Horizon Therapeutics Plc, which has a market capitalization of about $18 billion, is in talks with Amgen Inc (AMGN.O), Sanofi (SASY.PA) and Johnson & Johnson (JNJ.N) unit Janssen Global Services over potential takeover offers.
"Any offer for Horizon Therapeutics Plc (HZNP.O), if made, would be in cash, as required by Rule 2.12 of the Takeover Rules," Sanofi said in a statement.
"There is no certainty that any offer will be made, nor as to terms on which any such offer may be made, if forthcoming," it added.
Shares in Sanofi fell after its statement and were down more than 2% at 85.58 euros at 1100 GMT.
Horizon, which makes drugs for rare, autoimmune and severe inflammatory diseases, has said there is no certainty that it will receive a takeover offer.
UBS said in an analyst note that a deal "would be doable and would not screen badly in terms of P&L impact", but it was debatable whether it should be done.
While acquiring Horizon would add a mixed portfolio of specialty drugs to Sanofi's roster, it would not address the French company's need to develop its drug pipeline and improve its productivity from research and development, UBS said.
Sanofi has made several large-scale takeover deals in recent years, and earlier this year it completed the buyout of immuno-oncology company Amunix Pharmaceuticals for around $1 billion.
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