What is the difference between an R21 and R33 research project grant?

The R21 mechanism is meant to support research projects in which proof-of-principle has not yet been established. The aim of such an award is thus to acquire, through the completion of a series of quantitative performance measures, sufficient data to demonstrate proof of principle. IMAT R21s are intended to encourage new exploratory and pilot research projects. Proposed projects are expected to be novel. The technology proposed should be at the inception, conceptiual stage and may involve considerable risk but could lead to a breakthrough in a particular area that could have a major impact on cancer research. The IMAT R21 FOAs limit direct costs to $400,000 total for up to 3 years.

The R33 mechanism is meant to support research projects that are more developmental in nature and should be predicated upon the establishment of proof-of-principle through prior research. An IMAT R33 project may or may not have been previously supported by an exploratory IMAT R21 grant. IMAT R33s are expected to generate sufficient data to fully validate the technology in a biologically relevant setting and demonstrate its full utility in addressing biological, translational, clinical, and/or epidemiological questions. The IMAT R33 FOAs limit direct costs to $300,000 per year for up to 3 years.

Specific requirements for each of these types of grants are outlined in the funding overview section of this website and in each of the relevant RFAs.