propan-2-amine:1-(heteropolycycle-6-yl)ethenone transaminase

Endpoint summary

Description of key information

ω-Transaminase has not been engineered for gastric stability and would be digested/hydrolyzed when ingested. Like all proteins, enzymes that have not been engineered for low pH and/or gastric stability, will denature or degrade into amino acids.

Further live animal testing to investigate the acute oral toxicity of ω-Transaminase is scientifically unnecessary as there is sufficient information for deriving an adequate qualitative hazard assessment.

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Additional information

In general, enzymes are of very low toxicity due to ready biodegradability and very low bioavailability. In traditional acute toxicity testing, mortality has been the endpoint. However, because enzymes show very low toxicity, extremely high doses that are far above human exposure levels typically have been applied. Therefore, acute toxicity studies are not considered to provide appropriate knowledge and are as such not a relevant test system for enzymes (1).

Additionally, enzyme preparations have a very long history of being used as processing aids in the production of foods, such as in the dairy, wine, brewing and distilling, starch, and baking industries. Also, enzymes are used in various other industries e.g. detergent, textile, paper, leather, fuel ethanol, and animal feed (2). The production organism used in the manufacture of ω-Transaminase has a long history of safe use.

ω-Transaminase has not been engineered for gastric stability (low pH and gastric media) and would be digested/hydrolyzed when ingested. Like all proteins, enzymes that have not been engineered for low pH and/or gastric stability, will denature or degrade into amino acids.

Industrial enzymes have a remarkably good safety profile with a long history of safe manufacture and use, with only some enzyme causing respiratory sensitization. Oral toxicity is not typically associated with non-protease enzymes (2). The Enzyme Technical Association (ETA) sponsored a survey of oral toxicity study data on enzymes produced using protein engineering (3). ETA reviewed toxicity data on protein engineered non-protease enzymes produced by 30 individual strains. This survey found no reports of adverse effects in any of the 47 individual oral toxicity studies that were performed (3). ETA identifies only protease enzymes as having acute oral toxicity (4).

CDX-6114 is a phenylalanine enzyme developed using the same engineering work structure with manufacturing based on the same manufacturing platform as ω-Transaminase. Several nonclinical safety pharmacology and toxicology studies have been conducted with CDX-6114 in rats, and non-human primates. The results of the safety pharmacology studies, which evaluated gastrointestinal propulsion, respiratory function and neurobehavioral parameters in the rat resulted in no treatment-related safety findings of concern following a single oral dose of up to 720 mg/kg bw. Similarly, evaluation of cardiovascular function, including blood pressure, heart rate, qualitative and quantitative assessment of the electrocardiogram in the cynomolgus monkey indicated no safety concerns following oral dosing up to 720 mg/kg bw.

The two 14-day toxicity studies of CDX-6114 were designed in compliance with the International Conference on Harmonization (ICH) guidance M3(R2) titled “Nonclinical Safety Studies for the Conduct of Human Clinical Trials and Marketing Authorization for Pharmaceuticals”, as well as other relevant ICH guidelines, especially ICH-S6(R1). Both studies were conducted in compliance with Good Laboratory Practices (GLP) regulations. These animal toxicology studies were conducted using repeated oral daily dosing of CDX 6114 for up to 14 days in both rats and cynomolgus monkeys. All standard toxicology parameters, including a detailed histological examination of all standard tissues as well as a more extensive evaluation of the gastrointestinal tract, were performed. In both male and female rats and monkeys, oral administration via gavage of 720 mg/kg bw/day of CDX-6114 for 14 consecutive days and showed no drug-related signs of toxicity; therefore, the no observed adverse effect level (NOAEL) was considered to be at least 720 mg/kg bw/day in both species (5).

CDX-7108 is a lipase enzyme developed using the same engineering work structure with manufacturing based on the same manufacturing platform as ω-Transaminase. CDX 7108 was well tolerated in both species at doses up to and including 408 mg/kg bw/day (rats), 424 mg/kg bw/day (monkeys) following 5 consecutive days of dosing, and up to and including 369 mg/kg bw/day in rats and monkeys following 28 days of dosing. No adverse effects were reported for any measured parameter including body weight, body weight gain, food consumption, clinical pathology (hematology, coagulation, clinical chemistry, and urinalysis), ophthalmology or neurobehavior (rats only) and electrocardiography (monkeys only). Furthermore, in both species administered CDX 7108 for 28 days at doses ≤ 369 mg/kg bw/day, there were no CDX-7108 related macroscopic or microscopic findings at the end-of-dosing on Day 28 or in animals held for a 2 week treatment-free recovery period (6).

Finally, ω-Transaminase enzymes are found in terrestrial and aquatic vertebrates (7) and are therefore commonly ingested with food. Based on the weight of evidence presented, further live animal testing to investigate the acute oral toxicity of ω-Transaminase is scientifically unnecessary as there is sufficient information for deriving an adequate qualitative hazard assessment.

[1] Enzymes REACH Consortium (2010). Data waiving argumentation for technical enzymes.
[2] https://amfep.org/about-enzymes/safety/
[3] ETA. 2009. An industry-sponsored survey on genotoxicity and oral toxicity study data from the enzymes produced using protein engineering
[4] https://www.enzymetechnicalassociation.org/enzymes/safe-handling-enzymes/
[5] Study numbers 0440RC130.001, 0437RC130.001, 0440SC130.002 and 0437RC130.001
[6] Study numbers CDX1783-R-2005, CDX1783-R-2021, CDX1783-NHP-2006 and CDX1783-NHP-2022
[7] Setini, A., Pierucci, F., Senatori, O. and Nicotra, A., 2005. Molecular characterization of monoamine oxidase in zebrafish (Danio rerio). Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, 140(1), pp.153-161. doi: 10.1016/j.cbpc.2004.10.002.

Justification for classification or non-classification

ω-Transaminase has not been engineered for gastric stability and would be digested/hydrolyzed when ingested. Like all proteins, enzymes that have not been engineered for low pH and/or gastric stability, will denature or degrade into amino acids. Further live animal testing to investigate the acute oral toxicity of ω-Transaminase is scientifically unnecessary as there is sufficient information for deriving an adequate qualitative hazard assessment. As such, ω-Transaminase does not meet the CLP criteria for acute toxicity classification.