Abstract OT2-6-15: Efficacy and Safety of Vintafolide Alone and Vintafolide Plus Paclitaxel Vs Paclitaxel Alone in Advanced Triple Negative Breast Cancer Subjects Using Etarfolatide Subject Selection

Abstract Background: Vintafolide (V) is a folic acid-vinca alkaloid small molecule drug conjugate that targets tumors that over-express the folate receptor (FR). 99mTc-etarfolatide (EC20) is a folate-targeted molecular imaging agent being developed to identify FR-positive tumors. Data suggest that triple negative breast cancers (TNBCs) expressing high levels of FR are likely to benefit from treatment with vintafolide. Trial design/Patient eligibility: This is a multicenter, randomized, open-label, Phase IIa trial in subjects with advanced TNBC. Patients will be evaluated for tumor specific expression of the FR using a EC20 SPECT/CT scan and classified as FR(100%) if 100% of RECIST 1.1 target lesions are FR-positive. Only FR(100%) patients are eligible for treatment and will be randomized in a 1:1:1 ratio to V alone, V + paclitaxel (P) or P alone. V will be administered at 2.5 mg IV 3x/week for 2 weeks on Days 1, 3, 5, 15, 17 and 19 of a 28-day cycle. P will be administered at 80 mg/m2 IV on Days 1, 8, 15, and 22. Specific aims: The primary endpoint for the trial is centrally assessed progression free survival (PFS). Secondary objectives include: assess the frequency of target tumors expressing FR(100%) vs FR(20-80%) vs FR(0%) in subjects with TNBC using EC20 SPECT scans; compare the clinical activity in subjects with advanced TNBC of V alone vs P and V + P vs P alone as measured by objective response rate (ORR), (complete response [CR] + partial response [PR]), clinical benefit rate (CBR; CR + PR + stable disease for ≥6 months), and overall survival; and assess the safety and tolerability of V alone vs P alone and V + P vs P alone in subjects with advanced TNBC. Statistical methods and target accrual: PFS and overall survival will be assessed in the intention to treat population using a stratified Cox model with Efron's tie handling method, and Kaplan-Meier method for PFS and OS curve estimation, respectively, in each treatment group. Inferential comparisons between the arms will be tested using the stratified log-rank test at one sided alpha level of 5%. This study will randomize 34 subjects into each treatment group with total study duration of ∼16-17 months. The study has 80% power to demonstrate that either patients treated with V or patients treated with V + P combination have a higher median time to an event of PFS than subjects treated with P at an unadjusted one-sided, 5% alpha-level, if the underlying constant hazard ratio between treatment groups is 0.5 and median survival time of 2.6 months. First patient enrollment is targeted for October. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT2-6-15.