Non-obligatory role of prostaglandin D2 receptor subtype 1 in rosacea: laropiprant in comparison to a placebo did not alleviate the symptoms of erythematoelangiectaic rosacea

Erythematotelangiectatic rosacea shares facial flushing features with those seen after niacin. This study was performed to test the hypothesis whether prostaglandin D2 (PGD2) receptor subtype 1 antagonist (laropiprant) will improve the symptoms of rosacea. The purpose of this study was to evaluate the effect of laropiprant 100 mg administered once daily for 4 weeks on the signs and symptoms of erythematotelangiectatic rosacea. Subjects received laropiprant 100 mg once-daily (n = 30) or placebo (n = 30) for 4 weeks. The primary pharmacodynamics endpoint was change in Clinician's Erythema Assessment (CEA) score from baseline to week 4. The patient self-assessment (PSA) was a secondary endpoint. Laropiprant was generally well tolerated in this study for the primary endpoint of change in CEA score from Baseline to Week 4, the least-squares mean of change from baseline to visit 4/week 4 was -3.7 and -3.4 for placebo and laropiprant (100 mg), respectively. The least-squares mean difference (placebo minus laropiprant) with 90% confidence interval of change in CEA score from baseline to visit 4/week 4 was estimated as -0.3 (-1.6, 1.0). For the secondary endpoint, the least-squares mean difference (placebo minus laropiprant) with 90% confidence interval of change from baseline to visit 4/week 4 was estimated as -0.7 (-7.7, 6.4) for PSA total score, -4.5 (-14.2, 5.3) for PSA emotion score, -1.3 (-7.8, 5.3) for PSA symptoms score, and 3.6 (-4.3, 11.4) for PSA functioning score. Laropiprant administered once daily for 4 weeks was generally well tolerated in this population of subjects with rosacea. However, there were no clinically meaningful changes in the primary endpoint of CEA given that the response to laropiprant could not be differentiated from that to placebo. There was also no clinically meaningful change in the secondary endpoint, PSA. A DP1 antagonist is not likely to be effective in rosacea.