Hi Shoba, Good question! Generally, applicants have to submit to either an SBIR or STTR solicitation for an NIH Fast Track. There have been rarely targeted solicitations that allow STTR in Phase I and SBIR in Phase II. Here is an example: https://grants.nih.gov/grants/guide/rfa-files/RFA-CA-21-001.html, but it is expired. However, applicants can switch mechanisms between two Phases. For example, apply for SBIR in Phase I and apply for STTR for Phase II, vice versa. However, there will be a funding gap between the two Phases. If you have additional questions, please feel free to reach out. -Lu
