U.S. Food and Drug Administration

1. U.S. Food and Drug Administration Notice: Archived Document The content in this document is provided on the FDA’s website for reference purposes only. It was current when produced, but is no longer maintained and may be outdated.

2. Tulathromycin Solution for Parenteral Injection for Treatment of Swine and Bovine Respiratory DiseaseMicrobiological Effects on Bacteria of Human Health Concern: A Qualitative Risk Estimation Scott A. Brown, DVM, PhD, Dipl ACVCP Senior Director, Metabolism & Safety Pfizer Animal Health

3. Overview • Guidance #152 risk analysis terminology • Hazard Characterization • Tulathromycin risk estimation summary • Qualitative Risk Estimation • Release assessment • Exposure assessment • Consequence assessment • Overall risk estimation • Conclusions

4. Indications and Regimen • For the treatment of bovine respiratory disease (BRD) associated with label pathogens, and for the control of BRD in cattle at high risk of BRD • For the treatment of swine respiratory disease (SRD) associated with label pathogens • Single parenteral injection (cattle and swine) • Not for use in lactating dairy cows or preruminant calves

5. Guidance #152 Risk Analysis Terminology

6. FDA/CVM Guidance #152 Evaluating the Safety of Antimicrobial New Animal Drugs With Regard to their Microbiological Effects on Bacteria of Human Health Concern “Microbial Safety File” Guidance Released October 23, 2003

7. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Guidance #152 Risk Analysis Terminology Hazard Characterization

8. Tulathromycin Hazard Characterization (FDA/CVM Guidance #152) • Focus on Campylobacter • Macrolides are used to treat campylobacteriosis when antimicrobial therapy is indicated • Macrolides are not used to treat Salmonella, E. coli • Macrolides are not used to treat Enterococcus infections • High macrolide resistance rates for clinical isolates since 70s • Other therapeutic options available • Macrolide resistance determinants are transferable in Enterococcus, but tulathromycin activity is attenuated in colonic contents, feces due to binding, pH

9. Tulathromycin Hazard Characterization (FDA/CVM Guidance #152) • The “Hazard” is • human illness (campylobacteriosis), • caused by an antimicrobial-resistant bacteria (macrolide-resistant Campylobacter), • attributable to an animal-derived food commodity (beef or pork), and • treated with the human antimicrobial drug of interest (a macrolide)

10. Tulathromycin Hazard Characterization (FDA/CVM Guidance #152) • The “Hazardous Agent” is • antimicrobial-resistant food-borne bacteria (macrolide-resistant Campylobacter) of human health concern • that are in or on a food-producing animal (beef cattle or swine) • as a consequence of the proposed use of the antimicrobial new animal drug (tulathromycin)

11. Tulathromycin Hazard Characterization (FDA/CVM Guidance #152) • The “Specific Risk” is • the probability that human food-borne illness (campylobacteriosis) is • caused by an antimicrobial- resistant bacteria (macrolide-resistant Campylobacter), • attributable to an animal-derived food commodity (beef or pork), and • treated with the human antimicrobial drug of interest (a macrolide)

12. Summary of Risk Estimation

13. Release Assessment Summary • “Low” probability that macrolide-resistant (MacR) Campylobacter will be selected as a result of proposed tulathromycin use • Attenuated microbiological activity of tulathromycin in colonic contents: • Low pH • Binding to fecal substrates • MacR occurs by mutation in Campylobacter • Frequency of spontaneous mutation is low (<10-9) • No evidence of transferable macrolide resistance • No unique resistance mechanisms detected

14. Release Assessment Summary • Proposed use of tulathromycin supports “Low” Release: • Parenteral use under veterinary prescription only • Individual animal treatment (not pre-ruminants) • Single dose = full course of therapy • Treatment of BRD and SRD usually occurs at a time substantially before slaughter

15. Release Assessment Summary • Expect selection pressure by tulathromycin will be no greater than that for macrolides currently used in livestock: • Tulathromycin activity attenuated in colonic content, feces • Tulathromycin mechanism of action, cross-resistance profile same as current-use macrolides • Macrolides are currently used for SRD, BRD • Macrolide resistance in Campylobacter acquired by mutation, not gene acquisition • Despite >30 years of macrolide use in livestock (parenteral, in-feed, water medications), MacR C.jejuni from humans is low (1-3%); no trends over time

16. Campylobacter in Beef Exposure Recommendation* *Sponsor accepts the default recommendation

17. Campylobacter in Pork Exposure Default (G#152)

18. Campylobacter in Pork Exposure Recommendation* *Sponsor recommendation

19. Consequence Assessment Summary • Guidance #152 defines macrolides as “Critically Important” in human medicine • For the treatment of Legionnaire’s disease; and atypical Mycobacterium (Mycobacterium avium complexus/M. avium intracellulaire) prophylaxis and therapy • For the treatment of foodborne diseases (i.e., Campylobacter)

20. Sponsor Conclusions:Microbial Safety of Tulathromycin • The proposed label use of tulathromycin includes management considerations of: • prescription status • inherent low extent of use due to parenteral single dose administration • Advisory Committee Review • MacR is currently monitored by NARMS • With these management considerations, approval of the proposed indications for injectable tulathromycin in cattle and swine poses no appreciable risk to public health with respect to microbial food safety.

21. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Qualitative Risk Estimation

22. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Qualitative Risk Estimation Release Assessment

23. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Qualitative Risk Estimation Release Assessment Chemistry and Disposition

24. 3 basic amino groups = highly charged form in solution pKa 8.6, 9.6, 9.9 aids penetration of the outer membrane of Gram-negative bacteria. Lipophilic when unionized Metabolically stable Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Tulathromycin Chemistry C41H79N3O12 molecular weight: 806.23 Letavic et al., 2002; Norcia et al., 2004

25. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Tulathromycin Mechanism of Action/Spectrum of Activity • Mechanism: Inhibits protein synthesis • Similar to other macrolides (e.g., erythromycin, tilmicosin) • Binds to the 23s rRNA of bacterial ribosomes • Competes for erythromycin-binding • Binds to erythromycin-sensitive ribosomes • No binding to erythromycin-resistant ribosomes • Spectrum: Broad-spectrum activity against bacterial respiratory disease pathogens in cattle and swine

26. Release Assessment Risk Estimation Exposure Assessment Microorganism No. strains MIC (g/ml) Consequence Assessment Range MIC50 MIC90 Campylobacter spp1 30 0.25 – 128 0.5 64 Enterococcus faecalis 9 4.0 - >128 8.0 NA E. faecium 21 4.0 - > 128 8.0 >128 Enterococcus spp2 8 4.0 - >128 4.0 NA Escherichia coli 16 4.0 – 8.0 8.0 8.0 Salmonella spp3 15 4.0->128 4.0 8.0 1Includes: 2 C. fetus, 13 C. jejuni, 15 Campylobacter spp. 2Includes: 1 E. avium, 7 E. gallinarium 3Includes: 7 S. choleraesuis, 6 S. dublin, 2 S. enteritidis MICs of Tulathromycin Tested Against Foodborne Microorganisms

27. Release Assessment Risk Estimation Exposure Assessment Microorganism Mean MIC (g/mL) atpH: Consequence Assessment 6.5 7.0 7.2 7.4 7.6 8.0 E. coli ATCC 25922 >128 18.4 4.59 2.0 2.0 2.0 E. faecalis ATCC 29212 >128 36.8 12.1 3.48 2.0 2.30 S. aureus ATCC 29213 >128 24.3 8.00 3.03 1.74 2.0 Effects of pH on Tulathromycin Activity

28. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Parenteral dosing Plasma Tmax(hours)1 Cmax(µg/mL) 0.5 t1/2(hours)90 AUC0-¥ h(ng·h/mL) 16,700 VSS(L/kg) 11 F(%) 87.70 Tmax = time to maximum concentration; Cmax = maximum concentration; t1/2 = half life; AUC = area under conc.-time curve;Vss = volume of distribution at steady state; F = bioavailability Tulathromycin Pharmacokinetics Bovine Plasma Profile • Fast-acting due to rapid release from injection site • Extensively distributed; high volume of distribution • Extended half-life; prolonged duration • High bioavailability

29. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Parenteral Dosing Plasma Tmax(hours)0.92 Cmax(µg/mL) 0.581 t1/2(hours)91 AUC0-¥ h(ng·h/mL) 12,200 VSS(L/kg) 13.2 F(%) 88 Tmax = time to maximum concentration; Cmax = maximum concentration; t1/2 = half life; AUC = area under conc.-time curve;Vss = volume of distribution at steady state; F = bioavailability Tulathromycin Pharmacokinetics Swine Plasma Profile • Fast-acting due to rapid release from injection site • Extensively distributed; high volume of distribution • Extended half-life; prolonged duration • High bioavailability

30. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Metabolism/Excretion in Feces • 30-60% of total dose excreted in feces, depending on the species • Peak concentrations 30-100 g total drug residues/g • 90% as unchanged drug • Tulathromycin activity in colon contents and feces is substantially attenuated • Significant percentage (>70%) binds to fecal solids • In vitro activity of tulathromycin is reduced when sterilized feces added to growth media • E. coli • Enterococcus • Bifidobacterium • Fusobacterium

31. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Tulathromycin Chemistry and Disposition Conclusions • Low in vitro activity against enteric foodborne pathogens • Attenuated activity at pH found in colonic contents • High fecal binding of drug • Transient concentrations in colon

32. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Resistance Mechanisms, Genetics, and Location

33. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Mechanisms of Macrolide Resistance • Target site modification • Sequence change in ribosome due to mutation • rRNA methylation (e.g., ermA, ermB) • Inducible (erythromycin does; tilmicosin and tulathromycin do not) • Constitutive • Drug inactivation • Phosphorylation (e.g., mphA or mphB) • Hydroxylation (e.g., ereA and ereB) • Drug efflux pumps (e.g., msrA and mefA)

34. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Transferable Resistance • Macrolide resistance genes are transferable • Study showed no difference in transfer frequency of plasmid-mediated macrolide resistance when tulathromycin was added to E. faecalis mating pair • Tulathromycin activity is attenuated due to pH and binding, thus limiting tulathromycin’s ability to select for enterococci containing these genetic elements

35. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Transferable Resistance Determinants • Transferable genes for MACR have not been reported in Campylobacter* • Unlike other bacteria, erm gene resistance has not been reported in Campylobacter • Macrolide resistance due to mutation only *Jensen & Aarestrup, 2001; Yan & Taylor, 1991

36. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Cross-Resistance • Constitutively expressed erm genes confer cross-resistance to macrolides, lincosamides, streptogramin B (MLSB) • Tulathromycin and tilmicosin have similar cross-resistance profiles for human pathogens, both are weak inducers of erm genes • Efflux pumps • Campylobacter having high erythromycin MIC’s have high tulathromycin MIC’s (I.e., are cross-resistant)

37. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Point Mutations • E. coli, Salmonella, Enterococcus, and Campylobacter studies: • No tulathromycin- or macrolide-resistant mutants found at the frequency expected for spontaneous mutation (10-9)

38. Macrolide Resistance in Campylobacter

39. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Resistance/Genetics Conclusions • Three types of macrolide resistance mechanisms documented • Many of the genes are transferable • Erm genes are broadly disseminated and confer cross-resistance to MLSB • Transferable macrolide resistance genes have not been documented in macrolide-resistant Campylobacter • Macrolide-resistance in Campylobacter occurs via chromosomal mutation • Mutation frequency to macrolideR is very low (< 10-9 )

40. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Resistance Selection Pressures in the Field BRD & SRD in the USCurrent Macrolide Use Antibiotics Use

41. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Bovine Respiratory Disease Labored Breathing Normal Depressed

42. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Percent of Cattle that Developed Diseases after Arrival Feedlot 1999 – Part III, USDA/NAHMS survey, December 2000)

43. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment BRD: Impact • Animal welfare • 31.1% of all bovine deaths • 57-79% of feedlot mortality • Cost to the industry • Over 23 million cattle in feedlots annually (residence time in feedlots is about 6 months) • 15% (BRD) of 23M cattle = 3.45M feedlot cattle affected by BRD • Hundreds of millions of dollars lost due to BRD Vogel 1994; Lonergan et al, 2001

44. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Swine Grower/Finisher Deaths by Producer-Identified Causes Swine 2000 – Part I, USDA/NAHMS survey, August 2001

45. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment BRD and SRD in the US Summary • BRD affects approximately 15% of feedlot cattle (over 3.4M feedlot cattle affected) - morbidity • SRD causes approximately 40% of deaths in swine - mortality

46. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Macrolide Approvals in Cattle and Swine

47. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Uses of Currently Approved Macrolides • Treatment of respiratory disease • Treatment of cattle at high risk of respiratory disease • Control of diseases (swine dysentery caused by Brachyspira hyodysenteriae, bacterial respiratory disease) • Growth promotion

48. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Percent of Cattle that Received the Following Antimicrobials in Feed or Water Feedlot 1999 – Part III, USDA/NAHMS survey, December 2000

49. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Percent of Sites that Gave Antibiotics to Weaned Pigs as a Preventative Practice USDA/APHIS Veterinary Services Info Sheet, March 2002

50. Release Assessment Risk Estimation Exposure Assessment Consequence Assessment Five Most Common Antibiotics (by route of administration) Given to Grower/Finisher Pigs USDA/APHIS Veterinary Services Info Sheet, March 2002