Major US drugmaker Pfizer is collaborating with Sangamo Therapeutics to develop and commercialize gene therapy programs for the rare blood disorder hemophilia A. The agreement includes SB-525, one of Sangamo’s four lead product candidates.

The US Food and Drug Administration has cleared initiation of human clinical trials for SB-525, which has been granted orphan drug status.

Under the terms of the deal, Sangamo will receive an upfront payment of $70 million from Pfizer as well as potential milestone payments of up to $475 million, including up to $300 million for the development and commercialization of SB-525 and up to $175 million for additional candidate drugs developed under the partnership. The California-based biotech will also receive tiered double-digit royalties on net sales.

Sangamo will conduct the SB-525 Phase I/II clinical study and certain manufacturing activities. For its part, Pfizer will be operationally and financially responsible for research, development, manufacturing and commercialization activities for SB-525 and additional products.

“We believe SB-525 has the potential to be a best-in-class therapy that may provide patients with stable and durable levels of Factor VIII protein with a single administration treatment,” said Mikael Dolsten, president of worldwide research and development at Pfizer.

More than 150,000 people worldwide are believed to have the disorder, which is caused by a genetic mutation that results in insufficient activity of Factor VIII, a blood clotting protein.