However, the stock pared back much of its gains in the afternoon after France's Ministry of Economy and Finance stated it had not received any request for investment authorization regarding Abivax.
On the Paris stock exchange, around 15:00 GMT, Abivax shares were up 6.9% at 105.8 euros, after having jumped by more than 33% earlier in the session.
According to La Lettre, Eli Lilly is prepared to acquire Abivax for 15 billion euros, confirming rumors already circulating last month regarding the American giant's interest in the French group.
Abivax and Eli Lilly did not immediately respond to a request for comment from Reuters.
A source at Bercy indicated that Paris had not received any request for an IEF procedure, which oversees foreign investment controls in France.
"Bercy has no knowledge of nor contact with Eli Lilly. In the case of strategic pharmaceutical companies, the IEF procedure would be mandatory," the source stated.
The French biotech's stock, with a market capitalization exceeding eight billion euros, had soared by more than 500% on July 23, the date the company announced positive results from a late-stage trial for its lead drug, obefazimod, intended for the treatment of ulcerative colitis.
"Following the positive phase III trial results on ulcerative colitis, Abivax has become a very attractive M&A target," wrote Kepler Cheuvreux in a note.
(Written by Alessandro Parodi in Gdansk with Mathieu Romain in Paris; French version by Claude Chendjou and Blandine Hénault, edited by Sophie Louet)
