Seocalcitol

Seocalcitol (EB1089) Description:IC50: In SKHEP-1 cells, the IC50 for seocalcitol was 460.99 nM.
Calcitriol receptor, also known as the vitamin D receptor (VDR), is a member of the nuclear receptor family of transcription factors. The VDR not only regulates transcriptional responses but also involved in microRNA-directed post transcriptional mechanisms. Seocalcitol (EB1089) is a vitamin D analog that has been extensively studied and shown to have profoundly reduced hypercalcemic effects.
In vitro: In a previous in vitro study, it was found that proliferation of Hep 3B, PLC/PRF/5 and SKHEP-1 HCC cells was significantly inhibited at all seocalcitol concentrations tested, while HTC cells only responded to 1,000 nM concentration of EB1089. However, proliferation of Novikoff cells was unaffected by the drug at all concentrations examined [1]. Another cell in-vitro study indicated that EB1089 significantly inhibited HEp-2 cell proliferation and increased p57 mRNA and protein levels; this was blocked by siRNA-p57 but not by siRNA-con [2].
In vivo: Seocalcitol effectively inhibited SKHEP-1 tumor growth without inducing hypercalcemia (p<0.05). These results indicate that seocalcitol is an effective growth inhibitor of HCC tumors [1].
Clinical trial: 56 patients with inoperable advanced HCC were included in an uncontrolled study of oral Seocalcitol treatment for up to 1 year. Out of 33 patients evaluable for tumour response, two had complete response (CR), 12 stable disease and 19 progressive disease. The CRs appeared after 6 and 24 months of treatment, and lasted for 29 and at least 36 months. Seocalcitol was well tolerated; the most frequent toxicity was hypercalcaemia and related symptoms. Most patients tolerated a daily dose of 10 mg of Seocalcitol. These data showed that Seocalcitol may have an effect in the treatment of HCC, especially in early disease when a prolonged treatment can be instituted. The survival benefit with or without tumour response should be determined in controlled studies [3].
Reference:
[1] Ghous Z, Akhter J, Pourgholami MH, Morris DL. Inhibition of hepatocellular cancer by EB1089: in vitro and in vive study. Anticancer Res. 2008;28(6A):3757-61.
[2] Lu L, Qiu J, Liu S, Luo W. Vitamin D3 analogue EB1089 inhibits the proliferation of human laryngeal squamous carcinoma cells via p57. Mol Cancer Ther. 2008;7(5):1268-74.
[3] Dalhoff K1 Dancey J, Astrup L, Skovsgaard T, Hamberg KJ, Lofts FJ, Rosmorduc O, Erlinger S, Bach Hansen J, Steward WP, Skov T, Burcharth F, Evans TR. A phase II study of the vitamin D analogue Seocalcitol in patients with inoperable hepatocellular carcinoma. Br J Cancer. 2003 21;89(2):252-7.

Bioavailability of seocalcitol IV: evaluation of lymphatic transport in conscious rats.[Pubmed:17048118]

Pharm Res. 2006 Nov;23(11):2681-8.

PURPOSE: To study the use of long chain triglycerides (LCT) as a lymphotropic carrier of (3)H-Seocalcitol by comparing the lymphatic transport and the portal absorption of (3)H-Seocalcitol when dissolved in a (1) LCT solution or a (2) reference solution without lipid containing propylene glycol (PG). MATERIALS AND METHODS: A lymph cannulated conscious rat model was dosed orally with (3)H-Seocalcitol dissolved in either LCT or PG. Lymph was collected continuously, and blood was sampled over 9 h. (3)H-Seocalcitol in blood and lymph and triglycerides in lymph were analysed. RESULTS: A statistically significantly (p < 0.05) higher recovery of the dosed (3)H-Seocalcitol was found in the intestinal lymph upon administration of the LCT solution (1.3 +/- 0.6%) compared to the PG solution (0.5 +/- 0.4%). The portal absorption of (3)H-Seocalcitol was significantly (p < 0.05) higher from the LCT solution (16.2 +/- 2.2%) than from the PG solution (10.8 +/- 0.8%). CONCLUSIONS: The LCT solution resulted in a statistical significantly higher level of lymphatic and portal transport of (3)H-Seocalcitol compared with the PG solution. However, even though LCT facilitates the formation of chylomicrons, (3)H-Seocalcitol favours absorption directly to the portal blood probably due to the moderate lipophilicity of the molecule.

MNU-induced mammary gland carcinogenesis: chemopreventive and therapeutic effects of vitamin D and Seocalcitol on selected regulatory vitamin D receptor pathways.[Pubmed:21843606]

Toxicol Lett. 2011 Nov 10;207(1):60-72.

The effects of administration of vitamin D(3) and Seocalcitol on MNU-induced carcinogenesis of mammary gland in Sprague-Dawley rats have been investigated. Administration of both substances in a weekly dose of 7 mug/kg caused prolonged latency of mammary gland tumors. The latency of tumors was markedly prolonged for 30-40 days by Seocalcitol. Using PET analysis, reduction in [(1)(8)F]2-fluoro-2-deoxy-d-glucose (FDG) uptake or tumor volume in tumors chemopreventively treated with vitamin D(3) were detected in MNU-induced tumors, vitamin D(3) reduced expression of 25-hydroxylase (25OHase) (p<0.01) and 24-hydroxylase (24OHase) (p<0.01) and Seocalcitol 24OHase. Positive regulation of 25OHase mRNA level after the treatment with vitamin D(3) was observed in liver, while in kidney, vitamin D(3) and Seocalcitol induced expression of 24OHase was significant. Our observations indicate a cross talk between respective pathways of VDR, RARs/RXRs, TRs and ERs in carcinogenesis process.

Bioavailability of seocalcitol III. Administration of lipid-based formulations to minipigs in the fasted and fed state.[Pubmed:17383165]

Eur J Pharm Sci. 2007 May;31(1):8-15.

The bioavailability of Seocalcitol from two lipid-based formulations and a propylene glycol (PG) solution was studied in minipigs in the fasted and fed state. The lipid-based formulations were a medium chain triglyceride (MCT) solution and a self-microemulsifying drug delivery system (MC-SMEDDS) having a composition of 25% MCT, 48% cremophor RH 40, 27% akoline MCM. An IV solution was administered in order to determine the absolute bioavailability. In the fasted state the absolute bioavailability of Seocalcitol was 15, 21 and 28% for the PG, MCT and MC-SMEDDS, respectively. The bioavailability from the PG solution was affected by the presence of food (29%), whereas the bioavailability from the lipid-based formulations was less affected by the presence of food; MCT (22%) and MC-SMEDDS (33%). The increased bioavailability from the PG solution in the fed state is believed to be due to the presence of lipids in the food. The present study illustrates an often mentioned beneficial effect of dosing lipid-based formulations; the reduced food effect on bioavailability. Previously published solubility data in simulated intestinal media relates very well to the present in vivo findings as the solubility studies showed that addition of lipids to the formulation could reduce/eliminate the difference in solubility between the fasted and fed state. Previously the same formulations were dosed to rats, resulting in a lower bioavailability from the MC-SMEDDS compared to the MCT. This illustrates that the animal model used should be carefully considered when studying formulations that are dependent on the dynamic processes in the GIT.

Antioxidants and doxorubicin supplementation to modulate CD14 expression and oxidative stress induced by vitamin D3 and seocalcitol in HL60 cells.[Pubmed:17982638]

Oncol Rep. 2007 Dec;18(6):1513-9.

1alpha,25-dihydroxyvitamin D3 (VD3) and the EB1089 analog are well known for their roles in the modulation of proliferation and the differentiation of several malignant cells. In addition, VD3 or EB1089 displayed a high disposal of oxidant features and the ability to cause release of reactive oxygen species (ROS). We attempted to enhance HL60 cell differentiation and to limit ROS generation, by the association of deltanoids with doxorubicin and the antioxidants catalase (CAT), superoxide dismutase (SOD) and N-acetyl cystein (NAC). Differentiation of HL60 cells into monocytic lineage was studied by expression of mRNA, protein CD14 and functional differentiation by the nitroblue tetrazolium assay. The 2',7'-dichlorodihydrofluorescein diacetate (H2-DCFDA) dye allowed to evaluate in situ ROS generation. When associated with 0.1 nM EB1089, 15 nM doxorubicin induced an increase of differentiated cell percentage from 29% to 87% and did not affect VD3-treated cells. The association with doxorubicin also induced a significant increase of ROS release (p<0.05) versus VD3 and EB1089-treated cells. These results correspond to additivity of individual effects of doxorubicin and deltanoids. Antioxidant agents (10 nM NAC, 50 U/ml SOD or 2000 U/ml CAT) were associated with 10 nM VD3 or 1 nM EB1089 for 72 h. Compared to VD3 and EB1089 treatments, associations with antioxidants induced a slight increase of differentiated cells and a significant increase of CD14 mRNA. The highest differentiation effect occurred in the case of the EB1089-NAC association. Antioxidants induced a decrease (p<0.05) in ROS release generated by VD3 or EB1089 near the level of untreated cells. Thus, antioxidant agents demonstrated a protective effect against VD3 and EB1089 oxidative cytotoxicity and an enhancement of the monocyte differentiation. Combinations of antioxidants with deltanoids could dissociate the oxidative stress and differentiation.

EB1089 inhibits the parathyroid hormone-related protein-enhanced bone metastasis and xenograft growth of human prostate cancer cells.[Pubmed:19584236]

Mol Cancer Ther. 2009 Jul;8(7):1787-98.

Parathyroid hormone-related protein (PTHrP) plays a major role in prostate carcinoma progression and bone metastasis. Once prostate cancers become androgen-independent, treatment options become limited. Vitamin D analogues represent a potentially valuable class of agents in this clinical context. Using the prostate cancer cell line C4-2 as a model, we studied the effects of PTHrP and the noncalcemic vitamin D analogue EB1089 on markers of prostate cancer cell progression in vitro and in vivo. C4-2 is a second-generation androgen-independent LNCaP subline that metastasizes to the lymph nodes and bone when injected into nude mice and produces mixed lytic/blastic lesions, mimicking the in vivo situation. We report that PTHrP increases cell migration and invasion, and that a pathway via which EB1089 inhibits these processes is through down-regulation of PTHrP expression. PTHrP also increases anchorage-independent cell growth in vitro and xenograft growth in vivo; EB1089 reverses these effects. The in vivo PTHrP effects are accompanied by increased tumor cell proliferation and survival. Treatment with EB1089 reverses the proliferative but not the antiapoptotic effects of PTHrP. PTHrP also increases intratumor vessel density and vascular endothelial growth factor expression; EB1089 reverses these effects. Intracardially injected C4-2 cells produce predominantly osteoblastic lesions; PTHrP overexpression decreases the latency, increases the severity and alters the bone lesion profile to predominantly osteolytic. EB1089 largely reverses these PTHrP effects. A direct correlation between PTHrP immunoreactivity and increasing tumor grade is observed in human prostate cancer specimens. Thus, decreasing PTHrP production by treatment with vitamin D analogues may prove therapeutically beneficial for prostate cancer.

Vitamin D3 analogue EB1089 inhibits the proliferation of human laryngeal squamous carcinoma cells via p57.[Pubmed:18483314]

Mol Cancer Ther. 2008 May;7(5):1268-74.

The objective of this study is to evaluate the role of the cyclin-dependent kinase inhibitor p57 in EB1089-inhibited proliferation of human laryngeal squamous carcinoma cells (HEp-2). HEp-2 cells were treated with the vitamin D3 analogue EB1089 for 48 h and total RNA was extracted for reverse transcription-PCR amplification using primers for the p57 coding sequence. Proteins were detected by Western blot analysis. For interference using silencing RNA (siRNA), HEp-2 cells were transfected with siRNA specific for p57 (siRNA-p57) or a negative control sequence (siRNA-con) followed by treatment with 10 nmol/L EB1089. The effects of EB1089 on cell proliferation were evaluated by 5-bromo-2'-deoxyuridine incorporation and '3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide assay. Cell death and cell cycle dynamics were monitored using flow cytometry. EB1089 significantly inhibited HEp-2 cell proliferation and increased p57 mRNA and protein levels; this was blocked by siRNA-p57 but not by siRNA-con. The EB1089-induced suppression of HEp-2 cell proliferation recovered to near-normal levels with siRNA-p57 transfection. EB1089 inhibits the proliferation of HEp-2 cells and p57 plays an important role in this.