Drug Information Q&A Q54. What is an "orphan drug"?

Answer

Orphan drugs are also called "drugs for rare diseases," and are drugs for diseases for which the number of patients is small and treatment methods have not been established, such as intractable diseases.

Explanation

Regardless of the number of patients, the importance of drugs in the treatment of diseases remains the same. Considering the position of patients suffering from intractable diseases that are difficult to treat, the role of "orphan drugs" in society is very significant.

However, from a practical standpoint, the lack of demand for orphan drugs has made it difficult to spend huge amounts of money on their development. Even when the efficacy of a drug was known to some extent, the global trend was not to proceed to full-scale development.

From the 1970s to the 1980s, there was a movement to establish a public assistance system for research and development of orphan drugs, mainly in developed countries, and the Orphan Drug Act was enacted in the U.S. In Japan, the Orphan Drug Act was enacted in 1979.

In Japan, a new drug research and development program for intractable diseases was launched in 1979, followed by the simplification of the approval process in 1985 and the revision of the Pharmaceutical Affairs Law in 1993, which led to a full-fledged public R&D assistance system for orphan drugs.

Currently, the criteria for designation as an orphan drug include the following: the number of patients must be less than 50,000; the disease must be difficult to treat, such as an intractable disease; there must be a high medical need; there must be no other suitable alternative drug or treatment method; and the drug must be expected to have extremely high efficacy or safety compared to existing drugs. The criteria include the following.

Once a drug meets these criteria and is designated as an orphan drug, it is eligible to receive subsidies for research and development, and is given priority over other drugs in the approval process so that it can be made available to patients as quickly as possible.

These institutional support measures have made the research and development of orphan drugs easier than in the past, and have enabled the development of drugs for intractable diseases for which there are only a few patients in Japan.

Chart/Column

54｜Criteria for designation as an orphan drug

Less than 50,000 patients (less than 200,000 in the case of the U.S.)
Targets serious diseases such as intractable diseases.
High medical necessity
No suitable alternative drug or treatment is available
Significantly more effective or safer than existing drugs
High potential for development
Development costs are not expected to be recovered from sales (in the U.S.)

MINI Column Recently approved orphan drugs

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Indications	Generic name
New influenza (H5N1)	Cell culture influenza vaccine
Malignant glioma	Bevacizumab
Interstitial pneumonia associated with polymyositis and dermatomyositis	Tacrolimus hydrate
Pandemic influenza	Cell culture influenza vaccine
HIV-1 infection	Cobicistat, elvitegravir
Lipoatrophy	Metreleptin
Acute lymphocytic leukemia	clofarabine
Acute seizures in patients with acute porphyria	Hemin
Chronic lymphocytic leukemia	Ofatumumab
Tonic and atonic seizures in Lennox-Gastaut syndrome	Rufinamide
Visualization of tumor tissue during tumor resection for malignant glioma	Aminolevulinic acid hydrochloride
Hypophosphatemia	Sodium dihydrogen phosphate monohydrate
Renal angiomyolipoma, subependymal giant cell astrocytoma	Everolimus
Huntington's disease	Tetrabenazine
Malignant soft tissue tumor	Pazopanib hydrochloride
Clonic or tonic-clonic seizures in patients with Dravet syndrome	Stilipentol
HIV-1 infection	Rilpivirine hydrochloride
Erythema Nodosum Leprae	Thalidomide

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