AstraZeneca will take full control of Caelum Biosciences in a deal worth up to $500 million, the drugmaker said on Wednesday, sharpening its focus on rare-disease drugs following its purchase of Alexion Pharmaceuticals. The deal gives AstraZeneca access to another potentially lucrative rare disease drug that is undergoing late-stage trials and has a “fast track” status for regulatory review in the United States. New Jersey-based Caelum will become part of AstraZeneca’s Alexion division, the rare diseases specialist it bought for $39 billion earlier this year. Alexion will pay $150 million to buy the remaining stake it does not already own in Caelum and make future payments of up to $350 million, depending on milestones achieved. Alexion took a minority stake in Caelum in 2019. Caelum’s drug candidate aims to treat AL amyloidosis, a rare, life-threatening disease that damages the heart and kidneys and affects an estimated 20,000 people across six …