The other commenter isn’t completely correct, at least with modern techniques – optimisation of the drug during its development can involve altering its structure to (typically) increase its half-life.
For some drugs, you can make it more lipophilic by changing out atoms – for instance, swapping out hydrogen for fluorine. This means it binds better to tissues, so it isn’t as easily flushed away by the kidneys or broken down in the liver. [Source](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6004573/)
For large protein biologics used as medicine, if you make them large enough they won’t be removed by the kidneys. You can also add polyethylene glycol which makes them more immune tolerant so they aren’t removed that way, or by adding human serum albumin, which makes them more resistant to being broken down by enzymes called proteases, as well as being a big molecule that isn’t removed by the kidneys as easily. [Source](https://www.sciencedirect.com/science/article/pii/S0753332219301623)
To add serum albumin you can add lipids (long molecular chains) to the drugs (such as insulin) so that they “stick” to the albumin in your body once the drugs are taken in and absorbed. [Source](https://pubs.acs.org/doi/10.1021/acsmedchemlett.8b00226#)
Hope this helps!
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