ArmaGen, a private biotech firm, has signed a licensing agreement to fund development of AGT-182, an investigational enzyme to treat degenerative nerve disorder Hunter syndrome. Under the agreement, Calabasas-based ArmaGen will receive payments up to $225 million, including an initial upfront payment of $15 million in cash and equity, from Shire plc, an Irish pharmaceutical company. In exchange, Shire will receive worldwide commercialization rights for AGT-182. The collaboration will be managed by a joint steering committee with representatives from both companies. AGT-182 is ArmaGen’s main investigational drug, and the company plans to start clinical trials before the end of the year. “Shire is the ideal partner for AGT-182, based on the company’s international reach and expertise in serving patients with Hunter syndrome,” James Callaway, chief executive of ArmaGen, said in a statement. Hunter syndrome is a rare, progressive and severe disorder in which the body can’t break down complex sugars. The buildup of these chemicals interferes with the functioning of certain organs, leading to serious complications including developmental delays and mental impairment.