Shares of a tiny biotech company developing a prostate cancer drug rocketed by more than 400% over the past year even though it’s years away from a commercial product. Another small biotech stock plunged 69% in a single day after that company’s bone marrow treatment failed in clinical trials.

Small biotech stocks tend to experience wild ups and downs because of the nature of their business, but over time, the sector does very well. Even if the ever-present possibility of a flameout poses greater investment risk than you are comfortable with, you still can participate in the biotech revolution.

There are at least 10 mature biotech firms with market capitalizations of more than $10 billion each that ­already have FDA-approved products on the market providing steady revenue. These companies are better able to withstand setbacks than smaller biotechs are, yet still fund the development of new drugs.

Here are two well-­established biotechs that have been selling at attractive valuations…

Amgen (AMGN), with a $123 billion market capitalization, is the largest US biotech. Its blockbuster drugs include Enbrel (for arthritis), Prolia (osteoporosis) and Repatha (cholesterol). Though some of its drugs will lose market share to generics, Amgen has recently recieved approval for Aimovig, a migraine drug that could offset some of that loss.

Biogen (BIIB) has achieved strong profitability on the success of four drugs, each with more than $1 billion in annual sales. Its Rituxan remains the standard of care for hematological cancer, and Avonex, Tysabri and Tecfidera dominate the multiple sclerosis market. Biogen’s deep neuroimmunology pipeline includes a drug to treat Alzheimer’s that is in late-stage clinical trials.