A fluorescent imaging agent called rizedisben showed promise in helping surgeons identify nerve structures during robotic prostate surgery, based on findings from a recent phase 1 clinical trial. At a dose of 3.0 mg/kg, the agent enabled consistent and sustained visualization of the obturator nerve in all patients, with minimal drug-related adverse effects.
The trial enrolled 38 adults with localized prostate cancer scheduled for robot-assisted laparoscopic radical prostatectomy. Conducted at an academic cancer center between January 2023 and October 2024, the study used a dose-escalation design to determine the optimal safe and effective dose of rizedisben. This trial marks the first human evidence that rizedisben can enable real-time intraoperative nerve visualization in minimally invasive procedures.
Rizedisben is a small-molecule fluorophore that binds to myelin and fluoresces under blue light (370–425 nm). It aims to improve real-time identification of nerve structures and reduce the risk of nerve injury during surgery.
Doses ranged from 0.25 mg/kg to 3.0 mg/kg. Patients received the drug intravenously about 30 minutes before nerve visualization. The obturator nerve served as the reference nerve due to its routine exposure and sufficient myelin content.
The main endpoint was sustained fluorescence, defined as moderate or stronger nerve visualization lasting at least 90 minutes. This was measured through intraoperative surgeon scoring and post hoc image analysis.
Sustained fluorescence was observed at 1.0 mg/kg, but only at the 3.0 mg/kg dose did all 9 patients meet the threshold. Fluorescence lasted over 3.5 hours in some cases, with no decline in intensity before surgery ended.
Neurovascular bundle visibility was also evaluated at 3.0 mg/kg. These bundles were visible in 8 of 9 patients Fluorescence was less intense than in obturator nerves, likely due to lower myelin content and smaller size. However, the contrast between nerve and surrounding fat tissue remained consistent, suggesting color differentiation under blue light aided visualization.
Safety was monitored over 45 days. Four patients experienced possibly related adverse events, including a rash and photophobia. All events resolved without long-term effects. No serious cardiac or complications were reported.
The findings support continued research on rizedisben, particularly in surgeries where nerve preservation is critical, noted researchers. Future studies may explore its use in other surgical settings and in combination with tumor-specific imaging agents.
The authors reported no conflicts of interest.
Source: JAMA Surgery