Adenosine deaminase (Ki = 2.5 pM)

Both pentostatin and ECP result in T-cell and host DC depletion and a shift of the remaining DC and T-cell population to a tolerogenic DC2 and T-regulatory population leading to the low rate of GVHD observed by Miller et al with a regimen combining ECP, pentostatin and 600 cGy TBI for HLA-identical and non-identical (5/6) allogeneic HCT.[1]

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The aim of this study was to evaluate the anti-trypanosomal effect of treatment with 3'-deoxyadenosine (cordycepin) combined with deoxycoformycin (pentostatin: inhibitor of the enzyme adenosine deaminase) in vitro by using mice experimentally infected with Trypanosoma evansi. In vitro, a dose-dependent trypanocidal effect of cordycepin was observed against the parasite[2].

Pentostatin (2 mg/kg) combined with cordycepin (2 mg/kg) was 100% effective against Trypanosoma evansi-infected mice. Increased levels of some biochemical parameters, especially liver enzymes, were accompanied by histological lesions of the liver and kidneys. Pentostatin alone has no effect on infected groups. All dogs developed granulocytopenia with granulocyte counts <500 cells/μL starting on day 4. Thrombocytopenia (<20,000 platelets/μL) begins on day 7 after HCT, with a nadir of 3000 to 14000 platelets/μL [1].

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In the in vivo trials, the two drugs were used individually and in combination of different doses. The drugs when used individually had no curative effect on infected mice. However, the combination of cordycepin (2 mg kg-1) and pentostatin (2 mg kg-1) was 100% effective in the T. evansi-infected groups. There was an increase in levels of some biochemical parameters, especially on liver enzymes, which were accompanied by histological lesions in the liver and kidneys. Based on these results we conclude that treatment using the combination of 3'-deoxyadenosine with deoxycoformycin has a curative effect on mice infected with T. evansi. However, the therapeutic protocol tested led to liver and kidney damage, manifested by hepatotoxicity and nephrotoxicity[2].

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Extracorporeal photopheresis (ECP) and the purine analog pentostatin exert potent immunomodulatory effects. We evaluated the use of these treatment modalities to prevent GVHD in a canine model of unrelated dog leukocyte Ag-mismatched hematopoietic cell transplantation, after conditioning with 920 cGy TBI. We have shown previously in this model that 36/40 dogs given MTX alone as postgrafting immunosuppression engrafted and that 25 of 40 dogs had severe GVHD and median survival of 21 days. In the current study, nine dogs received conditioning with 920 cGy TBI and postgrafting MTX either with ECP on days -2 to -1 alone (n=5) or ECP on days -6 and -5 combined with two doses of pentostatin (days -4 to -3) (n=4). Seven of nine dogs achieved engraftment. Six dogs developed severe acute GVHD (four in the group with ECP alone and two with pentostatin and ECP). We failed to demonstrate a positive impact of ECP and pentostatin for the prevention of GVHD compared with historical control dogs.[1]

Mixed leukocyte cultures (MLC) and natural killer (NK) cell cytotoxicity assay [1]
Mixed leukocyte cultures were used to assess the dogs’ cellular immune function before and after ECP as described previously. To evaluate NK cell activity before and after ECP, chromium release assays were performed as described previously.

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Chimerism analysis [1]
Donor and host cell chimerism were evaluated using a polymerase chain reaction (PCR) based assay of polymorphic (CA)n dinucleotide repeats with primers specific for informative microsatellite markers. Genomic DNA of the cells of interest was extracted, and PCR was performed under conditions described previously. The technique used enables to detect between 2.5% to 97.5% donor cell chimerism.

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Detection of apoptosis by Annexin V (Ax)/PI staining [1]
Apoptosis of cells exposed to ECP was assessed by flow cytometry with the use of Annexin V binding, which allows detection of phosphatidylserine on the cell surface of apoptotic cells. Briefly, after overnight incubation at 37 °C in 5% humidified atmosphere, cells were harvested, lysed, washed with PBS and incubated with Annexin V-FITC and propidium iodide (PI) according to the manufacturer’s manual. Cells were analyzed by flow cytometry by means of CellQuest Analysis software. A minimum of 10 000 events were counted per sample. Cells positive for Annexin V but negative for PI are in early apoptosis, cells double positive for Annexin V and PI are in late apoptosis. Results are reported as a percentage of annexin V-FITC positive cells.

DLA-nonidentical marrow grafts [1]
All recipient dogs were conditioned for transplantation by 920 cGy TBI at 7 cGy/minute using a linear accelerator. Dogs in group A1 received ECP administered on days −2 and −1 with TBI on day 0 and dogs in group A2 received ECP on days −6 and −5, intravenous (IV) infusion of pentostatin at a dose of 4mg/m2 on days −4 and −3, and TBI on day 0 (Table 1). Donor marrow cells from DLA-nonidentical donors were aspirated under general anesthesia through needles inserted into humeri and femora and stored in heparinized tissue culture medium at 4°C for no more than 6 hours.22 Within 4 hours of TBI, harvested marrow cells were infused IV into recipients at a median dose of 2.9 (range, 1.9 to 6.1) ×108 total nucleated cells (TNC)/kg. The day of marrow grafting was designated as day 0. In addition to marrow graft, recipients were given IV infusions of peripheral blood buffy coat cells obtained by leukapheresis from the marrow donor on days 1 and 2, at a median dose of 2.3 (range, 1.2 to 6.9) ×108 TNC/kg to ensure consistent hematopoietic engraftment. MTX, at a dose of 0.4 mg/kg intravenously was used as postgrafting immunosuppression and administered on days +1, +3, +6 and +11, then weekly thereafter until day 102.

Absorption, Distribution and Excretion
Not absorbed orally, crosses blood brain barrier.
In man, following a single dose of 4 mg/m2 of pentostatin infused over 5 minutes, approximately 90% of the dose was excreted in the urine as unchanged pentostatin and/or metabolites as measured by adenosine deaminase inhibitory activity.
68 mL/min/m2
Plasma concentrations of pentostatin following direct iv injection of 0.25 mg/kg daily for 4 or 5 days in a limited number of patients with advanced, refractory cancer ranged from approximately 3.2-9.7 ng/ml. Plasma concentrations appear to increase linearly with dose; in a study in patients with leukemia, plasma pentostatin concentrations determined 1 hour after administration of 0.25 or 1 mg/kg of the drug as a 30 min iv infusion averaged approximately 0.4 or 1.26 ug/ml, respectively.
No apparent correlation has been documented between mean or absolute plasma adenosine or deoxyadenosine concentrations and therapeutic or toxic responses to pentostatin; however, limited data suggest that there may be a correlation between response to the drug and the ratio of deoxyadenosine triphosphate to adenosine triphosphate in lymphoblasts. In addition, increases in plasma deoxyadenosine reportedly parallel the accumulation of deoxyadenosine triphosphate in erythrocytes and lymphoblasts, and there appears to be a correlation between toxicity and the ratio of deoxyadenosine triphosphate to adenosine triphosphate in erythrocytes.
Studies in animals indicate that pentostatin distributes rapidly to all body tissues, but the extent of drug accumulation in different tissues appears to vary among species. Following intraperitoneal injection in mice, the highest concentrations of the drug were found in the kidneys, liver, and spleen. In dogs, pentostatin tissue concentrations following iv administration were proportional to tissue adenosine deaminase activity, with the highest concentrations in the lungs, spleen, pancreas, heart, liver, and jejunum. Pentostatin reportedly enters erythrocytes via a facilitated transport system common to other nucleosides or by simple diffusion; efflux of the drug from cells has not been characterized, although the time course of pentostatin's effects (eg, adenosine deaminase inhibition) varies among different types of cells (eg, lymphocytes, erythrocytes).
Limited data in animals and humans indicate that pentostatin distributes relatively poorly into CSF, with peak CSF concentrations averaging approximately 10% of concurrent plasma concentrations. In a 6 yr old leukemia patient receiving pentostatin 0.25 mg/kg daily for 3 successive days by direct iv injection, serum and CSF (via lumbar puncture) pentostatin concentrations 4 hr after the initial dose were approximately 147 and 19 ng/ml, respectively, using an enzyme-inhibition titration assay; one hour after the third dose, corresponding serum and CSF concentrations were approximately 241 and 35 ng/ml, respectively.
For more Absorption, Distribution and Excretion (Complete) data for PENTOSTATIN (7 total), please visit the HSDB record page.

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Metabolism / Metabolites
Primarily hepatic, but only small amounts are metabolized.
Primarily hepatic, but only small amounts are metabolized.
Route of Elimination: In man, following a single dose of 4 mg/m2 of pentostatin infused over 5 minutes, approximately 90% of the dose was excreted in the urine as unchanged pentostatin and/or metabolites as measured by adenosine deaminase inhibitory activity.
Half Life: 5.7 hours (with a range between 2.6 and 16 hrs)

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Biological Half-Life
5.7 hours (with a range between 2.6 and 16 hrs)
Following iv administration of 4 mg/sq m of pentostatin as a single dose over 5 min in healthy individuals, the distribution half-life and terminal elimination half-life reportedly averaged 11 min and 5.7 hr, respectively. In a multiple dose study in a limited number of patients receiving 36 courses of pentostatin at a dosage of 4 mg/sq m iv, distribution half-life and terminal elimination half-life reportedly averaged 9.6 min (range: 3.1-48.5 min) and 4.9 hr, respectively. In other studies in a limited number of patients with advanced cancer, the distribution half-life averaged 17-85 min and the terminal elimination half-life averaged 2.6-15 hr following single iv doses of 0.1 or 0.25 mg/kg of pentostatin.
In patients with renal impairment (creatinine clearance less than 60 ml/min),the half-life of pentostatin averages approximately 18 hr.

Toxicity Summary
Pentostatin is a potent transition state inhibitor of adenosine deaminase (ADA), the greatest activity of which is found in cells of the lymphoid system. T-cells have higher ADA activity than B-cells, and T-cell malignancies have higher activity than B-cell malignancies. The cytotoxicity that results from prevention of catabolism of adenosine or deoxyadenosine is thought to be due to elevated intracellular levels of dATP, which can block DNA synthesis through inhibition of ribonucleotide reductase. Intracellular activation results in incorporation into DNA as a false purine base. An additional cytotoxic effect is related to its incorporation into RNA. Cytotoxicity is cell cycle phase-specific (S-phase).

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Toxicity Data
Mouse(iv): LD50 122 mg/kg
LD50=128 mg/kg (mouse)

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Interactions
Limited data suggest that concomitant therapy with pentostatin (4 mg/sq m every 2 weeks) and fludarabine (principally 10 mg/sq m daily for 4 days at 28 day intervals), a synthetic purine nucleoside, may be associated with severe and/or fatal pulmonary toxicity (eg, pneumonitis). In one study, 4 of 6 patients receiving the drugs concomitantly for treatment of refractory chronic lymphocytic leukemia reportedly developed such toxicity.
Although therapy with either pentostatin or allopurinol alone has been associated with the development of skin rash, limited evidence suggests that concomitant use of the drugs, compared with pentostatin therapy alone, in patients with refractory hairy cell leukemia is not associated with an increased incidence of rash. However, other toxicities, including abnormalities in renal or hepatic function, have been observed in a few patients receiving concomitant pentostatin and allopurinol. ... One patient reportedly developed a fatal hypersensitivity vasculitis while receiving pentostatin and allopurinol concurrently; however, a causal relationship to the drugs has not been established.
Pentostatin inhibits the degradation of vidarabine and enhances its cytotoxicity in cell culture and in animals with experimentally induced leukemia. In addition, limited data in patients with acute leukemia suggest that combined therapy with the drugs may be associated with increased plasma vidarabine concentrations and/or half-life and greater toxicity compared with pentostatin therapy alone. Although improvement and/or remission has been reported in a few patients with acute T cell lymphoblastic leukemia who received vidarabine and pentostatin concomitantly.

[1]. Extracorporeal photopheresis combined with pentostatin in the conditioning regimen for canine hematopoietic cell transplantation does not prevent GVHD. Bone Marrow Transplant. 2014 Sep;49(9):1198-204.

[2]. Cordycepin (3'-deoxyadenosine) pentostatin (deoxycoformycin) combination treatment of mice experimentally infected with Trypanosoma evansi. Parasitology. 2013 Apr;140(5):663-71.

Therapeutic Uses
Antibiotics; Antineoplastic Agents; Enzyme Inhibitors; Immunosuppressive Agents
Antibiotics, Antineoplastic; Enzyme Inhibitors; Immunosuppressive Agents
Antineoplastic
Pentostatin is used for the palliative treatment of hairy cell leukemia (leukemic reticuloendotheliosis) that responds inadequately to, or progresses during, interferon alfa therapy. Pentostatin has been designated an orphan drug by the US Food and Drug Administration (FDA) for the treatment of this condition. ... Pentostatin produces clinically important tumor regression or disease stabilization (complete or partial responses) in approximately 80-100% of patients with hairy cell leukemia, including in previously untreated patients (eg, those who have not undergone splenectomy or other therapy) as well as in those in whom splenectomy and/or therapy with other agents (eg, interferons, antineoplastic agents) have failed to control the disease (eg, those with progressive disease). In clinical studies in patients with interferon alfa-refractory hairy cell leukemia, a complete response to pentostatin therapy generally was defined as clearing of peripheral blood and bone marrow of hairy cells; normalization of organomegaly and lymphadenopathy; and recovery of hemoglobin concentration to at least 12 g/dl, platelet count to at least 100,000/cu mm, and granulocyte count to at least 1500/cu mm. A partial response was defined as a decrease of greater than 50% in the number of hairy cells in peripheral blood and bone marrow and a decrease of greater than 50% in organomegaly and lymphadenopathy; hematologic parameters for a partial response were the same as those for a complete response. Overall complete and partial responses of 58 and 28%, respectively, reportedly were observed in a limited number of these patients receiving pentostatin 4 mg/sq m iv every other week for 3 mo; responding patients continued treatment for another 3-9 mos. The median time to response in these patients reportedly was 4.7 mo (range: 2.9-24.1 mo). The median duration of response to pentostatin therapy in 2 clinical studies of patients with hairy cell leukemia reportedly exceeded 7.7 and 15.2 mo, with relapse occurring in approximately 15-20% of patients showing an initial response. For patients with progressive, postsplenectomy disease, pentostatin generally has been considered an alternative to interferon alfa or secondary therapy for interferon refractory disease since experience with interferon alfa has been more extensive to date. However, superiority of either drug or of other therapies remains to be established.
For more Therapeutic Uses (Complete) data for PENTOSTATIN (10 total), please visit the HSDB record page.

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Drug Warnings
Pentostatin is a toxic drug with a low therapeutic index, and a therapeutic response is not likely to occur without some evidence of toxicity. The drug must be used only under constant supervision by physicians experienced in therapy with cytotoxic agents. Most, but not all, adverse effects of pentostatin are reversible if detected promptly. When severe adverse effects occur during pentostatin therapy, the drug should be discontinued or dosage reduced and appropriate measures instituted. Pentostatin should be reinstituted with caution if at all, with adequate consideration of further need for the drug, and with awareness of possible recurrence of toxicity.
Patients with poor performance status appear to experience greater toxicity with pentostatin and should be treated with the drug only when the anticipated benefits outweigh the potential risks.
Hematologic function must be frequently and carefully monitored during and after pentostatin therapy, particularly during the first several courses of therapy in patients at increased risk of myelosuppression (eg, those with hairy cell leukemia). Initiation of pentostatin therapy in such patients can result in severe myelosuppression. If severe neutropenia continues beyond the initial cycles of pentostatin therapy, patients should be examined, including bone marrow examination, to determine the status of their disease. In addition, periodic monitoring for evidence of peripheral hairy cells should be performed in patients with this leukemia to evaluate the patient's response to therapy. Bone marrow aspirations and biopsies also may be required at 2 to 3 mo intervals.
Patients receiving pentostatin should be observed closely for signs of nonhematologic (eg, neurologic) toxicity. If severe adverse reactions occur, the drug should be withheld and appropriate corrective measures taken as indicated. Therapy with pentostatin should be temporarily withheld or discontinued in patients who develop evidence of neurologic toxicity.
For more Drug Warnings (Complete) data for PENTOSTATIN (11 total), please visit the HSDB record page.

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Pharmacodynamics
Pentostatin is an antineoplastic anti-metabolite used in the treatment of several forms of leukemia including acute nonlymphocytic leukemia and hairy cell leukemia. Anti-metabolites masquerade as purine or pyrimidine - which become the building blocks of DNA. They prevent these substances becoming incorporated in to DNA during the "S" phase (of the cell cycle), stopping normal development and division. It is a 6-thiopurine analogue of the naturally occurring purine bases hypoxanthine and guanine. Intracellular activation results in incorporation into DNA as a false purine base. An additional cytotoxic effect is related to its incorporation into RNA. Cytotoxicity is cell cycle phase-specific (S-phase).

C11H16N4O4

268.2691

268.117

C, 49.25; H, 6.01; N, 20.88; O, 23.86

53910-25-1

439693

White crystals from methanol/water
White to off-white solid

1.8±0.1 g/cm3

673.1±65.0 °C at 760 mmHg

220-225ºC

360.9±34.3 °C

0.0±2.2 mmHg at 25°C

1.793

-2.16

4

6

2

19

356

4

O1[C@]([H])(C([H])([H])O[H])[C@]([H])(C([H])([H])[C@]1([H])N1C([H])=NC2[C@@]([H])(C([H])([H])N=C([H])N([H])C1=2)O[H])O[H]

FPVKHBSQESCIEP-KDXUFGMBSA-N

InChI=1S/C11H16N4O4/c16-3-8-6(17)1-9(19-8)15-5-14-10-7(18)2-12-4-13-11(10)15/h4-9,16-18H,1-3H2,(H,12,13)/t6-,7+,8+,9-/m0/s1

(R)-3-((2S,4S,5R)-4-hydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl)-3,6,7,8-tetrahydroimidazo[4,5-d][1,3]diazepin-8-ol

Deoxycoformycin; CI825; CI-825; Deoxycoformycin; Nipent; 53910-25-1; 2'-Deoxycoformycin; PD-ADI; Pentostatina; Pentostatine; CI 825; PD81565; PD-81565; PD 81565; covidarabine; deoxycoformycin; pentostatine. brand name: Nipent.

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)

H2O : ~100 mg/mL (~372.76 mM)
DMSO : ≥ 50 mg/mL (~186.38 mM)

Solubility in Formulation 1: ≥ 2.08 mg/mL (7.75 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 (7.75 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 (7.75 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.)