A.O.U.P. "P. Giaccone" University Hospital
DEPARTMENT OF ONCOLOGY
MEDICAL ONCOLOGY UNIT
(Dir.: Prof. Antonio Russo)
EGFR inhibitors for
overcoming resistance
Sergio Rizzo
Efficacy of EGFR-TKIs in EBFR mut. NSCLC
TKI
N. Pts
(TKI arm)
ORR
(%)
mPFS
(mesi)
IPASS
Mok, 2009
Gefitinib
609
71
5,7
WJTOG3405
Mitsudomi, 2010
Gefitinib
88
62
9,2
NEJ002
Maemondo, 2010
Gefitinib
114
74
10,4
First-SIGNAL
Han, 2012
Gefitinib
159
85
8,0
TORCH
Gridelli,2012
Erlotinib
380
42
6,4
OPTIMAL
Zhou, 2011
Erlotinib
82
83
13,1
EURTAC
Rosell, 2011
Erlotinib
86
64
9,7
LUX-Lung 3
Sequist, 2012
Afatinib
230
60
10,1
LUX-Lung 6
Wu, 2013
Afatinib
242
56
11,1
TOT: 1990
40-85
6-13
Studio di fase III
SUMMARY
Acquired resistance remains a major clinical problem in EGFR-mutant
lung cancer, usually occurring within a year of starting treatment
Review of literature 2016
Criteria for Acquired Resistance to EGFR TKIs
1
Patient has received prior therapy with an EGFR TKI
(monotherapy).
2
Tumor genotyping confirms the presence of a typical EGFR
mutation that is associated with sensitivity to EGFR TKIs (i.e.
exon 19 deletions, L858R, and G719X).
3
Patient achieves either a documented CR or PR or prolonged SD
(≥ 6 months) based on RECIST or WHO criteria.
4
Disease progression occurs despite uninterrupted exposure to an
EGFR TKI within 30 days.
5
Patient has not received additional systemic therapy between the
cessation of EGFR TKIs and the initiation of new therapy.
Jackman, D. et al. J. Clin. Oncol. 28, 357–360 (2009)
Causes of Acquired Resistance to EGFR TKIs
Genomic alterations
By-pass signaling
(Gene Amplifications)
Second site
mutations
Phenotypic alterations
NSCLC  SCLC
Epithelial-to-Mesenchymal Transition
By-pass signaling
(Gene Mutations)
Gainor & Shaw JCO 2013
Sequist, et al. Sci Trasl Med 2011
Percentage of Acquired-Resistance Mechanisms
Genetic alterations in EGFR
T790M mutations
D761Y, T854A, L747S mutations
50%
<5%
Bypass signaling tracks
MET amplification
5-22%
HER2 amplification
12%
PIK3CA mutations
5%
BRAF mutations
1%
CRKL amplification
9%
HGF over-expression
Rare cases
Phenotypic alterations
Transformation to SCLC
3-14%
Adapted from Gainor et al. J Clin Oncol, 2013
Percentage of Acquired-Resistance Mechanisms
SCLC trans.
(3-14%)
BRAF mut.
(1%)
PIK3CA mut.
(5%)
EMT
(?%)
HER2 ampl.
(12%)
EGFRT790M
(~50%)
MET ampl.
(5-15%)
• Tumours from approximately 40% of pts with acquired resistance do not
harbour a second-site mutation or MET amplification.
• Multiple investigations to identify resistance mechanisms are ongoing.
Del Re M, et al Expert Rev Mol Diagn. 2014
Second-site EGFR genetic alterations
Chromosome 7
EGF binding TM
EGF binding
EXON 2 5
7
13
Tyrosine kinase
16 17
18-21
Autophosphorilatyon
22-24
28
EGFR gene
V759L
Del Re M, et al Expert Rev Mol Diagn. 2014
L747S
D761Y
18
19
Nucleotide-binding loop
ins770-771
T790M
20
T854A
Acquired-Resistance
secondary mutations
21
Activation loop
The T790M
accounts for ~90%
of secondary
mutations observed
in EGFR
EGFR secondary somatic mutation in exon 20: T790M
T790M: mutation that interfere with drug binding in the EGFR ATP pocket
STERIC HINDRANCE
Threonine (~116 A) - Methionine (~163 A)
Michalczyk A et al. Bioorg Med Chem. 2008 Apr 1;16(7):3482-8.
Clonal selection hypothesis
How to explain the development of acquired resistance to TKIs
Primary
mutation
L858R
(exon 21)
Secondary
mutation
T790M
Resistant
tumor cells
(exon 20)
Additional
Mutation
Progenitor
cell
TKIs
Oncogenic
activation
Proliferation
Dead
cells
Russo A. et Al Cancer Treatment Reviews. 2010
T790M mutation occurs exclusively in cis with the
primary activating mutations in EGFR
Same allele
(in cis)
Opposite allele
(in trans)
Different
clone
Fast
growing
Unpredictable
growth behavior
More indolent
tumor growth
mod. da Alvaro L. J Thorac Oncol 2013
Prognostic role of BASELINE T790M mutation
Retrospective study on 173 pts harboring sensitive EGFR mut.
OS
TTP
25% of
MT pts
Pts with a high preexisting T790M % had worse clinical
outcomes to EGFR-TKIs than patients with a low T790M %
Lee Y. et al, Cancer 2014
Prognostic role of T790M-related ACQUIRED resistance
Prospective study on 369 pts harboring sensitive
EGFR mut. progressed after TKI and treated with CT
Lower rates of disease progression in T790M+ pts
PFS
OS
T790M+
T790M+
T790M-
T790M-
Li W. et al, Lung Cancer 2014
Rationale of TKI-continuation or Re-challenge
Following the discontinuation of TKI therapy disease flares may occur
Re-responses to EGFR TKIs following a TKI-free interval (case report)
Pz ♂ (66 aa.) NSCLC Adenocarcinoma, EGFR mut
a proportion of cells in a resistant tumour cell
population remain sensitive to EGFR inhibition
Hata A, et al. J Thorac Oncol 2013
Re-challenge of EGFR-TKI after a TKI-free interval
PD
PR
Start
TKI
PD
Tumor Volume
PR
Restart TKI
IMAGING
TKI-resistant clone
Stop TKI
TKI-sensitive clone
Time
TKI withdrawal
Advanced NSCLC guidelines: sensitizing EGFRmut+
Brain
Symptomatic
Advanced
NSCLC
EGFR+
TKI
PD*
Systemic
Asymptomatic
Isolated
lesion
Local therapy
+TKI
Multiple
lesions
WBRT
+TKI
Isolated
lesion
Local therapy
+TKI
Multiple
lesions
First-line
CT
Continue
TKI
*according to RECIST criteria
NCCN Clinical Recommendations
2015
Advanced NSCLC guidelines: sensitizing EGFRmut+
Tissue
biopsy
Advanced
NSCLC
EGFR+
TKI
PD
Liquid
biopsy
Prior to changing therapy, a biopsy is reasonable
to determine mechanism of acquired resistance
NCCN Clinical Recommendations
2016
T790M
2nd and 3rd generation of
TKIs to overcome
T790M-mediated resistance
Relative IC50
100x
T790M
10x
1x
Wt
Wt
EGFRm
Gefitinib
Erlotinib
Wt
EGFRm
Afatinib
Dacomitinib
EGFRm
T790M
Osimerinib
mod. da Li et al, Oncogene, 2008; Ranson et al, WCLC, 2013
2nd generation EGFR TKIs for overcoming resistance:
AFATINIB
% CONTROL VIABLE CELLS (72 HRS)
Growth inhibition of lung cancer cell lines harboring T790M by
AFATINIB and ERLOTINIB
Erlotinib
Afatinib
DRUG CONCENTRATION (M)
Li D et al. Oncogene. 2008 Aug 7;27(34):4702-11.
2nd generation EGFR TKIs for overcoming resistance:
DACOMITINIB (panHER inhibitor)
Phase II study with Dacomitinib
66 pre-treated (CT and erlotinib) advanced NSCLC pts
T790M
SD = 3 pts
PD = 3 pts
Reckamp KL, et al. Cancer 2014
3rd generation EGFR TKIs for overcoming resistance:
OSIMERTINIB (AZD9291)
AZD9291 in NSCLC EGFR mut. pts pre-treated with TKI (N=253)
ORR
Overall population
PFS
T790M+
T790MJanne PA, et al. . NEJM 2015
Acquired Resistance to 3rd generation EGFR TKI: C797S
Structural analysis of the
EGFR kinase domain mutations
Yu Z, et al. . Cancer Res 2007
Acquired Resistance to 3rd generation EGFR TKI: C797S
Emergence of a Third Mutation in the EGFR Tyrosine
Kinase Domain (case report)
Pt ♀ (60 yr) NSCLC Adenocarcinoma, EGFR mut (del ex19)
TKI
Local therapy
CT±TKI
AZD9291
?
Yu HA, et al. JAMA Onc. 2015
Acquired Resistance to 3rd generation EGFR TKI: C797S
Emergence of a Third Mutation in the EGFR Tyrosine
Kinase Domain (case report)
Mutation Analysis of Exon 20 of EGFR in Tumor Samples
Erlotinib
AZD9291
?
Yu HA, et al. JAMA Onc. 2015
The Allelic Context of T790M and C797S Acquired Mutations
?
Niederst MJ, et al. Clin Cancer Res 2015
EGFR resistance mutations in response
to TKI treatment and clonal selection
PD
SD
Tumor Volume
Start
1-2°g-TKI
PD
PR
Start
3°g-TKI
IMAGING
TKI-sensitive
Stop
1-2°g-TKI
Time
3°g-TKI-resistant
Acquired Resistance to EGFR TKIs: MET Amplification
MET Amplification in EGFR TKI resistant cells
(FISH) of MET/EGFR/CEP7 probe set
Pre-treatment
Post-treatment
Preexistence
and
clonal selection of
MET amplification in
EGFR mutant NSCLC
High-throughput FISH
Pre-treatment
Turke AB, et al. Cancer Cell 2010
Engelman JA, et al. Science 2007
Acquired Resistance to EGFR TKIs: MET Amplification
Survival analysis on EGFR-TKI according to the dynamic change of T790M
PFS
OS
Increased
Increased
Decreased
Increased T790M in ctDNA during TKI
Pts with decreasing
trend of T790M from
pre- to post-TKI
Higher rate of c-MET
amplification
Decreased
Better prognosis
Z. Wang et al. PLOSone 2014
Combined mechanisms of resistance: T790M and MET amplif.
Pt ♂ (55 yr), NSCLC Adenocarcinoma, EGFR mut (L858R)
Jun-2013
Oct-2013
Lung
- EGFRL858R
- TP53C277*
- TP53R110C
TKICT
CT
Jan-2014
TKI
Crizotinib
+
Erlotinib
Muscle
- EGFRL858R
- TP53C277*
-  MET amp
TKI
Crizotinib
+
Erlotinib
Apr-2014
Pleural eff.
- EGFRL858R
- EGFRT790M
- TP53R110C
-  MET amp
3a g TKI
Pleural eff.
- EGFRL858R
- EGFRT790M
- TP53R110C
Scheffler M, et al. J Thorac Oncol 2015
Other mechanisms of resistance: NSCLC  SCLC
Pt ♀ (40 yr), NSCLC Adenocarcinoma, EGFR mut (ex19 del)
PD
Baseline
PR
Re-biopsy
H&E
36 mths
TKI
CT
Erlotinib
Cis+Eto
SF
Adenocarcinoma
SCLC
RE-BIOPSY TO CLARIFY THE MECHANISM OF ACQUIRED
RESISTANCE BEFORE CHANGING THERAPY
Sequist, et al. Sci Trasl Med 2011
EGFR inhibitors for overcoming resistance
CONCLUSIONS
 What are the mechanisms of resistance to EGFR TKIs?
There are a several hypothesized mechanisms.
The most studied are the T790 mutation.
 Could the identification of the mechanisms of resistance be useful
in clinical management?
Yes. Many drugs targeting specifical mechanisms of resistance are
now available. A sequential strategy should be used.