines of treatment, healthcare consumption showed a trend towards increased non-TKI prescriptions per patient (8 for 2nd line and 9.7 for ≥ 3rd line). The management of patients with CML in later lines resulted in increased overall healthcare burden, with hospitalizations accounting for about half of total expenditure, whatever the treatment line and type of TKI.

CONCLUSIONS

This analysis in Italian real-life clinical practice reported economic expenditure for patients with CML in 2nd or ≥ 3rd lines with TKIs, mostly burdened by hospitalizations. Such clinical complexity suggests that further efforts are needed to improve the therapeutic management of later lines of CML.

Guidelines for the treatment of chronic myeloid leukemia from the NCCN and ELN: differences and similarities

Patients diagnosed with chronic myeloid leukemia (CML) in chronic phase can now have a life expectancy comparable to that of the general population thanks to the use of tyrosine kinase inhibitor (TKI) therapies. Although most patients with CML require lifelong TKI therapy, it is possible for some patients to achieve treatment-free remission. These spectacular results have been made possible by the development of superior treatment modalities as well as clinicians' efforts in strictly adhering to clinical guidelines such as the National Comprehensive Cancer Network (NCCN) and European Leukemia Network (ELN). CML treatment recommendations reported in these guidelines are the result of years of selecting and incorporating the most reliable evidence. In this review, we provide a synopsis of the differences and similarities that exist between the NCCN and ELN guidelines.

De-escalation or discontinuation of tyrosine kinase inhibitor in patients with chronic myeloid leukemia: A multicentral, open-label, prospective trial in China

Background: Long-term treatment-free remission (TFR) represents a new goal for chronic myeloid leukemia (CML). Optimizing dose of tyrosine kinase inhibitors (TKIs) in the CML treatment maybe a new challenge to maintain effective and improving patients' quality of life. We hypothesized that administration of low-dose TKIs does not compromise major molecular response (MMR) in patients with CML who have a deep molecular response (DMR). Methods: We did an open-label, randomized trial at eight hospitals in China. Eligible CML-CP patients (aged 18-70 years) had shown continuous response to TKI more than 5 years and maintained MR4.5 (BCR-ABLIS ≤ 0.0032%) in recent 18 months. Patients were randomly assigned (1:1) to the TKI de-escalation group or the discontinuation group. Randomization was done with permuted blocks (block size four) and implemented through an interactive web-based randomization system. Recurrence was defined as the single sample with real time Quantitative PCR (RT-qPCR) measurement greater than 0.1% (MMR). The primary endpoint was 12-month MMR rate in patients who received de-escalation or discontinuation of TKIs. This study was registered at ClinicalTrials.gov (NCT04143087). Results: Around 125 patients were enrolled between October 23, 2019 and October 31, 2020, 62 patients received dose de-escalation of TKIs, while 63 patients in the discontinuation group. In the de-escalation group, molecular recurrence-free survival at 12 months was 88.32% (95% CI 79%-98%), whereas molecular recurrence-free survival in the discontinuation group at 12 months was 59.98% (95% CI 47-73). No progressions occurred at the data cut-off date. All 29 recurrence cases restart TKI treatment returned to MMR. Cytolytic NK cells as a proportion of lymphocyte cells were significantly increased from baseline after 6 months whether in the de-escalation or TKIs cessation group (P = 0.048, 0.001, respectively); compared with the relapsing patients, Tregs proportion was decreased (P = 0.003), and higher proportion of NK cells were found in non-relapsing patients whether in TKI de-escalation or discontinuation group (P = 0.011, 0.007, respectively). We also found that the de-escalation group showed better disease-specific HRQOL in regards to its impact on emotional functioning, fatigue, pain, and financial difficulties. Conclusion: With 88.32% MMR in 12-months follow-up after de-escalation TKIs' treatment, dose-halving could become a new treatment paradigm for CML patients who with DMR under continuing maintenance therapy with TKIs.

A predictive scoring system for therapy-failure in persons with chronic myeloid leukemia receiving initial imatinib therapy

Data from 1,364 consecutive subjects with chronic-phase chronic myeloid leukemia (CML) receiving initial imatinib-therapy were interrogated to identify co-variates predicting therapy failure. Subjects were randomly divided into training (n = 908) and validation datasets (n = 456). In the training dataset, WBC count ≥120 × 10E + 9/L, haemoglobin concentration <115 g/L, blood basophils ≥12% and European Treatment and Outcome Study for CML Long-Term Survival (ELTS) risk score were significantly-associated with failure-free survival (FFS). Each co-variate was assigned 1 point to develop the imatinib-therapy failure (IMTF) model except ELTS high-risk category which was assigned 2 points based on multi-variable regression coefficients. Area under receiver-operator characteristic curve values in the IMTF model for 1-, 3- and 5-year FFS were 0.79-0.84 in the training dataset and 0.78-0.85 in the validation dataset. Calibration plots showed high agreement between predicted and observed outcomes. Decision curve analyses indicated subjects benefited from clinical use of this model. Cumulative incidences of imatinib-therapy failure and probabilities of FFS among the 5 risk cohorts (very low-, low-, intermediate-, high- and very high-risk) using the IMTF model were significantly different (all p values < 0.001). The IMTF model also correlated with probabilities of progression-free survival and survival (all p values < 0.001). These data should help physicians optimize TKI-therapy strategy at diagnosis in persons with chronic phase CML.