Beyond monotherapy: An era ushering in combinations of PARP inhibitors with immune checkpoint inhibitors for solid tumors

The introduction of PARP inhibitors (PARPis) and immune checkpoint inhibitors (ICIs) has marked a significant shift in the treatment landscape for solid tumors. Emerging preclinical evidence and initial clinical trials have indicated that the synergistic application of PARPis and ICIs may enhance treatment efficacy and potentially improve long-term patient outcomes. Nonetheless, how to identify specific tumor types and molecular subgroups most likely to benefit from this combination remains an area of ongoing research. This review thoroughly examines current studies on the co-administration of PARPis and ICIs across various solid tumors. It explores the underlying mechanisms of action, evaluates clinical efficacy, identifies potential responder populations, and delineates common adverse events alongside strategic management approaches. The aim is to offer a detailed understanding of this combination therapy, potentially guiding future therapeutic strategies for solid tumors.

Updated progression-free survival and final overall survival with maintenance olaparib plus bevacizumab according to clinical risk in patients with newly diagnosed advanced ovarian cancer in the phase III PAOLA-1/ENGOT-ov25 trial

OBJECTIVE

In the PAOLA-1/ENGOT-ov25 trial (NCT02477644), adding maintenance olaparib to bevacizumab provided a substantial progression-free survival benefit in patients with newly diagnosed advanced ovarian cancer and homologous recombination deficiency (HRD)-positive tumors, irrespective of clinical risk. Subsequently, a clinically meaningful improvement in overall survival was reported with olaparib plus bevacizumab in the HRD-positive subgroup. We report updated progression-free survival and overall survival by clinical risk and HRD status.

METHODS

Patients in clinical response after first-line platinum-based chemotherapy plus bevacizumab received maintenance olaparib (up to 24 months) plus bevacizumab (up to 15 months in total) or placebo plus bevacizumab. This post hoc analysis evaluated 5-year progression-free survival and mature overall survival in patients classified by clinical risk and HRD status.

RESULTS

Of 806 randomized patients, 74% were higher-risk and 26% were lower-risk. In higher-risk HRD-positive patients, the hazard ratio (HR) for progression-free survival was 0.46 (95% confidence interval (95% CI) 0.34 to 0.61), with 5-year progression-free survival of 35% with olaparib plus bevacizumab versus 15% with bevacizumab alone; and the HR for overall survival was 0.70 (95% CI 0.50 to 1.00), with 5-year overall survival of 55% versus 42%, respectively. In lower-risk HRD-positive patients, the HR for progression-free survival was 0.26 (95% CI 0.15 to 0.45), with 5-year progression-free survival of 72% with olaparib plus bevacizumab versus 28% with bevacizumab alone; and the HR for overall survival was 0.31 (95% CI 0.14 to 0.66), with 5-year overall survival of 88% versus 61%, respectively. No benefit was seen in HRD-negative patients regardless of clinical risk.

CONCLUSION

This post hoc analysis indicates that in patients with newly diagnosed advanced HRD-positive ovarian cancer, maintenance olaparib plus bevacizumab should not be limited to those considered at higher risk of disease progression. Five-year progression-free survival rates support long-term remission and suggest an increased potential for cure with particular benefit suggested in lower-risk HRD-positive patients.

Heterogeneity and treatment landscape of ovarian carcinoma

Ovarian carcinoma is characterized by heterogeneity at the molecular, cellular and anatomical levels, both spatially and temporally. This heterogeneity affects response to surgery and/or systemic therapy, and also facilitates inherent and acquired drug resistance. As a consequence, this tumour type is often aggressive and frequently lethal. Ovarian carcinoma is not a single disease entity and comprises various subtypes, each with distinct complex molecular landscapes that change during progression and therapy. The interactions of cancer and stromal cells within the tumour microenvironment further affects disease evolution and response to therapy. In past decades, researchers have characterized the cellular, molecular, microenvironmental and immunological heterogeneity of ovarian carcinoma. Traditional treatment approaches have considered ovarian carcinoma as a single entity. This landscape is slowly changing with the increasing appreciation of heterogeneity and the recognition that delivering ineffective therapies can delay the development of effective personalized approaches as well as potentially change the molecular and cellular characteristics of the tumour, which might lead to additional resistance to subsequent therapy. In this Review we discuss the heterogeneity of ovarian carcinoma, outline the current treatment landscape for this malignancy and highlight potentially effective therapeutic strategies in development.

An Overview of PARP Resistance in Ovarian Cancer from a Molecular and Clinical Perspective

Epithelial ovarian cancer (EOC), a primarily high-grade serous carcinoma (HGSOC), is one of the major causes of high death-to-incidence ratios of all gynecological cancers. Cytoreductive surgery and platinum-based chemotherapy represent the main treatments for this aggressive disease. Molecular characterization of HGSOC has revealed that up to 50% of cases have a deficiency in the homologous recombination repair (HRR) system, which makes these tumors sensitive to poly ADP-ribose inhibitors (PARP-is). However, drug resistance often occurs and overcoming it represents a big challenge. A number of strategies are under investigation, with the most promising being combinations of PARP-is with antiangiogenetic agents and immune checkpoint inhibitors. Moreover, new drugs targeting different pathways, including the ATR-CHK1-WEE1, the PI3K-AKT and the RAS/RAF/MEK, are under development both in phase I and II-III clinical trials. Nevertheless, there is still a long way to go, and the next few years promise to be exciting.

Poly (ADP-ribose) polymerase inhibitors (PARPi) in ovarian cancer: lessons learned and future directions

Poly (ADP-ribose) polymerase inhibitors (PARPi) represent a new standard of care in the upfront treatment of advanced epithelial ovarian cancer to the point that the vast majority of patients now receive a PARPi, alone or in combination with the anti-angiogenic bevacizumab, as part of their first-line maintenance therapy. The clinical benefit of PARPi is well established; however, much has changed since their introduction and several relevant questions have been raised and remain unresolved in the post-PARPi era. The decision-making process regarding the most appropriate first-line maintenance therapy could be challenging in clinical practice, especially in the homologous recombination-proficient setting, and several other factors need to be considered apart from the mutational status. Concerns regarding post-PARPi progression treatment have emerged, highlighting an unmet need to define a valid algorithm strategy. PARPi may not only compromise the response to further platinum due to cross-resistance mechanisms but the impact on subsequent non-platinum chemotherapy and surgery also remains unclear. Definitive results on the role of PARPi rechallenge are awaited, especially in the case of oligoprogression managed with locoregional treatment. Moreover, the updated overall survival data from the recurrent setting warrant caution in using PARPi as single agents for unselected patients. Several PARPi combination regimens are emerging for overcoming PARPi resistance and may become our new therapeutic armamentarium. This review discusses a set of clinically relevant issues in the PARPi era and provides a glimpse of future challenges and opportunities in ovarian cancer treatment.

Role of PARP Inhibitors in Cancer Immunotherapy: Potential Friends to Immune Activating Molecules and Foes to Immune Checkpoints

Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) induce cytotoxic effects as single agents in tumors characterized by defective repair of DNA double-strand breaks deriving from BRCA1/2 mutations or other abnormalities in genes associated with homologous recombination. Preclinical studies have shown that PARPi-induced DNA damage may affect the tumor immune microenvironment and immune-mediated anti-tumor response through several mechanisms. In particular, increased DNA damage has been shown to induce the activation of type I interferon pathway and up-regulation of PD-L1 expression in cancer cells, which can both enhance sensitivity to Immune Checkpoint Inhibitors (ICIs). Despite the recent approval of ICIs for a number of advanced cancer types based on their ability to reinvigorate T-cell-mediated antitumor immune responses, a consistent percentage of treated patients fail to respond, strongly encouraging the identification of combination therapies to overcome resistance. In the present review, we analyzed both established and unexplored mechanisms that may be elicited by PARPi, supporting immune reactivation and their potential synergism with currently used ICIs. This analysis may indicate novel and possibly patient-specific immune features that might represent new pharmacological targets of PARPi, potentially leading to the identification of predictive biomarkers of response to their combination with ICIs.

IOLite: phase 1b trial of doublet/triplet combinations of dostarlimab with niraparib, carboplatin-paclitaxel, with or without bevacizumab in patients with advanced cancer

BACKGROUND

Doublet combination therapies targeting immune checkpoints have shown promising efficacy in patients with advanced solid tumors, but it is unknown if rational triplet combinations will be well tolerated and associated with improved antitumor activity. The objective of this trial was to determine the recommended phase 2 doses (RP2Ds) and to assess the safety and efficacy of the programmed cell death protein 1 (PD-1) inhibitor dostarlimab in combination with (1) the poly(ADP-ribose) polymerase inhibitor niraparib with or without vascular endothelial growth factor inhibitor bevacizumab or (2) carboplatin-paclitaxel chemotherapy with or without bevacizumab, in patients with advanced cancer.

METHODS

IOLite is a multicenter, open-label, multi-arm clinical trial. Patients with advanced solid tumors were enrolled. Patients received dostarlimab in combination with niraparib with or without bevacizumab or in combination with carboplatin-paclitaxel with or without bevacizumab until disease progression, unacceptable toxicity, or withdrawal from the study. Prespecified endpoints in all parts were to evaluate the dose-limiting toxicities (DLTs), RP2Ds, pharmacokinetics (PKs), and preliminary efficacy for each combination.

RESULTS

A total of 55 patients were enrolled; patients received dostarlimab and: (1) niraparib in part A (n=22); (2) carboplatin-paclitaxel in part B (n=14); (3) niraparib plus bevacizumab in part C (n=13); (4) carboplatin-paclitaxel plus bevacizumab in part D (n=6). The RP2Ds of all combinations were determined. All combinations were safe and tolerable, with no new safety signals observed. DLTs were reported in 2, 1, 2, and 0 patients, in parts A-D, respectively. Preliminary antitumor activity was observed, with confirmed Response Evaluation Criteria in Solid Tumors v1.1 complete/partial responses reported in 4 of 22 patients (18.2%), 6 of 14 patients (42.9%), 4 of 13 patients (30.8%), and 3 of 6 (50.0%) patients, in parts A-D, respectively. Disease control rates were 40.9%, 57.1%, 84.6%, and 83.3%, in parts A-D, respectively. Dostarlimab PK was unaffected by any combinations tested. Coadministration of bevacizumab showed no impact on niraparib PKs. The overall mean PD-1 receptor occupancy was 99.0%.

CONCLUSIONS

Dostarlimab was well tolerated in both doublet and triplet regimens tested, with promising antitumor activity observed with all combinations. We observed higher disease control rates in the triplet regimens than in doublet regimens.

TRIAL REGISTRATION NUMBER

NCT03307785.

Major clinical research advances in gynecologic cancer in 2021

In the 2021 series, we not only summarized the major clinical research advances in gynecologic oncology but also added discussions to every part, based on communications at the conference. A review of cervical cancer included adjuvant treatments such as radiation and chemoradiation (concurrent or sequential) after radical hysterectomy in early cervical cancer, and immune checkpoint inhibitors in advanced, recurrent, and metastatic disease. Ovarian cancer research included studies of secondary cytoreductive surgery in platinum-sensitive recurrent ovarian cancer, and various trials of immune checkpoint inhibitors with or without vascular endothelial growth factor inhibitors and conventional chemotherapy. The rechallenge of poly (ADP-ribose) polymerase inhibitor maintenance in heavily pretreated ovarian cancer were also addressed. For uterine corpus cancer, dostarlimab (anti-programmed cell death protein 1 antibody) alone, or a tyrosine kinase inhibitor in combination with pembrolizumab for advanced, metastatic, or recurrent endometrial cancer were reviewed. The survival differences between the intensive and minimalist follow-up protocols were also described. In this review, we compared salpingectomy with delayed oophorectomy and salpingo-oophorectomy in terms of quality of life in BRCA 1 and 2 pathogenic variant carriers.

Efficacy of maintenance olaparib plus bevacizumab according to clinical risk in patients with newly diagnosed, advanced ovarian cancer in the phase III PAOLA-1/ENGOT-ov25 trial

OBJECTIVES

Adding maintenance olaparib to bevacizumab provided a significant progression-free survival (PFS) benefit in patients with newly diagnosed, advanced ovarian cancer in the randomized, double-blind PAOLA-1/ENGOT-ov25 trial (NCT02477644). We analyzed PFS by clinical risk and biomarker status.

METHODS

Patients received olaparib 300 mg twice daily for up to 24 months plus bevacizumab 15 mg/kg every 3 weeks for up to 15 months in total, or placebo plus bevacizumab. This post hoc exploratory analysis evaluated PFS in patients classified as higher risk (stage III with upfront surgery and residual disease or neoadjuvant chemotherapy; stage IV) or lower risk (stage III with upfront surgery and no residual disease), and by biomarker status.

RESULTS

Of 806 randomized patients, 74% were higher risk and 26% were lower risk. After a median 22.9 months of follow-up, PFS favored olaparib plus bevacizumab versus placebo plus bevacizumab in higher-risk patients (hazard ratio [HR] 0.60; 95% confidence interval [CI] 0.49-0.74) and lower-risk patients (0.46; 0.30-0.72). Olaparib plus bevacizumab provided a substantial PFS benefit versus bevacizumab alone in the homologous recombination deficiency (HRD)-positive subgroup (higher risk: HR 0.39; 95% CI 0.28-0.54 and lower risk: 0.15; 0.07-0.30), with 24-month PFS rates in lower-risk patients of 90% versus 43%, respectively (Kaplan-Meier estimates).

CONCLUSIONS

In PAOLA-1, maintenance olaparib plus bevacizumab provided a substantial PFS benefit in HRD-positive patients with a reduction of risk of progression or death of 61% in the higher-risk group and of 85% in the lower-risk group compared with bevacizumab alone.

Targeting DNA Repair Response Promotes Immunotherapy in Ovarian Cancer: Rationale and Clinical Application

Immune checkpoint inhibitors (ICI) have emerged as a powerful oncologic treatment modality for patients with different solid tumors. Unfortunately, the efficacy of ICI monotherapy in ovarian cancer is limited, and combination therapy provides a new opportunity for immunotherapy in ovarian cancer. DNA damage repair (DDR) pathways play central roles in the maintenance of genomic integrity and promote the progression of cancer. A deficiency in DDR genes can cause different degrees of DNA damage that enhance local antigen release, resulting in systemic antitumor immune responses. Thus, the combination of DDR inhibitors with ICI represents an attractive therapeutic strategy with the potential to improve the clinical outcomes of patients with ovarian cancer. In this review, we provide an overview of the interconnectivity between DDR pathway deficiency and immune response, summarize available clinical trials on the combination therapy in ovarian cancer, and discuss the potential predictive biomarkers that can be utilized to guide the use of combination therapy.

Immunotherapy in rare ovarian cancer

PURPOSE OF REVIEW

Ovarian cancer (OC) is a heterogeneous disease and a mounting body of evidence shows that a 'one-size-fits-all' approach is obsolete. Differences in epidemiology, tumor biology, genetic profiles and treatment responses of these different types necessitate a tumor and patient-specific approach. Ninety percentage consists of epithelial OC with 70% being high-grade serous OC. The other rarer subtypes are low-grade serous (5%), clear cell (12%), endometrioid (11%) and mucinous carcinoma (3%). The remaining 10% are nonepithelial rare OCs: germ cell (3%) and sex-cord stromal tumors (7%).

RECENT FINDINGS

Over the past few decades, the 5-year survival rates have only improved modestly, therefore novel therapies are urgently needed. Recently, immunotherapy has been introduced into clinical practice in a number of solid tumors. Although preclinical data confirm the presence of an immunogenic microenvironment in a number of ovarian tumor types, no single-agent immune checkpoint inhibitor has been approved hitherto. Identifying suitable treatment combinations, adequate patient selection and thus correct implementation of immunotherapy remain major challenges.

SUMMARY

In this review, we focus on the rationale of incorporating immune therapy in rare OC, we summarize the recent developments with preclinical data and results of clinical trials, with particular focus on rare ovarian histological subtypes.

Immunotherapy in gynecological cancers

Immunotherapy has changed the natural history of several malignancies that, a decade ago, had a very poor prognosis, such as lung cancer and melanoma. Consequently, many attempts have been done to expand the indications of immunotherapy agents, predominantly immune checkpoint inhibitors (ICIs), in other cancers, including gynecological malignancies. Alongside promising results in cervical and endometrial neoplasms, there are not clear data on the benefit of ICIs as single agent or in combination with antiangiogenic agents in ovarian cancer (OC) and ongoing trials are focusing on combining ICIs with standard chemotherapy or PARP inhibitors. This chapter summarized the evidences of ICIs in gynecological malignancies and report the ongoing trials in cervical, endometrial and OC.

Development of synthetic lethality in cancer: molecular and cellular classification

Recently, genetically targeted cancer therapies have been a topic of great interest. Synthetic lethality provides a new approach for the treatment of mutated genes that were previously considered unable to be targeted in traditional genotype-targeted treatments. The increasing researches and applications in the clinical setting made synthetic lethality a promising anticancer treatment option. However, the current understandings on different conditions of synthetic lethality have not been systematically assessed and the application of synthetic lethality in clinical practice still faces many challenges. Here, we propose a novel and systematic classification of synthetic lethality divided into gene level, pathway level, organelle level, and conditional synthetic lethality, according to the degree of specificity into its biological mechanism. Multiple preclinical findings of synthetic lethality in recent years will be reviewed and classified under these different categories. Moreover, synthetic lethality targeted drugs in clinical practice will be briefly discussed. Finally, we will explore the essential implications of this classification as well as its prospects in eliminating existing challenges and the future directions of synthetic lethality.

Front-Line Maintenance Therapy in Advanced Ovarian Cancer-Current Advances and Perspectives

Ovarian tumor is the gynecological cancer associated with the highest mortality. Most diseases are diagnosed at an advanced stage, which impairs the chances of prolonged complete remission. The standard front-line treatment of advanced stages combines surgery in an expert center with platinum-based chemotherapy. Most patients experience a relapse in the years following the initial treatment. During the last decade, anti-angiogenic agents used in the maintenance setting improved progression free survival (PFS) over chemotherapy alone. More recently, PARP inhibitors demonstrated substantial efficacy, mainly in patients with germinal or somatic BRCA mutations or other homologous recombination deficiencies (HRD), all involved in double strand DNA Damage Repair (DDR). Other therapeutic paradigms are currently being explored, including combinations of immune-checkpoints inhibitors, chemotherapy, bevacizumab and PARP inhibitors. In addition to these clinical advances, molecular characterization of the tumors and their correlations with drugs efficacy are needed to better understand which patient will benefit the most from the various treatments available to date.