Chronic Myeloid Leukemia Amer Rassam, M.D.

Learning Objectives Myeloproliferative disorders (MPDs) Molecular genetics of chronic myeloid leukemia Clinical manifestations and diagnosis of chronic myeloid leukemia Overview of the treatment of chronic myeloid leukemia Initial treatment of chronic myeloid leukemia in chronic phase

Learning Objectives Explain how to define and identify a relapse Treatment of CML in chronic phase after failure of initial therapy Clinical use of tyrosine kinase inhibitors for chronic myeloid leukemia Treatment of CML in accelerated phase and blast crisis Prognosis

Myeloproliferative Disorders Chronic Myeloid Leukemia (CML) Polycythemia Vera (PCV) Essential Thrombocythemia (ET) Primary Myelofibrosis (PMF)

Myeloproliferative Disorders Clonal disorders of hematopoiesis that arise in hematopoietic stem or early progenitor cell. Characterized by the dysregulated production of particular lineage of mature myeloid cells with fairly normal maturation. Exhibit a variable tendency to progress to acute leukemia Share abnormalities of hemostasis and thrombosis Overlap between the clinical features

Introduction CML is a clonal myeloproliferative neoplasm Dysregulated production and uncontrolled proliferation of mature and maturing granulocyte with fairly normal differentiation Fusion of 2 genes: BCR (or chromosome 22) and ABL1 (on chromosome 9), resulting in BCR-ABL1 fusion gene Final result: Abnormal chromosome 22 called Philadelphia (Ph) chromosome Final product: BCR-ABL1 fusion protein, a dysregulated tyrosine kinase

Introduction Uncontrolled production of mature and maturing granulocytes Predominantly neutrophils, but also basophils and eosinophils Triphasic or biphasic clinical course Chronic phase, accelerated phase, blast crisis

Phases of CML (before Imatinib) Advanced phases Chronic phase Median duration 5–6 years Accelerated phase Median duration 6–9 months Blast crisis Median survival 3–6 months

Epidemiology Annual incidence: 1 to 2 cases per 100,000 15% – 20% of all adult leukemias Incidence increases significantly with age Median age: ~ 55 years Prevalence increasing due to current therapy Most patients present in CP, 85% Majority of CML-related deaths due to progression to AP/BC 50% of CML patients are asymptomatic at diagnosis Risk factors Exposure to ionizing radiation, the only known

Molecular Genetics of CML The Philadelphia chromosome was originally detected by workers in Philadelphia. The first genetic abnormality to be associated with a human cancer. The result of a balanced translocation between chromosomes 9 and 22. Derivative chromosome 22 is significantly smaller Ph chromosome is present in hematopoietic cells from patients with CML. Therefore, the Ph chromosome is acquired and NOT inherited through the germline.

Molecular Genetics of CML The development of chronic phase CML appears to be a direct result of the BCR-ABL1 activity, which promotes its development by allowing: Uncontrolled proliferation of transformed cells Discordant maturation Escape from apoptosis Altered interaction with the cellular Matrix The progression of CML from chronic phase to accelerated face or blast crisis is a complex, multistep process (may be related to GMP). Also, it appears to involve the constitutive expression of the BCR-ABL1 tyrosine kinase.

Molecular Genetics of CML BCR ABL BCR ABL { q11 BCR Ph 22 { q34 ABL 9q+ 9

Ph chromosome and bcr-abl gene 9 q+ 9 c-bcr 1 2-11 c-abl Ph (or 22q-) 22 2-11 p210Bcr-Abl bcr 2-11 p190Bcr-Abl bcr-abl Exons Introns CML Breakpoints ALL Breakpoints abl FUSION PROTEIN WITH TYROSINE KINASE ACTIVITY bcr-abl gene structure t(9;22) translocation

Philadelphia chromosome t(9;22)(q34;q11) 22q- = Philadelphia chromosome

Clinical Manifestations Asymptomatic in 20-50% of patients Fatigue 34%, weight loss 20%, excessive sweating 15%, abdominal fullness 15%, bleeding episodes 21% (platelet dysfunction). Abdominal pain in the LUQ (enlarged spleen) Tenderness over the lower sternum. Acute gouty arthritis Findings: Splenomegaly, anemia, WBC > 100,000, platelet count > 600,000

Peripheral Blood Pathology Leukocytosis (median of 100,000) Differentiation shows virtually all cells of neutrophilic series Blasts < 2% Myelocytes more than metamyelocytes (a classic finding in CML) Neutrophils cytochemistry is abnormal – low LAP score Basophilia in 90% of cases Thrombocytosis. If low platelets – consider an other

CML Peripheral Blood Smear

CML Peripheral Blood Smear

Bone Marrow Pathology Granulocytic maturation pattern same as in the peripheral blood Increased reticulin fibrosis and vascularity Erythroid islands are reduced in number and size Dwarf megakaryocytes Pseudo-Gaucher’s cells and Sea Blue histiocytes (markers of increased cell turnover) Iron-laden macrophages are reduced or absent

Pseudo-Gaucher cells

Pseudo-Gaucher cells

Sea Blue Histiocyctes

CML – Bone Marrow

Diagnosis of CML Typical findings in the blood and bone marrow Requires the detection of the Ph chromosomal or its product, the BCR-ABL1 fusion mRNA and the BCR-ABL1 protein. Conventional cytogenetic analysis (karyotyping) – The first method Florence and in situ hybridization (FISH) analysis RT-PCR (The BEST) Southern blot techniques – rarely used Western Blotting – low sensitivity and labor intensive

BCR-ABL (FISH)

Cycle 1 yields 2 molecules Cycle 2 yields 4 molecules RT-PCR for BCR-ABL Qualitative RT-PCR allow for the diagnosis of CML Quantitative RT-PCR is used to quantify the amount of disease Allows for the identification of cryptic BCR-ABL translocations Does not require a bone marrow aspirate for optimal results Target sequence 1 Denaturation: Heat briefly to separate DNA strands 2 Annealing: Cool to allow primers to form hydrogen bond with ends of target sequence Cycle 1 yields 2 molecules Primers 3 Extension: DNA polymerase adds nucleotides to the 3” end of each primer New nucleo-tides Cycle 2 yields 4 molecules Cycle 3 yields 8 molecules; 2 molecules (in white boxes) match target sequence

Most CML patients are diagnosed in the chronic phase Blastic phase

Differential Diagnosis Leukemoid reaction Juvenile myelomonocytic leukemia (JMML) Chronic myelomonocytic leukemia (CMML) Atypical CML Chronic eosinophilic leukemia Chronic neutrophilic leukemia Other myeloproliferative neoplasms Other Ph chromosome positive malignancies

Accelerated Phase CML 10-19% blasts in the peripheral blood or bone marrow Peripheral blood basophils ≥20% Platelets < 100,000/microL, unrelated to therapy Platelets > 1,000,000/microL, unresponsive to therapy Progressive splenomegaly and increasing WBC, unresponsive to therapy Cytogenic evolution

Blastic Phase CML Blast crisis is generally refractory to treatment, occurs approximately 3-5 years after the diagnosis of CML and 18 months after the onset of accelerated face Blasts in the peripheral blood ≥20% or in the bone marrow ≥30% Large foci or clusters of blasts on the bone marrow biopsy Presence of extramedullary blastic infiltrate (e.g., myeloid sarcoma, also known as granulocytic sarcoma or chloroma)

Blast Phase CML – Bone Marrow

Blast Phase CML – Bone Marrow

What is the optimal frontline therapy for CML? Clinical Debate What is the optimal frontline therapy for CML?

Principles of CML treatment Relieve symptoms of hyperleukocytosis, splenomegaly and thrombocytosis. Hydration Chemotherapy (Busulfan, hydroxyurea) Control and prolonging the chronic phase (non-curative) Tyrosine kinase inhibitors Alpha-interferon + chemotherapy Chemotherapy (hydroxyurea)

Treatment Options Treatment decisions for patients with CML are complex, due to the variety of available options, many of which are conflicting. Potential cure with allogeneic hematopoietic stem cell transplantation Disease control without cure using tyrosine kinase inhibitors (TKIs) Palliative therapy with cytotoxic agents

Factors influencing choice of therapy Phase of CML Availability of a donor for allogeneic stem cell transplant Patient age Presence of medical co-morbidities Response to treatment with TKIs

IRIS Study Design: Imatinib Mesylate Versus IFN- + ara-C 1106 patients enrolled from June 2000 to January 2001 Imatinib Mesylate IF: · Loss of MCR or CHR · Increasing WBC count S R Crossover · Intolerance of treatment · Failure to achieve MCR at 12 months* · Failure to achieve CHR at 12 months* · Request to discontinue IFN-* IFN- a + ara-C Progression · Increasing WBC count S = screening. R = randomization. · Loss of MCR or CHR · Accelerated phase or blast crisis · Death

Hematologic Responses 100 96% 90 Imatinib mesylate 80 70 60 67% % Responding 50 IFN- + ara-C 40 30 20 10 3 6 9 12 15 18 21 Months Since Randomization

Cytogenic Responses 100 90 83% 80 Imatinib mesylate 70 60 % Responding 50 40 30 20% 20 IFN- + ara-C 10 3 6 9 12 15 18 21 Months Since Randomization

Overall Survival on First-Line Imatinib (IRIS Study)

Resistance to Imatinib occurs predominantly during advanced phase CML Chronic Phase Blast Crisis Advanced stage cancers are characterized by multiple genetic changes Patients in advanced phase often relapse with the development of chemotherapy resistance Some patients in blast crisis CML respond to Imatinib but then tends to relapse Relapse Hematopoietic differentiation Bone marrow to peripheral blood Ph-negative Ph+ blasts Ph+ Ph+ Imatinib mesylate- resistant blasts

Initial Treatment Imatinib (Gleevec) Dasatinib (Sprycel) Tyrosine kinase inhibitors are for first-line therapy in chronic phase CML Imatinib (Gleevec) Dasatinib (Sprycel) Nilotinib (Tasigna) All 3 agents are considered to be (category 1) based on the NCCN guidelines and recommendations. Second-generation TKIs (dasatinib or nilotinib) produce faster and deeper response than imatinib

Treatment of CML after failure of initial therapy No randomized trials have directly compared the efficacy of second-generation TKIs in patients with chronic phase CML who experience failure of an initial TKIs A trial of another TKI. Dasatinib preferred in patients with pancreatitis, elevated bilirubin or hyperglycemia Dasatinib crosses the blood brain barrier and would therefore be preferred in patients with CNS involvement Nilotinib might be chosen for patients with a history of pleural or pericardial effusion or disease Dasatinib and Nilotinib can result in QT prolongation

Other Options Bosutinib – toxicity is a limiting factor Ponatinib – toxicity is a limiting factor Increase the dose of Imatinib Omacetaxine mepesuccinate – SQ Injection Approved by the FDA for patients resistant or intolerant to 2 or more TKIs Hematopoietic cell transplant – the only cure Clinical trials

Other Options Interferon alfa plus cytarabine Hydroxyurea Busulfan Patients who are ineligible for HCT but have either a contraindication to a second-generation TKI or have failed to respond to treatment with available TKI Interferon alfa plus cytarabine Hydroxyurea Busulfan

Response Criteria Hematologic response Cytogenic response Molecular response

Resistance to treatment Primary resistance – patient fails to achieve a desired response to initial treatment Secondary resistance – patient with an initial response to a TKI ultimately relapses

Loss of Response T315I mutation Y253H, E255k/V and F359V/C/I mutations Patients should be re-evaluated with a bone marrow biopsy with cytogenetics, and BCR-ABL kinase mutation analysis T315I mutation Resistant to all TKIs, except Ponatinib Patient should be evaluated for SCT Y253H, E255k/V and F359V/C/I mutations Resistant to Imatinib and Nilotinib but sensitive to Dasatinib F317L/V/I/C, V299L and T315A mutations Sensitive to Nilotinib but with intermediate sensitivity to Imatinib and Dasatinib

Mechanisms of action TKIs They block the initiation of bcr-abl pathway Many TKIs also affect other signaling pathways Dasatinib and Bosutinib inhibit both Bcr-Abl and Src kinases. Nilotinib inhibits Bcr-Abl, c-kit and platelet derived growth factor receptor (PDGFR) These differences in targeted pathways may be responsible for their varied clinical effects in tumors

Mechanisms of Action, Imatinib Competitively inhibits the inactive configuration of the Bcr-Abl protein tyrosine kinase Blocking the ATP binding site and thereby preventing a conformational switch to the active form Inhibits cellular proliferation and tumor formation Produces 95% decrease in CML colony growth Inhibits platelet-derived growth factor and c-kit

GLEEVEC (Imatinib)

GLEEVEC (Imatinib) Molecular consequence of the t(9;22) is the fusion protein BCR–ABL, which has increased in tyrosine kinase activity BCR-ABL protein transform hematopoietic cells so that their growth and survival become independent of cytokines It protects hematopoietic cells from programmed cell death (apoptosis)

TASIGNA (Nilotinib)

Drug Interaction with TKIs They are metabolized by the CYP3A4 system – can inhibit other cytochrome P450 pathways Therefore, they compete with Coumadin Low TKIs levels – St. John’s wort, rifampin, carbamazepine, phenobarbital and phenytoin High TKIs levels – diltiazem, verapamil, itraconazole, ketoconazole, clarithromycin, erythromycin and grapefruit juice

Side Effects of TKIs Imatinib - Bone marrow suppression; fluid retention/edema; gastrointestinal effects; heart failure; hepatotoxicity Dasatinib - Bone marrow suppression; pleural/pericardial effusions; pulmonary arterial hypertension; QT prolongation; aspirin like effect Bosutinib - Bone marrow suppression; fluid retention/edema; gastrointestinal effects

Side Effects of TKIs Nilotinib - Bone marrow suppression; atherosclerosis-related events; electrolyte imbalance; hepatotoxicity Black box: QT prolongation (screening required) Ponatinib - Bone marrow suppression; fluid retention/edema; gastrointestinal effects; heart failure; hypertension; pancreatitis; aspirin-like effect Black box: Arterial thrombosis; hepatic toxicity

Pregnancy and TKIs All TKIs could be teratogenic during pregnancy Women are advised not to become pregnant while on TKIs (any TKI) Best effective contraception is the barrier Woman taking TKIs are advised to avoid to breast-feeding

Prognosis Improved dramatically since the incorporation of tyrosine kinase inhibitors into the initial treatment SEER database. 5138 patient’s, year 2000 and 2005 15-44 years – OS 72 versus 86% 45-64 years – OS 68 versus 76% 65-74 years – OS 38 versus 51% 75-84 years – OS 19 versus 36% Stage of disease at the time of diagnosis is the strongest single predictor of outcome.

www.tallahasseecancer.com

www.tallahasseecancer.com