Safety Assessment UK Alderley Park Cheshire United Kingdom

1. Safety Pharmacology Society Webinar Series:Safety Pharmacology Endpoints: Integration into Toxicology StudiesIntegrating functional CNS observations into toxicology studies: the CONS!Will Redfern, PhD Safety Assessment UKAlderley ParkCheshireUnited Kingdom September 20, 2012

2. Reasons for attrition of candidate drugs Meanwhile, ADME failures have been reduced by a ‘frontloading’ approach Kola & Landis (2004) Nature Reviews: Drug Discovery3: 711-715.

3. Attrition due to inadequate safety – why?

4. Attrition due to inadequate safety – why?

5. Impact of adverse effects of drugs by organ function throughout the pharmaceutical life cycle   2010 Update: Increased contribution from Nervous System AEs in 2010 No change in 10 years! The various toxicity domains have been ranked first by contribution to products withdrawn from sale, then by attrition during clinical development. 1-9% Adapted from Redfern WS et al. SOT 2010; 2011 0% >20% 10-19%

6. Impact of functional adverse effects on the nervous system on drug development during 2010: Source: DIA Daily January to December 2010

7. Impact of functional adverse effects on the nervous system on drug development during 2010: Impact of QT/TdPissues on drug development during 2010 by comparison: Source: DIA Daily January to December 2010

8. Functional measurements in repeat-dose toxicity studies Regulatory drivers Scientific drivers Doing it instead of standalone safety pharmacology studies Doing it in addition to standalone safety pharmacology studies • Rationale: • To provide early warning flags well ahead of the regulatory GLP SP core battery studies (by incorporating into early tox/MTD studies). • To assess whether findings in acute SP studies persist, intensify, or diminish after repeated dosing, and to demonstrate recovery after cessation of dosing. • To provide functional correlates of histopathological findings in previous tox studies. • To assess potential effects that may only develop after prolonged exposure. Rationale: To opt for the minimum regulatory requirement for FTIM: ICHS6 (Biologics) ICHS9 (Oncology Products) FDA Guidance on Exploratory IND Studies by incorporating SP core battery assessments into the 1-month regulatory tox studies. I have reservations about this. This will be what I’m focusing on today. I’m OK with this. Let’s have more of it!

9. Starting point... • Clearly, adverse effects on the nervous system make a significant contribution to attrition of candidate drugs during clinical development. • Therefore, the last thing we should do is reduce the quality of the preclinical CNS safety pharmacology assessment. • So, do more ‘as well as’, and reduce the temptation to go for ‘instead of’*. *In other words, do include CNS safety pharmacology endpoints in repeat-dose toxicity studies as well as standalone single-dose safety pharmacology studies, rather than instead of.

10. Why not replace standalone CNS safety pharmacology studies with assessments in repeat-dose toxicity studies – what’s the big deal? • The laboratory conditions in toxicology holding rooms/procedure rooms are not optimal for obtaining high quality behavioural data (due to noise; disturbance etc.). • The phenomenon of tolerance means that the responses measured on Day X may be diminished compared to Day 1 (ie, first administration). • By Day X, what you may be measuring is not the pharmacological response to the compound, but the effects of overt toxicity (inappetance; weight loss; general malaise). • Circumventing ‘2’ and ‘3’ above by doing the assessments on Day 1 of dosing causes logistical difficulties.

11. Limitations of SP endpoints in tox studies • The primary aim of a repeat-dose toxicity study is to expose animals to different levels of a test compound over a prolonged period, and to assess a standard list of in-life parameters (incl. clinical chemistry; body weights, food & water consumption; routine clinical observations; ophthalmoscopy; ECG, etc.), toxicokinetics, and post-mortem histological changes. • Any additional functional measurements MUST NOTinterfere with these aims or affect their outcome. • The study design and laboratory conditions may be sub-optimal for obtaining high-quality functional data.

12. Differences in in-life environments (etc.)

13. Example of a custom-designed, fit-for-purpose in vivo safety pharmacology suite CNS evaluations done here • Features: • Testing labs located remote from corridor noise (e.g., trundling of cage racks; loud conversations). • Primary access to suite via single entry door, with warning to limit entry to essential visits and to minimise noise level. • Staff requiring access to the other animals on the study can do so without disturbing the safety pharmacology observations/measurements. • Entry to the testing labs restricted to staff involved in the observations/measurements. • Designed to accommodate bulky test equipment, ergonomically. • Lighting control with local (manual) override.

14. Example of toxicology study holding rooms with ante room CNS evaluations done here • Drawbacks(for CNS safety pharmacology observations/measurements): • Testing area adjacent to corridor noise (e.g., trundling of cage racks; loud conversations). • Access from corridor directly into testing area. • Staff requiring access to the other animals on the study disturb the safety pharmacology observations/measurements. • Entry to the testing area unrestricted. • Bulky test equipment may be difficult to accommodate ergonomically. • Automated lighting control with no manual override.

15. Development of tolerance with repeat-dosing A DECREASE in response/clinical efficacy with repeat-dosing ‘‘Some form of adaptive syndrome is the inevitable consequence of the reciprocal interaction between most or all classes of drugs and the organism’’. W Haefely (1986)

16. (slow) (slow) (slow) (slow) Pupillary light reflex in a repeat-dose toxicology study in rats:tolerance developing to a mydriatic effect Drug Xµmol/kg po (n = 6 each) (No further dosing at high dose level) Redfern WS et al. (2007) A simple method for estimating pupil diameter in conscious rats and dogs during repeat-dose toxicity studies. J Pharmacol Toxicol Methods 56: e50.

17. Saliva production in a repeat-dose toxicology study in dogs:tolerance developing to a salivatory effect Salivation quantified by placing a pre-weighed gauze swab inside a jowl for 20 s; removed and re-weighed. First measurement was on Day 3 of study. (AZ in-house data)

18. Example of tolerance, increased response, and no change in response in the same study with the same compound! Effects of once-daily dosing with baclofen (10 mg/kg po) in the Irwin test in rats (3M; 3F) Conclusion: Change in magnitude of effect over repeated dosing is both pharmacology- and parameter-specific – and can’t be predicted in advance. AZ in-house data: courtesy of Lorna Ewart

19. Logistics for rodent studies… If you choose to go down this route (replacing the standalone safety pharmacology study), it is preferable to conduct functional measurements on Day 1 of the repeat-dose toxicity studies for the reasons outlined earlier (ie, you may miss an acute response that diminishes with repeat-dosing). But Day 1 of a tox study is usually mayhem, with timed TK bleeds etc. So, you could do the measurements on Day 2 of the repeat-dose study. However, you won’t get through all the Irwin tests (multiple time points) and whole-body plethysmography (WBP) measurements (4 hours’ recordings) on the vehicle and 3 dose levels (Irwin: 24 rats; WBP: 32 rats) in one day! So you could do (say) the Irwin tests on Day 2 and the WBP measurements on Day 3. Even then, you still won’t complete either of these evaluations in a single day. So you may have to stagger the start of the rodent 1-month study, e.g.: MON TUE WED THU Day 1 Start cohort 1 Day 2 cohort 1: Irwin Day 3 cohort 1: WBP Day 4 cohort 1 Day 1 Start cohort 2 Day 2 cohort 2: Irwin Day 3 cohort 2: WBP And you’ll have to reduce the standard number of time points in the Irwin test.Do you have enough quiet space to run Irwin and WBP simultaneously, close to the tox holding room…?

20. Conclusions • Replacement of the ‘standalone’ CNS safety pharmacology study with ‘CNS safety pharmacology assessments’ in a repeat-dose tox study represents a dumbing-down of the preclinical CNS risk assessment. • This would be like replacing the dog telemetry cardiovascular assessment with a ‘snapshot ECG’ in a tox study to assess QT risk. • You wouldn’t do that, would you...?

21. Acknowledgements Colleagues at AstraZeneca Alderley Park: Sharon Storey; Helen Prior; Claire Grant; Louise Marks; Lorna Ewart; Kat Greenwood; Claire Barnard; Dave Simpson; Sally Robinson; Jean-Pierre Valentin.