Good question

It is not un-preceded. Equal allocation is preferred -from an ethical point of view- to minimize participants numbers. Unequal allocation requires more patients to reach the same statistical power, so it is not the standard.

You might like to read this

Article The questionable use of unequal allocation in confirmatory trials

In the current crisis, no much time for repeated trials, you want to detect as much as possible of potential benefits and adverse reactions of the drug to answer the question "Is this drug good for COVID-19 patients or not?"

"Yes", "No", and "Good only if ......" are all good much needed answers if you are accurate and honest.

If the study gives inadequate data for some groups (due to limited numbers for example), the question will remain unanswered, open for more studies.

More studies means more time, which costs us more lives!

This cost outweighs the advantage of using equal allocation.

Iman Hassan Ibrahim Thank you for sharing the paper.. it explains a lot. They had recruited 158 participants in remdesivir group and 78 in placebo... Theoretically, they could have achieved the same power with 104 participants in both remdesivir and placebo (12 % lesser participants) according to the literature you have shared. So, I think conclude it is more of an operational (logistic and financial) and ethical issue than anything else.