NEW YORK (Reuters) - A new type of cancer drug stopped tumor growth in an early animal study, boosting hopes that the approach may prove promising in humans, according to data released on Sunday.

The treatment, called VX-680 and being developed by Vertex Pharmaceuticals Inc., represents the first drug to stop tumors by targeting enzymes called Aurora kinases.

Research has showed that Aurora kinases play an important role in mitosis, or the process of cell division, which is out of control in cancer patients. Aurora kinases have been identified as overly abundant in certain types of cancer, such as leukemia, colon cancer and breast cancer.

Many proteins are overexpressed in cancer cells, and stopping the overexpression will not necessarily have any impact on halting cancer, as has been observed in many clinical trial failures.

But the Vertex drug showed robust results in mice and rats.

In the animal study, the drug on average showed a 56 percent regression in colon cancer tumors after just 10 days, while in pancreatic cancer, the regression was 22 percent.

"One of the exciting things we have found is that we've tested the compound against a number of different tumor types, including those that are very difficult to treat in man, and we've had success against all of them so far," said Karen Miller, a principal researcher at Vertex and senior author of the study, published in the March issue of Nature Medicine.

A spokesman for Vertex said the company intends to start testing the treatment in humans in early-stage studies before the end of the year.

VX-680 is considered a "small molecule," or a mix of chemicals in a tight bundle, unlike most new cancer drugs, which are "large molecules," or proteins.