GHGuardant Health, Inc.

Guardant Health looks for tumour DNA in an ordinary blood sample — instead of a biopsy.

A tumour sheds fragments of its DNA into the blood, and from them the mutations that determine treatment choice can be identified. Previously that required a piece of tissue, and a biopsy is not always possible and always invasive. A blood test makes therapy selection faster and can be repeated as treatment proceeds.

The lines are expanding: monitoring residual disease after surgery and screening healthy people for colorectal cancer. The economics depend not on the science but on reimbursement: until an insurer covers a test, the laboratory runs it at close to a loss. Risks: coverage decisions, competition and a need for capital. The company pays no dividend.