Transcript Genomic approaches to enhance sensitivity to double

Targeting DNA repair defects in gynecologic cancers:
BRCA, BRCAness and beyond
Panagiotis Konstantinopoulos MD, PhD
Assistant Professor of Medicine
Harvard Medical School
Medical Gynecologic Oncology Program
Dana Farber Cancer Institute
1. Defective DNA repair pathways in
gynecologic cancers
DNA Damage Repair Pathways
Aziz et al. / Pharmacology & Therapeutics 133 (2012) 334–350
Homologous Recombination DNA Repair Pathway
Hereditary Breast Ovarian Cancer (HBOC) Syndrome
 Associated with germline mutations in BRCA1/2 genes and characterized by a
familial clustering of breast and epithelial ovarian cancers (EOCs)
 Accounts for 10-15% of all ovarian cancers, although its frequency is much
higher among Ashkenazi Jewish women with EOC (29%-41%)
 The National Comprehensive Cancer Network guidelines for breast and ovarian
genetic risk assessment currently recommend referral for genetic testing for
HBOC syndrome for every woman diagnosed with ovarian, fallopian tube or
primary peritoneal serous cancer
 Other cancers that may be part of HBOC syndrome are gastric, pancreatic,
prostate and uterine cancers (BRCA1 carriers) and melanoma, gastric,
pancreatic, prostate and biliary duct cancers (BRCA2 carriers)
Ovarian Cancer and HR defects
BRCA1
germline
8%
BRCA2
germline
6%
As many as 50% of high
BRCA1
somatic
3%
BRCA2
somatic
3%
grade serous ovarian
cancers have defective HR
BRCA1
methylation
11%
DNA repair pathway
EMSY ampl
6%
PTEN loss
5%
other HRD
7%
Fingerprint of HR pathway alterations in ovarian cancer
Cancer Genome Atlas Research Network.
Nature, 2011 Jun 29;474(7353):609-15
Platinum damage and DNA repair
Cisplatin
Intrastrand
Interstrand
cross-links
Nucleotide
Excision
Repair (NER)
Homologous
Recombination
(HR)
NER pathway alterations
 NER pathway alterations are present in 8% of high grade serous tumors.
 NER alterations confer a clinical phenotype of platinum sensitivity similar to that
of BRCA1/2-mutations in ovarian cancer.
 NER alterations are functionally associated with platinum sensitivity but do not
confer sensitivity to PARPis or other double strand break inducing agents.
 NER alterations is a novel mechanism of platinum sensitivity in ovarian cancer.
Mismatch Repair Pathway
HNPCC (Lynch) Syndrome
 Associated with development of multiple cancer types at an early age,
particularly colon, uterine and ovarian cancer
 Caused by a germline mutation in MSH2, MLH1, MSH6, PMS2 genes
 MSH2 or MLH1 mutations account for 90% of Lynch syndrome, MSH6 most of
the rest and PMS2 are very rare
 Lynch syndrome accounts for 2-5% of all uterine carcinomas and about 1-2% of
ovarian cancers
 The majority of Lynch syndrome-associated uterine cancers are endometrioid
histology
 Lynch syndrome has been associated with all subtypes of ovarian cancer
Risks of uterine and ovarian cancer in Lynch syndrome
Uterine Cancer and Mismatch Repair Defects
Defective MMR occurs in 2035% of all uterine tumors (i.e.
not only Lynch syndrome)
This can happen through
various mechanisms that
usually do not involve mutations
in MMR genes
Uterine Cancer and BRCA1/2
 There have been some reports of an increased risk of the serous
subtype of uterine cancer in BRCA carriers.
 In one report, 4 of 20 Ashkenazi Jewish women with USC had
BRCA1 germline mutations
 In another, three BRCA1 and three BRCA 2 germline mutations were
identified among 22 Jewish women with USC
2. Targeting defective DNA repair pathways in
gynecologic cancers
Development of PARP inhibitors
Interaction between BER and HR repair pathways
A cell CAN survive if ONLY the homologous recombination (HR)
pathway OR ONLY the base excision repair pathway (BER) is defective
BUT
CANNOT survive if BOTH pathways are defective
Synthetic lethality between HR and BER
HR pathway
BER pathway
Base Excision Repair (BER)
PARP-inhibitors (Synthetic Lethality)
Selected trials of olaparib in BRCA carriers in EOC
Agent
Design
Patients
Results
Olaparib
Phase I
15 BRCA carriers
8/15 (53%) had objective response per RECIST
criteria and 1 had stable disease for 6 months
50 BRCA carriers
40% ORR and/or CA125 (>50% decline)
Clinical benefit in platinum-sensitive, resistant, and
refractory subgroups (69%, 45%, and 23%,
respectively)
Olaparib
Phase I
33 BRCA carriers
(400mg po bid)
Olaparib
Phase II
24 BRCA carriers
(100mg po bid)
Olaparib
versus
Doxil
Randomized
Phase II
97 BRCA carriers
ORR: 33% at 400 mg bid and 13% at 100 mg bid
Median PFS : 5.8 mos at 400mg bid and 1.9 mos
at 100mg bid
Objective response rate per RECIST was 25% for
200mg po bid dose and 31% for 400mg po bid.
PFS was 6.5 and 8.8 months respectively
Fong et al. NEJM, 2009; Fong et al. JCO, 2010;
Audet et al. Lancet, 2010; Kaye et al. JCO, 2012
Concept of “BRCAness”
 A subset of sporadic ovarian tumors appear to share defects in
homologous recombination (HR) DNA repair with tumors that arise in
BRCA1/2 germline mutation carriers
 Such sporadic tumors may behave similarly to those with BRCA germline
mutations and are referred to as having a “BRCAness” phenotype
characterized by:
 Heightened sensitivity to platinum analogues and PARP inhibitors
(PARPis)
 Improved survival compared to their sporadic counterparts
Turner et al Nat Rev Cancer. 2004 Oct;4(10):814-9
Ovarian Cancer and HR defects
BRCA1
germline
8%
BRCA2
germline
6%
As many as 50% of high
BRCA1
somatic
3%
BRCA2
somatic
3%
grade serous ovarian
cancers have defective HR
BRCA1
methylation
11%
DNA repair pathway
EMSY ampl
6%
PTEN loss
5%
other HRD
7%
Olaparib in pts with negative or unknown BRCA-status
Agent
Design
Phase II, open
Olaparib
label, multicenter,
non randomized
study
Patients / Dose
17 BRCA-associated EOCs
46 sporadic EOCs
(400mg twice daily)
Results

BRCA-associated EOCs ORR: 41%
(Plat Sens: 60%, Plat Res: 33%)

Sporadic-EOC ORR: 24%
(Plat Sens: 50%, Plat Res: 4%)
265 high grade EOC patients
with unknown BRCA-status
Olaparib
Maintenance
Vs
Placebo
Randomized,
double-blind,
placebocontrolled, phase
2

Adverse events with an incidence that was at least 10%
who had received two or more
higher in the olaparib group than in the placebo group,
platinum based regimens and
were nausea, fatigue, vomiting, and anemia
had had a partial or complete 
A complete response (vs. partial response) to the final
response to their most recent
platinum-based therapy was
platinum-based regimen
progression-free survival, regardless
136: olaparib 400mg twice
daily
129: placebo
associated with longer
of study group

Interim OS analysis no difference between two arms
Biomarkers of BRCAness (Genomic Scars)
Lord et al Nature. 2012;481:287-294
Combinations of PARP inhibitors with other drugs
Combination of PARPis with antiangiogenic drugs
Tentori et al Eur J Cancer 2007; 43:2124-33
Combination of PARPis with PI3K inhibitors
Juvecar et al Cancer Discovery. 2012; 2:1048-63
Development of resistance to PARP inhibitors
1. Secondary mutations in BRCA1-associated tumors
Swisher et al. Cancer Res 2008
2. Secondary mutations in BRCA2-associated tumors
Sakai et al. Nature 2008
3. Loss of 53BP1 in BRCA1-associated tumors
4. Increased expression of p-glycoprotein efflux
transporter mediating multi-drug resistance
Is it possible to use PARPis in patients that have
intact HR or those who have developed resistance to
PARPis?
Evaluation of synergism between 17AAG and olaparib
36M2 w/ Olaparib + 17AAG
OVCAR5 w/ Olaparib + 17AAG
140
120
120
100
80
NO 17AAG
60
0.01uM 17AAG
Cell Viability (%)
Cell Viability (%)
100
80
NO 17AAG
60
0.01uM 17AAG
40
40
20
20
0
0
0
5
10
Olaparib (uM)
15
20
0
5
10
Olaparib (uM)
15
20
1.
2.
IC50
IC50
BRCA1 mut / PARPi
resistant
CDKN2A loss
CDKN2A loss
CCNE1 amplification
Targeting cell cycle checkpoints
Conclusions (I)
 DNA damage repair pathways are frequently deregulated in gynecologic cancers
both as hereditary cancer syndromes as well as sporadic tumors
 Defective DNA damage repair offers cancer cells genomic instability that allows
them to break and reform chromosomes, generate new oncogene fusions and
mutations, inactivate tumor suppressor genes, and consequently become more
malignant and progress
 At the same time, defective DNA repair pathways provide exciting opportunities
for anticancer therapies (e.g. chemotherapy, XRT, etc)
Conclusions (II)
 PARP inhibitors are exciting new drugs that target DNA repair pathways and
have shown promising activity in ovarian cancer
 Identifying patients who benefit from PARP inhibitors is an active area of
investigation
 Combinations of PARP inhibitors with other drugs may enhance sensitivity and
overcome resistance to these agents
 Checkpoint inhibitors are exciting novel agents against ovarian cancer