Updated from Jan. 7

The FDA approved American Pharmaceutical Partners' ( APPX) Abraxane to treat metastatic breast cancer, enriching bulls who watched the stock climb by nearly one-third in the past month.

On Monday morning, the stock was up $18.04, or 47%, to $56.75 in premarket trading. The stock, which gained 14% before being halted Friday afternoon, started December at $29.73.

American Pharma had touted Abraxane as an improved version of Bristol Myers Squibb's ( BMY) cancer drug Taxol. The company had claimed Abraxane can be administered faster, at higher doses and with less toxicity.

American Pharma said the move marks the first approval of a so-called protein-bound particle drugs; those drugs are free of toxic solvents.

"Abraxane provides a much-needed new treatment option for women with metastatic breast cancer," said principal clinical trial investigator William J. Gradishar. "The pivotal clinical trial results demonstrated that Abraxane had superior response rate when compared to Taxol in patients with metastatic breast cancer. For the first time we are able to offer patients the full therapeutic benefits of paclitaxel. This makes Abraxane a significant advance in the way we treat breast cancer."

The company said the FDA reviewed a study of 460 patients with metastatic breast cancer that showed Abraxane demonstrated a superior response rate and almost doubled the reconciled target lesion response rate when compared with Taxol.

The approval seemingly ends the longstanding war between the proponents and detractors of the stock. Bulls were convinced the drug was near approval, while bears were expecting the FDA to direct American Pharma to conduct more studies on what would be an entirely new drug-delivery technology.