The acquisitions of Alexion and Celgene are the latest in a long line of transactions in which big pharma buys big biotech. But these latest two are of biotechs that have disappointed their investors, and there are still some of those left for 2021.

Some analysts are suggesting that AstraZeneca is getting hold of a "scarce and high-quality asset" in Alexion for a very reasonable price and shareholders could demand more than the $175 per share offer on the table.

COVID-19 has introduced new challenges (and more attorneys) into the biopharma deal-making environment, but experts say the fundamentals for deal activity point toward a rebound. Companies that adapt quickly to changes – in communication, due diligence and deal structure – will make successful connections in a time of social distancing.

Alexion is a case study in the travails faced by a biotech with a single blockbuster as it tries to maintain its scale and transform itself into a sustainable business, without blowing billions on bad M&A.