Achillion Pharmaceuticals Inc., a Connecticut drug company whose CEO moved his office and 30 jobs to Blue Bell last winter, has been purchased by Alexion Pharmaceuticals Inc. of Boston for $930 million, or $6.30 a share, pending approval by Achillion shareholders and regulators.

Plus, Achillion shareholders will get an extra dollar a share if the FDA approves Achillion’s Danicopan (for a rare blood disease) and another dollar if a drug in development called ACH-5228 starts Phase 3 clinical trials by target dates.

Because the deal won’t close before 2020, the companies will continue to operate separately for now, said Alexion spokeswoman Megan Goulart.

The news drove Achillion shares up 72 percent, to $6.28, though that’s still less than half the company’s value soon after its 2007 initial public stock offering (IPO) or its 2015 high.

Buyer Alexion’s shares fell 5 percent to $99.51. The company, with sales of more than $4 billion last year, is modestly profitable.

Alexion develops complement inhibitors, which protect cells from damage due to disease. Achillion targets an “alternative pathway” to Alexion’s current products, said Alexion chief executive Ludwig Hantson in a statement. “We believe this approach has the opportunity to help patients with diseases not currently addressed” by products on the market, he added.

Achillion “has established great momentum,” and its position as “an established leader” in the field will speed therapies to market, said Achillion chief executive Joe Truitt. Alexion did not immediately respond to requests for comment on the deal’s impact on staff in Blue Bell or Connecticut. The deal must still be approved by Achillion shareholders.

The sale price is a big jump on the $350 million Achillion was worth when Truitt relocated from New Haven to offices at 1777 Sentry Parkway West, Blue Bell, earlier this year. He said he made the move because he found it easier to recruit pharma business people around Philadelphia than in New England.

The company’s assets include $230 million in cash on its books. With no approved drugs to sell, Achillion has burned through an average of more than $6 million of investor capital each month over the last four years as it has labored to bring its treatments to market.

Achillion is developing therapies for what are known as orphan diseases, serious conditions that affect a few thousand Americans. Under U.S. drug law, the company can speed such drugs to market, and hope for fat profit margins.

Its recent focus has been on “alternative pathways" for factor D, an immune system enzyme whose maladjustment is associated with lethal kidney and blood diseases.