Phase I study of safety and pharmacokinetics of the anti-MUC16 antibody-drug conjugate DMUC5754A in patients with platinum-resistant ovarian cancer or unresectable pancreatic cancer

BACKGROUND

MUC16 is a tumor-specific antigen overexpressed in ovarian (OC) and pancreatic (PC) cancers. The antibody-drug conjugate (ADC), DMUC5754A, contains the humanized anti-MUC16 monoclonal antibody conjugated to the microtubule-disrupting agent, monomethyl auristatin E (MMAE).

PATIENTS AND METHODS

This phase I study evaluated safety, pharmacokinetics (PK), and pharmacodynamics of DMUC5754A given every 3 weeks (Q3W, 0.3-3.2 mg/kg) or weekly (Q1W, 0.8-1.6 mg/kg) to patients with advanced recurrent platinum-resistant OC or unresectable PC. Biomarker studies were also undertaken.

RESULTS

Patients (66 OC, 11 PC) were treated with DMUC5754A (54 Q3W, 23 Q1W). Common related adverse events (AEs) in >20% of patients (all grades) over all dose levels were fatigue, peripheral neuropathy, nausea, decreased appetite, vomiting, diarrhea, alopecia, and pyrexia in Q3W patents, and nausea, vomiting, anemia, fatigue, neutropenia, alopecia, decreased appetite, diarrhea, and hypomagnesemia in Q1W patients. Grade ≥3-related AE in ≥5% of patients included neutropenia (9%) and fatigue (7%) in Q3W patients, and neutropenia (17%), diarrhea (9%), and hyponatremia (9%) in Q1W patients. Plasma antibody-conjugated MMAE (acMMAE) and serum total antibody exhibited non-linear PK across tested doses. Minimal accumulation of acMMAE, total antibody, or unconjugated MMAE was observed. Confirmed responses (1 CR, 6 PRs) occurred in OC patients whose tumors were MUC16-positive by IHC (2+ or 3+). Two OC patients had unconfirmed PRs; six OC patients had stable disease lasting >6 months. For CA125, a cut-off of ≥70% reduction was more suitable for monitoring treatment response due to the binding and clearance of serum CA125 by MUC16 ADC. We identified circulating HE4 as a potential novel surrogate biomarker for monitoring treatment response of MUC16 ADC and other anti-MUC16 therapies in OC.

CONCLUSIONS

DMUC5754A has an acceptable safety profile and evidence of anti-tumor activity in patients with MUC16-expressing tumors. Objective responses were only observed in MUC16-high patients, although prospective validation is required.

CLINICAL TRIAL NUMBER

NCT01335958.

Use and Effectiveness of Neoadjuvant Chemotherapy for Treatment of Ovarian Cancer

Purpose In 2010, a randomized clinical trial demonstrated noninferior survival for patients with advanced ovarian cancer who were treated with neoadjuvant chemotherapy (NACT) compared with primary cytoreductive surgery (PCS). We examined the use and effectiveness of NACT in clinical practice. Patients and Methods A multi-institutional observational study of 1,538 women with stages IIIC to IV ovarian cancer who were treated at six National Cancer Institute-designated cancer centers. We examined NACT use in patients who were diagnosed between 2003 and 2012 (N = 1,538) and compared overall survival (OS), morbidity, and postoperative residual disease in a propensity-score matched sample of patients (N = 594). Results NACT use increased from 16% during 2003 to 2010 to 34% during 2011 to 2012 in stage IIIC disease ( P_trend < .001), and from 41% to 62% in stage IV disease ( P_trend < .001). Adoption of NACT varied by institution, from 8% to 30% for stage IIIC disease (P < .001) and from 27% to 61% ( P = .007) for stage IV disease during this time period. In the matched sample, NACT was associated with shorter OS in stage IIIC disease (median OS: 33 v 43 months; hazard ratio [HR], 1.40; 95% CI, 1.11 to 1.77) compared with PCS, but not stage IV disease (median OS: 31 v 36 months; HR, 1.16; 95% CI, 0.89 to 1.52). Patients with stages IIIC and IV disease who received NACT were less likely to have ≥ 1 cm postoperative residual disease, an intensive care unit admission, or a rehospitalization (all P ≤ .04) compared with those who received PCS treatment. However, among women with stage IIIC disease who achieved microscopic or ≤ 1 cm postoperative residual disease, NACT was associated with decreased OS (HR, 1.49; 95% CI, 1.01 to 2.18; P = .04). Conclusion Use of NACT increased significantly between 2003 and 2012. In this observational study, PCS was associated with increased survival in stage IIIC, but not stage IV disease. Future studies should prospectively consider the efficacy of NACT by extent of residual disease in unselected patients.

Characterization of folate receptor alpha (FRα) expression in archival tumor and biopsy samples from relapsed epithelial ovarian cancer patients: A phase I expansion study of the FRα-targeting antibody-drug conjugate mirvetuximab soravtansine

PURPOSE

To characterize folate receptor alpha (FRα) expression in archival and fresh biopsy tumor samples from relapsed ovarian cancer patients.

METHODS

Patients with ovarian tumors amenable to biopsy were eligible to enroll. Eligibility included a minimum requirement of FRα positivity in archival tumor samples (≥25% of cells with ≥2+ staining intensity). Patients received mirvetuximab soravtansine at 6mg/kg once every 3weeks. Core needle biopsies were collected before and after treatment and FRα levels assessed by immunohistochemistry. Descriptive statistics were used to summarize the association between receptor expression and response.

RESULTS

Twenty-seven heavily pre-treated patients were enrolled. Six individuals (22%) did not have evaluable pre-treatment biopsies due to insufficient tumor cells. The concordance of FRα expression in archival and biopsy tissues was 71%, and no major shifts in receptor expression were seen in matched pre- and post-treatment biopsy samples. Adverse events were generally mild (≤grade 2) with keratopathy (48%), fatigue (44%), diarrhea, and blurred vision (each 37%) being the most common treatment-related toxicities. The confirmed objective response rate (ORR) was 22%, including two complete responses and four partial responses. Superior efficacy measures were observed in the subset of patients with the highest FRα levels (ORR, 31%; progression-free survival, 5.4months).

CONCLUSION

Concordance of FRα expression in biopsy versus archival tumor samples suggests that archival tissue can reliably identify patients with receptor-positive tumors and is appropriate for patient selection in mirvetuximab soravtansine clinical trials. Regardless of the tissue source analyzed, higher FRα expression was associated with greater antitumor activity.

Abstract 4033: Combined MEK and BCL-2/XL inhibition as a potential drug combination for the treatment of high-grade serous ovarian cancer

High-grade serous ovarian cancer (HGSOC) accounts for 70-80% of ovarian cancer deaths. Despite an initial response to platinum-based chemotherapy, treatment resistance eventually occurs in most patients. The overall aim of our studies is to identify synergistic drug combinations for the treatment of HGSOC and biomarkers that predict sensitivity for future translation in clinical trials. In particular, this study focuses on the vulnerabilities of patient-derived ovarian cancer cells to combined inhibition of the MEK pathway and the anti-apoptotic proteins BCL-2 and BCL-XL.

The Ras/MAPK pathway is activated in a subset of HGSOC by gene copy alterations. However, MEK inhibitors have not been evaluated in HGSOC. In this study, we used a collection of 14 primary samples derived from ascites cells of platinum-resistant HGSOC patients (Liu JF et al. 2016). We investigated the sensitivity of these tumor cells to the MEK inhibitor cobimetinib (GDC-0973). Treatment with GDC-0973 had no effects on cell viability in vitro in any of the patient-derived models. To investigate the response to MEK inhibition, we performed Reverse Phase Protein Array of the tumor cells treated with 0.3μM of GDC-0973 in vitro. We found that MEK inhibition by GDC-0973 reduced cell cycle progression markers and upregulated the pro-apoptotic protein BIM. Since more than half of the models express high levels of anti-apoptotic BCL-2 family proteins which neutralize BIM, we examined the effects of antagonism of BCL-2 pro-survival proteins in combination with GDC-0973. Treatment with a combination of GDC-0973 and the BCL-2/XL antagonist, navitoclax (ABT-263) significantly reduced cell number and increased cell death in 10 out of 14 patient-derived models. Protein levels of BIM following treatment with GDC-0973 correlated with sensitivity to the drug combination (R2=0.8 p&lt;0.0001). Interestingly, the BIM levels after MEK inhibition correlate with BIM protein levels before the treatment, suggesting that baseline BIM levels could be used as biomarker of sensitivity. Levels of the pro-survival protein MCL-1 also played a critical role in patient-derived cells that were resistant to the drug combination. Indeed, treatment with a specific MCL-1 inhibitor, A-1210477, in combination with GDC-0973 and ABT-263 led to dramatic tumor cell killing in vitro compared to dual combination of GDC-0973 and ABT-263.

Finally, we tested the combination of GDC-0973 and ABT-263 in vivo and preliminary results indicate that the drug combination is well tolerated and is able to significantly reduce tumor growth in patient-derived xenograft models (n=4).

Our studies provide significant evidence that combined inhibition of MEK and BCL-2/XL may be an effective drug combination for treatment of HGSOC and that the pro-apoptotic protein BIM may serve as a predictive biomarker to stratify patients that can benefit from these targeted therapies

Citation Format: Claudia Iavarone, Ioannis Zervantonakis, Laura M. Selfors, Sangeetha Palakurthi, Joyce F. Liu, Ursula A. Matulonis, Ronny I. Drapkin, Gordon B. Mills, Joel D. Leverson, Deepak Sampath, Joan S. Brugge. Combined MEK and BCL-2/XL inhibition as a potential drug combination for the treatment of high-grade serous ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4033. doi:10.1158/1538-7445.AM2017-4033

Abstract CT008: Phase I study of the alpha specific PI3-Kinase inhibitor BYL719 and the poly (ADP-Ribose) polymerase (PARP) inhibitor olaparib in recurrent ovarian and breast cancer: Analysis of the dose escalation and ovarian cancer expansion cohort

Background: In vivo synergy with concurrent PI3-Kinase inhibition and PARP inhibition has been observed in BRCA-deficient and BRCA-proficient preclinical models of triple negative breast cancer (TNBC) and ovarian cancer (OC). A phase I trial of the oral pan-class I PI3-Kinase inhibitor BKM120 and the PARP inhibitor olaparib demonstrated anti-cancer activity in TNBC and OC, both in patients with and without germline BRCA1 and BRCA2 (BRCA) mutations. However, CNS toxicity (depression) and liver function test abnormalities limited dose escalation of BKM120 prompting evaluation of the alpha specific PI3-Kinase inhibitor BYL719 (which has no CNS toxicity) in combination with olaparib.

Methods: Olaparib was administered twice daily (tablet formulation) and BYL719 daily on a 28-day cycle, both orally. A 3 + 3 dose-escalation design was employed with primary objectives of defining the maximum tolerated dose (MTD) and recommended phase 2 dose of the combination of BYL719 and olaparib, and secondary objectives of defining toxicity, activity, and pharmacokinetic profiles of both agents. Eligibility included recurrent TNBC or high grade serous (HGS) OC, or any histology OC or breast cancer (BC) with presence of a known germline BRCA mutation, performance status of 0-1 and measurable/evaluable cancer. Patients with platinum sensitive or resistant or refractory OC were eligible and prior PARP inhibitor use was allowed. Dose-expansion cohorts at the MTD were enrolled for both BC and OC.

Results: 46 patients (16 BC and 30 OC) have been enrolled in the study; 28 patients participated in the dose escalation portion of the study (4 BC and 24 OC). Two patients with OC did not receive study drugs because of ineligibility. MTD was defined as BYL719 200mg once daily and olaparib 200mg twice daily. Dose limiting toxicities included hyperglycemia, rash and fever with decreased neutrophil count. Four patients (3 OC and 1 BC) discontinued protocol therapy because of toxicity (2 for hyperglycemia, 1 for nausea and 1 for allergic reaction). Most common toxicities included nausea, hyperglycemia, fatigue, diarrhea and vomiting. At the MTD, 6 patients with OC and 12 patients with BC were enrolled into a dose expansion cohort. The OC expansion cohort has completed enrollment, while the BC cohort is still enrolling. Among patients with OC who received study drugs (28 patients, 26 (93%) with platinum resistant disease), objective response rate (ORR) by RECIST 1.1 was 36% (10/28 patients, all partial responses (PRs)). Median duration of response was 167 days (range 16-398 days); 5 of 10 patients with PR remain on treatment. ORR was 33% for patients with germline BRCA mutations and 31% for patients without germline BRCA mutations. Among patients without germline BRCA mutations with platinum resistant OC, ORR was 29%.

Conclusions: Combined BYL719 and olaparib is feasible, and similar clinical benefit was observed in patients with and without germline BRCA mutations. The activity of this combination in OC patients without germline BRCA mutations and with platinum resistant disease was higher than expected from olaparib monotherapy and warrants further investigation. This work was funded in part by the Stand Up To Cancer Ovarian Dream Team. Clinical trial: NCT01623349.

Citation Format: Panagiotis A. Konstantinopoulos, William T. Barry, Michael Birrer, Shannon N. Westin, Sarah Farooq, Karen Cadoo, Christin Whalen, Weixiu Luo, Hui Liu, Carol Aghajanian, David B. Solit, Gordon B. Mills, Barry S. Taylor, Helen Won, Michael F. Berger, Sangeetha Palakurthi, Joyce F. Liu, Lew Cantley, Scott H. Kaufmann, Elizabeth M. Swisher, Alan D. D'Andrea, Eric Winer, Gerburg M. Wulf, Ursula A. Matulonis. Phase I study of the alpha specific PI3-Kinase inhibitor BYL719 and the poly (ADP-Ribose) polymerase (PARP) inhibitor olaparib in recurrent ovarian and breast cancer: Analysis of the dose escalation and ovarian cancer expansion cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT008. doi:10.1158/1538-7445.AM2017-CT008

Abstract CT142: A single arm, single stage phase II trial of trametinib (GSK1120212) and GSK2141795 in persistent or recurrent cervical cancer

Introduction: In the US, invasive cervical cancer (CC) will affect 12,710 women/year with approximately 4,290 deaths. While screening has reduced cases in the developed world, CC remains a leading cause of cancer death globally with 275,000 women dying of CC/year. Though treatment options for recurrent/metastatic (met) CC have improved by adding bevacizumab to platinum-based chemotherapy, patients with met CC will eventually have cancer progression and therapies are few. PIK3CA and KRAS mutations are found in both adenocarcinomas and squamous cell cancers of the cervix. Thus, therapies targeting the PI3K/AKT and RAS-ERK pathways have rationale for treating metastatic CC; pre-clinical studies support dual PI3K inhibition and MEK inhibition given pathway redundancy and negative feedback loops. This phase II study tested a MEK and an AKT inhibitor combination.

Study Design: Trametinib (GSK1120212) is a reversible/selective inhibitor of MEK1 and MEK2. GSK2141795 is an AKT1-3 inhibitor. Objectives included RECIST 1.1 activity of trametinib and GSK2141795 in pts with recurrent CC (primary objective). Other objectives included toxicities and duration of response. Translational objectives included description of mutation and co-mutation rates of PI3K and RAS-ERK signaling pathway genes using hybrid-capture and massively parallel sequencing assay at Dana-Farber Cancer Institute. Eligibility: recurrent or met CC (any histology), receipt of 1 prior chemotherapy, and up to 1 additional regimen, no prior use of PI3K or RAS-ERK pathway inhibitor, ECOG PS 0-2, normal organ function, and availability of FFPE tissue. The treatment regimen was: trametinib 1.5 mg and GSK2141795 50 mg, both given PO daily; cycle length: 28 days. RR was assessed every 2 cycles. This study (NCT01958112) was approved and funded in part by the National Comprehensive Cancer Network (NCCN) Oncology Research Program from general research support provided by Novartis Pharmaceuticals Corporation.

Results: 16 pts were enrolled and 14 received study drug. The study was closed prior to accrual completion because of Novartis’ decision to stop 1) developing this combination because of lack of activity across several cancer types and observed toxicities and 2) manufacturing GSK2141795. Of the 14 patients who received study drug, one patient had a partial response lasting 108 days, 8 had stable disease, 3 had progression at their first evaluation and 2 pts were unevaluable. Related serious adverse events included a thromboembolic event (grade 3), acneiform rash (grade 3), retinal detachment (grade 2), and hypophosphatemia (grade 3). There were no grade 4 or 5 drug related toxicities.

Conclusions: This combination of an AKT and MEK inhibitor was tolerated by patients. Anti-cancer activity was minimal in the enrolled patients, but the study was terminated early due to discontinuation of the AKT inhibitor GSK2141795.

Citation Format: Ursula A. Matulonis, Alexi Wright, Susana Campos, Panagiotis Konstantinopoulos, Ariana Peralta, Kimberley MacNeill, Stephanie Morrissey, Christin Whalen, Joyce Liu. A single arm, single stage phase II trial of trametinib (GSK1120212) and GSK2141795 in persistent or recurrent cervical cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT142. doi:10.1158/1538-7445.AM2017-CT142

Abstract NTOC-112: GENOMIC SCARS AND CLINICAL RESPONSE TO COMBINATION THERAPY OF PARP AND ANGIOGENESIS INHIBITORS IN OVARIAN CANCER

BACKGROUND: Genomic instability, frequently resulting in chromosomal allelic deletion with allelic imbalance (AI)/loss of heterozygosity (LOH), is characteristic of high-grade serous ovarian cancer (HGSOC). Frequent allelic deletion is thought to arise from deficiency in DNA repair by homologous recombination (HR) resulting in the so called “genomic scars” of HR deficiency. Quantification of AI/LOH events in the tumor genome has previously been shown to predict response to therapy using platinum compounds. Recently, PARP inhibitors have proved useful in treating a sub-set of patients with HGSOC, particularly tumors harboring BRCA1/2 mutations. Combination with an angiogenesis inhibitor significantly improved the outcome. This study explores the potential of using AI/LOH scores to predict clinical response of HGSOC to PARP inhibition alone or in combination with an angiogenesis inhibitor.

MATERIALS AND METHODS: Molecular inversion probe array data were generated using tumors from a sub-set of patients (n=37) enrolled in a clinical trial comparing the PARP inhibitor Olaparib to the combination of Olaparib with the anti-angiogenic agent Cediranib (NCT01116648). AI/LOH regions were identified using an ASCAT based algorithm. Markers of genomic instability associated with DNA repair deficiency were scored. These quantify AI regions (NAI), telomeric AI (NtAI), large scale transition (LST), fraction of LOH (FLOH), and HRD-LOH. dChip was used for copy number analysis. The best overall response to therapy was determined using the RECIST 1.1 criteria for complete and partial response (CR, n = 3 and PR, n = 18), and stable disease without objective response (SD, n = 16).

RESULTS: A high tumor NAI-score was positively correlated with the degree of clinical response to therapy (either olaparib alone or in combination with cediranib) (Chi-square test for trend, p = 0.036). This association remains statistically significant in the subgroup carrying BRCA mutations (n = 22, Chi-square test for trend, p = 0.0488). In this limited sample, the objective response rate of high NAI tumors to the combination therapy was high (7 out of 8), especially in patient carrying wild-type BRCA1/2 genes (2 out of 2, p = 0.045). The results suggest NAI may be a potential genomic marker for response to the therapy combining PARP and angiogenesis inhibitors. However, no significant association was observed between the degree of objective response and scores of other genomic measurements NtAI, LST, or HRD-LOH.

SUMMARY: High NAI-score was associated with objective response to olaparib, alone or in combination with cediranib, supporting NAI as a candidate of genomic marker for predicting response to PARP inhibitor-based therapy in HGSOC. A larger cohort would be required to further evaluate predictive value of NAI for response to the combinational therapy.

Citation Format: Zhigang C. Wang, Nicolai Juul Birkbak, William T. Barry, Thomas M. Roberts, Eric P. Winer, J Dirk Iglehart, Ursula A. Matulonis, S. Percy Ivy, and Joyce F. Liu. GENOMIC SCARS AND CLINICAL RESPONSE TO COMBINATION THERAPY OF PARP AND ANGIOGENESIS INHIBITORS IN OVARIAN CANCER [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr NTOC-112.

Mirvetuximab soravtansine (IMGN853), a folate receptor alpha (FRα)-targeting antibody-drug conjugate (ADC), in platinum-resistant epithelial ovarian cancer (EOC) patients (pts): Activity and safety analyses in phase I pooled expansion cohorts

5547

Background: The early clinical evaluation of mirvetuximab soravtansine (IMGN853), an ADC that comprises a FRα-binding antibody linked to the tubulin-disrupting maytansinoid DM4, has revealed encouraging signs of activity in pts with ovarian cancer. A pooled analysis of safety and efficacy was performed including individuals with platinum-resistant EOC, enrolled across three expansion cohorts of an ongoing phase I trial (NCT01609556), who met the eligibility criteria for the pivotal phase III study of IMGN853 (FORWARD I; NCT02631876). Methods: Pts were administered IMGN853 intravenously once every 3 weeks at 6 mg/kg using adjusted ideal body weight dosing. Responses were assessed according to RECIST 1.1 and adverse events (AEs) evaluated by CTCAE v4.0. Results: A total of 37 EOC pts treated as part of the three phase I expansion cohorts (pooled population; n = 113) met the FORWARD I enrollment criteria of moderate to high tumor FRα levels (≥ 50% of cells with ≥ 2+ FRα expression) and 1-3 prior lines of therapy. In this group of pts with platinum-resistant disease, confirmed objective tumor responses were observed in 17 individuals (1 complete response [CR] and 16 partial responses [PR]) for an overall response rate (ORR) of 46% (95% CI, 29.5, 63.1) and a median PFS of 6.7 months (95% CI, 4.1, 9.0). The safety profile of the pooled population was consistent with that previously reported (ASCO Annual Meeting, 2016) with the most common AEs being diarrhea, fatigue, nausea, and blurred vision; these were low grade and readily managed. Conclusions: IMGN853 continues to be characterized by favorable tolerability and encouraging activity in pts with platinum-resistant EOC. In particular, both the ORR (46%) and PFS (6.7 months) achieved in this group of pts are superior to outcomes typically seen with established single-agent chemotherapy within the setting of primary platinum resistance. Overall, these analyses provide continued, robust support for the patient eligibility strategy employed in the phase III evaluation of IMGN853. Clinical trial information: NCT01609556.

miRNA profiling in a case: Control study of African American women with uterine serous carcinoma (USC)

e17116

Background: USC is an aggressive subtype of endometrial cancer associated with worse outcomes in African American patients. We evaluated differences in tumor miRNA expression by race, clinical and tumor characteristics, and survival outcomes. Methods: FFPE tumor tissue from hysterectomy specimens was identified for 29 African American cases. Case matching was performed by computer-based random assignment in a 1:1 ratio with Caucasian controls based on age ( < 70 vs. ≥70 years), stage (FIGO I/II vs. III/IV) and histologic subtype (pure vs. mixed). RNA was extracted from 77 specimens with sufficient tumor cellularity (54 tumors and 23 matched normal endometrium). miRNA array profiling was performed by microRNA Hi-Power Labeling (Hy3/Hy5) and hybridization to miRCURY LNA microRNA Array 7th Gen (Exiqon, Denmark). Analysis was performed with R/Bioconductor using a moderated t-statistic with multiple testing correction. Validation was done using the TCGA dataset. Results: Clinical and treatment characteristics were similar for cases and controls, although use of adjuvant radiation was less common in African Americans (p = 0.03). With a median follow-up of 43 months, 17 patients had recurrent or progressive disease. DFS and OS rates were similar by race (both logrank p > 0.5). Of 968 miRNAs analyzed, 649 were differentially expressed in normal endometrium vs. tumor. When compared by race, histologic subtype, stage or presence of LVI, no differentially expressed miRNAs were identified. In patients with disease recurrence at 3 years, miR-223 was significantly upregulated (fold change 1.5; p = 0.002). In validation using a TCGA dataset of 131 patients with mixed (n = 22) or pure serous (n = 109) histology, increased miR-223 expression ( > median) was associated with worse overall survival (HR 2.47; 95%CI 0.9-6.6). After adjustment for patient age and BMI, upregulation of miR-223 was a significant risk factor for death (adjusted HR 2.94; 95%CI 1.01-8.52). Conclusions: Upregulation of miR-223 was associated with disease recurrence in a cohort of women with uterine serous carcinoma and validated by TCGA data. miRNA profiling did not identify biological differences between African American and Caucasian patients.

Overall survival and updated progression-free survival results from a randomized phase 2 trial comparing the combination of olaparib and cediranib against olaparib alone in recurrent platinum-sensitive ovarian cancer

5535

Background: We previously reported that the combination of cediranib (ced) and olaparib (olap) improved progression-free survival (PFS) and overall response rates (ORR) in women with recurrent platinum-sensitive (plat-sens) high-grade serous (HGS) or BRCA-related ovarian cancer (OvCa) (NCT 01116648). We conducted an updated PFS and overall survival (OS) analysis. Methods: Patients (pts) across 9 centers were randomized 1:1 in this Ph 2 open label study to Olap (olap 400 mg capsules BID) or Ced/Olap (olap 200 mg capsules BID; ced 30 mg daily), stratified by BRCA status and prior anti-angiogenic therapy. Eligibility included pts with recurrent plat-sens HGS or BRCA-related OvCa. Pts had measurable disease by RECIST 1.1, PS 0 or 1, and the ability to take POs. No prior anti-angiogenics in the recurrent setting or prior PARP inhibitor was allowed. PFS was defined as time from randomization to radiographic progression or death. OS was defined as time from randomization to death. Results: Pts were enrolled from Oct 2011 to Jun 2013: 46 to Olap, 44 to Ced/Olap. 48 pts were known BRCA carriers (25 Olap; 23 Ced/Olap). As of Dec 21, 2016, 67 pts had a PFS event, and 52 pts had an OS event. Updated median PFS was 8.2 mos for Olap and 16.5 mos for Ced/Olap (HR 0.50, 95% CI 0.30-0.83, p=0.007). Median OS was 33.3 mos for Olap and 44.2 mos for Ced/Olap (HR 0.64, 95% CI 0.36-1.11, p=0.11). Within known germline BRCA mut carriers, updated PFS was 16.5 vs 16.4 mos (HR 0.75, p=0.42), and OS was 40.1 vs 44.2 mos (HR 0.79, p=0.55) for Olap and Ced/Olap, respectively. In pts without known germline BRCA mut, updated PFS was 5.7 vs 23.7 mos (HR 0.32, p=0.002), and OS was 23.0 vs 37.8 mos (HR 0.48, p=0.074). Conclusions: Updated PFS results consistently demonstrated that Ced/Olap significantly extended PFS compared to Olap in the overall population of women with plat-sens OvCa. In this Phase 2 study not powered to detect OS diferences, there was a trend towards OS improvement with Ced/Olap, particularly in pts without a known germline BRCA mutation. Results from ongoing studies of this oral combination in OvCa are of clinical interest. Clinical trial information: NCT 01116648.

The successful phase 3 niraparib ENGOT-OV16/NOVA trial included a substantial number of patients with platinum resistant ovarian cancer (OC)

5560

Background: Niraparib is a highly selective poly (ADP-ribose) polymerase (PARP) 1/2 inhibitor (PARPi); in preclinical studies, it concentrates in the tumor relative to plasma to deliver durable, near complete PARP inhibition and persistent antitumor effects.Niraparib demonstrated significantly longer progression free survival (PFS) vs placebo in patients (pts) with recurrent OC who were randomized following a complete response (CR) or partial response (PR) to platinum based chemotherapy in the controlled, double-blind phase 3 ENGOT-OV16/NOVA trial. To more fully characterize the NOVA trial population, we assessed platinum resistance status, defined as a duration of response to platinum < 6 months to the most recent (ultimate) platinum regimen. Analysis was limited to pts in the placebo arm, as inclusion of pts receiving active treatment (niraparib) would have confounded the ability to determine duration of response to platinum alone. Methods: Pts with recurrent OC, no prior PARPi use, ≥2 prior courses of platinum based chemotherapy, and CR or PR to the most recent platinum based chemotherapy were eligible. Pts were assigned to one of two cohorts based on g BRCA testing (g BRCAmut or non-g BRCAmut) and randomized 2:1 within each cohort to niraparib 300 mg or placebo qd until progressive disease (PD). Randomization occurred up to 8 weeks following the last dose of the most recent platinum based chemotherapy. PFS was measured from time of randomization to death or earliest PD as assessed by independent review committee. Estimated probability of pts having disease progression in each cohort and pooled across cohorts 6 months after the last dose of their most recent platinum therapy was calculated using the Kaplan-Meier methodology. Results: 181 pts were randomized to placebo (65 g BRCAmut and 116 non-g BRCAmut). Platinum resistance rate estimates for the g BRCAmut, non-g BRCAmut, and pooled cohorts were 42%, 53%, and 49%, respectively. Conclusions: Approximately half of the pts in the NOVA study, where niraparib treatment met its primary endpoint of prolonging PFS following a response to platinum, had developed platinum resistance to their last line of chemotherapy. Clinical trial information: NCT01847274.

Long-term benefit of niraparib treatment of recurrent ovarian cancer (OC)

5534

Background: Current therapies for recurrent OC include chemotherapy (C) or bevacizumab (B) in combination with C followed by continuous B, which showed improved progression-free survival (PFS) compared with C followed by placebo (P) over 3.4 months (GOG-0213) or 4.0 months (OCEANS). Potential impact of B on effectiveness of subsequent therapies has not been described. Niraparib (N) is a highly selective PARP 1/2 inhibitor (PARPi). In preclinical studies, N concentrates in the tumor; N showed significantly longer PFS vs P in patients (pts) with recurrent OC following complete/partial response (CR/PR) to platinum based chemotherapy (Plat) in the randomized, controlled, double-blind phase 3 ENGOT-OV16/NOVA trial. We report the long term effect of treatment with N and its impact on subsequent therapy. Methods: Eligibility for NOVA included recurrent OC, fallopian tube or peritoneal cancer, no prior PARPi use, and completion of ≥2 prior courses of Plat, with a CR or PR following the most recent Plat. Pts were enrolled into g BRCAmut or non-g BRCAmut cohorts based on BRCA mutation test results and randomized 2:1 to receive N 300 mg qd or P until progression of disease or death (PD). Tumors were tested for homologous recombination deficiency (HRD). Estimated probability of PD in each cohort at 12, 18 and 24 months post randomization, representing ~18, 24 and 30 months post chemotherapy initiation, was determined; the difference between PFS2 and PFS (PFS2-PFS) was evaluated in all randomized pts. Results: 203 pts were randomized in the g BRCAmut cohort. Of 350 pts randomized in the non-g BRCAmut cohort, 162 had HRD+ and 134 HRD− tumors. Estimated probability (product-limit method) of PFS at 12, 18 and 24 months was greater in the niraparib arm than in the placebo arm in each cohort and subgroup at each time interval. Probabilities (95% CI) at 24 months for niraparib vs control were 0.42 (0.30, 0.55) vs 0.16 (0.07, 0.28) (gBRCAmut) and 0.27 (0.19, 0.35) vs 0.12 (0.06, 0.21) (non-gBRCAmut). PFS2-PFS was similar in the 2 treatment arms in the combined cohorts (HR 1.02, 95% CI 0.765, 1.349). Conclusions: Niraparib provided long term benefit in pts with recurrent OC irrespective of g BRCAmut or HRD status, and no decrement in the benefit of subsequent therapy was observed. Clinical trial information: NCT01847274.

Clinically significant long-term maintenance treatment with olaparib in patients (pts) with platinum-sensitive relapsed serous ovarian cancer (PSR SOC)

5533

Background: In Study 19 (NCT00753545), a RCT in 265 pts with PSR SOC, the oral PARP inhibitor olaparib significantly improved progression-free survival (PFS) vs placebo (PBO), with the greatest benefit seen in pts with a BRCA1/2 mutation ( BRCAm); an interim overall survival (OS) analysis suggested an advantage for olaparib-treated pts (DCO: Sep 30, 2015; Ledermann et al, 2016). We report a planned final analysis of the long-term benefit of olaparib in pts with PSR SOC in Study 19. Methods: Pts who had received ≥2 prior regimens of platinum-based chemotherapy and were in response to their most recent regimen received olaparib (400 mg bid; capsules) or PBO until disease progression. Retrospective germline or tumor testing resulted in a known BRCAm status for 254/265 pts (96%). Results: At final DCO (May 9, 2016) median OS follow-up was 78.0 months. A long-term treatment benefit and the final hazard ratio (HR) for OS vs PBO (unadjusted for crossover: 13% of PBO pts – full analysis set [FAS]; 23% of PBO pts – BRCAm subgroup) is shown (Table). Details of BRCAwt pts on treatment for ≥6 years will be presented. No new safety signals or changes in olaparib tolerability profile were seen. Conclusions: The Study 19 final analysis shows that olaparib provides clinically significant, long-term treatment benefit in pts with PSR SOC. A durable benefit was seen in ≥10% of BRCAm and BRCAwt pts, who continued to receive and benefit from olaparib for ≥6 years–unprecedented in the relapsed ovarian cancer setting. Olaparib is well tolerated in this pt population and the analysis suggests olaparib confers an OS benefit in BRCAm pts. Clinical trial information: NCT00753545. [Table: see text]

Phase 2, two-group, two-stage, open-label study of avelumab in patients with microsatellite stable, microsatellite instable and POLE-mutated recurrent or persistent endometrial cancer

TPS5615

Background: The Cancer Genome Atlas project identified 2 groups of hypermutated endometrial cancers (ECs): an ultramutated group that harbored mutations in the exonuclease domain of polymerase e ( POLE), and a hypermutated group with microsatellite instability (MSI), the majority of which harbored MLH1 promoter methylation. We (Howitt, JAMA Onc 2015) and others have shown that POLE and MSI ECs are associated with higher number of predicted neoepitopes and tumor infiltrating lymphocytes, which is counterbalanced by overexpression of PD-1/PD-L1, suggesting that they may be excellent candidates for PD-1/PD-L1 blockade. Anti-PD-1 therapy has also demonstrated promising activity in mismatch repair deficient colorectal cancers and collectively in non-colorectal cancers (Le, NEJM 2015). Methods: This is an open-label, two-cohort, two-stage, phase 2 trial, of avelumab, a fully human IgG1 antibody directed against PD-L1, in two cohorts: i) a MSI/ POLE cohort including ECs with immunohistochemical (IHC) complete loss of expression of at least one of the mismatch repair (MMR) proteins and/or documented mutation in the exonuclease domain of POLE and ii) a MSS cohort including ECs with normal IHC expression of all MMR proteins. Key eligibility criteria include measurable disease, no upper limit of prior therapies, and any EC histology. Co-primary objectives include objective response rate and rate of progression-free survival at 6 months. Avelumab is administered at 10 mg/kg as 1-hour IV infusion every 2 weeks until disease progression or unacceptable toxicity; therapy may continue at the investigator’s discretion while awaiting radiologic confirmation of disease progression 4 weeks later. Maximum target enrollment is 70 patients (35 for each cohort). In the first stage, 16 patients will be enrolled in each cohort; if there are at least two objective responses or two patients progression-free at 6 months, accrual will continue to the second stage where 19 more patients will be enrolled for each cohort. Thus far, 16 patients have been enrolled, 13 on the MSS cohort and 3 on the MSI/ POLE cohort. Clinical trial information: NCT02912572.

Safety findings from FORWARD II: A Phase 1b study evaluating the folate receptor alpha (FRα)-targeting antibody-drug conjugate (ADC) mirvetuximab soravtansine (IMGN853) in combination with bevacizumab, carboplatin, pegylated liposomal doxorubicin (PLD), or pembrolizumab in patients (pts) with ovarian cancer

5553

Background: FORWARD II is a phase 1b study of the FRα-targeting ADC, mirvetuximab soravtansine (IMGN853), in combination with bevacizumab (BEV), carboplatin, PLD, or pembrolizumab in adults with FRα-positive EOC, primary peritoneal, or fallopian tube tumors (NCT02606305). Methods: The escalation stage of this trial evaluated the safety and tolerability of IMGN853 as part of 4 combination regimens: IMGN853 + BEV; + carboplatin; + PLD; and + pembrolizumab. IMGN853 was administered in combination on Day 1 of a 21 (BEV or carboplatin) or 28-day cycle (PLD). Pembrolizumab escalation is continuing. The starting dose of IMGN853 was 5 mg/kg (adjusted ideal body weight, AIBW), one level lower than the recommended single agent phase 2 dose (RP2D; 6 mg/kg AIBW) defined in a first-in-human study (NCT01609556). Adverse events (AEs) were evaluated by CTCAE v4.0. Results: 46 pts enrolled in the first 3 cohorts. IMGN853 was escalated from 5 to 6 mg/kg. Carboplatin and PLD dosing were escalated from AUC4 to AUC5 and 30 to 40 mg/m2, respectively; BEV dosing remained constant at 15 mg/kg. Diarrhea, nausea, and fatigue were common across cohorts (all grades; 33-57%) and mostly low grade (i.e. ≤ 2), consistent with the IMGN853 safety profile from the earlier phase I monotherapy study. AEs of interest related to the combination agents were seen in each arm. For example, grade 1/2 proteinuria (36%) and grade 3 hypertension (21%) were only observed in the BEV combination. Thrombocytopenia (44%) and neutropenia (39%), grades 1-3, occurred most frequently in the carboplatin arm. Grade 3 anemia and vomiting (each 14%), as well as low grade (≤ 2) constipation (43%), were seen in the PLD cohort. Conclusions: The RP2D dose of IMGN853 was readily combined with the highest doses (as per protocol) of BEV, carboplatin, and PLD. The AE profiles for these combinations were manageable and as expected based on known profiles of each agent; importantly, no new safety signals were identified. Updated data from all 4 combination regimens will be presented. Clinical trial information: NCT02606305.

Efficacy of niraparib on progression-free survival (PFS) in patients (pts) with recurrent ovarian cancer (OC) with partial response (PR) to the last platinum-based chemotherapy

5517

Background: Therapeutic paradigms for recurrent OC vary by geography. Maintenance following response to platinum-based chemotherapy (Plat) is standard in Europe, whereas in the US maintenance is considered following complete response (CR) vs treatment for partial response (PR). Niraparib is a highly selective PARP 1/2 inhibitor (PARPi). In preclinical studies it concentrates in the tumor relative to plasma, delivering > 90% durable PARP inhibition and antitumor effects. Niraparib demonstrated significantly longer PFS vs placebo (P) in pts with recurrent OC following a CR or PR to Plat in the randomized, controlled, double-blind phase 3 ENGOT-OV16/NOVA trial. Methods: Pts with recurrent OC, no prior PARPi use, ≥2 prior courses of Plat, and response to most recent Plat were eligible. Pts were assigned to 1 of 2 cohorts on the basis of g BRCA testing (g BRCAmut or non-g BRCAmut) and randomized 2:1 within each cohort to niraparib 300 mg or P qd until progressive disease (PD). Randomization occurred up to 8 weeks after last dose of the most recent Plat. Pts were stratified by time to progression after penultimate Plat (6 to < 12 months or ≥12 months), prior use of bevacizumab (yes/no), and response to most recent Plat (CR or PR). PFS was measured from time of randomization to death or earliest PD as assessed by independent review committee. Results: 49% of pts (niraparib: 67/138; P: 32/65) in the g BRCAmut and ~49% of pts (niraparib: 117/234 [50%]; P: 56/116 [48%]) in the non-g BRCAmut cohorts entered NOVA with a PR following their most recent Plat. At time of unblinding, 30 (45%) niraparib and 23 (72%) P pts in the g BRCAmut and 65 (56%) niraparib and 45 (80%) P pts in the non-g BRCAmut cohorts had PFS events. PFS hazard ratios (95% CI) were 0.24 (0.131–0.441) in g BRCAmut and 0.35 (0.230–0.532) in non-g BRCAmut cohorts for pts who had a PR to their most recent platinum regimen. This compared favorably to the overall NOVA study results, where PFS hazard ratios (95% CI) were 0.27 (0.173–0.410) in g BRCAmut and 0.45 (0.338–0.607) in non-g BRCAmut cohorts. Conclusions: Niraparib treatment provided significant benefit to pts with recurrent OC who achieved a PR following Plat. Clinical trial information: NCT01847274.

Prognostic importance of p16 status for women with vulvar squamous cell carcinoma (SCC) treated with radiotherapy

5599

Background: To evaluate the association between p16 status and in-field recurrence (IFR), progression-free (PFS) and overall (OS) survival in patients with vulvar SCC treated with radiation (RT) with or without surgical resection. Methods: In a multi-institutional retrospective cohort study, we identified 105 women with vulvar SCC who received RT between 1985-2011. Immunostaining for p16 was performed on archival tumor tissue using the Leica Bond III staining platform. Histopathology and p16 stains were reviewed by pathologists with expertise in gynecologic cancer; the intensity and extent of p16 staining in tumor cells were classified as negative (focal, weak, patchy) or positive (moderate or strong diffuse linear positive). Actuarial estimates of PFS, OS and IFR were calculated using the Kaplan-Meier method and compared by the logrank test. Multivariable analysis (MVA) was performed using the Cox proportional hazards model. Results: Patients with p16-positive disease were significantly younger at diagnosis (median 67 vs. 77 years) and were more likely to be current smokers (51% vs. 0%) and to have received concurrent chemotherapy (68% vs. 47%, all p<0.05). FIGO stage distribution, RT intent and median RT doses were similar by p16 status. With a median follow-up of 61 months, 5-year PFS and OS rates were 35% and 40%, respectively. Women with p16-positive tumors had significantly better 5-year PFS and OS rates than those with p16-negative tumors (61% and 23%, p<0.01 and 64% and 29%, p=0.01, respectively). The 5-year IFR rate was also lower for those with p16-positive disease (17% vs. 65%, p<0.01). On univariate analysis, use of concurrent chemotherapy was not associated with PFS (p=0.5), OS (p=0.3) or IFR (p=0.8). On MVA adjusted for age and stage, p16 positivity was significantly associated with better PFS (HR 0.57, 95% CI 0.33-0.97) and lower IFR (HR 0.24, 95% CI 0.09-0.6). Conclusions: In a multi-institutional setting, women with p16-positive vulvar SCC treated with RT had a lower IFR rate and longer survival than those with p16-negative disease. The magnitude of prognostic importance of p16 status is similar to that seen in oropharyngeal, anal and cervical cancers treated with RT.

Phase 1 dose-escalation study of mirvetuximab soravtansine (IMGN853), a folate receptor α-targeting antibody-drug conjugate, in patients with solid tumors

BACKGROUND

Mirvetuximab soravtansine (IMGN853) is an antibody-drug conjugate that selectively targets folate receptor α (FRα). In this phase 1 dose-escalation study, the authors investigated IMGN853 in patients with FRα-positive solid tumors.

METHODS

Patients received IMGN853 on day 1 of a 21-day cycle (once every 3 weeks dosing), with cycles repeated until patients experienced dose-limiting toxicity or progression. Dose escalation commenced in single-patient cohorts for the first 4 planned dose levels and then followed a standard 3 + 3 scheme. The primary objectives were to determine the maximum tolerated dose and the recommended phase 2 dose. Secondary objectives were to determine safety and tolerability, to characterize the pharmacokinetic profile, and to describe preliminary clinical activity.

RESULTS

In total, 44 patients received treatment at doses escalating from 0.15 to 7.0 mg/kg. No meaningful drug accumulation was observed with the dosing regimen of once every 3 weeks. The most common treatment-related adverse events were fatigue, blurred vision, and diarrhea, the majority of which were grade 1 or 2. The dose-limiting toxicities observed were grade 3 hypophosphatemia (5.0 mg/kg) and grade 3 punctate keratitis (7.0 mg/kg). Two patients, both of whom were individuals with epithelial ovarian cancer, achieved confirmed tumor responses according to Response Evaluation Criteria in Solid Tumors 1.1, and each was a partial response.

CONCLUSIONS

IMGN853 demonstrated a manageable safety profile and encouraging preliminary clinical activity, particularly in patients with ovarian cancer. The results establish a recommended phase 2 dosing of 6.0 mg/kg (based on adjusted ideal body weight) once every 3 weeks. Cancer 2017. © 2017 American Cancer Society. Cancer 2017;123:3080-7. © 2017 American Cancer Society.

Safety and Activity of Mirvetuximab Soravtansine (IMGN853), a Folate Receptor Alpha-Targeting Antibody-Drug Conjugate, in Platinum-Resistant Ovarian, Fallopian Tube, or Primary Peritoneal Cancer: A Phase I Expansion Study

Purpose This phase I expansion cohort study evaluated the safety and clinical activity of mirvetuximab soravtansine (IMGN853), an antibody-drug conjugate consisting of a humanized anti-folate receptor alpha (FRα) monoclonal antibody linked to the tubulin-disrupting maytansinoid DM4, in a population of patients with FRα-positive and platinum-resistant ovarian cancer. Patients and Methods Patients with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer received IMGN853 at 6.0 mg/kg (adjusted ideal body weight) once every 3 weeks. Eligibility included a minimum requirement of FRα positivity by immunohistochemistry (≥ 25% of tumor cells with at least 2+ staining intensity). Adverse events, tumor response (via Response Evaluation Criteria in Solid Tumors [RECIST] version 1.1), and progression-free survival (PFS) were determined. Results Forty-six patients were enrolled. Adverse events were generally mild (≤ grade 2), with diarrhea (44%), blurred vision (41%), nausea (37%), and fatigue (30%) being the most commonly observed treatment-related toxicities. Grade 3 fatigue and hypotension were reported in two patients each (4%). For all evaluable patients, the confirmed objective response rate was 26%, including one complete and 11 partial responses, and the median PFS was 4.8 months. The median duration of response was 19.1 weeks. Notably, in the subset of patients who had received three or fewer prior lines of therapy (n = 23), an objective response rate of 39%, PFS of 6.7 months, and duration of response of 19.6 weeks were observed. Conclusion IMGN853 exhibited a manageable safety profile and was active in platinum-resistant ovarian cancer, with the strongest signals of efficacy observed in less heavily pretreated individuals. On the basis of these findings, the dose, schedule, and target population were identified for a phase III trial of IMGN853 monotherapy in patients with platinum-resistant disease.

Use of CA-125 Tests and Computed Tomographic Scans for Surveillance in Ovarian Cancer

Importance

A 2009 randomized clinical trial demonstrated that using cancer antigen 125 (CA-125) tests for routine surveillance in ovarian cancer increases the use of chemotherapy and decreases patients' quality of life without improving survival, compared with clinical observation. The Society of Gynecologic Oncology guidelines categorize CA-125 testing as optional and discourage the use of radiographic imaging for routine surveillance. To date, few studies have examined the use of CA-125 tests in clinical practice.

Objectives

To examine the use of CA-125 tests and computed tomographic (CT) scans in clinical practice before and after the 2009 randomized clinical trial and to estimate the economic effect of surveillance testing.

Design, Setting, and Participants

A prospective cohort of 1241 women with ovarian cancer in clinical remission after completion of primary cytoreductive surgery and chemotherapy at 6 National Cancer Institute-designated cancer centers between January 1, 2004, and December 31, 2011, was followed up through December 31, 2012, to study the use of CA-125 tests and CT scans before and after 2009. Data analysis was conducted from April 9, 2014, to March 28, 2016.

Main Outcomes and Measures

The use of CA-125 tests and CT scans before and after 2009. Secondary outcomes included the time from CA-125 markers doubling to retreatment among women who experienced a rise in CA-125 markers before and after 2009, and the costs associated with surveillance testing using 2015 Medicare reimbursement rates.

Results

Among 1241 women (mean [SD] age 59 [12] years; 1112 white [89.6%]), the use of CA-125 testing and CT scans was similar during the study period. During 12 months of surveillance, the cumulative incidence of patients undergoing 3 or more CA-125 tests was 86% in 2004-2009 vs 91% in 2010-2012 (P = .95), and the cumulative incidence of patients undergoing more than 1 CT scan was 81% in 2004-2009 vs 78% in 2010-2012 (P = .50). Among women whose CA-125 markers doubled (n = 511), there was no significant difference in the time to retreatment with chemotherapy before and after 2009 (median, 2.8 vs 3.5 months; P = .40). During a 12-month period, there was a mean of 4.6 CA-125 tests and 1.7 CT scans performed per patient, resulting in a US population surveillance cost estimate of $1 999 029 per year for CA-125 tests alone and $16 194 647 per year with CT scans added.

Conclusions and Relevance

CA-125 tests and CT scans are still routinely used for surveillance testing in patients with ovarian cancer, although their benefit has not been proven and their use may have significant implications for patients' quality of life as well as costs.

Clear cell ovarian cancers with microsatellite instability: A unique subset of ovarian cancers with increased tumor-infiltrating lymphocytes and PD-1/PD-L1 expression

Clear cell ovarian carcinoma (CCOC) represents a distinct histologic subtype of ovarian cancer associated with significantly worse prognosis across all stages and no effective therapeutic options. Here, we report a rare but clinically important cohort of CCOCs with microsatellite instability (MSI) (MSI-CCOCs), which are highly immunogenic and may thus be very responsive to immune checkpoint blockade. CCOCs with MSI exhibit a significantly higher number of CD8⁺ TILs, higher CD8⁺/CD4⁺ ratio, and higher PD-1⁺ TILs compared with microsatellite stable (MSS) CCOCs and compared with high grade serous ovarian cancers, which are the most common histologic subtype of ovarian cancer. Of note, PD-L1 expression in tumor cells or immune cells was noted in all cases of CCOCs with MSI. These observations open an alternative therapeutic avenue for a fraction of patients with CCOC and argue for the routine testing of CCOCs for MSI, a test that is not currently routinely performed.

What Is the Place of PARP Inhibitors in Ovarian Cancer Treatment?

Poly-ADP-ribose polymerase (PARP) inhibitors have been one of the most exciting developments in the treatment of ovarian cancer in recent years. Demonstration of anti-cancer activity has led to the European Medicines Agency (EMA) approval of the PARP inhibitor (PARPi) olaparib as maintenance therapy in women with BRCA-mutated (BRCAm) ovarian cancer with platinum-sensitive recurrence following response to platinum therapy and the US Food and Drug Administration (US FDA) approval of olaparib in relapsed germline BRCA-mutated (gBRCAm) ovarian cancer in women who have received at least three prior chemotherapy treatments, both occurring in 2014. Additional trials are underway or awaiting final analysis with olaparib, other PARPis, and PARPi combinations to further elucidate the activity of these drugs in various clinical settings. This review will focus on the current clinical experience and ongoing trials with PARPis in ovarian cancer.

Biomarkers of Response and Resistance to DNA Repair Targeted Therapies

Drugs targeting DNA damage repair (DDR) pathways are exciting new agents in cancer therapy. Many of these drugs exhibit synthetic lethality with defects in DNA repair in cancer cells. For example, ovarian cancers with impaired homologous recombination DNA repair show increased sensitivity to poly(ADP-ribose) polymerase (PARP) inhibitors. Understanding the activity of different DNA repair pathways in individual tumors, and the correlations between DNA repair function and drug response, will be critical to patient selection for DNA repair targeted agents. Genomic and functional assays of DNA repair pathway activity are being investigated as potential biomarkers of response to targeted therapies. Furthermore, alterations in DNA repair function generate resistance to DNA repair targeted agents, and DNA repair states may predict intrinsic or acquired drug resistance. In this review, we provide an overview of DNA repair targeted agents currently in clinical trials and the emerging biomarkers of response and resistance to these agents: genetic and genomic analysis of DDR pathways, genomic signatures of mutational processes, expression of DNA repair proteins, and functional assays for DNA repair capacity. We review biomarkers that may predict response to selected DNA repair targeted agents, including PARP inhibitors, inhibitors of the DNA damage sensors ATM and ATR, and inhibitors of nonhomologous end joining. Finally, we introduce emerging categories of drugs targeting DDR and new strategies for integrating DNA repair targeted therapies into clinical practice, including combination regimens. Generating and validating robust biomarkers will optimize the efficacy of DNA repair targeted therapies and maximize their impact on cancer treatment. Clin Cancer Res; 22(23); 5651-60. ©2016 AACR.