10-12 April 2019: The OECD Conference on RNAi based pesticides provided an overview on the current status and future possibilities for the regulation of externally applied dsRNA-based products that are proposed for use as pesticides. The event facilitated exchanges between policy makers, academia, industry on their implications in health, environment, and regulation.

1. EFSA’s activities on the risk
assessment of RNAi-based
GM crops
Nikoletta Papadopoulou, Fernando Álvarez-
Alfageme, Yann Devos, Anna Lanzoni, Matthew
Ramon, Claudia Paoletti, Elisabeth Waigmann
GMO Unit
11 April 2019

2.  EFSA is responsible to perform a pre-market risk assessment (RA) of
GMOs with regard to human and animal health and the environment
 RA is performed by the GMO Panel, ad-hoc experts, and GMO Unit
scientists
 GM CROPS: soybean, maize, oilseed rape, cotton
 MAJOR TRAITS (single or stacked): insect resistance and herbicide
tolerance
RISK ASSESSMENT OF GMO IN EUROPE

3. RNAi technology application in GM plants:
• is used for down-regulation of specific target genes in planta or in
insect pests
• dsRNA or artificial miRNA can be used to elicit a silencing response
• Use of dsRNA more advanced for market applications
RNAi IN GM PLANT APPLICATIONS

4. 1. KEY OUTCOMES FROM EFSA WORKSHOP ON RNAI, 2014
2. EFSA PROCUREMENTS: MC (2017), ERA (2018), FF (2019)
3. GMO PANEL STRATEGY FOR ASSESSMENT OF RNAi OFF-TARGET
ANALYSIS (2017)
4. EFSA SCIENTIFIC OPINION ON GM MAIZE RESISTANT TO WESTERN
CORN ROOTWORM (WCR) (2018)
REVIEW OF EFSA’S ACTIVITIES ON RA OF
RNAi-BASED GM CROPS

5. Risks and issues related to the 3 main areas
of GMO risk assessment:
Molecular
characterisation (MC)
Food and feed (FF)
uses
Environmental risk
assessment (ERA)
EFSA 2014 WORKSHOP ON RNAi AND RA
REPORT: International scientific workshop ‘Risk assessment considerations for RNAi-based GM plants’ (4–5 June 2014,
Brussels, Belgium). EFSA supporting publication 2014:EN-705, 38 pp.

6. KEY MESSAGES FOR MC-1
Off-target effects in the RNAi based GM plant:
 Bioinformatics useful to predict potential off-target effects on plant genes
 NGS useful to map the composition of siRNA pools; but some technical
limitations should be considered
 siRNAs spread systemically in plants; dsRNA spread is unclear
 RNA-dependent RNA polymerases (RdRP) amplify the siRNA signal in
plants, facilitating systemic spread
 Silencing effect throughout the plant should be considered even in
tissue-specific expression of siRNA

7. Processing of ingested RNAi molecules:
 dsRNA produced in plants can be processed upon oral ingestion by
some organisms (e.g. insects and worms)
 Controversial views on the likelihood of intake and activity of mature
miRNAs from plants in mammals and insects
RNAi molecule intake, processing and mode-of-action may differ
between different taxonomic groups review baseline information
(Paces et al., 2017)
KEY MESSAGES FOR MC-2

8. Ingestion of RNAi-based GM plants by humans and livestock- Hazard
identification/characterization:
Uptake of ncRNAs molecules through intestinal barrier
• low absorption of naked or formulated ncRNAs in feeding studies
• Some evidence that dietary miRNAs are absorbed (controversial)
Uptake of ncRNAs through the respiratory route
• from pollen: too large for systemic exposure, contains low amounts of
RNAi
• No evidence of absorption of ncRNAs from the air by inhalation
KEY MESSAGES FOR FF-1

9. Ingestion of RNAi-based GM plants by humans and livestock-
Hazard identification/characterization:
• Target homology across species
• Unintended (off-target) effects
• Immune stimulation
 Review of baseline information by Davalos et al. under finalization
KEY MESSAGES FOR FF-2

10. Considerations on the usefulness of animal studies for food/feed risk
assessment based on:
 Properties of dsRNA (absorption, stability, degradation)
 Physical barriers
 No evidence for toxicity of RNAi molecules after ingestion
 not supported by scientific knowledge on dsRNA properties and
mode of action
KEY MESSAGES FOR FF-3

11. Dietary intake of dsRNA
• Key molecule ingested by arthropods
• Uptake of 21nt siRNAs not observed in WCR midgut cells (Bolognesi
et al., 2012)
• Plant-derived siRNAs considered less relevant for arthropods than dsRNA
 Multiple factors can affect RNAi efficiency in arthropods
(reviewed by Christiaens et al. 2018)
KEY MESSAGES FOR ERA-1

12. • Any dsRNA or siRNA molecule with sufficient homology to an
arthropod mRNA could trigger an off-target effect
• Substantial overlap in 21 bp regions necessary to trigger an off-
target effect, but some mismatches allowed
 Bioinformatics data may provide supplementary information to
predict off-target effects and support species selection for RA, but
cannot at present replace toxicity studies
KEY OUTCOMES FOR ERA-2
Off target effects on non-target arthropods of ingested RNAi-
based GM material

13. Considerations on Testing approach and Test Substance
• Ecotoxicological studies:
• dsRNA has been used as test material (e.g., Bachman et al., 2016),
as mostly dsRNA is ingested by arthropods
• Measurement endpoints and life stages Selection dependent on
trait and target gene; sublethal effects should also be measured
• NTO testing with in planta material, to capture unanticipated
unintended effects
 Tiered approach remains appropriate
KEY OUTCOMES FOR ERA-3

14.  Casacuberta JM, Devos Y, du Jardin P, Ramon M, Vaucheret H and
Nogué F, 2015. Biotechnological uses of RNA interference in plants:
Risk assessment considerations. Trends in Biotechnology, 33, 145–
147
 Ramon M, Devos Y, Lanzoni A, Liu Y, Gomes A, Gennaro A and
Waigmann E, 2014. RNAi-based GM plants: Food for thought for risk
assessors. Plant Biotechnology Journal, 12, 1271–1273
 Roberts AF, Devos Y, Lemgo GNY and Zhou X, 2015. Biosafety
research for non-target organism risk assessment of RNAi-based GE
plants. Frontiers in Plant Sciences, 6, 958
Food for thought for risk assessors

15. Literature review of baseline information to
support the RA of RNAi-based GM plants
Molecular
characterisation
(Paces et al., 2017)
Food and feed (FF)
(Davalos et al., under
finalization)
Environmental risk
assessment (ERA)
(Christiaens et al.,
2018)
THREE EFSA PROCUREMENTS

16.  Paces et al., 2017 summarized knowledge on MC RA related aspects:
• Mode of action of dsRNA and miRNA pathways in animal and plants
• Potential non-target gene regulation
• siRNA pools in plant tissues and the siRNA silencing effect
 Davalos et al. reviews information relevant to FF RA from ncRNA-based
GM plants, focusing on:
• Stability and degradation of ncRNAs after oral ingestion
• Passage of ncRNAs from food to humans and animals via the
gastrointestinal (GI) tract and other barriers,
• Systemic or immune system effects
OUTCOME OF THE LITERATURE REVIEW

17.  Christiaens et al., 2018 reviewed the scientific information relevant
to the ERA RA focusing on:
• Oral ingestion and spread of RNAi in arthropods, nematodes,
annelids and molluscs
• Mechanisms of dsRNA-, siRNA- and miRNA-elicited gene silencing
• Environmental fate of ncRNAs
• Non-target effects and their mechanisms
Bioinformatics data may provide supplementary information to predict off-target
effects and support species selection for RA, but cannot at present replace toxicity
studies
OUTCOME OF THE LITERATURE REVIEW-ERA

18. Internal note on the strategy and technical aspects for small RNA plant
off-target bioinformatics studies (Annex II, Minutes of the 118th GMO
Panel meeting) - considerations on:
 the search algorithm parameters (e.g. complementarity mismatches)
 the number of different small RNAs showing significant similarity to
the same potential off target transcript
 the established or predicted function of the potential off-targets that
could impact on the safety of the GM plant and/or derived products as
food/feed, or in the environment
The search for small RNA off-targets in the GM plant could have value for
the risk assessment of GM plants
PREDICTION OF RNAi OFF-TARGET GENES
IN PLANTS

19. RA OF RNAi-BASED GM MAIZE
Assessment of genetically modified maize MON 87411 for food and feed
uses, import and processing, under Regulation (EC) No 1829/2003
(application EFSA‐GMO‐NL‐2015‐124)
 Resistance to western corn rootworms (Diabrotica spp.) by:
I. the expression of a modified version of the Bacillus thuringiensis
cry3Bb1 gene, and
II. a DvSnf7 dsRNA expression cassette;
 Tolerance to glyphosate‐containing herbicides by the expression of a
cp4 epsps gene.
240nt long dsRNA used to down‐regulate the Snf7 gene transcript in
WCR via RNAi, leading to pest mortality after consumption

20. RA OF RNAi -BASED GM MAIZE
MC
 Assessment for off-target genes in plant;
 Measure of DvSnf7 dsRNA levels in different tissues, not considered
relevant for RA.
FF
 28-day tox study provided for maize MON 87411, not assessed: a)
usefulness not scientifically justified; b) deviating from OECD TG
407.
ERA
 No/limited exposure of GM maize expected

21. 1. Current framework for GMO RA (guidelines and regulatory data requirements)
is sufficient for RA of RNAi-based GM plant RA.
2. Additional considerations on:
 MC: Analysis of off-target effects in plant genes adds value to RA;
 FF: Animal studies for assessment of dsRNA toxicity in FF RA is not justified
based on current scientific knowledge;
 ERA: dsRNA market applications exclude cultivation in Europe; if NT
arthropods feed directly on dsRNA-expressing plants, or consumption of
plant-fed herbivores is expected, further information for exposure assessment
will be needed.
CONCLUSIONS

22. GMO Panel Experts
GMO Unit colleagues:
 Yann Devos
 Anna Lanzoni
 Matthew Ramon
ACKNOWLEDGEMENTS

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