From the NIH data sharing FAQs page:
Potential examples of justifiable factors include:
Examples of reasons that would generally not be justifiable factors limiting scientific data sharing include:
From Research Covered Under the Data Management & Sharing Policy:
NIH understands that some scientific data generated with NIH funds may be proprietary. Under the Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) Program Policy Directive, effective May 2, 2019, SBIR and STTR awardees may withhold applicable data for 20 years after the award date, as stipulated in the specific SBIR/STTR funding agreement and consistent with achieving program goals. SBIR and STTR awardees are expected to submit a Data Management & Sharing Plan per DMS Policy requirements.
Issues related to proprietary data also can arise when co-funding is provided by the private sector (for example, the pharmaceutical or biotechnology industries). NIH recognizes that the extent of data sharing may be limited by restrictions imposed by licensing limitations attached to materials needed to conduct the research. Applicants should discuss projects with proposed collaborators early to avoid agreements that prohibit or unnecessarily restrict data sharing. NIH staff will evaluate the justifications of investigators who believe that they are unable to share data.