If LP 533401, drug that inhibiti gut serotonin used in prepubertal people, will it produce bigger bone as it aid in bone formation?

Wow. This is a really sophisticated question. But you are jumping the gun. The drug is at a research level, without wider testing. One simply can't tell for sure whether it will have the expected effects, on which population, with what risk of side effects. And it may not make it to the marketplace.