Pharmacokinetic and pharmacodynamic evaluation of the atypical tetracyclines chelocardin and amidochelocardin in murine infection models

ABSTRACT The quest for novel anti-infectives against drug-resistant pathogens of the so-called ESKAPE panel is accompanied by intensive research aiming to find treatment options for the future. In this study, we evaluated the pharmacokinetics and pharmacodynamics of the two atypical tetracyclines: chelocardin (CHD) and amidochelocardin (CDCHD). Although CHD was in phase II clinical trials in the 1970s against urinary tract infections (UTI), CDCHD is a novel derivative obtained by biosynthetic engineering. A pharmacokinetic evaluation in uninfected, non-neutropenic CD-1 outbred mice using intravenous, peroral, and subcutaneous routes showed that CHD had higher plasma exposure than CDCHD but underwent an epimerization that was not observed for CDCHD. CDCHD showed persistently high exposure levels in urine lasting for more than 24 hours, whereas CHD urine concentrations decreased faster over time. Pharmacodynamic characterization in the neutropenic thigh infection model with K. pneumoniae and E. coli as challenge pathogens in CD-1 outbred mice proved that CHD was more effective in reducing bacterial burden in the thigh, in particular against E. coli, whereas CDCHD effectively reduced bacterial burden in kidneys affected by hematogenous seeding from the primary inoculation site, that is, thigh. Assessment of both atypical tetracyclines in an ascending UTI model with bladder as the primary inoculation site against gentamicin as positive control revealed high effectiveness of CDCHD. In summary, CDCHD warrants further preclinical exploration for the indication of UTI. IMPORTANCE There is a strong need to find novel treatment options against urinary tract infections associated with antimicrobial resistance. This study evaluates two atypical tetracyclines, namely chelocardin (CHD) and amidochelocardin (CDCHD), with respect to their pharmacokinetics and pharmacodynamics. We show CHD and CDCHD are cleared at high concentrations in mouse urine. Especially, CDCHD is highly effective in an ascending urinary tract infection model, suggesting further preclinical evaluation.


Figure S4. Assessment of higher doses of CHD in the neutropenic thigh infection model with K. pneumoniae.
CHD was tested in the neutropenic thigh infection model with K. pneumoniae at 50 mg/kg SC QD, 15 mg/kg SC TID and 10 mg/kg SC QID against levofloxacin 3.3 mg/kg IP TID.Bacterial loads were determined in thigh (a), blood (b) and kidney (c).Bacterial loads were expressed as log10 cfu/g in thigh and kidney and as log10 cfu/ml in blood.Per group n=6 animals were used.Two thighs from one animal were pooled.*: p < 0.05, ***: p < 0.001.CDCHD was tested in the neutropenic thigh infection model with K. pneumoniae at 50 mg/kg SC QD, 15 mg/kg SC TID and 10 mg/kg SC QID against levofloxacin 3.3 mg/kg IP TID.Bacterial loads were determined in thigh (a), blood (b) and kidney (c).Bacterial loads were expressed as log10 cfu/g in thigh and kidney and as log10 cfu/ml in blood.Per group n=6 animals were used.Two thighs from one animal were pooled.*: p < 0.05, ***: p < 0.001, ****: p < 0.0001.CHD and CDCHD were tested in an ascending urinary tract infection model with E. coli at 10 mg/kg SC BID against gentamicin 100 mg/kg SC BID.Bacterial loads were determined in urine (a), bladder (b) and kidney (c).Bacterial loads were expressed as log10 cfu/ml in urine, log10 cfu/bladder for bladder and as and kidney and as log10 cfu/kidney for kidney.Per group n=21 animals were used.Here, the mean with the 95% confidence interval (CI) is plotted.ns : not significant, **: p < 0.01, **** : p < 0.0001.

Figure S3 .
Figure S3.Assessment of low doses of CHD and CDCHD in the neutropenic thigh infection model

Figure S4 .
Figure S4.Assessment of higher doses of CHD in the neutropenic thigh infection model with

Figure S5 .
Figure S5.Assessment of higher doses of CDCHD in the neutropenic thigh infection model with

Figure S6 .
Figure S6.Assessment of CHD and CDCHD in an ascending urinary tract infection model with

Figure S7 .
Figure S7.Bioanalysis of terminal plasma and urine samples from the ascending urinary tract

Figure S2 .
Figure S2.Pharmacokinetic profiles of CHD and CDCHD at 15 and 30 mg/kg IV.CDCHD (a,c) and CHD (b,d) were administered at 15 mg/kg IV and 30 mg/kg IV, respectively.Plasma concentrations of CDCHD (a) and CHD (c) at 15 mg/kg IV (white) and 30 mg/kg IV (black) are displayed.Moreover, urine concentrations of CDCHD (b) and CHD (d) at 15 mg/kg IV (white) and 30 mg/kg IV (black) are displayed.N=3 mice were used per time point.

Figure S3 .
Figure S3.Assessment of low doses of CHD and CDCHD in the neutropenic thigh infection model with K. pneumoniae.

Figure S5 .
Figure S5.Assessment of higher doses of CDCHD in the neutropenic thigh infection model with K. pneumoniae.

Figure S6 .
Figure S6.Assessment of CHD and CDCHD in an ascending urinary tract infection model with display of the 95 % confidence interval.

Figure S7 .
Figure S7.Bioanalysis of terminal plasma and urine samples from the ascending urinary tract infection model.CDCHD and CHD were both assessed in an urinary tract infection model with E. coli.Terminal plasma (a) and urine (b) levels of both CHD and CDCHD are displayed.N=24 for plasma and n=3 for urine.

Table S5 .
Doses and dosage regimens in the neutropenic thigh infection model with K. pneumoniae (high dose CHD).

Table S6 .
Doses and dosage regimens in the neutropenic thigh infection model with K. pneumoniae (high dose CDCHD).

Table S7 .
Doses and dosage regimens in the neutropenic thigh infection model with E. coli.