Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

California cracks down on stem cell cowboys

In October, the governor of California, Jerry Brown, signed into law the country's first bill aimed at tackling unapproved stem cell therapies. The new law, written by Democratic state senator Ed Hernandez, requires clinics offering stem cell therapies to notify patients that the treatment offered has not been approved by the US Food and Drug Administration (FDA). Clinics must also post a notice with this information in their offices, and patients must be handed a paper stating this before they receive the treatment—both notices in a specified size and shape. The statement also recommends patients consult with their physicians before proceeding. California is home to over 100 stem cell clinics, according to a 2016 publication (Cell Stem Cell 19, 154–157, 2016), many presumably offering untested therapies. The FDA has also flexed its muscles in recent months, targeting only two, however, of the hundreds of clinics offering direct-to-consumer stem cell therapies in the US (Nat. Biotechnol. 35, 898–899, 2017). And although some are optimistic given that stem cell clinics are now attracting significant negative attention, others are more cautious. Columnist Michael Hiltzik wrote in the Los Angeles Times that the wording of the new Californian law—that the product has “not yet” [emphasis added] been approved by the FDA—implies that these stem cell therapies are being tested, when in fact many may not be. And then there's Texas. In September, the Texas legislature approved a “right to try” bill for stem cell therapies for patients with severe chronic or terminal illnesses lacking other options. The bill requires that the treatments be overseen by an institutional review board and applies only to those previously tested in humans. Whether these provisions will be upheld in a state that promotes itself as the world's leader in the research and use of stem cells, or simply give license to stem cell cowboys, remains to be seen.

Author information



Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

DeFrancesco, L. California cracks down on stem cell cowboys. Nat Biotechnol 35, 1119 (2017).

Download citation


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing