Rare diseases are not uncommon, and may be the mother lode for the world's pharmaceutical producers and researchers

Rare diseases may individually affect a relatively small number of patients compared to common ailments but the overall burden on society is heavy and drug developers should not ignore its market potential, says policy advocate.

"Rare diseases are not that rare when one considers the fact that each patient's disease also has a big impact on each of their family members and carers," said Li Linkang, executive director of China Alliance for Rare Disease. "Medical experts have made a conservative estimate that China has some 20 million rare disease patients, with around 200,000 new cases per year.

"The real numbers should be far higher as misdiagnoses and missed diagnoses are common ... most doctors have no experience with rare diseases and it takes three to five years for most patients to be diagnosed, which is too late."

The non-profit body is collecting nationwide data on rare disease prevalence to help government officials come up with policies to make drugs more affordable and accessible, and incentivise companies to invest in drug discovery programmes.

In the United States, the world's largest and most advanced pharmaceutical market, between 25 million to 30 million people live with as many as 7,000 types of rare diseases, according to the Genetic and Rare Disease Information Centre funded by the Department of Health and Human Services.

Rare disease is defined there as a condition that affects fewer than 200,000 people, under the 1983 Orphan Drug Act to incentivise new drugs development.

Under the US law, a disease that afflict more patients could also be granted "orphan status" if there is no "reasonable expectation" that the cost of development will be recovered from sales.

The status affords developers of drugs for such diseases benefits such as seven-year market exclusivity and tax credits on clinical trial expenses.

Without the status, a new drug is typically only given five-year exclusivity after marketing approval is granted.

The US market for rare-disease drugs is estimated at US$43 billion, just under 10 per cent of the nation's total drug spending of US$451 billion, according to the IQVIA Institute for Human Data Science.

That year, the US government granted "orphan" designations to 80 diseases " a record since 1983 - and over 429 drugs under development. The majority are oncology, blood and genetic disorders.

By August last year, 731 diseases and 503 therapies were granted such status.

Given the small patient numbers for rare disease drugs, their costs are high. The median US annual invoice price for a single therapy amounted to over US$46,000 in 2017, according to IQVIA.

Oncology medicines took up the bulk of orphan products, whose annual costs per patient range between US$1,000 and just under US$500,000.

Only three out of 43 non-oncology orphan drugs approved by the US Food and Drugs Administration between 2013 and 2017 are marketed in China, according to Beijing-based drug developer CANbridge Pharmaceutical.

China's rare disease market could potentially reach US$15.5 billion " 36 per cent that of the US market in 2017, assuming only one-fifth of China's population have access to diagnosis and treatment access, it estimated.

While individual drugs' costs are high, Li said the government should consider the broader context when making policy decisions.

"Some drugs sound hugely expensive on a per patient per year basis, but some rare diseases only have several hundred or several thousand patients nationwide," he said. "Their total drug cost is not huge compared to the government's drug reimbursement budget for common chronic diseases like high blood pressure."

This article originally appeared in the South China Morning Post (SCMP), the most authoritative voice reporting on China and Asia for more than a century. For more SCMP stories, please explore the SCMP app or visit the SCMP's Facebook and Twitter pages. Copyright © 2019 South China Morning Post Publishers Ltd. All rights reserved.

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