Shares of the Foster City, Calif.-based biopharma were up $1.92 or $61.79 at last check.
The two companies announced the acquisition last month in which Gilead agreed to pay $88 a share for Immunomedics. Gilead completed the tender offer for all outstanding shares of Immunomedics' shares on Friday.
With the completion of the merger, the Morristown, New Jersey-based Immunomedics becomes a wholly owned subsidiary of Gilead and its stock will no longer be listed on the Nasdaq.
Gilead said the purchase, which it will finance with a mixture of cash and debt, will give it access to Immunomedics' breast cancer treatment Trodelvy, which received approval from the Food and Drug Administration last spring.
"There is a lot of important work ahead of us to deliver on the vast potential that Trodelvy offers for patients with cancer," Daniel O’Day, Gilead Sciences' chairman and CEO, said in a statement. ""Together we will bring Trodelvy to many more patients around the world with triple-negative breast cancer and continue to explore its potential in many other types of cancer, both as a monotherapy and in combination with other treatments."
Gilead and Immunomedics said the deal was unanimously approved by both company's boards and is expected to close in the fourth quarter.
This was Gilead's second major announcement in less than 24 hours. On Thursday, the FDA cleared the drugmaker's antiviral remdesivir to treat coronavirus patients who require hospitalization.