Are you a shareholder or something?
It's not that complicated. Setipiprant is currently being tested (at very high dosages that are beyond most people's price range) and we'll learn of the results later this year. We'll see how well it does on its own over a 24-week period. We'll see how well it regrows hair, and what the side effect profile is. There are some posters who have tried setipiprant and reported null results, which suggests that it won't work for everybody.
Cetirizine is a different molecule. It has a different amplitude of effect, a different mode of action(s), it has other effects as well, and a different level of systemic penetration. The study on cetirizine was also one where the treatment was a topical one, rather than a pharmaceutical. The study also reported no side effects, which is wonderful if it holds up. In contrast, setipiprant will almost certainly affect mood and personality, as PGD2 plays a significant role in the brain.
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PGD2 is not the only molecule elevated in the scalps of balding men, nor is it the case of prostaglandins are never the consequence of other developments, don't post pseudoscience. For example, it's well-known that balding scalps contain more androgen receptors:
https://www.ncbi.nlm.nih.gov/pubmed/9496234
Balding men don't have more DHT -- that's well known. Some studies suggest that they might even have less DHT. What they do have is a different sensitivity to DHT. The higher rates of heart disease and prostate cancer suggest that the androgen receptors may be disproportionate elsewhere in the body as well.