There is an audio interview with Aubrey de Grey (SENS Research Foundation) and Brian Kennedy (Buck Institute for Aging Research) in which that is discussed in some detail.

http://mendelspod.com/podcasts/brian-kennedy-and-aubrey-de-g...

See the "response to Calico and HLI" portion.

With reference to Calico, the relevant part is this:

"I would say that definitely their hearts are in the right place, but they are a regular, perfectly normal company. They want to make profits fairly soon. Calico have set themselves up as a completely unusual company with the goal of doing something very long-term, however long it takes, they want to actually fix aging. They said so - Larry Page was perfectly clear about that. The question is how are they going about it, and that's getting really interesting. The first thing that they've done, which I feel is an absolutely spectacularly good move, is to bifurcate their work into a relatively short-term track and a long-term track. The short term track involves drug discovery for age-related diseases, doing deals with big companies like Abbvie, and so on. That's all very wonderful and all very lucrative in the relatively short term, and has more or less nothing to do with the mission for which Calico was set up - but it is a fabulous way to insulate the stuff that they do that is to do with why Calico was set up from shareholder pressure. It gets a little more complicated though. So then on the long term side, the stuff being led by David Botstein and Cynthia Kenyon, the question is how are they going about their mission. Of course an awful lot of this unknown because they are a secretive company, but from the perspective of whom they are hiring, and what kinds of work those people have done in the past, one can certainly say that they are not just focusing on one approach. They are interested in diversity. My only real concern is that they may be emphasizing a curiosity-driven long term exploratory approach to an unnecessary degree. I'm all for finding out more and more about aging, but I'm also all for using what we've already found out to the best of our ability to try stuff and see what we can do. I should emphasize that this is only my impression from a very limited amount of information available, but my impression is that it is perhaps turning into an excessively curiosity-driven, excessively basic science, inadequately translational outfit. And that's kind of what I feared when Botstein came along in the first place, because he's on record as saying he doesn't have a translational bone in his body."

The basic point is that they appear to be aiming at drug development to slow aging, which is very hard and speculative. The basic goal is to create a new global metabolic state that ages more slowly than the natural one. The calorie restricted state is an obvious one to try emulating, but that is also very hard: understanding sufficient to do this requires a complete map of cellular biology. More than a decade of research into sirtuins, and a billion dollars in investment, went nowhere for example. That was classed as a promising direction at the outset, and much hyped. But what if you did create a new metabolic state? The outcome would be a small increase in life span, a small slowing in aging, and a therapy that would be useless for old people because they are already damaged.

Compare that with the SENS repair approaches, such as removal of senescent cells, which is already producing far more robust results in mice, and at a fraction of the cost. Such therapies can be used over and again, and produce new benefits each time to the degree that they clear out damage. They are also useful and beneficial for old people, as they will reduce their damage load.

So in short, we can do the slow, expensive, useless path, or the fast, cheap, effective path. So far the research community has chosen the former. Why they have done this is a long, long cultural discussion on incentives and regulation and the nature of how research into age-related diseases has typically worked over the last century. What will change this is a continuing set of convincing animal data from SENS programs.