1

Management of CML patients treated with TKI:

the place of molecular monitoring

Antwerp, December 13th 2011

C. Graux

CHU Mont-Godinne

MolecularDiagnostic.be

Third Scientific Meeting Molecular Diagnostics.be

CML: definition

t(9;22)

CML epidemiology

• CML accounts for 14% of all leukemias

• The incidence is 1.6 per 100.000 /year

+/- 200 new cases/ year in Belgium

1 CML = 2 AML = 3 MM = 12 NHL = 37 CLL

Increases with age (median 67 y)

• Male predominance : 1.4/1

• The only known risk factor is ionizing radiations (high doses)

Exposure to atomic bomb in Nagasaki and Hiroshima induced CML

• Symptoms

- Fatigue, anorexia, weight loss

• Clinical examination

- Splenomegaly

• Biology

- Hyperleucocytosis

- Circulating bone marrow myeloid precursors (left shift)

- Increased basophilia

- Thrombocytosis

• Cytogenetics : t(9;22) = Philadelphia (Ph) chromosome

• Molecular biology: BCR-ABL1

CML diagnosis

Normal Chronic phase of CML

CML: peripheral blood smear Cytogenetic abnormality of CML

1 2 3 4 5

6 7 8 10 119 12

13 14 15 16 17 18

19 20 21 22 x Y

Ph chromosome

2

Ph chromosome and BCR-ABL1 gene

BCR-ABL1

ABL1

Chimeric protein

with tyrosinekinase activity

22

BCR

Ph (or 22q-)

9 9 q+

P210 BCR-ABL1

P190 BCR-ABL1

Chromosome 9

BCR

Chromosome 22

ABL1

Exons

Introns

CML Breakpoints

ALL Breakpoint

t(9;22) translocation BCR-ABL1 gene structure

BCR-ABL1: types of transcripts

m-bcr≈ 55 kd

M-bcr≈ 2,9 kb

µ-bcr

1a

1b

a3

a2

Multiplex-PCR for BCR-ABL1 transcripts

BCR

BCR-ABL1

Constitutively activated tyrosine kinase

Bcr-Abl1 signal transduction pathways

Adapted from Pasternak G et al. J Cancer Res Clin Oncol. 1998;124:643-660

BCR-ABL1

BCL-2MYC

GRB2 CRKL CBL (p120CBL)

RAS

RAF-MEK-MAPK cascade

JAK/STATs

Paxillin

PI3 kinase

Actin

DNA repair

AKT

Regulates cell cycle progression and differentiation Inhibition of apoptosis

Adhesion

Adhesion

Clinical evolution : CML phases

Chronic phase

Variable

Accelerated phase

Median time

6–9 months

Blastic crisis

Median survival

3–6 months

Advanced phases

3

What are the therapeutic goals in CML?

Disappearance of the symptoms

Modify the natural evolution of the disease � blastic phase

Cure

Criteria for response to R/

Hematologic response

Complete

- Platelet count < 450 x 109/L

- WBC count < 10 x 109/L

- Differential: no immature granulocyte

- Basophils < 5%

- Non palpable spleen

Cytogenetic response

Complete (CCgR) = No Ph+ metaphases

Partial (PCgR) = 1-35% Ph+ metaphases

Minor = 36-65% Ph+ metaphases

Minimal = 66-95% Ph+ metaphases

None = > 95% Ph+ metaphases

Molecular response

Allogeneic SCT

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Survival by disease stage, June 2001, based on transplants 1987 – Feb 2001.

P P = .0001= .0001

The only known cure but is associated with high

morbidity and mortality rates in CML

Interferon α

Guilhot F et al. N Engl J Med. 1997;337:223-229.

0.0 12 24 36 48 60

Major cytogenetic responseP

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Minor or no response

P < .001

Months after treatment with IFN-αααα

0.9

0.8

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0.5

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Chemotherapy

• Oral cytotoxic agents

– Hydroxyurea

– Busulfan

• Hematological responses in up to 90% of patients

• Major cytogenetic responses are rare (1%–5%)1-4

• Palliative care: no effect on disease progression

1. The Italian Cooperative Study Group on Chronic Myeloid Leukemia. N Engl J Med. 1994;330:820-825.2. Hehlmann R et al. Blood. 1994;84:4064-4077.3. Allan NC et al. Lancet. 1995;345:1392-1397.4. Ohnishi K et al. Blood. 1995;86:906-916.

BCR-ABL1: the ideal target for

molecular therapy

• Present in the majority of patients with CML (95%)

• The cause of the disease

• Necessary for the initiation of the disease (primary event)

• ABL1 is non essential for normal cellular functions

- Abl1 neg mice are viable

� Imatinib targets BCR-ABL1

4

Mechanism of action of Imatinib

Goldman JM, Melo JV. N Engl J Med. 344 :1084-1086

IRIS Study

S

Imatinib

IFN-a + Ara-C

R Cross-over

IF:· Loss of MCyR or CHR· Increasing WBC count

· Intolerance of treatment· Failure to achieve MCyR

Progression· Death· Accelerated phase or blast crisis· Loss of MCR or CHR· Increasing WBC count

S = screeningR = randomisation

Imatinib versus IFN-α + Ara-C1106 patients enrolled from June 2000 to January 2001

Complete hematological responses

94%

55%

Imatinib

IFN-αααα + Ara-C0

10

20

30

40

50

60

70

80

90

100

Months Since Randomisation

0 3 6 9 12 15 18 21

% R

esp

on

din

g

Major cytogenetic responses

Imatinib

IFN-αααα + Ara-C0

10

20

30

40

50

60

70

80

90

100

Months Since Randomisation

0 3 6 9 12 15 18 21

% R

esp

on

din

g

83%

20%

Superiority of Imatinib to IFN-α + Ara-C

IRIS Study : Summary of the 12-Month Data

CHR = complete haematological response; MCR = major cytogenetic response; PD = progressive disease; AP = accelerated phase; BC = blast crisis.

94

55

83

20

1,58,7

0,7

23

0

20

40

60

80

100

CHR MCyR PD to AP/BC Intolerance

Imatinib

IFN- + Ara-Cαααα

Baccarani, M. et al. Blood 2006;108:1809-1820

Is CCyR the best surrogate endpoint?

5

Progression to AP/BP

IRIS study

Towards cure under TKI?

Is MMR the best surrogate endpoint?

• No proven effect on survival…

• Variability of the assay…

• Data on benefit of MMR based on good responders…

But …

– MMR = very low progression rate

– Loss of MMR signals relapse/progression

– Early MMR predicts complete molecular response � cure?

– MMR underscores the basic oncology principle that less disease is better

� Less is probably more

Molecular monitoring: difficulties

• RQ-PCR is technically challenging

• Issues concerning comparability of results between centres

� International standardisation of molecular monitoring for

CML to enable testing laboratories to accurately mesure key

therapeutic molecular milestones in CML (MMR and CMR)

International scale for BCR-ABL1

• Historically (IRIS trial; 2000), the mean BCR-ABL1 levels of 30

CML patients was defined as 100% in each of the three

participating laboratories using BCR as a control

• The value corresponding to MMR in each laboratory has been

defined as 0,1% (reduction of 3 log from IRIS baseline)

• International Scale (IS) fixed to these key points

MMR is defined as ≤ 0,1%IS = - 3 log reduction of BCR-ABL1 from IRIS standardised baseline , NOT 3 log reduction from individual pretreatment levels

The absolute and not the relative amount is important

International scale for BCR-ABL1

6

Second generation TKI

• Nilotinib vs. Imatinib in CML-CP (ENESTnd Trial, NEJM 2010, Lancet, 2011)

– More frequent and faster MMR

– Decreased progression to accelerated or blastic phase

– More frequent CMR � room for cure?

• Dasatinib vs. Imatinib in CML-CP (NEJM 2010)

– More CCyR

– More frequent and faster MMR

Effect on long term outcome?

Nilotinib vs. Imatinib in CML-CP (ENESTnd Trial)

BCR-ABL1 kinase domain mutants

• Are associated with various degrees of TKI insensitivity

• Select resistant clones = most important mechanism of

resistance

• Can precede or accompany progression to advanced-phase

disease

� KD mutations above a certain level should be identified as

early as possible to reconsider the therapeutic strategyMartinelli. The Hematology Journal, 2005

≅≅≅≅ 90 KD mutations known to date

BCR-ABL1 kinase domain mutants

0

500

1000

1500

2000

2500

3000

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53H

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55D

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55K

E2

55V

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75K

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K2

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IC50

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Gleevec

AMN107

Activity of Nilotinib on Imatinib-Resistant

BCR-ABL1 Mutants

72-hour proliferation assay with BCR-ABL–expressing Ba/F3 cells (ATPLite; Perkin Elmer). Trough levels at a dose of 400 mg twice daily (BID) (1.7 µM) exceed the IC50 determined in vitro for 32/33 BCR-ABL mutants (exception T315I)

Weisberg et al. Br J Cancer. 2006;94:1765.

Spectrum of Kinase Inhibition for Imatinib and Novel Compounds

Melo J, Hematology 2009

7

Time Optimal

response

Suboptimal

response

Failure Warnings

Diagnosis N/A N/A N/A High riskCCA/Ph+

3 months CHR, at least MinorCgR

No CgR Less than CHR N/A

6 months At least PCgR Less than PCgR No CgR N/A

12 months CCgR PCgR Less than PCgR Less than MMR

18 months MMR Less than MMR Less than CCgR N/A

Any time (duringtreatment)

Stable or improvingMMR

Loss of MMR Mutations (IM-sensit)

Loss of CHR, loss of CCgR, mutations (IM-insensit)CCA/Ph+

Increase in transcriptlevelsCCA/Ph-

New recommendations 2010 are marked in red.

Management of CMLRecommendations from the European LeukemiaNet Conclusion

The next step is

- to better define CMR (EUTOS project)

- to identify patients cohorts not relapsing after TKI

withdrawal