The administration of Illinois Gov. Rod Blagojevich said Monday that it would give a $500,000 grant and tax credits worth more than $7.7 million to Japanese drugmaker Astellas Pharma Inc. as part of a deal to keep the company’s North American headquarters in Illinois.In exchange, Astellas will create 75 new positions and retain 350 jobs that had been located in Deerfield, the administration said. Astellas will be formed next year by the acquisition of Fujisawa Pharmaceutical Co. by Yamanouchi Pharmaceutical Co.As a result of the deal, the combined firm is increasing its space by one-third, to 215,000 square feet, in the Parkway North Center in the northern suburb, said Jerry O’Malley, managing director with CarrAmerica Realty Corp., which co-owns the office complex. Real estate firm CB Richard Ellis Inc. represented Astellas.