The document discusses various strategies for overcoming resistance to endocrine therapy in advanced breast cancer, including targeting downstream signaling pathways like PI3K/Akt/mTOR that are often aberrantly activated in endocrine resistant disease. It reviews clinical trials demonstrating improved progression-free survival when adding drugs like everolimus or CDK4/6 inhibitors to hormonal therapy. The goal is to inhibit compensatory survival pathways that become relied upon by cancer cells to drive continued growth in the face of endocrine therapy.

1. Venciendo la resistencia a la terapia endocrina en
cáncer de mama avanzado
Mauricio Lema Medina MD
Clínica de Oncología Astorga / Clínica SOMA, Medellín

2. Third Law of Motion
For every action there is an equal and opposite re-action
Isaac Newton

3. HR+ HR-
Hormone-receptor (HR+) positive BC

4. Stephens PJ, et al. Nature 2009
The complex landscape of somatic rearrangements in human
breast cancer genomes
Her2+ HR+/Her2- Triple Negative

5. Biology

6. Biologic determinants of endocrine resistance in BC
Musgrove EA. Nat Rev Cancer 2009
Oestrogen action at the molecular level

7. Biologic determinants of endocrine resistance in BC
Musgrove EA. Nat Rev Cancer 2009
Anti-Estrogen (AE) action at the cell-cycle level

8. Biologic determinants of endocrine resistance in BC
Musgrove EA. Nat Rev Cancer 2009
Anti-Estrogen (AE) action at the apoptotic level

9. LTED increases acinar area in MCF-7 cell-lines
Liu, S, et al (including Gonzalez-Angulo, A). Oncotarget 2014; 5(19): 9049-9064

10. LTED increases colony numbers in BC cell-lines
Liu, S, et al (including Gonzalez-Angulo, A). Oncotarget 2014; 5(19): 9049-9064

11. LTED increases migrating cells in BC cell-lines
Liu, S, et al (including Gonzalez-Angulo, A). Oncotarget 2014; 5(19): 9049-9064

12. Phospho-RTK signaling in LTED
BC cell-lines
Liu, S, et al (including Gonzalez-Angulo, A). Oncotarget 2014; 5(19): 9049-9064

13. Phospho-RTK signaling in LTED BC cell-lines
Liu, S, et al (including Gonzalez-Angulo, A). Oncotarget 2014; 5(19): 9049-9064

14. Anti ER treatment with
Fulvestrant induces PI3k
pathway activation
Fox EM, Arteaga CL, Miller TW. Frontiers in Oncology, 2012

15. Aromatase induction in tamoxifen-resistant breast cancer: Role
of phosphoinositide 3-kinase-dependent CREB activation
• Preclínico (líneas celulares)
• MCF-7
• TAMR-MCF-7 (Resistentes a tamoxifen)
Phuong NT, et al. Cancer Lett. 2014 28; 351(1):91-9
TAMR-MCF-T
PI3K/AKT CREB Aromatasa
c-AMP-response element binding protein

16. Phospho-RTK signaling in LTED BC cell-lines
Liu, S, et al (including Gonzalez-Angulo, A). Oncotarget 2014; 5(19): 9049-9064

17. Anti-ER/RTKs/IGFR1 in LTED BC cell-lines
Liu, S, et al (including Gonzalez-Angulo, A). Oncotarget 2014; 5(19): 9049-9064

18. Anti-ER/RTKs/IGF-IR in LTED BC cell-lines
Liu, S, et al (including Gonzalez-Angulo, A). Oncotarget 2014; 5(19): 9049-9064

19. Anti-ER/RTKs/IGF-IR in LTED BC cell-lines
Liu, S, et al (including Gonzalez-Angulo, A). Oncotarget 2014; 5(19): 9049-9064

20. Targeting TK and ER overcomes endocrine-therapy resistance in BC
Liu, S, et al (including Gonzalez-Angulo, A). Oncotarget 2014; 5(19): 9049-9064

22. Fu X, Osborne CK, Schiff R, Breast 2013

23. Foxo3a

24. Foxo3a
Foxo3a
Transcriptional factor
Nucleus

25. Foxo3a
Foxo3a
Transcriptional factor
Nucleus

26. Foxo3a
Foxo3a
Transcriptional factor
Nucleus
p27 (antiproliferation)
FASl (proapoptosis)
ERE (antiproliferation)

27. Foxo3a
Foxo3a
Nucleus
AKT

28. Foxo3a
Foxo3a
Nucleus
AKT
P

29. Foxo3a
Foxo3a
Nucleus
AKT
P

30. Foxo3a
Foxo3a
Nucleus
AKT
P
Inactivation

31. Foxo3a
Foxo3a
Nucleus
AKT
P
Inactivation p27 (proliferation)
FasL (antiapoptosis)
ERE (proliferation)

32. Fu X, Osborne CK, Schiff R, Breast 2013

33. Foxo3a expression and OS in BC
Jiang Y, PLoS One, 2013

34. Development of PI3k inhibitors
Rodon J, et al. Nat Rev Clin Oncol 2013

35. Rb Phosphorilation by CDK4/6 promotes G1 to S-phase transition
Schwartz G, J Clin Oncol, 2005

36. Rb Phosphorilation by CDK4/6 promotes G1 to S-phase transition
Cadoo KA, Breast Cancer, 2014

37. PD 0332991 (anti CDK4/6) inhibits pRB phosphorilation
Finn RS. Breast Cancer Res, 2009

38. Biologic determinants of endocrine resistance in BC
Musgrove EA. Nat Rev Cancer 2009
Molecular mechanisms of Endocrine Resistance

39. In the clinic…

40. New Drugs to Overcome Resistance in Hormonal Therapy
Afinitor Product W Product X Product Y
Mechanism of Action • mTOR inhibitor • CDK4/6 kinase inhibitor • HDAC inhibitor • P13K inhibitor
Comparator • Exemestane • Letrozole • Exemestane • Fulvestrant
Median PFS • Afinitor + Exemestane -
7.8 months vs.
Exemestane alone -3.2
months (HR = 0.45)
• Product W + Letrozole -
26.1 months vs.
Letrozole alone -7.5
months (HR = 0.37)
• Product X +
Exemestane -7.1
months vs. Exemestane
alone -4.1 months (HR
= 0.58)
N/A
Median OS • OS results are not
mature
N/A Product X + Exemestane -
29.3 months vs.
Exemestane alone -22
months (HR = 0.75)
N/A
Ziaudinn and Tang
Review paper in preparation

41. Letrozole + Buparlisib (Pan-PI3k inhibitor) – Phase I Trial
Mayer IA, J Clin Oncol, 2014

42. Letrozole + Buparlisib (Pan-PI3k inhibitor) – Phase I Trial
Mayer IA, J Clin Oncol, 2014

43. Letrozole plus dasatinib improves PFS in MBC
Paul et al, #S3-07, SABCS 2013
• Randomized phase II multicenter USO trial
• HR+, HER2- MBC first line, 116 evaluable pts
• Adjuvant AI allowed if completed > 1yr before entry
• Letrozole +/- dasatinib (Src TKI), cross over allowed
• Primary end point: CBR (PR/CR/SD>6m)
DL L
CBR (%) 71 66
PFS (M) 22 11 p=0.05
• Toxicities: fatigue (38%), nausea (38%), anemia (25%), rash (23%), pleural effusion (16%) and edema (13%)
• 27% pts required dose reduction for dasatinib

44. Hortobagyi GN et al.
SABCS 2011;Abstract S3.7.
Baselga J et al.
N Engl J Med 2011;[Epub ahead of print].
Everolimus for Postmenopausal Women with
Advanced Breast Cancer: Updated Results of the
BOLERO-2 Phase III Trial

45. Adapted from Atkins MB et al. Nat Rev Drug Discov 2009;8(7):535-6.
Mechanism of Action of mTOR Inhibitors

46. Crosstalk between ER and mTOR Signaling
Adapted from Di Cosimo S, Baselga J. Nat Rev Clin Oncol 2010;7(3):139-47.

47. Hortobagyi GN et al. SABCS 2011;Abstract S3-7.
Postmenopausal, ER-positive
locally advanced or metastatic
breast cancer
Progression on letrozole or
anastrozole
(n = 724)
R
Everolimus – 10 mg daily
+
Exemestane – 25 mg daily
(n = 485)
Placebo
+
Exemestane – 25 mg daily
(n = 239)
Stratification: Sensitivity to prior hormonal therapy and presence of visceral metastases
Endpoints:
• Primary: Progression-free survival (PFS) by local assessment
• Secondary: Overall survival, overall response rate, quality of life,
safety, bone markers, pharmacokinetics
BOLERO-2 Study Design

48. Response and Clinical Benefit
Hortobagyi GN et al. SABCS 2011;Abstract S3-7.
Everolimus + Exemestane
Placebo + Exemestane
Response Clinical Benefit
Percent
12.0%
1.3%
50.5%
25.5%
P < 0.0001
P < 0.0001

49. BOLERO-2: Everolimus + Exemestane Improves PFS in HR+ MBC
Baselga J, et al. N Engl J Med. 2012;366:520-529.
0 6 12 18 24 30 36 42 48 54 60 66 72 78
Wks
ProbabilityofEvent(%)
Everolimus + exemestane
(median PFS: 10.6 mos)
Placebo + exemestane
(median PFS: 4.1 mos)
HR: 0.36 (95% CI: 0.27-0.47;
log-rank P < .001)
Patients at Risk, n
Everolimus
Placebo
485
239
385
168
281
94
201
55
132
33
102
20
67
11
43
11
28
6
18
3
9
3
3
1
2
0
0
0
100
90
80
70
60
50
40
30
20
10
0
Central Assessment

50. BOLERO-2: Final PFS Analysis (18-Mo Follow-up)
PFS, Mos EVE + EXE PBO + EXE HR (95% CI) P Value
Local review 7.8 3.2 0.45
(0.38-0.54)
< .0001
Central review 11.0 4.1 0.38
(0.31-0.48)
< .0001
With visceral mets 6.83 2.76 0.47
(0.37-0.60)
--
Without visceral mets 9.86 4.21 0.41
(0.31-0.55)
--
Bone-only mets 12.88 5.29 0.33
(0.21-0.53)
--
Progression after neo/adj
therapy
11.50 4.07 0.39
(0.25-0.62)
--
 OS data still not mature (HR: 0.77; 95% CI: 0.57-1.04)
 Most common grade 3/4 AEs were stomatitis (8%), hyperglycemia (5%), fatigue (4%)
Piccart, M, et al. SABCS 2012. Abstract P6-04-02.

51. Common Adverse Events
Everolimus + Exemestane
(n = 482)
Placebo + Exemestane
(n = 238)
All Grades Grade 3/4 All Grades Grade 3/4
Stomatitis 59% 8% 11% <1%
Rash 39% 1% 6% 0
Fatigue 36% <5% 27% 1%
Diarrhea 33% <3% 19% <1%
Decreased appetite 30% 1% 12% <1%
Nausea 29% <2% 28% 1%
Noninfectious pneumonitis 15% 3% 0 0
Hyperglycemia 14% <6% 2% <1%
Hortobagyi GN et al. SABCS 2011;Abstract S3-7.

52. Bolero-2: OS of Exemestane + Everolimus in mBC
Piccert M, et al. Ann Oncol 2014

53. Finn RS, et al. SABCS 2012. Abstract S1-6.
Aromatase Inhibitor + CDK4/6 Inhibitor Improves PFS in ER+ MBC
0
0.2
0.4
0.6
0.8
1.0
0 6 1210 14
Mos
16 20 22 28
PD 991 + LET (n = 84)
21 (25)
26.1
(12.7-26.1)
PFSProbability
Pts at Risk, n
PD 991 + LET
LET
84
81
75
57
60
38
53
29
43
22
35
17
25
11
3
1
1
1
24 261882 4
0.3
0.5
0.7
0.9
0.1
LET (n = 81)
40 (49)
7.5
(5.6-12.6)
18
6
15
5
14
4
9
3
5
3
Events, n (%)
Median PFS, mos
(95% CI)
HR
(95% CI)
P value
0.37
(0.21-0.63)
< .001

54. Investigational Agents in MBC
Agent MOA Phase Patient Population Response, % (n/N)
Abemaciclib +
fulvestrant[1] CDK4/6 inhibitor I HR+ MBC
19.1 (9/47) PR;
29.8 (14/47) SD ≥ 24 wks;
21.3 (10/47) SD < 24 wks
LEE011 and/or BYL719 +
letrozole[2]
CDK4/6 inhibitor PI3K
inhibitor
Ib
Postmenopausal ER+ HER2-
MBC
Preliminary clinical activity
Dose escalation continues
LEE011 +
EVE + EXE[3]
CDK4/6 inhibitor
mTOR inhibitor
Ib/II
Postmenopausal ER+ MBC;
refractory to NSAIs
7 (1/14) PR;
50 (7/14) SD
BYL719 + letrozole[4] PI3K inhibitor Ib ER+ HER2- MBC
11 (3/26) PR;
27 (7/26) CBR
Sorafenib + letrozole[5] Multitarget TKI I/II
Postmenopausal HR+ MBC;
no prior therapy for MBC
39 (16/41) PR;
41 (17/41) SD;
Median OS: 51.5 mos
ABT-888[6] PARP inhibitor II
BRCA+ MBC; no prior
platinum agents
BRCA1: 20 (4/20) CBR
BRCA2: 42 (8/19) CBR
1. Patnaik A, et al. ASCO 2014. Abstract 534. 2. Munster PN, et al. ASCO 2014. Abstract 533. 3. Bardia A, et al. ASCO 2014. Abstract 535. 4. Mayer IA, et al. ASCO
2014. Abstract 516. 5. Tan AR, et al. ASCO 2014. Abstract 531. 6. Somlo G, et al. ASCO 2014. Abstract 1021.

55. First-line Letrozole vs Tamoxifen,
Then Crossover
Median OS
Letrozole: 34 mos
Tamoxifen: 30 mos
Time to Crossover
Letrozole: 17 mos
Tamoxifen: 14 mos
Mouridsen H, et al. J Clin Oncol. 2003;21:2101-2109.
P = .53 (long-rank test)
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0 6 12 18 24 30 36 42 48 54 60
Mos
ProportionAlive
Letrozole 1st Tamoxifen 1st

56. CONFIRM: Fulvestrant 500 mg vs 250 mg in Postmenopausal Women
With ER+ MBC
Fulvestrant 250 mg*
(n = 374)
Fulvestrant 500 mg†
(n = 362)
Postmenopausal
women
with ER-positive
advanced
breast cancer
(N = 736)
*Fulvestrant 250 mg: 1 injection of fulvestrant 250 mg IM + 1 placebo injection on Day 0; 2 placebo injections on
Day 14; 1 injection of fulvestrant 250 IM + 1 placebo injection on Day 28, then every 28 days thereafter.
†Fulvestrant 500 mg: 2 injections of fulvestrant 250 mg IM on Days 0, 14, 28, then every 28 days thereafter.
DiLeo A, et al. SABCS 2012. Abstract S1-4.

57. CONFIRM: Effect of Fulvestrant 500 mg vs
250 mg on Survival in Postmenopausal Women
 Baseline characteristics appeared well balanced between treatment arms
 Subsequent therapies were well balanced between arms, with approximately 60% of patients
receiving subsequent chemotherapy and approximately one third receiving other hormonal
therapy
Outcome
Timing of
Analysis
Fulvestrant
500 mg
Fulvestrant
250 mg HR (95% CI)
Median PFS First* 6.5 mos 5.5 mos 0.80‡ (0.68-0.94)
Median OS First* 25.1 mos 22.8 mos 0.84§ (0.69-1.03)
Median OS Final† 26.4 mos 22.3 mos 0.81¶ (0.69-0.96)
*First analysis was performed at 50% maturity.
†Final analysis was performed at 75% maturity.
‡ P = .006
§P = .001
¶P = .016
DiLeo A, et al. SABCS 2012. Abstract S1-4.

58. EFFECT: Fulvestrant vs Exemestane After Progression of
Nonsteroidal AI
PFSProbability
Mos
Pts at Risk, n
Fulvestrant
Exemestane
3.73.7Median, mos
HR: 0.963 (95% CI: 0.819-1.133; P = .6531)
Cox analysis, P = .7021
ExemestaneFulvestrant
Fulvestrant
Exemestane
0 3 6 9 12 15 18 21 24 27
0.0
0.2
0.4
0.6
0.8
1.0
351 195 96 50 25 12 4 2
342 190 98 41 21 12 8 6
0
1
0
0
Chia S, et al. J Clin Oncol. 2008;26:1664-1670.

59. FIRST Study Design
Robertson JF, et al. Clin Oncol. 2009;27:4530-4535.
Endpoints at primary
data cutoff
Primary endpoint
 Clinical benefit rate
Secondary endpoints
 ORR
 TTP
 Duration of response
 Duration of clinical benefit
 Safety
Exploratory endpoint
 Best response to subsequent
therapy
Open-label first-line ER+ postmenopausal
patients with advanced breast cancer
(target, N = 200; actual, N = 205)
Fulvestrant 500 mg IM
on Days 0, 14, 28, and every
28 days thereafter
Anastrozole 1 mg/day PO
Progression
Follow-up
Progression
Follow-up

60. 0
0.2
0.4
0.6
0.8
1.0
0 6 12 18 24
Mos
30 36 42 48
Fulvestrant 500 mg
Anastrozole 1 mg
ProportionofPatientsAlive
andProgressionFree
HR: 0.66 (95% CI: 0.47-0.92;
P = .01)
Pts at Risk, n
Fulvestrant 500 mg
Anastrozole 1 mg
102
103
74
69
65
55
52
39
45
30
34
21
20
8
6
2
0
0
Robertson JF, et al. Breast Cancer Res Treat. 2012;136:503-511.
FIRST: TTP at Follow-up Analysis

61. Postmenopausal women
with hormone receptor–
positive MBC
(N = 707)
Anastrozole 1 mg/day PO +
Fulvestrant 500 mg on Day 1,
250 mg on Days 14 and 28,
250 mg every 28 days thereafter
(n = 355)
Anastrozole 1 mg/day PO
(n = 352)
Treatment until disease
progression
Stratified by previous adjuvant
tamoxifen
Women with
progression encouraged
to cross over to receive
fulvestrant
Mehta RS, et al. N Engl J Med. 2012;367:435-444.
SWOG S0226: Study Design
 Primary endpoint: PFS
 Secondary endpoints: OS, safety

62. SWOG S0226: PFS and OS Overall and by Previous Adjuvant Tamoxifen
Endpoint Anastrozole +
Fulvestrant
Anastrozole HR (95% CI) P Value
Median PFS (n = 694), mos 15.0 13.5 0.80
(0.68-0.94)
.007
 No previous adjuvant
tamoxifen (n = 414)
17.0 12.6 0.74
(0.59-0.92)
.0055
 Previous adjuvant tamoxifen
(n = 280)
13.5 14.1 0.89
(0.69-1.15)
.37
Median OS (n = 694), mos 47.7 41.3 0.81
(0.65-1.00)
.049
 No previous adjuvant
tamoxifen (n = 414)
47.7 39.7 0.74
(0.56-0.98)
.0362
 Previous adjuvant tamoxifen
(n = 280)
49.6 44.5 0.91
(0.65-1.28)
.59
Mehta RS, et al. N Engl J Med. 2012;367:435-444.

63. Endocrine Therapy Sequencing in MBC: Which Order Is Best?
 AI or fulvestrant are most effective first-line single agents; fulvestrant ± AI reasonable
choice for endocrine therapy–naive patients with MBC
 Continue endocrine therapies until resistance
 mTOR inhibition with everolimus + exemestane is best second-line therapy after
progression on nonsteroidal AI
 After everolimus, back to anti-ER therapy alone or enhanced blockade of PI3K pathway
 Addition of CDK4/6 inhibitor to first-line letrozole may become a new SOC; phase III trial
under way

64. Conclusiones
La terapia dirigida inicial en NSCLC aporta beneficios en EFS; y, posiblemente, en OS
Se deben identificar en forma OPORTUNA los genes conductores (drivers) potencialmente
intervenibles (ie, EGFR, entre otros)
Las variables clínicas usuales son insuficientes para discriminar quiénes van a ser positivos
para mutaciones potencialmente intervenibles

65. ER pathway and Fulvestrant response elements

66. Mechanisms of secondary resistance to hormonal
therapy in BC
• Loss of Era (15-20%)
• Era mutations (1%)

67. Aberrations in PI3K pathway in BC
PI3K catalytic subunits p110α (PIK3CA) and p110β (PIK3CB)
PI3K regulatoy subunits p85α (PIK3RA)
PI3K effectors: AKT1, AKT2 and PDK1
Lipid phosphatases: PTEN and INPP4B
Found in 70% of BC
Fu X, Osborne CK, Schiff R, Breast 2013

68. Aberrations in PI3K pathway in BC
PI3K catalytic subunits p110α (PIK3CA) and p110β (PIK3CB)
PI3K regulatoy subunits p85α (PIK3RA)
PI3K effectors: AKT1, AKT2 and PDK1
Lipid phosphatases: PTEN and INPP4B
49% vs 32% - Luminal A vs Luminal B
Found in 70% of BC
Fu X, Osborne CK, Schiff R, Breast 2013

69. Loi S, et al. PNAS, 2010
PIK3CA mut associated with
lower downstream pS6
signaling in HR+ BC treated
with Tam

70. Loi S, et al. PNAS, 2010
PIK3CA mut associated with
better outcome in Tam
treated ER+ BC

71. Reprinted by permission from the American Association for Cancer Research: Johnston SR. Clin Cancer Res. 2005;11:889s-899s.
ER target gene transcription
SOS
P P
P P
PI3-K
akt
P
P
RAS
RAF
MEK
MAPKp90RSK
ER
P
p160
Basal
transcription
machineryCBPER ER
PP P
ERE
Plasma
membrane
Cytoplasm
Nucleus
E2
SERD
AI T
IGF1R
EGFR/HER2
Increased signaling
through PI3-K
pathway
Increased
signaling through
EGFR and/or
IGF1-R
VEGFR
Mechanisms of Hormone Resistance

72. ER status and OS in BC
Jiang Y, PLoS One, 2013

73. Foxo3a / ER status and OS in BC
Jiang Y, PLoS One, 2013

74. Dual function of YAP-1 in cancer
Wang and Tang Can and Met Rev 2013