It takes at least 10 years for most medication, including drugs for rare diseases, to make its way from discovery to marketplace, said Dr Timothy Low, who is head of medical affairs at Shire Asia-Pacific.
Clinical trials alone - which test if a drug is effective and safe for humans - can take six or seven years.
Shire is a pharmaceutical company that specialises in producing drugs for people with rare diseases.
But there are differences when it comes to developing rare-disease drugs compared with drugs for more common conditions.
"In rare diseases, the industry is often pioneering breakthrough medicines, ones that are, for the first time, exploring a new biological pathway," explained Dr Low.
The price of rare-disease drugs also reflects the high failure rate for developing them, the "exceptionally complex" processes behind manufacturing them, as well as related services for these drugs, such as training and education, he added.
The Ministry of Health (MOH) said that "the cost of some of these drugs may be high, given that there may only be one or two patients with the specific rare disease at any given time".
Still, MOH said it is continuing to look at how to better support patients with such conditions, adding: "No Singaporean will be denied medical treatment because of their inability to pay."
People here can tap the Medication Assistance Fund to help with the cost of such expensive, non-standard medications, though the drugs need to be listed under the fund.
Those who require drugs that are not listed can also get help on a case-by-case basis. However, these drugs must still be approved by the Health Sciences Authority (HSA). And companies that want to register products with the HSA must pay fees that can go into the tens of thousands.
Mr Kenneth Mah, who is co-founder of the Rare Disorders Society Singapore, said patients find it very difficult to afford such drugs if government funding is not available. This, in turn, means pharmaceutical companies have less incentive to register their drugs for use here.
If patients need a rare drug that is not currently licensed for use, said Mr Mah, doctors can apply to the HSA for an exemption.
He added: "Pharmaceutical companies won't want to register their drugs unless they know that patients can afford them."