18th Annual Perspectives in Breast Cancer Growth Factor Pathways in Hormone Resistant Breast Cancer Christy A Russell, MD Fight On!

Tumors Classified as ER+ Have Varied Receptor Expression Profiles ASCO/CAP recommends that a tumor specimen be considered ER+ if >1% of tumor cells test positive for ER. Breast cancer classified as ER+ is a heterogeneous disease, based on varying ER expression level PR status HER2 status BC with strong ER expression are biologically distinct from those with weak ER expression

Hormone Receptor Positive Determination Any endocrine therapy (n = 777) Allred Score* for Estrogen Receptor Score Component of Score Straining Proportion of malignant cells straining for ER None 1 <0.01 2 0.01-0.1 3 0.1-0.33 4 0.33-0.67 5 >0.67 Intensity Average intensity of positively stained cells Weak Intermediate Strong Allred Score of > 3 are generally considered hormone-sensitive Harvey et al. J Clin Oncol 1999;17:1474-1481

Stable disease on hormone therapy provides similar benefit as CR or PR Compare Survival with Stable Disease (Clinical Benefit) to Survival with CR or PR with Anastrozole Use in ABC Clinical Benefit = CR + PR + Stable  24 wks 100 80 At 2-Year Risk Deaths Estimate CR or PR 33 10 85% Stable  24wk 78 23 86% Other 152 118 35% 60 Survival (%) 40 20 1 2 3 4 Years From Randomization Stable disease on hormone therapy provides similar benefit as CR or PR ABC = advanced breast cancer, Clinical benefit = no prognosis for > 24wks Robertson JF, et al. Breast Cancer Res Treat. 1999;58:157-162.

Patients with Disease Progression on One Hormone Therapy May Respond to Another Hormone Therapy C 40% 30% 25% 15% 1st Line 2nd Line 3rd Line 4th Line An optimal sequence of hormone therapies has not been defined Bavior C, et al. Ann Oncol 2012. Epub Feb 8; Osborne Ck, Schiff R. Ann Res Med 2011;62:233-247

NCCN Guidelines Recommend Serial Endocrine Therapy for Hormone Receptor Positive, HER2- Advanced Breast Cancer, Not in Visceral Crisis NCCN Clinical Practice Guidelines in Oncology. Breast Cancer, version 1.2012; Osborne CK, et al. Ann Rev Med 2011;62:233-247

Hormone Receptor Positive, Advanced Breast Cancer Unmet Need With initial hormone therapy of advanced breast cancer: About 30% will have clinical response (PR, CR) About 50% will have clinical benefit (no progression for 24 weeks) However, almost all will develop resistance and ultimately have disease progression

Endocrine Agents for Postmenopausal Breast Cancer SERMs Tamoxifen Toremifene Raloxifene Estrogens Estradiol DES, EE2 ER-Down Regulator Fulvestrant Aromatase Inhibitors Anastrozole Letrozole Exemestane Progestins Megestrol Acetate MPA Androgens Fluoxymesterone

Review of Trials of Hormone Therapy in First-Line Advanced Breast Cancer

Selected Trials of HT in First-Line ABC Trial or Lead Author N Nabholtlz Anastrozole vs tamoxifen 1021 Mouridsen Letrozole vs tamoxifen 916 Paridaens Exemestane vs tamoxifen 371 Howell Fulvestrant (250) vs tamoxifen 587 S02226 Fulvestrant (250, loading) + anastrozole vs anastrozole 694 FACT Fulvestrant (250, loading) + anastrozole vs anastrozole 514 FIRST Fulvestrant (500) vs anastrozole 205 Mehta SABCS 2011, Abst S1-1; Bergh J Clin Oncol 2012 [Epub ahead of print]; Nabholtz Eur J Cancer 2003;39:1684-1689; Mouridsen 2003;21:2101-2109; Paridaens 2008;26:4883-4890; Howell J Clin Oncol 2004;22:1605-1613.

First-Line Phase III Studies: AIs and/or Fulvestrant (250) vs Tamoxifen AIs have improved efficacy compared with tamoxifen2-4 TTP (mo): anastrozole (10.7) vs tamoxifen (6.4)2 TTP (mo): letrozole (9.4) vs tamoxifen (6.0)3 PFS (mo): exemestane (9.9) vs tamoxifen (5.8)4 Fulvestrant (250) has similar efficacy compared with tamoxifen5 TTP (mo): fulvestrant (8.2) vs tamoxifen (8.3)

First-Line Phase III Studies Fulvestrant (250, loading ) First-Line Phase III Studies Fulvestrant (250, loading )* + Anastrozole vs Anastrozole In SWOG S0226 (n = 694), fulvestrant addition improved: PFS (mo); fulvestrant + anastrozole (15.0) vs anastrozole (13.3), P = 0.007 OS (mo): fulvestrant + anastrozole (47.7) vs anastrozole (41.3), P = 0.049 In FACT (n=514), fulvestrant addition had: no effect on PFS or OS seen: OS (mo): fulvestrant + anastrozole (37.8) vs anastrozole (38.2), P = 1.00 Mixed results for fulvestrant 250, loading Mehta, et al. SABCS 2011, Abst S1-1 Bergh, et al. J Clin Oncol 2012;30(16):1919-25 *Fulvestrant 500 mg d 1 IM, 250 mg d 14 and 28, 250 mg every 28 days thereafter.

FIRST: Fulvestrant (500) vs Anastrozole (Phase II) FULVESTRANT 500 mg IM days 1, 14, 28 and q28days thereafter Primary CBR defined as CR, PR, and SD for > 24 wks Secondary ORR, TTP, DoR N = 205 PMW with previously untreated HR+ advanced breast cancer ANASTROZOLE 1 mg QD orally FUL (500) n = 102 ANAS n = 103 HR P-value TTP (mo) 23.4 13.1 0.66 0.01 ORR (%) 36.0 35.5 1.02 0.947 CBR (%) 72.5 67.0 1.30 0.386 Robertson JRF, et al. SABCS 2010. Abstract S1-3, Robertson et al. J Clin Oncol 2009;27:4530-35 13

FIRST: TTP, Fulvestrant (500) vs Anastrozole (Phase II) 1.0 Fulvestrant 500 mg 0.8 Anastrozole 1 mg 0.6 Proportion of patients alive and progression-free 0.4 HR = 0.66 0.2 95% CI (0.47, 0.92) p=0.01 0.0 6 12 18 24 30 36 42 48 Time (months) Fulvestrant 500 mg n = 102 (%) Anastrozole 1 mg n = 103 (%) Percent with progression (%) 63 (61.8) 79 (76.7) Median (months) 23.4 13.1 Robertson SABCS 2010, Abst S1-3 14

Review of Trials of Hormone Therapy in Advanced Breast Cancer After Progression on Prior Non-Steroidal Aromatase Inhibitor

Selected Trials of Fulvestrant Use After Progression on Prior NSAI* EFECT Fulvestrant vs exemestane 693 SoFEA Fulvestrant + anastrozole vs fulvestrant vs exemestane 750 CONFIRM Fulvestrant high vs fulvestrant low 736 Fulvestrant 250, loading Fulvestrant 500 *Non-steroidal aromatase inhibitor.

EFECT: Fulvestrant (250, loading) vs Exemestane PMW with advanced HR+ BC after failure of NSAI therapy FULVESTRANT 500 mg IM day 1, 250 mg day 14, 28, monthly Primary TTP Secondary ORR, CBR, DOR, TTR, OS, tolerability EXEMESTANE 25 mg QD FUL n = 351 EXE n = 342 P-value TTP (mo) 3.7 0.653 ORR (%) 7.4 6.7 0.736 Fulvestrant (250 loading) similar to exemestane Chia S, et al. J Clin Oncol 2008;26(10):1664-1670 17

SoFEA: Fulvestrant (250, loading) With or Without Anastrozole vs Exemestane FULVESTRANT 500 mg loading dose on day 1, then 250 mg monthly + ANASTROZOLE 1 mg/daily N = 723 Post menopausal women with advanced HR+ BC following progression on NSAI Primary PFS Secondary ORR, CBR, OS, tolerability FULVESTRANT 500 mg loading dose on day 1, then 250 mg monthly + Placebo daily EXEMESTANE 25 mg/daily No significant differences were observed in PFS, ORR, CBR, or OS FUL 500 n = 231 FUL + ANA n = 243 EXE PFS (mo) 4.8 4.4 3.4 Johnston S et al. EBCC-8. 2012 18

CONFIRM: Fulvestrant 250 vs 500 mg FULVESTRANT 500 mg IM on day 1, 14, 28, monthly N = 736 PMW with advanced HR+ BC after failure of prior endocrine therapy Primary PFS Secondary ORR, CBR, DoCB, OS, Qol FULVESTRANT 250 mg IM monthly FUL 500 n = 362 FUL 250 n = 374 P-value PFS (mo) 6.5 5.5 0.004 ORR (%) 9.1 10.2 0.795 CBR (%) 45.6 39.6 0.100 Bachelot T, et al. J Clin Oncol 2012. Epub 1-7; DiLeo et al. J Clin Oncol 2010;28:4594-4600 19

Mechanisms of ER Action in Breast Cancer

ER Target Gene Transcription Mechanisms of Endocrine Resistance MoAb IGF1R Increased upstream signaling through EGFR and/or IGF-IR and or VEGFR TKI AB EGFR/HER2 VEGFR MoAb P P P P P TKI P SOS PI3-K TKI RAS RAF Increased signaling through PI3-K pathway CCI RAD Akt MEK p90RSK MAPK SERD AI T ER E2 P p160 Basal Transcription Machinery CBP ER Cytoplasm ERE ER Target Gene Transcription Cell Growth Nucleus Plasma Membrane Mechanisms of intrinsic and acquired resistance likely similar From Johnston CCR 2005

Endocrine Resistance and the PI3K/AKT/mTOR Pathway Evidence suggests that the PI3K/AKT/mTOR pathway becomes activated in hormone resistant breast cancer This pathway allows cells to survive despite concurrent endocrine therapy Targeting the PI3K/AKT/mTOR pathway could provide benefit in metastatic breast cancer that is becoming resistant to the current endocrine therapy Johnston, S. Role of the mTOR Pathway in Endocrine Resistant Breast Cancer — Opportunities for Novel Combination Strategies. 2009.

PI3K/AKT/mTOR Pathway http://www.cellsignal.com/reference/pathway/mTor.html

Everolimus as mTOR Kinase Inhibitor Mechanisms of Action (MOA): everolimus inhibits mTOR through allosteric binding to the mTORC1 complex Reduces tumor angiogenesis by inhibiting VEGF and HIF-1 expression Targets pathway known to be involved in endocrine resistance Available as oral agent Villarreal-Garza, et al. Ann Oncol 2012 May 2 Epub ahead of print Barnett, et al. Pharmacotherapy 2012;32:383-96

Selected Trials of Hormonal Therapy Including Everolimus After Progression on Prior AI* EFECT Fulvestrant (250) vs exemestane 693 CONFIRM Fulvestrant (500) vs fulvestrant (250) 736 SoFEA Fulvestrant + anastrozole vs fulvestrant (250) vs exemestane 750 TAMRAD Tamoxifen + everolimus 110 BOLERO-2 Exemestane + everolimus 725 Fulvestrant 250 Everolimus Combinations Fulvestrant 500 *Non-steroidal aromatase inhibitor.

TAMRAD: Tamoxifen + Everolimus (Phase II) Phase 2 study; N=111 PMW with advanced HR+ HER2- BC Previously treated with non-steroidal aromatase inhibitor therapy in adjuvant or metastatic setting Tamoxifen 20 mg/day + Everolimus 10 mg/day Primary CBR at 6 months Secondary Safety, TTP, OS, ORR Tamoxifen 20 mg/d + Placebo TAM+EVE n = 54 TAM n = 57 P-value CBR (6 mo) 61% 42% 0.045 TTP (mo) 8.6 4.5 0.002 Bachelot T, et al. J Clin Oncol 2012. Epub 1-7. 26

TAMRAD: Time to Progression Hazard Ratio (HR) = 0.53; 95% CI (0.35-0.81) Exploratory log-rank: P = 0.0021 TAM: 4.5 mo. TAM + EVE: 8.6 mo. Month 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 Probability of Survival TAM TAM + EVE Patients at risk TAM + RAD: n = TAM : n = 54 57 45 44 39 30 34 25 13 19 11 7 1 9 Everolimus plus tamoxifen reduced time to progression by 47% Bachelot T, et al. J Clin Oncol 2012.Epub 1-7 27

TAMRAD: Overall Survival Everolimus plus tamoxifen increased overall survival by 55% 28

Tamoxifen With or Without Everolimus: TAMRAD: Safety The addition of everolimus resulted in an increase in the expected toxicities, including fatigue, stomatitis, rash, diarrhea, and pneumonitis (predominantly grade 1-2) Select Grade 3-4 Adverse Events Tamoxifen + Everolimus (n = 54) Tamoxife n (n = 57) Stomatitis 6 (11%) Rash 3 (6%) 1 (2%) Anorexia 5 (9%) 2 (3.5%) Dose reductions due to AEs 15 (28%) Treatment discontinuation due to AEs 4 (7%) Bachelot et al. J CLin Oncol 2012. Epub 1-7.

BOLERO-2: Everolimus in Postmenopausal, Hormone Receptor Positive ABC Postmenopausal ER+ HER2- breast cancer pts refractory to letrozole or anastrozole Everolimus 10 mg/day + Exemestane 25 mg/day (N = 485) Primary PFS Secondary OS ORR Bone Markers Safety PK Placebo + Exemestane 25 mg/day (N = 239) Stratification: Sensitivity to prior hormonal therapy Presence of visceral disease No cross-over Baselga J, et al. N Engl J Med 2012;366(6):520-9. 30

BOLERO-2: Baseline Characteristics Everolimus + Exemestane (N = 485), % Placebo + Exemestane (N = 239), % Median age (range), years 62 (34, 93) 61 (28, 90) Race Caucasian 74 78 Asian 20 19 Performance status 0 60 59 Liver involvement 33 30 Lung involvement 29 Measurable disease* 70 68 *All other patients had ≥ 1 bone lesion. Baselga J, et al. N Engl J Med 2012;366(6):520-9. 31

BOLERO-2: Prior Therapy Everolimus + Exemestane (N = 485), % Placebo + Exemestane (N = 239), % Sensitivity to prior hormonal therapy 84 Last treatment: LET/ ANA 74 75 Last treatment Adjuvant 21 16 Metastatic 79 Prior tamoxifen 47 49 Prior fulvestrant 17 Prior chemotherapy for metastatic BC 26 24 Number of prior therapies: ≥ 3 54 53 Baselga J, et al. N Engl J Med 2012;366(6):520-9. 32

BOLERO-2 Primary Endpoint: PFS Central Assessment 12 6 18 24 30 36 48 60 42 54 72 66 78 80 40 20 100 Probability of Event (%) Everolimus + Exemestane (E/N=114 / 485) Placebo + Exemestane (E/N=104 / 239) HR = 0.36 (95% CI: 0.27-0.47) Log rank P value = 3.3 x 10 -15 EVE + EXE: 10.6 Months PBO + EXE: 4.1 Months Time (weeks) Everolimus plus exemestane increased progression-free survival by 64% Baselga J, et al. N Engl J Med 2012;366(6):520-9. 33

BOLERO-2: Overall Response Rate and Clinical Benefit Rate by Local Assessment Baselga J, et al. N Engl J Med 2012;366(6):520-9. 34

BOLERO-2: Most Common G3/4 AEs Everolimus + Exemestane (N = 482), % Placebo + Exemestane (N = 238), % All Grades Grade 3 Grade 4 Stomatitis 56 8 11 1 Fatigue 33 3 <1 26 Dyspnea 18 4 9 Anemia 16 5 Hyperglycemia 13 2 AST 6 Pneumonitis 12 Baselga J, et al. N Engl J Med 2012;366(6):520-9. 35

BOLERO-2: Overall Survival As of PFS interim analysis: 83 deaths 10.6% in everolimus arm 13.0% in placebo arm OS interim analysis after 173 events OS final analysis at 392 events 80% power to detect 26% reduction in hazard ratio (0.74) Baselga J, et al. N Engl J Med 2012;366(6):520-9. 36

BOLERO-2: Clinical Implications The PFS of HR+ MBC patients who took everolimus + exemestane had a significantly higher PFS than those who took exemestane alone Everolimus may slow progression of MBC in patients who initially became resistant to endocrine therapy alone

Other Mechanisms of Resistance PI3K Compensatory Pathways

PI3K Compensatory Pathways Rapalogs Activate Akt IGFR-1 Phase I Everolimus Study Tumor pAkt IRS PI3K pre-therapy PIP3 PTEN Akt PDK1 Tuberin on-therapy Rheb 10mg/day 50mg/week TORC1 S6K 4EBP1 S6 Tabernero A, et al. J Clin Oncol. 2008;26(10):1603-1610

PI3K Compensatory Pathways PI3K Inhibitors Activate ERK Pathway via Enhanced RTK Signaling IGFR1 HER2 EGFR P P P P P P P P P P P P PI3K Ras PTEN PIP3 Raf Akt PDK1 MEK Tuberin Erk Rheb Rsk TORC1

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Conclusions The effectiveness of ET is limited by high rates of de novo and acquired endocrine resistance. Resistance to ET is a step-wise progression of BC cells that renders them estrogen-independent Bidirectional crosstalk between the ER and growth factor receptor signaling pathways, such as the PI3K/AKT/mTOR pathway, is implicated in resistance to ET Under the pressure of ET, dynamic interplay between ER and growth factor receptor expression exists that can alter BC cell phenotype Overcoming endocrine resistance remains critical to enhancing further the benefit of existing endocrine therapies.