Dec 12 (Reuters) - Pfizer said on Tuesday it has agreed to donate the rights of royalties from sales of cancer drug Bavencio to address concerns from U.S. antitrust regulators related to its $43-billion deal to buy Seagen.

Pfizer said it had now received all regulatory approvals to close the deal on Thursday.

The drugmaker in March agreed to buy Seagen and its targeted cancer therapies as it braces for a steep fall in COVID-related sales and generic competition for some top-selling drugs.

However, the U.S. Federal Trade Commission sent a request for more information on the deal to the companies in July.

Washington-based Seagen is a pioneer of antibody-drug conjugates, which work like "guided missiles" designed to destroy cancer while sparing healthy cells. (Reporting by Manas Mishra in Bengaluru; Editing by Shounak Dasgupta)