Phase Ib Dose Expansion and Translational Analyses of Olaparib in Combination with Capivasertib in Recurrent Endometrial, Triple-Negative Breast, and Ovarian Cancer

Strategies for the prevention or reversal of PARP inhibitor resistance

INTRODUCTION

Advances in our understanding of tumor biology shed light on hallmarks of cancer development and progression that include dysregulated DNA damage repair (DDR) machinery. Leveraging the underlying tumor genomic instability and tumor-specific defects in DDR, Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) induced DNA damage emerges as a novel non-chemotherapy therapeutic opportunity. PARPis are currently approved in multiple tumor types, with the largest benefit seen in tumors with homologous recombination repair (HRR) deficiency, including germline and somatic mutations in BRCA1/2 genes (BRCA) and other pathway members such as PALB2 and Rad51c.

AREAS COVERED

This review article summarizes the current approval landscape and known and proposed mechanisms of resistance to PARPi. Further, therapeutic strategies to overcome PARPi resistance are discussed, including ongoing clinical trials.

EXPERT OPINION

PARPi have proven to be a safe and effective therapy and represents a cornerstone treatment across multiple solid tumor types. Elucidating innate and acquired mechanisms of resistance, coupled with the emergence of novel therapeutic options to capitalize on the activity of PARPi and prevent or reverse the acquisition of resistance, provides an opportunity to further expand the role of PARPi in cancer therapy.

Capivasertib in Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative advanced breast cancer

PURPOSE

This review discusses the role and efficacy of Capivasertib in managing Hormone Receptor-Positive (HR+) breast cancer.

SUMMARY

Breast cancer is the most prevalent type of cancer among women worldwide. This article is an in-depth analysis of advanced therapeutic options involving Capivasertib in treating HR+ Breast Cancer. It focuses on the mode of action, efficacy, clinical trials, and comparison with fulvestrant alone. This review also highlights the therapy's precision in targeting specific cancer cells. Its mechanism of action involves preventing cancer cells from growing and having a cytotoxic effect on them. It improves progression-free survival while maintaining the quality of life. The side effects can be easily managed by dose reduction or discontinuation of the drug. This article sheds light on the ongoing trials and FDA recognition.

CONCLUSION

In conclusion, Capivasertib-fulvestrant therapy shows potential as an innovative therapeutic option for HR+ breast cancer but warrants additional research, especially in randomized control trials (RCT). It resulted in longer progression-free survival compared to fulvestrant alone. Its side effect profile is minimal.

Phase II study of talazoparib in advanced cancers with BRCA1/2, DNA repair, and PTEN alterations

Cancer cells with BRCA1/2 deficiencies are sensitive to poly (ADP-ribose) polymerase (PARP) inhibitors. We evaluated the efficacy of talazoparib in DNA-Damage Repair (DDR)-altered patients. In this phase II trial, patients were enrolled onto one of four cohorts based on molecular alterations: (1) somatic BRCA1/2, (2) other homologous recombination repair pathway, (3) PTEN and (4) germline BRCA1/2. The primary endpoint was a clinical benefit rate (CBR): complete response, partial response or stable disease ≥24 weeks. 79 patients with a median of 4 lines of therapy were enrolled. CBR for cohorts 1-4 were: 32.5%, 19.7%, 9.4% and 30.6%, respectively. PTEN mutations correlated with reduced survival and a trend towards shorter time to progression.Talazoparib demonstrated clinical benefit in selected DDR-altered patients. PTEN mutations/loss patients derived limited clinical benefit. Further study is needed to determine whether PTEN is prognostic or predictive of response to PARP inhibitors.

PARP inhibitors in non-ovarian gynecologic cancers

Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPis) have transformed the treatment of ovarian cancer, particularly benefiting patients whose tumors harbor genomic events that result in impaired homologous recombination (HR) repair. The use of PARPi over recent years has expanded to include subpopulations of patients with breast, pancreatic, and prostate cancers. Their potential to benefit patients with non-ovarian gynecologic cancers is being recognized. This review examines the underlying biological rationale for exploring PARPi in non-ovarian gynecologic cancers. We consider the clinical data and place this in the context of the current treatment landscape. We review the development of PARPi strategies for treating patients with endometrial, cervical, uterine leiomyosarcoma, and vulvar cancers. Furthermore, we discuss future directions and the importance of understanding HR deficiency in the context of each cancer type.

Homologous recombination proficient subtypes of high-grade serous ovarian cancer: treatment options for a poor prognosis group

Approximately 50% of tubo-ovarian high-grade serous carcinomas (HGSCs) have functional homologous recombination-mediated (HR) DNA repair, so-called HR-proficient tumors, which are often associated with primary platinum resistance (relapse within six months after completion of first-line therapy), minimal benefit from poly(ADP-ribose) polymerase (PARP) inhibitors, and shorter survival. HR-proficient tumors comprise multiple molecular subtypes including cases with CCNE1 amplification, AKT2 amplification or CDK12 alteration, and are often characterized as "cold" tumors with fewer infiltrating lymphocytes and decreased expression of PD-1/PD-L1. Several new treatment approaches aim to manipulate these negative prognostic features and render HR-proficient tumors more susceptible to treatment. Alterations in multiple different molecules and pathways in the DNA damage response are driving new drug development to target HR-proficient cancer cells, such as inhibitors of the CDK or P13K/AKT pathways, as well as ATR inhibitors. Treatment combinations with chemotherapy or PARP inhibitors and agents targeting DNA replication stress have shown promising preclinical and clinical results. New approaches in immunotherapy are also being explored, including vaccines or antibody drug conjugates. Many approaches are still in the early stages of development and further clinical trials will determine their clinical relevance. There is a need to include HR-proficient tumors in ovarian cancer trials and to analyze them in a more targeted manner to provide further evidence for their specific therapy, as this will be crucial in improving the overall prognosis of HGSC and ovarian cancer in general.

C5aR1 inhibition reprograms tumor associated macrophages and reverses PARP inhibitor resistance in breast cancer

Although Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) have been approved in multiple diseases, including BRCA1/2 mutant breast cancer, responses are usually transient requiring the deployment of combination therapies for optimal efficacy. Here we thus explore mechanisms underlying sensitivity and resistance to PARPi using two intrinsically PARPi sensitive (T22) and resistant (T127) syngeneic murine breast cancer models in female mice. We demonstrate that tumor associated macrophages (TAM) potentially contribute to the differential sensitivity to PARPi. By single-cell RNA-sequencing, we identify a TAM_C3 cluster, expressing genes implicated in anti-inflammatory activity, that is enriched in PARPi resistant T127 tumors and markedly decreased by PARPi in T22 tumors. Rps19/C5aR1 signaling is selectively elevated in TAM_C3. C5aR1 inhibition or transferring C5aR1hi cells increases and decreases PARPi sensitivity, respectively. High C5aR1 levels in human breast cancers are associated with poor responses to immune checkpoint blockade. Thus, targeting C5aR1 may selectively deplete pro-tumoral macrophages and engender sensitivity to PARPi and potentially other therapies.

Repression of PRMT activities sensitize homologous recombination-proficient ovarian and breast cancer cells to PARP inhibitor treatment

An "induced PARP inhibitor (PARPi) sensitivity by epigenetic modulation" strategy is being evaluated in the clinic to sensitize homologous recombination (HR)-proficient tumors to PARPi treatments. To expand its clinical applications and identify more efficient combinations, we performed a drug screen by combining PARPi with 74 well-characterized epigenetic modulators that target five major classes of epigenetic enzymes. Both type I PRMT inhibitor and PRMT5 inhibitor exhibit high combination and clinical priority scores in our screen. PRMT inhibition significantly enhances PARPi treatment-induced DNA damage in HR-proficient ovarian and breast cancer cells. Mechanistically, PRMTs maintain the expression of genes associated with DNA damage repair and BRCAness and regulate intrinsic innate immune pathways in cancer cells. Analyzing large-scale genomic and functional profiles from TCGA and DepMap further confirms that PRMT1, PRMT4, and PRMT5 are potential therapeutic targets in oncology. Finally, PRMT1 and PRMT5 inhibition act synergistically to enhance PARPi sensitivity. Our studies provide a strong rationale for the clinical application of a combination of PRMT and PARP inhibitors in patients with HR-proficient ovarian or breast cancer.

Oncogenic Pathways and Targeted Therapies in Ovarian Cancer

Epithelial ovarian cancer (EOC) is one of the most aggressive forms of gynaecological malignancies. Survival rates for women diagnosed with OC remain poor as most patients are diagnosed with advanced disease. Debulking surgery and platinum-based therapies are the current mainstay for OC treatment. However, and despite achieving initial remission, a significant portion of patients will relapse because of innate and acquired resistance, at which point the disease is considered incurable. In view of this, novel detection strategies and therapeutic approaches are needed to improve outcomes and survival of OC patients. In this review, we summarize our current knowledge of the genetic landscape and molecular pathways underpinning OC and its many subtypes. By examining therapeutic strategies explored in preclinical and clinical settings, we highlight the importance of decoding how single and convergent genetic alterations co-exist and drive OC progression and resistance to current treatments. We also propose that core signalling pathways such as the PI3K and MAPK pathways play critical roles in the origin of diverse OC subtypes and can become new targets in combination with known DNA damage repair pathways for the development of tailored and more effective anti-cancer treatments.

New clinical trial design in precision medicine: discovery, development and direction

In the era of precision medicine, it has been increasingly recognized that individuals with a certain disease are complex and different from each other. Due to the underestimation of the significant heterogeneity across participants in traditional "one-size-fits-all" trials, patient-centered trials that could provide optimal therapy customization to individuals with specific biomarkers were developed including the basket, umbrella, and platform trial designs under the master protocol framework. In recent years, the successive FDA approval of indications based on biomarker-guided master protocol designs has demonstrated that these new clinical trials are ushering in tremendous opportunities. Despite the rapid increase in the number of basket, umbrella, and platform trials, the current clinical and research understanding of these new trial designs, as compared with traditional trial designs, remains limited. The majority of the research focuses on methodologies, and there is a lack of in-depth insight concerning the underlying biological logic of these new clinical trial designs. Therefore, we provide this comprehensive review of the discovery and development of basket, umbrella, and platform trials and their underlying logic from the perspective of precision medicine. Meanwhile, we discuss future directions on the potential development of these new clinical design in view of the "Precision Pro", "Dynamic Precision", and "Intelligent Precision". This review would assist trial-related researchers to enhance the innovation and feasibility of clinical trial designs by expounding the underlying logic, which be essential to accelerate the progression of precision medicine.

Capivasertib: First Approval

Capivasertib (Truqap™) is an orally available, small-molecule pan-AKT inhibitor being developed by AstraZeneca for the treatment of various cancers, including breast and prostate cancers. Capivasertib received its first approval, in the USA, in November 2023 for use in combination with fulvestrant for the treatment of adult patients with hormone receptor (HR)-positive, human epidermal growth factor 2 (HER2)-negative, locally advanced or metastatic breast cancer with one or more PIK3CA/AKT1/PTEN-alterations following progression on at least one endocrine-based regimen in the metastatic setting or recurrence on or within 12 months of completing adjuvant therapy. Capivasertib is also under regulatory review for HR-positive, HER2-negative breast cancer in the EU and several other countries, and in phase III clinical development for use (in combination with other anti-cancer agents) in the treatment of triple-negative breast cancer, castration-resistant prostate cancer, and hormone-sensitive prostate cancer. This article summarizes the milestones in the development of capivasertib leading to this first approval for HR-positive, HER2-negative, locally advanced or metastatic breast cancer.

Small molecule agents for triple negative breast cancer: Current status and future prospects

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with poor prognosis. The number of cases increased by 2.26 million in 2020, making it the most commonly diagnosed cancer type in the world. TNBCs lack hormone receptor (HR) and human epidermal growth factor 2 (HER2), which limits treatment options. Currently, paclitaxel-based drugs combined with other chemotherapeutics remain the main treatment for TNBC. There is currently no consensus on the best therapeutic regimen for TNBC. However, there have been successful clinical trials exploring large-molecule monoclonal antibodies, small-molecule targeted drugs, and novel antibody-drug conjugate (ADC). Although monoclonal antibodies have produced clinical success, their large molecular weight can limit therapeutic benefits. It is worth noting that in the past 30 years, the FDA has approved small molecule drugs for HER2-positive breast cancers. The lack of effective targets and the occurrence of drug resistance pose significant challenges in the treatment of TNBC. To improve the prognosis of TNBC, it is crucial to search for effective targets and to overcome drug resistance. This review examines the clinical efficacy, adverse effects, resistance mechanisms, and potential solutions of targeted small molecule drugs in both monotherapies and combination therapies. New therapeutic targets, including nuclear export protein 1 (XPO1) and hedgehog (Hh), are emerging as potential options for researchers and become integrated into clinical trials for TNBC. Additionally, there is growing interest in the potential of targeted protein degradation chimeras (PROTACs), degraders of rogue proteins, as a future therapy direction. This review provides potentially valuable insights with clinical implications.

Bevacizumab increases the sensitivity of olaparib to homologous recombination-proficient ovarian cancer by suppressing CRY1 via PI3K/AKT pathway

PARP inhibitors have changed the management of advanced high-grade epithelial ovarian cancer (EOC), especially homologous recombinant (HR)-deficient advanced high-grade EOC. However, the effect of PARP inhibitors on HR-proficient (HRP) EOC is limited. Thus, new therapeutic strategy for HRP EOC is desired. In recent clinical study, the combination of PARP inhibitors with anti-angiogenic agents improved therapeutic efficacy, even in HRP cases. These data suggested that anti-angiogenic agents might potentiate the response to PARP inhibitors in EOC cells. Here, we demonstrated that anti-angiogenic agents, bevacizumab and cediranib, increased the sensitivity of olaparib in HRP EOC cells by suppressing HR activity. Most of the γ-H2AX foci were co-localized with RAD51 foci in control cells. However, most of the RAD51 were decreased in the bevacizumab-treated cells. RNA sequencing showed that bevacizumab decreased the expression of CRY1 under DNA damage stress. CRY1 is one of the transcriptional coregulators associated with circadian rhythm and has recently been reported to regulate the expression of genes required for HR in cancer cells. We found that the anti-angiogenic agents suppressed the increase of CRY1 expression by inhibiting VEGF/VEGFR/PI3K pathway. The suppression of CRY1 expression resulted in decrease of HR activity. In addition, CRY1 inhibition also sensitized EOC cells to olaparib. These data suggested that anti-angiogenic agents and CRY1 inhibitors will be the promising candidate in the combination therapy with PARP inhibitors in HR-proficient EOC.

Exploring the role of PI3K/AKT/mTOR inhibitors in hormone-related cancers: A focus on breast and prostate cancer

Breast cancer (BC) and prostate cancer (PC) are at the top of the list when it comes to the most common types of cancers worldwide. The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway is important, in that it strongly influences the development and progression of these tumors. Previous studies have emphasized the key role of inhibitors of the PIK3/AKT/mTOR signaling pathway in the treatment of BC and PC, and it remains to be a crucial method of treatment. In this review, the inhibitors of these signaling pathways are compared, as well as their effectiveness in therapy and potential as therapeutic agents. The use of these inhibitors as polytherapy is evaluated, especially with the use of hormonal therapy, which has shown promising results.

Health-related quality of life and patient-centred outcomes with COVID-19 vaccination in patients with breast cancer and gynaecological malignancies

Introduction

Safety and tolerability of COVID-19 vaccines were demonstrated by several clinical trials which led to the first FDA/EMA approvals in 2021. Because of mass immunizations, most social restrictions were waived with effects on quality of life. Therefore, our a-priori hypothesis was that COVID-19 vaccination impacted the health-related quality of life (HR-QoL) in patients with breast and gynecological cancer.

Methods

From March 15th until August 11th, 2022, fully vaccinated patients with breast and gynecological cancer treated in the oncological outpatient clinics of the Department of Obstetrics and Gynecology, LMU University Hospital, Munich, Germany filled out a vaccine related QoL survey. Patients were asked about demographics (age, comorbidities), clinical parameters related to previous COVID-19 infections, and HR-QoL related parameters (living situation, responsibilities in everyday life). Subsequently, a questionnaire with 12 items was designed using a 5-point Likert scale (0 - strongly disagree/4 - strongly agree), covering the aspects health and therapy, social environment, participation in everyday life and overall assessment.

Results

By August 11th, 2022, 108 out of 114 (94.7%) patients had received at least three doses of COVID-19 vaccine and six patients at least two doses. More than half of the surveyed patients were >55y (52.6%; mean: 55.1y, range 29-86y). Patients with breast cancer (n= 83) had early (59.0%) or metastatic cancer (41.0%); gynecological cancers (n=31) also included metastatic (54.8%) and non-metastatic cancer (45.2%). 83.3% of the patients stated that COVID-19 vaccination had a positive impact on their HR-QoL. Furthermore, 29 patients (25.4%) had undergone a COVID-19 infection. These patients reported self-limiting symptoms for a median duration of 5.9 days and no hospital admissions were registered.

Conclusions

Our study demonstrates that vaccination against COVID-19 was positively associated with HR-QoL in patients with breast and gynecological cancer. Furthermore, vaccinated patients who underwent COVID-19 disease experienced only self-limiting symptoms.

Combination Treatment Strategies to Overcome PARP Inhibitor Resistance

Poly(ADP-ribose) polymerase (PARP) enzymes have been shown to be essential for DNA repair pathways, including homologous recombination repair (HRR). Cancers with HRR defects (e.g., BRCA1 and BRCA2 mutations) are targets for PARP inhibitors (PARPis) based on the exploitation of "synthetic lethality". As a result, PARPis offer a promising treatment option for advanced ovarian and breast cancers with deficiencies in HRR. However, acquired resistance to PARPis has been reported for most tumors, and not all patients with BRCA1/2 mutations respond to PARPis. Therefore, the formulation of effective treatment strategies to overcome resistance to PARPis is urgently necessary. This review summarizes the molecular mechanism of therapeutic action and resistance to PARPis, in addition to emerging combination treatment options involving PARPis.

The Breast Cancer Proteome and Precision Oncology

The goal of precision oncology is to translate the molecular features of cancer into predictive and prognostic tests that can be used to individualize treatment leading to improved outcomes and decreased toxicity. Success for this strategy in breast cancer is exemplified by efficacy of trastuzumab in tumors overexpressing ERBB2 and endocrine therapy for tumors that are estrogen receptor positive. However, other effective treatments, including chemotherapy, immune checkpoint inhibitors, and CDK4/6 inhibitors are not associated with strong predictive biomarkers. Proteomics promises another tier of information that, when added to genomic and transcriptomic features (proteogenomics), may create new opportunities to improve both treatment precision and therapeutic hypotheses. Here, we review both mass spectrometry-based and antibody-dependent proteomics as complementary approaches. We highlight how these methods have contributed toward a more complete understanding of breast cancer and describe the potential to guide diagnosis and treatment more accurately.

PARP inhibitors: enhancing efficacy through rational combinations

Poly (ADP-ribose) polymerase inhibitors (PARPi) have significantly changed the treatment landscape for tumours harbouring defects in genes involved in homologous repair (HR) such as BRCA1 and BRCA2. Despite initial responsiveness to PARPi, tumours eventually develop resistance through a variety of mechanisms. Rational combination strategies involving PARPi have been explored and are in various stages of clinical development. PARPi combinations have the potential to enhance efficacy through synergistic activity, and also potentially sensitise innately PARPi-resistant tumours to PARPi. Initial combinations involving PARPi with chemotherapy were hindered by significant overlapping haematologic toxicity, but newer combinations with fewer toxicities and more targeted approaches are undergoing evaluation. In this review, we discuss the mechanisms of PARPi resistance and review the rationale and clinical evidence for various PARPi combinations including combinations with chemotherapy, immunotherapy, and targeted therapies. We also highlight emerging PARPi combinations with promising preclinical evidence.

A Phase Ib, Open-label Study Evaluating the Safety and Efficacy of Ipatasertib plus Rucaparib in Patients with Metastatic Castration-resistant Prostate Cancer

PURPOSE

To report the safety and efficacy of ipatasertib (AKT inhibitor) combined with rucaparib (PARP inhibitor) in patients with metastatic castration-resistant prostate cancer (mCRPC) previously treated with second-generation androgen receptor inhibitors.

PATIENTS AND METHODS

In this two-part phase Ib trial (NCT03840200), patients with advanced prostate, breast, or ovarian cancer received ipatasertib (300 or 400 mg daily) plus rucaparib (400 or 600 mg twice daily) to assess safety and identify a recommended phase II dose (RP2D). A part 1 dose-escalation phase was followed by a part 2 dose-expansion phase in which only patients with mCRPC received the RP2D. The primary efficacy endpoint was prostate-specific antigen (PSA) response (≥50% reduction) in patients with mCRPC. Patients were not selected on the basis of tumor mutational status.

RESULTS

Fifty-one patients were enrolled (part 1 = 21; part 2 = 30). Ipatasertib 400 mg daily plus rucaparib 400 mg twice daily was the selected RP2D, received by 37 patients with mCRPC. Grade 3/4 adverse events occurred in 46% (17/37) of patients, with one grade 4 adverse event (anemia, deemed related to rucaparib) and no deaths. Adverse events leading to treatment modification occurred in 70% (26/37). The PSA response rate was 26% (9/35), and the objective response rate per Response Criteria in Solid Tumors (RECIST) 1.1 was 10% (2/21). Median radiographic progression-free survival per Prostate Cancer Working Group 3 criteria was 5.8 months [95% confidence interval (CI), 4.0-8.1], and median overall survival was 13.3 months (95% CI, 10.9-not evaluable).

CONCLUSIONS

Ipatasertib plus rucaparib was manageable with dose modification but did not demonstrate synergistic or additive antitumor activity in previously treated patients with mCRPC.

Targeting DNA Damage Repair and Immune Checkpoint Proteins for Optimizing the Treatment of Endometrial Cancer

The dependence of cancer cells on the DNA damage response (DDR) pathway for the repair of endogenous- or exogenous-factor-induced DNA damage has been extensively studied in various cancer types, including endometrial cancer (EC). Targeting one or more DNA damage repair protein with small molecules has shown encouraging treatment efficacy in preclinical and clinical models. However, the genes coding for DDR factors are rarely mutated in EC, limiting the utility of DDR inhibitors in this disease. In the current review, we recapitulate the functional role of the DNA repair system in the development and progression of cancer. Importantly, we discuss strategies that target DDR proteins, including PARP, CHK1 and WEE1, as monotherapies or in combination with cytotoxic agents in the treatment of EC and highlight the compounds currently being evaluated for their efficacy in EC in clinic. Recent studies indicate that the application of DNA damage agents in cancer cells leads to the activation of innate and adaptive immune responses; targeting immune checkpoint proteins could overcome the immune suppressive environment in tumors. We further summarize recently revolutionized immunotherapies that have been completed or are now being evaluated for their efficacy in advanced EC and propose future directions for the development of DDR-based cancer therapeutics in the treatment of EC.

Triumphs and challenges in exploiting poly(ADP-ribose) polymerase inhibition to combat triple-negative breast cancer

Poly(ADP-ribose) polymerase 1 (PARP1) regulates a myriad of DNA repair mechanisms to preserve genomic integrity following DNA damage. PARP inhibitors (PARPi) confer synthetic lethality in malignancies with a deficiency in the homologous recombination (HR) pathway. Patients with triple-negative breast cancer (TNBC) fail to respond to most targeted therapies because their tumors lack expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Certain patients with TNBC harbor mutations in HR mediators such as breast cancer susceptibility gene 1 (BRCA1) and breast cancer susceptibility gene 2 (BRCA2), enabling them to respond to PARPi. PARPi exploits the synthetic lethality of BRCA-mutant cells. However, de novo and acquired PARPi resistance frequently ensue. In this review, we discuss the roles of PARP in mediating DNA repair processes in breast epithelial cells, mechanisms of PARPi resistance in TNBC, and recent advances in the development of agents designed to overcome PARPi resistance in TNBC.

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.

The role of PARP inhibitor combination therapy in ovarian cancer

The use of PARP inhibitors (PARPi) has transformed the care of advanced high-grade serous/endometrioid ovarian cancer. PARPi are now available to patients in both the first-line and recurrent platinum-sensitive disease settings; therefore, most patients will receive PARPi at some point in their treatment pathway. The majority of this expanding population of patients eventually acquire resistance to PARPi, in addition to those with primary PARPi resistance. We discuss the rationale behind developing combination therapies, to work synergistically with PARPi and overcome mechanisms of resistance to restore drug sensitivity, and clinical evidence of their efficacy to date.

PARP Inhibitors in Breast and Ovarian Cancer

Poly (ADP-ribose) polymerase (PARP) inhibitors are one of the most successful examples of clinical translation of targeted therapies in medical oncology, and this has been demonstrated by their effective management of BRCA1/BRCA2 mutant cancers, most notably in breast and ovarian cancers. PARP inhibitors target DNA repair pathways that BRCA1/2-mutant tumours are dependent upon. Inhibition of the key components of these pathways leads to DNA damage triggering subsequent critical levels of genomic instability, mitotic catastrophe and cell death. This ultimately results in a synthetic lethal relationship between BRCA1/2 and PARP, which underpins the effectiveness of PARP inhibitors. Despite the early and dramatic response seen with PARP inhibitors, patients receiving them often develop treatment resistance. To date, data from both clinical and preclinical studies have highlighted multiple resistance mechanisms to PARP inhibitors, and only by understanding these mechanisms are we able to overcome the challenges. The focus of this review is to summarise the underlying mechanisms underpinning treatment resistance to PARP inhibitors and to aid both clinicians and scientists to develop better clinically applicable assays to better select patients who would derive the greatest benefit as well as develop new novel/combination treatment strategies to overcome these mechanisms of resistance. With a better understanding of PARP inhibitor resistance mechanisms, we would not only be able to identify a subset of patients who are unlikely to benefit from therapy but also to sequence our treatment paradigm to avoid and overcome these resistance mechanisms.

Addressing the Reciprocal Crosstalk between the AR and the PI3K/AKT/mTOR Signaling Pathways for Prostate Cancer Treatment

The reduction in androgen synthesis and the blockade of the androgen receptor (AR) function by chemical castration and AR signaling inhibitors represent the main treatment lines for the initial stages of prostate cancer. Unfortunately, resistance mechanisms ultimately develop due to alterations in the AR pathway, such as gene amplification or mutations, and also the emergence of alternative pathways that render the tumor less or, more rarely, completely independent of androgen activation. An essential oncogenic axis activated in prostate cancer is the phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, as evidenced by the frequent alterations of the negative regulator phosphatase and tensin homolog (PTEN) and by the activating mutations in PI3K subunits. Additionally, crosstalk and reciprocal feedback loops between androgen signaling and the PI3K/AKT/mTOR signaling cascade that activate pro-survival signals and play an essential role in disease recurrence and progression have been evidenced. Inhibitors addressing different players of the PI3K/AKT/mTOR pathway have been evaluated in the clinic. Only a limited benefit has been reported in prostate cancer up to now due to the associated side effects, so novel combination approaches and biomarkers predictive of patient response are urgently needed. Here, we reviewed recent data on the crosstalk between AR signaling and the PI3K/AKT/mTOR pathway, the selective inhibitors identified, and the most advanced clinical studies, with a focus on combination treatments. A deeper understanding of the complex molecular mechanisms involved in disease progression and treatment resistance is essential to further guide therapeutic approaches with improved outcomes.

Rational Combinations of PARP Inhibitors with HRD-Inducing Molecularly Targeted Agents

Cancers with wild-type BRCA, homologous recombination proficiency, or de novo or acquired resistance to PARP inhibition represent a growing population of patients who may benefit from combinatorial PARP inhibitor strategies. We review targeted inhibitors of angiogenesis, epigenetic regulators, and PI3K, MAPK, and other cellular signaling pathways as inducers of homologous recombination deficiency, providing support for the use of PARP inhibitors in contexts not previously considered susceptible to PARP inhibition.

Kinase Inhibitors in the Treatment of Ovarian Cancer: Current State and Future Promises

Ovarian cancer is the deadliest gynecological cancer, the high-grade serous ovarian carcinoma (HGSC) being its most common and most aggressive form. Despite the latest therapeutical advancements following the introduction of vascular endothelial growth factor receptor (VEGFR) targeting angiogenesis inhibitors and poly-ADP-ribose-polymerase (PARP) inhibitors to supplement the standard platinum- and taxane-based chemotherapy, the expected overall survival of HGSC patients has not improved significantly from the five-year rate of 42%. This calls for the development and testing of more efficient treatment options. Many oncogenic kinase-signaling pathways are dysregulated in HGSC. Since small-molecule kinase inhibitors have revolutionized the treatment of many solid cancers due to the generality of the increased activation of protein kinases in carcinomas, it is reasonable to evaluate their potential against HGSC. Here, we present the latest concluded and on-going clinical trials on kinase inhibitors in HGSC, as well as the recent work concerning ovarian cancer patient organoids and xenograft models. We discuss the potential of kinase inhibitors as personalized treatments, which would require comprehensive assessment of the biological mechanisms underlying tumor spread and chemoresistance in individual patients, and their connection to tumor genome and transcriptome to establish identifiable subgroups of patients who are most likely to benefit from a given therapy.

Efficacy evaluation of multi-immunotherapy in ovarian cancer: From bench to bed

Ovarian cancer, one of the most common gynecological malignancies, is characterized by high mortality and poor prognosis. Cytoreductive surgery and chemotherapy remain the mainstay of ovarian cancer treatment, and most women experience recurrence after standard care therapies. There is compelling evidence that ovarian cancer is an immunogenic tumor. For example, the accumulation of tumor-infiltrating lymphocytes is associated with increased survival, while increases in immunosuppressive regulatory T cells are correlated with poor clinical outcomes. Therefore, immunotherapies targeting components of the tumor microenvironment have been gradually integrated into the existing treatment options, including immune checkpoint blockade, adoptive cell therapy, and cancer vaccines. Immunotherapies have changed guidelines for maintenance treatment and established a new paradigm in ovarian cancer treatment. Despite single immunotherapies targeting DNA repair mechanisms, immune checkpoints, and angiogenesis bringing inspiring efficacy, only a subset of patients can benefit much from it. Thus, the multi-immunotherapy investigation remains an active area for ovarian cancer treatment. The current review provides an overview of various clinically oriented forms of multi-immunotherapy and explores potentially effective combinational therapies for ovarian cancer.

Novel therapeutic approaches in GEP-NETs based on genetic and epigenetic alterations

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are heterogeneous malignancies with distinct prognosis based on primary tumor localization, grade, stage and functionality. Surgery remains the only curative option in localized tumors, but systemic therapy is the mainstay of treatment for patients with advanced disease. For decades, the therapeutic landscape of GEP-NETs was limited to chemotherapy regimens with low response rates. The arrival of novel agents such as somatostatin analogues, peptide receptor radionuclide therapy, tyrosine kinase inhibitors or mTOR-targeted drugs, has changed the therapeutic paradigm of GEP-NETs. However, the efficacy of these agents is limited in time and there is scarce knowledge of optimal treatment sequencing. In recent years, massive parallel sequencing techniques have started to unravel the genomic intricacies of these tumors, allowing us to better understand the mechanisms of resistance to current treatments and to develop new targeted agents that will hopefully start an era for personalized treatment in NETs. In this review we aim to summarize the most relevant genomic aberrations and signaling pathways underlying GEP-NET tumorigenesis and potential therapeutic strategies derived from them.

PARP Inhibitors for Breast Cancer: Germline BRCA1/2 and Beyond

Simple Summary

Poly-adenosine diphosphate ribose polymerase (PARP) inhibitors (PARPi) are effective against tumors with mutations in DNA repair genes, most commonly in the BRCA1 and BRCA2 genes. Because these tumors are unable to repair their DNA, PARPi have been used to target DNA repair pathways and are useful in the treatment of breast cancers with some of these alterations. There are two FDA-approved PARPi for patients with breast cancer—olaparib and talazoparib. The data on olaparib and talazoparib in the treatment of breast cancer are summarized in this review, and we also explore potential future applications of PARPi beyond inherited BRCA mutations.

Abstract

Poly-adenosine diphosphate ribose polymerase (PARP) inhibitors (PARPi) are approved for BRCA1/2 carriers with HER2-negative breast cancer in the adjuvant setting with a high risk of recurrence as well as the metastatic setting. However, the indications for PARPi are broader for patients with other cancer types (e.g., prostate and ovarian cancer), involving additional biomarkers (e.g., ATM, PALB2, and CHEK) and genomic instability scores. Herein, we summarize the data on PARPi and breast cancer and discuss their use beyond BRCA carriers.

PARP inhibitors as single agents and in combination therapy: the most promising treatment strategies in clinical trials for BRCA-mutant ovarian and triple-negative breast cancers

INTRODUCTION

Poly (ADP-ribose) polymerase inhibitors (PARPis) are an exciting class of agents that have shown efficacy, particularly for BRCA-mutant triple-negative breast cancer (TNBC) and high-grade serous ovarian cancer (HGSOC). However, most patients who receive PARPi as their standard of care therapy inevitably develop resistance and this underscores the need to identify additional targets that can circumvent such resistance. Combination treatment strategies have been developed in preclinical and clinical studies to address the challenges of efficacy and resistance.

AREAS COVERED

This review examines completed or ongoing clinical trials of PARPi mono- and combination therapies. PARPi monotherapy in HER2 negative breast (HR+ and TNBC subtypes) and ovarian cancer is a focal point. The authors propose potential strategies that might overcome resistance to PARPi and discuss key questions and future directions.

EXPERT OPINION

While the advent of PARPis has significantly improved the treatment of tumors with defects in DNA damage and repair pathways, careful patient selection will be essential to enhance these treatments. The identification of molecular biomarkers to predict disease response and progression is an endeavor.

"The emerging role of capivasertib in breast cancer"

Over 50% of breast tumors harbor alterations in one or more genes of the phosphatidylinositol 3-kinase (PI3K) pathway including PIK3CA mutations (31%), PTEN loss (34%), PTEN mutations (5%) and AKT1 mutations (3%). While PI3K and mTOR inhibitors are already approved in advanced breast cancer, AKT inhibitors have been recently developed as a new therapeutic approach. Capivasertib (AZD5363) is a novel, selective ATP-competitive pan-AKT kinase inhibitor that exerts similar activity against the three AKT isoforms, AKT1, AKT2, and AKT3. Preclinical studies demonstrated efficacy of capivasertib in breast cancer cell lines as a single agent or in combination with anti-HER2 agents and endocrine treatment, especially in tumors with PIK3CA or MTOR alterations. Phase I/II studies demonstrated greater efficacy when capivasertib was co-administered with paclitaxel, fulvestrant in hormone receptor (HR)-positive, HER2-negative breast cancer or olaparib. The recommended phase II dose of capivasertib as monotherapy was 480 mg bid on a 4-days-on, 3-days-off dosing schedule. Toxicity profile proved to be manageable with hyperglycemia (20–24%), diarrhea (14–17%) and maculopapular rash (11–16%) being the most common grade ≥3 adverse events. Ongoing Phase III trials of capivasertib in combination with fulvestrant (CAPItello-291), CDK4/6 inhibitor palbociclib (CAPItello-292) and paclitaxel (CAPItello- 290) will better clarify the therapeutic role of capivasertib in breast cancer.

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Phosphatidylinositol-3-kinase (PI3K)/Akt (PI3K/AKT) pathway is one of the most commonly altered pathways in breast cancer.

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Capivasertib (AZD5363) is a highly potent Akt kinase inhibitor with activity against the three isoforms AKT1, AKT2, and AKT3.

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Preclinical studies demonstrated efficacy of capivasertib either alone or in combination with anti-HER2 agents, chemotherapy and endocrine treatment.

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Dose-limiting toxicities include hyperglycemia (20–24%), diarrhea (14–17%) and maculopapular rash (11–16%).

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Capivasertib increased susceptibility to paclitaxel (PAKT, BEECH), fulvestrant (NCT01226316, FAKTION) or Olaparib (ComPAKT).

PARP inhibitors in ovarian cancer: overcoming resistance with combination strategies

The use of PARP inhibitors (PARPi) in patients with epithelial ovarian cancer is expanding, with the transition from use in recurrent disease to the first-line setting. This is accompanied with an increasing population of patients who develop acquired PARPi resistance. Coupled with those patients with primary PARPi resistance, there is an urgent need to better understand mechanisms of resistance and identify means to overcome this resistance. Combination therapy offers the potential to overcome innate and acquired resistance, by either working synergistically with PARPi or by restoring homologous recombination deficiency, targeting the homologous recombination repair pathway through an alternate strategy. We discuss mechanisms of PARPi resistance and data on novel combinations which may restore PARPi sensitivity.

Characterization of anticancer drug resistance by reverse-phase protein array: new targets and strategies

INTRODUCTION

Drug resistance is the main barrier to achieving cancer cures with medical therapy. Cancer drug resistance occurs, in part, due to adaptation of the tumor and microenvironment to therapeutic stress at a proteomic level. Reverse-phase protein arrays (RPPA) are well suited to proteomic analysis of drug resistance due to high sample throughput, sensitive detection of phosphoproteins, and validation for a large number of critical cellular pathways.

AREAS COVERED

This review summarizes contributions of RPPA to understanding and combating drug resistance. In particular, contributions of RPPA to understanding resistance to PARP inhibitors, BRAF inhibitors, immune checkpoint inhibitors, and breast cancer investigational therapies are discussed. Articles reviewed were identified by MEDLINE, Scopus, and Cochrane search for keywords 'proteomics,' 'reverse-phase protein array,' 'drug resistance,' 'PARP inhibitor,' 'BRAF inhibitor,' 'immune checkpoint inhibitor,' and 'I-SPY' spanning October 1, 1960 - October 1, 2021.

EXPERT OPINION

Precision oncology has thus far failed to convert the armament of targeted therapies into durable responses for most patients, highlighting that genetic sequencing alone is insufficient to guide therapy selection and overcome drug resistance. Combined genomic and proteomic analyses paired with creative drug combinations and dosing strategies hold promise for maturing precision oncology into an era of improved patient outcomes.

Precision Medicine for BRCA/PALB2-Mutated Pancreatic Cancer and Emerging Strategies to Improve Therapeutic Responses to PARP Inhibition

Simple Summary

For the small subset of pancreatic ductal adenocarcinoma (PDAC) patients with loss-of-function mutations to BRCA1/2 or PALB2, both first-line and maintenance therapy differs significantly. These mutations confer a loss of double-strand break DNA homologous recombination (HR), substantially altering drug sensitivities. In this review, we discuss the current treatment guidelines for PDAC tumors deficient in HR, as well as newly emerging strategies to improve drug responses in this population. We also highlight additional patient populations in which these strategies may also be effective, and novel strategies aiming to confer similar drug sensitivity to tumors proficient in HR repair.

Abstract

Pancreatic cancer is projected to become the second leading cause of cancer-related death by 2030. As patients typically present with advanced disease and show poor responses to broad-spectrum chemotherapy, overall survival remains a dismal 10%. This underscores an urgent clinical need to identify new therapeutic approaches for PDAC patients. Precision medicine is now the standard of care for several difficult-to-treat cancer histologies. Such approaches involve the identification of a clinically actionable molecular feature, which is matched to an appropriate targeted therapy. Selective poly (ADP-ribose) polymerase (PARP) inhibitors such as Niraparib, Olaparib, Talazoparib, Rucaparib, and Veliparib are now approved for several cancers with loss of high-fidelity double-strand break homologous recombination (HR), namely those with deleterious mutations to BRCA1/2, PALB2, and other functionally related genes. Recent evidence suggests that the presence of such mutations in pancreatic ductal adenocarcinoma (PDAC), the most common and lethal pancreatic cancer histotype, significantly alters drug responses both with respect to first-line chemotherapy and maintenance therapy. In this review, we discuss the current treatment paradigm for PDAC tumors with confirmed deficits in double-strand break HR, as well as emerging strategies to both improve responses to PARP inhibition in HR-deficient PDAC and confer sensitivity to tumors proficient in HR repair.

Therapeutic Targeting of DNA Damage Response in Cancer

DNA damage response (DDR) is critical to ensure genome stability, and defects in this signaling pathway are highly associated with carcinogenesis and tumor progression. Nevertheless, this also provides therapeutic opportunities, as cells with defective DDR signaling are directed to rely on compensatory survival pathways, and these vulnerabilities have been exploited for anticancer treatments. Following the impressive success of PARP inhibitors in the treatment of BRCA-mutated breast and ovarian cancers, extensive research has been conducted toward the development of pharmacologic inhibitors of the key components of the DDR signaling pathway. In this review, we discuss the key elements of the DDR pathway and how these molecular components may serve as anticancer treatment targets. We also summarize the recent promising developments in the field of DDR pathway inhibitors, focusing on novel agents beyond PARP inhibitors. Furthermore, we discuss biomarker studies to identify target patients expected to derive maximal clinical benefits as well as combination strategies with other classes of anticancer agents to synergize and optimize the clinical benefits.