Evaluation of Trans-Sodium Crocetinate (TSC) on Peripheral Oxygenation in Healthy Individuals Using Transcutaneous Oximetry

Introduction Trans sodium crocetinate (TSC) is a synthetic carotenoid with a unique mechanism of action that improves the diffusion of oxygen by reducing oxygen transfer resistance within plasma, and it is currently being developed to enhance oxygen delivery to hypoxic tissues in multiple conditions. The goals of this study were to evaluate safety, pharmacokinetics, and pharmacodynamic properties of escalating doses of TSC on peripheral oxygenation utilizing transcutaneous oxygen measurements, when administered to healthy subjects breathing supplemental oxygen. Methods This was a dose-escalation, single-center, randomized, phase 1 study aimed at assessing the safety, pharmacokinetic and pharmacodynamic properties of TSC at doses of 0.5, 1.0, 1.5, 2.0, or 2.5 mg/kg as an intravenous bolus. Thirty healthy adult subjects of 18 to 55 years of age were enrolled and allocated to one of the five dose groups or placebo. Venous blood samples were collected for pharmacokinetic evaluations of TSC at 1, 10, 30 minutes, and 1.5 hours after the start of injection of the study drug. Pharmacodynamic assessment of tissue oxygenation was performed while the subjects breathed supplemental oxygen at 6 L/minute for 70 minutes prior to study drug administration: the first 10 minutes was to allow for equilibration, and the subsequent 60 minutes served as a baseline period (Period 1), followed by a time-matched 60-minute intervention period (Period 2). Tissue oxygenation readings were obtained by transcutaneous oximetry (TcpO2) measurement using four TcpO2 sensors placed on the lower limbs of subjects lying in a supine or semi-recumbent position. TcpO2 values were recorded over a 2-hour time period: 60 minutes prior to study drug administration (Period 1) and 60 minutes post administration of the study drug (Period 2). Results TSC was safe and well tolerated at all doses tested. The pharmacokinetic analyses demonstrated that clearance decreased at escalating doses of TSC. The results of the primary pharmacodynamic analysis revealed high levels of variability in the 60-minute baseline TcpO2 levels, however despite such variability, time-matched TcpO2 measurements demonstrated observed increases in median TcpO2 values in subjects who received TSC, relative to those who received a placebo. The high variability observed across the four sensors suggested that the data could not be pooled across all four sensors, therefore, additional supplemental analyses were performed. The results of the supplemental analyses indicated that the TcpO2 intra-subject slopes of the TSC treatment groups were consistently positive during the study intervention period, and therefore suggestive of an increase in TcpO2 levels. This was not observed in the placebo group. Based on this analysis, all TSC dose groups had a greater increase in TcpO2 levels than the placebo group, with the 2.5 mg/kg dose demonstrating the most notable increase over the 1-hour intervention period (Period 2). Conclusions TSC administered as a single IV bolus dose ranging from 0.5 mg/kg to 2.5 mg/kg to healthy subjects breathing supplemental oxygen, was safe and well tolerated. Pharmacokinetic assessments demonstrated that TSC plasma concentrations increased with escalating dose and that increasing TSC dose was associated with a decrease in clearance. The high levels of variability in TcpO2 levels did not allow for pooling of sensor measurements for primary analysis; however, supplemental analysis of individual sensor measurements demonstrated an observed dose effect of TSC on peripheral tissue oxygenation relative to placebo.