A mouse-human phase 1 co-clinical trial of a protease-activated fluorescent probe for imaging cancer

Abstract

Local recurrence is a common cause of treatment failure for patients with solid tumors. Intraoperative detection of microscopic residual cancer in the tumor bed could be used to decrease the risk of a positive surgical margin, reduce rates of reexcision, and tailor adjuvant therapy. We used a protease-activated fluorescent imaging probe, LUM015, to detect cancer in vivo in a mouse model of soft tissue sarcoma (STS) and ex vivo in a first-in-human phase 1 clinical trial. In mice, intravenous injection of LUM015 labeled tumor cells, and residual fluorescence within the tumor bed predicted local recurrence. In 15 patients with STS or breast cancer, intravenous injection of LUM015 before surgery was well tolerated. Imaging of resected human tissues showed that fluorescence from tumor was significantly higher than fluorescence from normal tissues. LUM015 biodistribution, pharmacokinetic profiles, and metabolism were similar in mouse and human subjects. Tissue concentrations of LUM015 and its metabolites, including fluorescently labeled lysine, demonstrated that LUM015 is selectively distributed to tumors where it is activated by proteases. Experiments in mice with a constitutively active PEGylated fluorescent imaging probe support a model where tumor-selective probe distribution is a determinant of increased fluorescence in cancer. These co-clinical studies suggest that the tumor specificity of protease-activated imaging probes, such as LUM015, is dependent on both biodistribution and enzyme activity. Our first-in-human data support future clinical trials of LUM015 and other protease-sensitive probes.

Tumor-Specific Uptake of Fluorescent Bevacizumab–IRDye800CW Microdosing in Patients with Primary Breast Cancer: A Phase I Feasibility Study

“…Several approaches have been used showcasing the potential of fluorescence imaging in humans, varying from single-dose to dose-escalation designs differing from our microdosing approach. In particular, the ex vivo validation steps for visualization of tumor microdistribution of the NIR fluorescent tracer and its relationship to histologic immunohistochemical parameters provides a framework that was not reported earlier in previous clinical studies in, for example, fluorescein-conjugated CEA-targeted imaging in colorectal cancer (25), folate receptor-a imaging in ovarian cancer (26), the study of Rosenthal and colleagues using cetuximab-IRDye800CW in head and neck cancer (29), and a protease-activatable probe in soft tissue sarcoma and breast cancer (30). Therefore, the impact of our study is that it provides the necessary framework of evaluation and reporting of future clinical studies of fluorescence image-guided surgery.…”

“…More recently, Burggraaf and colleagues demonstrated c-met-targeted endoscopy fluorescence imaging in humans using a fluorescent dye of 650 nm (28), whereas Rosenthal and colleagues have demonstrated the feasibility of using the therapeutic mAb cetuximab targeting EGFR as the targeting moiety of an NIRF tracer in patients with head and neck cancer (29). In addition, the clinical application of a proteaseactivatable tracer has been reported in patients with soft tissue sarcoma and breast cancer (30).…”

Improved resection and prolonged overall survival with PD-1-IRDye800CW fluorescence probe-guided surgery and PD-1 adjuvant immunotherapy in 4T1 mouse model

“…With tumor-specific probes, breast tumor specimens can be detected, dissected, and then intraoperatively evaluated by image-guided approaches. 6 The applicability of intraoperative tumor-specific fluorescence imaging for real-time tumor visualization was successfully demonstrated in a first-inhuman analysis in breast cancer. 1 Studies in mice have demonstrated that residual fluorescence in the tumor margins correlates with local recurrence, whereas image-guided surgery improved outcomes.…”

Advances in fluorescent-image guided surgery

“…Clinical trials have recently begun using LUM015, a protease-activated fluorescent molecule, constituting the first in-human phase 1 clinical trial of this type of imaging probe (36). The activation of LUM015 relies on cathepsin proteases, enzymes commonly overexpressed by tumors (37).…”

“…LUM015 is optically inactive under normal conditions, but upon proteolytic cleavage by specific cathepsins, a covalently attached quencher molecule is released and fluorescence signal greatly intensifies (36). LUM015 was injected intravenously into 15 patients with either invasive ductal carcinoma or soft tissue sarcoma and was well tolerated with no adverse pharmacological activity (36).…”