Regeneron (Nasdaq:REGN), Sanofi-Aventis' (NYSE:SNY) REGN475 Put on Hold by FDA

Citing possible damage to the bones of patients using the drug REGN475, aka SAR164877, the FDA told Regeneron (Nasdaq:REGN) and Sanofi-Aventis (NYSE:SNY) the drug study must be put on hold.

The drug was in the trial stage for the purpose of blocking pain in those suffering from osteoarthritis; it's supposed to be a nerve growth factor inhibitor.

The Food and Drug Administration revealed the decision in a filing with the Securities and Exchange Commission, saying a patient being treated with the drug developed avascular necrosis of a joint. That refers to a the bone collapsing after bone tissue dies.

The FDA made the decision because of their concerns over the possibility the overall class of drugs having the potential to generate the side effect.

Sanofi-Aventis was trading at $32.13, down $0.37, or 1.14 percent, as of 1:38 PM EST. Regeneron Pharmaceuticals was trading at $33.66, up $0.16, or 0.48 percent.