The Food and Drug Administration approved 27 first-of-a-kind drugs in 2013, down from 39 new medications in 2012, which was a 15-year high.

Despite the decline, FDA officials say the tally of innovative medications approved last year is in line with the historical trend. On average, the FDA has approved 28 first-of-a-kind drugs annually over the past five years.

FDA drug approvals are watched closely by analysts as both a barometer of industry innovation and the federal government’s efficiency in reviewing new therapies.

Experts say the number of drug approvals declined in 2013 mainly because there were fewer drugs submitted for review.

According to an FDA presentation given last month to industry executives, the agency received at least 32 applications for innovative medications in 2013, down from 41 in 2012. Generally the FDA takes between 6 and 10 months to review new drug applications.

“I don’t think this reflects badly on the way FDA is working, rather on the number of applications they had to review,” said Ira Loss, who covers the industry for Washington Analysis. There are at least 25 new drug applications pending at FDA for 2014 with more expected to be filed early this year, according to Washington Analysis.

More drug applications bode well for an industry that thrives on new products and has seen patents on some of its all-time blockbuster sellers — including the cholesterol pill Lipitor and the blood thinner Plavix — expire in recent years.

FDA drug approvals peaked at 53 in 1996 before declining in the wake of a series of high-profile drug safety incidents, culminating with the withdrawal of Merck’s painkiller Vioxx in 2004 because of links to heart attack and stroke.

Drug approvals have bounced around in the mid-twenties for the last decade or so, before jumping to 30 in 2011. The 39 drugs approved in 2012 was the highest annual tally since 1997.

Experts attribute the recent uptick to a combination of factors: a stable, well-funded FDA and a newly established research model among drugmakers that focuses on first-of-a-kind drugs for rare conditions with few other medical treatments.

One-third of the 27 new drugs approved last year were for rare diseases and medical conditions, continuing a multiyear trend favoring so-called orphan drugs. Such therapies include drugs like Imbruvica, a drug from Pharmacyclics and Johnson & Johnson that was approved in November to treat a rare form of blood cancer. Imbruvica was one of three drugs approved in 2013 under a new “breakthrough” drug designation, which was authorized by Congress in 2012. The classification is designed to speed up development of promising drugs by providing companies with extra meetings and earlier communication with FDA scientists.

But not all the breakthrough drugs of 2013 were for rare diseases or niche conditions.

Perhaps the most important new therapy of the year was a highly anticipated hepatitis C drug from Gilead Sciences Inc. that is expected to offer a faster, more palatable cure to millions of people infected with the liver-destroying virus. The daily pill, Sovaldi, has been shown to cure roughly 90 percent of hepatitis C cases in just 12 weeks, compared with older drugs that cure about three out of four patients and can take up to a year.

In the first quarter of 2014 the FDA is scheduled to rule on several innovative medications, including a long-lasting injectable drug for hemophilia from Biogen Idec and the first-ever treatment for a sleep disorder caused by blindness, developed by Vanda Pharmaceuticals. Inc.

(AP)