Scientists advising the Food and Drug Administration said anemia drugs sold by Amgen and Johnson & Johnson should be allowed to stay on the market for chemotherapy patients.
The recommendation was made despite concerns that the drugs may heighten the risk of death and tumor growth.
Shares of Amgen rose almost 5 percent Thursday, while Johnson & Johnson stock got a 0.42 percent boost.
The cancer experts voted 13 to one in favor of maintaining the drugs' approval for chemotherapy patients.
FDA often follows its panelists advice, though it is not required to do so.
Wall Street was concerned the panel could have recommended halting use of the drugs in all chemotherapy patients. Anemia drugs accounted for $6.2 billion, or more than 40 percent, of Amgen's revenue last year. J&J's Procrit had sales of $2.9 billion, or less than 5 percent of total sales.
Panelists were scheduled to vote on more moderate restrictions on the drugs, such as limiting use in some type of cancer.
Regulators bolstered warning labels on the treatments — Aranesp, Epogen and Procrit — three times in the past year. Amgen manufactures all three drugs, though New Brunswick, N.J.-based Johnson & Johnson sells Procrit.