Exhibit 21.1

Oscient Pharmaceuticals Corporation & Wholly-Owned Subsidiaries

1. Oscient Pharmaceuticals Corporation

• Organized under the laws of Massachusetts

• Registered as a foreign entity in New Jersey

2. Genesoft Pharmaceuticals, LLC

• Organized under the laws of Delaware

• Registered as a foreign entity in California

3. Guardian II Acquisition Corporation

• Organized under the laws of Delaware

• Registered as a foreign entity in Massachusetts.

4. Collaborative Securities Corporation

• Organized under the laws of Massachusetts

5. Collaborative Genetics, Inc. MA

• Organized under the laws of Massachusetts

6. Oscient Pharmaceuticals UK, Ltd.

• Organized under the laws of the United Kingdom