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Cross Species Comparison


  • Drug transporter assays
  • Drug interactions
  • Flux and net flux drug transport
  • Intracellular drug and metabolite concentrations
  • Kidney toxicity assays
  • Renal drug safety evaluation


  • aProximate™ kidney proximal tubule cells


  • Human
  • Mouse
  • Rat
  • Dog
  • NHP

Cross-species comparison of drug handling with near-physiological kidney transporter model

New drug molecules are usually tested in vivo in two preclinical species to gain a more detailed understanding of how they are transported and eliminated through the kidney and also to mitigate risk of renal toxicity in humans. However, these animal models are not always predictive of human responses. To address this problem, robust, comparative in vitro kidney transporter models, such as aProximate™, are powerful tools to compare different species and are much needed to improve in vitro-in vivo extrapolation (IVIVE).

Service outputs
Species differences in:

  • Apical to Basal (Jab) and Basal to Apical (Jba) flux
  • Net transport
  • Renal toxicity

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Cross species comparisons
Coloured Transmission electron microscopy (TEM) of kidney tubule cells

Identify optimal pre-clinical species

Compare multiple species

Rapid results

Newcells aProximate™ model

Accelerate your lead compound selection by understanding their mode of action in kidney tissue


Fully differentiated and polarised kidney proximal tubule cells


High expression of all relevant transporters


High predictivity of in vivo and clinical outcomes.

Example 1: Cross-species comparison of drug handling of PAH excretion in our kidney transporter model Close Open

Para-aminohippurate (PAH), a derivative of hippuric acid, is used as a diagnostic agent for the measurement of renal plasma flow. When infused intravenously, PAH is largely extracted from the blood by OAT1, the classic PAH transporter. The addition of probenecid, an OAT1 inhibitor, reduces PAH clearance due to drug-drug interactions at the transporter level.

PAH excretion was evaluated in vitro using aProximate™ PTCs from four different species to determine any differences in PAH handling could be detected in vitro. Measurement of PAH apical to basolateral flux (Jab), basolateral to apical flux (Jba) and net flux (Jnet) showed a net secretion of PAH in human, non-human primates, dogs and rat PTCs. In summary, aProximate™ is an ideal kidney transporter model to test drug handling and drug safety in different species in vitro prior to selecting preclinical species.

Cross-species comparison of PAH drug handling in human, dog and rat aProximate™ proximal tubule cells. Apical to basolateral flux (JAB), basolateral to apical flux (JBA) and net flux (JNet) suggest a net secretion of PAH in human, dog and rat aProximate™.
Example 2: Understanding the molecular basis of renal toxicology differences of a compound using a kidney transporter model Close Open

Newcells has investigated renal toxicology following exposure to the herbicide MCPA (4-chloro-2-methylphenoxyacetic acid) to elucidate the molecular basis of species differences observed as part of a collaborative project (Gledhill et al., 2022).

MCPA is a globally registered herbicide to control broadleaf weeds in cereals. Toxicological investigations using MCPA identified the kidneys as the primary target organ following oral dosing in rat, mouse and dog. Toxicokinetics of MCPA and other derivatives in rodent and non-rodent models concluded that kinetic differences in the dog suggest that this species is less relevant to human risk assessment than rodents.

This work aimed to establish the molecular basis for the greater sensitivity of the dog to the toxic effects of MCPA compared with the human and rat. Part of the work consisted of in vitro renal transporter studies using Newcells‘ aProximate™ kidney transporter model comparing proximal tubule cell flux in rat, dog and human.

The data were evaluated as a whole to provide a mechanistic rationale for the higher systemic exposures in the dog compared to those seen in other species and support the lack of relevance of the dog as a model species for MCPA human health risk assessments.

Net flux of MCPA (in ng/cm2/hr) through renal proximal tubule cell monolayers from rat, dog or human donors.  MCPA (50μg/ml) incubated for 90 min in the presence or absence of OAT1 inhibitor probenecid (200μM). Adapted from Gledhill et al., (2022).


The chlorophenoxy herbicide MCPA: A mechanistic basis for the observed differences in toxicological profile in humans and rats versus dogs.

View Publication
Service overview Close Open

Our service provides insights into cross-species differences in drug handling: aProximate™ is available in multiple species such as human, rat, dog and NHP, making it the ideal kidney transporter model for assessment of cross-species comparison of drug handling.

Perform rapid in vitro species comparison to select the best preclinical species and progress lead compounds into clinical development by using our transporter assays.

The cross-species comparative data generated from our transporter assays have been used for IND and IMPD submissions as it provides detailed mechanistic insights into drug excretion in several species, explaining possible differences.

Our project timelines are short due to our regular supply of fresh kidney tissue. The robust data generated by our scientific experts will guide you in confidence for key decision-making steps during drug development.

An example of cross-species drug interaction packages includes assessment of transepithelial flux in proximal tubule cells, specifically Apical to Basal (Jab) and Basal to Apical (Jba) flux, as well as net transport measurements in rat, dog and human. We can also measure the magnitude of intracellular accumulation across both the apical and basolateral membranes. We recommend acquiring data from three separate biological donor kidneys across all species.

Assay design

aProximate™ primary isolated kidney proximal tubule cells

Assay format
  • 24-well Transwell® plates (transporter assays)
  • 96-well Transwell® plates (kidney toxicity assays)


  • Human
  • Mouse
  • Rat
  • Dog
  • Non-human primate
Assay readout
  • Apical to Basal (Jab) and Basal to Apical (Jba) flux
  • Net transport measurements
  • Measurement of intracellular drug and metabolite concentrations
  • Kidney toxicity assays
Time points and replicates
  • 0, 30, 60, 90, 120 minutes (flux)
  • 72 hours (toxicity assays)
  • Data points are usually performed in triplicates

Model available for this service

aProximate™ proximal tubule cells

aProximate™ is one of the most advanced, near physiological, in vitro, kidney proximal tubule cell (PTCs) models. aProximate™ PTCs are derived from fresh human, rat, mouse, dog and NHP kidney tissue grown on Transwells®,where they remain well differentiated as a polarised cell layer forming tight junctions.

More information
A microscope image of a nephron model


Cross species comparisons
Coloured Transmission electron microscopy (TEM) of kidney tubule cells. Basal infoldings are labelled in red colour, mitochondria in green, nuclei in yellow and lysosomes in dark blue. Kidney tubule cells contain many mitochondria to handle drugs and excrete xenobiotics. Mitochondrial health is a good indicator of overall cell heath and allows the evaluation of drug safety.
A microscope image of a proximal tubule
Kidney proximal tubules stained with Mallory's aniline. Both the brush border and the basement membrane surrounding the tubule are clearly highlighted.


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