Comparative efficacy and safety of CDK4/6 and PI3K/AKT/mTOR inhibitors in women with hormone receptor-positive, HER2-negative metastatic breast cancer: a systematic review and network meta-analysis

A network meta-analysis of efficacy and safety for first-line and second/further-line therapies in postmenopausal women with hormone receptor-positive, HER2-negative, advanced breast cancer

BACKGROUND

Hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR + /HER2 -) advanced breast cancer is a prevalent subtype among postmenopausal women. Despite the growing number of randomized clinical trials (RCTs) exploring this topic, the efficacy and safety of first-line and second/further-line treatments remain uncertain. Accordingly, our aim was to conduct a comprehensive evaluation of the efficacy and safety of these therapies through network meta-analysis.

METHODS

RCTs were identified by searching Pubmed, Embase, and major cancer conferences. The efficacy of interventions was assessed using the hazard ratios (HRs) of progression-free survival (PFS) and overall survival (OS), while safety was indicated by the incidence of any grade adverse events (AEs), grade 3-5 AEs, AEs leading to treatment discontinuation, and AEs leading to death. Both time-variant HRs fractional polynomial models and time-invariant HRs Cox-proportional hazards models were considered for handling time-to-event data. Safety indicators were analyzed using Bayesian network meta-analysis. Additionally, subgroup analyses were conducted based on patient characteristics.

RESULTS

A total of 41 RCTs (first-line 17, second/further-lines 27) were included in the analysis. For first-line treatment, the addition of Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors to endocrine therapy significantly improved therapeutic efficacy in terms of both PFS and OS, demonstrating the best performance across all mechanisms. Specifically, the combination of Abemaciclib and Letrozole demonstrated the most favorable performance in terms of PFS, while Ribociclib plus Fulvestrant yielded the best outcomes in OS. Incorporating the immune checkpoint inhibitor Avelumab into the regimen with CDK4/6 inhibitors and selective estrogen receptor degraders significantly enhanced both PFS and OS in second-line or later treatments. Regarding safety, endocrine monotherapy performed well. Regarding safety, endocrine monotherapy performed well. There is mounting evidence suggesting that most CDK4/6 inhibitors may demonstrate poorer performance with respect to hematologic AEs. However, additional evidence is required to further substantiate these findings.

CONCLUSIONS

CDK4/6 inhibitors, combined with endocrine therapy, are pivotal in first-line treatment due to their superior efficacy and manageable AEs. For second/further-line treatment, adding immune checkpoint inhibitors to CDK4/6 inhibitors plus endocrine therapy may produce promising results. However, to reduce the results' uncertainty, further trials comparing these novel treatments are warranted.

TRIAL REGISTRATION

Registration number: PROSPERO (CRD42022377431).

CDK4/6 inhibitors, PI3K/mTOR inhibitors, and HDAC inhibitors as second-line treatments for hormone receptor-positive, HER2-negative advanced breast cancer: a network meta-analysis

BACKGROUND

This study sought to compare the benefits and safety of agents including Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) inhibitors, and histone deacetylase (HDAC) inhibitors as second-line treatments for these patients by conducting a comprehensive systematic review and network meta-analysis.

METHODS

The Medline, Embase and Cochrane Library databases were searched for randomized trials comparing CDK4/6 inhibitors, PI3K/mTOR inhibitors, or HDAC inhibitors vs. placebo with the addition of exemestane or fulvestrant as second-line treatments in patients with HR + advanced breast cancer up to December 16, 2021. Outcomes of interest were progression-free survival (PFS), overall response rate (ORR), overall survival (OS), clinical benefit rate (CBR), and grade 3-4 adverse drug events (ADEs). The present study was conducted according to the Cochrane Collaboration and PRISMA statements. The overall effect was pooled using the random effects model.

RESULTS

Seventeen studies with a total of 9,100 participants were included in the current study. Compared with placebo plus fulvestrant, PFS was significantly improved by CDK4/6 inhibitor plus fulvestrant, mTOR inhibitor plus fulvestrant, mTOR inhibitor plus exemestane, and PI3K inhibitor plus fulvestrant, but not HDAC inhibitor plus exemestane. While mTOR inhibitor plus exemestane was the best regimen (SUCRA value 89.5%), the mTOR inhibitor plus exemestane regimen induced more severe adverse events (SAEs) than the HDAC inhibitor plus exemestane regimen [OR, 95% CI: 2.40 (1.40-4.10)].

CONCLUSION

mTOR inhibitor and CDK4/6 inhibitor-based regimens demonstrated superior clinical efficacy and comparable safety profiles as second-line treatment in patients with HR-positive, HER2-negative advanced breast cancer.

Synergistic efficacy of PI3Kδ inhibitor with anti-PD-1 mAbs in immune-humanized PDX model of endocrine resistance hormone receptor-positive advanced breast cancer

Purpose

Endocrine resistance hormone receptor-positive (HR+) advanced breast cancer (ABC) is generally insensitive to immunecheckpoint inhibitors (ICIs). This study sought to determine whether PI3Kδ inhibitor could enhance the sensitivity of endocrine resistance HR + advanced BC to ICIs by reducing immune evasion.

Methods

Patient-derived HR + ABC xenografts were implanted into immune-humanized NSG mice and subsequently treated with YY20394 (PI3Kδ inhibitor) and camrelizumab. The mice were monitored for tumor progression, biochemical blood indicators, and peripheral blood T-cell subsets. The xenografted tumors were collected at the end of the treatment cycle and subjected to HE staining, immunohistochemistry and protein phosphorylation analysis. Besides, the xenografted tumors were also used to isolate primary breast cancer cells (BCCs) and regulatory T-cells (Tregs), which were subsequently used to evaluate drug sensitivity in vitro.

Results

The humanized PDX model showed a favorable initial treatment response to camrelizumab combined with YY20394 and manageable toxicity. YY20394 plus camrelizumab showed a strong inhibitory effect on HR + BC in vivo mediated by suppression of Treg activity and an increased proportion of CD8+ T cells. Mice bearing tumors treated with YY20394 and camrelizumab had less invasion, mitotic figures, and ki67 expression, while having higher IL-12 expression compared with other groups. Mechanistically, YY20394 only effectively inhibited the PI3K pathway and proliferation activity in Tregs but not in BCCs.

Conclusion

Our study suggests PI3Kδ inhibitor could the enhance the efficacy of ICIs in HR + BC PDX models by combating immune suppression and provides a feasible approach that may overcome the resistance of ICIs in HR + BC patients.

Phosphoinositide 3-Kinase (PI3K) Inhibitors and Breast Cancer: An Overview of Current Achievements

The phosphatidylinositol 3-kinase (PI3K) pathway is one of the most altered pathways in human cancers, and it plays a central role in cellular growth, survival, metabolism, and cellular mobility, making it a particularly interesting therapeutic target. Recently, pan-inhibitors and then selective p110α subunit inhibitors of PI3K were developed. Breast cancer is the most frequent cancer in women and, despite therapeutic progress in recent years, advanced breast cancers remain incurable and early breast cancers are at risk of relapse. Breast cancer is divided in three molecular subtypes, each with its own molecular biology. However, PI3K mutations are found in all breast cancer subtypes in three main "hotspots". In this review, we report the results of the most recent and main ongoing studies evaluating pan-PI3K inhibitors and selective PI3K inhibitors in each breast cancer subtype. In addition, we discuss the future of their development, the various potential mechanisms of resistance to these inhibitors and the ways to circumvent them.

A review on the role of cyclin dependent kinases in cancers

The Cyclin-dependent kinase (CDK) class of serine/threonine kinases has crucial roles in the regulation of cell cycle transition and is mainly involved in the pathogenesis of cancers. The expression of CDKs is controlled by a complex regulatory network comprised of genetic and epigenetic mechanisms, which are dysregulated during the progression of cancer. The abnormal activation of CDKs results in uncontrolled cancer cell proliferation and the induction of cancer stem cell characteristics. The levels of CDKs can be utilized to predict the prognosis and treatment response of cancer patients, and further understanding of the function and underlying mechanisms of CDKs in human tumors would pave the way for future cancer therapies that effectively target CDKs. Defects in the regulation of cell cycle and mutations in the genes coding cell-cycle regulatory proteins lead to unrestrained proliferation of cells leading to formation of tumors. A number of treatment modalities have been designed to combat dysregulation of cell cycle through affecting expression or activity of CDKs. However, effective application of these methods in the clinical settings requires recognition of the role of CDKs in the progression of each type of cancer, their partners, their interactions with signaling pathways and the effects of suppression of these kinases on malignant features. Thus, we designed this literature search to summarize these findings at cellular level, as well as in vivo and clinical levels.

CDK4/6 inhibitors versus PI3K/AKT/mTOR inhibitors in women with hormone receptor-positive, HER2-negative metastatic breast cancer: An updated systematic review and network meta-analysis of 28 randomized controlled trials

Background

Updated evidence was required to compare the efficacy and safety of cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) inhibitors for patients with hormone receptor-positive and HER2-negative metastatic breast cancer.

Methods

A systematic review and network meta-analysis was conducted utilizing data from randomized controlled trials (RCTs) that contained interventions of CDK4/6 inhibitors or PI3K/AKT/mTOR inhibitors. Progression-free survival (PFS), overall survival (OS), and treatment-related adverse events (TRAEs) were primary outcomes of interest. Pooled hazard ratios (HRs) and odds ratios (ORs) with 95% credible intervals (CrIs) were used to assess the survival outcomes and safety profiles, respectively.

Results

A total of 28 RCTs with 12,129 participants were included. Pooled analysis showed that CDK4/6 inhibitors significantly prolonged PFS than PI3K/AKT/mTOR inhibitors (HR, 0.81; 95% CrI, 0.69–0.94), whereas no significant differences were detected regarding OS. After balancing the treatment lines and metastatic sites, the superiority of CDK4/6 inhibitors only appeared in the visceral and non-visceral subgroups. Among CDK4/6 inhibitors, abemaciclib was significantly better than others in ≥3 grade neutropenia (OR, 0.04; 95% CrI, 0.01–0.15). The incidence of stomatitis and digestive disorders was different among diverse kinds of PI3K/AKT/mTOR inhibitors. Discrepancies appeared regarding TRAEs of hepatotoxicity, diarrhea, and hyperglycemia among different interventions.

Conclusions

CDK4/6 inhibitors showed better efficacy in PFS, but the benefits disappeared when taking treatment line into consideration. Specific and discrepant safety profiles were found in two categories of agents.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO, identifier CRD42022321172.

Treatment Strategy for Patients with HR-Positive HER2-Negative Metastatic Breast Cancer That Progressed on CDK4/6 Inhibitors

Background/Aims

The study aim was to evaluate if mTOR inhibitors can be considered as a treatment option for HR+ HER2- metastatic breast cancer (MBC) after progression on CDK4/6 inhibitors in clinical practice.

Methods

We retrospectively collected the clinicopathological data of patients with HR+ HER2- MBC treated with CDK4/6 inhibitors and subsequent therapies at our institution between 2014 and 2020. The patients were divided into 3 groups according to the type of subsequent treatment: (A) exemestane plus everolimus, (B) endocrine monotherapy, and (C) chemotherapy. Overall survival (OS) was estimated by using the Kaplan-Meier method and compared by using the log-rank test. The efficacy and adverse events (AEs) of each subsequent treatment were assessed by using Fisher's exact tests.

Results

Eighty-six patients (34 in group A, 20 in group B, 32 in group C) were included. The most common endocrine therapy in group B was fulvestrant (40%). The major chemotherapy regimen in group C was eribulin (25%). The median OS times after stopping CDK4/6 inhibitors were 34.5 months (95% confidence interval, 17.2 to NA), 13.6 months (3.9 to NA), and 19.5 months (18.8 to NA) in group A, group B, and group C, respectively. The only significant difference in OS was observed between group A and group B (20.9 months; p = 0.003). There was no difference in the incidence of grade 3 AEs between groups A and C or in the frequency of treatment discontinuation because of AEs among the 3 groups.

Conclusion

Our study shows that mTOR inhibitors might be an effective treatment option for patients with HR+ HER2- MBC previously treated with CDK4/6 inhibitors.

Protein tyrosine phosphatase receptor type Z1 inhibits the cisplatin resistance of ovarian cancer by regulating PI3K/AKT/mTOR signal pathway

Most patients with ovarian cancer (OC) get remission after undergoing cytoreductive surgery and platinum-based standard chemotherapy, but more than 50% of patients with advanced OC relapse within the first 5 years after treatment and develop resistance to standard chemotherapy. The production of medicinal properties is the main reason for the poor prognosis and high mortality of OC patients. Cisplatin (DDP) resistance is a major cause for poor prognosis of OC patients. PTPRZ1 can regulate the growth and apoptosis of ovarian cancer cells, while the molecular mechanism remains unknown. This study was designed to investigate the roles of PTPRZ1 in DDP-resistant OC cells and possible mechanism. PTPRZ1 expression in OC tissues and normal tissues was analyzed by GEPIA database and verified by Real-time Quantitative Reverse Transcription PCR (RT-PCR) assay. PTPRZ1 expression in normal ovarian cancer cells and DDP-resistant OC cells was also analyzed. Subsequently, RT-PCR, Western blot, MTT experiment and flow cytometry were used to assess the effects of PTPRZ1-PI3K/AKT/mTOR regulating axis on DDP resistance of OC. PTPRZ1 expression was abnormally low in OC tissues, and notably reduced in DDP-resistant OC cells. MTT experiment and flow cytometer indicated that overexpression of PTPRZ1 enhanced the DDP sensitivity of OC cells and promoted the cell apoptosis. Moreover, the results of our research showed that PTPRZ1 might exert its biological effects through blocking PI3K/AKT/mTOR pathway. PTPRZ1 overexpression inhibitied OC tumor growth and resistance to DDP in vivo. Overall, PTPRZ1 might suppress the DDP resistance of OC and induce the cytotoxicity by blocking PI3K/AKT/mTOR pathway.

Veliparib with carboplatin and paclitaxel in BRCA-mutated advanced breast cancer (BROCADE3): a randomised, double-blind, placebo-controlled, phase 3 trial

BACKGROUND

BRCA1 or BRCA2-mutated breast cancers are sensitive to poly(ADP-ribose) polymerase (PARP) inhibitors and platinum agents owing to deficiency in homologous recombination repair of DNA damage. In this trial, we compared veliparib versus placebo in combination with carboplatin and paclitaxel, and continued as monotherapy if carboplatin and paclitaxel were discontinued before progression, in patients with HER2-negative advanced breast cancer and a germline BRCA1 or BRCA2 mutation.

METHODS

BROCADE3 was a randomised, double-blind, placebo-controlled, phase 3 trial done at 147 hospitals in 36 countries. Eligible patients (aged ≥18 years) had deleterious germline BRCA1 or BRCA2 mutation-associated, histologically or cytologically confirmed advanced HER2-negative breast cancer, an Eastern Cooperative Oncology Group performance status of 0-2, and had received up to two previous lines of chemotherapy for metastatic disease. Patients were randomly assigned (2:1) by interactive response technology by means of permuted blocks within strata (block size of 3 or 6) to carboplatin (area under the concentration curve 6 mg/mL per min intravenously) on day 1 and paclitaxel (80 mg/m2 intravenously) on days 1, 8, and 15 of 21-day cycles combined with either veliparib (120 mg orally twice daily, on days -2 to 5) or matching placebo. If patients discontinued carboplatin and paclitaxel before progression, they could continue veliparib or placebo at an intensified dose (300 mg twice daily continuously, escalating to 400 mg twice daily if tolerated) until disease progression. Patients in the control group could receive open-label veliparib monotherapy after disease progression. Randomisation was stratified by previous platinum use, history of CNS metastases, and oestrogen and progesterone receptor status. The primary endpoint was investigator-assessed progression-free survival per Response Evaluation Criteria in Solid Tumors version 1.1. Efficacy analyses were done by intention to treat, which included all randomly assigned patients with a centrally confirmed BRCA mutation, and safety analyses included all patients who received at least one dose of velilparib or placebo. This study is ongoing and is registered with ClinicalTrials.gov, NCT02163694.

FINDINGS

Between July 30, 2014, and Jan 17, 2018, 2202 patients were screened, of whom 513 eligible patients were enrolled and randomly assigned. In the intention-to-treat population (n=509), 337 patients were assigned to receive veliparib plus carboplatin-paclitaxel (veliparib group) and 172 were assigned to receive placebo plus carboplatin-paclitaxel (control group). Median follow-up at data cutoff (April 5, 2019) was 35·7 months (IQR 24·9-43·6) in the veliparib group and 35·5 months (23·1-45·9) in the control group. Median progression-free survival was 14·5 months (95% CI 12·5-17·7) in the veliparib group versus 12·6 months (10·6-14·4) in the control group (hazard ratio 0·71 [95% CI 0·57-0·88], p=0·0016). The most common grade 3 or worse adverse events were neutropenia (272 [81%] of 336 patients in the veliparib group vs 143 [84%] of 171 patients in the control group), anaemia (142 [42%] vs 68 [40%]), and thrombocytopenia (134 [40%] vs 48 [28%]). Serious adverse events occurred in 115 (34%) patients in the veliparib group versus 49 (29%) patients in the control group. There were no study drug-related deaths.

INTERPRETATION

The addition of veliparib to a highly active platinum doublet, with continuation as monotherapy if the doublet were discontinued, resulted in significant and durable improvement in progression-free survival in patients with germline BRCA mutation-associated advanced breast cancer. These data indicate the utility of combining platinum and PARP inhibitors in this patient population.

FUNDING

AbbVie.