The genetic toxicity problem of the drug is analyzed.

In recent years, the problem of gene toxicity is one of the important contents of drug development, and even after the market evaluation of drug quality, and even become the industry's "flash point", "burning point"! However, most of the peers in the problem of genetic toxicity, most lying only in the warning structure, 1.5ug concept, rarely from the point of view of pharmacological toxicology to think about the true meaning of genetic poison.
so, organize this article, hope to make common progress.
01, what is genetic poison? Genotoxicity can be divided into four categories: DNA damage, gene mutation, change of chromosome structure and change in chromosome number.
broad erythrotoxicity refers to the harmful effectofs of changes in genetic information caused by genetic poisons caused by specific changes in the molecular structure of the genome of biological cells;
and narrow genetic toxicity refers to the effect of genetic poison on DNA (or chromosomes).
02, the history of genetic toxicology 1927, genetic toxicology originated in H.J. Muller's pioneering work, his research found that radiation not only increases the frequency of mutations, but also induced mutant or phenotype is exactly the same as observed without radiation.
, the induced mutation reaction must be evaluated according to the underlying mutation.
1938, Sax, based on Muller's research, found that X-rays can induce chromosomal structural distortion in purple dew pollen particles.
in the absence of a complete lack of DNA structure and chromosomal composition, Sax and his colleagues found that exchange within or between chromosomes requires at least two major damages in the nucleus.
also found that the total dose of exposure to X-rays remained the same, but the amount of exposure to x-rays decreased by prolonging the exposure time, or in a few parts of exposure, resulting in a decrease in the amount of chromosomal distortion.
1946, Auerbach and his colleagues reported that nitrogen mustard can induce fruit fly mutations that are the same as X-ray-induced mutations, and that people began to consider the genetic effects of chemicals.
by the 1970s, there were two events that allowed the use of inductic data to assess risk.
Miller and his colleagues have found that chemical carcinogens can form stable covalent derivatives in vitro and in vivo with DNA, RNA and proteins.
the same period, the second development changed the field of genetic toxicology, which Ames (1975) and his colleagues established for a simple, inexpensive mutation test using typhoid salmonella, which detects the response mutations of histine gene base caused by chemicals and can be used in combination with a foreign-aid Editing S9 metabolic system.
Ames test has been widely used today, and further in vivo micronuclear tests in the 1970s, after decades of development and application, there are now the use of image analysis, flow cytometers and laser scanning cytometers and other automated systems to detect micronucleometers.
followed, in 1994, Gatehouse and others published a series of recommendations for the implementation of the Ames test at the International Symposium on The Standardization of Genotoxicity Tests at ResearchMutation, and in 1997 the OECD developed guidelines for the Ames test, further promoting the standardization and application of the method.
Today, institutions such as ICH, OECD and others have developed and promulgated guidelines for genetic toxicology research, and are constantly being updated... 03. China's domestic release of the guidelines China on October 23, 2007 issued the "technical guidelines for drug genotoxicity research."
has emphasized in the drafting and review of the Guiding Principles that the Guiding Principles are only principled guidance and only reflect the perceptions of the time! Researchers should not mechanically copy the guiding principles, but should give full play to the initiative of subjectivity, actively track the progress of disciplines and promote research work.
March 2018, the State Food and Drug Administration (FDA) organized the revision of the Technical Guidelines for Drug Genotoxicity Research, and announced the repeal of the Technical Guidelines for Drug Genetic Toxicity Research issued by the former State Food and Drug Administration in 2007.

China's recently issued guidelines Source: Standard Test Combination Guiding Principles state: According to the genetic endpoint of the test test, the detection method can be divided into three categories, namely, gene mutation, chromosomal aberration, DNA damage, according to the test system, can be divided into invivied tests and in vitro tests.
standard test combinations should reflect different genetic endpoints, including in vivo and in vitro trials, and should include the following: 1) a bacterial response mutation test (also known as the Ames test), which has been shown to detect related genetic changes and most rodent and human genotoxic agents;
Table 1: Domestic Guidelines Standard Test Portfolio
04, ICH Guidelines 1995 and 1997 ICH issued guidelines S2A (specific guidelines for drug genotoxicity testing), S2B (genotoxicity: drug genotoxicity test standard combination); In June 006, the revision of the Guidelines for Genetic Toxicity was initiated and several meetings were held in the United States, the European Union and Japan to discuss the revision, which was finally completed in November 2011, completing the fourth process of THE ICH and recommending the adoption and use of the ICH management trio (EU, UNITED States, Japan).

. Ich's S2 (R1) Guidelines Standard Trial Combination Guidelines state that choosing one has more historical application experience is partly due to the fact that the portfolio is recommended by the S2A and S2B guidelines.
, however, the reasons for choosing one and choosing two are considered equally appropriate are as follows: When the in vitro mammalian cell test results are positive, two clear negative results of two well-implemented in vivo tests (using appropriate tissues and showing adequate exposure) are considered sufficient to demonstrate the lack of invivitivity potential in vivo, so the test strategy for both invivum tests is the same as the additional test of the positive results of in vitro tests.
Table 2: ICH S2 (R1) Guiding Principles Standard Test Portfolio
05, Historical Lybin Events of Drug Genetic Toxicity In June 2007, Roche Pharmaceuticals launched HIV protease inhibition of methicatinininine in the European market, because of the discovery of a classic genetictoxic impurity in its products - methyl sulfonate ethyl ester, EMA suspended all its sales in Europe. the introduction of ethyl methate
is due to the fact that ethanol is not completely dried during the cleaning of production equipment and remains, which reacts with methyl sulfonate in a non-raw material of methicillonate to form methyl sulfonate.

the chemical structure of methicillonave nephyl al-Nephinave Roche, after being asked to completely solve the pollution problem, also needs to supplement toxicity research data to better assess the risk to patients from genetically toxic impurities of methicillonaue nafeinon.
it was not until Roche fully resolved the issues that the EMA reinstated the relevant authorization of nayofa in the European market.
after the event, drug regulatory agencies around the world have put forward more clear regulations and requirements for genetically toxic impurities, therefore, domestic and foreign pharmaceutical enterprises in the new drug research and development process is also paying more and more attention to the control and detection of genetic ally toxic impurities.
06, the common gene toxicity (impurity) problem in small molecule drugs So, how to recognize and control the genetic toxic impurities? The structure of genetically toxic impurities is diverse, and for the vast majority of impurities, there is often insufficient toxicity or carcinogenic research data, making it difficult to classify them.
in the absence of safety data support, most regulations and guidelines use "warning structures" as markers for distinguishing between common and genetically toxic impurities.
for impurities containing warning structures, (Q) SAR prediction and invivity and carcinogenicity studies should be carried out, or impurity levels should be controlled below the toxicological concern threshold (TTC).
specific details on the results of the genetic impurity warning can refer to the warning structure "Development of the structural alerts for the in vivo micro sass nucleus inrodents" issued by the European Union, or enter the Carcinogenic Potency Database (CPDB), which contains a list of thousands of carcinogens, structural, CAS numbers, action sites, TTC values and a series of information.

the legendary Virtual Structure of Super Carcinogens (CNKI) ICH, the first guidelines for the study of chemical API impurities, Q3A (R2), and the guidelines Q3B (R2) for the study of formulation impurities, in which "further structural identification is required for the first time for potential impurities that can produce strong pharmacological activity or toxicity, even if their content is less than 0.1%."
in a later revised version, it was further clarified that "the potential genotoxic impurities in API" and "the need to develop lower testing limits according to the actual situation for highly toxic genotoxic impurities" were not clearly stated on the issue of genotoxic impurities and their research and control, and there were no specific requirements for their research principles, limit requirements and control strategies.
the EMEA Human Drug Commission (CHMP) has introduced the Guidelines for The Limits of Toxicimpurity, introducing the concept of an acceptable risk intake, the toxicology concern threshold (TTC).
set a limit tTC (1.5 ?g/day), which is equivalent to 1.5 ?g per person per day, and is considered an acceptable risk for most medicines (less than one in 100,000 risk of cancer in life).
based on this threshold, the acceptable level of impurities in the active drug is calculated according to the expected daily intake.
note that TTC is just a method of probability and has certain risks.
if there is a genotoxic impurity, its toxicity is unknown, assuming that its daily intake is within the TTC range, then its probability of cancer will be below 10-5, so the limit value (TTC) does not mean that there is no risk at all.
PS: There are different thresholds and algorithms for different types of drugs. Table 3 of the
: Classification of genetically toxic impurities in medicines
07, M7 Guiding Principles M7 were adopted by the ICH Steering Committee in June 2014 in Phase 4 of the ICH Process;
M7 is designed to provide a feasible framework for the identification, classification, definition and control of mutated impurities to limit potential cancer risks.
also intended to supplement ICH Q3A (R2), Q3B (R2) and M3 (R2) to support non-clinical safety studies for clinical trials and market.
PS:M7 does not apply to RAW drugs and preparations defined in the ICH S9 range for advanced cancer indications.
M7 again gives TTC, TD50, 1.5 ?g/day and other concepts and data, while highlighting the issue of genetic toxic impurities after the market changes drugs;
Table 4: After the market drug changes to face the problem of genetic toxicimpurity
08, the conclusion of gene toxicity problem, the most fundamental or safety problem, and whether a substance is safe, whether there is genetic toxicity, to rely on tests and data to prove.
so far, we have known a lot of genetic toxic substances, also know how to judge the warning structure, but there is still an NDMA event! And no matter what the cause of the incident, the result is the quality of the drug problem! But when quality is in question, as a pharmaceutical practitioner, reflecting more should be where the problem lies? In the end, how should we make "safe, effective, quality controllable" drugs! In summary, that is, for the author's current understanding of the content of genetic poison.
References: 1. ICH Tripartite Coordination Guidelines . 2. Guideline S2 (R1) for drug genotoxicity testing and results analysis for human use. 3. ICH. S2 (R1): Guidance on genotoxicity testing and data for the pharmaceuticals for human use. 2011 4. Ich. M3 (R2): Non-clinical safety for studies the conduct of the human clinical trials and marketing authorization for pharmaceuticals. 2009 5. Fda. Guide for industry and review staff: Recommended gets to integration of the genetic toxicology study results. 2006 6. OECD. Guideline for testing of the chemicals No.471: The Orc reverse change test.1997 7. OECD. Guideline for testing of the chemicals No.473: In Vitroso mammalian chromosomal aberration test. 2016 8. OECD. Guideline for testing of chemicals No. 488: Transgenicrodent som.