Nippon Shinyaku will pay Regenxbio $110 million upfront for U.S. and Asia rights to treatments for Hunter and Hurler syndromes.

Regenxbio, a prolific developer of gene therapy technology, will hand Japan’s Nippon Shinyaku certain rights to two experimental treatments in a deal that will earn it at least $110 million.

Nippon Shinyaku will pay that much upfront to Regenxbio, while promising to pay up to $700 million more in milestone fees that are mostly tied to future sales. In return, Nippon Shinyaku has rights to commercialize both treatments in the U.S. and across Asia.

One of the treatments, for a progressive disorder known as Hunter syndrome, could secure approval in the U.S. as soon as late this year. Should that happen, Regenxbio will retain rights to any priority review voucher, a kind of regulatory fast pass, that the Food and Drug Administration might issue as a result.

Regenxbio is a frequent collaborator in gene therapy, having previously licensed its technology to companies like Eli Lilly, Novartis and Astellas.

The deal with Nippon Shinyaku announced Tuesday will hand over partial responsibility to Regenxbio’s most advanced wholly owned therapy, RGX-121. The company is submitting the Hunter syndrome treatment for U.S. approval on a rolling basis, a process it expects to complete this quarter.

An approval would make RGX-121 the first gene therapy for Hunter syndrome, which is progressive and causes a range of symptoms across the body. Regenxbio has tested it in a multi-phase trial that measured RGX-121’s effects on a biomarker associated with brain disease activity.

Approval could hand the company a valuable priority review voucher, which companies can sell for prices that regularly reach $100 million. Under the deal with Nippon Shinyaku, Regenxbio retains rights to the voucher, if issued, and 100% of proceeds related to its sale.

The other treatment, RGX-111, treats another type of mucopolysaccharidosis called Hurler syndrome. It’s earlier in clinical testing.

Regenxbio will lead future clinical development of both RGX-121 and RGX-111, and under the deal is responsible for manufacturing both products for Nippon Shinyaku. It still holds rights to sell either in countries outside of the U.S. and Asia.

The deal is Regenxbio’s first since long-time CEO Kenneth Mills stepped down and was replaced by current chief Curran Simpson on July 1.