A new, highly effective class of psoriasis drugs did not appear to raise the risk of heart problems in a review of published studies, but the analysis may not have been big enough to detect rare cases, U.S. researchers said.

Abbott Laboratories pulled its U.S. and European marketing applications for one of the drugs in January, known as briakinumab, due to concerns raised by U.S. regulators.

The drug is part of a new class of treatments known as anti-IL-12/23 agents that have been shown to be highly effective at treating psoriasis, an autoimmune disease marked by well-defined patches of red raised skin.

Patients with severe psoriasis are already at increased risk of heart attacks, and doctors are worried the new treatments may increase this risk.

Abbott's decision also raised concerns about Johnson & Johnson's Stelara or ustekinumb, the first drug in the class to win marketing approval.

"We're concerned about the apparent excess in cardiovascular events," said Caitriona Ryan of the Baylor Research Institute in Dallas, whose study appears in the Journal of the American Medical Association on Tuesday.

Ryan and colleagues analyzed data from 22 randomized clinical trials of anti-IL-12/23 and anti-TNF drugs to treat chronic plaque psoriasis, the most common form of psoriasis.

The older drugs block tumor necrosis factor-alpha or TNF-alpha, a protein involved in inflammation. The newer drugs targets two different inflammatory proteins — interleukin 12 and interleukin 23.

Anti-TNF drugs in the study included Abbott's Humira or adalimumab, Pfizer's Enbrel or etanercept and Johnson & Johnson's Remicade or infliximab.

Ryan's team found that during the active portion of the clinical trials they reviewed, 10 out of the more than 3,179 patients who were treated with anti-IL-12/23 had a major cardiac event, such as a heart attack, stroke or death related to heart disease, compared with no heart problems in the 1,474 patients treated with a placebo.

Among patients treated with the older anti-TNF drugs, only 1 of the 3,858 patients had a major cardiac problem compared with 1 of the 1,812 patients treated with placebo.

Ryan told Reuters that although the study did not show a statistically significant increase in heart problems, it was likely not large enough to detect these rare events.

Dr. Christopher Ritchlin, a rheumatologist at the University of Rochester Medical Center, who has seen the findings but was not involved with the study, said the analysis does not ease his concerns about drugs in this class.

"There are some safety signals you are seeing in the treatment groups that are not in the placebo groups. I'm not saying there is a definite association, but there is smoke here," he said.

Ryan said the work exposes flaws in the design of clinical trials, which are powered to show differences in the effectiveness of drugs, but not to identify rare safety problems.

What is needed, she said, is some form of regulatory oversight of drugs after they win marketing approval, beyond the current system in which individual companies submit reports to the U.S. Food and Drug Administration.

"We have to find a way of being able to systematically gather safety data for these agents after they are on the market," Ryan said.