CAMBRIDGE, Mass. (AP) — Infinity Pharmaceuticals will stop studying one of its potential drugs as a rheumatoid arthritis treatment after it failed to generate enough improvement in patients during a mid-stage study.

Shares of the Cambridge, Massachusetts, company tumbled early Thursday morning after it announced the discontinuation but said it still plans to study the drug, duvelisib, as a potential treatment for blood cancers like leukemia and non-Hodgkin lymphoma. It is collaborating with fellow drug developer AbbieVie Inc. on those potential treatments.

Infinity was studying duvelisib in patients with moderate-to-severe forms of rheumatoid arthritis, a chronic inflammatory disease that affects the joints and destroys soft tissue, cartilage and bone. More than 300 patients in the study received a combination of either duvelisib and another drug, methotrexate, or a fake drug and methotrexate.

The drug fell short of the study’s main goal of generating a certain rate of improvement after three months of treatment.

Rheumatoid arthritis represents a major area of research for drug companies because it is chronic, meaning patients will likely take the drugs regularly for a long time.

Infinity Pharmaceuticals Inc. shares were down 11 percent, or $1.81, to $14.50 more than an hour before markets opened. The stock had climbed about 30 percent last year.