Five Prime Therapeutics Presents Monotherapy Data from the Phase 1a/1b Trial of FPA150 in Patients with Advanced Solid Tumors at the 2019 ASCO Annual Meeting
The data are the first presentation of FPA150 results and include safety and pharmacokinetics results from the Phase 1a monotherapy dose escalation portion of the study. The Phase 1a monotherapy portion of the study is being conducted in patients with advanced solid tumors, and the Phase 1b monotherapy expansion is enrolling patients with breast, ovarian and endometrial tumors that overexpress B7-H4.
“FPA150 is a first-in-class B7-H4 antibody that blocks inhibitory signaling to CD8 T cells and promotes the killing of B7-H4 overexpressing tumors through enhanced ADCC,” said Jasgit Sachdev, M.D. and Director of Breast and Gynecologic Early Phase Trials at the HonorHealth Research Institute. “It is promising to see in this study that FPA150 was well tolerated at doses as high as 20mg/kg with no dose-limiting toxicities.”
The open-label, multi-dose, multi-center Phase 1a dose escalation study was conducted in patients with advanced-stage solid tumors regardless of B7-H4 overexpression at monotherapy doses ranging from 0.01 to 20 mg/kg every three weeks in an accelerated titration followed by 3+3 design and in a separate dose exploration cohort in which patients with tumors that overexpress B7-H4 were treated at doses of 3 or 10 mg/kg every three weeks with mandatory pre- and on-treatment biopsies.
FPA150 monotherapy demonstrated a favorable safety profile with no dose-limiting toxicities or treatment-related serious adverse events. Evaluation of anti-tumor activity is ongoing. A recommended dose of 20 mg/kg every three weeks was selected based on safety and pharmacokinetics.
“Rapid enrollment of this first-in-human study of a novel targeted agent with checkpoint blockade and ADCC activity highlights the significant unmet need in patients with advanced breast and gynecologic cancers,” said Helen Collins, Chief Medical Officer of Five Prime Therapeutics. “The preliminary data from the Phase 1a portion of this study, in patients with tumors overexpressing B7-H4, support continued evaluation of FPA150 in the monotherapy and in the anti-PD1 combination therapy setting.”
Of the 29 patients in the Phase 1a portion of the study,18 had B7-H4 positive tumors based on medium or high immunohistochemistry (IHC) scores, including 11 patients with advanced ovarian cancer. Of these, one patient with ovarian cancer, who had been treated with seven prior lines of therapy including anti-PD1 therapy, achieved a confirmed partial response with a duration of 6.2 months.
Monotherapy Phase 1b expansion began in February 2019 and is enrolling cohorts of patients with B7-H4 positive breast, ovarian and endometrial cancers at a dose of 20 mg/kg every three weeks. A safety lead-in of the combination of Keytruda® (pembrolizumab), a PD1 antibody, and FPA150 has also begun enrolling patients with B7-H4 positive ovarian cancer. The company expects to present preliminary efficacy results from the monotherapy expansion cohorts and early safety results from the FPA150-Keytruda combination at the European Society of Medical Oncology in September 2019.
FPA150 is a novel, fully human, afucosylated monoclonal antibody targeting B7-H4. B7-H4 overexpression is observed in multiple solid tumors, including breast and gynecologic cancers. FPA150 is designed with a dual mechanism of action: blocking the T cell checkpoint activity of B7-H4 as well as promoting enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) against tumor cells expressing B7-H4.
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