PARP inhibition basic science and clinical challenge. Thomas Helleday, PhD

Transcription

1 PARP inhibition basic science and clinical challenge Thomas Helleday, PhD

2 Poly (ADP-ribose) Polymerase 1 (PARP1) Reprinted by permission from Macmillan Publishers Ltd: Rouleau M et al. Nat Rev Cancer 2010;10: copyright (2010)

3 PARP family of proteins DNA repair Reprinted by permission from Macmillan Publishers Ltd: Schreiber J et al. Nat Rev Mol Cell Biol 2006;7: copyright (2006)

4 DNA damage/nad + levels dictate responses Ström CE and Helleday T. Biomolecules 2012;2: by permission of CCPL (2012)

5 PARP1 is critical for efficient SSB repair DNA single-strand break PARP1 Polβ PNKP APTX Lig3 XRCC1 XRCC1 Ligase3 PNKP, APTX PCNA, Polδ/ε, Polβ, Ligase1, FEN1 Polβ Lig3 XRCC1 short patch Lig3 XRCC1 PCNA Polδ/ε Polβ FEN1 Lig3 XRCC1 Lig1 long patch PCNA Lig1 Ström CE et al. Nucleic Acids Res 2011;39: by permission of Oxford University Press

6 BRCA2 deficient cells are killed by PARP inhibitors V-C8+B2 V-C8 gh2ax + DNA gh2ax g BRCA2 defective HR Reprinted by permission from Macmillan Publishers Ltd: Bryant HE et al. Nature 2005;434(7035): copyright (2005); Farmer H et al. Nature 2005;434(7035):

7 Specific killing of BRCA2 deficient tumours with PARP inhibitors Relative thigh circumference Days post implant AG mg/kg V-C8+B2 control V-C8+B2 AG14361 V-C8 control V-C8 AG14361 Reprinted by permission from Macmillan Publishers Ltd: Bryant HE et al. Nature 2005;434(7035): copyright (2005)

8 Synthetic lethality as an approach for anti-cancer treatments Cancer cells Normal cells PARP Inhibition PARP Inhibition SSB repair Homologous Recombination SSB repair Homologous Recombination BRCA2+/- BRCA2-/- Cell Survival death Survival Helleday T.

9 PARP inhibitors in monotherapy

10 PARP inhibitors in treatment for BRCA1/2 cancer >80 clinical trials with PARP inhibitors in phase I-II Progressive disease Stable disease Partial response Complete response 80 Ovarian cancer Prostate cancer Breast cancer Treatment duration (week) From Fong PC et al. New Engl J Med 2009;361(2): Copyright (2009) Massachusetts Medical Society. Reprinted with permission from Massachusetts Medical Society

11 PARP inhibitors in treatment for BRCA1/2 ovarian cancer Olaparib 400 mg twice daily Olaparib 100 mg twice daily Reprinted from Audeh MW et al. Lancet 2010;376(9737): Copyright (2010), with permission from Elsevier

12 Response to PARP inhibitors in triple negative breast cancer is dictated by BRCA mutation Olaparib 400 mg twice daily Reprinted from Gelmon KA et al. Lancet Oncol 2011;12(9): Copyright (2011), with permission from Elsevier

13 Platinum resistant ovarian cancers and non-brca respond to PARP inhibitor Reprinted from Gelmon KA et al. Lancet Oncol 2011;12(9): Copyright (2011), with permission from Elsevier

14 Olaparib maintenance treatment improve progression-free survival in relapsed high-grade serous ovarian cancer 1.0 Probability of progression-free survival Olaparib Placebo Months since randomization Hazard ratio, 0.35 (95% CI, ) P<0.001 Adapted from Ledermann J et al. N Engl J Med 2012;366(15):

15 Ovarian cancers often have silenced Fanconi anemia (FA) pathway, rendering in homologous recombination defect PARP-sensitive tumour PARP-resistant tumour? Reprinted by permission from Macmillan Publishers Ltd: Taniguchi T et al. Nat Med 2003;9(5): copyright (2003)

16 Biomarkers for PARP inhibitor sensitivity in monotherapy? BRCA1/2 mutation Silenced or mutated BRCA related genes PARP1 protein levels or PARP activity Functional homologous recombination assay (RAD51 foci, FA status) RNA/DNA signatures correlating with BRCA status BRCA mutational signature

17 Resistance to PARP inhibitors Cancer cells PARP inhibitor BRCA2 mutation Cell Survival Death Resistant clone Rottenberg S et al. Proc Natl Acad Sci U S A 2008;105(44): ; Reprinted by permission from Macmillan Publishers Ltd: Sakai W et al. Nature 2008;451: copyright (2003)

18 Complicity of genetic networks 53BP1 loss as resistance mechanism Ancestrial suppressed network 53BP1 BRCA PARPi Reprinted from Bunting SF et al. Cell 2010;141: Copyright (2010), with permission from Elsevier

19 PARP inhibitors in combination therapy

20 Iniparib plus chemotherapy in metastatic triple-negative breast cancer Overall survival (%) Gemcitabine-carboplatin alone Hazard ratio for death with iniparib, 0.57 (95% CI, ) P=0.01 Gemcitabine-carboplatin plus iniparib Months Adapted from O'Shaughnessy J et al. N Engl J Med 2011;364(3):

21 Reasons for phase III to fail? Iniparib plus chemotherapy in metastatic triple-negative breast cancer Phase II design (open label) Combination with gem-carbo? No selection for BRCA mutated patients? Iniparib is not a PARP inhibitor O'Shaughnessy J et al. N Engl J Med 2011;364(3): ; Reprinted from Patel AG et al. Clin Cancer Res 2012;18: , with permission from AACR

22 Rucaparib (PF , AG014699), with temozolomide in patients with metastatic melanoma Survival probability Kaplan Meier Plot with number of subjects at risk Censored 95% Confidence limits Overall survival (months) Best % tumour shrinkage from baseline Patient Conclusion: This study show that temozolomide ( mg/m 2 /day) can safely be given with a PARP inhibitory dose of rucaparib, increasing progression-free survival over historical controls in metastatic melanoma patients Redrawn from Plummer R et al. Cancer Chemother Pharmacol 2013;71(5):

23 a normal no DNA damage PARP inhibitors have no clinical benefit Strategies using PARP inhibitors as anti-cancer agents - overview b normal c normal BRCA mut replication stress PARP inhibitors selectively toxic to BRCA mut cancer PARP inhibitors with some toxicity to DNA damaged cancer cells Potentiating chemotherapy Synthetic lethality d replication stress +chemo PARP active PARP inhibitors sensitise all cells to chemotherapy no clinical benefit Combined with targeted therapies Enhance cancerspecific DNA damage Context specific synthetic lethality High PAR PARP activity stained by PAR polymers e replication stress f DNA damage stress g DNA damage stress +chemo not PARP activate +CDK1 inhibitor hypoxia PARP inhibitors + chemotherapy work with additive effect, potential clinical benefit Targeted inhibitors activate PARP in cancer, PARP inhibitors have clinical benefit hypoxia activates PARP in cancer, PARP inhibitors may have clinical benefit Low PAR Helleday T. Curr Opin Oncol 2013;25:

24 What combination will work in the clinic depends on tumour characteristics and drug mechanism of action Therapy DNA repair inhibitor Value Comment PRIMARY TUMOUR Receptor negative cancer, p53 mutated and Fanconi s anemia (FA) silenced - Platinum-based chemo Platinum-based chemo Platinum-based chemo Platinum-based chemo Temozolomide Radiotherapy PARP inhibitor PARP inhibitor Proteasome inhibitor DNA-PK inhibitor Non-FA crosslink inhibitor PARP inhibitor ATR/Chk1 inhibtor FA silenced cells exhibit decreased homologous recombination and sensitivity to PARP inhibitors FA silenced cells are sensitive to both platinum-based chemo and PARP inhibitors, which cause different DNA lesions, additive effect with both treatments, some normal tissue toxicity. Proteasome inhibitors inhibit FA-mediated crosslink repair. Preferential induction of normal tissue toxicity. Sensitivity to crosslinking agents in FA-silenced cells depend on active DNA-PK activity. Cancer cells become selectively resistant to platinum-based chemo. FA silenced cells rely on non-fa mediated repair for survival, which normal cells do not. This pathway not yet identified. Temozolomide not standard in ovarian cancer, PARP activity required for normal cell survival. Risk of potentiating side effects. ATR/Chk1 inhibitors sensitises to radiotherapy and are especially active in p53 mutated cancer. Furthermore, FA silenced cells exhibit replication lesions requiring ATR/Chk1 for survival RESIDUAL TUMOUR Platinum resistant by DNA-PK loss Doxorubicin Paclitaxel Paclitaxel PARP inhibitor - Chk1 inhibitor DNA-PK lost cells rely on PARP-mediated backup-end joining repair of doxorubicin-induced double-strand breaks. Normal cells have DNA-PK and are not sensitised by PARP inhibitors Mitosis inhibitor causing uncapping at telomers and DNA damage signalling-mediated cell death. Docetaxel triggers Chk1-mediated mitotic checkpoint required for survival in p53 mutated cells

25 PARP inhibitor mechanism of action

26 Ström CE and Helleday T. Biomolecules 2012;2: PARP is involved in SSBR, replication repair, alt-nhej, fork protection, NER and BER

27 PARP1 trapping is required for PARP inhibitor toxicity Reprinted from Murai J et al. Cancer Res 2012;72(21): , with permission from AACR

28 PARP1 + BRCA2 protects replication forks from Mre11 degradation Reprinted from Ying S et al. Cancer Res 2012;72(11): , with permission from AACR

29 PARP1 + BRCA2 protects replication forks from Mre11 degradation PARP inhibitors HR BER RR Prot Trap alt NHEJ PARP inhibitors inhibits several PARP family member Reprinted from Ying S et al. Cancer Res 2012;72(11): , with permission from AACR

30 SUMMARY Efficacy of PARP inhibitors in monotherapy coupled with HR defect Combination strategy complex and in depth mechanistic understanding needed PARP inhibitors trap PARP on DNA and has different effect from protein loss PARP1 is involved in SSB repair, replication restart, fork protection, B-NHEJ Resistance can develop to PARP inhibitors

31 Thank you!