655-P: Evaluation of Accuracy and Longevity of an Implantable CGM System through 365 Days

Background: The PROMISE Clinical Trial, conducted to assess safety and accuracy of a 180-day implantable CGM System, had 43 subjects implanted with a modified sensor containing sacrificial boronic acid (SBA) to reduce the degradation of the boronic acid glucose-binding moieties. In-home use to 365 days was monitored in a 30 subject SBA sub-study. Methods: Accuracy of sensor glucose (SG) measurements produced by an algorithm emulator was compared to YSI model 2300 glucose obtained during in-clinic visits to 180 days. The sub-study compared SG to fingerstick blood glucose (BG, CONTOUR Next One BG meter) 4-7 times/day, from days 1-365 or until sensor retirement. SG values were paired within 5 mins after a BG values in the 30 sensors. MARD for 1-180 days was assessed with both YSI and BG reference methods. MARD by glucose ranges were compared for 1-180 days, 181-365 days and 1-365 days using BG as reference. Results: The MARD for SBA sensors for days 1-180 from in-clinic visits was 8.1% with YSI and 9.5% with BG as reference. The Table shows a comparison of MARD values by glucose ranges for the 3 time periods. Conclusions: There was ∼1.4 percentage point increase in overall MARD obtained when BG measurements were used as the reference value rather than YSI. The extension of the PROMISE Clinical Trial in a subset of subjects implanted with SBA sensors suggests accuracy can be maintained and extended to 365 days and across 40-400 mg/dl glucose ranges.