The objective of this study is to compare the safety and efficacy of BRM421 OS to vehicle for the treatment of the signs and symptoms of dry eye disease.

Inclusion Criteria:

• Be at least 18 years of age;
• Provide written informed consent;
• Have a reported history of dry eye prior to enrollment;
• Have a history of use or desire to use eye drops;

Exclusion Criteria:

• Have any clinically significant slit lamp findings at Visit 1 that may include active blepharitis, meibomian gland dysfunction (MGD), lid margin inflammation or active ocular allergies that require therapeutic treatment, and/or in the opinion of the investigator may interfere with study parameters;
• Be diagnosed with an ongoing ocular infection (bacterial, viral, or fungal), or active ocular inflammation at Visit 1;
• Have worn contact lenses within 7 days of Visit 1 or anticipate using contact lenses during the study;
• Have used any eye drops within 2 hours of Visit 1;
• Have previously had laser-assisted in situ keratomileusis (LASIK) surgery within the last 12 months;
• Be a woman of childbearing potential who is not using an acceptable means of birth control;