dGK Km = 8.0 μM)[2]
Ara-G targets DNA polymerases and is incorporated into DNA during replication. After cellular uptake, ara-G is phosphorylated to ara-GTP by deoxyguanosine kinase (dGK) and other kinases. Ara-GTP competes with dGTP for incorporation into DNA by DNA polymerases. Once incorporated, the arabinose sugar moiety prevents further DNA chain elongation, leading to DNA strand termination and apoptosis. T-cells are selectively sensitive to ara-G due to their higher dGK activity and lower levels of the degrading enzyme 5'-nucleotidase.

9-β-D-arabinofuranoguanine is selectively toxic to cultured T lymphoblasts, as they are able to accumulate higher levels of cytotoxicity relative to B- and alymphoblastoid cells. Cause cell death[1][2]. 9-β-D-arabinofuranoguanine (0-1000 μM; 72 h) is cytotoxic and has an IC50 of MOLT-4, MOLT-4/Ara-G500 and MOLT-4/Ara-G900. Ara-GTP[1].
Ara-G is a potent inhibitor of DNA synthesis in T-cells. It is incorporated into DNA and causes DNA chain termination. The compound is selectively toxic to T-cell lines compared to other cell types due to differential expression of dGK and 5'-nucleotidase. Ara-G has been shown to induce apoptosis in T-ALL cell lines. The compound's activity is concentration-dependent and correlates with ara-GTP accumulation.

In vivo, ara-G (as the prodrug nelarabine) is effective for the treatment of T-cell acute lymphoblastic leukemia and T-cell lymphoblastic lymphoma. Nelarabine is FDA-approved for this indication. After administration, nelarabine is rapidly demethylated to ara-G, which is then phosphorylated to the active ara-GTP. The compound's selective toxicity to T-cells makes it effective against T-cell malignancies with manageable systemic toxicity.

9-beta-D-Arabinofuranosylguanine (araG) is a nucleoside analogue that elicits cytotoxicity through the intracellular accumulation of its 5'-triphosphate, araGTP, araG is selectively toxic to cultured T-lymphoblasts due to their ability to accumulate higher levels of the cytotoxic metabolite, araGTP, relative to B- and null lymphoblastoid cells. In an effort to determine whether this selectivity may occur in leukemic cells in vivo, we have investigated the metabolism of araG in MOLT-4 T-lymphoblasts. MGL-8 B-lymphoblasts, HL-60 promyelocytes, and HUT-102 mature T-cells and compared it to that in freshly isolated leukemic cells from patients. MOLT-4 T-lymphoblasts were 50- to 380-fold more sensitive to growth inhibition with araG and accumulated 80-fold higher levels of araGTP than any of the other cell lines studied. Incubation of peripheral blood from patients with leukemia with araG for 4 h demonstrated that T-acute lymphocytic leukemia cells accumulated significantly higher median levels of araGTP than did acute myelogenous leukemia or chronic lymphocytic leukemia cells (187 versus 72 and 31 pmol of araGTP per 10(7) cells, respectively), araGTP accumulation was not dependent on the rate of degradation of araG during the incubation. In contrast, araG did not exhibit similar selective growth inhibition, nor did the accumulation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate in the freshly isolated leukemic cells differ significantly among T-acute lymphocytic leukemia, acute myelogenous leukemia, chronic lymphocytic leukemia, and non-T-, non-B-cell acute lymphocytic leukemia cells. These results demonstrate that the selective metabolism of araG observed in cultured cell lines was representative of the metabolism in freshly isolated leukemic cells. Furthermore, degradation of araG did not limit the accumulation of araGTP in the leukemic cells. These results indicate that araG may be valuable as a selectively acting chemotherapeutic agent in T-lymphoblastic malignancies[1].

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9-beta-D-arabinofuranosylguanine (Ara-G) is an important and relatively new guanosiue analog with activity in patients with T-cell malignancies. The biochemical and molecular events leading to resistance to Ara-G are not fully understood. Therefore we generated two Ara-G-resistant human MOLT-4 leukemic cell lines with different levels of resistance. The mitochondrial enzyme deoxyguanosine kinase (dGK) and the nuclear/cytosol enzyme deoxycytidine kinase (dCK) are key enzymes in the activation of Ara-G. Decreased levels of dGK protein and mRNA were found in both resistant cell sublines. The activity of dCK was decreased in the subline with higher resistance to Ara-G and these cells were highly cross-resistant to other nucleosides activated by dCK. Increased activity of the mitochondrial enzyme thymidine kinase 2 was observed in both resistant sublines and this could be related to the dGK deficiency. In search for other resistance mechanisms it was found that the resistant cells overexpress the mdr1 gene, while no changes were detected in the levels of multidrug resistance-associated protein 1 through 6, lung resistance-associated protein or topoisomerase IIalpha or IIbeta. Taken together, our findings demonstrate that multiple mechanisms are involved in the acquired resistance to Ara-G. However, low expression of dGK is the most apparent alteration in both resistant cell lines. Partial deficiency of dCK was found in the subline cells with higher resistance to Ara-G. Furthermore, Ara-G may select for high expression of the multidrug resistance (mdr1) which could be a specific resistance mechanism but more likely part of an overall cellular stress response.[2]
Ara-G activity is assessed in vitro using T-ALL cell lines or other relevant cells. Cells are treated with varying concentrations of ara-G for 24-72 hours. Cell viability is assessed using MTT or CellTiter-Glo assays. Ara-GTP accumulation is measured by HPLC or LC-MS/MS. DNA chain termination is assessed by measuring DNA synthesis inhibition using [3H]-thymidine incorporation or BrdU incorporation. Apoptosis is evaluated by Annexin V/PI staining and caspase activity assays.

Cell viability assay[2]
Cell Types: MOLT-4 and Ara-G resistant sublines: MOLT-4/Ara-G500 and MOLT-4/Ara-G900
Tested Concentrations: 0 4.2, 452 and 777 μM respectively[2] . -1000 μM
Incubation Duration: 72 h
Experimental Results: Cytotoxic to MOLT-4, MOLT-4/Ara-G500 and MOLT-4/Ara-G900 cells, with IC50 of 4.2, 452 and 777 μM respectively.
Cellular assays for ara-G employ T-ALL cell lines (e.g., CCRF-CEM, Jurkat) or primary T-ALL cells. Cells are seeded in multi-well plates and treated with varying concentrations of ara-G for 24-72 hours. Cell viability is assessed using MTT or CellTiter-Glo assays. Ara-GTP levels are measured by HPLC or LC-MS/MS. DNA synthesis is assessed by [3H]-thymidine incorporation. Apoptosis is evaluated by Annexin V/PI staining. The selectivity of ara-G for T-cells versus other cell types is assessed using B-cell lines or other non-T cells.

In vivo efficacy of ara-G (as nelarabine) is evaluated in mouse xenograft models using T-ALL cell lines. Tumor-bearing mice are treated with nelarabine via intravenous or oral administration at various doses. Tumor volumes are measured every 2-3 days. Pharmacodynamic markers such as ara-GTP levels are measured in tumor tissues. Body weight and clinical signs are monitored for tolerability. Nelarabine has been evaluated in clinical trials and is FDA-approved for T-ALL and T-LBL.

Ara-G has molecular formula C10H13N5O4 and molecular weight 267.24. It has CAS number 38819-10-2. The compound is a nucleoside analog and the active metabolite of nelarabine. It is soluble in water and DMSO. The compound should be stored at -20°C for long-term stability. Ara-G is a research-use compound and a reference standard for nelarabine studies.

Nelarabine (the prodrug of ara-G) has been associated with neurotoxicity, including severe neurological adverse events. Other adverse effects include myelosuppression, nausea, vomiting, and fatigue. The compound should be used with caution in patients with pre-existing neurological conditions. Dose adjustments may be required for patients with renal or hepatic impairment. Ara-G itself has similar toxicity concerns as the prodrug.

[1]. Shewach DS, et al. Differential metabolism of 9-beta-D-arabinofuranosylguanine in human leukemic cells. Cancer Res. 1989 Dec 1;49(23):6498-502.
[2]. Lotfi K, et al. Low level of mitochondrial deoxyguanosine kinase is the dominant factor in acquired resistance to 9-beta-D-arabinofuranosylguanine cytotoxicity. Biochem Biophys Res Commun. 2002 May 24;293(5):1489-96.

9-β-D-arabinofuranylguanine is a purine nucleoside in which guanine is linked to arabinofuranyl sugar via a β-N(9)-glycosidic bond. It inhibits DNA synthesis and leads to cell death. It has antitumor activity and is also a DNA synthesis inhibitor. It is a β-D-arabinoside and a purine nucleoside.
Ara-G (9-β-D-arabinofuranosylguanine) is a deoxyguanosine analog and the active metabolite of nelarabine, a prodrug used for the treatment of T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL). Ara-G is selectively toxic to T-cells due to their higher deoxyguanosine kinase activity. The compound is incorporated into DNA during replication, leading to DNA chain termination and apoptosis. Nelarabine is FDA-approved for T-ALL and T-LBL.

C10H13N5O5

283.2407

283.091

C, 42.41; H, 4.63; N, 24.73; O, 28.24

38819-10-2

135499520

Typically exists as White to off-white solids at room temperature

2.3±0.1 g/cm3

775.9ºC at 760 mmHg

225°C(lit.)

423.1ºC

1.955

-1.72

5

7

2

20

446

4

O1[C@]([H])(C([H])([H])O[H])[C@]([H])([C@@]([H])([C@]1([H])N1C([H])=NC2C(N([H])C(N([H])[H])=NC1=2)=O)O[H])O[H]

NYHBQMYGNKIUIF-FJFJXFQQSA-N

InChI=1S/C10H13N5O5/c11-10-13-7-4(8(19)14-10)12-2-15(7)9-6(18)5(17)3(1-16)20-9/h2-3,5-6,9,16-18H,1H2,(H3,11,13,14,19)/t3-,5-,6+,9-/m1/s1

2-amino-9-[(2R,3S,4S,5R)-3,4-dihydroxy-5-(hydroxymethyl)oxolan-2-yl]-1H-purin-6-one

38819-10-2; 9-beta-d-Arabinofuranosylguanine; 9-(beta-D-Arabinofuranosyl)guanine; Ara-G; Ara-G hydrate; 9-Arabinofuranosylguanine; 9-beta-Arabinosylguanine; Guanine arabinoside;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: This product requires protection from light (avoid light exposure) during transportation and storage.

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

DMSO : ~125 mg/mL (~441.32 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (7.34 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (7.34 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
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.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (7.34 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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