Acceleron is developing several other therapies based on this underlying science, including ACE-031 for muscle growth. This therapy will seek to grow muscle in patients by turning off myostatin, or GDF-8, and holds promise to treat ALS (amyotrophic lateral sclerosis) and muscular dystrophy. In this category, it will face stiff competition, with Wyeth and Amgen investing their own research muscle in these promising processes. –JOANNA BREITSTEIN

ANTIBODIES' NEW RIVAL

Adnectins—the fast and mean disease-fighting machine

Today, researchers like Gill are looking into protein-scaffold technologies as a next-generation platform to engineer high-science drugs. "Think of it like origami," says Gill. "You start with a sheet of paper, but then can fold it in many ways. Each shape represents a different function. But that piece of paper is like a template that we can use repeatedly to develop drugs against multiple targets."

Of the scaffolds under research, one of the most promising is adnectins. Adnectins, shaped like the part of an antibody that binds targets, are composed of fibronectin (a human protein that binds to different types of molecular entities). Adnexus Therapeutics, a privately held 40-person shop based in Waltham, MA, has built its research pipeline on this technology and is working to engineer amino-acid sequences to target specific medical conditions.

The company recently signed an agreement with Bristol-Myers Squibb to develop their lead oncologic candidate, Angiocept (CT-322), which is set to enter Phase II trials in late 2007. Angiocept works somewhat like Avastin in that it blocks new blood vessels from forming and supplying tumors with the nutrients to grow. However, Avastin targets just VEGF-A, while Angiocept targets VEGF-A, VEGF-C, and VEGF-D, which may heal patients more completely.

Indeed, the ability to bind to multiple targets means that adnectins offer hope in treating more complex diseases. "For 20 years, we've been trying to figure out how to get an antibody to hit more than one target," says Adnexus CEO John Mendlein. "There are few examples of this because it goes against nature's original design, which is to make an antibody bind to only one thing."

The most promising benefits of this scaffold, however, may be commercial, not clinical. Because adnectins are smaller than antibodies—Gill says they are closer to the "speedboats" of small molecules, compared with the "cruise ships" of large molecules—they are easier to handle. For instance, Adnexus plans to manufacture the proteins in E. coli, a much cheaper method of manufacturer than the one for Avastin, which is produced in Chinese hamster ovary cells.

The company also sees the potential for rapid screening of possible adnectin candidates. Using a proprietary technology, the company can generate trillions of versions of a biologic in a single sample, then, in Mendlein's metaphor, "fish" in it using the target as bait. "It's like a Google search engine for finding a pharmaceutical. We make all these different variations of adnectin and then find the right one that has the affinity, selectivity, immunogenicity, and manufacturing properties that we believe will confer an advantage in the marketplace."

Additional protein-scaffold technologies are in the works. They include compounds built on single-domain antibodies, tetranectins, small modular immunopharmaceuticals, A-domain proteins, ankyrin repeat proteins, and lipocalins. –JOANNA BREITSTEIN

THE 411 ON GLIALS

How does an asthma drug become a medication for neuropathic pain? Alchemy, recycling, or simply smart science?