Report on study behind Merck's suspension of trial:
8/1/08 Diabetes Rep. (Pg. Unavail. Online)
2008 WLNR 14362676
Diabetes ReportCopyright 2008 Espicom Business Intelligence
August 1, 2008
Corticosteroid less effective than laser therapy for treating DMO
A study conducted by the National Eye Institute's (NEI) Diabetic Retinopathy Clinical Research Network has found that triamcinolone, a potential new corticosteroid therapy for the treatment of diabetic macular oedema (DMO), proved less effective than traditional laser treatment, and that the latter method has fewer side effects in the long-term treatment of DMO.
This was the first study to compare the long-term benefits of both treatments and evaluate their potential side effects. While triamcinolone was used in this trial, there is no scientific rationale at this time suggesting that one corticosteroid preparation should be substantially different from another. According to Dr Paul A Sieving, Director of the NEI, the results of this study, which were published in the 26th July online issue of Ophthalmology (10.1016/j.ophtha.2008.06.015), should confirm the use of laser treatment for DMO.
The investigation, which was conducted at 88 sites across the US, included 840 study eyes of 693 subjects with DMO involving the fovea and with visual acuity (VA) of 20/40 to 20/320. Patients were randomly assigned to triamcinolone 1 (n=256) or 4mg (n=254), or traditional focal/grid photocoagulation (n=330). Following treatment, investigators tested each patient to determine whether the procedure had prevented substantial vision loss (defined as reading at least two less lines on a standard eye chart two years after entering the study). Retreatment was given for persistent or new oedema at four-month intervals and the primary outcome was evaluated at two years.
At four months, mean VA was better in the triamcinolone 4mg group than in either the laser (p<0.001) or triamcinolone 1mg groups (p=0.001). By one year, there were no significant differences among groups in mean VA. By the 16-month visit and extending through the primary outcome visit at two years, mean VA was better in the laser group than in either triamcinolone group (at two years, p=0.02 for laser vs triamcinolone 1mg; p=0.002 for laser vs triamcinolone 4mg; and p=0.49 for triamcinolone 1 vs 4mg). Treatment group differences in the VA outcome could not be attributed solely to cataract formation.
Optical coherence tomography results generally paralleled the VA results. Intraocular pressure increased from baseline by 10mmHg or more at any visit in 4, 16 and 33 per cent of eyes in the laser, triamcinolone 1 and 4mg groups, respectively, and cataract surgery was performed in 13, 23, and 51 per cent of eyes in the three groups, respectively.
The researchers found that, while not as effective as the laser treatment, triamcinolone treatment did provide some benefit. Notably, laser treatment had previously been perceived to prevent further vision loss, but not to improve vision. Improvements in vision were not found in the only prior study evaluating laser treatment for DMO because most subjects enrolled in that trial already had good-to-excellent visual acuity and therefore, no room to improve. The current findings raise the possibility that combining laser treatment with corticosteroids might produce greater benefit. The Diabetic Retinopathy Clinical Research Network is currently conducting a study that is comparing a combination of corticosteroids and laser to laser alone.
Editor's note: under a joint development and commercialisation agreement, Merck & Co and SurModics are currently developing the latter's I-vation intravitreal implant system to deliver triamcinolone acetonide in a sustained-release fashion for the treatment of DMO. The product is currently in a Phase IIb trial in patients with the disorder.
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