Image credit: Nancy Goodman/Kids v. Cancer

President Obama signed a bill today that will provide incentives to drug companies to research and develop drugs for rare diseases.

The Creating Hope Act grants pharmaceutical companies that create drugs for diseases like childhood cancers a voucher giving speedier review of any other drug they submit for approval.

The Oval Office signature was a hard-fought victory for children like Mollie Ward, 11, who survived a rare form of pancreatic cancer thanks to an experimental drug, and for other families who have fought childhood cancers.

Nancy Goodman, founder of Kids v. Cancer, which is devoted to pediatric cancer research, lost her son Jacob Froman, 10, to a rare form of brain cancer nearly four years ago. He'd been diagnosed at the age of 8.

She was instrumental in getting the bill passed. She and others said that drug companies had little financial incentive to develop new treatments because childhood cancers are so rare.

"The reason I started working on the Creating Hope Act was that I found very early on that there are just very few drugs to treat kids with cancer," she told ABC News. "We created a big, fat carrot. The carrot is a voucher."

While 50 new drugs for adult cancer have been released in the last 20 years, just one expressly for pediatric cancer has gotten initial Food and Drug Administration approval, doctors say.

The track record for drugs for other pediatric rare diseases is even worse.

"The reason that companies don't make pediatric drugs is all market force driven," said Dr. Henry Friedman, an neuro-oncologist at Duke University Medical Center. "Companies have an obligation to their shareholders to make money. The pediatric diseases by and large are such low numbers. … The incentive to make pediatric drugs is very small."

Goodman said the measure was smart legislation and an attempt to ensure that more families don't experience what she has.

"I don't think the American public realizes how devastating pediatric cancer is," she said. "It's far worse than any other adult cancer. There's something unfair and unjust about the death of a child."