Can we eventually stop TKI in all CML patients? John Goldman - - PowerPoint PPT Presentation

‘Can we eventually stop TKI in all CML patients?’

John Goldman

Controversies in Hematology Rome, 12 September 2010

• The vast majority of responding patients relapse within a few

weeks or months if they discontinue treatment with imatinib or a 2G-TKI

• In vitro studies show that ‘quiescent’ stem cells are resistant to

both imatinib and dasatinib

• Complete molecular response is consistent with survival of up to

107 leukemia cells; a DNA based PCR may be more sensitive than conventional cDNA-based PCR

• The analogy with results of allogeneic stem cell transplantation

support the concept that small numbers of leukemia stem cells may remain in the body for many years and then regenerate leukemia

Evidence and concepts in favour of the notion that TKI rarely eliminates residual leukemia cells

• LSC may be entirely eradicated by continued treatment with

imatinib or 2G-TKI

• If they are not, there are three situations where quiescent LSC

may remain innocuous: 1. They are inhibited or undergo apoptosis in the presence of TKI as soon as they start to cycle,

• 2. Progression to advanced phase occurs always at the level of a

more committed progenitor cell, or

• 3. Low levels of LSC are readily controlled by immunological

mechanisms that don’t work with large cell numbers

Targeting quiescent stem cells

If eliminating residual disease really is important, what can we do to target them effectively?

Use existing TKIs according to different schedules

• Use TKIs in combination with new anti-BCR-ABL drugs.
• Use TKIs in conjunction with signal transduction

inhibitors or epigenetic inhibitors – eg FTIs, HDAC inhibitors, autophagy inhibitors, PP2A activators and

• thers
• Immunotherapy with vaccines or CTLs directed against

BCR-ABL, WT1, PR3, PRAME, etc

Eliminating residual leukaemia cells

• 1. Does elimination of more differentiated progenitor

cells (eg GMP) prevent leukaemia progression?

• 2. Does adherence become more of a problem as

patients continue therapy for some years?

• 3. Do we need develop more sensitive techniques for

measuring residual disease in general and for leukaemia ‘stem cells’ in particular?

• 4. If eliminating residual disease really is important,

what can we do to target them effectively ?

Does elimination of more differentiated progenitor cells (eg GMP) prevent leukaemia progression?

β-catenin and leukaemic stem cell self-renewal

• β-catenin is activated by Wnt and Frizzled; loss
• f β-catenin impairs CML LSC renewal (Zhao,

Reya et al, 2007)

• β-catenin is normally inactivated in the

cytoplasm by APC/GSK3β/axin complex

• When activated β-catenin enters the nucleus

and combines with LEF and TCF and induces excessive self-renewal by targeting expression of cyclin D1 and MYC

• Mis-splicing of exons 8 and 9 of the GSK-3β

gene could contribute to survival of β-catenin in blastic phase

• PKF-115 interferes with the β-catenin /LEF/TCF

complex and reverses excessive stem cell renewal in a mouse xenograft model

Jamieson et al. N Engl J Med. 2004;351:657-667.

In myeloid blastic crisis β-catenin is over-expressed in GMP compared with putative stem cells

β-catenin and leukaemic stem cell self-renewal

• β-catenin is activated by Wnt and Frizzled; loss
• f b-catenin impairs CML LSC renewal (Zhao,

Reya et al, 2007)

• Normal β-catenin is normally inactivated in the

cytoplasm by APC/GSK3β/axin complex

• When β-catenin enters the nucleus it combines

with LEF and TCF and induces excessive self- renewal by targeting expression of cyclin D1 and MYC

• Mis-splicing of exons 8 and 9 of the GSK-3β

gene could contribute to survival of β-catenin in blastic phase

• PKF-115 interferes with the β-catenin/ LEF/TCF

complex and reverses excessive stem cell renewal in a mouse xenograft model

LT-HST MPP ST-HST MEP CMP GMP

Erythrocytes, platelets Granulocytes, macrophages

CLP Pro-B Pro-T Pro-NK

T-cells NK-cells B-cells

Actual target for myeloblastic progression

CD33 CD123

Loss of p16 in lymphoblastic transformation of CML

9p21.3 CDKN2A (p16, INK4A)

Chromosome 9 H Sill, JM Goldman and NC Cross. Blood 1995; 85: 2013-2016

Homozygous deletions of the p16 [CDKN2A] tumor suppressor gene are associated with lymphoid transformation of CML

Coincidental loss at 7p and 9p in CML in lymphoblastic transformation

9p24.1 9p21.3 9p13.2 PAX5 MLLT3 CDKN2A (p16) PDCD1LG2 JMJD2C 7p12.2 7p15.2 7p14.1 TRAP IKZF1 (Ikaros) HOXA7

Background

• p16 lost in 50% of patients with CML-BT(L) (Sill et al, 1995)
• IKZF1 (Ikaros) lost in majority of 20/22 adults and 16/21 children with Ph+ALL, possibly

due to aberrant RAG-mediated recombination. CDKN2A (p16) lost in 53% of patients. Inactivating mutations found in PAX5 (Mullighan et al, 2008)

LT-HST MPP ST-HST MEP CMP GMP

Erythrocytes, platelets Granulocytes, macrophages

CLP Pro-B Pro-T Pro-NK

T-cells NK-cells B-cells

Actual target for lymphoblastic progression

CD10 CD19

Does elimination of more differentiated progenitor cells (eg GMP) prevent leukaemia progression? The preliminary evidence suggesting that the expanded ‘clone’ myeloid blastic transformation derives from a genetically altered GMP population (at least in some cases) taken together with the phenotypic data could mean that the answer is ‘yes’

Does adherence become more of a problem as patients continue therapy for some years? After some years on imatinib patients a relatively high proportion of patients appear to be taking less than the prescribed dose. This conclusion is based on reasonably objective measurements.

Do we need develop more sensitive techniques for measuring residual disease in general and for leukaemia ‘stem cells’ in particular?

Decreasing residual leukaemia

N u m b e r

• f

l e u k a e m i a c e l l s ( l

• g10

)

1 2 3 4 5 6 7 8 9 10 11 12 13 0.0001 0.001 0.01 0.1 1 10 100

BCR-ABL1/ABL1 ratio (%)

Leucocytosis RQ-PCR positive Ph-chromosome pos Ph-negative but

BCR-ABL1 transcript measurement is still not sensitive enough to assess good responders

1000

?

Cure ?

Patterns of residual disease in IM-treated patients in CMR

Sobrinho-Simoes et al, Blood 2010

gDNA+ gDNA+

If eliminating residual disease really is important, what can we do to target them effectively?

If eliminating residual disease really is important, what can we do to target them effectively?

• Use existing TKIs according to different schedules

If eliminating residual disease really is important, what can we do to target them effectively?

• Use existing TKIs according to different schedules
• Use TKIs in combination with new anti-BCR-ABL

drugs.

If eliminating residual disease really is important, what can we do to target them effectively?

• Use existing TKIs according to different schedules
• Use TKIs in combination with new anti-BCR-ABL

drugs.

• Use TKIs in conjunction with signal transduction

inhibitors or epigenetic inhibitors – eg FTIs, HDAC inhibitors, autophagy inhibitors, PP2A activators and others

50 100 150 200 250

No drug control BMS-214662 250nM IM 5uM BMS-214662 + IM Dasatinib 150nM BMS-214662 + Dasatinib

Condition % No drug contro

P=0.033 P=0.032 P=0.027

BMS-214662 inhibits CML LTC-IC colony formation

• IM and dasatinib protect CML stem cells and result in increased colony

formation (p=0.033 versus no drug control)

• Virtual elimination of all colonies in the BMS-214662-containing arms

Copland et al, Blood 2008; 111: 2843-53

CML

If eliminating residual disease really is important, what can we do to target them effectively?

• Use existing TKIs according to different schedules
• Use TKIs in combination with new anti-BCR-ABL

drugs.

• Use TKIs in conjunction with signal transduction

inhibitors or epigenetic inhibitors – eg FTIs, HDAC inhibitors, autophagy inhibitors, PP2A activators and others

• Immunotherapy with vaccines or CTLs directed

against BCR-ABL, WT1, PR3, PRAME, etc

The inescapable conclusion is TKI alone suppress the bulk of leukemia cells in responding patients but do ..not eradicate residual stem cells so additional measures are required to cure CML

The inescapable conclusion is TKI alone suppress the bulk of leukemia cells in responding patients but do not eradicate residual stem cells, so additional measures are required to cure CML

The end