Absolutely. Compounds that look good on paper all the time run into massive complications in practice. for instance, some "phospholipid nano particles" (just a sphere of cell wall shit that merges into the existing cell wall) can clump up, clog your alveoli in the lungs and cause your lungs to violently explode in a bloody fury. Now THAT's a proper respiratory illness. There are tons of compounds that on paper look great, but no one could account for how they react with some super obscure part of your body that the author never considered and the result is catastrophic. For instance, a famous case is DNP, or dinitrophenol, which binds to your brown fat cells. It raises your metabolism, so is just about the perfect weight loss drug, trouble is, if you take too much it can keep raising your metabolism until your body heats up over 114 degrees and you start slow roasting your organs alive, and there is no way to decouple the chemical from the receptor so all the doctors could do is pack you on ice and pray you can get to the other side of a couple days of your body trying to make brisket out of your ass.