HAYWARD, CA, USA I Apr 29, 2013 I Impax Pharmaceuticals, the brand products division of Impax Laboratories, Inc. (IPXL) today announced that Impax and GlaxoSmithKline (GSK) are terminating their collaboration for the development and commercialization of IPX066 outside the United States (U.S.) and Taiwan. IPX066 (known as RYTARY™ in the U.S.) is an investigational extended-release capsule formulation of carbidopa-levodopa being developed for the symptomatic treatment of adult patients with idiopathic Parkinson’s disease and is not approved anywhere in the world.

Under the terms of the agreement entered into in December 2010, GSK’s right to develop and commercialize IPX066 outside the U.S. and Taiwan will transfer back to Impax effective at the end of July 2013. The decision has been reached because of delays in the anticipated regulatory approval and launch dates in countries in which GSK has rights to commercialize the product.

Impax intends to initiate activities to find a partner or partners for markets outside the U.S. looking to grow their non-US neurology franchise.

About RYTARY (IPX066)

RYTARY is an investigational extended-release capsule formulation of carbidopa-levodopa being developed for the symptomatic treatment of adult patients with idiopathic Parkinson’s disease. It is not approved or licensed anywhere in the world. Results from the phase III studies of RYTARY, APEX-PD (early PD patients), ADVANCE-PD (advanced PD patients) and ASCEND-PD (advanced PD patients) have previously been announced.

About Impax Pharmaceuticals

Impax Pharmaceuticals is the branded products division of Impax Laboratories, Inc. Impax Pharmaceuticals is focused on targeting significant unmet needs, with a primary focus on developing treatments for central nervous system disorders. For more information, please visit its Web site at: www.impaxpharma.com.

About Impax Laboratories, Inc.

Impax Laboratories, Inc. (Impax) is a technology based specialty pharmaceutical company applying its formulation expertise and drug delivery technology to the development of controlled-release and specialty generics in addition to the development of central nervous system disorder branded products. Impax markets its generic products through its Global Pharmaceuticals division and markets its branded products through the Impax Pharmaceuticals division. Additionally, where strategically appropriate, Impax develops marketing partnerships to fully leverage its technology platform and pursues partnership opportunities that offer alternative dosage form technologies, such as injectables, nasal sprays, inhalers, patches, creams and ointments. For more information, please visit the Company’s Web site at: www.impaxlabs.com.

SOURCE: Impax Laboratories