Ulodesine (formerly also known as BCX4208) is a novel and potent inhibitor of purine nucleoside phosphorylase (PNP) with the potential to be used for the treatment of psoriasis and gout. It inhibits PNP with an IC50 of 0.5 nM. It is currently being developed by Biocryst as a once-daily oral, chronic treatment for gout. Ulodesine acts at the upstream of xanthine oxidase in the purine metabolism pathway to reduce the production of serum uric acid (sUA) by inhibiting PNP. BCX-4208 is currently in early clinical investigation in psoriasis and gout.

Physicochemical Properties

Molecular Formula	C12H16N4O3
Molecular Weight	264.28044
Exact Mass	264.122
CAS #	548486-59-5
Related CAS #	548486-59-5
PubChem CID	135449518
Appearance	White to off-white solid powder
Hydrogen Bond Donor Count	4
Hydrogen Bond Acceptor Count	5
Rotatable Bond Count	3
Heavy Atom Count	19
Complexity	389
Defined Atom Stereocenter Count	2
SMILES	C1C(C(CN1CC2=CNC3=C2N=CNC3=O)O)CO
Chemical Name	7-(((3R,4R)-3-hydroxy-4-(hydroxymethyl)pyrrolidin-1-yl)methyl)-3H-pyrrolo[3,2-d]pyrimidin-4(5H)-one
Synonyms	BCX4208;BCX-4208;BCX 4208; DADMe-immucillin H
HS Tariff Code	2934.99.9001
Storage	Powder-20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month
Shipping Condition	Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Biological Activity

Targets	Ulodesine (BCX4208) targets purine nucleoside phosphorylase (PNP) (Ki = 1.3 nM for human recombinant PNP; IC50 = 3.2 nM for mouse PNP, IC50 = 2.8 nM for rat PNP) [1] Ulodesine (BCX4208) exhibits high selectivity for PNP, with no significant inhibition of other purine metabolic enzymes (xanthine oxidase, adenosine deaminase, hypoxanthine-guanine phosphoribosyltransferase) at concentrations up to 10 μM (Ki > 1000 nM for all) [1][2]
ln Vitro	1. In recombinant enzyme activity assays, Ulodesine (BCX4208) potently inhibits human PNP with a Ki of 1.3 nM, mouse PNP with an IC50 of 3.2 nM, and rat PNP with an IC50 of 2.8 nM; maximal inhibition (>95%) of PNP activity is achieved at 10 nM [1] 2. Ulodesine (BCX4208) (1–100 nM) dose-dependently reduces the production of uric acid in human hepatoma HepG2 cells treated with hypoxanthine (a purine precursor); 10 nM Ulodesine decreases uric acid levels by 60% compared to vehicle-treated cells [1] 3. In human peripheral blood mononuclear cells (PBMCs), Ulodesine (BCX4208) (5 nM) inhibits PNP-mediated catabolism of inosine and guanosine, leading to a 4-fold increase in intracellular purine nucleoside levels and a 50% reduction in hypoxanthine release (a substrate for xanthine oxidase) [1] 4. Ulodesine (BCX4208) shows no cross-reactivity with xanthine oxidase (XO) at concentrations up to 10 μM, confirming no direct inhibition of XO-mediated uric acid synthesis [2]
ln Vivo	PNP is potently inhibited by ulodesine (iv), having an IC50 value of 2.293 nM/L[1]. Ulodesine (iv) removes uric acid buildup in the mouse model's blood[1]. 1. In a novel mouse hyperuricemia model induced by combined administration of oxonic acid (XO inhibitor, 250 mg/kg i.p.) and hypoxanthine (500 mg/kg p.o.), oral Ulodesine (BCX4208) (1, 3, 10 mg/kg) dose-dependently reduces serum uric acid (sUA) levels by 25%, 48%, and 72% respectively at 4 hours post-dosing [1] 2. Ulodesine (BCX4208) (10 mg/kg p.o.) maintains sUA reduction for >8 hours in hyperuricemic mice, with sUA levels remaining 55% lower than baseline at 8 hours; in contrast, allopurinol (10 mg/kg p.o.) shows a maximal sUA reduction of 40% at 2 hours, with effects fading by 6 hours [1] 3. In rats with diet-induced hyperuricemia, oral Ulodesine (BCX4208) (5 mg/kg/day) for 7 days reduces sUA by 65% and urinary uric acid excretion by 40%, consistent with decreased de novo uric acid synthesis [2] 4. In phase I clinical trials, single oral doses of Ulodesine (BCX4208) (50–800 mg) in healthy volunteers reduce sUA by 30–60% in a dose-dependent manner, with the effect persisting for 24 hours at doses ≥200 mg [2]
Enzyme Assay	1. PNP enzyme activity assay (human/mouse/rat): Purified recombinant human, mouse, and rat PNP proteins were incubated with serial concentrations of Ulodesine (BCX4208) (0.1 nM–10 μM) in reaction buffer containing inosine (100 μM, PNP substrate) and phosphate buffer (50 mM). The mixture was incubated at 37°C for 30 minutes, and the reaction was terminated by adding trichloroacetic acid (10% v/v). The production of hypoxanthine (PNP reaction product) was quantified by HPLC with UV detection at 254 nm. Dose-response curves were generated to calculate Ki (for human PNP) and IC50 (for mouse/rat PNP) values [1] 2. Xanthine oxidase selectivity assay: Recombinant human XO protein was incubated with Ulodesine (BCX4208) (0.1 nM–10 μM) and xanthine (100 μM, XO substrate) in Tris-HCl buffer (pH 7.5). The formation of uric acid was measured by spectrophotometry at 293 nm. The percentage of XO inhibition was calculated to assess off-target activity [2]
Cell Assay	1. HepG2 cell uric acid production assay: Human HepG2 hepatoma cells were seeded in 24-well plates at a density of 5×10⁴ cells/well and cultured for 24 hours. Cells were pre-treated with Ulodesine (BCX4208) (0.1 nM–10 μM) for 1 hour, then stimulated with hypoxanthine (500 μM) for 6 hours to induce uric acid synthesis. Culture supernatants were collected, and uric acid concentrations were measured using a colorimetric assay kit. The inhibition rate of uric acid production was calculated relative to vehicle-treated controls [1] 2. PBMC purine metabolism assay: Human peripheral blood mononuclear cells (PBMCs) were isolated from healthy donor blood and cultured in RPMI medium. Cells were treated with Ulodesine (BCX4208) (0.5 nM–10 nM) for 4 hours, then incubated with [¹⁴C]inosine (1 μCi/mL) for 2 hours. Intracellular nucleosides and extracellular hypoxanthine were separated by HPLC and quantified by liquid scintillation counting to assess PNP-mediated catabolism [1]
Animal Protocol	1. Novel mouse hyperuricemia model establishment: Male C57BL/6 mice (20–25 g) were administered oxonic acid (250 mg/kg) via intraperitoneal (i.p.) injection 1 hour before oral gavage of hypoxanthine (500 mg/kg) to induce hyperuricemia. Ulodesine (BCX4208) was formulated in 0.5% CMC-Na + 0.1% Tween 80 and administered orally at doses of 1, 3, 10 mg/kg (gavage volume: 0.2 mL/20 g body weight) 30 minutes before hypoxanthine administration. Blood samples were collected from the orbital sinus at 0, 2, 4, 6, and 8 hours post-hypoxanthine to measure sUA by HPLC [1] 2. Rat diet-induced hyperuricemia protocol: Male Sprague-Dawley rats (200–250 g) were fed a high-purine diet (2% yeast extract) for 14 days to induce hyperuricemia. Ulodesine (BCX4208) (5 mg/kg/day) or vehicle was administered orally once daily for 7 days. Blood samples were collected from the tail vein every 2 days to measure sUA, and 24-hour urine was collected on day 7 to quantify urinary uric acid excretion [2] 3. Preclinical efficacy comparison protocol: Hyperuricemic mice were randomized to receive Ulodesine (BCX4208) (10 mg/kg p.o.), allopurinol (10 mg/kg p.o.), or vehicle. sUA levels were measured at 0, 2, 4, 6, and 8 hours post-dosing to compare the duration and magnitude of urate-lowering effects [1]
ADME/Pharmacokinetics	1. Mouse pharmacokinetics: After oral administration of Ulodesine (BCX4208) (10 mg/kg), the peak plasma concentration (Cmax) is 1.8 μg/mL (achieved at 1 hour), elimination half-life (t₁/₂) is 6.2 hours, and absolute oral bioavailability is ~85% [1] 2. Human phase I PK: In healthy volunteers, oral Ulodesine (BCX4208) (200 mg) results in a Cmax of 3.5 μg/mL, AUC₀–24h of 42 μg·h/mL, and t₁/₂ of 8.5 hours; plasma protein binding is ~78% (measured by ultrafiltration) [2] 3. Tissue distribution: In mice, Ulodesine (BCX4208) distributes widely to liver, kidney, and gastrointestinal tract (tissue/plasma ratio of 2.1–3.5), with low penetration into the central nervous system (brain/plasma ratio of 0.15) [1] 4. Metabolism and excretion: Ulodesine (BCX4208) is minimally metabolized in the liver (≤10% of dose as metabolites); ~70% of the oral dose is excreted unchanged in urine within 72 hours, and 20% is excreted in feces [2]
Toxicity/Toxicokinetics	1. In vitro cytotoxicity: Ulodesine (BCX4208) (up to 10 μM) shows no significant cytotoxicity in HepG2 cells, PBMCs, or primary renal tubular cells, with cell viability >90% as assessed by MTT assay [1] 2. Acute in vivo toxicity: Single oral administration of Ulodesine (BCX4208) (2000 mg/kg) in mice causes no mortality or behavioral abnormalities (e.g., lethargy, ataxia) over 7 days; gross necropsy reveals no organ damage [1] 3. Chronic toxicity: Rats treated with Ulodesine (BCX4208) (50 mg/kg/day) for 28 days show no changes in liver/renal function markers (ALT, AST, creatinine) or histopathological abnormalities in liver/kidney tissues [2] 4. Drug-drug interactions: Ulodesine (BCX4208) does not inhibit human CYP450 enzymes (CYP1A2, 2C9, 2C19, 2D6, 3A4) at therapeutic concentrations (up to 10 μM), and no pharmacokinetic interactions are observed with allopurinol or probenecid in preclinical studies [2]
References	[1]. Establishment of a novel hyperuricemiaanimal model using mice and assessment ofhyporuricemia action of PNP inhibitor Ulodesine. [2]. New medications in development for the treatment of hyperuricemia of gout. Curr Opin Rheumatol. 2015 Mar;27(2):164-9.
Additional Infomation	Ulodesine has been used in trials studying the treatment of Gout, Arthritis, Hyperuricemia, and Joint Disease. 1. Ulodesine (BCX4208) is a potent, selective, orally bioavailable purine nucleoside phosphorylase (PNP) inhibitor developed by BioCryst Pharmaceuticals for the treatment of hyperuricemia and gout [1][2] 2. Ulodesine (BCX4208) exerts its hypouricemic effect by inhibiting PNP, a key enzyme in the purine salvage pathway; this blocks the catabolism of inosine/guanosine to hypoxanthine/guanine, reducing the substrate pool for xanthine oxidase-mediated uric acid synthesis [1] 3. Unlike xanthine oxidase inhibitors (XOIs, e.g., allopurinol, febuxostat), Ulodesine (BCX4208) targets the purine salvage pathway rather than direct XO inhibition, providing a novel mechanism for uric acid lowering [2] 4. Ulodesine (BCX4208) completed phase II clinical trials for gout, demonstrating sustained urate-lowering efficacy in patients with hyperuricemia who had inadequate response to XOIs [2]

Solubility Data

Solubility (In Vitro)

DMSO:≥ 10mg/mL Water:N/A Ethanol:N/A

Solubility (In Vivo)

Solubility in Formulation 1: ≥ 1 mg/mL (3.78 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 10.0 mg/mL clear DMSO stock solution to 400 μL of PEG300 and mix evenly; then add 50 μL of Tween-80 to the above solution and mix evenly; then add 450 μL of 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. Solubility in Formulation 2: ≥ 1 mg/mL (3.78 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 10.0 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. Solubility in Formulation 3: ≥ 1 mg/mL (3.78 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 10.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	3.7839 mL	18.9193 mL	37.8387 mL
	5 mM	0.7568 mL	3.7839 mL	7.5677 mL
	10 mM	0.3784 mL	1.8919 mL	3.7839 mL

*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.