Achillion Pharmaceuticals Inc said its experimental hepatitis C drug, when used in combination with Gilead Sciences Inc’s Sovaldi, eradicated signs of the virus after six weeks of therapy, sending its shares up before the opening bell.

If the combination of Sovaldi and Achillion’s ACH-3102 continues to show this level of effectiveness, the treatment could eventually rival offerings from Gilead and AbbVie Inc to fight the liver-destroying virus.

Gilead’s new-generation hepatitis C treatment, Harvoni, which combines Sovaldi with the company’s own NS5A inhibitor, achieves this response after eight weeks of therapy. Sales of Harvoni totaled $2.11 billion in the quarter ended Dec. 31.

AbbVie’s regimen, Viekira Pak, which won U.S. approval in December, takes 12 weeks to achieve a cure.

Shares of Achillion, one of the few companies developing hepatitis C therapies independently, rose about 10 percent in premarket trading on Monday.

The main goal of Achillion’s ongoing mid-stage study is to achieve a sustained virological response 12 weeks after therapy, which would constitute a cure.

The study is testing a 50 milligram (mg) dose of Achillion’s NS5A inhibitor in combination with 400 mg of Gilead’s sofosbuvir in previously untreated genotype 1 hepatitis C patients.

The market for hepatitis C drugs has developed at a lightening pace in recent years, with several companies working on producing newer drugs to cure the disease, which affects about 150 million globally.

Achillion’s data represents the shortest duration and highest response achieved to date with any two-drug, direct-acting antiviral regimen for hep C, Chief Executive Milind Deshpande said in a statement.

“We will now be evaluating four- and six-week treatment durations that leverage all of our (hepatitis C) assets including ACH-3102, ACH-3422 and sovaprevir,” he said.

Achillion shares closed at $10.82 on the Nasdaq on Friday.

Gilead’s stock was down about 0.5 percent at $96.98 premarket.