Assuming that the samples are not biased in favour of any of the drugs, you can try to calculate the 95% confidence interval for each of the new drugs and check whether or not they intersect with the (66%-74%) you had for drug A.

I didn't do the math precisely, but The results will look something like (52%-68%) for drug B and (62%-78%) for drug C. I think a larger sample would really help

Assuming that the samples are not biased in favour of any of the drugs, you can try to calculate the 95% confidence interval for each of the new drugs and check whether or not they intersect with the (66%-74%) you had for drug A.

I didn't do the math precisely, but The results will look something like (32%-48%) for drug B and (22%-38%) for drug C. I think a larger sample would really help