InSite Vision Announces Joint Patent Infringement Lawsuit with Merck & Co., Inc. Against Sandoz, Inc.

ALAMEDA, Calif. – May 26, 2011 – InSite Vision Incorporated (OTCBB: INSV) today announced that it will join Merck (NYSE:MRK), known as MSD outside the United States (U.S.) and Canada, and Pfizer Inc. (NYSE: PFE) in filing a patent infringement lawsuit against Sandoz Inc.

Sandoz recently filed an Abbreviated New Drug Application (ANDA) with the U.S. Food and Drug Administration (FDA) seeking to market a generic version of AzaSite® (azithromycin 1% ophthalmic solution) before expiration of the patents covering AzaSite and its use. AzaSite is marketed by Inspire Pharmaceuticals in the U.S., now a wholly-owned subsidiary of Merck.

The companies have agreed that Merck will take the lead in prosecuting this lawsuit. Each company will be responsible for their own legal costs, with InSite assuming a monitoring role.

Sandoz filed an ANDA application for AzaSite with the FDA of which InSite received notice on April 18, 2011, and InSite has 45 days to file a patent infringement lawsuit. With this filing today, that time requirement has been met. This lawsuit also triggers an automatic stay, or bar, of the FDA’s approval of the ANDA for up to 30 months or until a final court decision of the infringement lawsuit, whichever comes first.

Merck, with the assistance of InSite and Pfizer, will vigorously defend the five U.S. patents related to AzaSite. InSite owns four U.S. patents covering AzaSite and its use, and an exclusive license to a Pfizer-owned azithromycin patent. Under the license agreement between InSite and Inspire, Inspire has the exclusive use of these patents in the U.S. in return for a 25 percent net sales royalty from AzaSite sales. InSite believes that its four patents and the Pfizer patent were properly prosecuted with the U.S. Patent and Trademark Office (USPTO) and are valid, and will provide AzaSite exclusivity until March 2019.

Additionally, InSite recently received a USPTO ruling that the AzaSite patent interference brought by the University of California at San Francisco (UCSF) against InSite patents will proceed to the Priority Phase, or trial phase.

In September 2010, the USPTO heard brief oral arguments where each side presented motions, including motions to dismiss, to be considered by a panel of USPTO judges. In this ruling, the panel of judges decided to see all evidence supporting the inventorship and priority before making a final decision. The USPTO has also determined that all evidence should be submitted, and final oral arguments completed before the end of 2011.

Approximately 90 percent of such cases are decided at the Priority Phase rather than in oral arguments in the Motion Phase. InSite continues to believe that the evidence supporting the inventorship and priority strongly supports the company in this matter, and InSite will continue to vigorously defend its position.

About InSite Vision

InSite Vision is committed to advancing new and superior ophthalmologic products for unmet eye care needs. The company’s product portfolio utilizes InSite Vision’s proven DuraSite® bioadhesive polymer core technology, an innovative platform that extends the duration of drug retention on the surface of the eye, thereby reducing frequency of treatment and improving the efficacy of topically delivered drugs. The DuraSite platform is currently leveraged in two commercial products for the treatment of bacterial eye infections: AzaSite® (azithromycin 1% ophthalmic solution), marketed in the U.S. by Inspire Pharmaceuticals, a wholly-owned subsidiary of Merck; and Besivance™ (besifloxacin 0.6% ophthalmic suspension), marketed by Bausch & Lomb and their partner Pfizer Inc. InSite Vision’s clinical-stage ophthalmic product pipeline includes AzaSite Plus™ (ISV-502) and DexaSite™ (ISV-305) for the treatment of eye infections, ISV-303 for pain and swelling associated with ocular surgery, and ISV-101 for the treatment of dry eye disease. For further information on InSite Vision, please visit www.insitevision.com.

Forward-looking Statements This news release contains certain statements of a forward looking nature relating to future events, including InSite’s planned Phase 3 trials for AzaSite Plus and DexaSite, the design, timing and potential outcome of same, and the expected benefits of the AzaSite Plus and/or DexaSite products. Such statements entail a number of risks and uncertainties, including but not limited to: the results of clinical trials for AzaSite Plus and DexaSite and the timing thereof; InSite’s ability to obtain FDA approval of AzaSite Plus and/or DexaSite and the timing thereof; InSite’s reliance on third parties for the commercialization of its products; the ability of InSite to enter into corporate collaborations for its product candidates; InSite’s ability to expand its product platform to include additional indications; InSite’s ability to compete effectively, either alone or through its partners, with other companies offering competing products or treatments; InSite’s ability to maintain and develop additional collaborations and commercial agreements with corporate partners, including those with respect to AzaSite; its ability to adequately protect its intellectual property and to be free to operate with regard to the intellectual property of others; and determinations by the FDA. Reference is made to the discussion of these and other risk factors detailed in InSite Vision’s filings with the Securities and Exchange Commission, including its annual report on Form 10-K and its quarterly reports on Form 10- Q, under the caption “Risk Factors” and elsewhere in such reports. Any forward-looking statements or projections are based on the limited information currently available to InSite Vision, which is subject to change. Although any such forward-looking statements or projections and the factors influencing them will likely change, InSite Vision undertakes no obligation to update the information. Such information speaks only as of the date of its release. Actual events or results could differ materially and one should not assume that the information provided in this release is still valid at any later date. # # # AzaSite® and DuraSite® are registered trademarks of InSite Vision Incorporated. BESIVANCE™ is a trademark of Bausch & Lomb Incorporated. Contact Information InSite Vision Louis Drapeau, Chief Financial Officer 510.747.1220 mail@insite.com Media/Investor Inquiries BCC Partners Karen L. Bergman 650-575-1509

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