Astellas has signed a major deal with the US biotechnology company which will give the Japanese drugmaker rights to drug candidates for autoimmune diseases and transplant rejection.

Under the terms of the agreement, Maxygen will receive an initial sum of $10 million and is eligible to receive up to an additional $160 million in pre-launch milestone payments. The company can also get tiered double-digit royalties on all sales.

The deal centres around Maxygen’s preclinical MAXY-4 programme which is looking to create a next-generation CTLA4-Ig protein for rheumatoid arthritis, transplant rejection and other autoimmune indications. They will co-develop MAXY-4 candidates for RA and other autoimmune diseases and Astellas will exclusively develop them for transplant rejection.

In addition, Maxygen has an option to co-promote any autoimmune therapeutic products developed under this alliance in North America. Regardless of indication, Astellas will manufacture the finished product using active drug substance provided by Maxygen and market and sell it globally.

Hirofumi Onosaka, Astellas’s senior corporate executive, said that Maxygen has “a very strong suite of technologies to develop improved versions of protein drugs”. He added that the Tokyo-based firm is committed to “solidifying immunology as one of our prioritised therapeutic areas, and this partnership should become a driving force to enhance our leadership position in the transplantation franchise”.

Astellas’ lead product is the immunosuppressant Prograf (tacrolimus), which is still selling well despite recently losing patent protection in the USA.