1. Overcoming Resistance in Hormonally Sensitive Breast Cancer Ruth M. O’Regan, MD Associate Professor, Hematology and Medical Oncology Emory University School of Medicine Director, Translational Breast Cancer Research Program Director, Hematology and Medical Oncology Fellowship Program Winship Cancer Institute Atlanta, Georgia Clinical Updates Hormonally Sensitive, Early-Stage Breast Cancer

2. Mechanisms of SERM Resistance Johnston CCR 2005 ER Target Gene Transcription SOS PP PP PI3-K Akt P P RAS RAF MEK MAPKp90 RSK ER P p160 Basal Transcription Machinery CBP ER P P P ERE Cell Growth Plasma Membrane Cytoplasm Nucleus E2 SERD AI T IGF1R EGFR/HER2 Increased signaling through PI3-K pathway CCI RAD MoAb TKI Increased upstream signaling through EGFR and/or IGF-IR and or VEGFR TKI AB VEGFR MoAb TKI Mechanisms of intrinsic and acquired resistance is likely similar

3. Copyright ©2003 by the National Academy of Sciences ER+ Cancers Are Heterogenous in Outcome Sorlie et al PNAS 2003 ER +

4. Efficacy of Tamoxifen Varies in ER+ Cancers Low Risk (RS<18) N 171 142 Int Risk (RS 18-30) N 85 69 Interaction P=0.06 High Risk (RS≥31) N 99 79 024681416 Years 0.0 0.2 0.4 0.6 0.8 1.0 DRFS Placebo Tamoxifen 12 10024681416 Years 0.0 0.2 0.4 0.6 0.8 1.0 DRFS Placebo Tamoxifen 12 10024681416 Years 0.0 0.2 0.4 0.6 0.8 1.0 DRFS Placebo Tamoxifen 12 10 Paik et al SABCS 2004 TAM-resistant

5. Correlation Between Recurrence Score and Intrinsic Subtype Recurrence Score Luminal A (n = 123) Luminal B (n = 55) Low621 Intermediate254 High3650 Fan et al NEJM 2006

6. Oncotype DX 21 Gene Recurrence Score (RS) Assay PROLIFERATION Ki-67 STK15 Survivin Cyclin B1 MYBL2 ESTROGEN ER PR Bcl2 SCUBE2 INVASION Stromolysin 3 Cathepsin L2 HER2 GRB7 HER2 BAG1GSTM1 Reference Beta-actin GAPDH RPLPO GUS TFRC CD68 16 Cancer and 5 Reference Genes From 3 Studies CategoryRS (0 – 100) Low riskRS < 18 Int riskRS ≥ 18 and < 31 High riskRS ≥ 31

7. Poor Outcome for Patients with HER2-positive MBC Treated with Endocrine Agents Alone AgentClinical BenefitPFS Anastrozole28%2.4 months Letrozole29%3.0 months Kaufmann ESMO 2006, Johnston SABCS 2008

8. Cui, X. et al. J Clin Oncol; 23:7721-7735 2005 Overall Survival According to Tumor Receptor Status in Women Treated with Tamoxifen PR is prognostic or predictive for patients treated with tamoxifen

9. Disease-free Survival by Ki-67 LI in BIG-1-98 (Letrozole and Tamoxifen) 1,252 (47%) expressed Ki-67 LI > 11% (high) Viale G et al. SABCS 2007 Abs 64.

10. Possible Surrogate Markers for Hormone Resistance ER PR HER2 LUM A LUM B Low Ki-67 High Ki-67 Hormone-sensitive Hormone-resistant RS

11. Mechanisms of SERM Resistance Johnston CCR 2005 ER Target Gene Transcription SOS PP PP PI3-K Akt P P RAS RAF MEK MAPKp90 RSK ER P p160 Basal Transcription Machinery CBP ER P P P ERE Cell Growth Plasma Membrane Cytoplasm Nucleus E2 SERD AI T IGF1R EGFR/HER2 Increased signaling through PI3-K pathway CCI RAD MoAb TKI Increased upstream signaling through EGFR and/or IGF-IR and or VEGFR TKI AB VEGFR MoAb TKI

12. Copyright ©2008 American Association for Cancer Research Massarweh, S. et al. Cancer Res 2008;68:826-833 Increase in EGFR and HER2 Protein in Tamoxifen-resistant Breast Cancers in vivo

13. TAnDEM Study Design Crossover to receive trastuzumab was actively offered to all patients who progressed on anastrozole alone HER2-positive, HR+ MBC (n=208) R Anastrozole 1 mg daily + Trastuzumab 4 mg/kg loading dose  2 mg/kg qw until disease progression Anastrozole 1 mg daily until disease progression HR, hormone receptor; MBC, metastatic breast cancer; R, randomisation

14. Trastuzumab + AI Progression-free Survival 103483117141311941100 A + T 10436229542100000 A CI, confidence interval PFS = time from randomisation to date of progressive disease or death Probability 1.0 0.8 0.6 0.4 0.2 051015202530354045505560 Months 95% CI 3.7, 7.0 2.0, 4.6 P value 0.0016 Median PFS 4.8 months 2.4 months Events 87 99 0.0 No. at risk Kaufmann ESMO 2006

15. Patients (%) 0 10 20 30 40 50 60 P=0.026 Clinical benefit A + T (n=103) A (n=104) Trastuzumab + AI Clinical benefit 42.7% 27.9% Vogel JCO 2002, Kaufmann ESMO 2006 Clinical benefit with single agent trastuzumab 48%

16. Johnston et al., SABCS 2008, abstract 46 1° endpoint: PFS (investigator) in HR+/HER2 pts Letrozole ± Lapatinib in HR+ MBC Arm A: LAP 1,500 mg/d p.o.+ LET 2.5 mg/d p.o. (n = 642) Arm B: LET 2.5 mg/day p.o.+ Placebo (n = 644) (n = 1,286) RANDOMIZERANDOMIZE Eligibility criteria: Postmenopausal ER+/PgR+ HER2+/HER2-/unknown Stage IIIb, IIIc, and IV breast cancer No prior treatment for metastatic disease

17. Johnston et al., SABCS 2008, abstract 46 ITTHER2+HER2- let (n=644) let + lap (n=642) let (n=108) let + lap (n=111) let (n=474) let + lap (n=478) PFS (months) 10.811.93.08.213.413.7 HR 0.86; P =.026HR 0.71; P =.019HR 0.90; P =.188 ORR 28%30%15%28%32%33% P =.262P =.021P =.726 CBR 51%56%29%48%56%58% P =.096P =.003P =.761 OS (months) NR 32.333.3NR HR 0.74; P =.113NR Letrozole ± Lapatinib in HR+ MBC

18. Progression-free Survival HER2+ Population LET (N = 108) LET+ LAP (N = 111) Progressed or died89 (82%)88 (79%) Median PFS, mo3.08.2 Hazard ratio (95% CI)0.71 (0.53, 0.96) P-value0.019

19. Progression-free Survival ITT and HER2-ve Populations LET (N = 474) LET + LAP (N = 478) Progressed or died342 (72%)294 (62%) Median PFS, mo13.413.7 Hazard ratio (95% CI)0.90 (0.77, 1.05) P-value0.188 LET (N = 644) LET + LAP (N = 642) Progressed or died476 (74%)413 (64%) Median PFS, mo10.811.9 Hazard ratio (95% CI)0.86 (0.76, 0.98) P-value0.026 ITTHER2-ve * *Centrally confirmed

20.  Preplanned stepwise exploratory Cox proportional hazard analysis for PFS: –HER2+ population: HR for treatment = 0.65; P =.008 –HER2(-) population: HR for treatment = 0.77; P =.010  PFS in HER2(-) population based on interval since adjuvant TAM therapy ≥6 months since discontinuation of TAM or none <6 months since discontinuation of TAM LET (n=370) LET + LAP (n=382) LET (n=104) LET + LAP (n=96) Median PFS (months) 15.014.73.18.3 HR 0.94; P =.522HR 0.78; P =.117 CBR 64%62%32%44% Johnston et al., SABCS 2008, abstract 46 Hormone-sensitiveHormone-refractory Letrozole ± Lapatinib in HR+ MBC

21. Phase II Anastrozole ± Gefitinib in Newly Diagnosed HR+ MBC Cristofanilli M, et al. J Clin Oncol. 2008;26(15S): Abstract 1012. Post menopausal women Newly diagnosed, ER and / or PR-positive MBC, No prior hormonal therapy, measurable disease Anastrozole 1 mg PO daily Gefitinib 250 mg PO Daily Anastrozole 1 mg PO daily Placebo  Multi-center, randomized, double-blind trial  Primary objective: PFS  Enrollment stopped early due to low accrual R

22. Anastrozole ± Gefitinib in HR+ MBC Efficacy Cristofanilli et al, ASCO 2008, abstract # 1012 Anastrozole + Gefitinib (n = 43) Anastrozole + placebo (n = 50) Median PFS (months) 14.58.2 HR (95% CI) = 0.55 (0.32 – 0.94) Objective response rate2%12% Clinical benefit rate49%34%

23. Pollak et al Nature Reviews 2004 IGF-1R Signaling

24. Role of IGF-1R Signaling in HR+ Breast Cancer  TAM initially inhibits IGF-1 but with the onset of resistance IGF-1R signaling is re-established  TAM-resistant cancers are more sensitive to IGF-1R signaling  Inhibitors of IGF-1R (TKI and mAB) prevent growth of TAM-resistant cells Knowlden et al Endocrinology 2005 Massarweh, S. et al. Cancer Res 2008

25.  Metastatic breast cancer  At least 1 prior endocrine Rx for ≥ 3 months  Disease progression within 12 months of starting last endocrine therapy ER and/or PR- positive IMC-A12 (n = 30) IMC-A12 + most recent endocrine therapy (n = 60) Randomized Phase II Trial of IMC-A12 ± Hormonal Therapy in Hormone-resistant Metastatic Breast Cancer IMC-A12 10 mg/kg every 2 weeks R

26. Pilot Study of Letrozole + Bevacizumab MSKCC/UCSF  N = 43  Primary endpoint: Safety/feasibility  Secondary endpoints: TTP, RR, SD > 6 mo.  Prior NS-AI allowed if no documented progression  Ovarian suppression allowed (medical or surgical) 2.5 mg orally each day Week 0369 Bevacizumab 15 mg/kg IV Letrozole 12 Traina, Dickler, Rugo, Hudis et al., ASCO Abstract 3050, 2006

27. Best Response by RECIST Feasibility Study of Letrozole Plus Bevacizumab n (%) Assessed for Response43 Complete Response 0 (0%) Partial Response 4 (9%) Stable Disease > 24 weeks 29 (67%) Clinical Benefit Rate33 (76%) Median # cycles/patient (range): 13 (1-56) Prior Rx on a NS-AI for MBC (median/range): 15 wks (1-126 wks) Dickler ASCO Breast 2008

28. Progression-free Survival Dickler ASCO Breast 2008 Time (months) from Treatment start Progression-free survival 012243648 0.0 0.2 0.4 0.6 0.8 1.0 N = 43 Median PFS: 17.1 months [95% CI: (8.5, 26.2)] Median wks on AI therapy pre-bevacizumab = 15.4 weeks (range 1-216 wks)

29. RANDOMIZERANDOMIZE Endocrine Rx + Bevacizumab (15 mg/kg IV q 3 wks) Endocrine Rx + Placebo Proof of Concept Study CALGB 40503 First-line Endocrine Rx ± Bevacizumab for MBC  Primary Endpoint: Progression-free Survival  Endocrine Rx: Physician choice of Letrozole or Tamoxifen  For premenopausal women → ovarian suppression required (can start day 1 of protocol therapy)  Correlative studies: CTCs/CECs, pharmacogenomics, differential response by luminal subtyping and PIK3CA mutation analysis N = 442

30. Conclusions  HR+ cancers are clearly heterogeneous with divergent outcomes  Need to identify robust predictive factors for both luminal A and B cancers  Essential to establish molecular differences between luminal subtypes so that novel therapeutic approaches can be developed