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Pediatric Rare Disease Therapies Increase, But Most Repurposed, Study Finds

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Pediatric Rare Disease Therapies Increase, But Most Repurposed, Study Finds
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The number of treatments for children with rare diseases has grown over the past decade, according to a new study. However, despite the increase, nearly 7,000 rare diseases are still lacking treatment.

And federal incentives to boost treatment development for these rare diseases have primarily focused not on creating new therapeutics, but rather on expanding the use of existing ones, the data also showed.

The study, titled “Pediatric Orphan Drug Indications: 2010–2018,” was published in the journal Pediatrics.

Children comprise half of the people affected by rare diseases, which are defined as those affecting less than 200,000 Americans. While the investment in the development of treatments for children with rare disorders is crucial, the rarity of the diseases makes them less attractive for pharmaceuticals.

To motivate investment by pharmaceutical companies in the development of therapies for rare diseases — called orphan drugs — several federal incentives have been developed over the years. These include tax exemptions, grants for accelerating and testing potential therapies, and an exclusivity period of seven years to enhance marketing. During that time, competitors are precluded from marketing an alternative version of the therapy for the same disease.

Now, the researchers identified 402 orphan drugs approved by the U.S. Food and Drug Administration (FDA) between 2010 and 2018.

Noting that “data are lacking on the number, nature, and benefits of recently approved pediatric orphan indications,” the team conducted an analysis.

The results showed that a third of the 402 treatments — 136, corresponding to 33.8% — were specifically for children (pediatric indications), and targeted 87 unique diseases in all. A total of 21 diseases were targeted by more than one therapy.

One of the most frequently targeted rare diseases among children was cystic fibrosis, with 12 pediatric orphan indications, along with acute lymphoblastic leukemia, which also could be treated with 12 approved orphan drugs. Another common rare disease target among children was the immune disorder hereditary angioedema, characterized by swelling under the skin, with six pediatric orphan indications.

Of the 136 approved pediatric orphan drug applications, the majority were for existing therapies — some decades old. Some of the therapies were approved for treating common diseases.

In all, 45 (33.1%) were existing treatments approved for at least one common disease that were repurposed, and 31 (22.8%) were existing therapies approved only to treat rare diseases.

In contrast, 60 (44.1%) of the approved pediatric therapies were for new drugs.

“Our study reveals reason for optimism and reason for concern,” Kao-Ping Chua, MD, PhD, a pediatrician and researcher at Michigan Medicine C.S. Mott Children’s Hospital, and the study’s lead author, said in a press release.

“Many pediatric orphan indications may have represented breakthroughs for children with rare diseases. At the same time, most indications were not for new drugs, and some represented relatively minor expansions of use,” Chua said.

“Orphan drugs are costly to society, and it’s important to make sure that these costs are justified by the amount of benefit to patients,” he added.

According to the team, “the diseases targeted by the 136 pediatric orphan indications were most commonly categorized as genetic and/or metabolic (16.9%), hematologic (16.9%), immunologic and/or rheumatologic (12.5%), and cancer (11.8%).”

Among 97 treatments eligible for the FDA’s breakthrough therapy designation — intended to accelerate the development and review of a potential therapy for a serious or life-threatening disease, with clinical evidence of substantial improvement over existing options — 20 (20.6%) received the designation.

“Although the Orphan Drug Act has been effective in incentivizing drug development, our findings suggest that not all pediatric orphan indications hold the same value,” said Lauren Kimmel, a research assistant at the University of Michigan Medical School and Child Health Evaluation and Research Center (CHEAR), and the study’s first author.

“Policymakers should ensure that resources are being used efficiently and effectively to stimulate development of new therapies for rare diseases that don’t have any treatment options,” Kimmel concluded.

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