1) The document discusses sequencing agents for metastatic castration-resistant prostate cancer, including trials comparing androgen deprivation therapy alone versus androgen deprivation therapy plus docetaxel chemotherapy. 2) It reviews recent trials of sipuleucel-T, abiraterone, enzalutamide, cabazitaxel, and radium-223 that have shown improved overall survival compared to controls. 3) It discusses potential mechanisms of resistance to these agents, such as AR-V7 splice variants, and investigational agents like niclosamide that may be effective for patients with resistance.

1. Sequencing Agents in Metastatic Prostate
Cancer
April 9, 2016
Evan Y. Yu, M.D
Associate Professor
Medicine and Oncology
Florida Society of Clinical Oncology Spring Session
Kissimmee, Florida

2. Discussion Topics
• Metastatic hormone-sensitive prostate cancer
• Sequencing agents for metastatic castration-resistant prostate
cancer
• Clinical trials to pave the way for the future
• AR spliced variants
• Some situations where chemotherapy is needed
• Small cell neuroendocrine
• Aggressive variant

3. Investigational and off-label use
• Niclosamide and Olaparib are investigational
• Cabazitaxel is approved for use after docetaxel chemotherapy,
not prior

4. E3805 CHAARTED: ChemoHormonal Therapy vs.
Androgen Ablation for Metastatic Prostate Cancer
Sweeney C et al. N Engl J Med 2015; 373:737-46.
• N=790 men accrued
07/28/06 - 11/21/12
• Planned interim
analysis at 53%
information met 10/13
• 01/16/14 median
followup 29 months
• 136 (110 high volume)
deaths ADT alone vs. 101
(82 high volume) deaths
ADT+D
• 83.6% vs. 83.2% of deaths
from prostate cancer
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
O S (M onths)
0 12 24 36 48 60 72 84
Arm ALIVEDEAD M EDIANTO TAL
Probability
HR=0.61 (0.47-0.80)
p=0.0003
Median OS:
ADT + D: 57.6
months
ADT alone: 44.0
months
Primary endpoint –
Overall survival

5. Sweeney C et al. N Engl J Med 2015; 373:737-46.
E3805 CHAARTED: ChemoHormonal Therapy vs.
Androgen Ablation for Metastatic Prostate Cancer
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
OS (Months)
0 12 24 36 48 60 72 84
Arm ALIVEDEAD MEDIANTOTAL
Probability
p=0.0006
HR=0.60 (0.45-0.81)
Median OS:
ADT + D: 49.2 months
ADT alone: 32.2
months
>4 bone lesions and
>1 lesion in any bony
structure
beyond the spine/pelvis
OR
visceral disease
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
OS (Months)
0 12 24 36 48 60 72 84
Arm ALIVEDEAD MEDIANTOTAL
Probability
p=0.1398
HR=0.63 (0.34-1.17)
Median OS:
ADT + D: Not reached
ADT alone: Not
reached
High volume Low volume
OS by extent of metastatic disease at start of ADT

6. STAMPEDE Overall Survival
SOC 405 deaths
SOC+Doc 165 deaths
HR (95%CI) 0.76
(0.63, 0.91)
P-value 0.003
Non-PH p-value
Median OS (95% CI)
SOC 67m (60, 91m)
SOC+Doc 77m (70, NR)
Restricted mean OS time
SOC 58.8m
SOC+Doc 63.4m
Diff (95%CI) 4.6m (1.8, 7.3m)
James ND et al. Lancet 2016; 387:1163-77.

7. STAMPEDE Overall Survival for M1 Patient
Population (61% of trial population)
SOC 343 deaths
SOC+Doc 134 deaths
HR (95%CI) 0.73
(0.59, 0.89)
P-value 0.002
Non-PH p-value
Median OS (95% CI)
SOC 43m (24, 88m)
SOC+Doc 65m (27, NR)
Restricted mean OS time
SOC 49.3m
SOC+Doc 56.1m
Diff (95%CI) 6.8m (2.8,
11.0m)
James ND et al. Lancet 2016; 387:1163-77.

8. Recent Trials in mCRPC: Overall Survival
Therapy Prior Docetaxel Comparator HR P
Sipuleucel-T Mostly No Placebo 0.775 .032
Docetaxel No Mitoxantrone 0.76 .009
Cabazitaxel Yes Mitoxantrone 0.70 < .0001
Abiraterone/
Prednisone
No Prednisone 0.81 .0033
Yes Prednisone 0.646 < .0001
Enzalutamide
No Placebo 0.706 < .001
Yes Placebo 0.631 < .001
Radium-223 Mostly Yes Placebo 0.70 .002

9. Sipuleucel-T Survival Benefit1
• Sipuleucel-T was approved based on HR of 0.775
(~4-month OS benefit)
• Survival curves separated after 6 months
• Treatment is carried out in 5 weeks
– Few side effects
1. Kantoff PW et al. N Engl J Med. 2010;363:411-422.

10. Median OS, mo
Baseline PSA (n= 128 for all categories)
≤22.1 >22.1–50.1 >50.1–134.1 >134.1
Sipuleucel-T 41.3 27.1 20.4 18.4
Control 28.3 20.1 15.0 15.6
Difference 13.0 7.1 5.4 2.8
HR (CI) 0.51
(0.31-0.85)
0.74
(0.47-1.17)
0.81
(0.52-1.24)
0.84
(0.55-1.29)
Survival Benefit of Sipuleucel-T Is Greater
When PSA Is Lower1
1. Schellhammer PF et al. Urology. 2013;81:1297-1302.
IMPACT: OS by Baseline PSA

11. Abiraterone Acetate: An Androgen Biosynthesis
Inhibitor
1. De Bono JS et al. N Engl J Med. 2011;26:1995-2005. 2. Ryan et al. 2012 American Society of Clinical Oncology
Annual Meeting (ASCO 2012). Abstract LBA4518.
Pregnenolone
DHEA Androstenedione Testosterone DHT
17-OH-
Pregnenolone Cortisol
Aldosterone
Androgens
Cholesterol
Abiraterone
Abiraterone
Abiraterone improved OS and radiographic PFS in patients with
mCRPC post-docetaxel1,2

12. COU-302: Abiraterone/Prednisone vs
Placebo/Prednisone in Chemotherapy-Naïve mCRPC
OS: overall survival; PFS: progression-free survival.
Ryan CJ et al. N Engl J Med. 2013;368:138-148.
Ryan CJ, Smith MR, Fizazi K, Miller K. 39th ESMO 2014. Abstract 7530
Radiographic PFS

13. Abiraterone/Prednisone Reduced Death Risk by 19%
OS: overall survival; PFS: progression-free survival.
Ryan CJ et al. N Engl J Med. 2013;368:138-148.
Ryan CJ, Smith MR, Fizazi K, Miller K. European Society for Medical Oncology 2014 Congress (ESMO 2014).
Abstract 7530.
OS

14. Enzalutamide: An Androgen Receptor Inhibitor
Scher HI et al. N Engl J Med.
2012;367:1187-1197.
Enzalutamide improved OS and radiographic PFS in patients with
mCRPC post-docetaxel1
Enzalutamide
1
T
AR
T
Cell nucleus
Inhibits Binding of
Androgens to AR
Inhibits Nuclear
Translocation of AR
Inhibits Association
Of AR with DNA
AR
Cell cytoplasm
2
3
• No demonstrated
agonist effects in
pre-clinical models

15. PREVAIL: Enzalutamide vs Placebo in
Chemotherapy-Naïve mCRPC
Estimated Median Radiographic PFS, mo (95% CI)
Enzalutamide NYR (13.8-NYR)
Placebo 3.9 (3.7-5.4)
Radiographic PFS
NYR: not yet reached.
Beer TM et al. N Engl J Med. 2014; 371:424-33.

16. Enzalutamide Reduced Risk of Death by 29%
OS
Estimated Median OS, mo (95% CI)
Enzalutamide 32.4 (30.1-NYR)
Placebo 30.2 (28.0-NYR)
Patients still alive at data cut-off
Enzalutamide: 72%; Placebo: 63%
Beer TM et al. N Engl J Med. 2014; 371:424-33.

17. So Which Should Go First?
• There are no data to guide us in choosing
between abiraterone and enzalutamide
• Toxicity considerations
− Abiraterone: Hepatic dysfunction, fluid excess,
hyperglycemia
− Enzalutamide: Seizures, elderly with fatigue
• Unique situations with rapid disease
progression, significant symptoms and/or
visceral disease
− Docetaxel
− Docetaxel/carboplatin for aggressive variants
− Etoposide/cisplatin for neuroendocrine/small cell

18. Practical considerations currently drive what goes
next after Abiraterone or Enzalutamide
• What previous hormonal agents were used and how good
and long were the responses?
• What is the pace of the disease?
• Any visceral lesions?
• Patient tolerance and comorbidities?
• Financial toxicity (eg, patient copay)?
• PATIENT PREFERENCE

19. How Well Does Enzalutamide Work After
Abiraterone and Vice Versa?
• Only small, retrospective studies published, subject to
selection bias
• Incomplete information
• Variable assessment intervals challenge time to event analyses
• Generally advanced, heavily pretreated patients
• Most analyses are in the post-chemotherapy setting
• Significant PSA responses (e.g. >50% decline) are in the 17-27%
range1
• Responses tend to be short
1. Cheng HH et al. Prostate Cancer Prostatic Dis. Epub Jan. 20, 2015.

20. Docetaxel: First Drug in mCRPC to Improve Survival
1. Petrylak DP et al. N Engl J Med. 2004;351:1513-1520.
2. Tannock IF et al. N Engl J Med. 2004;351:1502-1512.
HR: 0.83, P = .03
TAX-3272SWOG 99-161

21. TROPIC: Overall Survival (Updated ITT Analysis)1
1. De Bono J et al. Lancet. 2010; 376:1147-1154.
Mitoxantrone Cabazitaxel
Median OS, mo 12.7 15.1

22. PRIMCAB Study
• Phase 2, randomized, open-label, multicenter study in chemotherapy-naïve
mCRPC patients who have PRIMary resistance to abiraterone acetate or
enzalutamide treatment comparing the antitumor effect of CABazitaxel to
alternative androgen receptor (AR)−targeted therapy
R
A
N
D
O
M
I
Z
E
Cabazitaxel 25 mg/m² Q3W
+ Prednisone 10 mg/d
(n = 137)
• mCRPC patients
who have primary
resistance to
Abiraterone/
Enzalutamide
(PD within 6
months of AR-
targeted therapy)
• N = 274
Switch to a second AR
(Abiraterone 1,000 mg daily +
Prednisone 5 mg BID or
Enzalutamide 160 mg QD)
(n = 137)
• Endpoints
– Primary: rPFS
– Secondary: OS, TTPP, safety
• Statistical plan
– Superiority design with assumption of HR of 0.67

23. AR-V7: An Important Possible Mechanism of
Resistance
• Most abundant AR-spliced
variant
• Constitutively active and
cannot be blocked by
LBD-targeting drugs
• Expression increased around
20-fold in CRPC
− Still minority compared to
FL-AR
FL-AR
AR-V7

24. AR-V7 Detection From CTCs and Subsequent
Response to Abiraterone
CTC: circulating tumor cell.
Antonarakis E et al. N Engl J Med. 2014;371:1028-1038.
* Increase of more than 100% in best PSA response.
† Patients who had previously received enzalutamide.

25. AR-V7 Detection From CTCs and Subsequent
Response to Enzalutamide
* Increase of more than 100% in best PSA response.
† Patients who had previously received abiraterone.
Antonarakis E et al. N Engl J Med. 2014;371:1028-1038.

26. Niclosamide for ARv7 Positive Patients?
• Screen of over 1,100 FDA
approved agents
identified niclosamide as
being able to inhibit AR-
V7 mediated protein
expression
• Decreases AR-V7 protein
levels
– Possibly through enhancing
proteasomal degradation
• Full length AR unaffected
• Also shown to inhibit NF-
κB, Wnt/β-catenin and
mTOR signaling
Liu et al. CCR 2014, Wieland et al. CCR 2013, Khanim et al. Blood 2011. Jin et al. Ca Res 2010, Balgi et al. PLoS one 2009
AR-V7 positive CWR22Rv1 and C4-2B MR cells treated with 0.25 μmol/L
niclosamide with or without 20 μmol/L enzalutamide.
Mice bearing CWR22Rv1 xenografts treated with vehicle control,
enzalutamide, or their combination for 3-weeks.

27. Niclosamide Phase 1 Trial at University of
Washington – PI: M. Schweizer
• Problem is limited bioavailability
(Cmax= 0.25 to 6.0 g/mL) of
niclosamide
• Phase I study to explore
alternative (high, frequent dose)
niclosamide dosing in
combination with enzalutamide
• Patient population:
– AR-V+ (as detected via AdnaTest)
CRPC
– Post-abiraterone
• Primary endpoint:
safety/tolerability
• Secondary endpoints:
– Niclosamide PK
– AR-V status pre-/post-treatment
– Changes in gene expression (RNA-
seq) pre-/post-treatment
A Phase I Study of Niclosamide in Combination with
Enzalutamide Men with Androgen Receptor Splice
Variant Positive Castration-Resistant Prostate Cancer
Enrollment Assess AR-V status
28-days
Enzalutamide 160 mg
PO daily
Niclosamide:
Cohort 1: 500 mg PO TID
Cohort 2: 1000 mg PO TID
Cohort 3: 1500 mg PO TID

28. Genomic Landscape of Metastatic Castration-
Resistant Prostate Cancer
Robinson D et al. Cell 2015; 161:1215-28.
• 23% of metastatic castration-resistant prostate cancers harbor DNA repair alterations
• 2.7% are MLH1 or MSH2, which are consistent with MSI

29. DNA Repair Defects Predict Response to A
PARP Inhibitor, Olaparib
• Overall response rate of 32.7% -- median duration of response ~ 9 months
• 14/16 (88%) of patients with a DNA repair alteration had a response
• 2/33 (6%) of patients without a DNA repair alteration had a response
Mateo J. et al, N Engl J Med 2015; 373:1697-708.

30. rPFS by presence of genomic
defects in DNA repair genes
OS by presence of genomic
defects in DNA repair genes
P<0.001
Biomarker negative:
median 7.5 months
Biomarker positive:
Median: 9.8 months
Biomarker
negative:
median 2.7 months
Response to Olaparib is Highly Enriched in
Patients with Defects in DNA Repair Genes
Mateo J. et al, N Engl J Med 2015; 373:1697-708.
Biomarker positive:
Median: 13.8 months
P=0.05

31. BRCA2 and Platinum Chemotherapy
• ATM and BRCA-mutated mCRPC with Carboplatin and Docetaxel
(ABCD trial)
• Identified by tumor NGS to have biallelic inactivation of:
BRCA1/2, n= 14 or ATM or other homologous DNA repair gene,
n=any
• Primary endpoint: rate of PSA50
0
2
4
6
8
10
12
PSA(ng/mL)
CAR
+DOC
ABI CAR CIS
+ETO
PAC
30 months
CAR
+DOC
2011 2012 2013 2014
BRCA2
homozygous
copy loss
4
2
1
0
CopiesofGene
Cheng HH et al. Eur Urol 2015; Epub Dec 24, 2015.

32. Radium-223: Overall Survival1
• N = 922
• Confirmed
symptomatic CRPC
• ≥2 bone metastases
• No known visceral
metastases
• Post-docetaxel or
unfit for docetaxel
1. Parker C et al. N Engl J Med. 2013;369:213-223.

33. ALSYMPCA Updated OS Analysis by
Stratification Variables: Prior Docetaxel Use1
1. Hoskin P et al. Lancet Oncol. 2014;15:1397-1406.
OS, Previous Docetaxel Use OS, No Previous Docetaxel Use

34. Radium-223 Before or After Chemotherapy?
Practical Considerations
• Only FDA-approved for patients who lack visceral
metastasis
• Stringent eligibility requirements for treatment
– Initial ANC ≥1,500/L with subsequent ≥1,000/L
– Hb ≥10 g/dL
– PLT ≥100,000/L with subsequent ≥50,000/L
• Requires pre-authorization, while chemotherapy with
docetaxel does not
ANC: absolute neutrophil count; Hb: hemoglobin; PLT: platelets.

35. Using PET to Study Mechanisms of Drug Resistance:
Trial Schema – PI: Ramos/Yu
• Initial studies will be in patients
receiving radium-223
PIs: Ramos, Yu
PET1
Begin
treatment
PET2a PET3
a In some cases, PET2 may show progression of disease and in those instances, would represent PET3 in this schema.
This scan will occur at 12 weeks ± 2 weeks from initiation of therapy.
b Survival monitoring will occur in 3-month intervals.
PET: positron-emission tomography.
Eligibilityassessment
andinformedconsent
Survival
monitoringb
Pretreatment
metastatic biopsy, if
appropriate
Metastatic biopsy, if
appropriate
Metastatic biopsy, if
appropriate and not
done after PET2

36. What might trigger me to perform a metastatic biopsy?
• Visceral lesions esp. liver metastasis
• Extremely bulky lymph nodes (>5cm)
• Low PSA in the setting of very high volume disease
• Predominantly lytic rather than blastic bone
metastases

37. • De novo presentation rare (<1% new diagnoses)
• May arise as a mechanism of resistance to ADT
• Metastatic disease, including unusual sites of metastases
• Low or modestly rising PSA
• Paraneoplastic syndromes (uncommon)
• Elevated CEA or serum neuroendocrine markers (chromogranin, neuron
specific enolase) can support the diagnosis
• Tissue IHC expresses chromogranin A and synaptophysin
• Treated like small cell lung cancer (platinum-doublet chemotherapy, e.g.
cisplatin or carboplatin with etoposide)
Neuroendocrine/Small cell prostate cancer

38. Overall Summary
• There is yet no definitive data to guide us as to how to sequence our
newer therapies, but there are pragmatic considerations that can be
taken into account
• Many clinical trials are underway that may address sequencing, explore
novel combinations and address biologic mechanisms of resistance
• AR-V7 warrants further evaluation as a potential predictive biomarker
• DNA damage genes like BRCA2, BRCA1, ATM, etc. may have an
important role in prostate cancer, both for genetic and familial
screening and therapeutic selection
• The newer potent AR targeted therapies could be leading to aggressive
variant and small/cell neuroendocrine prostate cancers, and both
biologic and therapeutic discovery is needed for this emerging field

39. Acknowledgements
Heather H. Cheng
Acknowledgements
• Emmanuel Antonarakis (Johns Hopkins)
• Matthew Galsky (Mt. Sinai)
• Elisabeth Heath (Wayne State)
• Ulka Vaishampayan (Wayne State)
• Pryzemslaw Twardowski (City of Hope)
• Sumanta Pal (City of Hope)
• Neeraj Agarwal (University of Utah)
• Himisha Beltran (Weill-Cornell)
Funding Sources
PNW SPORE
PCF
DOD PCCTC
Dendreon
Bayer
Michael T. Schweizer
Jorge D. Ramos