Decision to exercise buy-out option for Perseid follows start of Phase I RA trial in January.

Astellas Pharma has exercised its option to purchase all of Maxygen’s equity interests in the firms’ joint venture protein therapeutics specialist Perseid Therapeutics for $76 million. Astellas already owns 16.7% of Perseid, and its decision to acquire Maxygen’s 83.3% holding in the firm follows the start in January of a Phase I study evaluating Perseid’s CTLA-4-Ig therapeutic (designated ASP2408 by Astellas) for the treatment of rheumatoid arthritis and potentially other autoimmune indications.

The option for Astellas to buy Perseid outright was originally inked as part of Astellas and Maxygen’s 2009 joint venture agreement through which Perseid was established to exploit the majority of Maxygen’s protein pharmaceuticals technology assets and IP. Astellas and Maxygen each put $10 million in cash into the new firm, and Astellas received its 16.7% ownership interest in Perseid.

Perseid’s lead candidate MAXY-4 is a next-generation CTLA4-Ig molecule designed to exhibit an improved therapeutic profile compared with Bristol-Myers Squibb’s Orencia® and belatacept (LEA29Y), Perseid claims. The drug was developed using Perseid’s MolecularBreeding™ directed evolution platform to generate novel CTLA4-Ig proteins with significantly higher specific binding to human B7 ligands.

Perseid already has a global co-development and commercialization collaboration in place with Astellas, through which the firms are developing MAXY-4 for rheumatoid arthritis and other autoimmune diseases. Under terms of the deal Astellas has rights to commercialize MAXY-4 worldwide. Preclinical and clinical development costs relating to autoimmune disease indications in North America and European countries are being shared between the two companies. Astellas is responsible for developing the candidate for autoimmune disease indications in the rest of the world, and will shoulder all costs for developing as well as commercializing MAXY-4 for transplant-rejection indications worldwide.

Start of the Phase I trial with MAXY-4 in January triggered a $10 million milestone payment to Perseid by Astellas.

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