I think the other element here is risk, particularly revolving...

I think the other element here is risk, particularly revolving around Zantrene dosage. It looks as though optimal dosing may be a fine line between too little (limiting the effectiveness of Zantrene) and too much (limiting the effectiveneas of the immunotherapy). I'm speculating but optimal dosing may also vary between cancers, cell lines, patient types, immunotherapies, etc. and may require significant resources to fully understand and quantify.

This is the sort of risk that may be difficult for a small company like Race to mitigate, as (worst case) a failed trial could have a very significant impact. However, it would not be such a problem for big pharma with much larger resources and a much longer time horizon to be able to invest in getting things right, indeed it's probably more of their bread and butter.