Enhancing Mechanistic Research on Precision Probiotic Therapies (R33 Clinical Trial Optional) | PAR 24 239

Opportunity Information: Apply for PAR 24 239

The NIH funding opportunity PAR-24-239, titled "Enhancing Mechanistic Research on Precision Probiotic Therapies (R33 Clinical Trial Optional)," is designed to push probiotic research past broad, one-size-fits-all approaches and toward precision interventions that work reliably in real people. The central problem the NOFO is trying to solve is that probiotic responses in humans are often inconsistent and hard to reproduce, largely because people differ in many biologically meaningful ways. This program focuses on mechanistic research that can explain why a probiotic helps one subgroup but not another, and how that knowledge can be used to improve outcomes by matching probiotic strategies to the right individuals or biologic profiles.

The NOFO specifically solicits R33 applications that build on existing signals and preliminary evidence. In other words, it is not mainly intended for projects that are still fishing for potential response factors from scratch. Instead, it supports projects where investigators already have supportive preliminary data suggesting that certain host biological patterns or person-specific features are correlated with probiotic response, and now need rigorous mechanistic work to test whether those patterns are causal, predictive, or both. A key emphasis is moving from correlation to mechanism: clarifying the biological pathways that link host factors to probiotic colonization, persistence, function, immune effects, metabolic effects, or clinical benefit. If a team is earlier in the pipeline and still trying to identify candidate host patterns that might matter, NIH points them toward the companion R61/R33 opportunity (PAR-AT-24-XXX, TEMP-25412) intended for that earlier discovery stage.

What the program is looking for scientifically is research that characterizes and tests person-specific features that influence probiotic responsiveness and then uses that insight to define subgroups of responders. Examples of host features the NOFO highlights include the native microbiome, immune system status and function, sex or gender-related biology, diet, age, genetic background, lifestyle factors, and health history. The underlying idea is that these factors shape the intestinal environment and host physiology in ways that can either enable or block a given probiotic strain or consortium from exerting its intended effect. A strong application, therefore, would not just measure these features, but would connect them to plausible mechanisms, testable hypotheses, and experiments capable of distinguishing cause from coincidence.

Methodologically, the NOFO emphasizes rigorously designed mechanistic studies conducted either in humans or in relevant and innovative animal models. The expectation is that applicants will use experimental designs that can actually interrogate mechanism, such as carefully controlled interventions, validated biomarkers, functional assays, multi-omics approaches linked to hypotheses, or models that allow targeted manipulation of host variables. Because the title indicates "Clinical Trial Optional," applicants may propose studies that include clinical trials if appropriate, but they are not required to run a clinical trial to be responsive. The key requirement is that the work is mechanistic and clearly aimed at understanding and overcoming barriers to precision probiotic therapies, rather than simply demonstrating that a probiotic has some effect in a broad population.

From a practical translation standpoint, the NOFOs ultimate goal is to generate knowledge and strategies that make probiotic interventions more reliable by accounting for human heterogeneity. That can mean identifying biological signatures that predict who will benefit, clarifying why certain people do not respond, and developing approaches to improve response rates or effect sizes, such as selecting specific subgroups, tailoring dosing or formulation, pairing probiotics with dietary components, or addressing host conditions that interfere with probiotic activity. The program is essentially trying to lay the mechanistic foundation for precision probiotic use, where the right microbial therapy is matched to the right host context.

Eligibility is broad and includes many types of domestic organizations: state, county, city, township, and special district governments; independent school districts; public and state-controlled institutions of higher education; private higher education institutions; nonprofit organizations with or without 501(c)(3) status (excluding higher education when specified); for-profit organizations (other than small businesses); small businesses; public housing authorities; and Native American tribal governments (federally recognized) as well as other tribal organizations. The NOFO also explicitly encourages participation from institutions and organizations that serve populations historically underrepresented in biomedical research or that have specific community missions, including Alaska Native and Native Hawaiian Serving Institutions, AANAPISISs, Hispanic-serving Institutions, Historically Black Colleges and Universities, Tribally Controlled Colleges and Universities, faith-based or community-based organizations, regional organizations, and U.S. territories or possessions, among others. While foreign organizations are not eligible to apply directly, foreign components as defined by NIH policy are allowed, meaning a U.S.-based applicant may include certain international elements if they meet NIH rules and are well-justified.

Administratively, this is an NIH discretionary grant mechanism under an R33 funding instrument. The NOFO is associated with CFDA numbers 93.121, 93.213, 93.313, 93.393, and 93.866, reflecting its placement within NIH programs. The original closing date listed is June 2, 2027, indicating a multi-year window for submission cycles typical of NIH parent and special-interest announcements. The award ceiling and expected number of awards are not specified in the provided listing, which usually means applicants should rely on the full NOFO text and NIH Institute/Center-specific budget guidance when planning project scope and budgets.

In short, PAR-24-239 is aimed at teams that already have promising preliminary links between host biology and probiotic response and are ready to do the hard mechanistic work needed to prove what drives responsiveness, identify responder subgroups, and develop practical strategies to reduce inconsistent outcomes. The program is fundamentally about turning probiotics into precision tools by understanding the biology of who responds, why they respond, and how to design interventions that perform predictably across diverse human populations.

• The National Institutes of Health in the education, health sector is offering a public funding opportunity titled "Enhancing Mechanistic Research on Precision Probiotic Therapies (R33 Clinical Trial Optional)" and is now available to receive applicants.
• Interested and eligible applicants and submit their applications by referencing the CFDA number(s): 93.121, 93.213, 93.313, 93.393, 93.866.
• This funding opportunity was created on 2024-06-17.
• Applicants must submit their applications by 2027-06-02.
• 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 24 239

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