The point is, when you do an en vitro test with positive results, you continue to the next stage of testing. Funding becomes an issue, however interest in corona viruses was high due to SARS and subsequently Swine Flu and Avian Flu. Why subsequent testing wasn't performed becomes an interesting question. Typically any natural substance that is found to have therapeutic effects are tested initially in a published paper. Subsequent further testing to determine the active ingredient is performed. The chemical composition is then synthesized and tested. If the tests replicate the therapeutic effect, the new drug is patented and undergoes clinical trials. Most synthesized replicants typically have adverse side effects not found in the natural remedy. This is thought to be because of mitigating "inactive" ingredients in the original natural sourced substance. This requires further analysis to determine what other compounds are needed to minimize side effects and then retry clinical trials. The original naturally occurring substance is rarely tested further, at least not with any published papers. This is due to the lack of monetary compensation for the extremely expensive and arduous process of developing, testing and approving any RX grade substance. HCQ could possibly have many off label uses. At this time only Lupus and RA are regularly prescribed. These were anecdotal, but the massive amounts of documented cases of positive results were substantial enough for it to be mainstream and accepted. During an emergency, the use for treating with HCQ was done, but with far higher doses than were known to be safe were utilized. The Oxford study should have posted the dosages given. If it did, no one flagged the fact it was over 12 times the recommended dosages.