Overcoming the challenges of drug development in platinum-resistant ovarian cancer

The definition of "platinum-resistant ovarian cancer" has evolved; it now also reflects cancers for which platinum treatment is no longer an option. Standard of care for platinum-resistant ovarian cancer is single-agent, non-platinum chemotherapy with or without bevacizumab, which produces modest response rates, with the greatest benefits achieved using weekly paclitaxel. Several recent phase 3 trials of pretreated patients with prior bevacizumab exposure failed to meet their primary efficacy endpoints, highlighting the challenge in improving clinical outcomes among these patients. Combination treatment with antiangiogenics has improved outcomes, whereas combination strategies with immune checkpoint inhibitors have yielded modest results. Despite extensive translational research, there has been a lack of reliable and established biomarkers that predict treatment response in platinum-resistant ovarian cancer. Additionally, in the platinum-resistant setting, implications for the time between the penultimate dose of platinum therapy and platinum retreatment remain an area of debate. Addressing the unmet need for an effective treatment in the platinum-resistant setting requires thoughtful clinical trial design based on a growing understanding of the disease. Recent cancer drug approvals highlight the value of incorporating molecular phenotypes to better define patients who are more likely to respond to novel therapies. Clinical trials designed per the Gynecologic Cancer InterGroup recommendations-which advocate against relying solely upon the platinum-free interval-will help advance our understanding of recurrent ovarian cancer response where platinum rechallenge in the platinum-resistant setting may be considered. The inclusion of biomarkers in clinical trials will improve patient stratification and potentially demonstrate correlations with biomarker expression and duration of response. With the efficacy of antibody-drug conjugates shown for the treatment of some solid and hematologic cancers, current trials are evaluating the use of various novel conjugates in the setting of platinum-resistant ovarian cancer. Emerging novel treatments coupled with combination trials and biomarker explorations offer encouraging results for potential strategies to improve response rates and prolong progression-free survival in this population with high unmet need. This review outlines existing data from contemporary clinical trials of patients with platinum-resistant ovarian cancer and suggests historical synthetic benchmarks for non-randomized trials.

Utilization of Poly(ADP-Ribose) Polymerase Inhibitors in Ovarian Cancer: A Retrospective Cohort Study of US Healthcare Claims Data

Introduction

We aimed to characterize real-world utilization of poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) in women with ovarian cancer (OC).

Methods

This retrospective observational study of claims data from US MarketScan^® Commercial/Medicare Supplemental databases included women with OC initiating olaparib, niraparib, or rucaparib from January 1, 2017, to May 31, 2019. Patients were observed from first outpatient prescription until at least 30 days’ follow-up. Clinical events of interest (CEIs), based on adverse reactions in PARPi prescribing information, were identified from claims using ICD-9/10 codes. Other outcomes included dose modification, persistence, adherence, healthcare resource utilization (HCRU), and cost.

Results

Overall, 303, 348, and 162 women with OC received olaparib, niraparib, and rucaparib, respectively. During follow-up, risk of any CEI was higher with niraparib versus olaparib (odds ratio 3.36 [95% confidence interval 2.00–5.65]) and niraparib versus rucaparib (2.09 [1.10–3.95]), with no significant difference between rucaparib and olaparib (1.61 [0.93–2.79]). PARPi dose decreases were observed in 21.1%, 35.1%, and 30.2% of olaparib-, niraparib-, and rucaparib-treated patients, respectively. Persistence (no treatment gaps of more than 90 days) was significantly higher (P < 0.05) with olaparib (62.2%) versus niraparib (35.9%) and rucaparib (48.7%); adherence (medication possession ratio, MPR ≥ 80%) was 80.2% versus 38.6% and 63.2%, respectively (P < 0.001). Inpatient admissions and outpatient service use were higher with niraparib and rucaparib versus olaparib, reflected in mean (± standard deviation) total medical costs (excluding pharmacy) of $5393 ± 8828 for olaparib, $7732 ± 14,054 for niraparib, and $6868 ± 7929 for rucaparib.

Conclusion

Differences between the licensed PARPi were observed in the risk of experiencing a CEI, likelihood of dose modifications, ability to receive continuous PARPi therapy, HCRU, and costs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12325-021-01959-5.

Abstract P046: ENGOT-ov60/GOG3052/RAMP 201: A phase 2 study of VS-6766 (dual RAF/MEK inhibitor) alone and in combination with defactinib (FAK inhibitor) in recurrent low-grade serous ovarian cancer (LGSOC)

Background: VS-6766 is a unique small molecule inhibitor that blocks MEK kinase activity and RAF phosphorylation of MEK. This mechanism of blockade has been shown to limit compensatory MEK activation, thereby potentially enhancing efficacy of MEK inhibition. Defactinib, (VS-6063), an orally active small molecule, is a potent adenosine 5'- triphosphate (ATP) competitive, reversible inhibitor of focal adhesion kinase (FAK). Defactinib has shown synergistic activity with BRAF and MEK inhibitors in both in vitro and in vivo solid tumor models. Prior molecularly unselected studies with single agent MEK inhibitors have shown response rates up to 26% in recurrent LGSOC. A third of patients with recurrent LGSOC harbor somatic KRAS mutations. FAK inhibition has been shown to induce tumor regression when combined with RAF, MEK or RAF/MEK inhibitors in in vivo models of KRAS mutant ovarian cancer. The combination of VS-6766 and defactinib is currently being evaluated in the ongoing Investigator Sponsored FRAME study (NCT03875820). In this proof of concept study, durable objective responses have been reported in recurrent LGSOC patients, particularly those with KRAS mutations including patients who have had a prior MEK inhibitor (Banerji et al AACR 2020). Based on preclinical studies demonstrating efficacy of both VS-6766 and the VS-6766/defactinib combination and preliminary results of the FRAME study, the phase II ENGOT-ov60/GOG3052 has been developed in recurrent LGSOC. Methods: This is a Phase II, adaptive, two-part, multicenter, parallel cohort, randomized, open label study designed to evaluate the efficacy and safety of VS-6766 versus VS-6766 in combination with defactinib (NCT04625270). The study will be conducted in two parts. Part A will determine the optimal regimen based on confirmed overall response rate (independent radiology review) in KRAS-mutated LGSOC. Part B will determine the efficacy of the optimal regimen identified in Part A in KRAS-mutated and KRAS wild-type LGSOC. The minimum expected enrollment is 52 subjects with KRAS-mutated tumors (32 subjects in Part A and 20 in Part B) and 36 with KRAS wild-type tumors in Part B. Patients will be randomized to receive VS-6766 (4.0 mg PO, twice weekly 3 weeks on, 1 week off) or VS6766 with defactinib (VS-6766 3.2 mg PO, twice weekly + defactinib 200 mg PO BID 3 weeks on, 1 week off) till progression. Key inclusion criteria include histologically confirmed LGSOC, presence of KRAS mutation (Part A), prior systemic therapy for metastatic disease and up to 1 prior line of MEK/RAF inhibitor therapy permitted. This international study is open to enrollment.

Citation Format: Susana N. Banerjee, Bradley J. Monk, Els Van Nieuwenhuysen, Kathleen N. Moore, Ana Oaknin, Michel Fabbro, Nicoletta Columbo, David M. O’Malley, Robert L. Coleman, Jonathan Pachter, Andrew Koustenis, Gloria Patrick, Lorna Leonard, Rachel Grisham. ENGOT-ov60/GOG3052/RAMP 201: A phase 2 study of VS-6766 (dual RAF/MEK inhibitor) alone and in combination with defactinib (FAK inhibitor) in recurrent low-grade serous ovarian cancer (LGSOC) [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P046.

Adjuvant Gemcitabine Plus Docetaxel Followed by Doxorubicin Versus Observation for High-Grade Uterine Leiomyosarcoma: A Phase III NRG Oncology/Gynecologic Oncology Group Study

PURPOSE

We conducted a randomized phase III trial to determine whether adjuvant chemotherapy improves survival in women with uterine leiomyosarcoma.

METHODS

Women with uterus-confined, high-grade leiomyosarcoma who were confirmed disease free by imaging were randomly assigned to four cycles of gemcitabine plus docetaxel, followed by four cycles of doxorubicin, or to observation. All were followed for evidence of recurrence. The primary end point was overall survival (OS).

RESULTS

With international collaboration, 38 of the targeted accrual of 216 patients were enrolled, after which the study was closed by the National Cancer Institute for accrual futility. Twenty patients were assigned to chemotherapy, 18 to observation. Among the 17 patients treated with at least one cycle of chemotherapy, grade 3 or 4 toxicities were observed in 47%; among the 18 patients assigned to observation, one had grade 3 hypertension. There were six deaths (chemotherapy, n = 5; observation, n = 1), all due to disease. The restricted mean survival time for OS was estimated as 34.3 months (95% CI, 25.3 to 43.3 months) in the chemotherapy arm and as 46.4 months (95% CI, 43.6 to 49.1 months) in the observation arm. There were eight recurrences in each arm. The restricted mean survival time for recurrence-free survival was estimated as 18.1 (95% CI, 14.2 to 22.0) months in the chemotherapy arm and as 14.6 months (95% CI, 10.3 to 19.0 months) in the observation arm. Neither survival outcome comparison was considered statistically robust, due to the small sample size.

CONCLUSION

Despite international collaboration to test the role of adjuvant chemotherapy in uterine-confined leiomyosarcoma, this study was closed for accrual futility. Although the sample size precludes robust statistical comparison, observed OS and recurrence-free survival data do not show superior outcomes with adjuvant chemotherapy.

Abstract PR06: ARIEL3: A phase 3, randomized, double-blind study of rucaparib vs placebo following response to platinum-based chemotherapy for recurrent ovarian cancer (OC)

Background: Rucaparib, a poly(ADP-ribose) polymerase (PARP) inhibitor, is approved in the United States for treatment of women with deleterious BRCA mutation (germline and/or somatic) associated advanced OC who have been treated with two or more chemotherapies. Rucaparib has also demonstrated antitumor activity in the treatment setting in patients (pts) with BRCA wild-type associated recurrent OC whose tumor has high genomic loss of heterozygosity (LOH). ARIEL3 evaluated rucaparib vs placebo as maintenance treatment in pts with recurrent platinum-sensitive OC.

Methods: Eligible pts received ≥2 prior platinum-based therapies, had platinum-sensitive OC (disease progression ≥6 mo after penultimate platinum), and achieved a complete response (RECIST v1.1) or partial response (RECIST v1.1 or Gynecologic Cancer InterGroup CA-125 criteria) to their most recent platinum. All pts were required to have CA-125 less than the upper limit of normal. Pts were randomized 2:1 to receive oral rucaparib 600 mg BID or placebo. Investigator-assessed progression-free survival (PFS) (primary endpoint) was assessed in a step-down procedure for 3 nested cohorts: (1) BRCA mutant (deleterious germline or somatic BRCA mutation); (2) homologous recombination deficient (HRD) (BRCA mutant or BRCA wild type/LOH high); and (3) intent-to-treat (ITT) population. PFS was also assessed by blinded independent central review (BICR) (secondary endpoint) and LOH status in pts with BRCA wild type OC (exploratory endpoint). Adverse events (AEs) were summarized descriptively.

Results: ARIEL3 enrolled 564 pts (375, rucaparib; 189, placebo). Nearly 200 pts (n=196) had BRCA mutation-associated OC. Of these pts, 130 had a germline BRCA mutation (82 [21.9%], rucaparib; 48 [25.4%], placebo), 56 had a somatic BRCA mutation (40 [10.7%], rucaparib; 16 [8.5%], placebo), and 10 pts had tumors with germline and/or somatic BRCA status unknown (8 [2.1%], rucaparib; 2 [1.1%], placebo). Median investigator-assessed PFS in the BRCA-mutant cohort (130, rucaparib; 66 placebo) was 16.6 mo vs 5.4 mo (hazard ratio [HR], 0.23; 95% confidence interval [CI], 0.16-0.34; P&lt;0.0001). In the HRD cohort (236, rucaparib; 118, placebo), median PFS was 13.6 mo vs 5.4 mo (HR, 0.32; 95% CI, 0.24-0.42; P&lt;0.0001), and in the ITT population, median PFS was 10.8 mo vs 5.4 mo (HR, 0.37; 95% CI, 0.30-0.45; P&lt;0.0001). Median PFS by BICR in the BRCA-mutant cohort was 26.8 mo vs 5.4 mo (HR, 0.20; 95% CI, 0.13-0.32; p&lt;0.0001). In the HRD cohort, median PFS by BICR was 22.9 mo vs 5.5 mo (HR, 0.34; 95% CI, 0.24-0.47; p&lt;0.0001), and in the ITT population, median PFS by BICR was 13.7 mo vs 5.4 mo (HR, 0.35; 95% CI, 0.28-0.45; p&lt;0.0001). In the safety population (372, rucaparib; 189, placebo), the most common treatment-emergent AEs (≥35% of pts in either arm) included nausea (75.3% and 36.5%), asthenia/fatigue (69.4% and 43.9%), dysgeusia (39.2% and 6.9%), anemia (37.4% and 5.8%), constipation (36.6% and 23.8%), and vomiting (36.6% and 14.8%). The most common grade 3 or higher treatment-emergent AEs were anemia (18.8% and 0.5%) and alanine/aspartate aminotransferase increase (10.5% and 0%). At the visit cutoff date (15 April 2017), 13.4% and 1.6% of pts discontinued maintenance treatment due to treatment-emergent AEs (excluding disease progression), and 1.6% and 1.1% of pts died due to treatment-emergent AEs (including disease progression).

Conclusion: Rucaparib significantly improved PFS vs placebo in pts with platinum-sensitive, recurrent OC in all primary analysis groups of pts with platinum-sensitive, recurrent OC. Additionally, rucaparib significantly improved PFS vs placebo in pts with BRCA wild-type OC (LOH high and LOH low).

Clinical trial identification: NCT01968213.

This abstract is also being presented as Poster A47.

Citation Format: Robert L. Coleman, Amit M. Oza, Domenica Lorusso, Carol Aghajanian, Ana Oaknin, Andrew Dean, Nicoletta Colombo, Johanne I. Weberpals, Andrew Clamp, Giovanni Scambia, Alexandra Leary, Robert W. Holloway, David M. O’Malley, Terri Cameron, Lara Maloney, Sandra Goble, Kevin Lin, James Sun, Heidi Giordano, Jonathan A. Ledermann. ARIEL3: A phase 3, randomized, double-blind study of rucaparib vs placebo following response to platinum-based chemotherapy for recurrent ovarian cancer (OC). [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr PR06.

Identification of 12 new susceptibility loci for different histotypes of epithelial ovarian cancer

To identify common alleles associated with different histotypes of epithelial ovarian cancer (EOC), we pooled data from multiple genome-wide genotyping projects totaling 25,509 EOC cases and 40,941 controls. We identified nine new susceptibility loci for different EOC histotypes: six for serous EOC histotypes (3q28, 4q32.3, 8q21.11, 10q24.33, 18q11.2 and 22q12.1), two for mucinous EOC (3q22.3 and 9q31.1) and one for endometrioid EOC (5q12.3). We then performed meta-analysis on the results for high-grade serous ovarian cancer with the results from analysis of 31,448 BRCA1 and BRCA2 mutation carriers, including 3,887 mutation carriers with EOC. This identified three additional susceptibility loci at 2q13, 8q24.1 and 12q24.31. Integrated analyses of genes and regulatory biofeatures at each locus predicted candidate susceptibility genes, including OBFC1, a new candidate susceptibility gene for low-grade and borderline serous EOC.

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.