5-chloro-1,3-dihydro-1-(4-piperidinyl)-2H-benzimidazol-2-one

Endpoint summary

Description of key information

T000990 (CAS 53786-28-0) is characterised as a slight beige odourless powder having a moderate molecular weight (251.72 g/mol), a particle size of 117.459 µm (Mass Median Aerodynamic Diameter or MMAD), a moderate water solubility (0.549 g/L), a moderate partition coefficient (log Kow of -0.6 at pH 7, ionized form; log Kow of 0.3 at pH 13, unionized form) and a low volatility (vapour pressure of <2.9 E-11 kPa at 25°C).

Based on its average molecular weight, average partition coefficient and water solubility, dissolution of the substance is expected. Absorption can be limited due to its high pKa value. Furthermore, a combined 28-day repeated dose toxicity with the reproductive/developmental toxicity screening test showed adverse effects at 150 mg/kg (highest dose). Therefore, the oral absorption factor is assumed to be 50%.

Due it its low volatility and high MMAD, inhalation of the substance is expected to be low. Since its molecular weight is >200 and its water solubility is moderate, absorption will be low and the respiratory absorption factor is assumed to be 50%.

Dermal absorption is expected bo be low since T000990 is a solid and rather hydrophilic. Furthermore, an acute dermal study showed only local effects and the substance is not irritating to skin. Therefore, the dermal absorption factor is set to 10%.

T000990 is expected to distribute through the body but not expected to be distributed into cells since it's slightly hydrophilic.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

50

Absorption rate - dermal (%):

10

Absorption rate - inhalation (%):

50

Additional information

Toxicokinetic assessment of T000990

T000990 (CAS 53786-28-0), is a slight beige odourless powder with a moderate molecular weight (251.72 g/mol), a particle size of 117.459 µm (Mass Median Aerodynamic Diameter or MMAD), a moderate water solubility (0.549 g/L), a moderate partition coefficient (log Kow of -0.6 at pH 7, ionized form; log Kow of 0.3 at pH 13, unionized form) and a low volatility (vapour pressure of <2.9 E-11 kPa at 25°C).

The backbone of T000990 is a benzimidazolone group, with a chlorine and piperidinyl group attached. Due to the presence of secondary amine functional group, the substance is considered a base. This implies that the product has the potential to ionize in acidic-neutral environment. From the calculated pKa values based on the Perrin calculation method (Brekelmans, 2016) it can be confirmed that the test item is (partly) ionized in environments with a pH <12.7.

No toxicokinetic data (animal or human studies) are available on this substance. The data present in this dossier are based on physicochemical and toxicological parameters and will allow a qualitative assessment of the toxicokinetic behaviour of T000990.

Absorption

Oral/GI absorption:

T000990 is considered favourable for absorption due to the fact that its molecular weight of < 500 g/mol, its log Pow value between -1 and 4 and its moderate water solubility leading to dissolution of the substance into the gastrointestinal fluids and absorption through passive diffusion. However, the fact that the substance is assumed to be ionised to a large extent at neutral pH can limit the absorption along the gastrointestinal tract. It is generally assumed that the absorption along the gastrointestinal tract predominantly takes place in the small intestine.

In a combined 28-day repeated dose toxicity with the reproductive/developmental toxicity screening test (OECD 422, van Otterdijck, 2016), T000990 was administered by daily oral gavage to male and female Wistar Han rats at dose levels of 15, 50 and 150 mg/kg/d. Results showed that at 150 mg/kg/d, adverse findings were present as changes in clinical appearance, body weight loss or reduced weight gain, lower food intake, lower fore- and hindlimp grip strength and lower motor activity. Adverse histopathological findings were noted in the liver (hepatocellular vacuolation), thymus (cortical atrophy) and thyroid gland (follicular hypertrophy).

At 150 mg/kg, a lower number of implantation sites was recorded which was considered adverse, taking into account developmental results (such as a lower gestation index at 150 mg/kg).

Based on the physicochemical properties and the results of the toxicity studies, the oral absorption factor is set to 50%.

 

Respiratory absorption:

Because T000990 has a low volatility, the availability of the powder for inhalation as a vapour is limited. As its mass median aerodynamic diameter is larger than 100 µm, the majority of the solid particles won’t have a large potential to be inhaled. Based on those conclusions, the absorption of T000990 through inhalation is expected to be very low.

The moderate log Kow value indicates favourable absorption directly across the respiratory tract epithelium by passive diffusion. However,the moderate water solubility and molecular weight > 200 will cause the substance to be retained within the mucus and transported out of the respiratory tract rather than being absorbed after inhalation.

Therefore, the respiratory absorption factor is estimated to be 50%.

Dermal absorption:

Since T000990 is a solid, the product will not readily be taken up by the skin in comparison to liquid products. The dry product will have to dissolve into the surface moisture of the skin before uptake can take place. In order to cross the skin, the compound must first penetrate into the stratum corneum. From its moderate logKow value of -0.6 (at pH 7) it can be derived that the substance is rather hydrophilic causing only a minimal passage across the lipid rich environment of the stratum corneum leading to low dermal uptake. Subsequently the substance can partition from the stratum corneum into the epidermis based on its moderate water solubility (0.549 g/L). .

An acute dermal toxicity study (Latour, 2016) where 2000 mg/kg of T000990 was applied to 5 male and 5 female Wistar rats, demonstrated only local effects and no indications of dermal toxicity, confirming the expectations described above. Furthermore, the substance is not irritating to skin based on an in vivo acute dermal irritation study (Sanders, 2004).

As a result, the dermal absorption factor is set to 10%.

Distribution

Due to its moderate water solubility and moderate molecular weight T000990 is expected to distribute through the body due to diffusion through aqueous channels and pores. Since the substance is slightly hydrophilic (logKow<0 at pH 7), the substance is not likely to distribute into cells.

Accumulation

Since T000990 is a moderately water soluble and hydrophilic substance, no or only limited accumulation is expected within the body.

Metabolism

Once absorbed, T000990 might undergo phase I biotransformation (including reduction, oxidation or hydroxylation) followed by conjugation reactions (phase II) such as glucuronidation and sulfation, increasing the hydrophilicity.

Excretion

Given the moderate molecular weight, moderate water solubility and ionization of the molecule at the pH of urine, T000990 and its metabolites (such as conjugated glucuronides) will most likely be excreted through the urine. Most of the metabolites will have been filtered out of the blood by the kidneys, though a small amount may enter the urine directly by passive diffusion. Furthermore, T000990 may also be actively secreted through the bile.