EGFR-directed fluorescent affibody ABY-029 for phase 0 trial studies

Molecular guided surgery has potential as a critical tool to enhance extent of tumor resection in a range of cancers, and the evolution towards this surgical paradigm is largely just limited by the speed by which targeted imaging agents are cleared for human use by the FDA. The ABY-029 small molecule bioconjugate was developed through an NIH-funded Academic- Industry partnership, to test use of synthetic protein-dye conjugates through preclinical development and toxicity studies linked to a Phase 0 microdose clinical trial. The design of a human microdose trial in recurrent glioma patients allows for approval with limited pre-clinical single dose toxicity data in a single species, and small production runs of the agent, through peptide synthesis, thereby providing a low cost and yet high production rate of small specific probe molecules. Specifically, ABY-029 is composed of synthetic anti-epidermal growth factor receptor (EGFR; also called ErbB-1) Affibody molecule (Z03115-Cys) conjugated to IRDye800CW under GMP conditions. Toxicity analysis in rats demonstrated that signal-dose ABY-029 produced no pathological evidence of toxicity at any of the dose levels tested (up to 1000x an equivalent human microdose level). The objective of the Phase 0 study is to evaluate the binding specificity of ABY- 029 in recurrent glioma patients who have tumors with pathology-confirmed EGFR positive status. Preclinical studies in F98 EGFR-positive and EGFRvIII-mutated orthotopic rat tumors and U251 orthotopic xenograft tumors show a strong EGFR specificity and tumor-to-background ratio of between 4:1 and 8:1 depending on the type and location. EGFR-negative tumors showed only very little, perfusion-driven contrast of 2:1 suggesting a dominant molecular-based contrast mechanism. To enable visualization of sub-micromolar concentrations of ABY-029, a conventional operating microscope was fit with a high-powered light source and a near-infrared sensitive fluorescence camera. Preclinical evaluation of this device showed a lack of sensitivity to 1x microdose levels of ABY-029 in a U251 orthotopic glioma, borderline sensitivity to 3x microdose and robust signal in 6x microdose. Therefore, following successful eIND application, the first in-human clinical study is designed to allow escalation of dose from 1x to 3x to 6x, with transition to the next dose permitted only after an absence of detected signal on at least 2 patients. The study was approved by the Dartmouth IRB and register