A California biotech company headed by Michael West, a prominent scientist and entrepreneur involved in stem cell research, plans to supply scientists working with stem cells the tool they most need to develop and test novel therapies--a reliable and reproducible source of the cells.

Stem cells hold great promise for medicine, both as a potential source of replacement cells for damaged organs and as a scientific resource to study disease and develop and test new drugs. But to realize that promise, scientists have to figure out how to make their products on an industrial scale. "It's clear we'll need a much better strategy for reliably and reproducibly generating large numbers of specific cell types," says Arnold R. Kriegstein, director of the Institute for Regenerative Medicine at the University of California, San Francisco. "Most studies until now have stopped short of doing this."

The very qualities that make stem cells so desirable--the ability to self-replicate and develop into many types of cells--can also make them difficult to control. For example, two cell lines produced the same way but from different starting materials don't always behave the same, a property that's essential for both cell-based therapies and scientific studies.

West, CEO of BioTime and its subsidiary, Embryome Sciences, plans to sell lines of cells that he dubs "human embryonic progenitors"--cells that have inched partway along the continuum from embryonic stem cell to differentiated adult cell. West and collaborators published a paper last week describing their efforts to generate cells that reproduce only the same type of cells, theoretically creating a better-defined cell product.

In the early 1990s, West cofounded Geron, a biotech company based in Menlo Park, CA, that was originally focused on developing treatments for age-related diseases and is now developing embryonic stem cell-based therapies for spinal cord injury and other diseases. (Geron supported early research at the University of Wisconsin, where human embryonic stem cells were first isolated, and licensed crucial patents from the university.) Prior to joining BioTime, West headed Advanced Cell Technologies, a Los Angeles-based company that is also developing embryonic stem cell-based therapies, as well as new ways to generate embryonic stem cells.

West's latest career move--to head a company developing tools for the field rather than the therapies themselves--reflects in part a maturation of stem-cell medicine as a whole. Greater numbers of scientists are moving into this area of research, and their expertise may lie in neurology or cardiology, rather than in stem cell biology. "It's an interesting business model," says Evan Snyder, director of the Stem Cell Research Center at the Burnham Institute in La Jolla, CA. "I could clearly see a customer base in scientists who simply see stem cells as a way of providing lots of cells for their use." For example, scientists who want to screen new drugs for Parkinson's disease would ideally like to have a large number of dopamine neurons, the cell type affected in the disease.