For latest version: please go to https://academicentrepreneurship.pubpub.org/pub/einr3b30/release/2 In the U.S., a rare disease is one that affects fewer than 200,000 patients. There are more than 7,000 rare diseases today but relatively few specific therapies for them, mainly because the manufacturers cannot recoup their drug development costs. Orphan drug status allows sponsors to apply for incentives such as the Orphan Drug Tax Credit (ODTC), marketing exclusivity for seven years for the first orphan drug for a given rare disease, and an attractive drug-pricing scheme, amongst other benefits. Orphan drug trials are generally single arm (no placebo arm), nonrandomized, and open label. Safety Phase 1 trials are not usually required, and Phases 2 and 3 can be combined when the patient population is very low. Sponsors of an orphan drug can make use of expedited Food and Drug Administration (FDA) programs such as the Fast Track, Breakthrough Therapy, and Priority Review designations, as well as the Accelerated Approval pathway and unique grant funding opportunities, such as the Orphan Products Clinical Trials Grant program. The FDA facilitates patient-focused drug development (PFDD) meetings, wherein they collect patient experience data from the patients, their family members, their caregivers, and disease foundations. These data can help the orphan drug developers for a given rare disease in determining clinical endpoints and the route of therapy administration for their clinical trials.