As Mike mentioned, it is literally anyone's guess right now. Even in the leaked presentation management came out and said they haven't received any further requests from FDA and do not know why they have not heard back.
I'm going with it's a mix of several reasons, none of which Humanigen is involved with or is required to somehow gather more data or give more info to the FDA. Look at what's happening with FDA leadership right now, things are a bit of a mess and they have/had a large amount of review staff working on the Pfizer approval.
My guess is that like any regulatory body or government agency, there is so much red tape to get through and bureaucracy and HGEN is simply too small a company to have the resources to push it through either through political or social pressure.
Just sit back and wait, the EUA is coming but you're going to torture yourself checking for an update every single day.
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