Initial phase 1 study of WT2725 dosing emulsion in patients with advanced malignancies.

Abstract

2066 Background: WT2725 is a Wilms’ tumor (WT1)-derived-oligopeptide vaccine intended to induce WT1 specific cytotoxic T-lymphocytes against WT1 positive tumors in HLA-A*0201+ or HLA-A*0206+. This first in human study of WT2725 was conducted to evaluate the safety, tolerability, and efficacy. Methods: Subjects with progressive or recurrent glioblastoma (GBM), acute myeloid leukemia (AML) (patients in morphologic remission with minimal residual disease determined by WT1 RT-PCR were allowed), non-small cell lung cancer (NSCLC), or ovarian cancer despite standard therapy were treated with 0.3, 0.9, 3, and 9 mg of WT2725 subcutaneously (s.c.) every week for 4 weeks, then every other week for 6 weeks, and every 4 weeks thereafter until progression or other discontinuation event (part 1); and with 18 mg and 27 mg of WT2725 s.c. every week for 8 weeks, then every other week for 10 weeks, and every 4 weeks thereafter until progression or other discontinuation event (part 2). Responses were evaluated by Immune-related Response Criteria (irRC) for solid tumors and modified International Working Group (IWG) for AML. Results: 62 subjects were dosed, the most frequent adverse events were grade 1 injection site reactions (no grade 3 injection site reactions or dose limiting toxicities observed). Of the 21 GBM subjects who were dosed, seven survived for ≥ 1 year (33%). Of these seven subjects, three survived for ≥18 months (14%), and two for ≥2 years (both in complete radiologic remission, 9.5%). One of the seven subjects with ≥1 year survival had previous treatment with bevacizumab. Two subjects continue dosing (1 complete response with no measurable disease >3 years and 1 partial response > 13 months on study). Results in subjects with non-GBM tumors (12 subjects with AML, 21 with ovarian CA, 7 with NSCLC, and 1 other cancer) are not presented here. WT1-specific CTLs and tumor burden was monitored. WT1 specific CTLs were associated with decrease of tumor burden in two patients with low tumor burden. Some patients with high disease burden did not respond. Conclusions: Preliminary data suggests WT2725 is well tolerated with potential antitumor activity in GBM patients, supporting future development of WT2725 for treatment of GBM in selected subjects. Clinical trial information: NCT01621542.