Longitudinal study to follow-up a developmental abnormality Luc De Schaepdrijver, DVM, PhD Preclinical Development & Safety Janssen R&D, Belgium

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1 Longitudinal study to follow-up a developmental abnormality Luc De Schaepdrijver, DVM, PhD Janssen R&D, Belgium ILSI-HESI Workshop, Washington, April 21 st, 2015 Fetal Imaging in Regulatory Developmental Toxicity Studies

2 Postnatal follow-up of skeletal anomalies Why? Examination of term fetuses in embryo-fetal developmental studies only provides a snapshot of the skeleton. Characterization of a skeletal anomaly and correct classification as malformation or variation is important in order to avoid grey zone anomalies. A missing piece of information is the postnatal fate of these anomalies. Can postnatal follow-up help in making a better risk assessment? THE question to address: is there reversibility? Does the finding persists during postnatal life or is there repair by bone remodeling (such as wavy ribs)? Consider also the severity of the defect. Does it adversely affects animal survival & health? (full supernumerary ribs persist after birth but are still considered variations).

3 Bent long bones in juvenile rats A case study Probe compound available that provokes a high incidence of bent long bones in an embryo-fetal development (EFD) study Control Shortened & curved bones Treated

4 Results EFD study in the Wistar rat with compound X Fetal Observation (total n of examined fetuses) Control (106) 10 mg/kg (118) 40 mg/kg (100) 160 mg/kg (83) Bent Scapula Bent Humerus Bent Radius Bent Ulna Bent Femur Bent Tibia Bent Fibula

5 Longitudinal CT study Compound X dosed once daily from GD 6 till GD 17 to pregnant SPF Wistar rats. 2 groups : 1 Control group and 1 High dose group. Dams were allowed to litter down and their offspring were examined by repeated CT scans (Triumph multi-modality system, focal spot size 50 m) on postnatal day 0, 7, 21 and 80. Animals were anaesthetized using isoflurane. All CT scans were reconstructed and surface rendered for visual inspection.

6 CT Equipment All micro-ct scans were acquired on a Triumph multi-modality system (Gamma Medica, Northridge, CA) using the following acquisition parameters: tube voltage 80 kvp, tube current 250 ma, focal spot size 50 µm and a field-of-view of 59 or 93 mm.

7 Longitudinal CT study: 3-D image analysis Development of a customized semi-automatic workflow (Definiens, Germany): import of images -> automatic detection of bone regions (fore-and hindlegs) -> automatic segmentation and classification of individual bones -> analysis of bone attributes and statistical analysis. Morphological parameters examined : bone length, width, volume and bending.

8 CT image analysis - Postnatal Day 0 Normal (a) and bent long bones (b)

9 CT image analysis - Postnatal Day 7 Normal (a) and bent long bones (b)

10 Calculation of bending of long bones

11 Flexion values for bent radius and ulna radius ulna

12 Bending of long bones: PND 0 vs PND 7 1 Flection of long limb bones on PND 0 and day 0 day 7 day 0 day 7 day 0 day 7 day 0 day 7 day 0 day 7 day 0 day 7 Scapula Humerus Ulna Radius Femur Tibia control dosed all

13 CT image analysis Recovery within 21 days PND 0 PND 7 PND 21 Adult

14 Longitudinal CT study: Conclusions Quality of the images obtained by CT was satisfactory and comparable to those obtained with the gold standard (Alizarin red). Imaging of the same animal at different postnatal ages allows quantitative measurements of bone structures (bending, length, volume, ). Since bent long bones were transient findings that showed complete recovery within 3 weeks postnatally, this observation could be downgraded from a malformation to a variation.

15 Take home messages Postnatal follow-up of skeletal defects by means of CT can reduce uncertainties regarding their classification and adds valuable information for risk assessment. Besides the severity, transience or permanence of skeletal defects is a key element to assess. Anomalies may either be upgraded (to a malformation) or downgraded (to a variation). Defects with a low prevalence form a challenge for postnatal follow-up. Non-invasive in vivo CT can be very useful to address a particular concern in developmental biology as a second tier more mechanistic approach.

16 Acknowledgements Peter Delille, Ellen Broeckx, Jo Embrechts In-life phase and fetal pathology Infinity imaging lab, Ghent University acquisition of -CT images Definiens AG, Germany image analysis of -CT images David Wise and Julian French -CT inspiration

17 Back-up slides 16

18 Number of scanned pups Scanned pups Control group N of pups (litters) Test article treated group N of pups (litters) Postnatal Day 0 37 pups (4 litters) 48 live pups (8 litters) 16 dead pups (7 litters) Postnatal Day 7 9 pups (2 litters) 20 pups (5 litters) Postnatal Day 21 7 pups (2 litters) 14 pups (3 litters) Postnatal Day 80 2 pups (1 litter) 6 pups (4 litters)