The U.S. Food and Drug Administration on Wednesday cleared Amgen Inc.’s Vectibix as a treatment for advanced colon cancer.

The approval of Amgen’s first cancer drug came a day earlier than company officials had anticipated. It enables the biotech giant to move beyond its current products for the oncology market, which have been limited to targeting cancer treatment side effects such as anemia and infection.

Chief Executive Kevin Sharer earlier estimated that Vectibix sales could reach $2 billion a year despite competition from ImClone Systems Inc.’s Erbitux, which has been available for more than two years.

Vectibix, generically known as panitumumab, is the first of more than half dozen drugs in Amgen’s oncology development pipeline. The drug is expected to be commercially available in early-to-mid October, the company said in a statement, and will be priced at approximately 20 percent less than Erbitux. The FDA approval calls for the drug to be administered intravenously once every two weeks.

The company also announced a financial assistance program for patients who are unable to afford their insurance co-payments. Similar programs are available for the company’s other eight drugs, but have rarely been promoted in conjunction with a drug approval announcement.

Vectibix is expected to have an additional marketing advantage over Erbitux because the generically modified mice used in its development do not leave behind mice proteins that can cause a human immune system reaction. The drug was developed in partnership with Abgenix Inc. until Amgen acquired the smaller Fremont-based company earlier this year.