Discovery of Cell-based Chemical Probes for Novel Brain Targets (R21 Clinical Trial Not Allowed) | PAR 21 028

Opportunity Information: Apply for PAR 21 028

The NIH funding opportunity PAR-21-028, titled "Discovery of Cell-based Chemical Probes for Novel Brain Targets (R21 Clinical Trial Not Allowed)," supports early-stage, high-impact projects focused on creating and refining small-molecule chemical probes that work in cell-based systems. The central goal is to accelerate the development of new tools that researchers can use to interrogate brain biology and disease mechanisms, particularly in areas aligned with the missions of NIMH, NIA, NICHD, and NIDCD. Rather than emphasizing clinical translation or patient studies, this announcement is aimed at generating practical, well-characterized probe compounds that can reveal how specific targets and pathways function in brain-relevant contexts.

A key expectation is that applicants are not starting from scratch. Projects should begin with "validated hits," meaning the research team already has initial compounds with credible activity against a target of interest, along with established bioassays capable of evaluating new analogs. The funded work is therefore positioned as a chemical optimization and validation effort: improving potency, selectivity, and usability of small molecules and demonstrating their utility as probes in cellular models. The program is particularly interested in efforts that connect probe development to meaningful biological questions, so the most competitive applications are likely to be those where the chemical probe work directly enables new insight into disease-relevant targets or biological processes rather than simply producing a compound library without a strong mechanistic or disease-linked rationale.

The scientific emphasis is explicitly on cell-based chemical probes, which typically means compounds that can be used in living cells to modulate a target and produce an interpretable readout. This often involves demonstrating target engagement and functional effects in relevant cell types, as well as showing that the tool compound is selective enough to support trustworthy biological conclusions. While in vivo probe development can be related, the announcement signals that applicants primarily interested in in vivo chemical probes should consider the companion R01 pathway (referenced as TEMP-8444), indicating that this R21 mechanism is meant to keep the scope tightly focused on cellular systems and early proof-of-concept tool generation.

From an administrative and eligibility standpoint, this is a discretionary NIH grant using the R21 mechanism, and clinical trials are not allowed. The opportunity is broadly open to a wide range of applicant organizations, including public and private institutions of higher education, nonprofits (with or without 501(c)(3) status), for-profit organizations (including small businesses), and multiple levels of government (state, county, city/township, special districts), as well as tribal governments and tribal organizations. The announcement also highlights additional eligible groups such as Historically Black Colleges and Universities, Hispanic-serving Institutions, Tribally Controlled Colleges and Universities, Alaska Native and Native Hawaiian Serving Institutions, AANAPISI institutions, faith-based or community-based organizations, U.S. territories or possessions, regional organizations, and foreign (non-U.S.) entities. The participating NIH components are reflected in the CFDA numbers listed (93.242, 93.279, 93.866, 93.867), corresponding to the institutes and centers whose missions align with mental health, aging, child health and development, and communication disorders.

In terms of funding parameters, the listing shows an award ceiling of $200,000, consistent with the smaller, exploratory nature of the R21 mechanism. The original closing date is given as 2024-01-07, and the FOA record was created on 2020-10-14. Overall, the opportunity is designed for teams that already have a credible starting point (hit compounds and assays) and can rapidly advance those hits into robust, cell-active chemical probes that either illuminate new brain targets or strengthen the biological validation of targets relevant to brain disorders and related conditions within NIH institute priorities.

• The National Institutes of Health in the education, health sector is offering a public funding opportunity titled "Discovery of Cell-based Chemical Probes for Novel Brain Targets (R21 Clinical Trial Not Allowed)" and is now available to receive applicants.
• Interested and eligible applicants and submit their applications by referencing the CFDA number(s): 93.242, 93.279, 93.866, 93.867.
• This funding opportunity was created on 2020-10-14.
• Applicants must submit their applications by 2024-01-07. (Agency may still review applications by suitable applicants for the remaining/unused allocated funding in 2026.)
• Each selected applicant is eligible to receive up to $200,000.00 in funding.
• Eligible applicants include: State governments, County governments, City or township governments, Special district governments, Independent school districts, Public and State controlled institutions of higher education, Native American tribal governments (Federally recognized), Public housing authorities/Indian housing authorities, Native American tribal organizations (other than Federally recognized tribal governments), Nonprofits having a 501 (c) (3) status with the IRS, other than institutions of higher education, Nonprofits that do not have a 501 (c) (3) status with the IRS, other than institutions of higher education, Private institutions of higher education, For-profit organizations other than small businesses, Small businesses, Others.

Apply for PAR 21 028

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