I audited pharma facilities and worked closely with the FDA. The FDA has to approve the methodology. Manufacturing in an approved facility is a hell of a lot easier but before any product can be shipped the FDA has to inspect the plant specifically for the manufacturing of these products.

I worked in such a facility and hosted these inspections often as well as conducted audits to ensure we were always audit ready.

But yes... I would not recommend a new pharma company try to build a manufacturing facility themselves... way to much time, energy, and red tape. Contracting out the formulation and packaging is so much easier.... Because lets not forget... the FDA has to sign off on the packaging also..