Plexxikon acquired by Daiichi Sankyo


On March 1, 2011, Plexxikon, Inc. (Berkeley, CA) announced that it has agreed to be acquired by Daiichi Sankyo, Japan’s third-largest pharmaceutical company, via an all-cash purchase. Under the merger agreement, Daiichi will pay $805 million up-front to purchase Plexxikon. Near-term milestone payments associated with the approval of Plexxikon’s lead drug candidate PLX4032 could total an additional $130 million.

The main driver for the merger is Plexxikon’s lead drug, PLX4032, for the treatment of metastatic melanoma. Plexxikon and its development and commercialization partner Roche/Genentech expect to file for U.S. and European approval of PLX4032 this year; the drug is expected to reach the market in 2012. By acquiring Plexxikon, Daiichi will gain the right to co-promote the drug in the U.S. with Genentech. PLX4032 is a novel oral drug that specifically targets B-Raf kinase carrying the V600E mutation, which is present in the majority of human melanomas.

We have been covering the development of PLX4032 on the Biopharmconsortium Blog. Our most recent article, “Phase 3 trial of targeted anticancer drug PLX4032/RG7204 shows overall survival benefit in melanoma patients”, was posted on January 23, 2011. That article, which discusses the successful Phase 3 trial of PLX4032 (which Roche has designated as RG7204), includes a list of links to our earlier articles. The Phase 3 trial showed that treatment with PLX4032 gave enhanced overall survival as compared with dacarbazine (the standard of care) in previously untreated metastatic melanoma patients carrying the B-Raf(V600E) mutation. Although previous studies showed tumor shrinkage and enhanced progression-free survival (by approximately seven months) in the majority of PLX4032-treated patients as compared to dacarbazine, this is the first report that PLX4032 give enhanced overall survival.

PLX4032 is a personalized medicine, which Plexxikon has planned to pair with a companion diagnostic, developed in partnership with Roche Molecular Diagnostics. The DNA-based companion diagnostic will identify patients whose tumors carry B-Raf(V600E). The companies plan to launch PLX4032 together with the companion diagnostic, so that oncologists can readily identify patients who would benefit from treatment with the drug.

In acquiring Plexxikon, Daiichi also gains a pipeline that includes the kinase inhibitor PLX3397, which is in Phase 1 safety studies, with Phase 2 studies planned in metastatic breast cancer, and PLX-204, an oral PPAR alpha, gamma, and delta partial agonist that is In Phase 2 clinical trials in type 2 diabetes.

Daiichi will also gain Plexxikon’s drug discovery and development technology and strategy. We discussed how Plexxikon used its proprietary scaffold-based drug design technology platform to discover PLX4032, in our March 10, 2010 article on this blog. Daiichi says that it plans to “provide a high degree of independence to the Plexxikon group to support their continuing success,” and to leverage Plexxikon’s technology platform to discover and develop newer drug candidates.

Daiichi’s purchase of Plexxikon is part of a recent trend, in which the leading Japanese pharmaceutical companies have been investing in  oncology R&D in the United States. Two of these investments were large acquisitions. In 2008, Takeda acquired Millennium Pharmaceuticals (Cambridge, MA) for $8.8 billion; Takeda operates its acquisition, renamed Millennium: The Takeda Oncology Company, as a wholly-owned subsidiary. Astellas acquired OSI (Melville, NY) for $4 billion in 2010; OSI also operates as a wholly-owned subsidiary.  Both of the acquired companies boast large-selling drugs–Millennium’s Velcade (bortezomib) and OSI’s Tarceva (erlotinib) (which is partnered with Genentech/Roche).

The Japanese pharmaceutical companies aim to utilize U.S. innovation to compete in the lucrative global oncology market, which analysts project will expand 12 to 15 percent per year, reaching as much as $80 billion by 2012. In contrast, annual sales growth for Japanese pharmaceutical companies is projected to average 1.4 percent from 2009 to 2015. Overseas investments by Japanese companies are also being driven by a strong yen; the yen gained 8 percent gain over the dollar during the past year.

Some analysts believe that Daiichi paid too much for Plexxikon, and that even with the Plexxikon acquisition, Daiichi will not be very competitive in oncology with Takeda and Astellas, each of which acquired much larger U.S. oncology companies. Moreover, Daiichi has other issues to deal with, such as slow sales for its oral antiplatelet agent Effient (Prasugrel) (codeveloped with Lilly, and approved in 2009), which Daiichi hoped would be a blockbuster drug. Moreover, Daiichi’s majority-owned Indian generic drug company Ranbaxy has experienced a fourth-quarter loss due to rising operating expenses.

In addition to its acquisition of Plexxikon, Daiichi is also codeveloping (with ArQule, of Woburn MA) ARQ 197, a c-Met kinase inhbitor; this compound is in Phase 3 clinical trials in non-small cell lung cancer (NSCLC). Daiichi also acquired German oncology firm U3 Pharma (Martinsried, Germany) for $235 million in 2008. U3 Pharma (which operates as a wholly-owned subsidiary of Daiichi) is developing MAb-based anticancer therapies. Daiichi also, in 2007, licensed Japanese development and commercialization rights to Amgen’s MAb drug denosumab. Denosumab, marketed as Xgeva, was approved in the U.S. in 2010 for prevention of skeletal-related events in patients with bone metastases of solid tumors.

Will the acquisition of Plexxikon help Daiichi to compete in the worldwide oncology market, with its Japanese rivals and with other pharmaceutical companies? Only time will tell. PLX4032 is an exciting, breakthrough medicine that is likely to be approved in 2012. Moreover, if Daiichi allows Plexxikon the freedom to innovate and invests in its R&D activity, and if it can also harness Plexxikon’s technology platform to discover and develop novel drugs across different therapeutic areas, the Plexxikon acquisition may prove to be a major competitive advantage despite its small size.


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