US biopharmaceutical research companies are currently developing 452 new medicines for the treatment of rare diseases, according to new industry figures.

The 452 new medicines and vaccines, all of which are now in human clinical trials or under review by the Food and Drug Administration (FDA), include treatments for genetic disorders, neurological conditions, infectious diseases and autoimmune disorders, says the report, from the Pharmaceutical Research and Manufacturers of America (PhRMA).

Although a rare disease is defined as one that affects fewer than 200,000 people in the US, the number of such conditions totals approximately 7,000 and collectively they affect nearly 30 million Americans, or one in 10 of the population, says PhRMA. According to the FDA, one third of all new drug approvals over the last five years have been for rare diseases.

And this year alone, 13 orphan drugs have received FDA approval, including treatments for Cushing disease, cystic fibrosis and Gaucher disease.

The 452 new medicines and vaccines currently under development include 105 for cancer, 85 for genetic disorders, 65 for blood cancers, 32 for neurological disorders, 28 for infectious diseases and 20 for respiratory conditions.  Examples include:

- use of targeted RNAi therapies for Duchenne muscular dystrophy (DMD), which affects about one in every 3,500-6,000 male births in the US each year;

- a potential new treatment for hypophosphatasia, a rare inherited bone disease in infants, which delivers the enzyme necessary for proper bone growth that patients with the condition are missing;

- a medicine for idiopathic pulmonary fibrosis (IPF) that targets elevated connective tissue growth factor in the lungs:

- a potential treatment for amyotrophic lateral sclerosis (ALS) that uses the patient’s bone marrow stem cells to create healthy neuron-like cells to replace diseased neurons:

- a potential first-in-class medicine for acute lymphoblastic leukemia (ALL) designed to focus the body’s cell-destroying T-cells against two different targets simultaneously, linking the T-cells to cancer cells: and

- a genetically modified vaccine designed for the treatment of pancreatic cancer.

Rare diseases provide opportunities to study human physiology and biomedical science from unique perspectives, leading to insight into more common disorders, says PhRMA. However, development of rare-disease medicines also poses unique challenges, such as recruitment of volunteers for clinical trials, since the patient population with a specific rare disease is typically very small, geographically dispersed and often children, it adds.