DNA synthesis ( IC50 = 67 nM ); DNA synthesis (HSB2 cells) ( IC50 = 0.44 μM ); DNA synthesis (ALL-SIL cells) ( IC50 = 1.24 μM ); DNA synthesis (JURKAT cells) ( IC50 = 2.15 μM )

The AUC for ara-G plasma is 20 mM minutes, and the AUC for Nelarabine plasma is 2.82 mM minutes. Nelarabine in plasma has a terminal half-life of 25 minutes, a central volume of distribution of 1.1 L/kg, and a clearance of 42 mL/minutes/kg. Ara-G has a central volume of distribution of 1.4 L/kg and a terminal half-life of 182 minutes in plasma. Nelarabine and ara-G have terminal half-lives of 77 and 232 minutes, respectively, in CSF. AUCcsf:AUCplasma for ara-G is 23%, and for Nelarabine it is 29%. Due to their comparatively short half-lives, elarabine and ara-G do not accumulate with daily infusions.[4]

The MTT assay is used to assess drug resistance in the HSB2, ALL-SIL, JURKAT, and PER-255 cell lines. After four days of incubation, elsarabine's concentration is examined in triplicate. The drug resistance metric known as the IC50, or drug concentration that inhibits cell growth by 50%, is employed. The data show the average of two to six separate experiments conducted at different times. When even the highest dose in a given experiment fails to produce 50% cytotoxicity, the IC50 is noted as being double the highest concentration that was tested.

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The in vitro efficacies of three new drugs--clofarabine (CLOF), nelarabine (NEL) and flavopiridol (FP) - were assessed in a panel of acute lymphoblastic leukaemia (ALL) cell lines. The 50% inhibitory concentration (IC50) for CLOF across all lines was 188-fold lower than that of NEL. B-lineage, but not T-lineage lines, were >7-fold more sensitive to CLOF than cytosine arabinoside (ARAC). NEL IC50 was 25-fold and 113-fold higher than ARAC in T- and B-lineage, respectively. T-ALL cells were eightfold more sensitive to NEL than B-lineage but there was considerable overlap. FP was more potent in vitro than glucocorticoids and thiopurines and at doses that recent phase I experience predicts will translate into clinical efficacy. Potential cross-resistance of CLOF, NEL and FP was observed with many front-line ALL therapeutics but not methotrexate or thiopurines. Methotrexate sensitivity was inversely related to that of NEL and FP. Whilst NEL was particularly effective in T-ALL, a subset of patients with B-lineage ALL might also be sensitive. CLOF appeared to be marginally more effective in B-lineage than T-ALL and has a distinct resistance profile that may prove useful in combination with other compounds. FP should be widely effective in ALL if sufficient plasma levels can be achieved clinically.[1]

Nelarabine (35 mg/kg, approximately 700 mg/m2) was administered over 1 h through a surgically implanted central venous catheter to four nonhuman primates. Blood (four animals) and ventricular CSF (three animals) samples were obtained at intervals for 24 h for determination of nelarabine concentrations, which were measured by HPLC-mass spectrometry. Results: The nelarabine plasma AUC (median+/-s.d.) was 2,820+/-1,140 microM min and the ara-G plasma AUC was 20,000+/-8,100 microM min. The terminal half-life of nelarabine in plasma was 25+/-5.2 min and clearance was 42+/-61 ml/min/kg. The terminal half-life of ara-G in plasma was 182+/-45 min. In CSF the terminal half-life of nelarabine was 77+/-28 min and of ara-G was 232+/-79 min. The AUCcsf:AUCplasma was 29+/-11% for nelarabine and 23+/-12% for ara-G.[4]

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35 mg/kg; i.v. injection

Healthy adult male rhesus monkeys

Absorption, Distribution and Excretion
Following intravenous administration of nelarabine to adult patients with refractory leukemia or lymphoma, plasma ara-G Cmax values generally occurred at the end of the nelarabine infusion and were generally higher than nelarabine Cmax values, suggesting rapid and extensive conversion of nelarabine to ara-G. Mean plasma nelarabine and ara-G Cmax values were 5.0 ± 3.0 mcg/mL and 31.4 ± 5.6 mcg/mL, respectively, after a 1,500 mg/m2 nelarabine dose infused over 2 hours in adult patients. The area under the concentration-time curve (AUC) of ara-G is 37 times higher than that for nelarabine on Day 1 after nelarabine IV infusion of 1,500 mg/m2 dose (162 ± 49 mcg.h/mL versus 4.4 ± 2.2 mcg.h/mL, respectively). Comparable Cmax and AUC values were obtained for nelarabine between Days 1 and 5 at the nelarabine adult dosage of 1,500 mg/m2, indicating that nelarabine does not accumulate after multiple dosing. There are not enough ara-G data to make a comparison between Day 1 and Day 5. After a nelarabine adult dose of 1,500 mg/m2, intracellular Cmax for ara-GTP appeared within 3 to 25 hours on Day 1. Exposure (AUC) to intracellular ara-GTP was 532 times higher than that for nelarabine and 14 times higher than that for ara-G (2,339 ± 2,628 mcg.h/mL versus 4.4 ± 2.2 mcg.h/mL and 162 ± 49 mcg.h/mL, respectively).
Nelarabine and ara-G are partially eliminated by the kidneys. Mean urinary excretion of nelarabine and ara-G was 6.6 ± 4.7% and 27 ± 15% of the administered dose, respectively, in 28 adult patients over the 24 hours after nelarabine infusion on Day 1.
Nelarabine and ara-G are extensively distributed throughout the body. For nelarabine, V_ss values were 197 ± 216 L/m² in adult patients. For ara-G, V_ss/F values were 50 ± 24 L/m² in adult patients.
Renal clearance averaged 24 ± 23 L/h for nelarabine and 6.2 ± 5.0 L/h for ara-G in 21 adult patients. Combined Phase I pharmacokinetic data at nelarabine doses of 199 to 2,900 mg/m² (n = 66 adult patients) indicate that the mean clearance (CL) of nelarabine is 197 ± 189 L/h/m² on Day 1. The apparent clearance of ara-G (CL/F) is 10.5 ± 4.5 L/h/m² on Day 1. For pediatric patients receiving at a dose of 104 to 2,900 mg/m², the combined Phase I pharmacokinetic data indicate that the mean clearance (CL) of nelarabine is 259 ± 409 L/h/m², 30% higher than in adult patients. The apparent clearance of ara-G on day 1 is also higher in pediatric patients than in adult patients, estimated to be 11.3 ± 4.2 L/h/m².

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Metabolism / Metabolites
The principal route of metabolism for nelarabine is O-demethylation by adenosine deaminase to form ara-G, which undergoes hydrolysis to form guanine. In addition, some nelarabine is hydrolyzed to form methylguanine, which is O-demethylated to form guanine. Guanine is N-deaminated to form xanthine, which is further oxidized to yield uric acid. Ring opening of uric acid followed by further oxidation results in the formation of allantoin. Ring opening of uric acid followed by further oxidation results in the formation of allantoin.

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Biological Half-Life
Nelarabine and ara-G are rapidly eliminated from plasma with a mean half-life of 18 minutes and 3.2 hours, respectively, in adult patients. For pediatric patients, the half-life of nelarabine and ara-G are 13 minutes and 2 hours, respectively. Because the intracellular levels of ara-GTP were so prolonged, its elimination half-life could not be accurately estimated.

Hepatotoxicity
In clinical trials, serum enzymes elevations occurred in a small proportion of patients treated with nelarabine when given as sole therapy for refractory or relapsed acute leukemia. These elevations are generally mild-to-moderate, transient and asymptomatic. Elevations of aminotransferase levels above 5 times the upper limit of normal are reported in 4% of patients with leukemia receiving nelarabine. The elevations rarely require dose adjustment or delay in therapy. Cases of clinically apparent liver injury due to nelarabine have been reported to occur, but few details are available. A single case report of clinically apparent liver injury attributed to nelarabine has been published with rapid onset of jaundice during a second course of nelarabine, a hepatocellular pattern of enzyme elevations, no immunoallergic or autoimmune features and a rapid improvement upon stopping.
Likelihood score: E* (unproven but suspected cause of clinically apparent liver injury).

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Protein Binding
Nelarabine and ara-G are not substantially bound to human plasma proteins (< 25%) in vitro, and binding is independent of nelarabine or ara-G concentrations up to 600 µM.

[1]. Br J Haematol . 2007 Apr;137(2):109-16.

[2]. Expert Opin Pharmacother . 2006 Sep;7(13):1791-9.

[3]. Blood . 2007 Jun 15;109(12):5136-42.

[4]. Cancer Chemother Pharmacol . 2007 May;59(6):743-7.

Pharmacodynamics
Nelarabine is a prodrug of the cytotoxic deoxyguanosine analogue 9-ß-D-arabinofuranosylguanine (ara-G). Nelarabine is demethylated by adenosine deaminase (ADA) to ara-G. Ara-G is then transported into cells, where it undergoes three phosphorylation steps, resulting in the formation of ara-G triphosphate (ara-GTP). In the first phosphorylation step, ara-G is converted to ara-G monophosphate (ara-GMP). Ara-GMP is then monophosphorylated by deoxyguanosine kinase and deoxycytidine kinase to ara-G diphosphate, and then subsequently to the active ara-G triphosphate (ara-GTP). Ara-GTP is the one that exerts the pharmacological effect. Pre-clinical studies have demonstrated that targeted T-cells possess marked sensitivity to the agent. Since T lymphoblasts have a higher expression of deoxycytidine kinase, ara-G preferentially accumulates in T cells over B cells, thus showing higher toxicity to T lymphoblasts.[A2331,AA2334,2335]

C11H15N5O5

297.27

297.107

C, 44.44; H, 5.09; N, 23.56; O, 26.91

121032-29-9

3011155

White to off-white solid powder

2.0±0.1 g/cm3

721.0±70.0 °C at 760 mmHg

209-217ºC

389.9±35.7 °C

0.0±2.4 mmHg at 25°C

1.829

-0.58

4

9

3

21

377

4

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

IXOXBSCIXZEQEQ-UHTZMRCNSA-N

InChI=1S/C11H15N5O5/c1-20-9-5-8(14-11(12)15-9)16(3-13-5)10-7(19)6(18)4(2-17)21-10/h3-4,6-7,10,17-19H,2H2,1H3,(H2,12,14,15)/t4-,6-,7+,10-/m1/s1

(2R,3S,4S,5R)-2-(2-amino-6-methoxypurin-9-yl)-5-(hydroxymethyl)oxolane-3,4-dio

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)

Solubility in Formulation 1: ≥ 2.5 mg/mL (8.41 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 25.0 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: ≥ 2.5 mg/mL (8.41 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 25.0 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: ≥ 2.5 mg/mL (8.41 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 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: 1% DMSO +30% polyethylene glycol+1% Tween 80 : 30 mg/mL

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Solubility in Formulation 5: 5 mg/mL (16.82 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication (<60°C).

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