Human Genome Sciences Inc. said the Food and Drug Administration likely won't approve its effort to sell a hepatitis C drug in a dose that is taken every two weeks, expressing concern about the "risk benefit."

The move comes two months after Novartis AG, Human Genome's partner on the drug, pulled its application for European approval after regulators there indicated that additional data would be needed and couldn't be generated within the review's time frame. European officials at the time also raised concern about whether the drug's help "is sufficient relative to risk."

Human Genome said Monday that in a preliminary review letter, the FDA gave its feedback on the 900-microgram dose of Zalbin, known in Europe as Joulferon, given every two weeks. While the review is still ongoing, Human Genome "has concluded that licensure of this dosing regimen is unlikely."

The drug, which is also being studied at dosing every four weeks, treats people with genotypes 2 and 3 hepatitis C, an inflammation of the liver. Genotypes 2 and 3 of the virus are generally easier to treat than genotype 1, the most common one in the U.S.

Human Genome and Novartis agreed in 2006 to jointly sell the drug, with the two splitting U.S. profits and Novartis paying Human Genome a royalty on international sales. As of March, Human Genome received $207.5 million in milestone payments so far, and up to another $300 million is possible.