Shares of Silence Therapeutics jumped after the company said its proposed blood cancer treatment met its primary endpoint.

The stock rose 41% to $16.88 in premarket trading Monday. Through the previous close, shares had nearly doubled this year.

In a 36-week Phase 2 trial, 88% of patients treated with divesiran responded positively, compared with 19% of those treated with the placebo, the clinical-stage biotechnology company said.

The primary endpoint was the proportion of patients responding to divesiran, which is being tested as a treatment for patients with the blood cancer polycythemia vera.

The trial also met its key secondary endpoint of divesiran-treated patients having a significantly reduced phlebotomy rate compared with the placebo group.

Patients taking the treatment also showed improvements in hematocrit control, which involves keeping the percentage of red blood cells within a safe target range.

The treatment was well tolerated and safety was in line with previous trials.