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MedKoo product information:
PX-478
Description of PX-478: PX-478 is HIF-1alpha inhibitor, is also an orally active small molecule with potential antineoplastic activity. Although its mechanism of action has yet to be fully elucidated, HIF1-alpha inhibitor PX-478 appears to inhibit hypoxia-inducible factor 1-alpha (HIF1A) expression, which may result in decreased expression of HIF1A downstream target genes important to tumor growth and survival, a reduction in tumor cell proliferation, and the induction of tumor cell apoptosis. The inhibitory effect of this agent is independent of the tumor suppressor genes VHL and p53 and may be related to derangements in glucose uptake and metabolism due to inhibition of glucose transporter-1 (Glut-1). PX-478 has excellent activity against established human tumor xenografts, providing tumor regressions with prolonged growth delays which correlate positively with HIF-1 levels. PX-478 is a highly water soluble molecule, with good i.v., i.p. and p.o. antitumor activity. It is rapidly absorbed following oral and i.p. administration and gives excellent Cmax and AUC via these routes. Check for active clinical trials or closed clinical trials using this agent. (NCI Thesaurus).
Current developer: Oncothyreon.
Stability of PX-478: According to researchers from ProlX Pharmaceuticals, chemical stability of PX-478 under variable temperature and light conditions showed 100% recovery for greater than 6 months. PX-478, as either an amorphous or crystalline hydrochloride salt is highly water soluble. Examination of pH stability provided evidence of base lability, however excellent stability in solutions of pH<3 with t1/2 of 26 to 2643 days at 4°C. Neutral, isotonic buffered dosing solution had sufficient stability to allow i.v. administration for the toxicology and kinetics studies in mice, rats, and dogs where the maximum tolerable dose for five day i.v. treatment was found to be 100, 35 and 20mg/kg, respectively. (source: http://aacrmeetingabstracts.org/cgi/content/abstract/2004/1/486-b).
Activity observed in animal model study: PX-478 has been shown to have efficacy against a number of human cancer xenograft models, with significant regressions and growth delays in OvCar-3 (ovarian), SHP-77 (small cell lung), PC-3 (prostate), DU-145 (prostate), MCF-7 (breast), and Caki-1 (renal). PX-478 suppresses constitutive and hypoxia induced levels of HIF-1a in cancer cells, while leaving other ubiquitin regulated proteins unaffected. Through HIF-1a inhibition , PX-478 inhibits the expression of VEGF and the glucose transporter Glut-1, resulting in massive tumour apoptosis When tumours (xenograft models in mice) are being treated with PX-478, the efficiency of tumour killing correlates with inherent tumour HIF-1a expression. (source: http://pharmalicensing.com).
Toxicity of PX-478: The primary toxicological indicators were myelosuppression and rapidly reversible weight loss that correlated with food intake. The bioanalytic protocol and assay developed for identification of PX-478 and metabolites in biological samples demonstrated excellent frozen and refrigerated stability of PX-478 once isolated. Oral and i.p. administration of PX-478 to mice show excellent bioavailability of 86% and 91%, respectively. The terminal half life values for parent drug were determined in mice and dogs to be 60 minutes and 8 minutes, respectively. Clearance and volume of distribution in mice and dogs were found to be 4.7 and 15.6 ml/min/kg and 380 and 184 ml/kg, respectively. Protein binding studies of PX-478 in mice showed no measurable binding. (source: http://aacrmeetingabstracts.org/cgi/content/abstract/2004/1/486-b).
Mechanism of P-478: PX-478 is the N-oxide form of the approved anticancer drug melphalan, PX-478 was reported to suppress HIF-1α levels in human tumor xenografts and inhibit the expression of HIF-1 target genes including vascular endothelial growth factor (VEGF) and the glucose transporter-1. PX-478 had marked antitumor activity against even large tumor xenografts, which correlated positively with HIF-1α levels. Even though the upstream targets have not been fully elucidated, PX-478 inhibited HIF-1α at multiple levels that together or individually might contribute to its antitumor activity against HIF-1α-expressing tumors. It was reported that PX-478 inhibited HIF- 1α protein levels and HIF-1 transactivating activity in a variety of cancer cell lines. The inhibition occurred in both normoxic and hypoxic conditions and did not require pVHL or p53.
Three mechanisms were identified as contributing to the decrease in HIF-1α levels by PX-478: reduction in HIF-1α mRNA levels, and inhibition of HIF-1α translation play major roles; inhibition of HIF-1α deubiquitination, appears to play a minor role. HIF-1α was up-regulated in irradiated tumors and thus might serve as a promising target for radiosensitization. PX-478 reduced HIF-1α protein levels and signaling in vitro in a dose-dependent manner and provided direct radiosensitization of hypoxic cancer cells in clonogenic survival assays using C6 glioma, HN5 and UMSCCa10 squamous cells, and Panc-1 pancreatic adenocarcinoma cell lines. Of note, PX-478 yielded striking in vivo tumor sensitization to a single-dose irradiation, prevented postradiation HIF-1 signaling, and abrogated downstream stromal adaptation in C6 and HN5 reporter xenografts. (source: Lee K, Kim HM. A novel approach to cancer therapy using PX-478 as a HIF-1α inhibitor. Arch Pharm Res. 2011 Oct;34(10):1583-5.)
Phase I trials of P-478: A Phase I trial was done at two sites in the US and the result was reported at the 2010 ASCO Annual Meeting. The Phase I trial of PX-478 was an open-label, dose escalation trial in 41 patients with advanced cancer that was designed to examine safety, tolerability, pharmacokinetics, pharmacodynamics and antitumor activity. PX-478 was administered orally on days 1-5 of a 21 day cycle at doses ranging from 1 mg/ m2 to 88.2 mg/m2. Adverse events occurring in more than 10 percent of patients were nausea, fatigue, diarrhea and vomiting. One patient experienced prolonged Grade 3 thrombocytopenia at the highest dose level. Thirteen of 37 evaluable patients (35%) had stable disease. Pharmacodynamic studies revealed dose-proportional inhibition of HIF-1α levels. Pharmacokinetic studies demonstrated low levels of PX-478 with evidence for conversion to melphalan and other metabolites. The result was promising in that clinical treatment with PX-478 was associated with a relatively high proportion of patients achieving stable disease and a dose-dependent inhibition of HIF-1α. Metabolite identification and related metabolism studies might be done to identify metabolic pathways and active entities from PX-478 besides inactive melphalan. Conclusively, HIF-1α was proven to be a valid target of cancer therapy and modulates multiple tumorigenic processes. The information from preclinical and clinical trials of PX-478 will be useful for developing a novel approach to cancer therapy with HIF-1α inhibitors and give positive impacts to following developments and appilications of HIF inhibitors. (source: Lee K, Kim HM. A novel approach to cancer therapy using PX-478 as a HIF-1α inhibitor. Arch Pharm Res. 2011 Oct;34(10):1583-5.)
1: Sun K, Halberg N, Khan M, Magalang UJ, Scherer PE.
Selective Inhibition of HIF1α Ameliorates Adipose Tissue Dysfunction.
Mol Cell Biol. 2012 Dec 17. [Epub ahead of print] PubMed PMID: 23249949.
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