Incidence of Bcr-Abl kinase domain mutations in imatinib refractory chronic myeloid leukemia patients from South India

A Retrospective Analysis of BCR-ABL-1 Kinase Domain Mutations in Frontline TKI Resistant Chronic Myeloid Leukemia Patients: A Single Centre Experience

CML is a commonly diagnosed myeloproliferative neoplasm in India. Tyrosine kinase inhibitors (TKIs) are the current standard of care for management of CML. Mutations in Tyrosine kinase Domain (TKD) result in resistance to TKIs. The aim of this study is to evaluate the pattern of TKD mutations in CML patients having inadequate response or resistance to first line TKIs and to analyse the outcome of CML patients with and without mutations. It is a retrospective observational study. Medical records of 1633 CML patients from year 2014 to 2021 were analysed. Out of these 108 patients (6.6%) lost their response or did not achieve it in defined time points. 62 patients (71%) were found to have TKD mutations. On analysing specific mutations T315I was the most common mutation seen in 29 (46%) cases followed by M351T in 10 (16%) cases and G250E in 7 (11%) cases. ATP binding region was found to be the most common site in tyrosine kinase domain (50% cases) followed by P-loop (22%) and A loop (9.6%). 13 (20%) cases had ≥2 TKD mutations. The study showed inferior overall survival (OS) in patients with TKD mutations involving T315I mutations and ATP binding domain. Patients may have have underlying TKD mutations at prestation or may develop during course of disease. In case of TKI resistance, testing for specific mutations must be done and appropriate TKI sensitive to underlying mutation is to be used which translates into improved OS.

A Retrospective Analysis of BCR-ABL1 Kinase Domain Mutations in the Frontline Drug Intolerant or Resistant Chronic Myeloid Leukemia Patients: An Indian Experience from a High-End Referral Laboratory

Atreye MajumdarSambit K. MohantyObjective  This article identifies and evaluates the frequency of mutations in the BCR-ABL1 kinase domain (KD) of chronic myeloid leukemia (CML) patients who showed suboptimal response to their current tyrosine kinase inhibitor (TKI) regime and assesses their clinical value in further treatment decisions. Materials and Methods  Peripheral and/or bone marrow were collected from 791 CML patients. Ribonucleic acid was extracted, reverse transcribed, and Sanger sequencing method was utilized to detect single-nucleotide variants (SNVs) in BCR-ABL1 KD. Results  Thirty-eight different SNVs were identified in 29.8% ( n  = 236/791) patients. T315I, E255K, and M244V were among the most frequent mutations detected. In addition, one patient harbored a novel L298P mutation. A subset of patients from the abovementioned harbored compound mutations (13.3%, n  = 33/236). Follow-up data was available in 28 patients that demonstrated the efficacy of TKIs in correlation with mutation analysis and BCR-ABL1 quantitation. Molecular response was attained in 50% patients following an appropriate TKI shift. A dismal survival rate of 40% was observed in T315I-harboring patients on follow-up. Conclusion  This study shows the incidence and pattern of mutations in one of the largest sets of Indian CML patients. In addition, our findings strengthen the prognostic value of KD mutation analysis among strategies to overcome TKI resistance.

Assessment of BCR-ABL1 Fusion Transcripts and Their Association with Response to Imatinib Treatment in Chronic Myeloid Leukemia Patients

Objectives: BCR-ABL1 fusion transcripts with contrasting data on response to imatinib therapy have been reported from different parts of the world. Hence, the present study aimed to determine the frequencies of transcripts and their association with response to imatinib therapy in chronic myeloid leukemia (CML) patients. Methods: A total of 170 (76 follow-up and 94 imatinib-resistant) CML samples were included in the study. BCR-ABL1 fusion transcripts and expression status were analyzed in all cases using multiplex reverse transcriptase PCyR and real-time PCyR. Sanger sequencing was used for tyrosine kinase domain (TKD) mutation screening in imatinib mesylate-resistant patients. Results: Of 170 CML patients, 36.36% showed b2a2, 63.53% had b3a2, and 2.94% had b2a2 + b3a2 isoforms. Mean platelet counts and blasts were significantly lower in b2a2 carriers (P = 0.0092; P ≤ 0.0001). Patients with b2a2 transcript were found to be more in responders group (both hematological and cytogenetic), whereas b3a2 patients were more in partial responders group and death (P = 0.763; P = 0.309). In follow-up patients, mean baseline BCR-ABL1 expression levels are significantly higher in b2a2 versus b3a2 carriers (P = 0.0351). Of 94 imatinib-resistant patients, 36 (38.29%) had acquired TKD mutations. Among 36 patients, mean BCR-ABL1 levels are significantly higher in b2a2 and b2a2 + b3a2 group (P = 0.0002; P ≤ 0.0001). TKD mutation frequency was more in b3a2 (61.11%) compared to other types. With respect to follow-up status in 36 patients, 17 patients died while 19 were on imatinib higher doses or 2nd-generation tyrosine kinase inhibitors. Of 17 patients, 41.66% had b2a2 transcript and 54.54% had b3a2 transcript. Conclusion: Patients with b3a2 transcripts might be associated with poor response and worse prognosis in CML with imatinib treatment.

Efficacy, safety, and quality of life of generic and innovator ibrutinib in Indian CLL patients

To report the efficacy, safety, and quality of life (QoL) on generic and innovator ibrutinib in Indian CLL patients. This was a single centre, prospective study of treatment-naive (TN), and relapsed/refractory (R/R) CLL patients receiving ibrutinib in India. The choice of innovator or generic ibrutinib was as per patient discretion. Response and adverse events were recorded as per the 2018 iwCLL guidelines and CTCAEv4.0. QoL was assessed using the EORTC QLQ-C30 and CLL17 questionnaires. A total of 32 CLL patients (TN, n = 7 and R/R, n = 25) received ibrutinib from 2016-2019. The median age was 60 years (37-84). All TN patients attained partial response without any grade 3/4 adverse events (AE). Ibrutinib was less tolerated in the R/R setting, with 52% patients developing grade 3/4 AE and required dose reduction. Eleven patients (44%) died during follow-up. Grade 3-5 infections were seen in 44% of R/R CLL patients. Generic ibrutinib (n = 8) was comparable to innovator ibrutinib (n = 17) in terms of efficacy, safety, and QoL. Ibrutinib is less well tolerated in Indian R/R CLL patients. Infections are a common cause of morbidity and mortality. This study affirms the safety and efficacy of generic ibrutinib.

Efficacy and safety profile of generic imatinib in patients with newly diagnosed chronic myeloid leukemia-chronic phase: sharing experience of a hemato-oncology center from eastern India

In India, CML is the commonest adult leukemia. Imatinib is the gold standard for frontline treatment of newly diagnosed CML-CP patients. The present study was conducted to assess the efficacy and safety of generic imatinib in newly diagnosed CML-CP patients. In this prospective study, 76 newly diagnosed CML-CP patients received generic imatinib. They were monitored as per the ELN2013 recommendation. Karyotyping and BCR-ABL transcript level were done at specified time points. Adverse effects, if any, were documented as per the NCI-CTCAE criteria v4.03. Statistical analysis was done using standard methods. A total of 76 patients included in the study; median age was 36 years. The most common (71%) presenting symptom was fatigue; splenomegaly was found in all patients. CHR was achieved in 97% cases. At 3 months, 64.5% patients achieved ERM. At 6 months, CCyR and MCyR had seen in 65% and 68% cases, respectively. MMR achieved at 12 months in 44% cases. Most common hematological and non-hematological toxicity were anemia and skin changes seen in 89.5% and 71% cases, respectively. With generic imatinib therapy, the results of treatment outcome and safety profile were comparable with original imatinib. The added advantage was gross reduction in cost of therapy meeting unmet needs in CML patients in countries with resource constraints.

ABL Kinase Domain Mutations in Iranian Chronic Myeloid Leukemia Patients with Resistance to Tyrosine Kinase Inhibitors

OBJECTIVE

Tyrosine kinase inhibitors (TKIs) are considered standard first-line treatment in patients with chronic myeloid leukemia. Because ABL kinase domain mutations are the most common causes of treatment resistance, their prevalence and assessment during treatment may predict subsequent response to therapy.

METHODS

The molecular response in Bcr-Abl1IS was tested via quantitative real-time polymerase chain reaction. We used the direct sequencing technique to discover the mutations in the ABL kinase domain. The IRIS trial established a standard baseline for measurement - (100% BCR-ABL1 on the 'international scale') and a major molecular response (good response to therapy) was defined as a 3-log reduction in the amount of BCR-ABL1 - 0.1% BCR-ABL1 on the international scale.

RESULTS

We observed 11 different mutations in 13 patients, including E255K, which had the highest mutation rate. A lack of hematologic response was found in 22 patients, who showed a significantly higher incidence of mutations.

CONCLUSION

Detection of kinase domain mutations is a reliable method for choosing the best treatment strategy based on patients' conditions, avoiding ineffective treatments, and running high-cost protocols in patients with acquired resistance to TKIs.

An Imatinib-non-responsive patient with an ABL Leu387Trp mutation achieves cytogenetic and molecular response under bosutinib: Case report and biological characterization

Leu387Trp mutation, aroused in an imatinib-non-responsive CML patient, was selected by imatinib treatment along with other unknown factors responsible for resistance, and then it was overcome by bosutinib. These results will be useful for treating patients with this rare mutation and will advise against automatically considering a new mutation as the cause of TKI resistance.

Comparison of Frequency and Sensitivity of BCR-ABL1 Kinase Domain Mutations in Asian and White Patients With Imatinib-resistant Chronic-Phase Chronic Myeloid Leukemia

INTRODUCTION

BCR-ABL1 mutations require consideration during second-line tyrosine kinase inhibitor selection for patients with chronic myeloid leukemia (CML). The present retrospective analysis compared the frequency of BCR-ABL1 mutations in Asian and white patients in whom imatinib therapy had failed.

PATIENTS AND METHODS

A nonstudy cohort (76 Asian patients from community clinical practices) and 2 study cohorts (29 Asian and 352 white patients from dasatinib phase II and III clinical trials) were identified.

RESULTS

In the nonstudy cohort, 80 mutations were identified; the most frequent was T315I (15%), followed by phosphate-binding loop mutations E255K (11%), G250E (10%), and Y253H (10%). Asian patients had a greater proportion of T315I and phosphate-binding loop mutations compared with the white patients. The nonstudy cohort was less likely to have multiple mutations compared with either study cohort. Single mutations highly resistant to dasatinib, nilotinib, and bosutinib were more frequent in the Asian than in the white cohorts.

CONCLUSION

These results suggest that mutational analysis findings will be invaluable for choosing an appropriate second-line tyrosine kinase inhibitor in Asia.

Chronic Myeloid Leukemia in India

Background

In the last decade, the use of imatinib has brought a paradigm shift in the management of chronic myeloid leukemia (CML). In India, imatinib has been available for more than a decade and has been made accessible to all segments of the population because of patient assistance programs and cheaper generic versions. Despite improvements in survival, there are unique challenges in the Indian context.

Methods

We reviewed published data pertaining to CML in India for the period of 1990 to 2016, using PubMed advanced search with the terms chronic myeloid leukemia and India, and included studies that reported on epidemiology, monitoring for therapy, treatment outcomes, and resistance. Additionally, the references in retrieved articles were also reviewed.

Results

Thirty-seven studies were identified. The incidence of CML may be slightly lower in India than in the West, but there was only a single article reporting population-based data. Indian patients presented with more advanced disease. Most centers have access to imatinib as first-line therapy, but there is limited availability of molecular monitoring and second-line therapy. Most of the outcome data were retrospective but seemed comparable with that reported in Western centers. Drug adherence was impaired in at least one third of patients and contributed to poor survival.

Conclusion

Focused prospective studies and cooperative studies might improve the quality of data available. Future studies should focus on adherence, its effects on outcomes, and methods to address this problem.