Angiogenix Inc.'s vascular disease product, Acclaim, missed its primary endpoint in a Phase II trial in chronic stable angina patients, but the company said it plans to further investigate the product's ability to prevent nitrate tolerance.
"There's no question, in this trial, that the patients who received continuous nitrate became tolerant to it," said Ed Jennings, CEO of the Burlingame, Calif.-based company. "What we're trying to do is overcome that tolerance, and we did not meet that in this trial."
The 204 patients enrolled in the study were randomized to receive either Acclaim - isosorbide mononitrate in combination with the amino acid L-arginine to prevent nitrate tolerance - or nitrate therapy alone. Results of the trial indicated that Acclaim showed no statistical significance in increased walking time, determined from the beginning of the test until the patient developed angina of a moderate degree.
But, despite the disappointing trial results, Jennings told BioWorld Today the company "hasn't given up on the concept," adding that the "data we have are outstanding, and there are no safety issues" with the drug.
"I think what we learned is that there's a good chance we need higher levels of L-arginine to be bioavailable in the plasma in order to prevent the tolerance effect," he said. Acclaim was shown to be efficacious in a smaller two-week, 14-patient trial, but Jennings said researchers used a different dosing regimen for the larger study - twice a day rather than four times.
Angiogenix has an ongoing pharmacokinetic and pharmacodynamic study of Acclaim in Hamburg, Germany, to evaluate the effects of delivering higher amounts of L-arginine.
"Once we get those results in March, we'll redesign the formulation to attempt to increase the bioavailability," Jennings said. "We'll take the results of the trial we just completed to get a measurement of what we need."
Acclaim is one of three products Angiogenix has in development for improving vascular function by increasing nitric oxide production. Jennings explained that nitrate therapies are designed to work by "relaxing the blood vessels and allowing blood flow by activating the endogenous nitric oxide synthase enzyme." The ENOS enzyme then releases nitric oxide.
"But, for some reason, when given continually, patients develop a tolerance for nitrates, and nitric oxide stops getting through," he said, adding that existing therapies call for intermittent dosing schedules, which help prevent nitrate tolerance but also deny patients the benefit of continual treatment.
"So we looked at combining L-arginine, which is a precursor for nitric oxide, to try and keep the ENOS enzyme working and allow the nitrate to work as it is supposed to on a continued basis," Jennings said.
Analysis of Acclaim's Phase II data did reveal positive, though not statistically significant, trends, namely an extended length of time before the onset of angina and ST-segment depression in patients treated with Acclaim, as well as a trend toward benefit in those patients receiving concomitant ACE inhibitor therapy.
"That was interesting because it suggested there might not have been enough L-arginine," Jennings said.
While analyzing data and awaiting results of the Hamburg study, Angiogenix also will have to consider funding sources for its next Acclaim trial, as well as upcoming trials for the company's two other clinical products.
"We're having discussions with potential partners for those two projects, and we're also having funding discussions with capital sources for another Acclaim trial," Jennings said.
Angiogenix raised $12 million in a private placement in December 2002 to fund the Acclaim trial, shortly after acquiring the product from Augusta, Ga.-based NitrOsystems Inc. An extra investment of $3 million was added in July 2003. (See BioWorld Today, Dec. 19, 2002.)
Jennings said the company's other products, set to begin Phase II trials this year, likely will not be affected by Acclaim's setbacks. "I would say right now they're still on the same schedule," he said.
ANGX-1039 is the company's "large market drug" for the treatment of peripheral arterial disease. With only two FDA-approved treatments on the market, pentoxifylline and cilostazol, Angiogenix said the market opportunity could be more than $1 billion.
The other product, ANGX-3227, is designed for a "small, concentrated niche market," Jennings said. The drug treats sickle cell disease.
Although Acclaim is being tested only in angina patients, the company said it intends to investigate additional indications, such as post-operative conditions and congestive heart failure.