C21, an angiotensin II type 2 receptor (AT2R) agonist, stabilized and improved lung function in patients with idiopathic pulmonary fibrosis (IPF), according to a press release from Vicore Pharma, the developers of the drug.

The interim results of the phase 2 AIR study (NCT04533022) showed that treatment with C21 stabilized forced vital capacity (FVC) measurements in patients for several months before improving FVC values.

At 24 weeks, the FVC change was +125mL in treated patients compared to an expected decline of -120 mL in untreated patients. The improvements reached clinical significance compared to expected values at 28, 32, and 36 weeks after initiation of C21 treatment (P =.016 at 36 weeks). Out of the 7 patients in the study who completed 36 weeks, 5 continued to show improvement in FVC while the other 2 remained stable.

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“This is very encouraging data to see stabilization in patients over 36 weeks is certainly not something we would expect to see by chance in a clinical trial and definitely warrants further assessment of C21 in IPF,” Toby Maher, clinical expert to Vicore Pharma said.

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The treatment was well tolerated during the study with no related serious adverse events, acute exacerbations, or gastrointestinal signals. Based on these analyses, Vicore plans to initiate a double-blind controlled phase 2 dose-finding study called AIR 2 which will run in parallel to the AIR trial.

“Now that the interim analysis has shown both safety and a positive effect on lung function in this trial, we want to move as quickly as possible to the next stage to be able to bring this treatment to patients,” Rohit Batta, chief medical officer of Vicore said.

A total of 25 patients with IPF have been enrolled in the AIR study so far with 21 evaluable at the time of interim analysis. Of those patients, 13, 9, and 7 had reached 12, 24, and 36 weeks of treatment, respectively. During the study, patients received 100 mg of C21 twice daily for 24 weeks with the option of a 12-week extension.

“Based on the mechanism of action of C21, which has both vascular and antifibrotic characteristics, we were optimistic, but this exceeds our expectations,” Joanna Porter, coordinating investigator in the AIR study said.

C21 is believed to have multiple mechanisms of action including activation of epithelial function to improve alveolar integrity, the release of nitric oxide by endothelial cells to aid in vascular remodeling and vasodilation, inhibition of TGFβ1 to prevent fibrosis, and activation of matrix metalloproteinase for fibrinolysis.


Vicore’s AIR study interim analysis suggests that C21 improves lung function in IPF patients. News Release. Vicore Pharma; February 10, 2022.
C21 IPF AIR Study – Interim Analysis. News Conference. Vicore Pharma; February 10, 2022.