Lantheus (LNTH) - Get Report  , a company that produces diagnostic agents used in medical imaging, reached a deal to acquire oncology medicine developer Progenics Pharmaceuticals (PGNX) - Get Report in an all-stock deal. 

Under the deal, Progenics shareholders will receive 0.2502 a share of Lantheus for each Progenics share they own. The exchange ratio implies a 21.5% premium to Progenics 30-day weighted average closing price.

The two companies had combined pro forma revenue of $370.1 million for the 12 months ended June 30. 

"Lantheus will be a leader in radiopharmaceutical innovation, providing medical professionals with essential tools and therapies to diagnose and treat neuroendocrine tumors and prostate cancer patients," said Lantheus CEO Mary Anne Heino. "Our complementary strengths, radiopharmaceutical manufacturing and supply chain expertise, and focus on commercial execution will deliver sustainable and diversified revenue streams and increase our gross margin potential."

Heino will be the CEO of the combined company, which will trade on the Nasdaq under Lantheus' ticker symbol. 

Lantheus shares fell 20.16% in trading to $19.18, while Progenics slumped 3.2% to $4.79.

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