An experimental heart failure drug being developed by Merck & Co showed promise in a pilot study as it improved breathing and kidney function, researchers said on Tuesday.

The drug, rolofylline, may also lead to fewer readmissions to hospital due to worsening heart failure, according to researchers who presented the data at the American College of Cardiology annual scientific meeting.

Rolofylline is an adenosine A1 receptor antagonist intended to improve renal, or kidney, function. Heart failure occurs when the heart can no longer efficiently pump blood throughout the system and often leads to worsening kidney function.

The study, which involved 301 patients hospitalized for acute heart failure and renal impairment, tested the drug at three doses against a placebo. Acute heart failure is a serious form of the disease in which a patient develops symptoms such as chest pain or respiratory distress.

The highest 30 milligram dose was more effective than the two lower doses - 10 mg and 20 mg - and placebo, researchers said. That is the dose expected to be tested in the large phase 3 study that will be used to seek approval of the medicine.

“Clearly the signal that we saw for protection against worsening of renal function was most apparent with the 30 mg dose and that is the reason we are moving forward with that dose,” Dr. Barrie Massie, the study’s lead researcher, said in an interview.

“Preserving kidney function is an important goal for improving the prognosis of patients with acute heart failure,” he said.

While the medicine was administered along with intravenous diuretics for just three days, Massie said 30 mg of rolofylline appeared to continue to provide protection after 14 days.

Patients in the study were judged to have been either a “success” as evidenced by improvement in dyspnea, or breathing problems; “failure” as evidenced by worsening heart failure, worsening renal function, readmission to hospital or death; or “unchanged.”

The drug’s effectiveness was also measured by its ability to help patients’ kidneys clear a substance called creatinine. Creatinine buildup is an indication of kidney dysfunction.

Fifty-three percent of patients treated with 30 mg of rolofylline were deemed treatment success compared with 37 percent on placebo, while the failure rate on the drug at 30 mg was 16 percent versus 28 percent on placebo, researchers said.

Nearly 60 percent of patients who received the 30 mg dose had marked or moderately improved dyspnea at days two and three, compared with 41 percent on placebo, researchers said.

The highest tested rolofylline dose was also associated with a trend toward reduction in the composite end point of 60-day death or hospital readmission for heart or kidney function problems.

The trial was too small to achieve statistical significance for survival or rehospitalization, Merck said.

The pilot study was designed to confirm the optimal dose of rolofylline and assess the goals of a larger, definitive outcome trial called PROTECT, which is expected to be completed by early 2009, researchers said.

There were no serious side effects seen in the pilot study, although the drug can cause seizures in patients at high risk of seizure, Massie said. There were two such cases in an earlier rolofylline study and some patients in the pilot program were pre-treated with antiseizure medication, he said.

The results suggest that rolofylline helps maintain kidney function over the near term, and may decrease death and rehospitalizations in patients with acute heart failure, researchers said.

“PROTECT hopefully will confirm these results,” Massie said.

“I think it could be a very important drug in these people who are hard to treat,” he added.

“If the results (of the PROTECT trial) are as favorable as we’ve seen with the 30 mg dose in the pilot phase, I think there is going to be widespread use,” he added.

CHICAGO (Reuters)