What FDA’s record states
| Field | What FDA’s record states | Source |
|---|---|---|
| Recipient | Ralph A. DeFronzo, M.D. | FDA letter ↗ |
| Location | San Antonio, TX | FDA letter ↗ |
| Letter date | Sep 17, 2025 | FDA letter ↗ |
| Posted by FDA | Sep 23, 2025 | FDA index ↗ |
| Issuing office | Center for Drug Evaluation and Research (CDER) | FDA letter ↗ |
| Subject | Clinical Investigator/Sponsor | FDA letter ↗ |
| MARCS-CMS number | 716773 | FDA letter ↗ |
| GLP-1 drugs named | GLP-1 (named in the letter, no specific drug) | FDA letter ↗ |
| Response letter | Not published by FDA | FDA letter ↗ |
| Closeout letter | Not published by FDA | FDA letter ↗ |
“For example, all versions of the protocol that was in effect at the time all seven subjects enrolled, required the following inclusion criteria to be eligible for enrollment in the study: blood pressure ≤ 145 / 65 mmHg estimated glomerular filtration rate (eGFR) > 45 ml/min/1.73m² Furthermore, the eligibility criteria for Protocol (b)(4) required subjects who were treated with glucagon-like peptide-1 (GLP-1) receptor agonists or thiazolidinediones, and with sodium-glucose transport protein 2 (SGLT2) inhibitors, to be excluded from participation in the study.”FDA warning letter to Ralph A. DeFronzo, M.D., Sep 17, 2025 · read the full letter on fda.gov ↗
What this is and is not.A warning letter is FDA’s statement of what it considers significant violations. It is an allegation, not a court finding, and the firm can respond. A closeout letter is posted when FDA confirms the violations were corrected.
Source
Every field above is copied from FDA’s page for this letter, read Oct 3, 2026. The letter on fda.gov ↗ · All 161 GLP-1 warning letters