To my knowledge, "conditional approval" does not exist. Certainly not after phase one. The idea behind conditional approval is that drug might be approved after phase 3, on the grounds that it seems effective but the FDA would like to see long-term data.
By nature, rare disease trials have two problems. One, not many patients and two, not enough time. NPC1 takes years to progress. It is different for every kid. Some kids have very bad mutations and die in a few years after birth. Others have less aggressive mutations and progression may take decades. I read an article about a women that was diagnosed with NPC1 at 60 years old.
So...an NPC1 trial only looks at a few patients( MNK and Orphazyme had 50-something patients, CTDH has less than that). The trials are for 52 weeks. In the FDA's opinion, 52 weeks is very small window into the disease progression. The idea behind conditional approval is to approve the drug on 52 week data if it seems positive. However, the trial participates would be monitored for the years to follow. If it appears after 3-5 years the drug actually does not work, approval is withdrawn.
I have heard many people lobby for this approach. My understanding is, as of now, it does not exist. I am not an expert. If you know otherwise please, direct me to that information. That would be very helpful!
I did hear a company argue that if a treatment is a re-purposed drug, with safety data already established, Phase one should be skipped. They argue in favor "conditional approval" with a short trial and few patients, as safety, theoretically, is not an issue.
