Nucleus: The Chemical Blogspace Blog

Cabazitaxel (see structure), is an orally bioavailable semi-synthetic derivative of the natural taxoid 10-deacetylbaccatin III with potential antineoplastic activity. Cabazitaxel binds to and stabilizes tubulin, resulting in the inhibition of microtubule depolymerization and cell division, cell cycle arrest in the G2/M phase, and the inhibition of tumor cell proliferation. Unlike other taxane compounds, this agent is a poor substrate for the membrane-associated, multidrug resistance (MDR), P-glycoprotein (P-gp) efflux pump and may be useful for treating multidrug-resistant tumors. In addition, cabazitaxel penetrates the blood-brain barrier (BBB).

Sanofi-aventis recently announced results from a Phase 3 trial which demonstrated cabazitaxel plus prednisone/prednisolone significantly improved overall survival and progression-free survival in patients with metastatic (advanced) hormone-refractory prostate cancer whose disease progressed following treatment with docetaxel-based chemotherapy. 

TROPIC (trial) was designed to assess patients with metastatic hormone-refractory prostate cancer whose disease had progressed following treatment with docetaxel-based chemotherapy. Results showed that the combination of cabazitaxel and prednisone/prednisolone significantly reduced the risk of death by 30%.

Researchers are  happy with these compelling results  and  hope that these results will provide new options and hope for patients with serious diseases, such as metastatic hormone-refractory prostate cancer.….

Ref : http://en.sanofi-aventis.com/binaries/20100304_Asco_GU_en_tcm28-27547.pdf

Rhubarb (herbaceous perennial plants growing from short, thick rhizomes) is a group of plants that belong to the genus Rheum in the family Polygonaceae.  They have large leaves that are somewhat triangular shaped with long fleshy petioles and small flowers. While the leaves are toxic, the plants have medicinal uses, but most commonly the plant’s stalks (see picture, source : Wikipedia) are cooked and used in pies and other foods for their tart flavour.  A number of varieties have been domesticated for human consumption, most of which are recognised as Rheum x hybridum by the Royal Horticultural Society.

Rhubarb (stem & roots) has been used as a strong laxative (the two  – anthraquinones emodin and rhein are responsible). Rubarb has been used in traditional Chinese medicine & medieval Arabic and European prescriptions. The rhizomes (‘roots’) contain stilbene compounds (including rhaponticin) which seem to lower blood glucose levels in diabetic mice.

Now,  researchers from Biomedical Research Center at Sheffield Hallam University, lead by Dr. Nikki Jordan-Mahy, have come up with new findings. Researchers found that baking British garden rhubarb for 20 minutes dramatically boosted levels of anti-cancer chemicals called polyphenols. Previous research has shown that polyphenols selectively kill or prevent the growth of cancer cells.

This is the first study to examine the benefits of British rhubarb, specifically a variety grown in South Yorkshire. Earlier research has studied Oriental medicinal rhubarb, which has been used in traditional Chinese medicine for thousands of years. 

Baking and slow stewing offered the best maintenance of colour through preservation of anthocyanin and the highest antioxidant capacity. Baking for 20 min provided well-cooked rhubarb with the highest antioxidant capacity and the highest anthocyanin content, which is important for the aesthetic quality of the dish.  

As per the claim by the researchers, LC–MS analysis putatively identified over 40 polyphenol components in raw rhubarb (including anthraquinone, stilbene, anthocyanin and flavonol derivatives.) Baking caused selective effects on the stability of the different polyphenol components. Initially, the yield of all components increased but there was a drastic decline in the relative stability of anthraquinone aglycones with increasing cooking time and initial evidence for the turnover of other anthraquinone derivatives was obtained. Researchers now plan to study the effect of rhubarb’s polyphenols on leukemia…..

Ref : Dr. Nikki Jordan-Mahy, et. al., Food Chemistry, Vol. 119, Issue 2, 15 March 2010, Pages 758-764

Using human breast cancer cells and primary human mammary epithelial cells in vitro, Dr. Ratna  Ray (Professor in the Department of Pathology at Saint Louis University) and colleagues found the bitter melon extract significantly decreased proliferation, of cell growth and division, and induced death in breast cancer cells. These early results offer an encouraging path for research into breast cancer. Researchers claim that, “this study may provide us with one more agent as an extract that could be used against breast cancer if additional studies hold true“. 

Ray and colleagues are currently conducting follow-up studies using a number of cancer cell lines to examine the anti proliferative effect of the extract. They are also planning a preclinical trial to evaluate its chemopreventive efficacy by oral administration. Hope they come up with positive results…….

Ref : Dr. Ratna Ray et.al., Cancer Research, 10.1158/0008-5472, February 23, 2010.

Van Andel Research Institute (VARI) researchers have found a way to reverse resistance to Sunitinib (see structure), a treatment that is currently the first line of defense against clear cell renal cell carcinoma (ccRCC), a deadly form of kidney cancer. Most patients who show a positive response to Sunitinib develop a resistance to the drug after one year of treatment.

Researchers lead by Dr. Teh, Bin Tean found that ccRCC tumor cells that had developed a resistance to Sunitinib had increased secretion of the protein interleukin-8 (IL-8). Administering Sunitinib and IL-8 neutralizing antibodies re-sensitized tumors to sunitinib treatment. Researchers also found that IL-8 may serve as a useful biomarker to predict patients’ response to sunitinib treatment.

Interestingly,  another  study from same  group  of  Teh’s laboratory, looked into exactly how sunitinib works.  The study found that the treatment does not target tumor cells, but rather the tumor’s blood supply.

Researchers conclude that “it is now of critical importance to validate these findings in the clinical setting” and they hope that these insights will help to build upon recent advances to extend clinical benefits to more patients with metastatic kidney cancer….

Ref : 1.  Cancer Research 70, 1053, February 1, 2010. 

        2.  Cancer Research 70, 1063, February 1, 2010

We know that,  Abiraterone (discovered and developed at the Institute of Cancer Research in London, see structure) is a drug under investigation for use in hormone-refractory prostate cancer (prostate cancer not responding to treatment with antiandrogens). Abiraterone acts  by blocking the formation of testosterone by inhibiting CYP17A1 (CYP450c17), an enzyme also known as 17α-hydroxylase/17,20 lyase.  This enzyme is involved in the formation of DHEA and androstenedione, which may ultimately be metabolized into testosterone.

The latest trial, which was led by the ICR and the Royal Marsden NHS Foundation Trust, is the first to investigate the drug in men with such advanced prostate cancer.

A total of 47 men were recruited for the trial, all of whom had late-stage castration-resistant prostate cancer, which means that their disease was advanced and their tumors were no longer responsive to androgen deprivation therapy. In almost all cases, the men’s cancer had spread to their bones. All of the participants had already received hormone therapy and the chemotherapy drug docetaxel, but were no longer responding to those treatments. By the end of the study period, researchers found that around three-quarters of men had experienced a drop in levels of prostate specific antigen (PSA), which is often raised in men with prostate cancer and can be used to measure disease activity.

 In around half of the men,  PSA levels fell by at least 50 per cent, while three-quarters of participants also had a drop in the number of tumor cells circulating in their blood. Three years after the start of the trial, five of the patients were still taking abiraterone and benefitting from the treatment. Lead researcher Dr Alison Reid, also from the ICR and the Royal Marsden, noted that “abiraterone shrank or stabilised men’s cancers for an average of almost six months, which is a very impressive result with only mild side-effects“. 

Though the initial results are exciting, the researchers conclude that there’s a lot more work needed to establish what abiraterone’s place will be in treating men with prostate cancer….

Ref :http://info.cancerresearchuk.org/news/archive/cancernews/2010-02-16-New-drug-shows-promise-for-advanced-prostate-cancer-patients

The phase I study found that the chemotherapy medicine  Triapine, was well tolerated in combination with standard-of-care cisplatin chemotherapy and radiation treatment in women with cervical cancer. This regimen provided both significant reduction in cancer disease and cancer control.

In the study   (ten-patient study) patients,  were treated three times weekly with Triapine (a potent Ribonucleotide Reductase Inhibitor) in combination with weekly cisplatin treatment and daily pelvic radiation therapy over five weeks.  The researchers claims that  “a 100% complete response rate was observed and no disease progression was documented through 18 months of median follow-up.”A phase two follow-up study is ongoing at the Ireland Cancer Center. UH Case Medical Center  Hope this new found combintaton will be  a promising new treatment to help women fight this aggressive disease in the days to come…

Ref : http://clincancerres.aacrjournals.org/content/16/4/1298.abstract?sid=f3df7c2d-9e46-4baf-b47b-83d310b87641

The kinamycins are a series of naturally occurring compounds endowed with intriguing molecular architectures and potent biological properties such as  antibiotic and antitumor activities. These novel diazofluorene-containing compounds defied chemical synthesis since their initial disclosure by Omura et al. in 1970 until the first total synthesis of kinamycin C by Porco et al. in late 2006.

Now, researchers from Yale University,  have  developed a new method to recreate this structure that allows them to synthesize the kinamycins with much greater efficiency than previously possible.

As per the claim by the researchers,  key to the success of the route was the development of a three-step sequence for construction of the diazonapthoquinone (diazofluorene, blue in structure source : JACS) function of the natural product.

While scientists have produced kinamycins in the laboratory in the past, the Yale team was able to halve the number of steps required to go from simple, easily obtainable precursors to the complete molecule from 24 down to 12. 

This sequence comprises fluoride-mediated coupling of a β-(trimethylsilylmethyl)-cyclohexenone and halonapthoquinone, palladium-mediated cyclization to construct the tetracyclic scaffold of the natural product, and mild diazo-transfer to a complex cyclopentadiene to introduce the diazo function. Ortho-quinone methide intermediates, formed by reduction and loss of dinitrogen from (structure), have been postulated to form in vivo, and this approach provides a straightforward synthetic pathway to such compounds.

This research is of great importance because by shortening the synthesis one can now prepare these molecules in the quantities required for further studies, including animal studies and even clinical trials.

Working with researchers at the Yale School of Medicine and the Yale Chemical Genomics Screening Facility, the team has begun testing several of the compounds against cancer cells, with promising preliminary results. Next, they will work to understand the exact mechanism that makes the compounds,  which are benign on their own  highly toxic once they penetrate cells. Lead researcher Dr. Seth Herzon, says “the key to success will be whether they can develop selectivity – whether they can kill cancer cells in the presence of non-cancerous tissue“. Dr.Herzon  is also optimistic about lomaiviticin A (which also has the reactive core kinamycin,  and is even more toxic and could prove even more effective in destroying cancer cells)…let us hope positive results from this study….

Ref : http://pubs.acs.org/doi/abs/10.1021/ja910769j 

Celastrol, derived from trees and shrubs called celastracaea,  (Thunder of God Vine) has been used for centuries in China to treat symptoms such as fever, chills, joint pain and inflammation.Celastrol has been shown to possess antioxidant, anti-inflammatory activities. The same compound has been tried for Alzheimer’s disease and anticancer activity  also.

Now Dr. Ahmed Chadli, has come up with an interesting findings i.e., Celastrol may play a role in cancer treatment by inactivating a protein required for cancer growth.  Protein, P23, is one of many proteins helping the heat shock protein 90. Dr. Chadli claims that,  “scientists are just beginning to realize the potential of controlling inflammation-related diseases, including cancer, by inhibiting HSP90″.

As per  claim by Dr. Chadli, cancer cells need HSP90 more than normal cells because cancer cells have thousands of mutations. They need chaperones all the time to keep their mutated proteins active. By taking heat shock proteins away from cells, the stabilization is taken away and cell death occurs. 

Most HSP90 inhibitors lack selectivity, disabling the functions of all proteins activated by HSP90 rather than only the ones implicated in a specific tumor and proteins vary from one tumor to another. Dr. Chadli and colleagues at the Mayo Clinic believe celastrol holds the key to specificity, targeting the HSP90-activated protein required for folding steroid receptors.

Celastrol inhibits the Hsp90 chaperoning machinery by inactivating the co-chaperone p23, resulting in a more selective destabilization of steroid receptors compared with kinase clients. Both in vitro and in vivo results demonstrate that celastrol disrupts p23 function by altering its three-dimensional structure, leading to rapid formation of amyloid-like fibrils. This study reveals a unique inhibition mechanism of p23 by a small molecule that could be exploited in the dissection of protein fibrillization processes as well as in the therapeutics of steroid receptor-dependent diseases.…

In my earlier blog, I mentioned about the combination of Lapatinib and Trastuzumab for breast cancer treatment. Now FDA has  approved Lapatinib in combination with Letrozole (see structure ; Letrozole trade name Femara, an oral non-steroidal aromatase inhibitor for the treatment of hormonally-responsive breast cancer after surgery)  to treat hormone positive and HER2-positive advanced breast cancer in postmenopausal women for whom hormonal therapy is indicated. This drug combination of  Lapatinib  & Letrozole provides women being treated for advanced breast cancer with an important treatment option. 

The entirely oral treatment regimen works by targeting both HER2 and the hormone receptors, thereby slowing the cancer cells’ ability to grow or spread. As per the claim by  Dr. Richard Pazdur, (Director, Office of Oncology Drug Products, FDA’s Center for Drug Evaluation and Research) women with HER2-positive disease receiving the Lapatinib plus Letrozole combination more than doubled the time they lived without the cancer progressing compared with those receiving Letrozole alone (35 weeks vs. 13 weeks).

Lapatinib, was initially approved in combination with a chemotherapy drug, Xeloda (capecitabine) in 2007. This combination was used to treat women with advanced breast cancer tumors with the HER2 protein who had received prior treatment with chemotherapy drugs, including an anthracycline and a taxane, and Herceptin (trastuzumab), an anti-cancer antibody used to treat HER2-positive advanced breast cancer. Safety information from this study was consistent with previous Lapatinib clinical studies in advanced breast cancer. The most commonly reported side effects of the combination were diarrhea, rash, nausea and fatigue. Still clinical trials are to be carried out, in my opinion its a good achievement…

Ref : http://www.prnewswire.com/news-releases/fda-expands-use-of-approved-breast-cancer-drug-83072502.html

Poniard Pharmaceuticals, Inc,  claims that Phase 2 trial  study met its primary objective, that is picoplatin in combination with 5-fluorouracil and leucovorin (FOLPI regimen) was associated with a statistically significant reduction in neurotoxicity (p <0.004) compared to oxaliplatin given in combination with 5-fluorouracil and leucovorin (FOLFOX regimen). More…