Evaluation of an Anti-cancer Immunotherapy Combined With Standard Neoadjuvant Treatment in Patients With WT1-positive Primary Invasive Breast Cancer

The study will be conducted in two consecutive segments (Phase I and Phase II), each with specific objectives. Active follow-up will be for three years. Patients in this study will be allocated to cohorts as below. Cohort A will include postmenopausal patients with hormone receptor-positive breast cancer who receive aromatase inhibitor (AI) as neoadjuvant therapy concurrently with administration of 6 or 8 doses of WT1 anti-cancer immunotherapy (WT1 ASCI)/placebo starting on Day 0. AI treatment will be administered daily for duration of either 18 (if 6 doses of WT1 ASCI/placebo) or 24 weeks (if 8 doses of WT1 ASCI/placebo). Cohort B will include breast cancer patients who will receive neoadjuvant chemotherapy concurrently with administration of WT1 ASCI/placebo starting on Day 0. Neoadjuvant chemotherapy in Cohort B will consist either 1) if 6 doses of WT1 ASCI/placebo: 6 cycle-treatment chemotherapy regimens consist of 6, three-weekly cycles of anthracycline/taxane-based therapy, or 2) if 8 doses of WT1 ASCI/placebo: 8 cycle-treatment regimens consisting of 4 three-weekly cycles of anthracycline-based therapy followed by 4 three-weekly or 12-weekly taxane administrations without trastuzumab. Cohort C will include patients with Human Epidermal Growth Factor Receptor 2 (HER2)-overexpressing breast cancer who will receive neoadjuvant trastuzumab (Herceptin) therapy combined with chemotherapy concurrently with administration of WT1 ASCI/placebo starting on Day 0. Neoadjuvant chemotherapy in Cohort C will consist either 1) if 6 doses of WT1 ASCI/placebo: 6 cycle-treatment chemotherapy regimens consist of 6, three-weekly cycles of anthracycline/taxane-based therapy, or 2) if 8 doses of WT1 ASCI/placebo: 8 cycle-treatment regimens consisting of 4 three-weekly cycles of anthracycline-based therapy followed by 4 three-weekly or 12-weekly taxane administrations with trastuzumab. Cohorts D and E will include patients with hormone receptor-positive and HER2 non-overexpressing breast cancer who will receive neoadjuvant chemotherapy. For patients in these Cohorts D and E, WT1 ASCI/placebo (placebo applicable only for Cohort E patients) will be administered on Day 14 of each three-weekly cycle of chemotherapy. Neoadjuvant chemotherapy in Cohorts D and E will consist either 1) if 6 doses of WT1 ASCI/placebo: 6 cycle-treatment chemotherapy regimens consist of 6, three-weekly cycles of anthracycline/taxane-based therapy, or 2) if 8 doses of WT1 ASCI/placebo: 8 cycle-treatment regimens consisting of 4 three-weekly cycles of anthracycline-based therapy followed by 4 three-weekly taxane administrations without trastuzumab. Enrolment in Cohort E will be conditional on the absence of a safety signal and on the adequate induction of an immune response by the WT1 ASCI in Cohort D (defined as \>= 40% response rate based on post-Dose 4 anti-WT1 antibody responses in at least six patients). If this criterion is met, 60 patients (40 receiving WT1 ASCI and 20 placebo) with identical eligibility criteria will be enrolled into Cohort E. In case no adequate safety and/or immunogenicity will be obtained in Cohort D, recruitment in Cohort E will not be initiated. The protocol has been updated following Protocol Amendment 4, April 2013, leading to the update of the study design.