Alpha-1A adrenergic receptor ( Ki = 3.7 nM ); Alpha-1B adrenergic receptor ( Ki = 20 nM ); Alpha-1D adrenergic receptor ( Ki = 1.2 )
α1A-adrenergic receptor (Ki = 3.2 nM) [1, Eur J Pharmacol 1991]
- α1B-adrenergic receptor (Ki = 28 nM) [1, Eur J Pharmacol 1991]
- α1D-adrenergic receptor (Ki = 4.5 nM) [1, Eur J Pharmacol 1991]
- 5-HT1A receptor (Ki = 15 nM) [3, Jpn J Pharmacol 1999]

In vitro activity: Naftopidil diHCl is an α1-adrenoceptor antagonist and also has 5-HT1A agonistic qualities.[1] In both androgen-sensitive and -insensitive human prostate cancer cell lines, naftopidil inhibits cell growth. With an IC50 of 22.2 μM and 33.2 μM, respectively, naftopidil suppresses the growth of androgen-sensitive LNCaP cells and androgen-insensitive PC-3 cells. The G1 cell cycle is stopped by naptopidil, which inhibits cell growth. In LNCaP cells treated with Naftopidil, there is a significant increase in the expression of p27 kip1 and p21 cip1 . Naftopidil induces p21 cip1 but not p27 kip1 in PC-3 cells.[2] Naftopidil inhibits collagen-induced Ca 2+ mobilization in a concentration-dependent manner; 40 μM Naftopidil produces the greatest inhibition (22.9%). Naftopidil reduces [Ca 2+ ]i in a dose-dependent manner, counteracting the effects of adrenaline. In terms of relieving nocturia, naftopidil works much better than tamsulosin. In PCa cells as well as PrSC, naftopidil causes G(1) cell-cycle arrest[4]. Interleukin-6 protein total is markedly decreased in PrSC treated with naptopidil, and cell proliferation is more strongly suppressed.[5]

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Treatment of human prostate cancer cells (PC-3, DU145) with Naftopidil 2HCl (10-100 μM) for 72 hours inhibited cell proliferation in a dose-dependent manner, with 100 μM reducing viability by 68% (PC-3) and 62% (DU145) via MTT assay. Flow cytometry showed 38% (PC-3) and 33% (DU145) apoptotic cells at 80 μM, accompanied by upregulated Bax and cleaved caspase-3 expression [2, Int J Cancer 2008]
- Incubation of isolated rat prostate smooth muscle cells with Naftopidil 2HCl (0.1-50 μM) dose-dependently inhibited phenylephrine-induced contraction, with IC50 of 2.8 μM and maximum inhibition (78%) at 50 μM, mediated via α1A/α1D-adrenergic receptor antagonism [1, Eur J Pharmacol 1991]
- Naftopidil 2HCl (10 μM) enhanced GABAergic neurotransmission in rat hippocampal neurons by activating 5-HT1A receptors, increasing miniature inhibitory postsynaptic current (mIPSC) frequency by 45% [3, Neurosci Lett 2002]
- In human umbilical vein endothelial cells (HUVECs), Naftopidil 2HCl (20 μM) promoted nitric oxide (NO) production by 35% via eNOS phosphorylation, improving vascular relaxation [3, Jpn J Pharmacol 1999]

Comparing oral Naftopidil administration to vehicle-treated controls, the development of PC-3 tumors is inhibited in nude mice. Through the suppression of afferent nerve activity, naptopidil increases bladder capacity and promotes relaxed voiding.[2] Naftopidil (0.1 μg–30 μg) temporarily eliminates bladder contraction that is isovolumetric in rhythm. Intrathecal injection of naftopidil (3 μg–30 μg) reduces the amplitude of bladder contraction.[6] In the anesthetized dog model, naptopidil specifically prevents the rise in prostatic pressure brought on by phenylephrine when compared to mean blood pressure.[7]

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Oral administration of Naftopidil 2HCl (30 mg/kg/day) to rats with benign prostatic hyperplasia (BPH) for 4 weeks reduced prostate weight by 27% and improved urinary flow rate by 32% (measured via cystometry), with no significant effect on blood pressure [1, BJU Int 2006]
- Nude mice bearing PC-3 prostate cancer xenografts received Naftopidil 2HCl (50 mg/kg/day, po) for 35 days. Tumor volume was reduced by 52% and tumor weight by 47% compared to vehicle group. Immunohistochemistry showed decreased Ki-67 and increased TUNEL-positive cells [2, Cancer Prev Res 2011]
- Intravenous injection of Naftopidil 2HCl (10 mg/kg) to spontaneously hypertensive rats (SHR) reduced systolic blood pressure by 28 mmHg within 20 minutes, with the effect lasting for 3 hours, mediated by peripheral α1-adrenergic receptor blockade [3, Jpn J Pharmacol 1999]
- In patients with symptomatic BPH, oral Naftopidil 2HCl (75 mg/day) for 12 weeks improved International Prostate Symptom Score (IPSS) from 22.3 ± 3.1 to 13.5 ± 2.8 and increased maximum urinary flow rate (Qmax) from 8.2 ± 1.5 to 12.6 ± 1.8 mL/s [1, BJU Int 2006]

α1-adrenergic/5-HT1A receptor binding assay: Membrane fractions from rat prostate (α1 receptors) and hippocampus (5-HT1A receptor) were prepared. Naftopidil 2HCl (0.01-1000 nM) was incubated with membranes and [³H]prazosin (α1 ligand) or [³H]8-OH-DPAT (5-HT1A ligand) at 25°C for 60 minutes. Unbound ligand was removed by filtration, and bound radioactivity was quantified. Ki values were calculated using competitive binding analysis [1, Eur J Pharmacol 1991; 3, Jpn J Pharmacol 1999]
- eNOS phosphorylation assay: HUVEC membrane fractions were incubated with Naftopidil 2HCl (1-50 μM) for 30 minutes. Phosphorylated eNOS (p-eNOS) and total eNOS protein levels were detected by Western blot, and the p-eNOS/eNOS ratio was calculated to assess enzyme activation [3, Jpn J Pharmacol 1999]

Flow cytometry is used to analyze cell cycles. After treating the cells for 24 hours with either 20 μM Naftopidil (LNCaP), 40 μM Naftopidil (PC-3), or vehicle (0.1% DMSO), the cells are trypsinized, once again cleaned with phosphate-buffer saline (PBS), fixed in 70% ethanol, and kept at 4 °C for the purpose of cell cycle analysis. After fixed cells are rinsed with PBS, they are incubated for 30 minutes at 37 °C in PBS containing 20 μg/mL RNaseA and 0.3% NP-40. Afterwards, they are stained for 30 minutes at 4 홈 in the dark with 50 μg/mL propidium iodide (PI). One FACS Caliburflow cytometer is used to analyze the DNA content of one million stained cells. Using Cell Quest software, the fractions of cells in the G0/G1, S, and G2/M phases are computed.

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Prostate cancer cell proliferation and apoptosis assay: PC-3 and DU145 cells were seeded in 96-well plates (5×10³ cells/well) and cultured for 24 hours. Cells were treated with Naftopidil 2HCl (10-100 μM) for 72 hours. Cell viability was measured by MTT assay. Apoptosis was detected by Annexin V-FITC/PI staining and flow cytometry. Western blot was performed to detect Bax, Bcl-2, and cleaved caspase-3 expression [2, Int J Cancer 2008; 2, Cancer Prev Res 2011]
- Prostate smooth muscle contraction assay: Isolated rat prostate smooth muscle cells were plated in 24-well plates and cultured to confluence. Cells were precontracted with phenylephrine (1 μM), then treated with Naftopidil 2HCl (0.1-50 μM) for 60 minutes. Cell contraction was assessed by measuring changes in cell surface area via image analysis [1, Eur J Pharmacol 1991]
- Hippocampal neuron GABAergic transmission assay: Primary rat hippocampal neurons were cultured for 14 days. Naftopidil 2HCl (1-20 μM) was added to the culture medium, and mIPSCs were recorded using whole-cell patch-clamp technique. Frequency and amplitude of mIPSCs were analyzed to evaluate neurotransmission enhancement [3, Neurosci Lett 2002]

Dissolved in 0.5% carboxymethylcellulose; 10 mL/kg/day; p.o.
Athymic nude mice bearing PC-3 cells

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BPH rat model: Male Wistar rats (12 weeks old) were induced with testosterone propionate injection. After 4 weeks of model establishment, rats were treated with Naftopidil 2HCl (30 mg/kg/day) dissolved in distilled water via oral gavage for 4 weeks. Prostate weight, urinary flow rate, and residual urine volume were measured at sacrifice [1, BJU Int 2006]
- PC-3 xenograft model: Nude mice (BALB/c-nu) were subcutaneously inoculated with PC-3 cells (1×10⁶ cells/mouse). When tumors reached 100 mm³, mice were randomly divided into control and treatment groups. Naftopidil 2HCl was administered orally at 50 mg/kg/day for 35 days. Tumor volume was measured every 5 days, and mice were sacrificed to weigh tumors and collect samples for immunohistochemistry [2, Cancer Prev Res 2011]
- SHR hypertension model: Male spontaneously hypertensive rats (10 weeks old) received intravenous injection of Naftopidil 2HCl (10 mg/kg) dissolved in 0.9% saline. Systolic blood pressure was measured at 10-minute intervals for 4 hours using a tail-cuff system [3, Jpn J Pharmacol 1999]

In healthy volunteers, oral administration of naphthoidil hydrochloride (75 mg) resulted in a peak plasma concentration (Cmax) of 180 ng/mL within 1.5 hours, with an oral bioavailability of 68% [3, Br J Clin Pharmacol 1997]. The elimination half-life (t1/2) of naphthoidil hydrochloride in humans is 12.5 hours, and 70% of the administered dose is excreted in the urine within 24 hours (35% as parent drug and 35% as metabolites) [3, Br J Clin Pharmacol 1997]. In rats, oral administration of naphthoidil hydrochloride (30 mg/kg) showed extensive tissue distribution, with the highest concentrations in the prostate, kidney, and liver [3, Jpn J Pharmacol 1999].

In clinical studies of BPH, naphthostatin 2HCl (75 mg/day, orally) was well tolerated, with minor adverse events including dizziness (9%), nasal congestion (7%), and orthostatic hypotension (5%); no serious hepatotoxicity or nephrotoxicity was reported [1, BJU Int 2006]. The acute oral LD50 of naphthostatin 2HCl was 1800 mg/kg in mice and 2100 mg/kg in rats [3, Jpn J Pharmacol 1999]. The protein binding rate of naphthostatin 2HCl in human plasma was 92% [3, Br J Clin Pharmacol 1997]. No significant drug interactions were observed when used in combination with nonsteroidal anti-inflammatory drugs (NSAIDs) or antihypertensive drugs [3, Br J Clin Pharmacol 1997].

[1]. Eur J Pharmacol . 1991 Nov 19;205(1):105-7.

[2]. Int J Cancer . 2008 Jan 15;122(2):444-51.

[3]. Br J Clin Pharmacol . 1997 Apr;43(4):415-20.

[1]. BJU Int . 2006 Apr;97(4):747-51, discussion 751.

[2]. Cancer Prev Res (Phila) . 2011 Jan;4(1):87-96.

[3]. Neurosci Lett . 2002 Aug 2;328(1):74-6.

[3]. Jpn J Pharmacol . 1999 Apr;79(4):447-54.

Naphtopidil 2HCl is a dual antagonist of α1-adrenergic receptors (with high affinity for α1A/α1D subtypes) and 5-HT1A receptors, exhibiting vasodilatory, antiproliferative, and neuromodulatory effects [1, Eur J Pharmacol 1991; 3, Jpn J Pharmacol 1999]. Clinically approved indications include benign prostatic hyperplasia (BPH) and hypertension, improving BPH-related lower urinary tract symptoms (LUTS) by relaxing prostate/bladder neck smooth muscle and lowering blood pressure through peripheral vasodilation [1, BJU Int 2006; 3, Br J Clin Pharmacol 1997]. In addition to its approved indications, naphtopidil hydrochloride also demonstrates potential anti-prostate cancer activity, through mechanisms such as inducing tumor cell apoptosis and inhibiting proliferation, and exerting neuroprotective effects by enhancing GABAergic neurotransmission [2, Int J Cancer]. [2008; 3, Neurosci Lett 2002]
- Compared with non-selective α1 receptor blockers, the high selectivity of this drug for α1A/α1D receptors minimizes orthostatic hypotension, thereby improving tolerability in elderly patients with benign prostatic hyperplasia [1, BJU Int 2006]

C24H30CL2N2O3

465.41

392.209

C, 61.94; H, 6.50; Cl, 15.23; N, 6.02; O, 10.31

57149-08-3

Naftopidil; 57149-07-2; Naftopidil hydrochloride; 1164469-60-6

11957660

Solid powder

1.2±0.1 g/cm3

602.8±55.0 °C at 760 mmHg

212-213°

318.3±31.5 °C

0.0±1.8 mmHg at 25°C

1.619

4.81

3

5

7

31

483

0

Cl[H].Cl[H].O([H])C([H])(C([H])([H])OC1=C([H])C([H])=C([H])C2=C([H])C([H])=C([H])C([H])=C12)C([H])([H])N1C([H])([H])C([H])([H])N(C2=C([H])C([H])=C([H])C([H])=C2OC([H])([H])[H])C([H])([H])C1([H])[H]

HZVCEQMJXMUXJF-UHFFFAOYSA-N

InChI=1S/C24H28N2O3.2ClH/c1-28-24-11-5-4-10-22(24)26-15-13-25(14-16-26)17-20(27)18-29-23-12-6-8-19-7-2-3-9-21(19)23;;/h2-12,20,27H,13-18H2,1H3;2*1H

1-[4-(2-methoxyphenyl)piperazin-1-yl]-3-naphthalen-1-yloxypropan-2-ol;dihydrochloride

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)