Development of a [89Zr]Zr-labeled human antibody using a novel phage-displayed human scFv library.

PURPOSE: Tax-interacting protein 1 (TIP1) is a cancer-specific radiation-inducible cell surface antigen that plays a role in cancer progression and resistance to therapy. This study aimed to develop a novel anti-TIP1 human antibody for noninvasive PET imaging in cancer patients.

EXPERIMENTAL DESIGN: A phage-displayed scFv library was created from healthy donors' blood. High-affinity anti-TIP1 scFvs were selected from the library and engineered to human IgG1. Purified antibodies (Abs) were characterized by size-exclusion chromatography-HPLC (SEC-HPLC), native mass spectrometry (native MS), ELISA, BIAcore, and flow cytometry. The labeling of positron emitter [89Zr]Zr to the lead Ab, L111, was optimized using deferoxamine (DFO) chelator. The stability of [89Zr]Zr-DFO-L111 was assessed in human serum. Small animal PET studies were performed in lung cancer tumor models (A549 and H460).

RESULTS: We obtained 95% pure L111 by SEC-HPLC. Native MS confirmed the intact mass and glycosylation pattern of L111. Conjugation of 3 molar equivalents of DFO led to the optimal DFO-to-L111 ratio of 1.05. Radiochemical purity of 99.9% and specific activity of 0.37 MBq/μg was obtained for [89Zr]Zr-DFO-L111. [89Zr]Zr-DFO-L111 was stable in human serum over seven days. The immunoreactive fraction in cell surface binding studies was 96%. In PET, preinjection with 4 mg/kg cold L111 before [89Zr]Zr-DFO-L111 (7.4 MBq; 20 μg) significantly (P<0.01) enhanced the tumor-to-muscle SUVmax ratios on day 5 compared to day 2 postinjection.

CONCLUSIONS: L111 Ab targets lung cancer cells in vitro and in vivo. [89Zr]Zr-DFO-L111 is a human antibody that will be evaluated in the first-in-human study of safety and PET imaging.