Just my opinion, FDA likes to have more than one site to diversify the treatment group, lessening the chances for findings not reflective of the overall population. But recall that the 120 is only for a P 2. We can expect hundreds more for the P 3 to be required. Others posting here have shown examples of much less than the tens of thousands required of P 3s for vaccines, being required for non-vaccine studies. Glad for that, as it readjusted my (our) beliefs, making them more accurate.