In May, Biogen (Nasdaq:BIIB) CEO Michel Vounatsos announced his resignation following a precipitous decline in its share price after failing to achieve material sales of its Alzheimer’s drug Aduhelm (aducanumab). Roughly half a year later, Biogen has installed the German-Canadian executive Christopher Viehbacher to lead the company. Viehbacher will assume the role of president, CEO…