Discontinuation of Tyrosine Kinase Inhibitors in Chronic Myeloid Leukemia: What s Stopping us from Stopping?

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1 Discontinuation of Tyrosine Kinase Inhibitors in Chronic Myeloid Leukemia: What s Stopping us from Stopping? David Pham, PharmD PGY2 Hematology/Oncology Pharmacy Resident South Texas VA Health Care System Division of Pharmacotherapy, The University of Texas at Austin College of Pharmacy Pharmacotherapy Education and Research Center, UT Health San Antonio San Antonio, Texas January 11, 2019 Learning Objectives: 1. Describe the disease state, diagnosis, and management of chronic myeloid leukemia (CML) 2. Compare and contrast tyrosine kinase inhibitors and other agents used in the management of CML 3. Evaluate the available literature regarding potential discontinuation of tyrosine kinase inhibitor therapy in CML 4. Evaluate the available literature regarding potential second discontinuation of tyrosine kinase inhibitor therapy in CML Pham 1

2 Chronic Myeloid Leukemia I. Definition 1 A. Myeloproliferative neoplasm that affects the myeloid lineage of the hematopoietic stem cell differentiation pathway B. Results in the overproduction of immature myeloid blast cells C. Affects the production and maturation of red blood cells, white blood cells, and platelets Figure 1. Stem Cell Differentiation Pathway Table 1. Phases of CML 2,F10 Chronic Phase (CP) Accelerated Phase (AP) Blast Phase (BP) Majority of Characterized by symptoms and increasing blast Presents and behaves like an patients are count acute leukemia diagnosed during Can progress to blast phase if left untreated Patients symptomatic with chronic phase Worse prognosis high blast count May or may not Behaves like acute leukemia be symptomatic Worst prognosis but typically Modified criteria per MD Anderson Cancer Center Criteria per International Bone responsive to Criteria Marrow Transplant Registry standard Peripheral blood myeloblasts between 15-30% 30% blasts in blood, bone treatments Peripheral blood myeloblasts and promyelocytes marrow, or both Can progress to combined 30% Extramedullary infiltrates of accelerated or Peripheral blood basophils 20% leukemic cells blast phase if left Platelets 100 x 10 9 /L unrelated to therapy untreated Additional clonal cytogenetic abnormalities in Ph+ cells II. Background 2 A BCR-ABL1 first identified by Drs. Nowell and Hungerford in Philadelphia, PA and CML becomes first leukemia with chromosomal abnormality linked to pathophysiology B. Historically, interferon was a standard therapy for the treatment of CML i. Poor outcomes 10-year survival of approximately 20% ii. Toxic regimen flu-like symptoms, depression, pancytopenia C. Identified driver mutation found in 95% of CML cases i. Target mutation treatment tyrosine kinase inhibitors ii. TKIs improve outcomes 10-year survival of approximately 84-90% a. Good efficacy with lifelong treatment b. Tolerable adverse effect profile Pham 2

3 III. Pathophysiology 2,5 A. Abelson murine leukemia (ABL1) gene on chromosome 9 B. Breakpoint cluster region (BCR) gene on chromosome 22 C. Translocation (9;22) i. Oncogene constitutively active ii. Philadelphia chromosome iii. iv. Driver mutation for CML Utilizes a downstream signaling pathway Figure 2. Philadelphia Chromosome Figure 3. BCR-ABL Tyrosine Kinase Pathway IV. Epidemiology 2,3,4 A. Constitutes approximately 15% of all new leukemia diagnoses in adults B. Lifetime risk i. Approximately 1 in 526 Americans will develop CML in their lifetime ii. About 50% of individuals with newly diagnosed CML are age 65 or older at the time of diagnosis C. Incidence i. Affects approximately 1-2 individuals per 100,000 adults ii. An estimated 8,430 individuals will be diagnosed with CML in 2018 with approximately 1,090 deaths D. Survival Pham 3

4 i. 10-year overall survival increased from ~20% to ~80-90% after 2001 Figure 4. CML Survival Over Time V. Clinical Presentation 2,5,10 A. Signs and symptoms i. ~50% of patients asymptomatic diagnosis made after incidental findings ii. Symptomatic patients may have fatigue, weight loss, splenomegaly, night sweats, easy bleeding, malaise, loss of appetite B. Laboratory findings i. WBC >25,000 cells/mm 3 ii. Megakaryocytosis, basophilia, eosinophilia iii. May have hyperkalemia, hyperuricemia, increased lactate dehydrogenase C. Bone marrow findings i. Hypercellular (~75-90%), increased erythropoiesis, increased megakaryocytes, minimal dysplasia, blasts <10% VI. Diagnosis 2,5,10 A. Bone marrow aspiration/biopsy i. Can be utilized to confirm the diagnosis of CML ii. Provides additional information regarding hypercellularity and blast and basophil percentages iii. Able to detect chromosomal abnormalities other than the Philadelphia chromosome B. Reverse transcriptase-polymerase chain reaction (RT-PCR) to evaluate BCR-ABL1 transcripts i. Used to detect presence of residual disease while on treatment ii. Can detect for presence (qualitative) or amount (quantitative) of BCR-ABL1 transcripts VII. Risk Stratification 5 A. Risk factors i. Older age ii. Being male iii. Radiation exposure B. Scoring systems used in CML 6-10 i. Provides information regarding prognosis ii. Types Sokal score 1984 Hasford (Euro) score 1998 European Treatment and Outcome Study (EUTOS) score 2011 a. Shown to have stronger prognostic capabilities compared to Sokal score b. Has not been validated yet in a subsequent study iii. Only Sokal and Hasford scores currently recommended for use by National Comprehensive Cancer Network (NCCN) guidelines Pham 4

5 Management Table 2. Prognostic Score Equations 6-10 Study Calculation Risk Definition Exp x (age in years 43.4) + (spleen Low: <0.8 Sokal et al, 7.51) x [(platelet count 700) ] Intermediate: x (blast cells 2.10) High: >1.2 Hasford et al, when age 50 years + (0.042 x spleen) when platelet count > 1500 x 10 9 /L + ( x blast cells) when basophils > 3% + ( x eosinophils) x 100 Low: 780 Intermediate: High: >1480 iv. Categorizing CML as low, moderate, or high risk helps dictate choice of initial TKI used Low risk imatinib Intermediate or high risk dasatinib, nilotinib, bosutinib I. Historical treatment timeline 2,5 A Italian Cooperative Study Group: interferon vs. chemotherapy 11 i. OS: 72 vs. 52, p < ii. Time to progression to AP/BP: 72 vs. 45 (p < 0.001) iii. Patients undergoing allogeneic transplant: 36/322 patients (11%) data censored iv. Patients stopping treatment due to toxic effects: 16% vs. 0% (p<0.001) v. Adverse effects of interferon : a. Usually multiple: Flu-like symptoms (asthenia, fever, headache, arthralgia, myalgia), nausea, anorexia, diarrhea, weight loss b. Stopping treatment: polyneuropathy; a syndrome of confusion, dizziness, drowsiness, and depression B Tyrosine kinase inhibitor therapy i. In 2001, results from the IRIS trial introduced a new era of targeted therapy that has since replaced interferon as the standard treatment for CML 12 ii. TKIs have improved life expectancies, offered a more tolerable adverse effect profile, and precluded the need for allogeneic transplant and its complications such as infections and graft versus host disease iii. Agents a. First generation: imatinib b. Second generation: dasatinib, nilotinib, bosutinib c. Third generation: ponatinib Table 3. First-line TKI Therapy for CP-CML: Long-term follow-up data 10 Trial Study arms No. of patients CCyR MMR IRIS 12 DASISION 13 ENESTnd 14 Imatinib 400 mg IFN- + cytarabine Dasatinib 100 mg Imatinib 400 mg Nilotinib 300 mg Nilotinib 400 mg Imatinib 400 mg Median followup Disease progression n (%) PFS years 83% 38 (7%) 92% 83% (13%) % % 12 (5%) 85% 91% 5 years (p=0.002) % 19 (7%) 86% 90% years % (p<0.0001) 10 (4%) 92% 94% % 6 (2%) 96% 96% (p<0.0001) % 21 (7%) 91% 92% OS Pham 5

6 BFORE 16 Bosutinib % 47% 4 (2%) mg (p=0.0075) (p=0.02) Imatinib 400 mg % 37% 6 (3%) CCyR: complete cytogenetic response; MMR: major molecular response; PFS: progression free survival; OS: overall survival iv. Initial TKI selection for CP-CML is based on risk score, TKI toxicities, age, comorbidities, and ability to tolerate therapy C. Protein synthesis inhibitor therapy: omacetaxine 18 i. Reserved for after failure of 2 or more TKIs ii. Reserved for T315I mutation II. Monitoring Response to TKI Therapy and Mutational Analysis 2,10,19 A. Goals of Therapy i. If in CP remain in CP and prevent progression to AP/BP a. Long life expectancies for patients who remain in CP while on treatment b. Lower life expectancies even if patients in AP/BP are able to achieve CP again ii. If in AP achieve CP and proceed to allogeneic stem cell transplantation a. Prognosis is significantly worse in patients who progress to AP iii. If in BP achieve CP and proceed to allogeneic stem cell transplantation a. Prognosis is significantly worse in patients who progress to BP b. Acquisition of additional genetic mutations such as trisomy 8, isochromosome 17, trisomy 21 and deletion 7 causes CML to progress from CP to either myeloid BP (~2/3 of patients) or lymphoid BP (~1/3 of patients) B. Monitoring Response to TKI Therapy 2,10 i. Types of responses a. Hematologic response: improvement of blood counts and signs/symptoms b. Cytogenetic response: amount of Philadelphia chromosomes in metaphase c. Molecular response: number of BCR-ABL1 transcripts present Table 4. Response Criteria for TKI Therapy 10 Response Type Criteria Normal peripheral blood count WBC <10,000 cells/mm 3 Hematologic Platelets < 450,000 cells/mm 3 No immature cells in the peripheral blood No signs or symptoms of disease Complete (CCyR): 0% Ph+ metaphases Major (MCyR): 0-35% Ph+ metaphases Cytogenetic Partial (PCyR): 1-35% Ph+ metaphases Minor: >35-65% Ph+ metaphases Early: BCR-ABL1 10% at 3 and 6 Major (MMR): BCR-ABL1 <0.1% or 3 log reduction in BCR-ABL1 Molecular mrna from the standardized baseline, if qpcr (IS) is not available Complete (CMR): no detectable BCR-ABL mrna by qpcr (IS) o BCR-ABL % yields a 4.5-log reduction (MR4.5) ii. Tests for monitoring response a. Types of tests Table 5. Tests for Monitoring Response 5,10 Test Recommendation for Monitoring Bone marrow At diagnosis aspiration/ Failure to reach response milestones biopsy Any sign of molecular or cytogenetic relapse RT-qPCR (IS) At diagnosis Pham 6

7 BCR-ABL kinase domain mutation analysis Every 3 after starting treatment. After BCR-ABL1 (IS) between >0.1%-1% is reached, can monitor every 3 for 2 years, then every 3-6 thereafter If there is 1-log increase in BCR-ABL transcript levels with MMR, qpcr should be repeated in 1-3 Chronic phase o Failure to reach response milestones o Any sign of molecular or cytogenetic relapse o 1-log increase in BCR-ABL transcript levels with loss of MMR Disease progression to accelerated or blast phase b. Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) blood test conducted periodically throughout treatment a) Monitors for presence and quantity of BCR-ABL1 transcripts b) Conducted every 3 for two years as long as patient is responding to treatment, followed by every 3-6 thereafter c) Helps determine if early treatment milestones are being achieved iii. Early Treatment Milestones a. Gold standard: Complete cytogenetic response at 12 Table 6. Early Treatment Milestones 10 BCR-ABL1 (IS) >15 >10% Possible TKI resistance TKI resistance >1% - 10% TKI sensitive disease Possible TKI resistance TKI resistance 1 % TKI sensitive disease iv. IRIS trial: 8-year follow-up 20 a. Results a) Event-free survival at 8 years: 81% b) Freedom from progression to AP/BP: 92% b. Take home: a) Patients on long-term imatinib maintain their responses b) Progression to AP/BP occurred early and risk for progression was minimal after year 3 v. Resistance to imatinib? 10,21 a. Evaluate adherence to TKI therapy and screen for drug interactions a) Poor adherence to therapy leads to worse outcomes i. Reasons for non-adherence 1. Intolerable adverse effects 2. High cost Table 7. Cost of Therapy 22 Drug Cost per month (AWP) Cost per year (AWP) Gleevec Imatinib $12, $11, $145, $142, Sprycel $15, $185, Tasigna $16, $196, Bosulif $17, $204, Iclusig $19, $238, Omacetaxine $10, $122, b) Drug-drug interactions i. TKIs are substrates of cytochrome P450 (CYP) enzymes 1. CYP3A4 inducers decreased TKI concentration decreased efficacy and increased potential for relapse Pham 7

8 2. CYP3A4 inhibitors increase TKI concentration increased toxicities which may decrease adherence ii. Consider dose modifications if co-administration cannot be avoided b. Conduct kinase domain mutational analysis in patients who are intolerant to imatinib or in patients who progress to AP/BP a) If resistant mutation(s) present, consider second line treatment with 2 nd generation TKIs which have higher binding affinity for the ABL1 kinase i. Y253H, E255K/V, or F359V/C/I: dasatinib ii. F317L/V/I/C, T315A, or V299L: nilotinib iii. E255K/V, F317L/V/I/C, F359V/C/I, T315A, or Y253H: bosutinib iv. T315I: ponatinib, omacetaxine, allogeneic HS III. Controversy with TKI Discontinuation 24 A. Since the introduction of TKIs, chronic myeloid leukemia has evolved from an incurable and fatal disease to a manageable, chronic illness 2,5 i. Patients receiving long-term TKIs can achieve undetectable molecular BCR-ABL transcript levels ii. Optimal responders to therapy can have life expectancies similar to those of the general population iii. Potential long-term implications on quality of life resulting from lifelong TKI use may cause patients to want to stop their therapy B. Risks of TKI discontinuation include possible progression of leukemia and increased morbidity i. Significant risk for relapse of CML a. Untreated CP-CML can also progress to AP or BP ii. Development of TKI withdrawal syndrome 23 a. Reported in ~25-30% of patients who discontinue their TKI b. Characterized by low-grade, diffuse musculoskeletal pain a) Treated with NSAIDs or steroids b) Resolves with TKI resumption c. Appears within 1-2 following TKI discontinuation and can last up to 6 C. Benefits of TKI discontinuation include improved overall quality of life i. No longer taking medications that cause side effects like fatigue, edema, malaise, etc. ii. Reduced pill burden iii. Decreased medication costs iv. Women of childbearing age may now consider pregnancy following TKI discontinuation a. TKIs can cross through placenta b. Teratogenic toxicities Clinical Question #1 Is it appropriate to stop tyrosine kinase inhibitor therapy in patients who have chronic myeloid leukemia? Table 8. STIM trial 25 Mahon, et al. Lancet Oncol 2010; 11: Study Aim To assess whether imatinib can be discontinued without occurrence of molecular relapse in patients in complete molecular remission while on imatinib Study Design Prospective, multi-center, non-randomized Pham 8

9 Patient Population Inclusion Exclusion Age 18 years old Previous treatment with Diagnosis of CML-CP or CML-AP immunomodulatory agents Ongoing treatment with imatinib for at least 3 except interferon years Treatment for other Sustained complete molecular response for at malignancies least 2 years Previous hematopoietic stem cell transplant Intervention Molecular biology follow-up of BCR-ABL transcripts using quantitative RT-PCR from peripheral blood was performed: o Every month for the first year o Every 2 for the second year o Every three for the third year and beyond Karyotype of bone marrow cells was assessed in all patients to show complete cytogenetic remission before discontinuation of therapy Molecular relapse was defined as positivity in BCR-ABL transcripts in quantitative RT-PCR with a ratio of BCR-ABL to ABL of 10-5 or more o Re-introduction of imatinib was recommended in instances of molecular relapse Outcomes Primary: Molecular relapse-free survival Time to molecular relapse was measured from date of imatinib discontinuation to date of molecular relapse or date of last molecular examination for patients who did not relapse Relapse-free survival was estimated using Kaplan-Meier method Patients who received follow-up for at least 12 after discontinuation were further analyzed to determine potential factors associated with CMR persistence o Patients with factors that were identified by univariate analyses as potential predictive factors were entered into a Cox regression model All patients in molecular relapse were treated again with imatinib 400 mg PO daily Baseline Characteristics Results N=100 patients; 69 patients with minimum 12- follow-up after discontinuation of imatinib Age: years (median 62 years) Low Sokal risk score: 35 (50.7%) Female: 43 (62.3%) Previous therapy with interferon : 34 (49.2%) Imatinib therapy duration 50 : 51 (73.9%) Time to CMR: 2-56 (median 19 ) CMR duration before discontinuation: (median 35.5 ) Outcomes Relapse-free survival was 41% at 12 & 38% at 24 Forty-six patients remained free of molecular relapse at median follow up of 14 o Interim analysis: 39% in CMR (median follow-up 55 ) Potential factors for predicting molecular relapse by multivariate Cox regression model: Hazard ratio (95% CI) p-value Sokal score (low vs. intermediate vs. high) ( ) Imatinib duration (<50 vs. 50 ) ( ) Sex (male vs. female) ( ) Discussion Authors Conclusions Reviewer s Interpretation Imatinib can be safely discontinued in patients who obtain a stable complete molecular remission (CMR) Strengths Limitations Prospective, multicenter study Small sample size Pham 9

10 BCR-ABL1 values by international scale (IS) 31% had follow-up less than 12 Take-Home Points Imatinib discontinuation may be feasible and safe in ~40% patients Patients need to be re-introduced to imatinib therapy after molecular relapse Sokal risk score, gender, imatinib duration may affect prognosis of relapse Abbreviations: CMR: complete molecular response Table 9. STOP 2G-TKI trial 26 Rea, et al. Blood 2017; 129(7): Study Aim To evaluate outcomes of first-line subsequent dasatinib or nilotinib discontinuation in CML patients with long-lasting and deep molecular responses Study Design Prospective, multi-center, observational study Patient Inclusion Population Exclusion Age 18 years old Previous allogeneic hematopoietic Diagnosis of CML-CP or CML-AP stem cell transplant Treated with dasatinib or nilotinib either firstline or after imatinib intolerance, suboptimal History of progression to AP or BP Nonmajor BCR-ABL transcripts response, or resistance CML while on therapy 3 or more years duration on TKI therapy Received chemotherapy or 2 years or more of molecular response 4.5 radiotherapy for other malignancies Failure of prior TKI discontinuation Intervention Molecular biology follow-up of BCR-ABL transcripts using quantitative RT-PCR from peripheral blood was performed: o Every month for the first year o Every 2 for the second year o Every three for the third year and beyond Molecular relapse was defined as loss of MMR on any single test o Re-initiation of previously prescribed TKI was recommended in instances of molecular relapse Bone marrow cytogenetic analyses and BCR-ABL1 kinase domain mutation assessments recommended in patients with BCR-ABL1 1% and those failing to regain MMR after therapy resumption Outcomes Primary: Treatment-free remission (TFR) at 12 TFR was defined as time from second generation TKI discontinuation to date of first major molecular response (MMR) loss or re-initiation of therapy and calculated using Kaplan- Meier method Changes in BCR-ABL transcript levels between date of molecular relapse and date of treatment resumption calculated using Wilcoxon-matched pairs signed rank test Comparison of quantitative variables from 2 independent groups: Mann Whitney U test Two tailed p-values of <0.05 were considered statistically significant Results Baseline Characteristics N=60 patients that completed at least 12 of follow-up after TKI cessation All patients in chronic phase at diagnosis Female: 38/60 (63.3%) Low Sokal score: 32/60 (53.3%) Second line dasatinib or nilotinib as TKI type before discontinuation: 40/60 (66.7%) History of intolerance to imatinib: 39/60 (65%) Median duration of TKI treatment: 76 Pham 10

11 Outcomes Authors Conclusions Reviewer s Interpretation Discussion First-line or subsequent dasatinib or nilotinib can be safely stopped in CML patients with deep and long-lasting molecular responses A suboptimal response or resistance prior to dasatinib or nilotinib is associated with significantly worse treatment-free remission Strengths Limitations Prospective, multicenter study Similar study criteria as previous imatinib discontinuation studies such as MR4.5 and relapse defined as loss of MMR Small sample size Mostly nilotinib/dasatinib for 2 nd line Included patients with history of progression to AP-CML Take-Home Points Dasatinib or nilotinib may be stopped after achieving deep molecular responses Prompt re-introduction of TKI after relapse is important in disease control Resistance or suboptimal response to prior therapy worsens treatment free remission Table 10. EURO-SKI trial 27 Saussele, et al. Lancet Oncol 2018; 19: Study Aim To define precise conditions for TKI discontinuation Study Design Prospective, single-arm, open label, non-randomized Patient Inclusion Population Age 18 years old Confirmed diagnosis of BCR-ABL1 positive CML in chronic phase Receiving first-line or second-line treatment with any TKI or taking a TKI as part of a combination treatment Needed 3 PCR results showing deep molecular response within the year +/- 2 Exclusion Previous allogeneic stem cell transplant Previous TKI treatment failure Active concomitant malignancies Intervention Molecular response was assessed using RT-qPCR Molecular response monitoring was done once monthly during the first 6 after TKI discontinuation, every 6 weeks until month 12, and then every 3 for at least 3 years Patients with confirmed deep molecular response could stop TKI treatment immediately Outcomes Primary: molecular relapse-free survival Secondary: factors affecting MMR maintenance at 6, cost impact of TKI discontinuation Molecular response assessed using RT-PCR and occurred monthly during first 6 after TKI discontinuation, every 6 weeks until month 12, and then every 3 for at least 3 years Pham 11

12 Baseline Characteristics Molecular recurrence defined as loss of MMR corresponding with >0.1% BCR-ABL transcripts Results 821 patients were enrolled in the study Descriptive characteristics available only for 758 patients at time of analysis due to exclusion criteria Characteristic Patients Age at diagnosis, years 52 (41-60) Duration of TKI therapy, years 7.5 ( ) Sokal score Low Intermediate High Hasford/Euro score Low Intermediate High EUTOS score Low High Treatment before TKI Hydroxycarbamide 259/584 (44%) 197/584 (34%) 128/584 (22%) 239/547 (44%) 256/547 (47%) 52/547 (10%) 536/588 (91%) 52/588 (9%) 396 (52%) 273 (36%) First-line TKI: Imatinib 710 (94%) Second-line TKI: Nilotinib Dasatinib 47/116 (41%) 62/116 (53%) Outcomes Outcomes Patients Molecular relapse free survival: % 50% Authors Conclusions Reviewer s Interpretation MMR or better at (62%) Loss of MMR after TKI discontinuation 371/755 (49%) Loss of MMR within 6 297/373 (80%) Discussion If following certain procedures, such as standardized molecular monitoring of BCR-ABL, TKI discontinuation is safe and predictable Strengths Limitations Prospective, multicenter, international study Date of 1 st deep molecular response Largest sample size retrieved retrospectively Less stringent criteria for TKI Only 6% of patients on 2 nd gen. TKI discontinuation Take-Home Points Less deep MR (MR4.0) and loss of MMR are acceptable criteria Sokal and EUTOS risk scores not predictive of keeping MMR Previous IFN α, TKI duration, & DMR duration affects relapse-free survival at 6 IV. NCCN Guideline Recommendations for First TKI Discontinuation 10 A. TKIs may be safely discontinued in select patients B. Outside of a clinical trial, all of the following criteria must be met for TKI discontinuation: i. Age 18 or older ii. CP-CML only. No history of AP- or BP-CML Pham 12

13 Clinical Question #2 iii. On TKI therapy for at least 3 years iv. Prior evidence of quantifiable BCR-ABL1 transcripts v. Stable molecular response (MR4; BCR-ABL1 < 0.01% IS) for 2 years, as documented on at least 4 tests performed at least 3 apart vi. Molecular monitoring monthly for 1 year, then every 6 weeks for the second year, then every 12 weeks thereafter indefinitely vii. Prompt resumption of TKI within 4 weeks of a loss of MMR with molecular monitoring every 4 weeks until MMR is re-established Is it appropriate to stop tyrosine kinase inhibitor therapy in patients who have failed to achieve a treatment-free remission (TFR) after first discontinuation failure? Table 11. RE-STIM Trial 28 Legros, et al. Cancer 2017; 123(22): Study Aim To evaluate TFR after a second TKI discontinuation attempt Study Design Observational, multicenter study Patient Inclusion Population Age 18 years old Confirmed diagnosis of BCR-ABL1 positive CML in CP Failed a first TKI discontinuation attempt, regained deep molecular response with MR4.5, and discontinued TKI again Previously included in trials like STIM, A- STIM, or EURO-SKI Exclusion Previous autologous or allogeneic stem cell transplant Patients with non-major BCR-ABL1 transcripts History of progression to AP-CML or BP-CML Intervention Molecular response was assessed using RT-qPCR Molecular response monitoring was done monthly during the first 12 after TKI discontinuation, every 2-3 during the second year, and then every 3-6 for up to 5 years Outcomes Primary: Treatment-free remission (TFR) Secondary: Lack of progression to advanced phase CML, efficacy of treatment resumption Molecular recurrence defined as loss of MMR corresponding with >0.1% BCR-ABL transcripts Results Baseline Characteristics 70 patients were enrolled in the study Baseline characteristics at second TKI discontinuation: Characteristic Patients Age at diagnosis, years 60 (36-93) Duration of TKI therapy before 2 nd 32 (6.0-72) discontinuation, Duration of umr4.5 before 2 nd 25 (4.0-68) discontinuation, First-line TKI Imatinib 50/70 (71%) Second-line TKI Nilotinib Dasatinib 13/70 (19%) 7/70 (10%) Pham 13

14 Outcomes Outcomes Patients Number of patients that lost an MMR 45 (64%) Median time off therapy () 5.3 ( ) Molecular relapses occurring in first year after TKI discontinuation 54% Authors Conclusions Reviewer s Interpretation TFR probability at: % 48% 42% 35% Same TKI restarted 27 (60%) TKI change due to past tolerance issues: Dasatinib Nilotinib TKI change from 2 nd generation TKI to: Different 2 nd generation TKI Imatinib 5 3 Progression to advanced phase CML 0 (0%) Discussion A second attempt to discontinue TKI therapy in patients who failed a first discontinuation and subsequently regained undetectable MR4.5 after TKI re-challenge is safe Strengths Limitations Prospective, multicenter study Used TFR as treatment goal Same PCR testing frequency as STIM trial Small sample size Only had patients with 1 st line TKI Time to loss of MR4.5 = 3, but time to TKI re-start = 5 Take-Home Points May be feasible if strict MR4.5 requirement met Second discontinuation is more successful in patients who relapse later than 3 during a TKI discontinuation attempt Close and prolonged molecular monitoring is necessary Summary and Recommendations I. Discontinuation of TKI therapy is a potentially feasible and safe option for CML patients II. Achieving a deep molecular response prior to discontinuation of TKI may help achieve longer TFR A. Duration of TKI therapy for at least 3 years B. Stable molecular response (MR4; BCR-ABL1 < 0.01% IS) for at least 2 years III. Continuous molecular monitoring is important in CML A. BCR-ABL transcript levels detected by RT-PCR can fluctuate B. Therefore, routine monitoring is recommended to ensure sustained TFR i. Monthly for one year ii. Every 6 weeks for second year iii. Every 12 weeks indefinitely IV. Prompt resumption of TKI within 4 weeks of loss of MMR with molecular monitoring every 4 weeks until MMR is re-established V. A second TKI discontinuation attempt in patients who have previously failed a first TKI discontinuation attempt may be safe and feasible VI. Future Directions A. Utilizing TFR as an endpoint in future studies and comparing TFR rates between imatinib and second generation TKIs B. Larger, prospective studies evaluating the long-term safety and efficacy of a second TKI discontinuation 5 4 Pham 14

15 References 1. What Is Chronic Myeloid Leukemia? Leukemia Types. American Cancer Society. Accessed December 17, Jabbour E, Kantarjian H. Chronic myeloid leukemia: 2018 update on diagnosis, therapy, and monitoring. American Journal of Hematology. 2018;93: Key Statistics for Chronic Myeloid Leukemia. American Cancer Society. Accessed December 10, Cancer Stat Facts: Leukemia - Chronic Myeloid Leukemia (CML). Acute Myeloid Leukemia - Cancer Stat Facts. Accessed January 6, Thompson PA, Kantarjian HM, Cortes JE. Diagnosis and Treatment of Chronic Myeloid Leukemia in Mayo Clin Proc. 2015;90(10): Hasford J, Baccarani M, Hoffmann V, et al. Predicting complete cytogenetic response and subsequent progression-free survival in 2060 patients with CML on imatinib treatment: the EUTOS score. Blood. 2011;118(3): Marin D, Ibrahim AR, Goldman JM. European Treatment and Outcome Study (EUTOS) Score for Chronic Myeloid Leukemia Still Requires More Confirmation. Journal of Clinical Oncology. 2011;29(29): Jabbour E, Cortes J, Nazha A, et al. EUTOS score is not predictive for survival and outcome in patients with early chronic phase chronic myeloid leukemia treated with tyrosine kinase inhibitors: a single institution experience. Blood. 2012;119(19): Yamamoto E, Fujisawa S, Hagihara M, et al. European Treatment and Outcome Study score does not predict imatinib treatment response and outcome in chronic myeloid leukemia patients. Cancer Science. 2014;105(1): National Comprehensive Cancer Network. Chronic Myeloid Leukemia. V Interferon Alfa-2a as Compared with Conventional Chemotherapy for the Treatment of Chronic Myeloid Leukemia. New England Journal of Medicine. 1994;330(12): Obrien SG, Guilhot F, Larson RA, et al. Imatinib Compared with Interferon and Low-Dose Cytarabine for Newly Diagnosed Chronic-Phase Chronic Myeloid Leukemia. New England Journal of Medicine. 2003;348(11): Kantarjian H, Shah NP, et al. Dasatinib versus Imatinib in Newly Diagnosed Chronic Phase Chronic Myeloid Leukemia. New England Journal of Medicine Jun 17;362(24): Saglio G, Kim DW, et al. Nilotinib versus Imatinib for Newly Diagnosed Chronic Myeloid Leukemia. New England Journal of Medicine Jun 17;362(24): Cortes JE, Kim D-W, Kantarjian HM, et al. Bosutinib Versus Imatinib in Newly Diagnosed Chronic-Phase Chronic Myeloid Leukemia: Results From the BELA Trial. Journal of Clinical Oncology. 2012;30(28): Cortes JE, Gambacorti-Passerini C, et al. Bosutinib Versus Imatinib for Newly Diagnosed Chronic Myeloid Leukemia: Results From the Randomized BFORE Trial. Journal of Clinical Oncology Jan 20;36(3): Cortes JE, Kim DW, et al. A Phase 2 Trial of Ponatinib in Philadelphia Chromosome Positive Leukemias. New England Journal of Medicine. 2013; 369: Cortes JE, Lipton JH, et al. Phase 2 study of subcutaneous omacetaxine mepesuccinate after TKI failure in patients with chronicphase CML with T315I mutation. Blood Sep 27;120(13): Ren R. Mechanisms of BCR-ABL in the pathogenesis of chronic myelogenous leukaemia. Current neurology and neuroscience reports. Published March Accessed January 6, Deininger M, O brien SG, Guilhot F. International randomized study of interferon vs. STI571 (IRIS) 8-year follow up: sustained survival and low risk for progression of events in patients with newly diagnosed chronic myeloid leukemia in chronic phase (CML- CP) treated with imatinib. Blood. 2009; Valent P. Imatinib-resistant chronic myeloid leukemia (CML): Current concepts on pathogenesis and new emerging pharmacologic approaches. Biologics. 2007;1(4): Login. Accessed January 6, Richter J, Söderlund S, Lübking A, et al. Musculoskeletal pain in patients with chronic myeloid leukemia after discontinuation of imatinib: a tyrosine kinase inhibitor withdrawal syndrome?. J Clin Oncol. 2014;32: Saußele S, Richter J, Hochhaus A, Mahon FX. The concept of treatment-free remission in chronic myeloid leukemia. Leukemia. 2016;30(8): Mahon F-X, Réa D, Guilhot J, et al. Discontinuation of imatinib in patients with chronic myeloid leukaemia who have maintained complete molecular remission for at least 2 years: the prospective, multicentre Stop Imatinib (STIM) trial. The Lancet Oncology. 2010;11(11): Rea D, Nicolini FE, Tulliez M, et al. Discontinuation of dasatinib or nilotinib in chronic myeloid leukemia: interim analysis of the STOP 2G-TKI study. Blood. 2016;129(7): Saussele S, Richter J, Guilhot J, et al. Discontinuation of tyrosine kinase inhibitor therapy in chronic myeloid leukaemia (EURO- SKI): a prespecified interim analysis of a prospective, multicentre, non-randomised, trial. The Lancet Oncology. 2018;19(6): Legros L, Nicolini FE, Etienne G, et al. Second tyrosine kinase inhibitor discontinuation attempt in patients with chronic myeloid leukemia. Cancer. 2017;123(22): Pham 15

16 Appendix A: Review of Landmark Trials for Therapies in CML Table 1. IRIS Trial (2001) Imatinib Purpose To compare the efficacy of imatinib with that of interferon alfa plus low dose cytarabine in the treatment of CP- CML Population Inclusion Exclusion years old Diagnosed with Ph+ CP-CML within six of study entry LFTs, total bilirubin, and serum creatinine 1.5x ULN Women who were breastfeeding, pregnant, or child-bearing potential ECOG 3 or higher Presence of other uncontrolled serious medical conditions Received prior chemotherapy or any investigational agent Had undergone hematopoietic stem cell transplant Had undergone major surgery within the preceding 4 weeks Were known to be seropositive for HIV Had a history of cancer within the previous 5 years excluding basal cell carcinoma or cervical carcinoma in situ Design/ Prospective, multi-center, open-label, phase 3, randomized trial; 1106 patients were randomized: 553 pts received imatinib vs. 553 pts received interferon alfa and cytarabine. Results CCyR, 18 mo: 87.1% imatinib vs. 34.7% interferon/cytarabine Conclusion Imatinib superior to interferon alfa plus low-dose cytarabine as 1 st line for newly diagnosed CP-CML Critique Strengths Limitations Prospective, multicenter, open-label randomized phase 3 study Early cross-over of many Large sample size Balanced baseline characteristics Intention to treat patients to imatinib group may cloud differences in survival Imatinib produced better hematologic and cytogenetic responses compared to interferon alpha and cytarabine Take-Home Points Table 2. DASISION Trial (2012) Dasatinib Purpose To compare the efficacy of dasatinib with that of imatinib in the treatment of CP-CML Population Inclusion Exclusion Diagnosed with Ph+ CP-CML within 3 of study entry No previous treatment for CML except for anagrelide or hydroxyurea ECOG 0-2 Total bilirubin 2x ULN AST/ALT 2.5x ULN Serum creatinine 3x ULN Women who were breastfeeding, pregnant, or child-bearing age without negative pregnancy test Serious, uncontrolled medical disorders or infections Uncontrolled or serious cardiovascular disease QTc interval >450 msec History or serious bleeding disorder unrelated to CML Previous or concurrent cancer other than basal-cell skin cancer Previous chemotherapy for peripheral stem-cell mobilization Pleural effusion at baseline Design/ Multinational, open-label, phase 3, randomized trial; 259 pts Dasatinib vs. 260 pts Imatinib Results CCyR, 24 mo: 86% dasatinib vs. 82% imatinib Conclusion Dasatinib shows deeper and faster responses compared to imatinib Critique Strengths Limitations Multinational, open-label randomized, phase 3 study Balanced baseline characteristics Follow-up period not long enough to detect long-term effects Take-Home Points Dasatinib produced a faster and deeper complete cytogenetic response and major molecular response within 12 after initiating therapy compared to imatinib Table 3. ENESTnd Trial (2010) Nilotinib Purpose To compare the efficacy of nilotinib with that of imatinib in the treatment of CP-CML Population Inclusion Exclusion Design/ Diagnosed with Ph+, CP- CML within 6 of study entry ECOG 0-2 Adequate organ function Multinational, open-label, phase 3, randomized trial Previously treated with a TKI before study entry (except imatinib for 2 weeks) or any medical treatment for CML for > 2 weeks (except anagrelide or hydroxyurea) Patients with impaired cardiac function Use of coumadin Drugs that block or stimulate the activity of the liver enzyme cytochrome P450 3A4 or with potential to prolong QTc interval Pham 16

17 282 pts nilotinib 300mg, 281 pts nilotinib 400mg, and 283 pts imatinib Results MMR, 12 mo: 44% nilotinib 300mg, 43% nilotinib 400mg, vs. 22% imatinib (p<0.001) Conclusion Nilotinib either at 300mg or 400mg was superior to imatinib for newly diagnosed CP-CML Critique Strengths Limitations Take-Home Points Multicenter, open-label randomized, phase 3 study Balanced baseline characteristics Did not review complete cytogenetic response as a primary endpoint Follow-up period not long enough to detect durability of responses Nilotinib produced significantly better major molecular responses and complete cytogenetic responses compared to imatinib Table 4. BELA Trial (2012) Bosutinib Purpose To compare the efficacy of bosutinib with that of imatinib in the treatment of CP-CML Population Inclusion Exclusion Design/ Adults diagnosed with Ph+, CP-CML within 6 of study entry Total bilirubin 2x ULN; AST/ALT 2.5x ULN Serum creatinine 1.5x ULN ECOG 0-1 Phase 3, randomized trial Previous treatment received for leukemia (except anagrelide or hydroxyurea) Prior stem cell transplant CNS leukemia Extramedullary disease only History of accelerated or blast phase CML Major surgery or radiotherapy within 14 days of randomization Use of medications that prolong QTc interval History of uncontrolled heart disease Prolonged QTc interval History of another malignancy except basal-cell carcinoma in past 5 years Congenital or acquired cytopenias 250 pts bosutinib 500mg vs. 252 pts imatinib Results CCyR, 12 mo: 70% bosutinib vs. 68% imatinib (p=0.601); MMR, 12 mo: 41% bosutinib vs. 27% imatinib (p<0.001) Conclusion The primary endpoint of CCyR was not met and not significantly different between bosutinib and imatinib Critique Strengths Limitations Take-Home Points Multicenter, open-label Did not review complete cytogenetic response as a primary endpoint randomized, phase 3 study Follow-up period not long enough to detect durability of responses Balanced baseline characteristics Early discontinuation of bosutinib due to toxicities Intention to treat Bosutinib 500 mg did not demonstrate superior complete cytogenetic response at 12 compared to imatinib Table 5. BFORE Trial (2018) Bosutinib Purpose To compare the efficacy of bosutinib with that of imatinib in the treatment of CP-CML Population Inclusion Exclusion Design/ Adults diagnosed with Ph+, CP- CML within 6 of study entry Total bilirubin 2x ULN AST/ALT 2.5x ULN Serum creatinine 1.5x ULN ECOG 0-1 Open-label, phase 3, randomized trial 268 pts bosutinib 400mg vs. 268 pts imatinib Previous treatment received for leukemia (except anagrelide or hydroxyurea) Past CNS involvement Extramedullary disease only Major surgery or radiotherapy within 14 days of randomization Use of medications that prolong QTc interval History of uncontrolled heart disease Known seropositivity to HIV, acute or chonic hepatitis B or C, cirrhosis Recent or ongoing GI disorder History of another malignancy except basal-cell carcinoma or cervical carcinoma in situ in past 5 years Uncontrolled hypomagnesemia or uncorrected hypokalemia Current or recent participation in clinical trials of investigational agents Women who were breastfeeding, pregnant, or child-bearing age without negative pregnancy test Pham 17

18 Results MMR, 12 mo: 47.2% bosutinib vs. 36.9% imatinib (p=0.02) CCyR, 12 mo: 77.2% bosutinib vs. 66.4% imatinib (p=0.0075) Conclusion Patients who received bosutinib had significantly better and faster results than imatinib Critique Strengths Limitations Multinational, open-label randomized, phase 3 study Balanced baseline characteristics Intention to treat Take-Home Points Did not review complete cytogenetic response as a primary endpoint Follow-up period not long enough to detect durability of responses Bosutinib had significantly higher rates of major molecular response and complete cytogenetic response and achieved faster responses than those who received imatinib This difference in result was seen with bosutinib 400 mg compared to the 500 mg dose that was used in the BELA trial Table 6. PACE Trial (2013) - Ponatinib Purpose To compare the efficacy of ponatinib with that of imatinib in the treatment of CP-CML Population Inclusion Exclusion Adults diagnosed with CML in Received TKI in previous 7 days any phase or Ph+ ALL For CP or AP, received hydroxyurea or anagrelide within 24 hrs of Previously treated with dasatinib receiving ponatinib or nilotinib For BP, received chemotherapy within 14 days prior to first dose of Developed the T315I mutation ponatinib after any TKI therapy For Ph+ ALL patients, received corticosteroids within 24 hrs prior to ECOG 0-2 first dose ponatinib Total bilirubin 1.5x ULN Previous stem cell transplant with past 60 days AST/ALT 2.5x ULN Use of medications that prolong QTc interval Prothrombin time 1.5x ULN Require treatment with immunosuppressive agents other than Lipase 1.5x ULN corticosteroids Amylase 1.5x ULN Have active CNS disease Serum creatinine 1.5x ULN Significant cardiovascular disease QTc 450 msec in males and <470 History of significant bleeding msec in females History of pancreatitis or alcohol abuse Subjects of child-bearing age must Triglycerides 450 mg/dl agree to use effective History of GI or malabsorption syndrome contraception Women who were breastfeeding, pregnant, or child-bearing age without negative pregnancy test Major surgery in past 14 days Known seropositivity to HIV, acute or chronic hepatitis B or C, Design/ cirrhosis Multinational, multicenter, open-label Phase 2 trial 449 pts with CML, Ph+ ALL with resistance to dasatinib or nilotinib, or pts with BCR-ABL T315I mutation treated with ponatinib 45mg PO daily and followed at 15 Results Hematologic response lasting >8 weeks: 67% of pts MCyR: 22% of pts Conclusion Ponatinib had activity against CML across various stages of disease and mutational status Critique Strengths Limitations Multinational, multicenter, open-label Unbalanced baseline characteristics between groups phase 2 study Follow-up period not long enough to detect durability of responses Relevant primary endpoint with Included patients previously treated with cytarabine and interferon complete cytogenetic response alpha Take-Home Points Ponatinib was associated with antileukemic activity in heavily pre-treated patients with CML Pham 18

19 Table 7. Omacetaxine Trial (2013) Purpose To evaluate the efficacy and safety of subcutaneous omacetaxine in CML patients with resistance or intolerance to two or more TKIs Population Inclusion Exclusion Design/ Results Adults diagnosed with Ph+, CP-CML within 6 of study entry Multicenter, noncomparative, open-label phase 2 trial NYHA Class III or IV heart disease, active ischemia, or any other uncontrolled heart condition Active malignancy other than CML Uncontrolled active infection HIV positive status Patients eligible for stem cell transplant at time of screening Patients in lymphoid blast crisis 46 pts enrolled with CP-CML, with 85% having received treatment with 2 or more TKIs, treated with omacetaxine induction (1.25 mg/m2 SQ bid x14 days, q28d) and maintenance (1.25 mg/m2 SQ x7 days, q28d for up to 24 ) Hematologic response lasting >8 weeks: 67% of pts MCyR: 22% of pts Conclusion Omacetaxine can produce clinically meaningful hematologic and cytogenetic responses with an acceptable safety profile for pts with CP-CML who have previously failed multiple TKIs Critique Strengths Limitations Take-Home Points Prospective, multicenter, single arm, open-label phase 2 study Intention to treat No comparator Small sample size Included patients previously treated with cytarabine and interferon alpha There is a favorable risk-benefit profile in patients with T315I mutation who have failed prior TKI therapy Appendix B: Summary of TKI Discontinuation Trials Study Treatment prior to discontinuation No. of patients Depth and duration of MR required for discontinuation Trigger to resume TKI therapy Median followup Treatment-free remission rate STIM1 Imatinib ± interferon 100 MR5.0 for at least 2 years Loss of MR % at 60 TWISTER Imatinib ± interferon 40 MR4.5 for at least 2 years Loss of MR % at 24 HOVON Imatinib + cytarabine 15 MR4.5 for at least 2 years Loss of MR % at 24 A-STIM Imatinib ± interferon 80 MR5.0 for at least 2 years Loss of MMR 31 61% at 36 ISAV study Imatinib (after failure of 108 CMR for at least 18 Loss of MMR 36 52% at 96 interferon or hydroxyurea) KID study Imatinib ± interferon 90 MR4.5 for at least 2 years Loss of MMR 27 59% at 24 Stop 2G-TKI Dasatinib/nilotinib (1 st or 2 nd line) 60 MR4.5 for at least 24 Loss of MMR 47 54% at 48 ENESTFreedom Nilotinib (1 st line) 190 MR4.5 for at least 12 Loss of MMR 96 49% at 96 weeks ENEStop study Nilotinib (2 nd line) 126 MR4.5 for at least 12 Loss of MMR 96 53% at 96 weeks DADI Dasatinib (2 nd line) 63 MR4.0 for at least 12 Loss of MR % at 36 EURO-SKI Any TKI 758 MR4.0 for at least 1 year Loss of MMR 27 50% at 24 Pham 19

20 Appendix C: Overview of therapies for CML Table 1. Overview of Therapies for CML FDA Approval MOA Dose Adverse Effects Notes Imatinib (Gleevec ) Dasatinib (Sprycel ) Nilotinib (Tasigna ) Bosutinib (Bosulif ) Ponatinib (Iclusig ) May 10, 2001 June 28, 2006 October 29, 2007 September 4, 2012 December 14, 2012 Inhibits BCR- ABL tyrosine kinase, inducing apoptosis; also inhibits PDGF, c-kit CP AP, BP 400 mg PO daily mg PO daily Edema, fatigue, skin rash, nausea, diarrhea, vomiting, muscle cramps Inhibits most BCR-ABL tyrosine kinase mutations that are resistant to imatinib (except T315I and F317V), inducing apoptosis; also inhibits SRC family, c-kit, EPHA2, and PDGF 100 mg PO daily 140 mg PO daily Fluid retention, pleural effusions, diarrhea, thrombocytopenia, neutropenia, anemia Inhibits most BCR-ABL tyrosine kinase mutations that are resistant to imatinib (except T315I and F317V), inducing apoptosis; also inhibits c-kit, EPHA2, and PDGF, but not SRC family 300 mg PO twice daily (400 mg if resistant) 400 mg PO twice daily Hyperglycemia, skin rash, nausea, QTc interval prolongation, occlusive arterial disease, arthralgia Take on empty stomach Inhibits most BCR- ABL tyrosine kinase mutations that are resistant to imatinib (except T315I and V229L), inducing apoptosis; also inhibits SRC family; minimal activity on c-kit and PDGF 400 mg PO once daily 500 mg PO once daily Diarrhea, nausea, vomiting, hyperphosphatemia, skin rash, fatigue, headache, cytopenias, fever Inhibits most BCR-ABL tyrosine kinase mutations that are resistant to imatinib, inducing apoptosis; also inhibits SRC family, c-kit, EPHA2, and PDGF 45 mg PO once daily Arterial occlusions, heart failure, hepatotoxicity, VTE, hypertension, arterial ischemia, skin rash, constipation, cytopenias Dose adjustment for CYP 3A inhibitors Omacetaxine (Synribo ) October 26, 2012 Reversibly binds to the A-site cleft of the ribosomal subunit to interfere with chain elongation and inhibit protein synthesis; Acts independently of BCR-ABL1 tyrosine kinase activity Induction: 1.25 mg/m 2 SQ twice daily x 14 days of a 28-day cycle; maintenance: 1.25 mg/m 2 SQ twice daily x 7 days of a 28-day cycle Thrombocytopenia, neutropenia, infection, increased uric acid, diarrhea, nausea, abdominal pain, fever, injection site reaction, fatigue, weakness, alopecia Pham 20