Here's what insiders bought in filings for Sep 14, 2021 — 40 companies and around $2.75 billion in total. At the top: TBIO, $2.74 billion bought, with Sanofi as the largest buyer.
Eight of the buys came from a CEO or CFO. Cluster buying (3+ insiders) is running at 113 companies this month. One buy doesn't make a thesis, but it's a good place to start digging.