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Editors Selection IGR 16-4

Medical Treatment: Bimatoprost Implant and Circadian IOP

Comment by Kaweh Mansouri on:

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This is the first study evaluating the 24-h IOP-lowering effects of 10-ug injectable bimatoprost implant ('Durysta'), which was approved for a one-time use by the FDA in 2020. The study evaluated 24-h IOP by measuring habitual position IOP (e.g., sitting during daytime and supine at nighttime) using Goldmann applanation tonometry and the pneumatonometer at week eight after administration, when they were housed in a sleep lab. Efficacy and safety were also evaluated at 12 months. Thirty-one participants with POAG and OHT were included in this trial. There was a control group of patients (n = 6) who received once-daily bimatoprost 0.1%.

Sleep lab measurements showed that IOP was consistently lowered at week eight both at day and nighttime: The mean hour-matched, habitual position, IOP change from baseline over 24 hours by pneumatonometry ranged from -3.7 to -1.7 mmHg; the range was -3.7 to -1.8 mmHg across diurnal and -2.4 to -1.7 mmHg across nocturnal timepoints. In the reference group, the habitual position IOP change from baseline over 24 hours ranged from -5.0 to -1.8 mmHg.

Fluctuation in habitual position IOP over 24 hours was reduced after bimatoprost implant administration. The mean range in IOP over 24 hours, measured in habitual position by pneumatonometry, was 9.9 mmHg at baseline and 8.3 mmHg at week eight, and the mean change from baseline in IOP range at week eight was -1.6 mmHg. This reduction in 24-hour habitual position IOP fluctuation occurred primarily because of a reduction in diurnal IOP fluctuation. In contrast, for the reference group, the mean (SD) change from baseline in range of habitual position over 24 hours at the week eight sleep lab visit was +0.7 (3.90) mmHg.

The mean habitual position IOP reduction was 2.6 mmHg during the diurnal period and 2.1 mmHg during the nocturnal period. In fact, the bimatoprost implant provided a more sustained IOP-lowering effect over 24 hours than topical bimatoprost 0.01%.

The percentage of participants in the bimatoprost implant group requiring no additional (rescue) IOP-lowering treatment in the study eye was 100% (31/31) at week 8 and remained high (74.2%, 23/31) at month 12. Therefore, ¾ of patients remained controlled at one year with a single administration.

The device was shown to be safe and generally well tolerated: the most common adverse event was conjunctival hyperemia (35.5%). There were no safety concerns in respect to endothelial cell loss (ECL), with a mean loss of 2% at one year and no subject experiencing a ≥ 15% (ECL). At one year, 68% of implants were no longer visible on gonioscopy or were estimated to be < 25% of their original size.

Its results provide important insights into the potential of the bimatoprost implant, which I see as mostly two-fold compared to topical prostaglandin analogues: Firstly, adherence issues are bypassed through the single injection and tolerability seems to be better for patients. Secondly, it is possible that the stronger observed reduction in IOP fluctuations provide improved glaucoma control

This is an interesting study and the authors are to be commended for having conducted what was a challenging design. Its results provide important insights into the potential of the bimatoprost implant, which I see as mostly two-fold compared to topical prostaglandin analogues: Firstly, adherence issues are bypassed through the single injection and tolerability seems to be better for patients. Secondly, it is possible that the stronger observed reduction in IOP fluctuations provide improved glaucoma control. On the other hand, the issue of ECL with repeated administration is somewhat a concern and more studies are needed to provide assurances on long-term corneal safety.

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