Updates headline and first paragraph, adds background in paragraphs 7 and 9

March 10 (Reuters) - Beacon Roofing Supply BECN.O is negotiating a potential $11 billion buyout from billionaire Brad Jacobs-run QXO QXO.N, in a complete reversal after it rebuffed an earlier offer and adopted a poison pill to stave off a hostile takeover attempt.

The companies confirmed they are in discussions about a combination in which QXO would acquire Beacon for $124.35 per share in cash. That is an increase of 10 cents from QXO's previous proposal, which Beacon had rejected saying it significantly undervalued the company.

Shares of Beacon rose about 8% to $120 before the bell. The company is postponing its investor day scheduled for March 13.

QXO, a new entrant in the building products distribution industry and which counts U.S. President Donald Trump's son-in-law Jared Kushner as a board member, in January made public its bid to buy Beacon's outstanding shares for $124.25 apiece.

Virginia-based Beacon rejected the offer, which prompted QXO CEO Brad Jacobs to approach Beacon's shareholders directly in a hostile takeover attempt.

Following this, Beacon had asked shareholders to reject QXO's offer. The company said its shareholders were "underwhelmed by the first and only offer".

Jacobs retaliated arguing Beacon's chairman, Stuart Randle, and CEO Julian Francis last year sold about 21% and 10% of their shares, respectively, at lower values than QXO's offer.

Last week, QXO extended the deadline for its $124.25-per-share takeover offer for a second time, which was set to expire on March 10.

It said at the time that about 19.18% of Beacon's outstanding shares were tendered.

QXO proposed 10 independent director nominees to replace Beacon's board of directors after it obtained antitrust clearance in the U.S. and Canada to acquire the roofing material supplier.

(Reporting by Utkarsh Shetti in Bengaluru; Editing by Shilpi Majumdar)

((UtkarshUmesh.Shetti@thomsonreuters.com))