Partnership, valued at over $335 million, includes development of other Raf inhibitors.

For $60 million upfront, Plexxikon has granted Roche worldwide, exclusive rights to its Phase I candidate for polycystic kidney disease (PKD), PLX5568. Roche may also license other selective Raf inhibitors resulting from the partnership.

Roche agreed to pay up to $275 million in milestone fees related to PLX5568. Plexxikon could earn additional payments based on the success of other compounds and indications. Separately, Plexxikon will receive royalties on sales of any of these products.

Plexxikon will be responsible for discovery and early development through completion of Phase I trials. Kathy Glaub, president of Plexxikon, hopes to initiate a Phase IIa study by the end of this year.

Preclinical data on PLX5568 has shown positive effects in a variety of pain models, points out Glaub. She believes that this may become another option for Roche to consider.

Plexxikon retains an option to co-promote any product resulting from the collaboration for a non-PKD indication in the U.S.

This is the second agreement between Roche and Plexxikon. The first, an agreement worth over $700 million, was inked in October 2006 and covered the development of a preclinical anticancer agent PLX4032, which selectively inhibits B-RafV600E.

Under the terms of that deal, Plexxikon initially obtained $40 million. Roche agreed to provide $6 million in research funding and $660 million in milestones.

Glaub reports that the collaboration continues to be a success and that the firm has already received some milestones. The most significant will be achieved with the initiation of a registration trial, she adds.

PLX4032 has advanced from the preclinic into later-stage Phase I studies. If data is positive, Glaub plans to begin a Phase II/III registration evaluation later this year.


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