Synthesis and evaluation of 3-(dihydroxyboryl)benzoic acids as D,D-carboxypeptidase R39 inhibitors

Penicillin binding proteins (PBPs) catalyze steps in the biosynthesis of bacterial cell walls and are the targets for the beta-lactam antibiotics. Non-beta-lactam based antibiotics that target PBPs are of interest because bacteria have evolved resistance to the beta-lactam antibiotics. Boronic acids have been developed as inhibitors of the mechanistically related serine beta-lactamases and serine proteases; however, they have not been explored extensively as PBP inhibitors. Here we report aromatic boronic acid inhibitors of the D,D-carboxypeptidase R39 from Actinomadura sp. strain. Analogues of an initially identified inhibitor [3-(dihydroxyboryl)benzoic acid 1, IC(50) 400 microM] were prepared via routes involving pinacol boronate esters, which were deprotected via a two-stage procedure involving intermediate trifluorborate salts that were hydrolyzed to provide the free boronic acids. 3-(Dihydroxyboryl)benzoic acid analogues containing an amide substituent in the meta, but not ortho position were up to 17-fold more potent inhibitors of the R39 PBP and displayed some activity against other PBPs. These compounds may be useful for the development of even more potent boronic acid based PBP inhibitors with a broad spectrum of antibacterial activity.

Structural and mechanistic basis of penicillin-binding protein inhibition by lactivicins

Beta-lactam antibiotics, including penicillins and cephalosporins, inhibit penicillin-binding proteins (PBPs), which are essential for bacterial cell wall biogenesis. Pathogenic bacteria have evolved efficient antibiotic resistance mechanisms that, in Gram-positive bacteria, include mutations to PBPs that enable them to avoid beta-lactam inhibition. Lactivicin (LTV; 1) contains separate cycloserine and gamma-lactone rings and is the only known natural PBP inhibitor that does not contain a beta-lactam. Here we show that LTV and a more potent analog, phenoxyacetyl-LTV (PLTV; 2), are active against clinically isolated, penicillin-resistant Streptococcus pneumoniae strains. Crystallographic analyses of S. pneumoniae PBP1b reveal that LTV and PLTV inhibition involves opening of both monocyclic cycloserine and gamma-lactone rings. In PBP1b complexes, the ring-derived atoms from LTV and PLTV show a notable structural convergence with those derived from a complexed cephalosporin (cefotaxime; 3). The structures imply that derivatives of LTV will be useful in the search for new antibiotics with activity against beta-lactam-resistant bacteria.

Modification of estrone at the 6, 16, and 17 positions: novel potent inhibitors of 17beta-hydroxysteroid dehydrogenase type 1

The 17beta-hydroxysteroid dehydrogenases (17beta-HSDs) catalyze the interconversion between the oxidized and reduced forms of androgens and estrogens at the 17 position. The 17beta-HSD type 1 enzyme (17beta-HSD1) catalyzes the reduction of estrone to estradiol and is expressed in malignant breast cells. Inhibitors of this enzyme thus have potential as treatments for hormone dependent breast cancer. Here we report the syntheses and biological evaluation of novel inhibitors based on the estrone or estradiol template. These have been investigated by modification at the 6, 16 or 17 positions or combinations of these in order to gain information about structure-activity relationships by probing different areas in the enzyme active site. Activity data have been incorporated into a QSAR with predictive power, and the X-ray crystal structures of compounds 15 and 16c have been determined. Compound 15 has an IC50 of 320 nM for 17beta-HSD1 and is selective for 17beta-HSD1 over 17beta-HSD2. Three libraries of amides are also reported that led to the identification of inhibitors 19e and 20a, which have IC50 values of 510 and 380 nM respectively, and 20 h which, having an IC50 value of 37 nM, is the most potent inhibitor of 17beta-HSD1 reported to date. These amides are also selective for 17beta-HSD1 over 17beta-HSD2.

The regulation and inhibition of 17beta-hydroxysteroid dehydrogenase in breast cancer

17Beta-hydroxysteroid dehydrogenase Type 1 (17beta-HSD1) has a pivotal role in regulating the synthesis of oestradiol (E2) within breast tumours. In whole body studies in postmenopausal women with breast cancer the conversion of oestrone (E1) to E2 (4.4+/-1.1%) was much lower than the inactivation of E2 to E1 (17.3+/-5.0%). In contrast, an examination of in vivo oestrogen metabolism within breast tumours revealed that whereas little metabolism of E2 occurred, E1 was converted to E2 to a much greater extent in malignant (48+/-14%) than in normal (19+/-6%) breast tissue. Findings from these studies originally suggested that oestrogen metabolism within breast tumours may differ from the mainly oxidative direction found in most other body tissues and that the activity of 17beta-HSD1 might be regulated by tumour-derived factors. Several growth factors (e.g. IGF-I, IGF-II) and cytokines (e.g. IL-6, TNFalpha) have now been identified which can markedly stimulate the activity of 17beta-HSD1 and such a mechanism may account for the high concentrations of E2 found in most breast tumours. Cells of the immune system, which can infiltrate breast tumours, are thought to be a major source of the growth factors and cytokines which can modulate 17beta-HSD1 activity. Given the central role that 17beta-HSD1 has in regulating breast tumour E2 concentrations the development of potent inhibitors of this enzyme has recently attracted considerable attention. Our initial studies in this area explored the use of derivatives of E1 as inhibitors, with 2-ethyl- and 2-methoxy E1 being found to inhibit 17beta-HSD1 activity in T-47D breast cancer cells by 96+/-2 and 91+/-1% respectively at 10 microM, but with a lack of specificity. Using the E1 scaffold a number of potent, selective 17beta-HSD1 inhibitors have now been identified including E1- and 2-ethyl-E1 containing a side chain with a m-pyridylmethylamidomethyl functionality extending from the 16beta position of the steroid nucleus. At 10 microM these compounds both inhibited 17beta-HSD1 activity by >90%, however some inhibition of 17beta-HSD2 activity was exhibited by the E1 derivative (25%) but not the 2-ethyl analogue. It is now apparent that 17beta-HSD1 activity contributes to the high E2 concentrations found in most breast tumours. The identification of potent, selective novel 17beta-HSD1 inhibitors will allow their efficacy to be tested in in vitro and in vivo studies.

E-ring modified steroids as novel potent inhibitors of 17beta-hydroxysteroid dehydrogenase type 1

17beta-Hydroxysteroid dehydrogenases (17beta-HSDs) are an important class of steroidogenic enzymes that regulate the bioavailability of active estrogens and androgens and are as yet a relatively unexploited therapeutic target. Based on our investigations and those of others, E-ring modified steroids were identified as a useful template for the design of inhibitors of 17beta-HSD type 1, an enzyme involved in the conversion of estrone into estradiol. The synthesis and biological evaluation of a new series of N- and C-substituted 1,3,5(10)-estratrien-[17,16-c]-pyrazoles and the corresponding SAR are discussed. Among the N-alkylated analogues, the most potent inhibitor was the 1'-methoxyethyl derivative, 41, with an IC(50) of 530 nM in T47-D human breast cancer cells. The X-ray crystal structure of the 1'-isobutyl derivative, was determined. Further optimization of the template using parallel synthesis resulted in a library of C5'-linked amides from which 73 emerged. This pyridylethyl amide had an IC(50) of 300 nM and its activity, with that of 41, suggests the importance of hydrogen bond acceptor groups in the pyrazole side chain. Both 41 and 73 displayed selectivity over 17beta-HSD type 2, and preliminary investigations showed 41 to be nonestrogenic in vitro in a luciferase reporter gene assay in contrast to the parent pyrazole 25. Molecular modeling studies, which support these findings, and a QSAR, the predictive power of which was demonstrated, are also presented.

D-ring modified estrone derivatives as novel potent inhibitors of steroid sulfatase

A series of novel D-ring modified derivatives of estrone was synthesized and tested as inhibitors of steroid sulfatase (STS). The steroidal D-ring was cleaved via an iodoform reaction and thermal condensation of the resulting marrianolic acid derivative gave 16,17-seco-estra-1,3,5(10)-triene-16,17-imide derivatives, where a piperidinedione moiety is in place of the D-ring. This synthetic approach was found to give a higher overall yield than the literature method of Beckmann rearrangement. A range of alkyl side chains have been introduced on the nitrogen atom of the imido-ring and the corresponding 3-O-sulfamates synthesized. The new D-ring modified estrone derivatives bearing a propyl (39) and a 1-pyridin-3-ylmethyl (46) moiety had IC(50) values of 1 nM when tested in placental microsomes for the inhibition of STS. These compounds are therefore up to 18-fold more potent than EMATE, the very first highly potent irreversible steroidal STS inhibitor.

Novel D-ring modified steroid derivatives as potent, non-estrogenic, steroid sulfatase inhibitors with in vivo activity

In pursuit of novel steroid sulfatase (STS) inhibitors devoid of estrogenicity, several D-ring modified steroid derivatives were synthesised. In vitro evaluation of the compounds identified two highly potent inhibitors, 4a and 4b, which were 18 times more active than estrone-3-O-sulfamate (EMATE), both having IC(50) values of ca. 1nM. These 16,17-seco-estra-1,3,5(10)-triene-16,17-imide derivatives were synthesised from estrone, via the intermediate 1, which was easily alkylated, deprotected and sulfamoylated affording the final compounds in high yields. In order to assess their biological profile, the selected inhibitors were tested for their in vivo inhibitory potency and estrogenicity in ovariectomised rats. After an oral dose of 10mg/kg per day for 5 days, 4a and 4b were found to inhibit rat liver steroid sulfatase by 99%. They were also devoid of estrogenic activity in the uterine weight gain assay, indicating that these two leads have therapeutic potential for the treatment of hormone-dependent breast cancer.

Improving the cancer chemotherapy use process

PURPOSE

Reports of the tragic consequences of erroneous cancer chemotherapy overdoses at a prominent cancer center and a university hospital prompted a review of our institution's practices and those of 123 other hospitals to ascertain for each the current in-house process to prevent chemotherapy errors.

METHODS

A multidisciplinary committee of oncologists, nurses, and pharmacists reviewed the chemotherapy use process and identified opportunities for improvement. A 1-page facsimile survey was answered by 150 of 215 members of the American Society of Clinical Oncology (ASCO) who received it.

RESULTS

We further restricted the writing of cytotoxic chemotherapy orders to physicians who were board-certified or -eligible in hematology or medical, pediatric, and gynecologic oncology and their approved fellows. Dispensation of drugs is limited to oncology-certified pharmacists, and administration to chemotherapy-certified nurses. Standard orders are used either on special oncology forms or designated order sets in the computer. Procedures to regulate the ordering of antineoplastic drugs for nonmalignant indications by nononcology specialists are outlined. A process to prevent chemotherapy errors is in place in 95% of hospitals. Dedicated medical oncology units are ubiquitous, and most cancer centers and university hospitals have dedicated gynecologic and pediatric oncology units. Chemotherapy orders are generally written by oncology fellows and countersigned by an attending oncologist in cancer centers and university hospitals, whereas private oncology attending physicians write them in most community hospitals. Drugs are administered by oncology-certified nurses in most institutions.

CONCLUSIONS

These recommendations should improve the safety and effective use of chemotherapy and reduce the error rate to as close to zero as human fallibility will allow.

Observations on ethical problems and terminal care

Progress in medical diagnosis and therapy has raised new problems with far-reaching ethical implications. Medicine must remain a profession and not become a business. Textbooks must address ethical problems in the context of health care decisions and not restrict themselves to pathophysiology and practical therapeutics alone. The relative roles of the principles of autonomy, non-maleficence, beneficence, and justice must be balanced and appropriately applied to individual situations in biomedical ethics. When therapy becomes futile and the suffering of the patient does not justify any anticipated benefit, the patient (and/or patient surrogate) may request withholding or even withdrawing life-prolonging interventions. In the persistent vegetative state, even nutritional support by an unnatural (tube) route may ethically be denied at the patient's (or surrogate's) informed decision. New areas of ethical evaluation have been raised by the desire of some individuals to prolongation of their lives at high expense to the society such that other individuals are denied services because of limitation of available resources. There has been a long-standing conflict of interest between the acceptance by physicians and/or medical institutions of money or gifts from pharmaceutical companies whose drugs they prescribe, stock, or sell. This practice increases the cost of the drugs and is, in effect, a "sick tax," which is morally wrong.

High-dose pulse chlorambucil in advanced, low-grade non-Hodgkin's lymphoma

High-dose pulse chlorambucil was given orally at a dose of 16 mg/m2 daily for 5 consecutive days each month, as reported by Cadman et al. It was used to treat 33 patients with advanced, low-grade non-Hodgkin's lymphoma. With median follow-up of 4.2+ years, 70% of the patients achieved objective response. Eleven of 24 patients with follicular small cleaved cell lymphoma (FSCL) had pathological complete response; nine of 24 with FSCL and three of seven with small lymphocytic lymphoma had partial response. Median disease-free survival was 28 months. Actuarial survival for all patients was 60% at 5 years from initiation of therapy. Treatment toxicity was minimal. Pulse chlorambucil is an effective and minimally toxic palliative therapy for advanced FSCL.

A randomized study of low and high doses of leukocyte alpha-interferon in metastatic renal cell carcinoma: the American Cancer Society collaborative trial

A prospective randomized trial of low versus high doses of human leukocyte alpha-interferon (1 X 10(6) units/day for 28 days versus 10 X 10(6) units/day for 28 days) was carried out in 30 patients with metastatic renal cell carcinoma, to test the tolerance and relative antitumor effects of these interferon doses. Both doses were tolerated well, and responses to the human leukocyte alpha-interferon were observed overall in seven individuals, including complete, partial, and minimal tumor regressions. Six of the seven responses occurred in patients who received the high dosage, and three of these responses were major responses. While not statistically significant, this result suggested a dose-response relationship. One minimal response was observed in a patient treated at low dosage. Nine individuals who were stable after 1 month of therapy at low dosage were randomized to a further month of therapy at low or high dosage, during which one of four at high dosage had a partial response, and none of five at low dosage manifested response. Regression of pulmonary disease in one individual was delayed, occurring 3 months after therapy at the high dose and enduring for a period of 28 months. Major objective responses in other patients were of 4 and 15 months duration. Human leukocyte alpha-interferon is an active agent in renal cell carcinoma at the dosage of 10 million units daily. No relationship of toxicity to response was evident in this trial. Optimum dosage and duration of treatment have yet to be established.

Circulating factor XI antibody and disseminated intravascular coagulation

Association of a circulating factor XI anticoagulant and disseminated intravascular coagulation (DIC) is described in a 33-year-old woman. Although the patient had rheumatoid arthritis and a bacterial infection treated with antibiotics, the anticoagulant was thought to be secondary to systemic lupus erythematosus. Curiously, the low levels of factor XI did not prevent the DIC from developing.

Abdominal paracentesis for malignant ascites

Abdominal paracentesis for malignant ascites may be performed safely for several hours by insertion of a plastic tube through an intracatheter needle. The system is closed and sterile for up to 9 liters of drainage.

Abdominal paracentesis for malignant ascites

Abdominal paracentesis for malignant ascites may be performed safely for several hours by insertion of a plastic tube through an intracatheter needle. The system is closed and sterile for up to 9 liters of drainage.

Asymptomatic eyebrow mass. A rare presenting sign of malignant non-Hodgkin's lymphoma

A 60-year-old woman had a solitary mass in her left eyebrow that was first thought to be a dermoid cyst and following excision and histological examination was found to be a localized, malignant, non-Hodgkin's lymphoma of the mixed lymphocytic and histiocytic type. Subsequent lymphangiography after excisional biopsy of the left eyebrow mass demonstrated extensive para-aortic and inguinal lymph node involvement.