By Jim Shrine
Sibia Neurosciences Inc. started a second Phase II trial of its agent for Parkinson's disease, this time in combination with L-dopa.
Patients in the double-blind, placebo-controlled study will take a different dose of the small molecule SIB-1508Y on each of three clinic visits and placebo during one visit. They will be given half their normal dose of L-dopa on all four visits. The 15 to 20 patients will serve as their own controls.
"We think this is an innovative approach to treating Parkinson's disease, because we're attempting to address not only the motor symptoms, but also the cognitive deficits associated with the disease," said Jeffrey McKelvy, Sibia's executive vice president and chief scientific officer. "There's a growing awareness of the fact that Parkinson's patients do have cognitive symptoms as well as motor symptoms."
SIB-1508Y is designed to selectively regulate dopamine and acetylcholine, which are linked to progression of Parkinson's and cognitive dysfunction, respectively. Preclinical studies suggested lower doses of both the drug and L-dopa have synergistic effects that increase efficacy, McKelvy said.
Halving the L-dopa dose should lead to reduced symptoms, he said, and the company hopes SIB-1508Y will alleviate re-emerging symptoms. The primary endpoint is motor improvement, and a cognitive evaluation will be used in one of the study's two centers.
Nearly a year ago Sibia, of La Jolla, Calif., began its first Phase II study of SIB-1508Y. In May, the doses were lowered and schedules changed in response to patient complaints of lightheadedness. The dosing part of the trial is expected to be completed in a month or two, McKelvy said.
The first study is testing SIB-1508Y as a monotherapy in early-stage patients who have taken no other drugs for their disease. No patients have dropped out since the trial resumed.
The new study, in later-stage Parkinson's patients, is expected to take about six months. It is designed to provide more dosing information and proof-of-principle for efficacy.
"In treatment of Parkinson's disease, it is inevitable patients will be on combination therapy," McKelvy said. "The underlying pharmacology of the effect of our drug offers the possibility of reducing L-dopa doses.
"The management of the disease is still do difficult," he added. "We wanted to gain experience with its use in combination therapy. Recently, there have been some problems reported with the use of the some of the dopamine agonists, so we think there is still an unmet need in this area, and we're doing the right thing moving this forward."
McKelvy said tests of the compound in animal models showed efficacy by itself and in combination regimens.
Sibia's stock (NASDAQ:SIBI) closed Monday at $4.75, unchanged. N