# 1/2: CO2 Reactivity as a Biomarker of Non-response to Exposure-based Therapy > **NIH NIH R01** · UNIVERSITY OF TEXAS AT AUSTIN · 2024 · $723,040 ## Abstract PROJECT SUMMARY/ABSTRACT Exposure-based therapy is an effective first-line treatment for anxiety-, obsessive-compulsive and trauma- and stressor-related disorders. 1–6 However, many patients fail to respond or achieve remission with exposure- based therapy, 7–11 resulting in “unnecessary” prolonged suffering, loss of productivity, and poorly used resources. Making available a biomarker assay that can aid clinicians and patients in treatment selection has the potential to have considerable public health impact. Basic research on fear extinction - a core mechanism of action of exposure-based therapy - may inform the development of a biomarker for the selection (yes/no) of exposure-based therapy. Growing evidence links 12,13 14–16 orexin system activity to deficits in fear extinction.17–20 Our group has demonstrated that reactivity to CO2 challenge, which is a safe, affordable and easy-to-implement procedure, can serve as a proxy for orexin system activity and predicts fear extinction deficits in rodents.21 Building upon this basic research, the goal for the propo sed study is to validate CO2 reactivity as a biomarker of exposure-based therapy non-response. To this end, we will assess CO2 reactivity in 600 adults meeting for one or more fear- or anxiety-related disorders prior to providing open, state-of-the art, transdiagnostic exposure-based therapy. By incorporating CO2 reactivity into a multivariate model predicting treatment non-response that also includes reactivity to hyperventilation as well as a number of related and theoretically-relevant prognostic variables, we will establish the mechanistic specificity and the additive predictive value of the putative biomarker. By developing models independently within two study sites and predicting the other site's data, we will validate that the results are likely to generalize to future clinical samples. The proposed study represents a necessary stage in translating basic research to strategies for treatment selection. The investigation addresses an important public health issue by testing an accessible clinical assessment strategy - informed by basic research - that may lead to a more effective treatment selection (personalized medicine) for patients with anxiety- and fear-related disorders and enhance our understanding of the mechanisms governing exposure-based therapy. ## Key facts - **NIH application ID:** 10813805 - **Project number:** 5R01MH125951-03 - **Recipient organization:** UNIVERSITY OF TEXAS AT AUSTIN - **Principal Investigator:** Marie H. Monfils - **Activity code:** R01 (R01, R21, SBIR, etc.) - **Funding institute:** NIH - **Fiscal year:** 2024 - **Award amount:** $723,040 - **Award type:** 5 - **Project period:** 2022-05-01 → 2027-02-28 ## Primary source NIH RePORTER: https://reporter.nih.gov/project-details/10813805 ## Citation > US National Institutes of Health, RePORTER application 10813805, 1/2: CO2 Reactivity as a Biomarker of Non-response to Exposure-based Therapy (5R01MH125951-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10813805. Licensed CC0. --- *[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*