In the second quarter, Berkshire said it exited a $180 million stake in Biogen Inc and reduced investments in Abbvie Inc, Bristol-Myers Squibb Co and Merck.
It also shed a $411 million stake in paint maker Axalta Coating Systems Ltd, a Berkshire holding since 2015.
The changes were disclosed in a regulatory filing detailing Berkshire's U.S.-listed holdings as of June 30.
Berkshire has been a net seller of stocks in 2021, including in the second quarter when it sold $1.1 billion more stocks than it bought.
That suggests Buffett and his investment managers Todd Combs and Ted Weschler remain wary of valuations as stock prices regularly set new highs.
The Standard & Poor's has doubled from its March 2020 trough early in the COVID-19 pandemic.
Berkshire has instead bought back about $14.3 billion of its own stock between January and late July though its share price also set records, and now sits just 2% below its May 7 peak.
The Omaha, Nebraska-based conglomerate ended June with $144.1 billion of cash and equivalents. Berkshire also owns dozens of businesses including the BNSF railroad, Geico auto insurance and Dairy Queen ice cream.
Organon specializes in contraception and other women's health products, and has dozens of brands in other fields.
Berkshire reported a $46.9 million Organon stake as of June 30.
Its largest investments on that date were $124.3 billion in Apple Inc and $42.6 billion in Bank of America Corp.
In Monday's filing, Berkshire also reported lowered stakes in Chevron Corp, General Motors Co, media company Liberty Global Plc, insurance broker Marsh & McLennan Cos and US Bancorp.
It reported increased stakes in supermarket chain Kroger Co, home furnishings chain RH and Marsh rival Aon Plc, which under regulatory pressure called off a $30 billion merger with Willis Towers Watson Plc last month.
(Reporting by Jonathan Stempel in New York, Editing by Rosalba O'Brien and Richard Pullin)
By Jonathan Stempel