Biogen The third Buffett stock to avoid like the plague is blue chip biotech Biogen (NASDAQ: BIIB). Part of Kraft Heinz's transformation strategy involves netting $2 billion in gross productivity efficiencies by 2024 to offset inflation and cash needed for other important investments. Biogen is valued at less than 10 times Wall Street's earnings per share consensus for 2021, and it's on track to generate at least $5.3 billion in free cash flow for a third consecutive year in 2020.