However, these are not "research chemicals" in the sense that people usually seem to use the phrase. The article refers to antibiotics, cancer treatments, neuromodulators... the sorts of drugs that the FDA requires a great deal of testing in multiple rounds before human trials can begin. I somehow don't think that experimental chemotheraputics, et al can be purchased from the same online outlets.
This will obviously depend on what country we're talking about, but generally, I'd still expect tons of in vitro tests (e.g. applying it to body cells in a lab), then in vivo tests with e.g. mice and then a few tests with humans who've signed a contract, before such a chemical can be sold anywhere close to the free market.
Even if people volunteer for it, you can't just poison them...
AbsolutelyNotCats is (probably) talking about some of not-yet-banned compounds predicted to have some recreational properties, sold as a "research chemicals" because these are not and will be not tested. people like DMT or 2C-B? slap a methyl here or hydroxyl there and you're good to go with selling this because it's not illegal to do so. you can't call this thing as safe or pharmaceutical or anything else, because it's not tested this way
there are also CROs that will make a panel of compounds of your choice that you then test in some high-throughput screening and these are legit, non-sketchy companies that do participate in pharmaceutical design. that's entirely different thing
i hate to be the one that tells you this, but some rando cooking tryptamines in garage is not the kind of "research chemicals" that legit drug research uses. these are called CRO, contract research organizations and that would be Enamine ltd most of the time, they can make a wide array of compounds on demand. legit labs can get whatever they need (with appropriate paperwork), either as material for in vivo/in vitro testing or analytical standard
sometimes people get paid for participating in phase 1 trials, not the other way around