Pharmacotherapy for obesity: a quantitative analysis of four decades of published randomized clinical trials

AIM

This article provides the first comprehensive meta-analysis of randomized clinical trials of medications for obesity.

METHOD

Based on stringent inclusionary criteria, a total of 108 studies were included in the final database. Outcomes are presented for comparisons of single and combination drugs to placebo and for comparisons of medications to one another.

RESULT

Overall, the medications studied produced medium effect sizes. Four drugs produced large effect sizes (ie d>0.80; amphetamine, benzphetamine, fenfluramine and sibutramine). The placebo-subtracted weight losses for single drugs vs placebo included in the meta-analysis never exceeded 4.0 kg. No drug, or class of drugs, demonstrated clear superiority as an obesity medication. Effects of methodological factors are also presented along with suggestions for future research.

Lifestyle treatments in randomized clinical trials of pharmacotherapies for obesity

OBJECTIVE

This meta-analysis evaluated the types of lifestyle treatments used in published obesity drug studies and assessed their contribution to weight losses associated with pharmacological interventions.

RESEARCH METHODS AND PROCEDURES

Randomized, placebo-controlled, double-blind clinical trials of anti-obesity agents that are/were Food and Drug Administration-approved for the treatment of obesity (both prescription and over-the-counter), and drugs that are Food and Drug Administration-approved and are used off-label for obesity were included. Studies were located by computer searches of databases (e.g., Medline, PsychInfo) and reviewing tables of content/reference sections of journals, abstracts, previous reviews, past empirical studies, relevant book chapters, and recent issues of journals that regularly publish obesity research. In addition, a number of individuals who regularly publish in the obesity literature were asked to provide personal lists of obesity-drug studies. Based on the above criteria, a total of 108 randomized clinical trials were located.

RESULTS

Balanced-deficit diets, low-calorie diets, and self-monitoring were the most used lifestyle treatments in published obesity studies. They were incorporated into 40.7%, 25%, and 23.1% of pharmacotherapy studies, respectively. Physical activity and other behavioral or psychotherapeutic interventions rarely were used. A substantial portion of weight loss experienced by patients was attributable to both "placebo effects" and to the lifestyle treatments.

DISCUSSION

Obesity-pharmacotherapy trials do not use lifestyle treatments with the frequency expected based on the official positions of most professional organizations concerned with the comprehensive management of obesity.

An examination of body weight standards and the association between weight and health behaviors in the United States Air Force

This study examined the weight standards used by the U.S. Air Force and tested whether Air Force personnel who exceed the maximum allowable weight standard are more likely to engage in health risk behaviors compared with individuals who do not exceed current Air Force weight standards. Participants were 32,144 individuals who completed basic military training from August 1995 to August 1996. Compared with body mass levels known to predict increased health risks, the Air Force maximum allowable weight standards were found to be more stringent for women than for men. Furthermore, exceeding the maximum allowable weight standard of the weight management programs did not consistently indicate that an individual engaged in a less healthy lifestyle than other airmen. Perhaps other risk factors, such as cigarette smoking, may be more closely linked to negative health consequences than body weight.

Stressors of college: a comparison of traditional and nontraditional students

Perceived stress and stressors of nontraditional (returning-adult) and traditional college students were compared. Forty-seven nontraditional students 24-54 years old and 47 traditional students, matched for demographics, completed the Adolescent Perceived Events Scale (Compas, Davis, Forsythe, & Wagner, 1987) for college students. They rated 210 life events according to the desirability, impact, and frequency of the events. Significant differences were found between the nontraditional and traditional students for events in the following categories: academics, peer and social relations, family and network, autonomy and responsibility, and intimacy. Nontraditional students enjoyed going to classes and doing homework more, whereas traditional students worried more about school performance. Peer events, including social activities, had much more impact on traditional students, whereas nontraditional students reported much more responsibility in the home. The results suggest that there are significant differences between the groups in their perceptions of stressors.

Chemotherapy of non-small cell lung carcinoma guided by an in vitro drug resistance assay measuring total tumour cell kill

Specimens from 45 patients with previously-untreated non-small cell lung cancer (NSCLC) were tested for in vitro chemosensitivity to ten drugs utilising the DiSC assay, which measures cell kill in the total (largely non-dividing) tumour cell population. Thirty-five assays were successful and 25 patients with advanced disease subsequently received chemotherapy with the 'best' three drugs selected by the assay. Six patients were Karnofsky performance status 60 or less and the median pretreatment weight loss was 8.5%. Nine patients had a partial response (response rate = 36%; 95% confidence interval = 17-55%) and the median survival of all patients was 202 days. Specimens from responding patients were significantly more sensitive in the assay to drugs in general (especially to etoposide and to 'natural product' drugs) and to the drugs used in treatment than were specimens from non-responding patients. In vitro drug resistance differences between responding and non-responding patients were of greater significance than were differences between other clinical and laboratory measurements. Assay results classified patients into two cohorts, having relatively high and low probabilities of responding to chemotherapy. Assay results also identified patient cohorts with above average and below average durations of survival. Five patients (20%) were found to have tumours with extreme drug resistance (EDR), defined as assay results for the average of all ten tested drugs falling greater than one standard deviation more resistant than the median for all tumours assayed, and none of these patients with EDR responded to chemotherapy.

Effect of prior cancer chemotherapy on human tumor-specific cytotoxicity in vitro in response to immunopotentiating biologic response modifiers

Tumor-specific cytotoxicity was measured in fresh human biopsy specimens by a modification of the differential staining cytotoxicity assay. ImuVert, a cytokine inducer derived from Serratia marcescens, which produces broad-spectrum activation of both macrophages and lymphocytes, was dramatically more effective when it was tested in tumors obtained from patients with previously treated, chemotherapy-responsive adenocarcinomas (breast and ovary) than when it was tested in tumors obtained from either previously untreated patients or previously treated patients with chemotherapy-refractory adenocarcinomas (colon, lung, pancreas, stomach, kidney, gallbladder, uterus, and prostate). Similar findings, relating to prior chemotherapy treatment status, were obtained for tumor necrosis factor and interferon gamma, but not for interleukin-2 or interferon alpha. On the basis of these findings and on other evidence in the literature, we speculate that response to chemotherapy produces massive release and processing of tumor antigens. We further speculate that this response leads to a state in which the human immune system is primed (via in situ vaccination) to respond to exogenous macrophage-activation signals with potent, specific antitumor effects.

Perturbation of in vitro drug resistance in human lymphatic neoplasms by combinations of putative inhibitors of protein kinase C

Fresh specimens of human lymphatic neoplasms were tested with the differential staining cytotoxicity assay. Cells from relapsed patients with acute lymphoblastic leukemia (ALL) were significantly more resistant to vincristine, dexamethasone, and doxorubicin in the assay than were cells from previously untreated patients. The putative C kinase inhibitors verapamil (V), imipramine (I), lidocaine (L), tamoxifen (T), chlorpromazine (C), and haloperidol (H) were then tested singly, in combination with each other (VILTCH, ITCH, and VL), and in combination with vincristine. At concentrations judged to be clinically achievable, VILTCH itself was occasionally toxic to ALL and chronic lymphocytic leukemia. The VILTCH combination clearly potentiated the cytotoxic activity of vincristine in five of eight ALL specimens from relapsed patients and potentiated vincristine in 18 of 30 chronic lymphocytic leukemia specimens. It also potentiated vincristine in two of six specimens of multiple myeloma and five of six specimens of non-Hodgkin's lymphoma. The VILTCH combination had no significant effects in fresh cultures of normal human lymphocytes. The most active drugs in the VILTCH combination appeared to be verapamil and lidocaine. We conclude that the differential staining cytotoxicity assay is a useful tool to study the circumvention of clinically acquired drug resistance. While the mechanism of the observed enhancement of the cytotoxic effects of vincristine is not known, it is possible that combinations of putative C kinase inhibitors may reduce drug resistance in human lymphatic neoplasms.

Selective enhancement by menadiol of in vitro drug activity in human lymphatic neoplasms

The effect of menadiol (vitamin K3) on fresh specimens of human lymphatic neoplasms (HLN) was tested by means of the differential staining cytotoxicity assay. Menadiol was tested alone and in combination with standard antineoplastic agents. Drug effects were then compared with the effects of the same drugs in normal human lymphocytes and in fresh specimens of human non-small cell lung cancer. By itself, menadiol was moderately toxic to HLN, but not to normal lymphocytes or non-small cell lung cancer. Menadiol, menadione, and two structurally related congeners were equitoxic to HLN cells, but sodium metabisulfite (present in menadiol solutions as a preservative) was nontoxic. Menadiol increased the cytotoxic effects of a number of standard agents in HLN but not in normal lymphocytes. Cell survival times with mechlorethamine, vincristine, and dexamethasone were converted from a range characteristic of drug resistance (ie, range observed in relapsed patients) to a range characteristic of drug sensitivity (ie, range observed in untreated patients) in the presence of menadiol. These effects occurred at a concentration (2.0 micrograms/ml; 4.7 microM) of menadiol which is probably clinically achievable and which did not deplete intracellular glutathione. Menadiol should receive clinical testing as a chemosensitizing agent in HLN.

Laboratory detection of primary and acquired drug resistance in human lymphatic neoplasms

We tested the ability of the differential staining cytotoxicity (DiSC) assay to discriminate between sensitive and resistant cell populations in human lymphatic neoplasms. First, the in vitro activity spectra of the most important drugs paralleled the known clinical activity spectra of the same agents. Second, there were highly significant correlations between in vitro chemosensitivity and the results of clinical chemotherapy. Third, specimens from previously untreated patients were significantly more sensitive to the most important drugs than were specimens from patients who had previously received chemotherapy. Finally, metachronous assays performed on specimens from the same patients showed little change in chemosensitivity if there had been no intervening chemotherapy between the times that the first and second assays were performed. However, if the patients had received intervening chemotherapy between the times of the first and second assays, the specimens in the second assays tended to be significantly more resistant than were the specimens in the first assays. These data indicate that the DiSC assay may be of value in the design of strategies to circumvent drug resistance in human lymphatic neoplasms.

A novel dye exclusion method for testing in vitro chemosensitivity of human tumors

Dissociated cancer cells are exposed to antineoplastic drugs (5 X 10(4) viable cells/drug for 1 hr or continuously) and cultured for 4 to 6 days in liquid medium. Cells are then stained with Fast green dye, sedimented onto slides with a Cytospin centrifuge, and counterstained with a modified hematoxylin and eosin technique. Dead cells stain with Fast green, and living cells stain with hematoxylin and eosin. Cell kill is calculated as percentage of control based on the relative numbers of living tumor cells, living non-tumor cells, and dead cells. Drug sensitivity could be assayed in 125 of 162 specimens of human neoplasms obtained from malignant effusions (16 of 18), excisional biopsies (31 of 44), needle biopsies (34 of 47), endoscopic biopsies (18 of 23), peripheral blood samples (19 of 20), and bone marrow aspirates (five of seven). The assays were successful (median of ten drugs tested) in: 46 of 64 adenocarcinomas; four of 11 squamous cell carcinomas; five of seven lymphomas; six of seven melanomas; two of four sarcomas; 18 of 20 transitional-cell carcinomas; 14 of 15 small-cell carcinomas; seven of eight myelomas; 12 of 12 chronic lymphocytic leukemias; seven of nine acute leukemias, and four of five "undifferentiated" carcinomas. The assay results demonstrated a strong correlation between the in vitro chemosensitivity of different types of tumors and the known clinical response patterns of these tumors. This assay can be used to determine which specific cells are killed in a heterogeneous cell population. Further work is needed to determine if this assay may be useful in blind screening trials for antineoplastic agents or if it may be of clinical use in predicting response to agents which are not cycle specific.

Comparison of dye exclusion assays with a clonogenic assay in the determination of drug-induced cytotoxicity

The following factors must be considered when dye exclusion assays are interpreted. (a) It may require several days for lethally damaged cells to lose their membrane integrity following a cytotoxic insult. (b) During this time, the "surviving" cells may continue to proliferate. (c) Also during this time, some lethally damaged cells may undergo an early disintegration, so that they are not present to be stained with dye at the end of the culture period. Factors b and c may cause an underestimate of cell kill when the results of the assay are based upon the traditional "percent viability" expression. In order to overcome these problems, an internal standard was developed and tested. This was based upon the addition of a constant number of permanently fixed duck erythrocytes to the cultures of cells from two different established tumor cell lines. Results were based upon comparisons of the ratios of "viable" tumor cells to duck erythrocytes on permanent cytocentrifuge slides prepared from the cultures. This novel "ratio" method was found to be a more sensitive index of drug-induced cell kill than the traditional percent viability method. A standard agar cloning assay gave somewhat higher estimates of cell kill than the ratio method, although both assays were in qualitative agreement for the drugs tested. All three assays demonstrated a clear dose-effect relationship for most of the drugs tested. Dye exclusion assays may have a useful role in chemosensitivity testing in vitro.