The global pharmaceutical industry is pouring billions of dollars into developing treatments for rare diseases, which once drew little interest from major drugmakers but now point the way toward a new era of innovative therapies and big profits.

The investments come as researchers harness recent scientific advances, including the mapping of the human genome, sophisticated and affordable genetic tests, and laboratory robots that can screen thousands of compounds per hour in search of the most potent ones.

"It's a very, very promising time," said Jimmy Lin, a National Institutes of Health cancer researcher who cofounded the Rare Genomics Institute.

By definition, a rare disease is one that strikes fewer than 200,000 Americans, sometimes only a few dozen. But with 7,000 rare diseases known to doctors, and more emerging all the time, nearly 1 in 10 Americans has a rare disease. For most, there is no treatment.

For decades, drugmakers were reluctant to invest in rare-disease treatments, preferring to focus on mass-market drugs for cholesterol, heart trouble, and other common problems. Then, starting a decade ago, patents on some of the industry's most lucrative medicines began to expire, and cheap generic drugs started wiping out tens of billions of dollars in annual revenue.

So many companies shifted money to rare-disease drugs, knowing that those medicines cost less to develop and will face limited competition. Some already sell for $100,000 or more for a year of treatment, although drugmakers usually give financial aid to patients and big discounts to insurers.

"They're re-creating the blockbuster," said analyst Steve Brozak of WBB Securities. "There's more money, fewer patients, and it's 10 times easier to defend high prices to payers."

Last year, the Food and Drug Administration approved a record 17 medicines for rare diseases. More than 450 others are in development.

Patient-advocacy groups are getting better at raising money for research and building patient registries that could be used to recruit participants for drug studies, a process that otherwise can take years.

In the 1970s, only a handful of rare-disease drugs got approved. The 1983 Orphan Drug Act helped stir interest by providing expedited drug reviews, tax credits, and other benefits for drug companies. Since then, about 220 medicines have been approved, with 93 in the last decade.

For common conditions, drugmakers test treatments on thousands of patients, then undergo a regulatory review that can take a decade and cost more than $1 billion. For rare diseases, drugs sometimes are tested only on a few dozen people, and testing wraps up sooner.

That, plus government financial incentives, can cut development costs by one-third to one-half, and approval is nearly assured.

Pfizer Inc., which has major operations in Collegeville, made $3.53 billion last year selling rare-disease treatments, not counting 10 cancer drugs for patients with specific genetic mutations.

By 2019, 34 rare-disease drugs could have annual sales exceeding $1 billion each, says a forecast by the research firm GlobalData.