The data in a clinical trial are collected at research sites with many different investigators, spreading many different countries. These investigators are gene

The data in a clinical trial are collected at research sites with many different investigators, spreading many different countries. These investigators are generally not the people who 'alter the data', it are the CROs or Pharmaceutical companies that alter the data set AFTER all data has been collected and analysed. So if the collected data is registered in some immutable manner at the research sites, it becomes (near) impossible for the CRO to alter that data after analysis. This is where blockchain adds value. The clinicaltrials.gov repository only records high level findings of a clinical trial, again AFTER data analysis. This in no way prevents researchers from entering fake data, if the results are not as they want (registering it at the moment it is collected, when researchers don't know what the results would be yet, would make this more difficult). The comparison with the FDA (that supposedly makes it impossible to alter data after submission) does not make a lot of sense. This is only done prior to market application after years and years of performing clinical trials (where in the mean time one could alter the data in anyway they want). Moreover, the FDA actually stipulates that all data and documents need to be recorded in a time-stamped and immutable manner, so I'm certain they would welcome the use of blockchain technology here (which they do, have a look at their website).