This might be a more intuitive framework for drug trial phases.

Phase 1 / First you give only to healthy people. You cannot test a new therapy on individuals who are already “sick.” How would you distinguish adverse drug effect from complication of the disease? In the beginning you simply have to prove that the drug doesn’t cause problems in normal individuals. You can’t prove that if your initial study includes “non-normal” humans.

Phase 2 / Second, you give only to the sick. This lets you to determine if the drug has any benefit whatsoever in the intended audience. If it does not provide benefit, there is “no reason” to advance to the next stage.

Phase 3 / Third, you must prove that the drug not only provides a benefit but is actually better than the current standard. (“Head-to-head” trial; random controlled trial.)

Phase 4 / If you pass the third stage, you can release your product to market but must surveil for longterm effects which could not be captured by the earlier, shorter-stage phases.

Don't look too hard into it. the stem says "RECENTLY MARKETED" the SWIM mnemonic:

M: Marketed drugs - phase 4

classic mistake I made by not reading properly/ overthinking

From centerwatch.com (never heard of it before but seems like a good explanation):

"Phase IV studies, often called Post Marketing Surveillance Trials, are conducted after a drug or device has been approved for consumer sale. Pharmaceutical companies have several objectives at this stage: (1) to compare a drug with other drugs already in the market; (2) to monitor a drug's long-term effectiveness and impact on a patient's quality of life; and (3) to determine the cost-effectiveness of a drug therapy relative to other traditional and new therapies. Phase IV studies can result in a drug or device being taken off the market or restrictions of use could be placed on the product depending on the findings in the study."