Addressing Residual Disease in HER2-Positive and Triple-Negative Breast Cancer: What Is Next?

PURPOSE OF REVIEW

To summarize the treatment strategies for patients with human epidermal growth factor receptor 2 (HER2)-positive disease and triple-negative breast cancer (TNBC) who have residual disease after preoperative systemic therapy.

RECENT FINDINGS

There has been a shift towards neoadjuvant systemic therapy for selected patients with HER2-positive and TNBC. Assessing the tumor's response to therapy provides prognostic information and allows individualization of the postoperative treatment for these patients based on the tumor response to neoadjuvant therapy. Patients with TNBC with residual disease after neoadjuvant therapy can be treated with pembrolizumab, capecitabine, or olaparib. Those with HER2-positive disease are treated with adjuvant trastuzumab emtansine. The treatment of early breast cancer has evolved significantly, and patient outcomes continue to improve. As better treatments are developed, we will need biomarkers to determine which patients may benefit from certain therapies to continue to improve outcomes by right-sizing treatments and limiting toxicities.

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 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.

A Phase I dose-escalation study of two cycles carboplatin-olaparib followed by olaparib monotherapy in patients with advanced cancer

Preclinical studies have shown synergistic effects when combining PARP1/2 inhibitors and platinum drugs in BRCA1/2 mutated cancer cell models. After a formulation change of olaparib from capsules to tablets, we initiated a dose finding study of olaparib tablets bidaily (BID) continuously with carboplatin to prepare comparative studies in this patient group. Patients were included in a 3 + 3 dose‐escalation schedule: olaparib 25 mg BID and carboplatin area under the curve (AUC) 3 mg*min/mL d1/d22, olaparib 25 mg BID and carboplatin AUC 4 mg*min/mL d1/d22, followed by increasing dose‐levels of olaparib from 50 mg BID, 75 mg BID, to 100 mg BID with carboplatin at AUC 4 mg*min/mL d1/d22. After two cycles, patients continued olaparib 300 mg BID as monotherapy. Primary objective was to assess the maximum tolerable dose (MTD). Twenty‐four patients with a confirmed diagnosis of advanced cancer were included. Most common adverse events were nausea (46%), fatigue (33%) and platelet count decrease (33%). Dose‐level 3 (olaparib 75 mg BID and carboplatin AUC 4 mg*min/mL; n = 6) was defined as MTD. Fourteen out of 24 patients (56%) had a partial response as best response (RECIST 1.1). Systemic exposure of the olaparib tablet formulation appeared comparable to the previous capsule formulation with olaparib tablet AUC_0‐12 of 16.3 μg/mL*h at MTD. Polymers of ADP‐ribose levels in peripheral blood mononuclear cells were reduced by 98.7% ± 0.14% at Day 8 compared to Day 1 for dose‐level 3. Olaparib tablets 75 mg BID and carboplatin AUC 4 mg*min/mL for two cycles preceding olaparib monotherapy 300 mg is a feasible and tolerable treatment schedule for patients with advanced cancer.

What's new?

Preclinical studies have shown synergistic effects when combining PARP1/2‐inhibitors and platinum drugs in BRCA1/2 mutated cancer cell models. This phase I trial of olaparib tablets combined with carboplatin in advanced cancer patients showed that the combination has an acceptable side‐effect profile. The maximum tolerable dose was olaparib tablets 75 mg BID and carboplatin AUC 4 mg*min/ml. The observed preliminary anti‐tumor activity was encouraging, with 58% of patients having a decrease in tumor volume of more than 30%. This study shows that the tablet formulation of olaparib can be administered safely in combination with carboplatin, compared to the previous capsule formulation.

Role of Poly (ADP-Ribose) Polymerase inhibitors beyond BReast CAncer Gene-mutated ovarian tumours: definition of homologous recombination deficiency?

PURPOSE OF REVIEW

PARP inhibitors have transformed the management of BRCA mutant (BRCA) high-grade serous and endometroid ovarian cancer (HGOC). However, it is clear that the benefit can be extended beyond this subgroup, particularly to those cancers with homologous recombination repair deficiency (HRD). We review emerging molecular and clinical data to support the use of PARP inhibitors in HRD HGOC and discuss the advantages and disadvantages of different HRD assays.

RECENT FINDINGS

Several phase 3 trials support the use of PARP inhibitor maintenance therapy beyond those patients with BRCA in the first-line and platinum-sensitive relapse setting. Many of these studies included HRD testing and it is clear, regardless of the assay used, that an incremental reduction in benefit is observed from BRCA tumours to HRD to homologous recombination proficient tumours. However, although currently available HRD assays predict the magnitude of benefit from PARP inhibitors, they consistently fail to identify a subgroup of patients who do not benefit.

SUMMARY

Clinical data support the use of PARP inhibitor maintenance therapy beyond BRCA patients. Current HRD tests lack negative predictive value and more research is required to develop a composite HRD assay that provides a dynamic readout of HRD status.

Phase I study of intermittent olaparib capsule or tablet dosing in combination with carboplatin and paclitaxel (part 2)

Background In the first part of this extensive phase I study (NCT00516724), continuous olaparib twice daily (bid) with carboplatin and/or paclitaxel resulted in myelosuppression and dose modifications. Here, we report the safety, tolerability, and efficacy of intermittent olaparib dosing combined with carboplatin and paclitaxel. Methods Patients with advanced solid tumors (part D) and enriched for ovarian and breast cancer (part E) received olaparib (capsule and tablet formulations) using intermittent schedules (2 to 10 days of a 21-day cycle) combined with carboplatin/paclitaxel. Safety assessments included evaluation of dose-limiting toxicities (DLTs; cycle 1 only), adverse events (AEs), and physical examinations. Pharmacokinetic assessments of olaparib capsule and tablet combined with carboplatin/paclitaxel were performed. Tumor responses (RECIST) were assessed every 2 cycles. Results In total, 132 heavily pre-treated patients were included. One DLT of grade 3 elevated alanine aminotransferase lasting for 8 days was reported (olaparib tablet 100 mg bid days 3-12, carboplatin area under the curve 4 and paclitaxel 175 mg/m²). The most common hematological AEs were neutropenia (47%) and thrombocytopenia (39%), which frequently led to dose modifications. Non-hematological AEs were predominantly grade 1-2, including alopecia (89%) and fatigue (84%). Overall objective response rate was 46%. Conclusions Discontinuous dosing of olaparib resulted in significant myelosuppression leading to dose interruptions and/or delays. Anti-tumor activity was encouraging in patients enriched with BRCA-mutated breast and ovarian cancer. The most appropriate olaparib tablet dose for use in further studies evaluating olaparib in combination with carboplatin and paclitaxel is 50 mg bid (days 1-5).

Phase 1 study of veliparib (ABT-888), a poly (ADP-ribose) polymerase inhibitor, with carboplatin and paclitaxel in advanced solid malignancies

PURPOSE

Veliparib is an oral inhibitor of poly (ADP-ribose) polymerase (PARP)-1 and -2. PARP-1 expression may be increased in cancer, and this increase confers resistance to cytotoxic agents. We aimed to determine the recommended phase 2 dose (RP2D), maximum tolerated dose (MTD), dose-limiting toxicity (DLT), and pharmacokinetics (PK) of veliparib combined with paclitaxel and carboplatin.

METHODS

Eligibility criteria included patients with advanced solid tumors treated with ≤ 3 prior regimens. Paclitaxel and carboplatin were administered on day 3 of a 21-day cycle. Veliparib was given PO BID days 1-7, except for cycle 1 in the first 46 patients to serve as control for toxicity and PK. A standard "3 + 3" design started veliparib at 10 mg BID, paclitaxel at 150 mg/m², and carboplatin AUC 6. The pharmacokinetic (PK) disposition of veliparib, paclitaxel, and carboplatin was determined by LC-MS/MS and AAS during cycles 1 and 2.

RESULTS

Seventy-three patients were enrolled. Toxicities were as expected with carboplatin/paclitaxel chemotherapy, including neutropenia, thrombocytopenia, and peripheral neuropathy. DLTs were seen in two of seven evaluable patients at the maximum administered dose (MAD): veliparib 120 mg BID, paclitaxel 200 mg/m², and carboplatin AUC 6 (febrile neutropenia, hyponatremia). The MTD and RP2D were determined to be veliparib 100 mg BID, paclitaxel 200 mg/m², and carboplatin AUC 6. Median number of cycles of the three-agent combination was 4 (1-16). We observed 22 partial and 5 complete responses. Veliparib did not affect paclitaxel or carboplatin PK disposition.

CONCLUSION

Veliparib, paclitaxel, and carboplatin were well tolerated and demonstrated promising antitumor activity.

Phase I/Ib study of olaparib and carboplatin in heavily pretreated recurrent high-grade serous ovarian cancer at low genetic risk

Purpose: To investigate maximum tolerated dose (MTD), activity and predictive biomarkers of olaparib with carboplatin in BRCA wild-type (BRCAwt) high grade serous ovarian carcinoma (HGSOC) patients. Methods: A 3+3 dose escalation study examined olaparib capsules (400 mg twice daily [BID], days 1-7) with carboplatin (AUC3-5 on day 1) every 21 days for 8 cycles, followed by olaparib 400 mg BID maintenance. Blood and tumor biopsy samples were collected pre- and on-treatment in the expansion cohort for PAR levels and proteomic endpoints. Results: 30 patients (median 7 prior regimens [2-12], 63% (19/30) platinum-resistant) were enrolled. Dose-limiting toxicity was thrombocytopenia/neutropenia, and infection with carboplatin AUC5 (2/6 patients). MTD was olaparib 400 mg BID + carboplatin AUC4. Grade 3/4 adverse events (>10%) included neutropenia (23%), thrombocytopenia (20%), and anemia (13%). Five of 25 (20%) evaluable patients had partial response (PR; median 4.5 months [3.3-9.5]). Clinical benefit rate (PR + stable disease ≥4 months) was 64% (16/25). A greater decrease in tissue PAR levels was seen in the clinical benefit group versus no benefit (median normalized linear change -1.84 [-3.39- -0.28] vs 0.51 [-0.27- 1.29], p = 0.001) and a DNA repair score by proteomics did not correlate with response. Conclusions: The olaparib and carboplatin combination is tolerable and has clinical benefit in subsets of heavily pretreated BRCAwt HGSOC, independent of platinum sensitivity.

Olaparib for the treatment of breast cancer

INTRODUCTION

Mutations in BRCA1 and BRCA2 genes account for around 2-3% of breast cancer events and more than 10% of triple negative breast cancers. Olaparib (Lynparza®), an orally administered PARP inhibitor, demonstrated clinical benefit in a phase III trial for mutated BRCA-positive HER2 negative metastatic breast cancer. Areas covered: This review gives an overview of available preclinical and clinical data regarding olaparib, including its chemistry, mechanism of action, pharmacokinetics and pharmacodynamics, and evidence supporting antitumor efficacy and safety profile in breast cancer patients. Expert commentary: Olaparib improves progression-free survival in germline BRCA mutated HER2 negative metastatic breast cancer patients as compared to standard chemotherapy, with a manageable toxicity profile. Efficacy is of clinical relevance especially in the context of triple negative breast cancer. However, several aspects, such as sequencing or combination of these agents with other anticancer agents and identification of appropriate biomarkers, still need to be clearly defined.

Olaparib in combination with paclitaxel in patients with advanced gastric cancer who have progressed following first-line therapy (GOLD): a double-blind, randomised, placebo-controlled, phase 3 trial

BACKGROUND

Olaparib combined with paclitaxel has previously shown a significant improvement in overall survival versus placebo plus paclitaxel as second-line therapy in a phase 2 study in Asian patients with advanced gastric cancer, especially in those with ataxia-telangiectasia mutated protein (ATM)-negative tumours. Here, we report the primary efficacy and safety analyses from a subsequent phase 3 trial.

METHODS

This double-blind, randomised, placebo-controlled, phase 3 study (GOLD) recruited Asian patients aged 18 years or older (≥20 years if Japanese) with advanced gastric cancer that had progressed following, or during, first-line chemotherapy. Patients were randomly assigned (1:1) to receive oral olaparib (100 mg twice daily) plus paclitaxel (80 mg/m² intravenously) or matching placebo plus paclitaxel. Randomisation was done through an interactive voice response system and no stratification factors were used. Patients and investigators were masked to treatment allocation. Two co-primary populations were assessed: the overall population of all patients and patients whose tumours were ATM-negative (identified after randomisation, before the data cutoff date, March 28, 2016). The primary endpoint in both populations was overall survival (defined as the time from the date of randomisation until death from any cause before data cutoff); a significant difference was defined as p<0·025. Efficacy was assessed in the intention-to-treat populations and safety in patients who received at least one dose of treatment. This trial is registered with ClinicalTrials.gov, number NCT01924533 (study ID, D081BC00004), and is ongoing but no longer recruiting participants.

FINDINGS

Between Sept 3, 2013, and March 28, 2016, 643 patients were enrolled from 58 study sites in hospitals and medical centres in China, Japan, South Korea, and Taiwan. 525 eligible patients were randomly assigned: 263 to receive olaparib plus paclitaxel and 262 to receive placebo plus paclitaxel. 94 patients were determined to have ATM-negative tumours before unmasking for the primary analysis (48 in the olaparib plus paclitaxel group and 46 in the placebo plus paclitaxel group). Overall survival did not differ between treatment groups in the overall patient population (median overall survival 8·8 months [95% CI 7·4-9·6] in the olaparib group vs 6·9 months [6·3-7·9] in the placebo group; HR 0·79 [97·5% CI 0·63-1·00]; p=0·026) or in the ATM-negative population (12·0 months [7·8-18·1] vs 10·0 months [6·4-13·3]; 0·73 [0·40-1·34]; p=0·25). In the overall patient population, the most common grade 3 or worse adverse events in the olaparib plus paclitaxel group were neutropenia (78 [30%] of 262 patients), leucopenia (42 [16%]), and decreased neutrophil count (40 [15%]); in the placebo plus paclitaxel group, they were neutropenia (59 [23%] of 259 patients), leucopenia (27 [10%]), and decreased white blood cell count (21 [8%]). Adverse events with an outcome of death causally related to study treatment (according to investigator assessment) were reported in two patients: liver injury in one patient (<1%) in the olaparib plus paclitaxel group and cardiac failure in one patient (<1%) in the placebo plus paclitaxel group.

INTERPRETATION

The GOLD study did not meet its primary objective of showing a significant improvement in overall survival with olaparib in the overall or ATM-negative population of Asian patients with advanced gastric cancer. The study generated informative efficacy and safety data regarding the use of olaparib in combination with a chemotherapeutic agent and provides a foundation for future studies in this difficult-to-treat patient population.

FUNDING

AstraZeneca.

Randomized, Placebo-Controlled, Phase II Study of Veliparib in Combination with Carboplatin and Paclitaxel for Advanced/Metastatic Non-Small Cell Lung Cancer

Purpose: PARP plays an important role in DNA repair. Veliparib, a PARP inhibitor, enhances the efficacy of platinum compounds and has been safely combined with carboplatin and paclitaxel. The primary endpoint of this phase II trial determined whether addition of veliparib to carboplatin and paclitaxel improved progression-free survival (PFS) in previously untreated patients with advanced/metastatic non-small cell lung cancer.Experimental Design: Patients were randomized 2:1 to carboplatin and paclitaxel with either veliparib or placebo. Veliparib (120 mg) or placebo was given on days 1 to 7 of each 3-week cycle, with carboplatin (AUC = 6 mg/mL/min) and paclitaxel (200 mg/m²) administered on day 3, for a maximum of 6 cycles.Results: Overall, 158 were included (median age, 63 years; male 68%, squamous histology 48%). Median PFS was 5.8 months in the veliparib group versus 4.2 months in the placebo group [HR, 0.72; 95% confidence interval (CI), 0.45-1.15; P = 0.17)]. Median overall survival (OS) was 11.7 and 9.1 months in the veliparib and placebo groups, respectively (HR, 0.80; 95% CI, 0.54-1.18; P = 0.27). In patients with squamous histology, median PFS (HR, 0.54; 95% CI, 0.26-1.12; P = 0.098) and OS (HR, 0.73; 95% CI, 0.43-1.24; P = 0.24) favored veliparib treatment. Objective response rate was similar between groups (veliparib: 32.4%; placebo: 32.1%), but duration of response favored veliparib treatment (HR, 0.47; 95% CI, 0.16-1.42; P = 0.18). Grade III/IV neutropenia, thrombocytopenia, and anemia were comparable between groups.Conclusions: Veliparib combination with carboplatin and paclitaxel was well-tolerated and demonstrated a favorable trend in PFS and OS versus chemotherapy alone. Patients with squamous histology had the best outcomes with veliparib combination. Clin Cancer Res; 23(8); 1937-44. ©2016 AACR.

Clinical Application of Poly(ADP-Ribose) Polymerase Inhibitors in High-Grade Serous Ovarian Cancer

: High-grade serous ovarian cancer is characterized by genomic instability, with one half of all tumors displaying defects in the important DNA repair pathway of homologous recombination. Given the action of poly(ADP-ribose) polymerase (PARP) inhibitors in targeting tumors with deficiencies in this repair pathway by loss of BRCA1/2, ovarian tumors could be an attractive population for clinical application of this therapy. PARP inhibitors have moved into clinical practice in the past few years, with approval from the Food and Drug Administration (FDA) and European Medicines Agency (EMA) within the past 2 years. The U.S. FDA approval of olaparib applies to fourth line treatment in germline BRCA-mutant ovarian cancer, and European EMA approval to olaparib maintenance in both germline and somatic BRCA-mutant platinum-sensitive ovarian cancer. In order to widen the ovarian cancer patient population that would benefit from PARP inhibitors, predictive biomarkers based on a clear understanding of the mechanism of action are required. Additionally, a better understanding of the toxicity profile is needed if PARP inhibitors are to be used in the curative, rather than the palliative, setting. We reviewed the development of PARP inhibitors in phase I-III clinical trials, including combination trials of PARP inhibitors and chemotherapy/antiangiogenics, the approval for these agents, the mechanisms of resistance, and the outstanding issues, including the development of biomarkers and the rate of long-term hematologic toxicities with these agents.

IMPLICATIONS FOR PRACTICE

The poly(ADP-ribose) polymerase (PARP) inhibitor olaparib has recently received approval from the Food and Drug Administration (FDA) and European Medicines Agency (EMA), with a second agent (rucaparib) likely to be approved in the near future. However, the patient population with potential benefit from PARP inhibitors is likely wider than that of germline BRCA mutation-associated disease, and biomarkers are in development to enable the selection of patients with the potential for clinical benefit from these agents. Questions remain regarding the toxicities of PARP inhibitors, limiting the use of these agents in the prophylactic or adjuvant setting until more information is available. The indications for olaparib as indicated by the FDA and EMA are reviewed.

Advances in small-molecule drug discovery for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a subtype of poor prognosis, highly invasive and difficult-to-treat breast cancers accounting for approximately 15% of clinical cases. Given the poor outlook and lack of sustained response to conventional therapies, TNBC has been the subject of intense studies on new therapeutic approaches in recent years. The development of targeted cancer therapies, often in combination with established chemotherapy, has been applied to a number of new clinical studies in this setting in recent years. This review will highlight recent therapeutic advances in TNBC, focusing on small-molecule drugs and their associated biological mechanisms of action, and offering the possibility of improved prospects for this patient group in the near future.

Long-term safety and anti-tumour activity of olaparib monotherapy after combination with carboplatin and paclitaxel in patients with advanced breast, ovarian or fallopian tube cancer

BACKGROUND

Olaparib (AZD2281), a PARP-1/2 inhibitor, has been extensively investigated in clinical trials. However, limited clinical data are available about its long-term safety and anti-tumour activity.

METHODS

Patients had first participated in a phase I study of olaparib combined with carboplatin and/or paclitaxel. They continued with olaparib monotherapy in their best interest if they failed to tolerate the combination due to the treatment-related adverse events (TRAEs). Safety data were collected by physical examination and regular laboratory evaluations. Disease evaluations were performed by CT scan.

RESULTS

At data cutoff, 21 patients were included; 10 with breast, 9 with ovarian and 2 with fallopian tube cancer of whom 16 patients had a BRCA mutation (13 BRCA1; 3 BRCA2). TRAEs were mostly haematological and most prominent shortly after switching from combination to monotherapy, probably due to carry-over effects of chemotherapy. Over time, both severity and frequency of TRAEs decreased. Responses to olaparib were durable with a median treatment duration of 52 (range 7-183) weeks. In total, nine (43%) patients were still on study at data cutoff.

CONCLUSION

Continued long-term daily olaparib was found to be safe and tolerable. Encouragingly, patients who showed a favourable response on earlier combination therapy maintained this response on olaparib monotherapy.

PARP inhibitors in ovarian cancer: current status and future promise

Clinical investigation of poly(ADP-ribose) polymerase (PARP) inhibitors for ovarian cancer treatment has rapidly evolved from observations of single-agent in vitro activity of these agents in BRCA-deficient cancer cells in 2005 to the initiation of multiple phase III studies in 2013. With clinical trial design and treatment of ovarian cancer increasingly based on histological and molecular characteristics, PARP inhibitors are on the horizon of becoming the first biologic agents to be used to treat ovarian cancer based upon pre-selection characteristics of the patient's cancer. PARP inhibitors are most active in ovarian cancers that have defects or aberrations in DNA repair; use of these agents has been of particular interest in high grade serous cancers (HGSC), where studies have shown that ~50% of HGSC have abnormalities of DNA repair through BRCA germline and somatic mutation, post-translational changes of BRCA, and abnormalities of other DNA repair molecules. In addition, as aberrant DNA pathways in other histological subtypes of ovarian cancer are identified, and through the combination of PARP inhibitors with other biologic agents, the pool of eligible patients who may benefit from PARP inhibitors will likely expand. Pending review by the Food and Drug Administration (FDA) and the outcome of confirmatory phase III studies, PARP inhibitors could become the first FDA-approved biologic agent for ovarian cancer and also the first new FDA-approval in ovarian cancer since carboplatin and gemcitabine were approved for platinum sensitive ovarian cancer in 2006. This review discusses the PARP inhibitors that are currently in testing for ovarian cancer treatment and the future of this class of anti-cancer agents.