Feb 17 (Reuters) - Pharmacyclics Inc said its cancer drug developed with a Johnson & Johnson unit improved overall response rate in high-risk leukemia patients.

Those administered with Imbruvica showed an overall response rate of 88 percent, while 76.6 percent survived without the disease getting worse at 24 months.

All 16 patients enrolled in the small study suffered from high-risk chronic lymphocytic leukemia (CLL) and had failed to benefit from stem cell transplants and other therapies.

Patients who relapse of CLL following stem cell transplant are hard to treat with chemotherapy as they do not produce enough blood cells or develop post-transplant complications.

This could be a new patient population for the drug, which is already approved for a number of other indications associated with CLL.

Imbruvica is already approved for CLL patients who have received at least one prior therapy, and for CLL patients with a rare genetic mutation.

About 115,000 patients suffer from CLL in the United States and about 16,000 are newly diagnosed each year.

Shares of Pharmacyclics were up 1.4 percent at $165.69 in early trading on the Nasdaq.

(Reporting by Amrutha Penumudi in Bengaluru; Editing by Maju Samuel)