IR3535, the nature inspired repellent from Merck

Transcription

1 IR3535, the nature inspired repellent from Merck Bohlmann AM 1, Broschard T 2, Heider L 1 1 Merck KGaA, Darmstadt Germany, 2 Merck KGaA, Institute of Toxicology Chiang Mai, Thailand 2011

2 Introduction 1.0 2

3 First insect repellents were sourced from nature Nature is an inexhaustible source of inspiration for scientific and technological innovations. Even the idea of repellent protection was adopted from plants producing essential oils for own protection against insect infestation. The transfer of a simple natural protection mechanism to skin protection was the first innovative step. The high evaporation rate of essential oils and the correlated short protection times for personal protection caused the demand to look for solutions with long time protection. 3

4 ß-alanine is the natural prototype for IR3535 For the development of the topical Insect Repellent 3535 (Ethyl butylacetylaminopropionate), scientists took again inspirations from nature with the intention to create a molecule with optimized protection times and low toxicity. The naturally occurring amino acid ß-alanine was used as basic module. O H 2 N O H 4 Poultry, beef and fish are all rich sources of the amino acide ß-alanine

5 ß-alanine is the natural prototype for IR3535 Selected end groups were chosen to avoid toxicity and increase efficacy O N O OC 2 H 5 In 1997, US-EPA-OPP's Biochemical Classification Committee classified IR3535 as a biochemical, based on facts that it is functionally identical to naturally occurring beta alanine in that both repel insects, the basic molecular structure is identical, the end groups are not likely to contribute to toxicity and it acts to control the target pest via a nontoxic mode of action. 5

6 Purpose of this presentation This presentation will provide a review of efficiency of this nature inspired scientific approach in comparison to natural and pure synthetic repellent solutions. Example for synthetic approach: DEET Example for natural approach: Citronella 6

7 Summary of Performance Comparison 2.0 7

8 Performance comparison Chemical quality and purity DEET: synthetic substance with defined quality and high purity; > 95% of N,N-diethyl-meta-toluamide IR3535: synthetic substance with defined quality and high purity; > 98% of Ethyl butylacetylaminopropionate Oil of Citronella: Different types like Java and Ceylong are on the market. Quality and purity depends on distillation and source. More than 80 compounds. 8

9 Performance comparison Safety US-EPA classification DEET: Pesticide which will generally not cause unreasonable risks to s or the environment. EPA required improved label warnings than DEET has been thought to be associated with incidents of seizure IR3535: Biopesticide with non toxic mode of action Oil of Citronella: Biopesticide with non toxic mode of action 9

10 Performance comparison Children use US- EPA / CDC DEET: 30% DEET should be used on children aged > 2 months. Repellents with DEET should not be used on infants aged < 2 months 1 IR3535: Most repellents can be used on children aged > 2 months. Repellent products must state any age restriction. If none is stated, the Environmental Protection Agency has not required a restriction on the use of the product 1 Oil of Citronella: Agency is requiring special precautionary labeling relating to dermal sensitization and irritation for all product with use directions for dermal applications / Use on children under 6 months of age only with the advice of a physician. 2 1 CDC - Traveling Safely with Infants & Children, international-travel-infants-children/traveling-safely-with-infants-and-children.htm 2 EPA - REREGISTRATION ELIGIBILITY DECISION, Oil of Citronella, LIST C, CASE

11 Performance comparison Efficacy US- EPA / CDC DEET: Products containing these active ingredients typically provide reasonably long-lasting protection (US-CDC) IR3535: Products containing these active ingredients typically provide reasonably long-lasting protection (US-CDC) Oil of Citronella: In 1997, the EPA concluded that citronella-based insect repellents must carry the following statement on their labels: "For maximum repellent effectiveness of this product, repeat applications at one hour interval." 11

12 Performance Comparison of Safety

13 Safety DEET IR3535 Oil of Citronella Java Ceylon Acute toxicity oral rat (LD50) mg/kg (EPA) mg/kg (EU) Acute dermal toxicity rabbit or rat (LD50) mg/kg (EPA) > (EU) Acute inhalation (LD50) 5.95 mg/l (EPA) 2.02 mg/i (EU) > mg/kg > mg/kg (EPA) > mg/kg (EPA) > mg/kg > mg/kg (EPA) > mg/kg (EPA) > 5.1 mg/l > 5000 mg/kg (EPA) > 3.1 mg/l (EPA) Eye irritation rabbit Irritating to eye (EPA + EU) Slightly Irritating cleared in 8 days or less Irritation cleared in 72 hours Irritation cleared in 7 days or less Skin sensitisation guinea pig no no Sensitizer No Dermal sensitisation no no - - Subchronic dermal rat (NOAEL) 300 mg/kg/day (EPA) mg/kg/day (EU) mg/kg/day - - Developmental rat (NOAEL) 250 mg/kg/day (EU + EPA) mg/kg/day (oral)

14 Performance Comparison Ecological Toxicity Data DEET: Fish toxicity (rainbow trout) LC 50 = 75 mg/l (slightly toxic) Invertebrate toxicity (Daphnia magna) EC 50 = 75 mg/l (slightly toxic) 1 IR3535: Fish toxicity (zebrafish, Danio rerio) LC 50 > 100 mg/l Invertebrate toxicity (Daphnia magna) EC 50 > 100 mg/l 2 Oil of Citronella: Fish toxicity (rainbow trout) LC 50 = 17.3 mg/l (slightly toxic) Invertebrate toxicity (Daphnia magna) EC 50 = 26.4 mg/l (slightly toxic) 3 1 EPA - REREGISTRATION ELIGIBILITY DECISION DEET, LIST A, CASE Merck KGaA 3 EPA - REREGISTRATION ELIGIBILITY DECISION, Oil of Citronella, LIST C, CASE

15 IR3535 Metabolism The ester structure of the propionate provides essential advantages In case of penetration this molecule shows a high safety level, because of a short metabolic degradation and quick excretion as a simple water soluble acid. O N IR3535 (R) O O O N OH O N-acetyl-3-N-n-butylaminopropionic acid 15

16 Performance Comparison of Efficacy

17 EPA Product Performance (Efficacy) Assessment Citronella Because of numerous public inquires regarding the effectiveness (efficacy) of oil of citronella lotions, the Agency examined efficacy data associated with oil of citronella insect repellent lotion products and determined that product effectivesness diminishes rapidly over time; on the average, rasonalbe effectiveness (efficacy) lasts for 1 to 2 hours. 17

18 Performance comparison of IR3535 and DEET against Aedes aegypti Table 3: Mean Protection time results (h) of IR3535 and DEET against Aedes aegypti Method Formulation / Concentration Cage / Cage / Cage / Cage / Cage / rabbits Cage / Mean Protection (h) IR3535 Mean Protection (h) DEET Reference Ethanolic solution 10% - 30% Liebisch, 1981 Ethanolic solution 10% Shashin, % Cream Cilek, % - 20% Pump Spray Cilek, % - 20% Hydro gel Milutinovic, % Ethanolic solution 20% Usavadee, 2001 In summary, an overall review of available data suggests rough repellency equivalence for the two active ingredients 18

19 Performance comparison of IR3535 and DEET against Aedes albopictus Table 3: % Protection and protection times (h) of IR3535 and DEET against Aedes albopictus Method Formulation / Concentration Field / Aerosol 2 tests 2.5%, 3%, 5% Field Ethanolic solution 25% Field/ Ethanolic solution 2 tests 20% Cage/ Ethanolic solution 25% Protection IR / 6 h 100% / >90% for 4 h / 8h 98.4% / 100% for 8 h 2 h Protection DEET 5 / 6 h 100% / >90% for 6 h / 8h 97.4% / 100% for 8 h 2 h Reference 1989 / 90 (Japan, Osaka) Yap, 1998 (Malaysia), Usavadee, 2001 (Thailand) Yap, 1998 In summary, field and cage studies show strong similarity of protection times for IR3535 vs. DEET against Aedes albopictus. Solutions of 20% - 25% provided protection for up to 8 hours.. 19

20 Performance comparison of IR3535 and DEET against Anopheles species Table 5: % Protection and mean protection times (h) of IR3535 and DEET against Anopheles species Method Species Formul. / Conc. Protection IR3535 Protection DEET Reference Field gambiae and funestus Ethanolic solution 25% 96.3% for 6 h 99.3% for 6 h Kuhlow, 1975 (West Africa) Cage / maculatus Ethanolic solution 25% 64% (1 h) / 70-40% (2-8 h) 100% (1 h) / 70-40% (2-8 h) Yap, 1998 Field (July) hyrcanus minimus sawad-wongporni maculates Ethanolic solution 20% 3 h (99%, 5 h) 1 h (98%, 5 h) Usavadee, 2001 (Thailand) Field (August) hyrcanus minimus sawad-wongporni maculates Ethanolic solution 20% 4 h (99%, 5 h) 2 h (99%, 5 h) Usavadee, 2001 (Thailand) Cage / dirus Ethanolic solution 20% 3.8 h 5.8 h Usavadee, 2001 (Thailand) Field darlingi albitarsus braziliensis Pump spray 15% 100% / 90% 3.8 h / 4.5 h - Hill, 2006 (Bolivian Amazon) Field darlingi albitarsus braziliensis Lotion 15% 100% / 90% 6.9 h / 7.7 h - Hill, 2006 (Bolivian Amazon) Field darlingi albitarsus braziliensis Lotion 15% 100% / 90% 6.0 h / 6.9 h - Hill, 2006 (Bolivian Amazon) 20

21 Summary Anopheles species In field studies at a concentration of 25%, IR3535 showed 5 hours protection against Anopheles hyrcanus, An. minimus, An. sawadwongporni, and An. maculatus, similar to DEET. However, DEET showed superior performance against Anopheles dirus in cage studies. In field studies, 15% formulations of IR3535 showed 5 hours protection against Anopheles darlingi, An. albitarsus, and An. braziliensis. Performance thus varies with formulation and species, and advanced formulation can improve performance against Anopheles species. 21

22 Performance comparison of IR3535 and DEET against Culex species Table 7: % Protection and protection times (h) of IR3535 and DEET against Culex species Method Species Formulation / Concentration Cage / pipiens Ethanolic solution 10% - 30% Mean Protection IR h Mean Protection DEET h Reference Shashin, 1998 Cage / quinque-fasciatus Cream 10% - 20% Cage / quinque-fasciatus Pump Spray 10% - 20% Cage/ quinquefasciatus Ethanolic solution 20% Cage/ tritaeniorhynchus Ethanolic solution 20% Field quinquefasciatus Ethanolic solution 25% Field sitiens Ethanolic solution (April) tritaenio-rhynchus 20% h h 13.7 h 14.8 h >98% for 8h 5h h h 12.7 h 14.5 h >98% for 8h 5h Cilek, 2004 Cilek, 2004 Usavadee, 2001 Usavadee, 2001 Yap, 1998 (Malaysia), Usavadee, 2001 (Thailand) Field (May) Field (July) gelidus quinquefasciantus tritaenio-rhynchus tritaenio-rhynchus sitiens Ethanolic solution 20% Ethanolic solution 20% 5h 99% for 5h 5h 5h Usavadee, 2001 (Thailand) Usavadee, 2001 (Thailand) 22

23 Summary Culex species Review of available data indicates equivalent performance of IR3535 and DEET against Culex species. In cage tests, 20% ethanolic solutions of IR3535 provided protection ranging from hours, while 20 25% ethanolic solutions provided at least 8 hours protection in the field (Yap 1998; Usavadee 2001) In cage tests, IR3535 protected against Culex species for twice as long as Aedes species 23

24 Conclusion

25 Nature inspired scientific approach in comparison to natural and pure synthetic repellent solutions Overall Conclusion The ester structure of the propionate provides two essential advantages. The evaporation is optimized to have a long lasting efficacy. In case of penetration this molecule shows a high safety level, because of a short metabolic degradation and quick excretion as a simple water soluble acid. Learning from nature provided a molecule which shows impressive performance in comparison to a natural and pure synthetic repellent solution. 25