NEW YORK (AP) — Shares of Achillion Pharmaceuticals advanced Monday after the company said a combination of two experimental hepatitis C drugs cured all patients in a small clinical trial.

Achillion said all 12 patients had undetectable virus levels after six weeks of treatment with its two drugs, which are designated ACH-3102 and ACH-3422. The patients had type 1 hepatitis C, the form of the disease that is considered the most common and the hardest to treat, and they had not had any previous treatment.

Shares of Achillion Pharmaceuticals Inc. climbed $1.56, or 11 percent, to $15.77 in morning trading. Earlier the stock rose to $16.74, its highest price in almost eight years.

The drug regimen in the trial did not include interferon or ribavirin, both of which have long been part of standard therapies for hepatitis C. Both can cause unpleasant side effects, and newer hepatitis C treatments can be used without interferon.

The New Haven, Connecticut, company plans to start larger clinical trials of the regimen in 2015. It is also studying several potential treatments for hepatitis C.

Achillion shares have climbed fourfold in value in 2014.