Cardiac inotropy and cardiac calcium sensitization of PanLN800(-Forte), a cationic heptamethine indocyanine fluorescent contrast agent for intraoperative pan lymph node imaging.

Introduction: Accurate staging of malignancies often requires comprehensive evaluation of lymph nodes. However, finding these lymph nodes during oncological surgery is a daunting and time-consuming task, which increases the risk of missed lymph nodes and complications. Near-infrared (NIR) fluorescence imaging with the experimental fluorescent contrast agent PanLN800(-Forte) could provide real-time identification of lymph nodes and may solve this longstanding problem. In the current study we performed the preclinical toxicology evaluation of PanLN800(-Forte) towards its clinical translation for intraoperative pan lymph node imaging in thoracic surgery.

Methods: A single extended dose toxicology study was conducted to determine the safety and potential toxicity of PanLN800(-Forte) after administration of a single intravenous dose to Wistar Han rats. The study included a control group and two treatment groups (5.0 mg/kg and 15.0 mg/kg PanLN800(-Forte)), each consisting of 10 male and 10 female rats. Experimental endpoints included moribundity/mortality, clinical signs, body weights, body weight gains, clinical pathology, toxicity, and gross necropsy observations.

Results: Unexpected acute mortality was observed after administration of 5.0 mg/kg PanLN800(-Forte) to rats. No clear cause of sudden death was found after gross necropsy and pathology observations. To understand the mechanism of toxicity of PanLN800(-Forte), several additional tests were performed. By elimination, acute cardiac toxicity appears to be the cause of acute mortality in rats, in which PanLN800(-Forte) was found to be a potent inotrope acting as a cardiac calcium sensitizer.

Conclusion: PanLN800(-Forte) is not a viable fluorescent contrast agent for lymph node imaging in surgery because of cardiac calcium sensitization but may be a novel treatment for heart failure.