S and is the most commonlifethreatening genetic disease

There is currently no registered treatment forPKD which affects over 600,000 patients in the U.S and is the most commonlife-threatening genetic disease. This agreement with Plexxikon in PKD is consistent with the overall mission ofRoche to address diseases with significant unmet medical need. "PLX5568 is yet another first-in-class compound from Plexxikon that furtherhighlights our platforms capability to develop highly selective kinaseinhibitors. We hope PLX5568 will significantly delay the loss of kidney functiondue to this debilitating disease, leading to improved quality of life forpatients," stated K. Peter Hirth, Ph.D., chief executive officer of Plexxikon."We are pleased to announce our second collaboration with Roche, building on thefoundation of an excellent and continuing partnership centered on our oncologyprogram and lead product candidate, PLX4032." "We are enthusiastic about collaborating with Plexxikon on this program. Together, wewill advance PLX5568 to help patients suffering from PKD," said Dan Zabrowski,Global Head of Pharma Partnering at Roche.

"Plexxikon has demonstrated excellentcapabilities in discovery and early development necessary to bring forward noveland differentiated product candidates in a variety of indications. Thesecapabilities have driven our interest in a second collaboration with Plexxikon."Terms of Second Roche-Plexxikon CollaborationUnder the terms of the agreement, Roche will have a worldwide, exclusive licenseto develop and commercialize PLX5568, in addition to certain other selective Rafinhibitors resulting from the partnership. Plexxikon could also receive approximately$275 million in payments over the term of the partnership based on thesuccessful completion of a series of milestones for PKD. Separately, Plexxikon willreceive royalties for any sales related to products under the collaboration.Plexxikon retains an option to co-promote PLX5568 or any other product resultingfrom the collaboration for any non-PKD indication in the United States. Plexxikon will be responsible for any discovery and early development throughcompletion of Phase 1 clinical trials, including the completion of the Phase 1clinical trial currently being conducted for PLX5568.

Also under the new agreement, the partners may develop additionalselective Raf inhibitors for other human diseases. Following thesuccessful completion of the Phase 1 trial and chronic toxicology studies, aPhase 2 clinical trial in PKD patients will be initiated in 2009. PLX5568 is a very selective and potent inhibitor of Raf kinase, a criticalmediator of PKD pathology. PLX5568 has demonstrated impressive efficacy inorthologous models of both genetic forms of PKD, resulting in decreased cystsize and improved kidney function. Non-clinical GLP toxicology studies includingdoses up to 2000 mg/kg per day over a period of 28 days have revealed no doselimiting toxicity, confirming the expected safety profile of the drug.