TunR2, a novel mode-of-action tunicamycin-type antibiotic: pharmacokinetics in C57BL/6 mouse and Holstein cattle

Authors: COLOMBATTI OLIVIERI, MARIA - Oak Ridge Institute For Science And Education (ORISE); CASSMANN, ERIC - Iowa State University; Jackson, Michael; Price, Neil; Bannantine, John

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/23/2025
Publication Date: 7/23/2025
Citation: Colombatti Olivieri, M.A., Cassmann, E.D., Jackson, M.A., Price, N.P., Bannantine, J.P. 2025. TunR2, a novel mode-of-action tunicamycin-type antibiotic: pharmacokinetics in C57BL/6 mouse and Holstein cattle. PLOS ONE. https://doi.org/10.1371/journal.pone.0327932.
DOI: https://doi.org/10.1371/journal.pone.0327932

Interpretive Summary: We tested the safety of two new synthetic antibiotics, termed TunR1 and TunR2, in mice and cattle. The time to disappearance of the drug in the host (sometimes referred as the withdraw time) was measured in tissues, blood, urine and feces. We found that the synthetic antibiotics had a longer half life and were distributed more widely in tissues compared to the natural tunicamycin antibiotic. TunR2 did not breakdown in cows even after 10 days when it was cleared from the cows. Finally, the TunR2 was found to be safe in cows at microdose levels. These results show considerable potential for using TunR2 to treat bacterial pathogens in cows. These findings are of use to veterinarians and scientists working in the field.

Technical Abstract: We have investigated the pharmacokinetic of TunR2, a modified tunicamycin-type antibiotic, in mice and cattle. TunR2 has previously been shown to be effective in a mycobacterial disease model using zebrafish, with a minimal activation of the eukaryotic unfolded protein response (upr) and reduction of the in vivo mycobacterial burden. In this study, we presented statistically relevant pharmacokinetics of native tunicamycin (Tun) and two less toxic modified analogs, TunR2 and TunR1, using a well-defined clonal C57BL/6 mouse (both male and female). Blood samples were collected at multiple time points, and plasma concentrations were quantified using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Pharmacokinetic parameters were calculated using non-compartmental analysis. Our findings indicate that Tun and TunR1 tend to distribute in tissue compared to TunR2, which has a longer half-life than Tun. This translates into longer TunR2 activity time, potentially allowing for less frequent dosing than Tun or TunR1. We subsequently administered the modified TunR2 to Holstein cattle using a three-bolus intravenous regimen. We monitored blood, milk, urine, and feces over a 90-day period. In dairy cattle, the pharmacokinetics of TunR2 appear cumulative, and it remains metabolically unaltered prior to clearance after 10 days. These findings provide critical new insights into the pharmacokinetics of TunR2. We concluded that TunR2 has considerable potential for the treatment of bacterial infections particularly as an antimicrobial adjuvant with well-established ß-lactam antibiotics. Further studies are required to study safety and optimize dosing regimens for effective therapeutic use and in combination with other antibiotics like ß-lactams.