Addition Of Poly ADP-ribose Polymerase Inhibitors Research Articles

PARP inhibitors as therapy for small cell lung carcinoma: A systematic review and meta-analysis of clinical trials.

Small Cell Lung Cancer (SCLC) is a neuroendocrine carcinoma characterized by aggressive behavior and poor prognosis with limited treatment options. Poly ADP-Ribose Polymerase inhibitors (PARPi) are novel anti-cancer agents that induce DNA damages and cause cell death in tumor cells with impaired DNA repair, known as the synthetic lethality concept. This study aimed to analyze the efficacy and safety of PARPi for patients with SCLC from available clinical trial data. Studies reporting efficacy and safety of PARPi therapy for SCLC patients were searched across five databases with predetermined eligibility criteria in accordance with the PRISMA statement. Critical appraisal was done using suitable tools, outcomes were extracted, and analyzed. Five randomized controlled clinical trials with 451 interventional patients and 308 control patients with SCLC were included. The analysis showed increased Progression-Free Survival (PFS) (RR 0.92 (95 %CI 0.84-1.00; p=0.05)) and Objective Response Rate (ORR) (RR 1.27 (95 %CI 1.07-1.50; p=0.007)), no significant difference in Overall Survival (OS) (RR 1.03 (95 %CI 0.92-1.15; p=0.60)), and an increased risk for serious Treatment Emergent Adverse Events (TEAEs) (RR 1.13 (95 %CI 0.95-1.35; p=0.16)) in PARPi-receiving SCLC patients. Amongst the hematologic toxicities, sub-analysis showed that thrombocytopenia had the highest risk, followed by neutropenia, anemia, leukopenia, and lymphopenia. The addition of PARPi in the chemotherapy regimen for patients with SCLC results in increased PFS and ORR, with no difference in OS and an increased risk of TEAEs. Further and larger clinical studies are needed to validate the efficacy and safety of PARPi therapy for SCLC patients.

Abstract 7135: Preclinical effects of Tumor Treating Fields (TTFields) with PARP inhibitors in ovarian cancer

Abstract Purpose: Among gynecological malignancies, ovarian cancer is the leading cause of mortality. Poly (ADP-ribose) polymerase inhibitors (PARPi) represent standard-of-care treatment for selected cases of advanced epithelial ovarian cancer. PARPi exhibit sensitivity in homologues recombination deficient (HRD) tumors, in which there are mutations in the Fanconi Anemia (FA)-BRCA pathway, while about 75% of ovarian cancer patients are homologues recombination proficient (HRP). TTFields are non-invasive electric fields that disrupt cellular processes critical for cancer cell viability and tumor progression. Recent research showed that TTFields induce an HRD-like state (also known as BRCAness state) in various cancer types. The current study aims to investigate the impact of TTFields applied together with PARPi in ovarian cancer preclinical models. Methods: In vitro, A2780 (HRP), OVCAR3 (HRD), and A2780cis (platinum-resistant) ovarian cancer cells were treated with TTFields (1 V/cm RMS, 200 kHz, 72 h), alone or with addition of PARPi (olaparib or niraparib, at various concentrations). Efficacy was measured by analyzing cell count, colony formation, and apoptosis induction. The overall effect was calculated by multiplying cell count with colony formation. TTFields-treated cells were evaluated for the expression of FA-BRCA pathway proteins and for formation of γH2AX, a DNA damage marker, using Western blot and fluorescent microscopy, respectively. In vivo, ID8-fLuc (HRP) cells were inoculated intraperitoneally to 6-8-week-old C57BL/6 mice. Seven days post inoculation, mice were treated with sham-vehicle, TTFields, olaparib (50 mg/kg), or both over a period of four weeks. Tumor growth was analyzed using bioluminescent imaging at treatment cessation, and survival analysis was performed. Results: TTFields application resulted in reduced cell count, increased overall effect, and increased apoptosis in vitro. When TTFields were applied together with PARPi, a high and moderate synergistic interaction was shown respectively the BRCA wild-type A2780 cells and the platinum-resistant A2780cis cells. However, in the BRCA mutant OVCAR-3 cells the effect was additive. A downregulation of FA-BRCA protein expression was confirmed after TTFields treatment of the ovarian cells, with consequent DNA damage. In the tumor-bearing mice, TTFields and olaparib co-treatment resulted in reduced tumor volume and a survival benefit relative to the monotherapies and to control-treated mice. Conclusions: The data suggest potential advantages for TTFields concomitant with PARPi in ovarian cancer, even without underlying BRCA mutations - consistent with the BRCAness state induced by TTFields - and also suggests benefits in platinum-resistant ovarian cancer. Citation Format: Yani Berckmans, Hila Ene, Kerem Ben-Meir, Antonia Martinez-Conde, Roni Monin, Bieke Van den Ende, Sara Van Mechelen, Roni Frechtel-Gerzi, Hila Gabay, Rotem Engelman, Eyal Dor-On, Adi Haber, Moshe Giladi, Uri Weinberg, Yoram Palti, Ignace Vergote, An Coosemans. Preclinical effects of Tumor Treating Fields (TTFields) with PARP inhibitors in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7135.

Neoadjuvant PARP inhibitors in patients with early HER2-negative breast cancer harboring BRCA 1/2 germline mutations: A systematic review and meta-analysis.

e12611 Background: Poly (ADP-ribose) polymerase inhibitors (PARPi) are approved for the treatment of germline BRCA mutated (gBRCAm) breast cancer (BC) patients in the adjuvant and metastatic settings. Several studies have explored the role of PARPi in the neoadjuvant setting both with and without chemotherapy. Here, we explore the efficacy and safety of neoadjuvant PARPi in early HER2-negative BC patients. Methods: We searched PubMed, Scopus, and the Cochrane Library databases for randomized (RCT) and non-randomized clinical trials (non-RCT) that reported the proportion of patients with pathological complete response (pCR) after neoadjuvant PARPi and safety. Statistical analysis was performed using R software. Data were pooled using the random effects model. Results: Analysis included 3 RCTs and 4 non-RCTs, with 942 HER-2 negative breast cancer patients, 293 harboring a gBRCA 1/2 mutation. In a pooled analysis, gBRCAm carriers achieved a significantly higher rate of pCR than BRCA wild-type patients (56% versus 37%, p=0.04) with neoadjuvant PARPi. There was no difference in pCR when PARPi were combined with carboplatin (+/- chemotherapy) (40% versus 44%, p=0.69). Among RCTs (n=457) patients received PARPi in combination with either Paclitaxel plus Carboplatin (PCb) (85%) or with Paclitaxel alone (P) (15%). PARPi were associated with a higher pCR which approached, but did not meet statistical significance (51% vs 41%; Odds Ratio [OR]: 1.30, 95%CI 0.97 to 1.74, p=0.08). gBRCAm was associated with higher pCR compared to wild type in RCTs analysis (60% versus 48%; OR: 1.64, 95%CI 1.01 to 2.68, p=0.05). The most common adverse events (AEs) were cytopenias, nausea, fatigue, alopecia, and dizziness. Hematological toxicities were the most frequent serious AEs, including anemia (15%), neutropenia (22%), and thrombocytopenia (3%). The combination of PARPi and carboplatin was associated with higher hematological AEs (78% versus 46%; P=0.002). Conclusions: The addition of PARPi in the neoadjuvant setting improves pCR in early-stage HER2-negative breast cancer and germline BRCA 1/2 mutations, but not for unselected patients. Combination of PARPi with carboplatin does not improve pCR and leads to substantially worse toxicity. Further studies are warranted to identify the best neoadjuvant PARPi schema.[Table: see text]

Overcoming Resistance of Glioblastoma to Conventional Cytotoxic Therapies by the Addition of PARP Inhibitors

This article will present the rationale for combining chemical inhibitors of the DNA repair enzyme poly(ADP-ribose) polymerase (PARP) with conventional cytotoxic agents to improve the treatment of glioblastoma. After a brief review of the current therapeutic options for these aggressive tumours, the possible reasons for their resistance to radiation and chemotherapy will be discussed, highlighting the important role of DNA damage response pathways in many key resistance mechanisms. The dose-limiting toxicities associated with radiation and chemotherapy treatment will be described in order to illustrate the importance of tumour specificity in any attempt to increase the effectiveness of conventional treatments. There will then be a summary of the reasons why targeting DNA repair pathways might achieve tumour specific sensitization. After a brief summary of the key DNA damage response pathways, the biology, biochemistry and pharmacology of PARP and the existing PARP inhibitors will be presented. The major part of the review will cover the effects of combining PARP inhibitors with radiation and chemotherapy in vitro and in vivo, commenting on the underlying mechanisms and indicating where the data are predictive of tumour specific sensitization. Finally, we will consider specific scenarios where PARP inhibitors might contribute to the treatment of glioblastoma patients, discuss the challenges and opportunities associated with early phase clinical testing of these agents, and describe the clinical trials that are either underway or in development.

Protection by Ascorbate against Apoptosis of Thymocytes: Implications of Ascorbate-Induced Nonlethal Oxidative Stress and Poly(ADP-ribosyl)ation

Apoptosis can be triggered in thymocytes with stimuli (6α-methylprednisolone, thapsigargin, and etoposide) acting by different mechanisms. In each of these instances cell death is extensively prevented until 5 h of incubation when cells are preincubated with 250 μMascorbic acid (AA) for 1 h, then washed, and incubated in fresh medium containing the above mentioned apoptotic stimuli. In addition, the degree of spontaneous apoptosis of untreated thymocytes is somewhat lower in the AA-preincubated cells. The protection against apoptosis does not seem to be dependent on the intracellular enrichment of AA, as measured at the end of the preincubation period. On the contrary, such a protection is strictly related to a partial loss of ascorbate in the medium (possibly due to its autooxidation), is catalase-inhibitable, and is reproduced by a preincubation of the cells with nontoxic concentrations of hydrogen peroxide. The AA-supplemented cells show a remarkable decrease in NAD+levels and a significant increase of poly(ADP-ribose) polymerase (PARP) activity. Consistently with these results, the addition of PARP inhibitors, such as thymidine and 3-aminobenzamide, during the preincubation with AA, prevents NAD+depletion and abolishes the protective effect of AA against apoptosis. The possibility is discussed that an early activation of PARP by stimuli which are nontoxic per se makes the cells able to withstand subsequent apoptotic stimuli which are otherwise lethal.