Synthesis and inhibitory activity of novel tri- and tetracyclic quinolines against topoisomerases.

A series of isoindolo[2,1-a]- and pyrrolo[1,2-a]quinolines were designed and synthesized for DNA-gyrase and topoisomerase-II inhibition studies. Some of the compounds showed significant activity against the enzymes.

DNA gyrase inhibitory and antimicrobial activities of some diphenic acid monohydroxamides.

The synthesis and inhibitory activity against DNA gyrase of a series of diphenic acid monohydroxamides 4a-f are described. A protocol of two biological assays showed conclusively that inhibition occurs specifically at the DNA-DNA gyrase complex and is not attributable to nonspecific inhibition. In the enzyme assays, 4c was potent as the prototypical quinolone, nalidixic acid (1), with an IC50 value of 58.3 micrograms/mL compared to 52 micrograms/mL for 1. MIC activity against bacterial strains showed a systematic drop for all compounds relative to 1. For compounds 4c-e, the addition of PMBN produced dramatic increases in MIC activity indicating that activity is likely to be related to membrane transport. Molecular modeling of 4a indicates that the diphenic acid monohydroxamides can bind to the DNA-DNA gyrase complex in a similar fashion as that hypothesized for the quinolone series according to the hypothesis suggested by Shen et al. but may not self-associate by pi-pi stacking. In contrast to the quinolone series, as the diphenic acid monohydroxamides are shown by molecular mechanics minimizations to be nonplanar, they may present novel approaches for chemotherapeutic intervention with a potential for decreased side effects.

A comparison of active site binding of 4-quinolones and novel flavone gyrase inhibitors to DNA gyrase.

The activity of 4-quinolone antibacterials at the enzyme target level is based on the well known and reported observations that 4-quinolone antibacterials target the Gyr A subunit of the DNA gyrase holoenzyme, inhibiting supercoiling while facilitating the "cleavable complex". Such inhibition can be observed by running the in vitro DNA gyrase supercoiling inhibition assay or the "cleavable complex" DNA gyrase assay. Although potency of the gyrase inhibitor is dependent on many factors including permeability and pharmacokinetics, the inherent potency of a gyrase inhibitor lies in its activity against the target enzyme. We have examined the binding activity of novel flavones [Bioorganic & Med. Chem. Letters 3:225-230, 1993] to Escherichia coli DNA gyrase and have found differences in binding consistent with inhibition of DNA gyrase supercoiling and ability to facilitate the cleavable complex, but of different rank order. [3H]norfloxacin was used in vitro competition studies with test compounds, pBR322 and E. coli DNA gyrase. Binding affinity results indicate the rank order of greatest to weakest binding (ability to compete with [3H]norfloxacin) of test compounds: Levofloxacin = ciprofloxacin > ofloxacin > norfloxacin > flavone compounds (including ellagic acid, quercetin, and compounds 5a through 5n [Bioorganic & Med. Chem. Letters 3:225-230, 1993]). Such differences in binding ability of the 4-quinolones and flavones to the ternary complex of DNA.DNA gyrase.drug, as compared to the catalytic inhibition and "cleavable complex" data, suggests a more complex binding of flavones than the previously hypothesized models for 4-quinolone binding.

Isokinetic trunk strength and lifting strength measures. Differences and similarities between low-back-injured and noninjured workers.

Fifty-eight back pain patients and 21 entry-level Postal Service workers without low-back pain were evaluated using a variety of lumbar function measures. Isolated trunk strength and full lifting strength were gauged with isokinetic and isometric methods. Lumbar range-of-motion was computed using toe-touch and goniometers. Conventional clinical techniques such as toe touch and straight leg raise were effective in distinguishing back-injured from normal subjects. Isometric and isokinetic peak force and torque tests failed to show significant differences between low-back pain and job applicant groups. When compared with published norms, our job applicant group was significantly deconditioned. Our data suggest that asymptomatic, deconditioned subjects could be mistaken for back-impaired patients or symptom magnifiers.

Testing potential gyrase inhibitors of bacterial DNA gyrase: a comparison of the supercoiling inhibition assay and "cleavable complex" assay.

Inhibitory activity of test compounds against Escherichia coli DNA gyrase in a "cleavable complex" assay, readily observed in vitro at the enzyme level by the artificial addition of a denaturing agent, is found to be an excellent indicator of 4-quinolone inhibition of DNA gyrase, and as accurate a predictor of target enzyme inhibitory activity as the measurement of the inhibition of DNA gyrase supercoiling. This study was designed to examine the specificity of DNA gyrase inhibitors of various chemical classes in these two DNA gyrase assays, and define the use of these two assays in understanding the nature of inhibition by experimental compounds. Supercoiling inhibition was detected by determination of the 50% inhibition level, and cleavable complex inhibition measured by the determination of the drug concentration at which 50% of the maximal (of control) formation of linear, cleaved DNA was obtained. Results indicate that these two assays can serve several different functions in microbiological research, among them: (1) quantitation of enzyme inhibitory activity at the target level; and (2) distinguishing between nonspecific inhibition or artifactual inhibition of DNA gyrase and true, mechanism-based inhibition of the catalytic activity of DNA gyrase.

Failure of adjuvant chemotherapy in testicular cancer.

Two cases of failure of adjuvant chemotherapy after retroperitoneal lymph node dissection of Stage II nonseminomatous germ cell tumors are described. In both cases, initial surgical resection was complete, and two cycles of chemotherapy with cisplatin, vinblastine, and bleomycin were administered in an appropriate dose and schedule. Although one patient remains without evidence of disease 12 months after initiation of salvage chemotherapy with cisplatin, etoposide, and bleomycin, the other patient died of progressive disease despite intensive treatment with cisplatin and etoposide. Adjuvant therapy for Stage II germ cell tumors is not conventional treatment, and should be applied only in investigative settings where the long term effects and toxicity can be monitored, and does not reduce the need for frequent and thorough follow-up of treated patients.

Combined modality therapy for adults with small noncleaved cell lymphoma (Burkitt's and non-Burkitt's types).

Between June 1979 and June 1984 18 adult patients with small noncleaved cell lymphoma (SNCL) (diffuse undifferentiated lymphoma, Burkitt's and non-Burkitt's types of the Rappaport classification) were treated with high-dose cyclophosphamide, doxorubicin, vincristine, prednisone, midcycle high-dose methotrexate, and intrathecal methotrexate. Early in the course of treatment, hyperfractionated radiotherapy (125 cGy, every two days, for 1,500 to 2,250 centigray [cGy]) was administered to unresected masses greater than 10 cm in their greatest dimension. Chemotherapy was administered every 21 days for six to ten cycles. Treatment was generally well tolerated; however, one patient died of probable tumor lysis syndrome. With a median follow-up of 1.2 years, actuarial survival was 66.8% and relapse-free survival (RFS) was 71.3% for the entire group. All treatment failures and deaths occurred in patients with stage D disease. RFS projected at 2 years was 100% for stages A and AR and 60.6% for stage B, C, and D (P = .13 Gehan). Two-year RFS for patients with stage A, AR, B, or C disease was 100 v 41% for those with stage D disease. Patients with adverse prognostic features (n = 7)--unresected bulk measuring greater than 10 cm, pretreatment serum lactate dehydrogenase (LDH) 500 IU/L (normal, 200) or involvement of CNS or bone marrow--had a projected RFS of 28.6% compared with 100% for those patients without these features (P = .002 Gehan). Too few patients received induction radiotherapy to assert its role in therapy. By using aggressive multiagent therapy, cure can be expected in a high percentage of adults with SNCL. In the subset with adverse prognostic features, more effective therapy is necessary.

A phase II study of cisplatin and cytosine arabinoside for recurrent squamous cell carcinoma of the head and neck.

Based on experimental data suggesting synergy between cisplatin and cytosine arabinoside, 17 patients with recurrent squamous cancer of the head and neck were treated with this combination. The response rate was 18% with no complete responses, and the partial responses were of brief duration. There were moderate hematologic and gastrointestinal toxicities and two therapy-related deaths. The study was stopped early because of low response. When compared to results reported for cisplatin alone, the combination of cisplatin and cytosine arabinoside offered no clear advantage.