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Table 4 Summary of key similarities and differences between DURDs and DORDs identified in the present study

From: Characteristics of drugs for ultra-rare diseases versus drugs for other rare diseases in HTA submissions made to the CADTH CDR

Similarities between DORDs and DURDs
Number of studies Submissions for DURDs and DORDs are similar in terms of the number of studies considered in the CDR review of clinical data
Overall reasons for negative recommendations Insufficient clinical evidence was the most common reason for a negative recommendation for both DURDs and DORDs, followed by cost-related issues
Differences between DORDs and DURDs
Growth in annual submission number The steady growth in the total number of annual DRD submissions is predominantly attributable to growth in the number of annual submissions for DORDs, whereas the annual number of DURD submissions has risen only slightly
Molecular basis DURDs are distinct in by being almost exclusively biologic molecules, whereas DORDs include a substantial proportion of small molecule-based therapies
Study size Sample sizes for studies that support submissions for DURDs are generally smaller than those for DORDs
Study design The majority of submissions for DURDs contained clinical data from non-randomized uncontrolled trials without comparator, whereas most DORD submissions included data from high-quality trial designs with active and/or placebo control arms and double-blinding
Cost The average treatment costs of DURDS are generally substantially higher than those of DORDs
Recommendation type Relatively more negative than positive reimbursement recommendations were issued for DURDs compared to DORDs
Reasons for negative recommendation The rate of negative recommendations relating clinical reasons only was greater for DURDs than for DORDs