Tyrosine Kinase Inhibitors Withdrawal Research Articles

KIR-генетические факторы и ответ на терапию ингибиторами тирозинкиназ при хроническом миелоидном лейкозе

The development of tyrosine kinase inhibitors (TKIs) and their introduction into clinical practice considerably improved the prognosis for chronic myeloid leukemia (CML) patients. About 50 % of patients with achieved deep molecular response are eligible for safe TKI discontinuation. Despite these advances, no reliable biomarkers are known to predict a response and sustaining treatment-free remission after TKI withdrawal. As TKIs do not destroy leukemic stem cells, which can be responsible for relapse, critical importance in CML is attached to natural killers (NK-cells) having antitumor activity. Functional activity of NK-cells is evaluated by expression level and repertoire of killer cell immunoglobulin-like receptors (KIR). Current studies demonstrate that a patient’s KIR genotype affects the probability of achieving early and deep molecular responses to first- and second-generation TKIs, progression-free and overall survivals, and sustaining treatment-free remission. On that ground, KIR-genetic factors can be regarded as promising predictors of response to TKI therapy in CML. Early clinical studies, which dealt with monoclonal antibodies blocking the inhibitory KIR in order to increase NK-cell activity, revealed an acceptable safety profile and efficacy in some hematological diseases (such as acute myeloid leukemia, multiple myeloma, Т-cell lymphoma) if used in combination with cytostatic drugs or antitumor monoclonal antibodies. KIR genotype determination can contribute to the development of effective therapies of this malignant hematological tumor.

Successful Pregnancy and Delivery After Frozen-thawed Embryo Transfer Following the Third Discontinuation of Tyrosine Kinase Inhibitor in a Woman with Chronic Myeloid Leukemia.

Assisted reproductive technology is a viable option for pregnant women with chronic myeloid leukemia. We herein report the case of a patient who underwent successful fertility treatment with frozen embryo preservation at 36 years of age, followed by embryo transfer at 39 years of age, thus resulting in pregnancy and delivery after a third discontinuation of tyrosine kinase inhibitors (TKI). Despite the difficulty of long-term TKI withdrawal, the patient's strong desire for a baby led to a successful pregnancy and delivery with no apparent deformities or abnormalities. Thus, our case highlights the importance of collaboration between reproductive medicine physicians and hematologists.

Interleukin 10 (IL10) and IL15 Significantly Decreased in Chronic Myeloid Leukemia Patients Presenting with Tyrosine Kinase Inhibitor (TKI) Withdrawal Syndrome (TWS). Results from the Prospective, Explorative and Multicenter « Kiwis » Study Designed for TWS. Clinicaltrial.Gov ID: NCT03996096; Study Number: 18-206

Aims Treatment-free remission (TFR) has been included in practice guidelines as a new management goal for chronic myeloid leukemia (CML) patients, implying discontinuation of tyrosine kinase inhibitors (TKI). Paradoxically, TKI discontinuation gives rise to musculoskeletal pain and/or flushing, known as TKI withdrawal syndrome (TWS), in approximately 25% of patients with a reported median time of occurrence of 6 weeks. This syndrome is assumed to be caused by cytokine release, mast cell regrowth, or reactivation of an underlying inflammatory state. The KIWIS trial aimed at assessing these hypotheses by prospectively dosing biological markers before and after TKI discontinuation looking for any significant variation to be correlated to TWS. The secondary objectives were: description of the manifestations of TWS, assessment of TFR. Here, we will only focus on the primary objective. Methods The KIWIS study ( Clinicaltrial.govID: NCT03996096) was a multicenter prospective cohort of adult CML patients who had been treated with TKIs for at least 5 years, with a minimum of 2 years in deep molecular response (MR4.5). Patients with a history of inflammatory disease, those taking steroids, or those unable to complete the short form of the Brief Pain Inventory (BPI) were not included. BPI was used to assess pain severity and its impact on daily functioning. The arithmetic mean of the four severity items was used to score the severity of pain at different time points and identify patients with TWS. Blood samples were collected at baseline (M0), 1 month (M1), 2 months (M2), and 3 months (M3) post-discontinuation of TKI. We explored the following biomarkers: CRP, Rheumatoid Factor, tryptase, calcium, phosphate, Creatin Kinase, IL2, IL6, IL10, TGFβ, TNFα, IFNϒ, VEGF, PDGFβ, IL15, Crosslaps (CTX), Collagen pro-peptide type 1 (PINP1), and parathormone. Each patient served as their own control, and any variation of a biomarker by 20% from baseline was considered clinically significant. The BPI form was completed at the same time points as BCR-ABL follow-up: M0, M1, M2, M3, M4, M5, M6, M8, M10, and M12 following TKI withdrawal. The study was powered to include 50 patients. Results Out of the 50 patients, 16 (32%) developed TWS within the first 3 months, with a median onset time of 2 months. Patients' characteristics are displayed in table1. The baseline characteristics of patients in the TWS and non-TWS groups were similar. The duration of CML treatment was significantly longer in TWS patients compared to non-TWS patients (median: 9, Interquartile Range (IQR) [7-13] vs 7, IQR [6-8], p=0.039, respectively). No predictive factor for developing TWS were observed considering patients' characteristics and BPI scores at M0 in the univariate analysis. At M0, there were no significant differences between the two groups in terms of the concentration of each specific biomarker. In the TWS group, IL10, IL15, and IFNϒ levels decreased between inclusion and the M3 time point. For IL10, the median was 0.18 pg/ml (IQR: 0.12; 0.31) vs. 0.12 (IQR: 0.08-0.17), p=0.002; for IL15, 2.30 pg/ml (IQR: 1.77; 2.92) vs. 1.81 (IQR: 1.48; 2.25), p=0.026; and for IFNϒ, 5.92 pg/ml (IQR: 4.17; 12.49) vs. 4.24 pg/ml (IQR: 2.64; 7.99), p=0.036. In the non-TWS group, no significant differences were found. Changes in IL10 were positively correlated with changes in IL15 from M0 to M3 in all patients: r=0.42, p=0.009. No significant variations were observed in the two patient groups regarding the other biomarkers. Figure 1 exemplifies the evolution of IL10 (A: in TWS patients; B: in non-TWS patients) at M0 and M3. One patient missed the M3 time point sample. Conclusion This is the first study designed to prospectively investigate biomarkers associated with TWS. Our results suggest that TWS is not a cytokine-release-like syndrome but a distinct entity significantly associated with a decrease in IL10, IL15, and IFNϒ concentrations. It is worth noting that IL10 is an anti-inflammatory cytokine known to reduce pain; the role of IL15 and IFNϒ remains to be clarified. We hope that this study will pave the way for further investigations to fully understand the pathophysiology of TWS.

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 < 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.

Incidence of serious adverse events caused by tyrosine kinase inhibitor treatment following immune checkpoint inhibitor therapy in advanced NSCLC patients with oncogenic driver alterations.

Sequential tyrosine kinase inhibitors (TKIs) following immune checkpoint inhibitors (ICIs) increases the incidence of serious adverse events (SAEs). However, the factors and the types of TKIs that affect the incidence of SAEs remain unknown. We retrospectively reviewed advanced non-small cell lung cancer (NSCLC) patients who received sequential TKIs following ICIs between November 2015 and April 2021. All AEs were evaluated using Common Terminology Criteria for Adverse Events (CTCAE) ver 5.0. Among 1,638 NSCLC patients who received ICIs, 63 patients received sequential TKIs following ICIs. The types of TKIs included EGFR-TKIs in 48 patients, ALK-TKIs in 10 patients, and others in 5 patients. The median dosing interval was 57 days (range: 7-698). Eighteen (28.6%) patients developed SAEs (Grade 3/4 or hospitalized). The incidence of SAEs and withdrawal of TKIs due to AEs were significantly higher in patients (n = 40) who initiated TKI treatment within 3months after ICIs than in patients (n = 23) who initiated TKI treatment 3months after ICIs (SAEs, 40.0% vs. 4.3%, p < 0.01; withdrawal rate: 57.5% vs. 21.7%, p < 0.01). There was no significant difference in the incidence of SAEs and withdrawal rate due to AEs between EGFR-TKIs and other TKIs (SAE, 22.9% vs. 40.0%, p = 0.20; withdrawal rate: 41.7% vs. 53.3%, p = 0.55). The dosing interval from last ICI to the initiation of TKI treatment can affects the incidence of SAEs and the withdrawal rate due to AEs regardless of the types of TKIs.

Successful delivery using interferon α for molecular relapse of chronic myeloid leukemia after interruption of tyrosine kinase inhibitor

A tyrosine kinase inhibitor (TKI) was used to treat the patient, a 35-year-old woman who was diagnosed with chronic myeloid leukemia at the age of 22 years. Since a four-year deep molecular response (DMR) was obtained, spontaneous pregnancy was planned under TKI withdrawal. Even though her disease had advanced to MR2.0 at the time of pregnancy confirmation, 2 months from TKI cessation, interferon α therapy was initiated in light of the patient's history. Later, the patient reached MR3.0, gave birth to a healthy baby, and maintained MR3.0-4.0. TKI was resumed after about 6 months of breastfeeding. Treatment-free remission (TFR) is required for natural conception despite the teratogenicity and miscarriage risks associated with BCR::ABL1 TKIs. When planning a pregnancy, it is also necessary to take the patients' backgrounds, disease states, and medical history into account.

Duration of ≥MR4 Is the Best Predictor for a Successful 1st Treatment-Free Remission (TRF1) Attempt in CML Patients Treated with Tyrosine Kinase Inhibitors (TKI); Long-Term Follow-up of a Large Cohort of Patients Including a Cohort Undergoing a 2nd Tfr (TFR2) Attempt

Background: Prior to TKIs, CML was uniformly fatal unless the patient underwent allogeneic-HSCT. With TKIs, some patients achieve deep molecular responses with bcr-abl <0.01% (MR4); a portion of such patients can achieve long-term TFR, possibly cure, after TKI cessation. This approach is now considered the goal for every newly diagnosed CML patient. We present a single centre experience, with long-term follow up, of a cohort of CML patients undergoing TFR1 and TFR2 attempts. Method: Our database of 173 patients diagnosed with CML from 1994 to 2022 was searched for patients who had the potential to be eligible for a TFR attempt (pending adequate response to TKI): CML diagnosed in 1st chronic phase (CP1); no allogeneic HSCT in CP1; >3 yrs treatment with TKI; adequate follow-up. 120 patients fulfilled these criteria. Results: 70/120 (58%) achieved accepted criteria to attempt TFR: >3 years of TKI treatment; a deep molecular response (≥MR4) and underwent TFR attempt. Median age at diagnosis was 49.5 (20-81) yrs; 42% were female. Sokal score was low in 38%; intermediate in 29%; high in 33%. 66% of patients received multiple TKIs; 23% had received interferon. TKI at time of TFR1 attempt was imatinib (40%), nilotinib (30%), dasatinib (27%), and ponatinib (3%). Median time from diagnosis to TFR was 8.5 (4-23) yrs and median time on TKI was 7.5 (3.4-17.9) yrs. 36/70 (51%) remain in TFR with median follow-up of 46 (1-180) mths including; 16 patients now >5 yrs and 2 now >10 yrs in ongoing TFR; the cohort includes 2 patients with historically acquired bcr-abl mutations and 1 with a historically acquired additional cytogenetic abnormalities (no longer present at TFR1 attempt). All 3 are long-term TFR successes. Median time to relapse was 5 (2-36) mths, 25/34 (73.5%) relapsed within 6 mths of TKI withdrawal and 28/34 (82.4%) within 12 mths. Time of relapse for 1 patient is unknown. The remaining 5 patients relapsed at 13, 14, 18, 20, and 36 mths. All patients with CML recurrence (bcr-abl >0.1%) restarted TKI with a rapid return to major molecular response (MMR) or better (2 are too early for assessment) with median time to MMR of 3 (1-12) mths. No patient developed CML with high-risk features or blast phase. The strongest predictors for TFR success were duration of MR4 prior to attempting TFR1 (Table 1) - 60% (25/42) of patients with >5 yrs of ≥MR4 prior to cessation remain in TFR, compared to 55% (11/20) with 3-5 yrs and 0% (0/7) of patients with <3 yrs (p<0.03 for <3 vs 3-5 yrs and <3 vs >5 yrs, p=0.79 for 3-5 vs >5 yrs) ; prior treatment with interferon (81% - 13/16 - of patients who received interferon remain in TFR compared to 37% - 20/54 - who had not received interferon, p=0.0035), and a Sokal score <0.8 (64% of patients with low Sokal score remain in TFR compared to 45% with a score 0.8-1.2 and 45% with a score >1.2, p=0.35 for <0.8 vs 0.8-1.2, p=0.16 for <0.8 vs >1.2, p=1 for 0.8-1.2 vs >1.2). 6 patients had transient rises in their bcr-abl (>0.01%), ranging from 0.012 - 0.033, but these 6 returned to MR4 or better and remain in TFR for 8-77 mths. 13 (38%) of the 34 failed TFR1 patients attempted TFR2. Median time on TKI between 1st and 2nd attempts was 5.7 (4.8-8.9) yrs and had a median time ≥MR4 of 5.4 (4.6-8.8) yrs. Median follow up was 12 (1-27) mths. Currently, 9 (69%) patients remain in TFR2. Of the 4 patients who relapsed, all did so in the first 6 months after TKI withdrawal. 17 patients (25%) developed a withdrawal syndrome. Symptoms included fatigue, myalgias, and arthralgias. All but 4 patients had resolution over a median of 11 (1-25) mths. 3 patients benefited from a course of prednisolone. 4 patients have had persistent symptoms for median 12.5 (10-19) mths. Conclusion: Of 120 patients with adequate duration of TKI, 58% were eligible for TFR1 attempt which, to date, is successful in 51%. Prior interferon treatment, longer period in ≥MR4 and a Sokal score <0.8 predicted a successful TFR. For those that fail TFR1, TFR2 appears safe, and with short follow-up, currently 9/13 (69%) patients remain off treatment. In our cohort, overall 64% (45/70; 36 TFR1 + 9 TFR2) of patients eligible for TFR attempts remain off TKI giving an actual or functional cure rate of 38% (45/120). Historically acquired bcr-abl mutations or additional cytogenetic abnormalities are not necessarily contraindications to a TFR attempt - with 3 long-term TFR successes in our cohort. TFR is safe with no cases of disease progression, and all patients with TFR failure and adequate duration of follow-up regaining MMR. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Long-Term Follow-up of Tyrosine Kinase Inhibitors Discontinuation in Chronic Myeloid Leukemia: A Single-Center Experience

Introduction: Ever since the availability of BCR-ABL1 tyrosine kinase inhibitors (TKIs) as treatment for chronic myeloid leukemia (CML), life expectancy of patients has dramatically improved, approaching that of the overall population. Several clinical trials have demonstrated the possibility of discontinuing TKI. However, the information on the safety of long-term TKI cessation is still limited. Methods: We carried out a descriptive, retrospective and single-center study, including 56 patients with CML who discontinued TKI treatment between January 2006 and July 2022. We defined strict molecular relapse as loss of MR4 (BCR-ABL1 International Scale (IS) ≤ 0,01% or undetectable BCR-ABL1 in samples with ≥10.000 transcripts), loose molecular relapse as loss of major molecular response (MMR) (BCR-ABL1 IS ≤ 0,1% in samples with ≥10.000 transcripts) and deep molecular response (DMR) as response greater than or equal to MR4. Progression-free survival (PFS) was estimated by the method of Kaplan-Meier and defined as the time from TKI discontinuation to the date of first event (loss of DMR or death). Results: We included 56 patients (table 1). Median age at time of stopping TKI treatment was 60,3 (50,7-75,8) years and 35 (62,5%) were male. 44 patients had received 1 line of TKI treatment, 7 two lines, 2 three lines and 3 four lines. The previous TKI treatment consisted of imatinib (n=34), nilotinib (n=6), dasatinib (n=34), two lines of imatinib because of pregnancy (n=1), imatinib dasatinib (n=3), imatinib nilotinib (n=1), dasatinib imatinib (n=1), dasatinib ponatinib (n=1), imatinib dasatinib nilotinib (n=1), nilotinib dasatinib nilotinib (n=1), imatinib dasatinib imatinib dasatinib (n=1), imatinib nilotinib dasatinib dasatinib+asciminib (n=1), imatinib nilotinib dasatinib nilotinib (n=1). Duration of imatinib treatment was 121,5 (100-172,8) months, dasatinib 74,4 (29-86,1), nilotinib 34,3 (19,1-45,6), ponatinib 49 and asciminib 20,7. The reasons for switching from first to second line were intolerance (n=7, 58,3%), resistance to any TKI (n=4, 33,3%) and pregnancy (n=1, 8,3%). From second to third line was intolerance (n=5, 100%). Duration of DMR before TKI discontinuation was 87,6 (49,2-116,4) months. The last molecular responses before TKI cessation were RM5 (n=18, 32,1%), RM4.5 (n=28, 50%), RM4 (n=9, 16%) y MMR (n=1, 1,8%). Reasons for TKI discontinuation were the presence of side effects (n=28, 50%), an attempt to achieve a treatment-free remission (TFR) in patients with a DMR (n=16, 28,6%), patient preference (n=10, 17,8%) and pregnancy (n=2, 3,6%). After TKI discontinuation, 34 (60,7%) patients have maintained DMR for a median of 4,22 (2,12-7,14) years, of which six more than 8 years being the maximum follow-up of 12,6 years. 5 patients had died while DMR due to CML-unrelated causes. The probability of PFS at 1 year and 12,6 years was 65,3% (95% CI: 58,6%-71,7%) and 34,8% (95% CI: 25%-44,1%) respectively (Figure 1). 22 (39,28%) patients had strict molecular relapse with a median of 3,9 (3,2-7,8) months, of which 12 (21,4%) were loose molecular relapses. Loss of DMR occurred most frequently in the first 6 months after TKI discontinuation (n=15, 68,1%). The last CMR loss was at 95 months. 18 patients restarted treatment, 2 died due to CML-unrelated causes, 1 maintained RMM without treatment due to intolerance and 1 stopped treatment due to personal preference. At the time of restarting treatment, the BCR-ABL1 IS was ≤10% (n=3), ≤1% (n=7), ≤0,1% (n=7) and ≤0,01% (n=1). After restarting treatment, 18 (100%) patients had MMR, of whom 16 (80%) had DMR. Median time to regaining DMR after resuming TKI therapy was 3 (0,9-3,05) months. A second attempt at TFR was made in 5 patients. The median duration of TKI therapy after restarting the treatment and the second discontinuation was 60,2 (40,2-63) months. 4 patients maintained CMR with a follow-up of 11 (7,2-24,4) months, and one patient died while DMR for reasons unrelated to CML. Adverse effects improved in most patients. TKI withdrawal syndrome was noticed in 12 (21,4%) patients. Conclusion: In our study, the PFS at 12,6 years was 34,8%. Including the patients who have had a second discontinuation of TKI, 39 (69,6%) patients remain in DMR off-treatment, with a median follow-up of 49,1 (26,7-85,7) months. 6 patients had a follow-up of more than 8 years without treatment, which is still ongoing. These data confirm the applicability and safety of TKI discontinuation. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

A Retrospective Analysis of TKI Discontinuation in Patients with CML

To investigate the clinical characteristics of the patients with chronic myeloid leukemia (CML) discontinued tyrosine kinase inhibitors (TKI) therapy and the outcome of the patients. 35 cases of CML patients experienced initiative discontinuation of TKI therapy in our hospital from June 1st 2015 to December 31th 2019 were retrospectively analyzed. The TFR of the patients and the factors affecting it were analyzed. The median duration of TKI administration was 72 (range 35-173) months in the 35 patients. Among these patients, 8 had experienced TKI dose reduction or suspension. All the enrolled patients have achieved at least MMR. The median time for these patients achieving MMR was 15 (range 3-75) months after administration of TKI, and for MMR maintenance before TKI suspension was 55 (range 13-164) months. After TKI withdrawal the median follow up time was 20.3 (range 3-57.9) months, 22 out of 35 patients kept TFR, among them, 2 （5.71%） patients restarted TKI after 12 month suspension, and maintained MMR during suspension. 13 （37.1%）patients lost MMR, among them, 9 patients restarted TKI treatment, and 5 of them achieved MR4.0 after the median duration of 3(2-5) month. No patients were found to have disease progression. The estimated TFR rate was 57.8% and 51.8% at 12 and 24 months after discontinuation, respectively. Other clinical characteristic related to relapse were also analyzed, including the cumulative TKI administration duration, cumulative MMR duration, time to achieve MMR, median age at diagnosis, risk stratification by Sokal score, TKI dose reduction and discontinuation history, and second-generation TKI administration before stopping TKI, however, no statistical difference was found. TKI discontinuation is practical for CML patients in our center.

Half: A Prospective Multi-Centre Phase II Clinical Trial Evaluating the Efficacy and Safety of Tyrosine Kinase Inhibitors' Discontinuation after Two-Step Dose Reduction in Patients with Chronic Myeloid Leukemia in Deep Molecular Remission

Background.Treatment-free remission (TFR) has become a new treatment goal for chronic myeloid leukemia (CML) patients. However, usually abrupt tyrosine kinase inhibitors (TKIs) therapy discontinuation has been successful only in about half of eligible patients and it can cause burdening TKI withdrawal syndrome (TWS) in about 30% of them. Moreover, any robust clinical or biological factor predictive for successful TFR has not been identified yet. On top of that, sustainable deep molecular response (DMR) as the main prerequisite for TKI discontinuation attempt is achieved only in 20-40% of patients. The majority of CML patients, therefore, need to be treated with the effective and well-tolerated drug for a long time or even life-long.Study design and methods.With the recognition of all these aspects, we designed a nationwide prospective investigator-initiated phase II clinical trial HALF (ClinicalTrials.gov NCT04147533) in order to evaluate efficacy and safety of TKI discontinuation after previous two-step dose reduction in patients with CML in DMR (Fig. 1). Step-wise TKI dose reduction, i.e. half of the standard during the first 6 months after study entry, and the same dose given alternatively (every other day) during the next 6 months, was derived from pharmacokinetics and experimental data as well as from clinical trials' results. We assume that the step-wise and eventually meaningful TKI dose reduction enables a higher rate of patients achieving successful TFR with less pronounce TWS, or even would represent a more reasonable and safer alternative to the complete and sudden TKI interruption. This unique nationwide academic project has been facilitated by hematological patients care centralization in the Czech Republic.A primary study objective is to evaluate the proportion of patients in major molecular response (MMR) at 6 and 12 months and in TFR at 18, 24, and 36 months after the study enrollment, respectively, and molecular recurrence-free survival at all mentioned time points as well. Main secondary and exploratory objectives are: to evaluate the proportion of patients loosing MMR and in whom MMR and MR4.0 would be re-achieved after TKI re-introduction, time to MMR and MR4.0 re-achievement, FFS, PFS, OS, TWS, and QoL assessment, predictive factors for successful TFR identification, quantification of BCR-ABL1 using digital droplet PCR at both the DNA and mRNA levels, immunological profiling, BCR-ABL1 kinetics mathematical modeling, assessment of TKI pharmacokinetics, clonal hematopoiesis and pharmaco-economics.Results.The study was launched in December 2019; however, due to the COVID-19 outbreak, patients' recruitment started on June 16, 2020. Here, characteristics of the first 74 patients included in the study until April 2021 are presented. There were 37 males and 37 females, with median age at the time of diagnosis of 53 years (range, 23-74) and at the time of the study entry of 67 years (range, 35-86). A median time of CML disease, TKI treatment, and DMR duration before the study initiation was as follows: 9.9 years (range, 4.4-22.5), 9.8 years (range, 4.2-20.2), and 7.3 years (range, 3.2-18.3), respectively. The ELTS score was low, intermediate, high and unknown in 62.2%, 21.6%, 13.5%, and 2.7% of patients, respectively. At the time of study entry, 58 patients (79.5%) were treated with imatinib, 10 (13.7%) with nilotinib, and 5 (6.8%) with dasatinib, respectively, whereas in 63 patients (86.3%) it was in the first line of therapy. With almost half of patients (48.6%), the TKI dose was already reduced at the time of study entry. With 10 (13.5%) patients, interferon-α treatment preceded TKI administration. At the time of this abstract preparation, on July 26, 2021, altogether 102 patients (from planned 150) have been enrolled in the study; 48 of them (47.1%) have already moved to the second de-escalation phase and 9 (8.8%) patients to the TFR phase. There were 2 cases of confirmed MMR loss (both in month 8 after the study entry) and no patient experienced symptoms resembling TWS.Conclusions.Despite the COVID-19 pandemic, the HALF study was successfully launched and initiated in the majority of centers, with 102 already included patients and continuing intensive enrolment. Based on our very preliminary results, the step-wise dose reduction seems to be an effective and safe approach. More included patients, longer follow-up and further analyses are needed in order to reach all set up objectives. [Display omitted] DisclosuresŽácková: Angelini: Consultancy, Speakers Bureau; Novartis: Speakers Bureau. Faber: Angelini: Consultancy, Other: conference fees, Research Funding, Speakers Bureau; Bristol-Myers Squibb: Consultancy, Other: conference fees, Research Funding, Speakers Bureau; Novartis: Consultancy, Other: conference fees, Research Funding, Speakers Bureau; Pfizer: Other: conference fees; TERUMO: Other: conference fees. Bělohlávková: Novartis: Consultancy; BMS/Celgene: Consultancy. Horňák: Angelini: Honoraria. Svobodník: Roche: Speakers Bureau; Janssen-Cilag: Speakers Bureau. Machová Poláková: Incyte: Consultancy; Angelini: Consultancy; Novartis: Research Funding. Mayer: Principia: Research Funding.

Targeted therapy for drug-tolerant persister cells after imatinib treatment for gastrointestinal stromal tumours.

Despite the effectiveness of tyrosine kinase inhibitors (TKI), gastrointestinal stromal tumours (GIST) develop after the withdrawal of TKI. Based on previous studies, a subpopulation of drug-tolerant cells called "persister cells" may be responsible for the recurrence and have thus, gained attention as a novel target in cancer therapy. The metabolic changes were investigated in imatinib-derived persister GIST cells. We investigated the efficacy and the mechanism of GPX4 inhibitor, which is known as a major inducer of "ferroptosis". We also evaluated the effects of RSL3 to the gefitinib-derived persister lung cancer cells. We demonstrated a downregulation of glucose metabolism, subsequent decrease in the glutathione level and sensitivity to glutathione peroxidase 4 (GPX4) inhibitor, RSL3 in persister cells. As the cell death induced by RSL3 was found to be "iron-dependent" and "caspase-independent", loss of GPX4 function could have possibly induced selective persister cell ferroptotic death. In the xenograft model, we confirmed the inhibition of tumour regrowth after discontinuation of imatinib treatment. Moreover, RSL3 prevented the growth of gefitinib-derived persister lung cancer cells. RSL3 combined with TKI may be a promising therapy for both GIST and epidermal growth factor receptor-mutated lung cancer.

Persistence of Residual Circulating CD26+ Leukemia Stem Cells in Chronic Myeloid Leukemia Patients in Treatment Free Remission

Chronic myeloid leukemia (CML) patients achieving a deep and stable molecular response with tyrosine kinase inhibitors may discontinue TKI therapy and count on 50% about probability to maintain a “treatment free remission” (TFR) which is today the best surrogate for “cure” in CML. Albeit indispensable for attempting TFR, deepness and duration of molecular response are not the only criteria for a successful TFR as half of CML patients (pts) meeting those criteria still loose the response within 6-12 months after TKI discontinuation. Available data suggest that relapse after TKIs withdrawal is due to the persistence of leukemic stem cells (LSCs) intrinsically resistant to TKIs, however the presence and the impact of residual LSCs in CML patients in TFR has not been explored yet.CD34+/CD38-/Lin- CML LSCs specifically co-express dipeptidylpeptidase IV (CD26). We have recently demonstrated that CD26+ LSCs are easily detectable by flow-cytometry also in peripheral blood of CML pts both at diagnosis and during tyrosine kinase inhibitors (TKIs) treatment (Bocchia M, Blood 2016 128:942). The number of circulating residual CD26+LSCs appeared not correlating to the degree of molecular response, suggesting that residual TKI resistant quiescent LSCs may be transcriptionally low/silent and thus potentially not quantifiable by standard qRT-PCR analysis.We here evaluated the presence of circulating CD26+ LSCs in CML patients in TFR referring to several Italian hematology centers. During a follow-up visit, in which patients were checked for standard PB BCR-ABL1 molecular response, 3-6 mls of PB were collected in EDTA and sent to Siena Hematology Lab to detect CD34+/CD38-/CD26+ LSCs by multicolor flow cytometry. Cells were incubated with anti CD45, CD34 (581), CD38 (HIT2), CD26 (M-A261). Acquisition and analysis were performed by FACSCantoII using DIVA8 software.A total of 84 CML pts in TFR for a median of 31 months (range 2-192) were evaluated. All 84 patients were in first line treatment at the time of TKI withdrawal. Fifty-one out of 84 (60%) pts discontinued imatinib treatment and were in TFR for a median of 37 months (range 2-192); 14/84 (17%) pts discontinued dasatinib and were in TFR for a median 32 months (range 5-90) and 19/84 (23%) pts were in TFR for a median of 18 months (range 3-39) after nilotinib treatment.PB CD26+ CML LSCs were measurable in 54/84 (64%) pts with a median number of 0,0132 cells/µL (range 0,0053-1,77) while only 24/84 (28%) pts showed detectable BCR-ABL copies (median BCR-ABL/ABLIS ratio 0,0062 range 0,0032-0,493). Indeed, 18/84 (21%) pts showed both circulating CD26+ LSCs and detectable BCR-ABL, 26/84 (31%) pts scored negative for both determinations, while 36/84 (43%) pts showed detectable CD26+ LSCs and undetectable BCR-ABL. Only 4/84 (5%) pts showed measurable BCR-ABL copies with undetectable CD26+ LSCs.Kendall rank correlation coefficient, Mood test and bi-linear relation model of the whole cohort showed no correlation between BCR-ABL/ABLIS ratio and number of residual LSCs, while a significant linear inverse correlation was found between number of circulating CD26+ LSCs and TFR duration (r=-0.055 p <0.01 p=0.0063). Similar results were found also when considering only 51 pts in TFR after imatinib. A statistical analysis focusing on dasatinib and nilotinib subgroup of pts was not possible for due to the reduced sample size.This is the first time that residual circulating CML LSCs are detected in TFR CML pts even after long lasting TKI discontinuation and deep stable molecular response. Intriguingly, the evaluation of CD26+ LSCs appeared a more sensitive method than qRT-PCR to detect residual “quiescent” disease. The reason why CML LSCs may persist in pts who discontinued TKI, without resulting in an overt disease, it's still unknown but likely a CML LSCs specific immune control plays a crucial role. An ongoing prospective study, recruiting a consistent number of pts, monitoring the dynamics of circulating CD26+LSCs from TKI discontinuation may answer some still open questions. LSCs' clinical role, correlation with type and duration of previous TKI treatment as well interaction with active specific immune system will be investigated. DisclosuresBocchia:Roche: Other: Travel grant; Celgene: Other: Travel grant; Novartis: Other: Travel grant; Jansen: Other: Travel grant. Abruzzese:Novartis: Consultancy; Incyte: Consultancy; BMS: Consultancy; Pfizer: Consultancy. Galimberti:Incyte: Speakers Bureau; Bristol-Myers Squibb: Speakers Bureau; Novartis: Speakers Bureau; Pfizer: Speakers Bureau. Fava:Incyte: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria. Castagnetti:Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria; Incyte: Consultancy, Honoraria. Iurlo:Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria. Crugnola:BMS: Honoraria; Celgene: Honoraria; Novartis: Honoraria. Rosti:Pfizer: Research Funding, Speakers Bureau; Incyte: Research Funding, Speakers Bureau; Bristol Myers Squibb: Research Funding, Speakers Bureau; Novartis: Research Funding, Speakers Bureau.

“Duration of Deep Molecular Response” Has Most Impact on the Success of Cessation of Tyrosine Kinase Inhibitor Treatment in Chronic Myeloid Leukemia - Results from the EURO-SKI Trial

“Duration of Deep Molecular Response” Has Most Impact on the Success of Cessation of Tyrosine Kinase Inhibitor Treatment in Chronic Myeloid Leukemia - Results from the EURO-SKI Trial

Factors for Sustaining Molecular Remission after Discontinuation of Tyrosine Kinase Inhibitors Therapy in Chronic Myeloid Leukemia: Results of Non-Randomized Prospective Clinical Trial

Aim. To study the impact of different clinical and biological factors on sustaining molecular remission after discontinuation of tyrosine kinase inhibitors (TKI) therapy in chronic myeloid leukemia (CML) patients with a stable deep molecular response (MR). Materials &amp; Methods. The prospective multi-center trial on molecular remission sustainability after TKIs withdrawal, held from 2015 to 2019, enrolled 98 CML patients. The trial included patients with chronic phase CML treated with TKIs at least during 3 years and having a stable deep MR (&lt; МО4; BCR-ABL &lt; 0.01 %) during at least 2 years. Molecular monitoring was carried out every month during first 6 months after TKIs withdrawal, every 2 months during 0.5-1 year, and every 3 months after 1-year follow-up. In case of the loss of major MR (BCR-ABL &gt; 0.1 %) therapy was reinitiated. Results. Three-year molecular relapse-free survival was 51 % (95% confidence interval 41-61 %) in all patients, 25 % in patients with the failure of prior treatment discontinuation, and 53 % in patients who discontinued TKI therapy for the first time. According to univariate analysis, the following factors proved to be significant: persistance of deep MR, duration of therapy, and depth of MR. It was shown that TKI therapy duration, but not deep MR persistance, has independent prognostic value for the Russian population of CML patients. No significant differences were identified in 3-year molecular relapse-free survival in the groups of patients treated only with imatinib (55 %) compared with patients who received 2nd generation TKI (TKI2) as first-line (70 %; p = 0.26) and second-line (39 %; p = 0.09) therapy. However, duration of therapy in patients treated with TKI2 as first-line therapy was more than twice as short as in patients treated with imatinib as first-line therapy (median 41.5 vs. 96.4 months, respectively; p &lt; 0.0001). Conclusion. Longer therapy duration and MR depth (&lt; M04.5) before TKI withdrawal raise the probability of sustaining off-treatment remission. The study showed that molecular relapse-free survival does not significantly increase with the use of TKI2 as first-line treatment compared to imatinib. Nevertheless, TKI2 as first-line treatment enables to halve the duration of therapy needed to achieve comparable molecular relapse-free survival, as compared with imatinib.

Biological Mechanisms of Sustaining Deep Molecular Response in Chronic Myeloid Leukemia Upon Withdrawal of Tyrosine Kinase Inhibitors

The feasibility of treatment-free follow-up in chronic myeloid leukemia (CML) patients is an important issue in the era of tyrosine kinase inhibitors (TKI). The clinical trials of TKI withdrawal in case of a stable deep molecular response prove the probability of sustaining molecular remission in 40-60 % of patients. Treatment-free remission (TFR), even under persistence of residual leukemia cells, suggests that there are special biologically determined mechanisms of tumor cell proliferation control, which are independent of BCR-ABL kinase activity. The search for factors determining differences in residual leukemia clone kinetics upon TKI withdrawal is an objective which is crucial for understanding TFR as a new biological phenomenon. The review provides worldwide evidence dealing with the study of immunological, genetic, and other biological mechanisms underlying the control of minimal residual disease upon TKI discontinuation in CML patients.

Chronic myeloid leukemia: aiming for treatment free remission

BCR-ABL tyrosine kinase inhibitors (TKIs) dramatically improve the chronic myeloid leukemia (CML) prognosis, and most CML patients in the chronic phase are now able to lead lives that are comparable to those of healthy individuals. However, the high cost and adverse effects associated with long-term treatment remain issues in the treatment of CML patients. At the setout, a clinical study involving the discontinuation of imatinib was conducted in France. Thereafter, several TKI stop studies of first-generation (imatinib) and second-generation TKIs (dasatinib, nilotinib) have shown an earlier response than that with imatinib. These studies revealed that almost 50% of CML patients who were treated with TKIs and achieved a certain period of sustained deep molecular response can stop TKIs safely and obtain sustained treatment-free remission (TFR). Adverse effects of TKI withdrawal and predicting factors for successful discontinuation including immunity are gradually becoming clear via these studies. For superior CML treatment, several promising agents, including ABL001, are being developed. I trust that these efforts will enable CML patients to maintain TFR in the near future.

A prospective study of the monitoring of patients with chronic myeloid leukemia upon withdrawal of tyrosine kinase inhibitor therapy

Introduction. The advent of tyrosine kinase inhibitors (TKIs) in clinical practice drastically improved prognosis in patients with chronic myeloid leukaemia (CML). Adverse events of the TKI therapy and its high financial burden warrant the trend to gradually abandon this treatment.Aim. To assess the results of CML patient monitoring after the withdrawal of TKI therapy.Patients and methods. This prospective study included 98 chronic phase CML patients satisfying the criteria: any receiving of TKI therapy for ≥3 years; deep molecular response (DMR, BCR-ABL ≤ 0.01 % IS) during ≥ 2 years. The withdrawal was followed by quantitative BCR-ABL estimation performed monthly for the first 6 months of the survey, bimonthly for 1 year and every 3 months from the second year onwards. Therapy was resumed at a loss of major molecular response (MMR, BCR-ABL ≥ 0.1 % IS).Results. The MMR loss upon the TKI withdrawal was observed in 48 (49 %) patients. Survival without MMR loss was 52 % past 24 months since withdrawal, with a median of 35 months (23–52). The duration of therapy, MR and the MR depth at the time of withdrawal significantly correlated with a conserved post-therapy MMR. Gender, age, a Sokal risk group, type and line of TKI therapy at withdrawal, and imatinib resistance in history were not observed to significantly impact molecular relapse-free remission. MMR was recovered in all 48 patients with TKI therapy resumed in molecular relapse. In 65 % of the patients, adverse therapy events observed during treatment completely resolved by 6 months of post-therapy monitoring. Musculoskeletal pain (withdrawal syndrome, WS) was reported in 42 % patients in the post-therapeutic period, which did not lead to TKI resumption. The WS development correlated with an elder age and longer therapy prior to withdrawal.Conclusion. Molecular relapse-free survival in CML patients with treatment-free remission (TFR) is comparable to other published evidence. Monitoring safety during TFR is attested by the lack of disease progression and MMR recovery upon TKI resumption in all patients.

Elucidation of protein interactions necessary for the maintenance of the BCR-ABL signaling complex.

Many patients with chronic myeloid leukemia in deep remission experience return of clinical disease after withdrawal of tyrosine kinase inhibitors (TKIs). This suggests signaling of inactive BCR-ABL, which allows the survival of cancer cells, and relapse. We show that TKI treatment inhibits catalytic activity of BCR-ABL, but does not dissolve BCR-ABL core signaling complex, consisting of CRKL, SHC1, GRB2, SOS1, cCBL, p85a-PI3K, STS1 and SHIP2. Peptide microarray and co-immunoprecipitation results demonstrate that CRKL binds to proline-rich regions located in C-terminal, intrinsically disordered region of BCR-ABL, that SHC1 requires pleckstrin homology, src homology and tyrosine kinase domains of BCR-ABL for binding, and that BCR-ABL sequence motif located in disordered region around phosphorylated tyrosine 177 mediates binding of three core complex members, i.e., GRB2, SOS1, and cCBL. Further, SHIP2 binds to the src homology and tyrosine kinase domains of BCR-ABL and its inositol phosphatase activity contributes to BCR-ABL-mediated phosphorylation of SHC1. Together, this study characterizes protein-protein interactions within the BCR-ABL core complex and determines the contribution of particular BCR-ABL domains to downstream signaling. Understanding the structure and dynamics of BCR-ABL interactome is critical for the development of drugs targeting integrity of the BCR-ABL core complex.

The mechanism of cancer drug addiction in ALK-positive T-Cell lymphoma.

Rational new strategies are needed to treat tumors resistant to kinase inhibitors. Mechanistic studies of resistance provide fertile ground for development of new approaches. Cancer drug addiction is a paradoxical resistance phenomenon, well-described in MEK-ERK-driven solid tumors, in which drug-target overexpression promotes resistance but a toxic overdose of signaling if inhibitor is withdrawn. This can permit prolonged control of tumors through intermittent dosing. We and others showed previously that cancer drug addiction arises also in the hematologic malignancy ALK-positive anaplastic large-cell lymphoma (ALCL) resistant to ALK-specific tyrosine kinase inhibitors (TKIs). This is driven by overexpression of the fusion kinase NPM1-ALK, but the mechanism by which ALK overactivity drives toxicity upon TKI withdrawal remained obscure. Here we reveal the mechanism of ALK-TKI addiction in ALCL. We interrogated the well-described mechanism of MEK/ERK pathway inhibitor addiction in solid tumors and found it does not apply to ALCL. Instead, phosphoproteomics and confirmatory functional studies revealed STAT1 overactivation is the key mechanism of ALK-TKI addiction in ALCL. Withdrawal of TKI from addicted tumors in vitro and in vivo leads to overwhelming phospho-STAT1 activation, turning on its tumor-suppressive gene-expression program and turning off STAT3’s oncogenic program. Moreover, a novel NPM1-ALK-positive ALCL PDX model showed significant survival benefit from intermittent compared to continuous TKI dosing. In sum, we reveal for the first time the mechanism of cancer-drug addiction in ALK-positive ALCL and the benefit of scheduled intermittent dosing in high-risk patient-derived tumors in vivo.

Prospective Monitoring of Peripheral Blood CD26+ Leukemia Stem Cells in Chronic Myeloid Leukemia Patients from Time of TKI Discontinuation

Prospective Monitoring of Peripheral Blood CD26+ Leukemia Stem Cells in Chronic Myeloid Leukemia Patients from Time of TKI Discontinuation