Updated May 2026 · ClinicalTrials.gov
Supplementing L-citrulline to Overweight Late Asthma oNset Phenotypes
Supplementing L-citrulline to Overweight Late Asthma oNset Phenotypes to Increase Airway L-arginine/ADMA Ratio and Improve Asthma Control
Supplementing L-citrulline to Overweight Late Asthma oNset Phenotypes (NCT03885245) is a Phase 2 interventional studying Asthma and Obesity, sponsored by University of Colorado, Denver. RECRUITING as of the most recent ClinicalTrials.gov update. Talk to your doctor before contacting the trial site.
About This Trial
Patients with obese late onset (after childhood) asthma can have lower FeNO levels, yet be highly symptomatic and poorly responsive to inhaled steroids. This is a common asthma phenotype, particularly among females. This reduction of NO occurs through increased arginase activity and uncoupling of NO synthase (NOS), by accumulation of asymmetric di-methyl arginine (ADMA), which further lowers the L-arginine/ADMA ratio, preferentially promoting reactive oxygen species (ROS) formation and inflammation at the expense of NO. Indeed, in patients with obese late onset asthma, lower L-arginine/ADMA plasma ratios are associated with reduced FeNO, increased bronchial hyperreactivity, and greater asthma morbidity. In our pilot studies, the administration of L-citrulline, as an L-arginine donor, to patients with obese late onset asthma increased the L-arginine/ADMA ratio, FeNO levels, and improved asthma control and lung function. Therefore, the objectives of the protocol are to: a) determine the efficacy of L-citrulline, as an add-on treatment to improve the asthma control and lung function in obese late onset asthmatics; b) leverage the use of asthmatic and control cells to further understand obesity-related changes in epithelial airway NO metabolism, and how these changes relate to bronchoconstriction and lung function, c) determine airway epithelial changes in mitochondrial function and bioenergetics in obese late onset asthmatics and how these are modified by L-citrulline. To do this, 54 obese late onset asthmatics with suboptimal control will be blindly randomized, in a cross over study, comparing 15g/day of L-citrulline vs. placebo, in two 8-week treatment periods with a 6-week washout in between. The co-primary study outcomes are asthma control (ACQ, ACT) and FeNO, and secondary endpoints plasma L-arginine/ADMA, FEV1 and PC20 methacholine. Parallel to this study, a small study of 10 healthy obese controls will receive open label L-citrulline for 7 weeks to establish comparative reference values for the study aims. During the initial treatment phase, 50% of study participants will be randomly allocated to undergo pre and post L-citrulline treatment bronchoscopy to obtain BAL and airway epithelial cells. The research group proposing this study is highly experience in asthma clinical trials, implementation of cross over design studies, and in the use of research bronchoscopies.
What Stage of Research Is This?
Phase 2 trials evaluate whether a treatment actually works against Asthma and continue monitoring side effects. Phase 2 enrolls larger groups (typically 100–300 patients) and produces the first real efficacy signal. A successful Phase 2 readout is what unlocks the much larger Phase 3 confirmatory trials needed for FDA approval.
This trial is currently recruiting participants. The sponsor has registered the study with ClinicalTrials.gov as actively enrolling, which means new applicants who meet the eligibility criteria can be considered for screening. Trial status can change between updates — confirm current recruiting status with the study contact before traveling for a screening visit.
Target enrollment of 60 participants puts this in the typical range for a Phase 2-style efficacy study or a moderate Phase 3 trial in a focused Asthma subpopulation. At this scale, the study has enough statistical power to detect a clear treatment effect but is not the largest cohort in the field.
Who May Be Eligible (Plain English)
These are translations of the protocol\'s inclusion and exclusion criteria, simplified for patients and caregivers. The original clinical text appears below. Eligibility is ultimately confirmed by the trial site\'s screening process — this summary is a starting point for a conversation with your doctor, not a final determination.
Original Eligibility Criteria
View original clinical language
Treatments Being Tested
L-ctirulline
7 weeks of treatment with 15 g/day of orally administered (powder form mixed with water) L-citrulline
Matching Placebo
7 weeks of treatment with orally administered matching placebo (to 15 g/day of L-citrulline)
Locations (1)
Trial sites listed on ClinicalTrials.gov for this study. Site activation status can vary — confirm with the specific site before traveling for a screening visit.
How to Talk to Your Doctor About This Trial
Bring the printable summary of this trial — including the NCT ID (NCT03885245), the sponsor (University of Colorado, Denver), and the key eligibility criteria — to your next appointment. Your doctor can review the inclusion and exclusion criteria against your medical history, lab values, and current treatments to assess whether you are likely to qualify. They can also help you weigh whether trial participation makes sense alongside your existing care plan.
Useful questions to walk through together: What does the trial protocol require beyond standard care? How long is the active treatment phase, and how long is follow-up? Are there study visits at sites I can reach? Who pays for the trial-specific procedures, and who pays for standard-of-care portions? See our 25 questions to ask about clinical trials guide for a more complete checklist.
Authoritative Sources
The official record for this trial lives on ClinicalTrials.gov — the federal registry maintained by the National Library of Medicine at NIH. For background on how this trial fits into the FDA approval pathway, see the FDA drug approval process. For oncology-specific guidance for patients considering trials, the National Cancer Institute publishes patient-oriented overviews. International trial registries are aggregated by the WHO ICTRP.
Frequently Asked Questions
What is the NCT03885245 clinical trial studying?
Patients with obese late onset (after childhood) asthma can have lower FeNO levels, yet be highly symptomatic and poorly responsive to inhaled steroids. This is a common asthma phenotype, particularly among females. This reduction of NO occurs through increased arginase activity and uncoupling of NO synthase (NOS), by accumulation of asymmetric di-methyl arginine (ADMA), which further lowers the L-arginine/ADMA ratio, preferentially promoting reactive oxygen species (ROS) formation and inflammation at the expense of NO. Indeed, in patients with obese late onset asthma, lower L-arginine/ADMA pl… The full protocol is registered on ClinicalTrials.gov and includes the primary outcome measures, eligibility criteria, and study endpoints.
Who can participate in NCT03885245?
Eligibility for this trial depends on the specific inclusion and exclusion criteria set by the sponsor. The plain-English summary above translates the most important criteria into accessible language; the official clinical text is preserved in the collapsible section underneath. Whether you fit any specific trial is a medical decision your doctor needs to confirm — bring the trial information to your treating physician for a full review against your medical history.
How do I contact the trial site for NCT03885245?
Contact information registered with ClinicalTrials.gov is shown in the sidebar of this page. Before reaching out, confirm with your treating physician that this trial is appropriate for your situation. The trial site will then walk you through the screening process to determine final eligibility.
Is participating in a clinical trial safe?
Clinical trials in the United States are regulated by the FDA and overseen by Institutional Review Boards (IRBs) that review the protocol for safety. Risk varies by trial — Phase 1 studies test new treatments in humans for the first time, while Phase 3 trials use treatments that have already passed earlier safety screening. The informed consent document for any specific trial details the known risks and what to expect. Discuss those risks with your physician before deciding whether to participate.
Where can I verify the data on this page?
Every detail on this page comes directly from the ClinicalTrials.gov API. Click "View on ClinicalTrials.gov" in the sidebar to see the official, unmodified record. The federal record is always authoritative; this page is a structured presentation with a plain-English eligibility translation. For background on how clinical trials are regulated, see the FDA drug approval process documentation.
How This Page Is Built
Every field on this page is pulled directly from the ClinicalTrials.gov API v2 — no estimates, no proxies. The plain-English eligibility translation is generated from the original protocol text and reviewed for fidelity to the underlying clinical criteria. The original clinical text remains visible in the collapsible section above so users and clinicians can verify the translation. Read the full methodology for the data pipeline and known limitations.
Source: ClinicalTrials.gov API v2 record for NCT03885245. Maintained by the National Library of Medicine at NIH. Public domain. Cite as: "TrialFinderData. NCT03885245. Data: ClinicalTrials.gov."
Medical disclaimer: This page is informational, not medical advice. Talk to your doctor about whether a clinical trial is right for you.
Last updated 2026-05-08 · Data from ClinicalTrials.gov.