TG Therapeutics Inc said a combination of its experimental cancer drug, ublituximab, and approved treatment Imbruvica was found to be more effective in high-risk leukemia patients, compared with Imbruvica as a standalone therapy.

TG's shares more than doubled in morning trading on Monday.

The late-stage study involved adult patients with high-risk chronic lymphocytic leukemia (CLL) who have undergone at least one prior therapy.

The trial was designed to evaluate whether adding ublituximab would induce a statistically significant improvement in overall response rate by at least 20 percent between the two groups of patients.

The absolute difference between the two groups was about 30 percent, the company said on Monday.

TG said it would meet with the U.S. Food and Drug Administration to discuss accelerated approval.

A separate late-stage study testing ublituximab to treat multiple sclerosis is expected to begin later this year, pending the outcome of a mid-stage trial.

Ublituximab is also being evaluated in combination with another TG experimental drug, TGR-1202, for use in CLL and diffuse large B-cell lymphoma.

In 2015, AbbVie Inc forked out $21 billion for Pharmacyclics, giving it joint ownership of the blockbuster leukemia treatment, Imbruvica, with Johnson & Johnson.

Imbruvica, which is also approved to treat mantle cell lymphoma and a type of non-Hodgkin's lymphoma, generated $1.83 billion in sales for AbbVie last year.

The American Cancer Society has estimated that about 20,110 cases of CLL will be diagnosed in the United States in 2017, and the disease could claim 4,660 lives.

New York-based TG's shares were up about 87 percent at $10 in morning trading.