Stable heavy isotopes of hydrogen, carbon, and other elements have been incorporated into drug molecules, primarily as quantitative tracers during drug development. Studies involving the use of deuterium-labeled drugs in humans have shown that these compounds may have certain advantages over their non-deuterated counterparts. Deuterated drugs have attracted attention due to their potential to affect the pharmacokinetic and metabolic characteristics of drugs. Deuttetrabenazine is the first deuterated drug approved by the US Food and Drug Administration. Deuttetrabenazine is indicated for the treatment of chorea associated with Huntington's disease as well as tardive dyskinesia. Ongoing clinical trials indicate that many other deuterated compounds are being evaluated for use as therapeutics in humans, rather than simply as research tools. [1] Ritonavir (ABT 538) is an inhibitor of CYP3A4-mediated testosterone 6β-hydroxylation with a mean Ki of 19 nM. It also inhibits tolbutamide hydroxylation with an IC50 of 4.2 μM. [2] Ritonavir (ABT 538) was found to be a potent inhibitor of CYP3A-mediated biotransformations (nifedipine oxidation with IC50 of 0.07 mM, 17alpha-ethynylestradiol 2-hydroxylation with IC50 of 2 mM; terfenadine hydroxylation with IC50 of 0.14 mM). Ritonavir is also an inhibitor of reactions mediated by CYP2D6 (IC50=2.5 mM) and CYP2C9/10 (IC50=8.0 mM) [3]. Ritonavir resulted in increased cell viability in uninfected human PBMC cultures. Ritonavir significantly reduced the susceptibility of PBMCs to apoptosis, associated with lower levels of caspase-1 expression, reduced annexin V staining, and decreased caspase-3 activity in uninfected human PBMC cultures. Ritonavir inhibits PBMC and monocyte-induced tumor necrosis factor (TNF) production in a time- and dose-dependent manner at non-toxic concentrations[4]. Ritonavir inhibits p-glycoprotein-mediated extrusion of saquinavir with an IC50 of 0.2 μM, indicating that ritonavir has a high affinity for p-glycoprotein[5]. Ritonavir effectively inhibits the human liver microsomal metabolism of ABT-378 with a Ki of 13 nM. Ritonavir combined with ABT-378 (ratios of 3:1 and 29:1) inhibits CYP3A (IC50=1.1 and 4.6 μM), although less potent than ritonavir (IC50=0.14 μM)[6].

Deuterated compounds may, in some cases, offer advantages over nondeuterated forms, often through alterations in clearance. Deuteration may also redirect metabolic pathways in directions that reduce toxicities. The approval of additional deuterated compounds may soon follow. Clinicians will need to be familiar with the dosing, efficacy, potential side effects, and unique metabolic profiles of these new entities.

[1]. Impact of Deuterium Substitution on the Pharmacokinetics of Pharmaceuticals. Ann Pharmacother. 2019 Feb;53(2):211-216.

[2]. Differential inhibition of cytochrome P450 isoforms by the protease inhibitors, ritonavir, saquinavir and indinavir. Br J Clin Pharmacol. 1997 Aug;44(2):190-4.

[3]. Bardoxolone and bardoxolone methyl, two Nrf2 activators in clinical trials, inhibit SARS-CoV-2 replication and its 3C-like protease. Signal Transduct Target Ther. 2021 May 29;6(1):212.

[4]. Potent inhibition of the cytochrome P-450 3A-mediated human liver microsomal metabolism of a novel HIV protease inhibitor by ritonavir: A positive drug-drug interaction. Drug Metab Dispos. 1999 Aug;27(8):902-8.

[5]. Cytochrome P450-mediated metabolism of the HIV-1 protease inhibitor ritonavir (ABT-538) in human liver microsomes. J Pharmacol Exp Ther. 1996 Apr;277(1):423-31.

[6]. HIV protease inhibitor ritonavir: a more potent inhibitor of P-glycoprotein than the cyclosporine analog SDZ PSC 833. Biochem Pharmacol. 1999 May 15;57(10):1147-52.

[7]. HIV-1 protease inhibitor ritonavir modulates susceptibility to apoptosis of uninfected T cells. J Hum Virol. 1999 Sep-Oct;2(5):261-9.

C37H40D8N6O5S2

728.99

Typically exists as solid at room temperature

Ritonavir-d8; ABT 538-d8; RTV-d8

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)