Evaluation of α-hydroxycinnamic acids as pyruvate carboxylase inhibitors.

Through a structure-based drug design project (SBDD), potent small molecule inhibitors of pyruvate carboxylase (PC) have been discovered. A series of α-keto acids (7) and α-hydroxycinnamic acids (8) were prepared and evaluated for inhibition of PC in two assays. The two most potent inhibitors were 3,3'-(1,4-phenylene)bis[2-hydroxy-2-propenoic acid] (8u) and 2-hydroxy-3-(quinoline-2-yl)propenoic acid (8v) with IC50 values of 3.0 ±â€¯1.0 µM and 4.3 ±â€¯1.5 µM respectively. Compound 8v is a competitive inhibitor with respect to pyruvate (Ki = 0.74 µM) and a mixed-type inhibitor with respect to ATP, indicating that it targets the unique carboxyltransferase (CT) domain of PC. Furthermore, compound 8v does not significantly inhibit human carbonic anhydrase II, matrix metalloproteinase-2, malate dehydrogenase or lactate dehydrogenase.

A phase II study of single agent bortezomib in patients with metastatic breast cancer: a single institution experience.

PS-341, now known as bortezomib (Velcade[Millenium Pharmaceuticals, Inc., Cambridge, MA; and Johnson & Johnson Pharmaceutical Research & Development, LLC, Spring house, PA]), is a proteasome inhibitor approved for the treatment of refractory multiple myeloma. Preclinical and early clinical studies showed PS-341 to be effective in solid tumors, one of which was breast cancer. We conducted a single institution, phase II study using PS-341 in the treatment of patients with metastatic breast cancer. The primary objective of this study was to determine the objective tumor response in patients with metastatic breast cancer (MBC) receiving PS-341. The secondary objectives were to estimate progression-free survival of patients receiving single-agent PS-341 and to evaluate toxicity related to PS-341. In all 12 patients who met criteria for enrollment, there were no observed objective responses. Further, all 12 patients progressed while receiving therapy with PS-341. This study was terminated after the first stage due to the lack of any objective response.

HER2-positive breast cancer: current and future treatment strategies.

In the year 2006, breast cancer was estimated to affect >200,000 American women and cause nearly 56,000 deaths. Furthermore, breast cancer is the most common cancer diagnosed and second most common cause of cancer-related deaths in women. The current treatment armamentarium for breast cancer includes chemotherapy, endocrine therapy and biological therapy. Treatment has become more individualised based on characteristics of the tumour including overexpression of the human epidermal growth factor receptor (HER)-2. Between 20 and 30% of all breast cancers overexpress HER2, which means 40,000 - 60,000 patients will have this type of cancer.Previously, overexpression of HER2 was a negative prognostic and predictive risk factor for survival; however, with the advent of trastuzumab, patients' prognosis is improving in all treatment settings. Much controversy exists in the use of trastuzumab, including (i) the sequence of adjuvant trastuzumab (concurrent with chemotherapy or sequential); (ii) the treatment duration (<1 year, 1 year or 2 years); and (iii) the treatment choice upon disease progression (whether to continue or not with trastuzumab and add another cytotoxic agent). Current trials are ongoing to help answer these questions.Furthermore, there has been interest in predicting which HER2-positive patients would require anthracycline therapy, and which could avoid anthracycline therapy and its toxicities. Novel therapeutics, such as lapatinib, an oral tyrosine kinase inhibitor, which blocks both the epidermal growth factor receptor and HER2 receptor has recently been approved by the US FDA. Whereas pertuzumab, a humanised monoclonal antibody, directed against heterodimerisation of HER2 and HER3 has entered phase II and III clinical trials.

Role of efaproxiral in metastatic brain tumors.

Brain metastases from breast cancer are common and cause significant morbidity and mortality. Treatment with whole-brain radiotherapy provides a median survival of only 4-6 months. One mechanism affecting sensitivity to radiation is tumor oxygenation. Hypoxic tumor cells are more likely to be resistant to radiation and adversely affect prognosis. For nearly 70 years, all attempted modalities have failed to circumvent tumor hypoxia and increase tumor death. Abraham and colleagues developed a fibric acid derivative that would cause the displacement of oxygen from hemoglobin and improve tissue oxygenation. After modifications to enhance absorption into the red blood cell, RSR13 (efaproxiral) was developed. Efaproxiral was found to be safe and improved tumor oxygenation in preclinical studies. Early Phase I and II trials supported the earlier preclinical evidence while demonstrating that efaproxiral was safe and effective. A randomized Phase III study, Radiation Enhancing Allosteric Compounds of Hypoxic brain metastases (REACH, RT-009), failed to show a significant improvement in overall survival in all eligible patients treated with efaproxiral and whole-brain radiation. However, there was a statistically significant improvement in median survival and quality of life within a subset of metastatic breast cancer patients. Efaproxiral is currently being studied with radiotherapy in a confirmatory trial in the treatment of brain metastases from breast cancer. Furthermore, the combination of efaproxiral with radiotherapy is being investigated in other solid tumors.

Oxidative stress and apoptosis: a new treatment paradigm in cancer.

Redox regulation has been shown to be an important component of malignant cell survival. Tipping the cellular redox balance through pharmacologic regulation in favor of increasing intracellular reactive oxygen species (ROS) and/or depleting protective reducing metabolites (such as glutathione and nicotinamide adenine dinucleotide phosphate) may lead to oxidative stress and resultant induction of apoptosis for the treatment of cancer. We review the biology and importance of ROS with regard to malignant and normal cells. Moreover, we discuss pre-clinical and clinical data regarding novel therapeutic agents that modulate the cellular redox system including buthionine sulfoximine, ascorbic acid, arsenic trioxide, imexon, and motexafin gadolinium as single-agents and in combination. Continued research is needed to better understand the mechanisms and specific apoptotic pathways involved in ROS-induced cell death, as well as, to determine the most rationale and effective combination of redox-active agents.