Indicare quale tra queste affermazioni riguardante gli inibitori di PARP SBAGLIATA:

3. PARP INHIBITORS FOR CANCER THERAPYGrazia GrazianiUniversity of Rome �Tor Vergata�

7. BIOLOGICAL EFFECTS DERIVING FROM PARP ACTIVATION Covalent poly(ADP-ribosyl)ation influences the function of target proteins Interaction of ADP-ribose polymers bound to activated PARP with polymer-binding consensus motif of partner proteins PAR oligomers, when cleaved from poly(ADPribosyl)ated proteins, confer distinct cellular effects Lowering of the cellular level of its substrate, NAD+

9. PARP-2 is 18 times less active than PARP-1PARP-2 is 18 times less active than PARP-1

12.  PARP INHIBITORS AS CHEMO- AND RADIOSENSITIZERS Methylating agents: TEMOZOLOMIDE Topoisomerase I inhibitors Ionizing radiation

14. TEMOZOLOMIDE and DNA METHYLATION

15. THE CYTOTOXICITY OF TEMOZOLOMIDE IS DUE TO O6-METHYLGUANINE Cytotoxicity requires: Low levels of O6-methylguanine DNA methyltrasferase (MGMT) A functional Mismatch Repair (MMR)

19. PARP inhibitors might interfere with tumor growth at different levels Modulating the transcriptional activation of different tumor related transcription factors tumorigenesis and angiogenesisPARP inhibitors might interfere with tumor growth at different levels Modulating the transcriptional activation of different tumor related transcription factors tumorigenesis and angiogenesis

20. PARP INHIBITORS AS MONOTHERAPY Anti-tumor activity in tumor cells with defective repair of DNA double strand breaks by Homologous Recombination due to BRCA mutations: THE CONCEPT OF �SYNTHETIC LETHALITY� Bryant et al. Nature 2005, 434:913.; Farmer et al., Nature 2005, 434:917

21. Synthetic lethality Two genes are synthetically lethal if loss of function of either gene alone is compatible with cell survival, but inactivation of both cause cell death. A cancer-related mutated gene can sensitise tumour cells to a drug that specifically inhibits its �synthetic lethal partner�. The same drug should not affect normal cells, thus allowing higher therapeutic selectivity

22. BRCA The mutation increases the risk of ovarian cancer up to 60% (BRCA1 60%, BRCA2 10-20%) and breast cancer up to 84% (BRCA1 84%, BRCA2 60-80%). BRCA2, however, contributes less to the risk of ovarian cancer, but more to the risk of male breast cancer and pancreatic cancer. Only 5% of breast cancers and 10% of ovarian cancers are associated with a known genetic mutation. Loss of the second allele will lead to a cell not capable of the repair of DNA double strand breaks.

23. Homologous Recombination relies on the presence of an intact sister chromatid to act as template for correct repair of the break without loss of sequence information DSB is recognized by the MRN complex (Mre11�Rad50�Nbs1), that keeps the DNA ends in close proximity to each other and is required for end resection to generate the long 3�-ssDNA overhangs required for HR. BRCA1, BRCA2 and BARD1 allow recruitment of the Rad51 protein which coats the ssDNA segment displacing RPA and forming a RAD51 nucleoprotein filament. RAD51 nucleoprotein filament catalyzes strand invasion and initiates the homology search on the intact sister chromatid. The eukaryotic genome is under constant stress, one result of which is the constant generation of DNA damage. DNA damage can result from both endogenous (e.g. reactive oxygen species and cytosine deamination) and exogenous (e.g. ultraviolet radiation, ionizing radiation and chemicals) sources. HR is responsible for the repair of DNA double-strand breaks and DNA interstrand cross-links and for accurate chromosome segration. The process of HR is initiated at the site of DNA breaks and gaps and involves a search for homologous sequences promoted by Rad51 and auxiliary proteins followed by the subsequent invasion of broken DNA ends into the homologous duplex DNA that then serves as a template for repair. The eukaryotic genome is under constant stress, one result of which is the constant generation of DNA damage. DNA damage can result from both endogenous (e.g. reactive oxygen species and cytosine deamination) and exogenous (e.g. ultraviolet radiation, ionizing radiation and chemicals) sources. HR is responsible for the repair of DNA double-strand breaks and DNA interstrand cross-links and for accurate chromosome segration. The process of HR is initiated at the site of DNA breaks and gaps and involves a search for homologous sequences promoted by Rad51 and auxiliary proteins followed by the subsequent invasion of broken DNA ends into the homologous duplex DNA that then serves as a template for repair.

24. WHY DO PARP INHIBITORS SPARE NORMAL CELLS?

25. WHY DO PARP INHIBITORS SELECTIVELY KILL TUMOR CELLS WITH MUTATEDBRCA AND DEFECT IN THE REPAIR OF DNA DOUBLE STRAND BREAKS?

26. Lack of PARP-mediated BER is a synthetic lethal partner of complete BRCA1 or BRCA2 functional loss

27. SPORADIC TUMOURS WITH BRCA-LIKE CLINICAL PROPERTIES:TRIPLE NEGATIVE BREAST CANCERS 15% of breast cancers The overlap of BRCA1-associated breast cancers with the TNBC phenotype is significant. There is a clinical and pathological likeness between TRIPLE NEGATIVE, BASAL-LIKE breast cancers and hereditary BRCA1 breast cancers

28. BASAL-LIKE AND TRIPLE NEGATIVE BREAST CANCER 75% triple negative breast cancers are also basal-like 80-90% of hereditary BRCA1 breast carcinoma have features similar to basal-like tumors HER2 OVEREXPRESSING and BASAL-LIKE have the worst prognosis Basal-like tumors are mitotically active, high-grade, invasive, and associated with younger age The basal-like phenotype is ER, PR and HER2-negative, and either EGFR or CK 5/6 positive

29. Possible mechanisms of developing BRCAness in sporadic cancers Increased expression of proteins that inactivate BRCA1 (ID4) BRCA1 promoter methylation (10-15% sporadic breast cancers and 5-30% sporadic ovarian cancers) FANCF promoter methylation Defects in other Fanconi�s anemia complex proteins Decreased expression of other proteins involved in HR, including Rad51, ATM PTEN deficiency

31. PARP INHIBITORS newer PARP inhibitors are much more potent and specific for the reason that most of the compounds in this category are composed of carboxamide attached to an aromatic ring or the carbamoyl group built in a polyaromatic heterocyclic skeleton to form a fused aromatic lactam or imide which enhances the potency and specificity newer PARP inhibitors are much more potent and specific for the reason that most of the compounds in this category are composed of carboxamide attached to an aromatic ring or the carbamoyl group built in a polyaromatic heterocyclic skeleton to form a fused aromatic lactam or imide which enhances the potency and specificity

34. OLAPARIB: Phase II in BRCA1 OR BRCA2 MUTATED ADVANCED BREAST CANCER (ICEBERG 1)

36. OLAPARIB: Phase II in BRCA1 OR BRCA2 MUTATIONS ADVANCED OVARIAN CANCER (ICEBERG 2) 90% sporadic and 10% have a predisposing genetic defect 90% of patients with familial predisposition carry the BRCA defect. Although women with BRCA-associated ovarian cancer might have higher response rates to chemotherapy and improved survival rates than do those with sporadic ovarian cancer, most with stages III and IV will ultimately relapse and die despite available therapies. Up until now, knowledge of a BRCA mutation has not affected the selection of treatment for ovarian cancer. Phase II: in 57 patients with 2 doses with a median of 3 previous chemotherapy regimens

37. OLAPARIB: Phase II in BRCA1 or BRCA2 MUTATIONS ADVANCED OVARIAN CANCER PLATINUM RESISTANT (ICEBERG 3) The PFS were 6.5 vs 8.8 vs 7.1 months for 200 mg, 400 mg, and liposomal doxorubicin arm, respectively. Olaparib did not reach the primary objective of improving PFS partly because of a better PFS seen in the liposomal doxorubicin arm than expected. Twice as many grade 3 toxicities were seen in the liposomal doxorubicin arm. Although reported as a negative study, this trial still shows consistent response and decreased toxicity with the use of single-agent olaparib in BRCA mutation ovarian cancer patients.

39. INIPARIB: A NON-COMPETITIVE PARP INHIBITOR Iniparib is an irreversible inhibitor It ejects the Zn from the first zinc finger of PARP-1 inactivating the enzyme and degrades PARP-1 activating a protease The first PARP inhibitor that has shown survival advantage in TNBC phase II

40. About 15% of breast cancer; good response in the neo-adjuvant setting to taxanes and antracyclines. When metastatic disease develops the median survival is of approximately 1 year. No standard-of-care therapy exists for patients with metastatic triple-negative breast cancer. Current phase III comparing carboplatin versus docetaxel It shares clinical and pathological features with hereditary BRCA1-related breast cancers In sporadic triple-negative there is a dysregulation of BRCA1 or other components of HR Gemcitabine + carboplatin give 26-34% response rates Phase II: INIPARIB PLUS CHEMOTHERAPY IN METASTATIC TRIPLE NEGATIVE BREAST CANCER

41. INIPARIB AND PHASE III IN TNBC Sanofi-Aventis and its subsidiary, BiPar Sciences, at the end of January 2011 announced that a randomized Phase III trial evaluating Iniparib in 519 patients with metastatic disease did not meet the pre-specified criteria for significance for co-primary endpoints of overall survival and progression-free survival. The overall safety analysis indicates that the addition of iniparib did not significantly add to the toxicity profile of gemcitabine and carboplatin.

44. VELIPARIB AND PHASE 0 TRIALS The first Phase 0 study under FDA new Exploratory Investigational New Drug was performed (a first-in-human clinical trial conducted under an exploratory IND that has no therapeutic or diagnostic intent and involves very limited human exposure). Veliparib was chosen because it has a wide therapeutic index and a validated PD assay. The primary study end-point was target modulation by the PARP inhibitor measuring POLY(ADP-RIBOSE) levels in perypheral blood mononuclear cells (PBMC) and tumour biopsies.

45. RESISTANCE TO PARP INHIBITORS Secondary mutations of BRCA genes altering the reading frame to wild-type

46. SENSITIVITY OF OVARIAN CANCER TO PLATINUM AGENTS AND USE OF PARP INHIBITORS Platinum resistance: disease progression within 6 months of prior platinum therapy Platinum refractory disease: disease progression on platinum therapy Fong PC et al., Journal of Clnical Oncology 28, 2512, 2010: Olaparib induced objective response 46.2% in platinum sensitive patients (6/13), 33.5% in platinum-resistant patients (8/24), 0% in platinum-refractory patients(0/13)

47. RESISTANCE TO PARP INHIBITORS Up-regulation of p-glycoprotein (Pgp) efflux pump

48. CHALLENGING TASKS (1) To determine the optimal chemotherapy backbone to combine with PARP inhibitors (2) To balance the benefit and toxicity risk when PARP inhibitors are used in combination therapies (3) To define the most effective schedule of administration (i.e., continuous versus intermittent dosing with chemotherapy: higher myelotoxicity; concomitant or sequence treatment)

49. CHALLENGING TASKS (4) To define more precisely the patient population most likely to respond: potential signature of BRCAness (e.g. 60-gene assay to identify BRCAness profile) (5) Potential prophylactic use for BRCA1 and BRCA2 mutation carriers: potential long-term toxicity (6) PARP-1 expression/activity levels???? (HR-deficient cancers have higher PARP-1 levels) (7) To discover and validate candidate biomarkers to predict responders [i.e., ?H2AX, RAD51 (as a marker of intact HR), germline DNA studies,etc.]

50. gH2AX and RAD51 and HR function A key component in DNA repair is the histone protein H2AX, which becomes rapidly phosphorylated to form large numbers of ?H2AX at nascent DSB, creating a focus where proteins involved in DNA repair and chromatin remodeling accumulate (pink spots). Rad51 is a crucial downstream protein involved in HR repair, which is relocalized within the nucleus in response to DNA damage to form distinct foci that are thought to represent assemblies of proteins at these sites of HR repair (green spots).

51. CHALLENGING TASKS:HOW TO OVERCOME RESISTANCE TO PARP INHIBITORS 6-THYOGUANINE: it is not substrate of Pgp and reactivation of HR is not sufficient to repair lesions induced by 6-Thyoguanine Inhibitors of Pgp Proteasome inhibitors: down-regulation of Pgp

52. WHAT IS GOINGO TO BE THE FUTURE OF PARP INHIBITORS? Trials directed at subsets of patients who are most likely to respond to PARP inhibitors Trials in combination with chemotherapeutic agents for which preclinical studies have indeed shown synergy with PARP inhibitors