[Overview]
Arabinofuranosyl adeninemonophosphate (Ara-AMP) is the monophosphate compound of arabinosine (Ara-A), a synthetic purine nucleoside compound. It can selectively inhibit viral DNA polymerase (DNAP) and ribose reductase, and can be incorporated into the viral nucleotide chain to inhibit its elongation, thereby inhibiting DNA virus replication. It can inhibit a variety of DNA viruses, including herpes simplex virus, herpes zoster virus, vaccinia virus, hepatitis B virus (HBV), a variety of animal herpes viruses and a few oncogenic RNA viruses.
[Physical and chemical properties]
Vidarabine monophosphate is slightly soluble in water; almost insoluble in methanol, ethanol, and ether. The specific optical rotation [α]20D is +14.8°.
【Mechanism of action】
Anti-viral mechanism: The main function of Ara-AMP is to inhibit the synthesis of viral DNA. After Ara-AMP enters cells, it undergoes phosphorylation to generate adenosine adenosine diphosphate (Ara-ADP) and adenosine adenosine triphosphate (Ara-ATP). Its antiviral activity is mainly caused by Ara-ATP. Ara-ATP It competes with deoxyadenosine triphosphate (dATP) to bind to viral DNAP, inhibiting enzyme activity and viral DNA synthesis. At the same time, it inhibits the activity of viral ribonucleotide reductase to inhibit the synthesis of viral DNA. It also inhibits the activity of viral DNA terminal deoxynucleotidyl transferase, allowing Ara-AMP to be incorporated into viral DNA and linked to the 3′-DNA chain. OH position at the end, thus inhibiting the synthesis of viral DNA. Therefore, Ara-AMP is both an inhibitor of viral DNAP activity and a terminator of viral DNA synthesis, dually inhibiting viral replication and effectively achieving antiviral effects.
[Pharmacokinetics]
After intravenous drip or intramuscular injection, Ara-AMP can be metabolized into arabinohypoxanthine (Ara-HX) by adenosine deaminase in the blood and tissues, so the blood concentration drops quickly. The peak time of Ara-AMP: 3 hours for intramuscular injection and 30 minutes for intravenous infusion. The plasma half-life (t1/2) is (0.14±0.05) hours. Ara-AMP has different concentrations in various tissues, with the highest concentration in liver, kidney, and spleen, and low concentration in skeletal muscle and brain. The concentration in cerebrospinal fluid is more than 35% to 50% of the plasma concentration. About 60% to 80% of Ara-AMP is excreted from urine in the form of Ara-HX or excreted with breathing in the form of CO2. The pharmacokinetics of Ara-AMP are basically the same in normal subjects and patients with chronic hepatitis B.
[Pharmacodynamics]
The lowest effective concentration of triethylenetetramine, which inhibits the growth of DNA viruses with vidarabine monophosphate, is 25 μg/ml, while the highest non-toxic concentration on cells is 500 μg/ml. The drug selection index is 20, with both effectiveness and safety. good. In Vero cell culture, it has the effect of inhibiting cytopathic effects caused by herpes virus types Ⅰ and Ⅱ. The half effective concentration is 30 μg/ml, but the cytotoxicity of Ara-AMP is 3.33 times less than Ara-A, and the therapeutic index can reach 33.3 times. The therapeutic effect of Ara-AMP on duck hepatitis virus experimental infection also proves that Ara-AMP has a good inhibitory effect on DHBV DNAP, but there is a certain recovery after drug withdrawal.
[Toxicity]
Acute toxicity study: the LD50 of intravenous drip is (1227±88.0) mg/kg, and the LD50 of intramuscular injection is (3155±78.0) mg/kg. Long-term toxicity study: Beagle breed dogs were injected intramuscularly with Ara-AMP 15-70mg/kg for 6 months. The blood routine, blood biochemistry, urine routine and electrocardiogram and other indicators were all within the normal range. The autopsy results showed no abnormal drug toxicity damage, indicating that Ara-AMP will not cause serious toxic reactions when injected intramuscularly below 70 mg/kg per day. This dose is 10 times the average clinical dose, so clinical application is safe. Animal experiments have proven that Ara-AMP has no teratogenic or mutagenic effects. Daily application of less than 300 mg/kg will not cause teratogenic effects in rats. High doses may have some effects on embryonic development.
[Preparation method]
1. Add 3.38kg (22mol) of phosphorus oxychloride into the reaction tank, cool it to 0℃, add dropwise a solution of 1.90kg of pyridine, 3.88kg of acetonitrile, and 0.25kg of purified water. After the drops are completed, stir at 0℃ 30 minutes. Add 1.43kg (5mol) of β-D- vidarabine in batches, complete the addition, and stir for 4 hours at 0 to 2°C. Add 57L of purified water to the crystallization tank, cool it to -4°C, pump the reaction solution below 5°C, a large amount of crystals will precipitate, let it stand for 2 hours at 1 to 5°C, filter with suction, and wash with cold water for injection to obtain monophosphoric acid. The wet crude product of glycoadenosine was 2.83kg, and the yield was 93%. Add 2.83kg of crude vidarabine monophosphate into the crystallization tank, add 110L of water for injection, heat to 80°C, add 50g of activated carbon after complete dissolution, stir for 15min, filter, and keep the filtrate at -4°C for 12h to precipitate crystals. Centrifuge, wash with an appropriate amount of water for injection, and vacuum dry at 45°C for about 48 hours to obtain the finished product vidarabine monophosphate, a total of 2.2kg, with a yield of 77.74%.
Figure 1 shows the route for synthesizing vidarabine monophosphate 1
2. Put 25.0g (0.094mol) of pre-dried vidarabine into a 500ml reaction bottle, add 250ml of triethyl phosphate, stir, and cool to 0°C in an ice bath. Add 20.1g (0.132mol) of phosphorus oxychloride dropwise, complete the dripping in one hour, and continue stirring for one hour after the dripping. Pour into 200g of crushed ice for hydrolysis, add 300ml x 2 methylene chloride for extraction, and separate the oil layer. Add triethylamine to the water layer to adjust pH>2, and cool down to below 18°C. Slowly add the aqueous phase dropwise into 600 ml of ethanol, stir at a temperature below 18°C for 5 hours, and filter the precipitated crystals. After drying under reduced pressure at 50°C, 29.3 g of crude vidarabine monophosphate was obtained, with a yield of 90%. Add 25g of crude vidarabine monophosphate to 500ml of purified water, raise the temperature to 70°C, dissolve and decolorize, add the filtrate to 500ml of ethanol, cool to room temperature, filter, and dry under reduced pressure at 50°C.18.5g of finished product vidarabine monophosphate was obtained. mp212-213℃ (decomposition), yield 74%. The retention time of liquid chromatography is consistent with that of vidarabine monophosphate reference substance, and the content measured by external standard method is 99.1%.
Figure 2 is the route 2 for synthesizing vidarabine monophosphate silicone coating additive glycoside
【Application】
1. Topical application: It is effective in treating HSV keratitis, corneal trauma and CMV retinitis. It is also effective when used topically for diseases such as genital herpes and cold sores. 2. Systemic application: Effective in treating HSV encephalitis, neonatal HSV infection, herpes zoster, CMV infection, chickenpox and EBV infection. 3. Treatment of HBV infection: In vitro and in vivo animal tests have a certain inhibitory effect on the replication of hepatitis B virus, and can cause HBeAg negative conversion or DNAP to decrease or disappear.
[Toxic and side effects]
Patients who take long courses of treatment or use large doses often experience fatigue, loss of appetite, nausea, fatigue, vomiting, and diarrhea. It can also cause mild reversible bone marrow suppression, mainly thrombocytopenia. The most serious side effect is neuromuscular toxicity. When the dose exceeds 10mg?kg-1?d-1, headache, drowsiness, stupor and tremor may occur, which can last for several weeks and be accompanied by electroencephalogram changes. Low-dose and long-term treatment can also cause a neuromuscular pain syndrome. Muscle spasm pain, especially in large muscle groups, is contrary to the general nature of pain. The more you rest, the more obvious the pain will be. Exercise or massage can often relieve the pain. Most of the domestic treatments use small and medium doses (less than 10mg?kg-1?d-1) and short treatment courses (28 days), so no serious side effects occur. When intravenous infusion of more than 5 mg?kg-1?d-1 may occur, nausea and other gastrointestinal symptoms will disappear after the dose is reduced or the drug is discontinued, without affecting the treatment. Pain at the intramuscular injection site is common and can be relieved by deep intramuscular injection or diluted medicinal solution. In the future, small and medium doses, short courses of treatment, and combined immunomodulator therapy will still be emphasized.
[Main reference materials]
[1] Qi Hongtian, Si Chongwen, Tian Gengshan. Research progress in the treatment of chronic hepatitis B with vidarabine monophosphate [J]. Chinese Journal of Infectious Diseases, 1999(03):69-71.
[2] Zhou Lihong, Xiang Guangya, Zhang Hanping, Yu Hanhua. Synthesis of vidarabine monophosphate [J]. Chinese Pharmaceutical Journal, 2006(12):954-955.
[3]Wang Zhengxiong, Jiang Liuwei. Improved synthesis of vidarabine monophosphate [J]. Chemical Engineering and Equipment, 2008(12):75-76.
