Advances in PARP Inhibitors for Prostate Cancer

New Horizons of Synthetic Lethality in Cancer: Current Development and Future Perspectives

In recent years, synthetic lethality has been recognized as a solid paradigm for anticancer therapies. The discovery of a growing number of synthetic lethal targets has led to a significant expansion in the use of synthetic lethality, far beyond poly(ADP-ribose) polymerase inhibitors used to treat BRCA1/2-defective tumors. In particular, molecular targets within DNA damage response have provided a source of inhibitors that have rapidly reached clinical trials. This Perspective focuses on the most recent progress in synthetic lethal targets and their inhibitors, within and beyond the DNA damage response, describing their design and associated therapeutic strategies. We will conclude by discussing the current challenges and new opportunities for this promising field of research, to stimulate discussion in the medicinal chemistry community, allowing the investigation of synthetic lethality to reach its full potential.

Applications of Modified Mesenchymal Stem Cells as Targeted Systems against Tumor Cells

Combined gene and cell therapy are promising strategies for cancer treatment. Given the complexity of cancer, several approaches are actively studied to fight this disease. Using mesenchymal stem cells (MSCs) has demonstrated dual antitumor and protumor effects as they exert massive immune/regulatory effects on the tissue microenvironment. MSCs have been widely investigated to exploit their antitumor target delivery system. They can be genetically modified to overexpress genes and selectively or more efficiently eliminate tumor cells. Current approaches tend to produce more effective and safer therapies using MSCs or derivatives; however, the effect achieved by engineered MSCs in solid tumors is still limited and depends on several factors such as the cell source, transgene, and tumor target. This review describes the progress of gene and cell therapy focused on MSCs as a cornerstone against solid tumors, addressing the different MSC-engineering methods that have been approached over decades of research. Furthermore, we summarize the main objectives of engineered MSCs against the most common cancers and discuss the challenges, limitations, risks, and advantages of targeted treatments combined with conventional ones.

Prostatic adenocarcinoma: molecular underpinnings and treatment-related options

Prostate cancer is heterogeneous with varied pathologic features and presents with a wide spectrum of clinical manifestations from indolent to advanced cancer. Interrogation of the molecular landscape of prostate cancer has unveiled the complex genomic alterations in these tumors, which significantly impacts tumor biology. The documented array of chromosomal alterations, gene fusions, and epigenetic changes not only play a crucial role in oncogenesis and disease progression, but also impacts response and resistance to various therapeutic modalities. Various gene expression assays have been developed and are currently recommended in aiding clinical decision making in these clinically and molecularly heterogeneous cancer. In this review, we provide an overview of the molecular underpinnings of prostate cancer, and briefly review the current status of molecular testing and therapeutic options in the management of these tumors.

[177Lu]Lu-PSMA-617 as first-line systemic therapy in patients with metastatic castration-resistant prostate cancer: a real-world study

PURPOSE

The use of [177Lu]Lu-PSMA-617 radioligand therapy has become increasingly recognized as a viable therapeutic approach for patients in the advanced stages of metastatic castration-resistant prostate cancer (mCRPC). However, there is limited data regarding its effectiveness and safety in earlier lines. This study aims to present our institution's experience with [177Lu]Lu-PSMA-617 as a first-line systemic therapy for mCRPC.

METHODS

We collected and analyzed data from consecutive mCRPC patients who underwent first-line treatment with [177Lu]Lu-PSMA-617 at our center from 2015 to 2023. The various outcome measures included best prostate-specific antigen-response rate (PSA-RR) (proportion of patients achieving a ≥ 50% decline in PSA); objective radiographic response rate (ORR) (proportion of patients achieving complete or partial radiographic responses); radiographic progression-free survival (rPFS) (measured from treatment initiation until radiographic progression or death from any cause); overall survival (OS) (measured from treatment initiation until death from any cause); and adverse events.

RESULTS

Forty treatment-naïve mCRPC patients with PSMA-positive disease on [68Ga]Ga-PSMA-11 PET/CT were included (median age: 68.5 years, range: 45-78; median PSA: 41 ng/mL, range: 1-3028). These patients received a median cumulative activity of 22.2 GBq (range: 5.55-44.4) [177Lu]Lu-PSMA-617 over 1-6 cycles at 8-12 week intervals. A ≥ 50% decline in PSA was observed in 25/40 (62.5%) patients (best PSA-RR). Radiographic responses were evaluated for thirty-eight patients, with thirteen showing partial responses (ORR 34.2%). Over a median follow-up of 36 months, the median rPFS was 12 months (95% confidence interval, CI: 9-15), and the median OS was 17 months (95% CI: 12-22). Treatment-emergent grade ≥ 3 anemia, leucopenia, and thrombocytopenia were noted in 4/40 (10%), 1/40 (2.5%), and 3/40 (7.5%) patients, respectively.

CONCLUSION

The findings suggest that [177Lu]Lu-PSMA-617 is a safe and effective option as a first-line treatment in mCRPC. Further trials are needed to definitively establish its role as an upfront treatment modality in this setting.

Artificial INtelligence to Support Informed DEcision-making (INSIDE) for Improved Literature Analysis in Oncology

BACKGROUND

Defining optimal therapeutic sequencing strategies in prostate cancer (PC) is challenging and may be assisted by artificial intelligence (AI)-based tools for an analysis of the medical literature.

OBJECTIVE

To demonstrate that INSIDE PC can help clinicians query the literature on therapeutic sequencing in PC and to develop previously unestablished practices for evaluating the outputs of AI-based support platforms.

DESIGN, SETTING, AND PARTICIPANTS

INSIDE PC was developed by customizing PubMed Bidirectional Encoder Representations from Transformers. Publications were ranked and aggregated for relevance using data visualization and analytics. Publications returned by INSIDE PC and PubMed were given normalized discounted cumulative gain (nDCG) scores by PC experts reflecting ranking and relevance.

INTERVENTION

INSIDE PC for AI-based semantic literature analysis.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

INSIDE PC was evaluated for relevance and accuracy for three test questions on the efficacy of therapeutic sequencing of systemic therapies in PC.

RESULTS AND LIMITATIONS

In this initial evaluation, INSIDE PC outperformed PubMed for question 1 (novel hormonal therapy [NHT] followed by NHT) for the top five, ten, and 20 publications (nDCG score, +43, +33, and +30 percentage points [pps], respectively). For question 2 (NHT followed by poly [adenosine diphosphate ribose] polymerase inhibitors [PARPi]), INSIDE PC and PubMed performed similarly. For question 3 (NHT or PARPi followed by 177Lu-prostate-specific membrane antigen-617), INSIDE PC outperformed PubMed for the top five, ten, and 20 publications (+16, +4, and +5 pps, respectively).

CONCLUSIONS

We applied INSIDE PC to develop standards for evaluating the performance of AI-based tools for literature extraction. INSIDE PC performed competitively with PubMed and can assist clinicians with therapeutic sequencing in PC.

PATIENT SUMMARY

The medical literature is often very difficult for doctors and patients to search. In this report, we describe INSIDE PC-an artificial intelligence (AI) system created to help search articles published in medical journals and determine the best order of treatments for advanced prostate cancer in a much better time frame. We found that INSIDE PC works as well as another search tool, PubMed, a widely used resource for searching and retrieving articles published in medical journals. Our work with INSIDE PC shows new ways in which AI can be used to search published articles in medical journals and how these systems might be evaluated to support shared decision-making.

IGFBP3 promotes resistance to Olaparib via modulating EGFR signaling in advanced prostate cancer

Olaparib is a pioneering PARP inhibitor (PARPi) approved for treating castration-resistant prostate cancer (CRPC) tumors harboring DNA repair defects, but clinical resistance has been documented. To study acquired resistance, we developed Olaparib-resistant (OlapR) cell lines through chronic Olaparib treatment of LNCaP and C4-2B cell lines. Here, we found that IGFBP3 is highly expressed in acquired (OlapR) and intrinsic (Rv1) models of Olaparib resistance. We show that IGFBP3 expression promotes Olaparib resistance by enhancing DNA repair capacity through activation of EGFR and DNA-PKcs. IGFBP3 depletion enhances efficacy of Olaparib by promoting DNA damage accumulation and subsequently, cell death in resistant models. Mechanistically, we show that silencing IGFBP3 or EGFR expression reduces cell viability and resensitizes OlapR cells to Olaparib treatment. Inhibition of EGFR by Gefitinib suppressed growth of OlapR cells and improved Olaparib sensitivity, thereby phenocopying IGFBP3 inhibition. Collectively, our results highlight IGFBP3 and EGFR as critical mediators of Olaparib resistance.

PARP Inhibitors in Metastatic Castration-Resistant Prostate Cancer: Unraveling the Therapeutic Landscape

The treatment landscape of metastatic prostate cancer (mPCa) is rapidly evolving with the recent approvals of poly-ADP ribose polymerase inhibitors (PARPis) as monotherapy or as part of combination therapy with androgen receptor pathway inhibitors in patients with metastatic castration-resistant prostate cancer (mCRPC). Already part of the therapeutic armamentarium in different types of advanced cancers, these molecules have shaped a new era in mPCa by targeting genomic pathways altered in these patients, leading to promising responses. These agents act by inhibiting poly-ADP ribose polymerase (PARP) enzymes involved in repairing single-strand breaks in the DNA. Based on the PROfound and TRITON3 trials, olaparib and rucaparib were respectively approved as monotherapy in pretreated patients with mCRPC and alterations in prespecified genes. The combinations of olaparib with abiraterone (PROpel) and niraparib with abiraterone (MAGNITUDE) were approved as first-line options in patients with mCRPC and alterations in BRCA1/2, whereas the combination of talazoparib with enzalutamide (TALAPRO-2) was approved in the same setting in patients with alterations in any of the HRR genes, which are found in around a quarter of patients with advanced prostate cancer. Additional trials are already underway to assess these agents in an earlier hormone-sensitive setting. Future directions will include refining the treatment sequencing in patients with mCRPC in the clinic while taking into account the financial toxicity as well as the potential side effects encountered with these therapies and elucidating their mechanism of action in patients with non-altered HRR genes. Herein, we review the biological rationale behind using PARPis in mCRPC and the key aforementioned clinical trials that paved the way for these approvals.

Novel PARP7 Inhibitors for Treating Cancer

Provided herein are novel PARP7 inhibitors, pharmaceutical compositions, use of such compounds in treating cancer, and processes for preparing such compounds.

Hematological Toxicities with PARP Inhibitors in Prostate Cancer: A Systematic Review and Meta-Analysis of Phase II/III Randomized Controlled Trials

BACKGROUND

Poly ADP-ribose polymerase inhibitors (PARPis) are an important class of therapeutics for metastatic castration-resistant prostate cancer (mCRPC). Unlike hormone-based treatments for mCRPC, PARPis are not without drug-related hematological adverse events.

OBJECTIVE

To review the evidence on hematological toxicities, including anemia, thrombocytopenia, and neutropenia from PARPis in prostate cancer.

STUDY METHODOLOGY

A systematic review and meta-analysis using the PRISMA guidelines was performed for phase II and III randomized controlled trials (RCTs) of PARPis in prostate cancer. PubMed, Embase, and Ovid All EBM reviews-Cochrane were queried from inception to 9 June 2023. The Mantel-Haenszel method was used to report risk ratios (RR) and 95% confidence intervals (CI) for all-grade and high-grade anemia, thrombocytopenia, and neutropenia toxicities.

RESULTS

The systematic review retrieved eight phase II and III RCTs; specifically, eight were included in the anemia, five in the all-grade thrombocytopenia and neutropenia, and four in the high-grade thrombocytopenia and neutropenia outcomes. Compared to a placebo and/or other non-PARPi treatments, PARPi use was associated with an increased risk of all-grade anemia (RR, 3.37; 95% CI, 2.37-4.79; p < 0.00001), thrombocytopenia (RR, 4.54; 95% CI, 1.97-10.44; p = 0.0004), and neutropenia (RR, 3.11; 95% CI, 1.60-6.03; p = 0.0008). High-grade anemia (RR, 6.94; 95% CI, 4.06-11.86; p < 0.00001) and thrombocytopenia (RR, 5.52; 95% CI, 2.80-10.88; p < 0.00001) were also associated with an increased risk, while high-grade neutropenia (RR, 3.63; 95% CI, 0.77-17.23; p = 0.10) showed no significant association. Subgroup stratification analyses showed differences in various all-grade and high-grade toxicities.

CONCLUSION

PARPis were associated with an increased risk of hematological AEs. Future studies with more pooled RCTs will enhance this understanding and continue to inform patient-physician shared decision-making. Future studies may also have a role in improving the current management strategies for these AEs.

Design, synthesis, and biological evaluation of a series of benzofuran[3,2-d]pyrimidine-4(3H)-one derivatives containing thiosemicarbazone analogs as novel PARP-1 inhibitors

Poly ADP ribose polymerase-1 (PARP-1), one of the most important members of the PARP protein family, plays a crucial role in DNA damage repair, gene transcription, and apoptosis of cancer cells. In this work, benzofuran[3,2-d]pyrimidine-4(3H)-one was used as a framework to design and synthesize a series of novel PARP-1 inhibitors by introducing thiosemicarbazone or its derivatives into the scafford. Among all the target compounds, 19b and 19c were found to exhibit more potent inhibitory activity and higher selectivity against PARP-1 than Olaparib, especially the latter had an IC50 value of 0.026 μM against PARP-1 enzyme and a PARP-2/PARP-1 selectivity of 85.19-fold over Olapanib. Apart from strong cytotoxicity against the tested cancer cell lines, 19c was most sensitive to SK-OV-3 cells, with an IC50 value of 4.98 μM superior to Olaparib. Anti-cancer mechanism studies revealed that 19c could inhibit DNA single-strand breakage repair and aggravate DNA double-strand breakage by inhibiting PARP-1 activity, and promote the apoptosis of cancer cells through the mitochondrial apoptosis pathway.