Interim results from an early stage trial of Pharmacyclics Inc's experimental blood cancer drug show the number of leukemia patients responding to the medicine has increased over time.

At 10 months follow-up, 70 percent of patients treated with the lower dose of the drug, known as PCI-32756, had a significant improvement in their condition. That is up from the 48 percent response rate reported by trial investigators after six months of follow-up.

The trial includes 61 patients with chronic lymphocytic leukemia who have stopped responding to at least two other types of treatment.

In the high-dose group, 44 percent of patients have responded to PCI-32756 after 6.5 months of follow-up.

The findings are phenomenal, especially for patients who had already been treated with earlier rounds of therapy, said Dr, John Byrd, professor of hematology and oncology at Ohio State University in Columbus, and a lead investigator in the trial.

The updated results are being presented at a meeting of the American Society of Hematology.

PCI-32765 is an oral drug designed to target an enzyme known as Bruton's tyrosine kinase and block the function of cancerous B-cells. The drug is being studied as a treatment for a range of B-cell malignancies.

Side effects seen in the CLL trial included diarrhea, nausea and high lymphocyte counts.

Eighty-two percent of patients remain on treatment, and 8 percent have seen their disease worsen.

Pharmacyclics said earlier this week it had licensed PCI-32765 to Johnson & Johnson for $150 million upfront and as much as $825 million in payments tied to development milestones.

The announcement sent shares of Pharmacyclics down nearly 20 percent as investors theorized that the J&J deal made it less likely Pharmacyclics would be acquired by a larger company, at least in the near term.