Novartis laid out $16 billion for GlaxoSmithKline’s oncology portfolio in 2015 and has spent much of the last four years laboring to make a success of one of the drugs it picked up, Arzerra. It hasn’t had much luck in chronic lymphocytic leukemia (CLL), but it’s hoping fresh phase 3 data will help it forge a new market for the drug: multiple sclerosis.

Friday, Novartis said Arzerra (ofatumumab) had shown it was superior to Sanofi’s MS drug Aubagio in two phase 3 studies in adults with relapsing forms of the disease. The trials included 1,882 patients who either received a monthly injection of Arzerra or once-daily Aubagio pills. Arzerra reduced the rate of relapses, Novartis said.

The company plans to release full data at an MS conference in mid-September and to begin the approval process for Arzerra in MS with regulatory agencies by the end of this year. The drug will carry a different brand name if it is approved in MS.

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If Novartis succeeds with Arzerra in MS, it will be a notable turnaround for a troubled drug. Arzerra was never really a contender in CLL, because shortly after Novartis acquired it from GSK, the drug started to face competition from Johnson & Johnson and AbbVie’s Imbruvica. Arzerra floundered while Imbruvica grew into a $4 billion-a-year hit.

In January 2018, Novartis and partner Genmab stopped marketing Arzerra outside the U.S., citing a lack of market traction due to competition. It didn’t help that J&J and AbbVie ran head-to-head trials showing Imbruvica outperformed Arzerra in CLL in both response rate and survival.

But Novartis always held out hope for Arzerra in MS. A few months after it struck the GSK oncology deal, it paid another $1 billion for full control of the drug in MS. It was viewed as a smart bet at the time, because Novartis’ MS pill Gilenya—the company's best-seller at $3.3 billion a year—was expected to face generic competitors as soon as this year.

Novartis has so far managed to delay those generic rivals to Gilenya, though. In June, a U.S. district judge in Delaware granted a temporary injunction that prevented several generic drugmakers from launching their low-cost versions of the med. The judge cited ongoing patent litigation in federal court.

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Luckily, though, Novartis isn’t placing all its MS hopes on Gilenya and Arzerra. In March, the FDA approved Novartis’ Mayzent, the first oral drug for patients with secondary progressive multiple sclerosis. Even though the company will face challenges in educating physicians about how to recognize that particular form of the disease, analysts expect that sales of the drug will ultimately reach blockbuster territory.

Arzerra works against MS by binding to CD20 on the surface of B cells and depleting the cells, which are a major culprit in the disease. The company started the phase 3 trials of the drug in MS in August 2016.