Yeah given current and near future leverage and bargaining position, the only reasons I can think of for Hepa to exercise at the $3.21 would be:

1) extreme confidence based on what they know from the board room and one of the few avenues for large accumulation,

2) providing much needed financial support to a struggling but promising partner with which they are already heavily vested (i.e. in for a penny in for a pound),

3) and continued accumulation toward greater leverage and perhaps even control (either alone or in combination with an ally) at some point.

But that would cost them approximately $30m out of pocket. Did I do the math right? ... (9m+ shares x $3.21)

The debenture may be another sweeter bite of the apple for them, at better valuation most likely ... $6m /$.53 currently = 11.3m shares versus $30m for 9m+ shares.

Plus exercising the warrants would essentially remove the Hepa debenture IP leverage by providing plenty of short term cash, well over the $6m. So, exercising the warrants, eliminates a cheaper (maybe) accumulation opportunity in May.

Exercising at $3.21 may not seem like a great business decision for Hepa in an acute business vacuum relative to other options -

But in a different financial "strategic" vacuum it could make a lot of sense for a partner that is "all in" and with high confidence in current developments and near term ROI. That exercise could have given a sorely needed cash infusion at a pps investment level that would likely spur market confidence also given the Hepa board room view of the Covid trial and other non-public developments.

Hepa (with a BR view) chose not to exercise and accumulate another large block of Warrant shares at inflated prices, and depending on how Covid rolls and whatever other RVX cash resources are out there, they may or may not get another large accumulation opportunity with the debenture. 

Haven't been keeping up on the overall ownership percentages of Hepa and Ori, or how much closer exercizing all of these warrant opportunities would push them toward majority, in combination?

Just interesting to watch the chess moves, speculate, over think, and discuss.