Concomitant botanical medicine use among patients participating in commercial prostate cancer trials

OBJECTIVES

Patients with cancer frequently use botanical medications. The concomitant use of such medications by patients on commercial trials has not been well-described, despite the importance of these trials for evaluating the safety and efficacy of new agents. We sought to describe the use of botanical medications taken by patients with prostate cancer enrolled on global commercial trials.

DESIGN

Retrospective study.

SETTING

Regulatory repository of commercial clinical trial data.

INTERVENTIONS

Anti-cancer therapy.

MAIN OUTCOME MEASURES

Botanical and medication use data were pooled across six international commercial randomized trials for metastatic prostate cancer with detailed information on medication and indications. Botanical products were considered to have potential for drug interaction if they led to a change in drug exposure in human trials. Potential for interaction was ascertained by PubMed review. Descriptive statistics were used for analysis.

RESULTS

Of 7318 enrolled patients, 700 (10 %) reported botanical use at any time and 653 (9%) reported use of botanical products while on trial. Nearly half of botanical product types were not classified by plant (43 %). The highest proportion of botanical use was among patients in Asian countries (32 %), followed by patients in North America (13 %). Eighty-six different types of botanical products were used; of these, nineteen had a patient-reported anti-cancer indication.

CONCLUSIONS

Botanical medicine use among patients with prostate cancer in commercial trials is moderate, although it varies by region. Practitioners should be aware of the use of botanical interventions in a clinical trial context.

A Food and Drug Administration analysis of survival outcomes comparing the Adjuvant Paclitaxel and Trastuzumab trial with an external control from historical clinical trials

BACKGROUND

Although the Adjuvant Paclitaxel and Trastuzumab (APT) trial has been adopted clinically, single-arm trials have limitations, and interest remains whether these patients with small node-negative human epidermal growth factor receptor 2 (HER2)-positive early breast cancer (EBC) would benefit from more intensive chemotherapy. This analysis explored whether external controls can contextualize single-arm studies to add to clinical decision making in the use of de-escalated therapy in patients with low-risk HER2-positive EBC.

PATIENTS AND METHODS

Patient-level data from five randomized trials supporting drug approval in adjuvant HER2-positive EBC were pooled, and patients with low-risk EBC were selected (n = 1770). Patients treated concurrently with trastuzumab and either anthracycline/cyclophosphamide/taxane/trastuzumab (ACTH) or taxane/carboplatin/trastuzumab (TCH; n = 1366) were matched (1:1) to patients treated with paclitaxel and trastuzumab (TH) in the APT trial (n = 406) using propensity scores. Patients treated with anthracycline/cyclophosphamide/taxane (ACT; n = 374) were also matched (1:1) to those treated with TH. Propensity scores were estimated using covariates of age, tumor stage, estrogen receptor status, progesterone receptor status, and histological grade.

RESULTS

After matching, the estimated probabilities of invasive disease-free survival (iDFS) at 3 and 5 years were 98.6% and 96.5% in the TH arm, and 96.6% and 92.9% in the ACTH/TCH arm, respectively. The estimated probabilities of overall survival (OS) at 3 and 5 years were 99.7% and 99.3% in the TH arm, and 99.0% and 97.4% in the ACTH/TCH arm, respectively. Comparing the TH arm with the ACT arm in the matched sample, the estimated difference in iDFS was 7.5% (TH 98.8% and ACT 91.3%) at 3 years and 12.6% (TH 96.1% and ACT 83.5%) at 5 years. The estimated difference in OS was 2.6% (TH 100% and ACT 97.4%) at 3 years, and 5.3% (TH 99.3% and ACT 94.0%) at 5 years.

CONCLUSIONS

Our analyses suggest that patients' outcomes in both arms were in general similar, thus providing additional reassurance regarding de-escalation of therapy.

'Socialised care futility' in the care of older people in hospital who call out repetitively: An ethnographic study

BACKGROUND

People living with dementia may call out repetitively, sometimes called disruptive vocalisation, or verbal agitation. In literature and policy, patients who call out repetitively are assumed to be expressing an unmet need, which should be met. Yet there has been little systematic study of this patient group in an acute hospital setting.

OBJECTIVES

To better understand patients who call out repetitively and to identify what care looks like in an acute hospital setting.

DESIGN

Ethnography.

SETTINGS

Ten acute geriatric medical wards in two hospitals.

PARTICIPANTS

30 cognitively impaired patients who were calling out repetitively, and 15 members of hospital staff.

METHODS

Semi-structured interviews with hospital staff, 150 h of ward observations and informal conversations with staff, scrutiny of medical and nursing documentation, and measures of patient health status.

RESULTS

Patients who called out were moderately or severely cognitively impaired, often had delirium, were very physically disabled, and many were approaching the end of life. Most hospital staff were found to hold contradictory views: that calling out represents distress or unmet need, but that nothing can be done to alleviate the calling out. During informal conversations, most staff also tended to say that they intuitively recognised when intervening was likely to alleviate calling out. During observations, many staff appeared to and spoke of the ability to 'block' calling out. As a result we argue that social, emotional and physical needs may get overlooked. We argue that some calling out is due to a need that is unmeetable. We also found that while staff would talk about strategies for identifying need, observations and hospital documentation did not support evidence of systematic attempts to identify potential need.

CONCLUSION

Calling out repetitively within a hospital setting is difficult for staff to understand and to respond to. This is because many of these patients are severely cognitively impaired, often immobile and dependent on their professional carers. We argue that a form of socialised care futility is communicated between staff and is used to rationalise becoming unresponsive to calling-out. We explain this phenomenon as resulting from two protective mechanisms: defence of staff's professional identity as competent practitioners; and defence of staff as having personal morality. Socialised care futility risks good quality care, therefore systematic strategies to assess and manage possible need should be developed, even if calling out remains irresolvable in some cases.

Abstract ES5-3: Development of molecular and genomic biomarkers: A regulatory path forward

Due to advancements in tumor genomics, and a better understanding of the molecular subtypes and heterogeneity of breast cancer, there is great interest in molecular and genomic biomarker development.

There are many ways in which molecular and genomic biomarkers can be incorporated into breast cancer clinical trials. Diagnostic biomarkers can be utilized to identify a more homogeneous cancer population to study. Prognostic or predictive biomarkers can be useful for trial stratification and enrichment. Biomarkers of tumor response could be incorporated into clinical trials leading to earlier evaluations of antitumor activity. There is also the potential for a response biomarker to be studied as a potential surrogate endpoint or efficacy-response biomarker that is intended to substitute for a clinical endpoint expected to predict long-term outcome.

Biomarkers can become accepted by the US Food and Drug Administration for use in therapeutic product (either a novel product or an existing product with a new indication) development via two potentially complementary regulatory pathways. The first is in the context of a specific therapeutic product within an investigational new drug application and ultimately included in a drug label after approval of both a therapeutic product and a companion diagnostic device. This pathway requires close collaboration between Center for Drug Evaluation and Research (CDER) and Center for Devices and Radiological Health (CDRH). During drug development, CDRH will assess the investigational biomarker test and determine the level of risk that the device may present to the health and safety of patients; CDER will provide guidance on the clinical trial design and the biomarker development plan in the context of the product. At the time of the NDA or BLA submission, if the biomarker test is deemed essential for the safe and effective use of the therapeutic product, then the companion diagnostic is expected to be approved or cleared contemporaneously with the corresponding therapeutic product. The companion diagnostic is reviewed by CDRH to determine if there is valid scientific evidence to provide reasonable assurance that the device is safe and effective for its intended use. CDER will perform the appropriate NDA or BLA review with consideration of the biomarker. If appropriate, the biomarker would then become accepted in the context of the therapeutic product and disease setting and be incorporated in the label. The second pathway is through the FDA biomarker qualification program where a pharmaceutical developer, health research group, patient foundation, or consortium may request regulatory “qualification” of a biomarker. A multidisciplinary team is formed, advice is given, and if qualified, a biomarker can be relied upon to have a specific interpretation and application in drug development and regulatory review within the stated context of use for clinical trials across different therapeutic products.

Biomarkers should continue to be a priority through drug development and communication with FDA is critical to successful incorporation of biomarkers into clinical trials. Biomarkers used correctly in clinical trials have the potential to advance the development of highly effective treatments for breast cancer patients.

Citation Format: Beaver JA. Development of molecular and genomic biomarkers: A regulatory path forward. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr ES5-3.

Abstract PD6-08: IMAGE: Individualized molecular analyses guide efforts in breast cancer with comprehensive genomic profiling of tissue and plasma tumor DNA

Background: Standard treatment options for patients with metastatic triple negative breast cancer (TNBC) are limited to chemotherapy. Molecular profiling of tumors may allow for novel treatment recommendations.

Methods: We initiated a prospective study designated IMAGE. Women with newly progressing metastatic TNBC who received at least one line of prior chemotherapy were eligible. New metastatic biopsies were obtained for molecular profiling at study entry. Archived metastatic biopsy specimens were allowed if patients had not commenced new systemic therapy. The specimens were reviewed by the study pathologist and stained for ER, PR, HER2, and androgen receptor (AR) by immunohistochemistry. Specimens underwent hybrid-capture based comprehensive genomic profiling (CGP) (Foundation Medicine Inc., Cambridge, MA). Clinical data and genomic profiling reports were reviewed by the GAITWAY (Genomic Alterations in Tumors with Actionable Yields) Molecular Profile Tumor Board. Recommendations were communicated to the treating oncologist and patients were followed for treatment decision and clinical outcomes. Peripheral blood was also analyzed by an investigational assay for circulating plasma tumor DNA (ptDNA) (Foundation Medicine Inc.) at study entry, and when obtainable, from serial blood draws at time of progression. The primary objective was to assess feasibility of completing the process from consent to GAITWAY recommendations within 28 days for at least 80% of patients.

Results: From September 2013 to April 2015, we enrolled 26 eligible women. Median age was 55 (range 25-67); patients identified as white 12 (46%), black 11 (42%), or other 3 (12%); median number of prior lines of treatment was 3; and 65.4% of patients had visceral disease. Twenty (77%) eligible patients received CGP of a metastatic site biopsy. Six patients did not undergo CGP due to either absence of a metastatic site amenable for biopsy or inadequate tissue for CGP. The study met the predefined statistical endpoint for futility and was closed after 20 patients had undergone CGP. Twelve (60%) evaluable patients received treatment recommendations within 28 days of study consent. Failure to meet this time frame was due to difficulties in accessing archival tumor tissue (N=5) and need for additional tissue for molecular analysis (N=3). Preliminary results demonstrate high concordance between mutations in metastatic biopsies and ptDNA in 15/17 patients.

Enrolled in IMAGE26Successful NGS20Potentially actionable mutation identified15GAITWAY recommended targeted therapy as possible next treatment13Received targeted therapy4

Conclusions: CGP of patients with metastatic TNBC can provide additional information that may help direct treatment. However, difficulties in obtaining adequate tumor tissue may hinder this approach. Use of a well-validated ptDNA profiling assay could be an alternative to overcome these limitations.

Citation Format: Parsons HA, Beaver JA, Cimino-Mathews A, Zorzi J, Slater S, Clark T, Lipson D, Ali SM, Kennedy M, Otto GA, Young LE, Jeter S, VanDenBerg DA, Rosner GL, Park BH, Stearns V. IMAGE: Individualized molecular analyses guide efforts in breast cancer with comprehensive genomic profiling of tissue and plasma tumor DNA. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr PD6-08.

Pneumopericardium mimicking acute myocardial ischemia after laparoscopic cholecystectomy

Pneumopericardium occurred after laparoscopic cholecystectomy in a 57-year-old woman. The patient had chest pain accompanied by T-wave inversion on electrocardiogram, with signs and symptoms suggestive of acute myocardial ischemia. Evaluation for myocardial infarction, however, was negative and clinical findings resolved spontaneously. Although pneumopericardium after laparoscopic procedures has been previously reported, this case illustrates how associated findings may mimic those of acute myocardial ischemia or infarction.

Increased cell surface exposure of phosphatidylserine on propidium iodide negative thymocytes undergoing death by necrosis

Phosphatidylserine (PS) exposure on propidium iodide negative cells using FITC labelled annexin-V has been used to quantify apoptosis in vitro and in vivo. Detection of PS within cells undergoing necrosis is also possible if labelled annexin-V specific for PS enters the cell following early membrane damage. Necrotic or late apoptotic cells can be excluded from flow cytometric analysis using propidium iodide which enters and stains cells with compromised membrane integrity. Here we show that thymocytes undergoing death exclusively by necrosis show early exposure of PS prior to loss of membrane integrity. This early exposure of PS occurs in cells treated with agents which both raise intracellular calcium levels and are also capable of interacting with protein thiol groups. We also demonstrate that PS exposure in thymocytes induced to undergo apoptosis by three different agents does not correlate with calcium rises but correlates with and precedes DNA fragmentation.

Gliotoxin and related epipolythiodioxopiperazines

1. Gliotoxin belongs to the epipolythiodioxopiperazine class of secondary metabolites. These compounds show a diverse range of biological activity including antimicrobial, antifungal and antiviral properties. They also display potent in vitro and in vivo immunomodulating activity. 2. Their properties resulted in a number of early studies designed to exploit their possible chemotherapeutic value, although the general toxicity of most members of this class has precluded clinical use. 3. Most recently, their selective immunosuppressive properties have led to the possibility of ex vivo treatment of tissue to selectively remove immune cells responsible for tissue rejection. The mode of action of gliotoxin appears to be via covalent interaction to proteins through mixed disulphide formation and gliotoxin has been shown to inhibit a number of thiol requiring enzymes. 4. Gliotoxin is also a potent inducer of apoptotic cell death in a number of cells. Gliotoxin and other members of this class of toxins may be produced in vivo during the course of fungal infections and contribute to the aetiology of the disease.

Prognostic significance of serum c-erbB-2 protein in breast cancer patients

The tissue expression of c-erbB-2 protein in breast cancer is a marker of poor prognosis in a number of studies. More recently it has also been suggested that c-erbB-2 expression may predict response to systemic therapy in patients with advanced breast cancer. The measurement of c-erbB-2 protein in the serum of breast cancer patients has now been reported, but the significance of this finding is not clear. In this study an ELISA assay was used to measure c-erbB-2 in the sera of 23 normal controls, 46 benign breast disease patients, and 119 breast cancer patients. Elevated serum c-erbB-2 protein levels were detected in 13% (3/23) of normal controls, 15% (7/46) of benign disease patients, 15% (7/46) of Stage I/II patients, 26% (9/35) of Stage III patients, and 21% (8/38) of Stage IV patients. The tissue expression of the c-erbB-2 protein showed no association with detection of the serum c-erbB-2 protein (p = 0.31). In the 67 Stage III and IV patients who had assessable disease the presence of the c-erbB-2 protein in the serum bore no relationship to response to hormonal therapy (p = 0.71). Serum detection of the c-erbB-2 protein in Stage I/II patients predicted for a worsening of both survival outcome (p = 0.002) and disease free interval (p = 0.002). A worse outcome was also seen for the Stage III patients (p = 0.04) and Stage IV patients, although the latter did not reach statistical significance (p = 0.27). This study found that the presence of c-erbB-2 in the serum of breast cancer patients was of prognostic significance for all stages of disease.

Cyclosporin A rescues thymocytes from apoptosis induced by very low concentrations of thapsigargin: effects on mitochondrial function

Raising intracellular calcium levels can induce apoptosis or programmed cell death in many cells. While early rises in intracellular calcium are not universally associated with apoptotic cell death, calcium clearly plays a key role in many of the biochemical events which occur during apoptosis. In this paper we have determined intracellular calcium rises induced by 2, 10, and 100 nM thapsigargin in mouse thymocytes. These concentrations cause increases in cytosolic calcium of 100-250, 400-600, and > 1000 nM, respectively. These rises are sustained for at least 85 min and the ratio between the maximum rise caused by 10 nM compared to 2 nM thapsigargin is 2.1 +/- 0.4 (n = 6). Both 2 and 10 nM thapsigargin cause apoptosis at 24 h as shown by DNA fragmentation and morphology when examined by electron microscopy. Cyclosporin A (CsA) inhibits apoptosis caused by 2 nM thapsigargin but not that caused by 10 nM thapsigargin. Electron microscopy of thymocytes treated with 2 nM thapsigargin at 24 h shows intact mitochondria although with altered morphology. There is no loss of ATP or decrease in the ATP/ADP ratio in these cells over 12 h. Mitochondria in cells treated with 10 nM thapsigargin, however, are swollen by 6 h and many are lost by 24 h. These cells show greatly diminished ATP content by 12 h and a decrease in ATP/ADP ratio. Examination of the effects of PMA, an activator of the plasma membrane calcium ATPase pump, on cells treated with 10 nM thapsigargin suggests that two pools of calcium may be responsible for the differential effects of the two calcium levels in the cells. Probing of the mitochondrial membrane potential (MMP) by rhodamine 123 staining of live cells shows that the collapse of the MMP caused by 10 nM thapsigargin is unaffected by CsA. The MMP is also reduced in cells treated with 2 nM thapsigargin but this is restored by CsA. Cells are also rescued from apoptosis caused by 2 nM thapsigargin by incubation with FK506. This immunosuppressive agent has no effect on the membrane permeability transition induced in isolated mitochondria. These results suggest that very low rises in intracellular calcium in thymocytes cause activation-induced cell death inhibited by CsA and FK506 and are without effect on ATP levels and therefore do not involve irreversible mitochondrial damage. Exceeding these calcium levels by only two-fold results in apoptosis accompanied by reduced ATP levels and mitochondrial damage, although apoptotic cell death in this instance is unaffected by the classic inhibitor of mitochondrial permeability transition, CsA.

Evidence that gliotoxin enhances lymphocyte activation and induces apoptosis by effects on cyclic AMP levels

Gliotoxin is a secondary metabolite produced by several pathogenic fungi. It has potential clinical applications as an immunosuppressive agent in preventing allograft rejection. At low doses (< 30 nM) gliotoxin displays co-mitogenic activity, but at higher doses induces apoptosis in cells. Here we demonstrate that gliotoxin, although not mitogenic in its own right, enhances activation in preactivated splenocytes by a calcium-independent mechanism. The enhancement in activation correlates with a decrease in intracellular cyclic AMP levels. This property is inhibited by dibutyryl-cAMP. Increasing the concentration of gliotoxin to levels that caused apoptosis produced a dose-related increase in cAMP levels. Thus, the effects of gliotoxin on cell activation and the induction of apoptosis may both be mediated by changed levels of cAMP.

Serum tissue polypeptide specific antigen (TPS) in breast cancer patients: comparison with CA 15.3 and CEA

Pre-treatment TPS serum levels from patients with Stage IV breast cancer (n = 66) (1386.0 +/- 3504.5) were significantly higher (p < 0.0001), than normal controls (n = 47), (75.5 +/- 111.5 U/L), benign breast disease patients (n = 84) (58.5 +/ 57.1 U/L), and breast cancer patients with Stage I/II (n = 79) (52.7 +I- 49.5U/L) or Stage III disease (n = 57) (166.7 +/- 218.8). Analysis of sequentially obtained samples from Stage IV patients during endocrine treatment showed TPS alone or in combination with CEA and CA 15.3 was less accurate in predicting response than the combination of CEA with CA 15.3. In this study TPS did not usefully add to the established marker combination of CEA and CA 15.3.

Isozyme diversity in sour, sweet, and ground cherry

Thirty-six sour (Prunus cerasus L.), sweet (P. avium L.), and ground cherry (P. fruticosa Pall.) selections were evaluated for seven enzyme systems and principal coordinate analysis was used to examine isozyme divergence among these cherry species. The enzyme systems studied were phosphoglucose isomerase (PGI), isocitrate dehydrogenase (IDH), phosphoglucomutase (PGM), 6-phosphogluconate dehydrogenase (6-PGD), leucine aminopeptidase (LAP), shikimate dehydrogenase (SKDH), and malate dehydrogenase (MDH). The first principal coordinate, which accounted for 41% of the total variation, separated the diploid sweet cherry selections from the sour, ground, and sour x ground cherry tetraploids. An additional 86 selections were evaluated for up to six of the enzyme systems to determine the polymorphisms at the enzyme loci and the level of heterozygosity between the diploid sweet cherry and the tetraploid species and interspecific hybrids. 6-PGD was the most polymorphic enzyme exhibiting 16 patterns. The tetraploid cherry species were more heterozygous than the diploid sweet cherry with an average heterozygosity of 78% compared to 19% for the diploids.

Haemoglobin inhibition of fibrin polymerization and clotting

Clotting of human plasma by human alpha-thrombin was prolonged in the presence of haemoglobin as was human and bovine fibrinogen. Specifically, the clot time doubled for human plasma, human fibrinogen and bovine fibrinogen at 483, 233, and 116 microM haemoglobin, respectively. Fibrinopeptide A release was not inhibited at concentrations in approximately 16,000 molar excess compared with alpha-thrombin. Turbidometric analysis of fibrin polymerization showed a lengthening of the lag phase as well as the fibrin assembly process in the presence of haemoglobin. These findings suggested that neither fibrinogen recognition nor catalytic efficiency of thrombin was affected, implying that haemoglobin interferes with fibrin polymerization. Since human blood contains sufficient haemoglobin in erythrocytes to generate concentrations of up to 2.3 mM upon cell lysis, and haemoglobin concentrations of 0.16-0.48 mM caused 1.25 to two times longer clotting times in fresh human plasma, respectively, haemoglobin may act to modulate clot formation under conditions of haemolysis.

Improving efficiency of breeding for higher crop yield

Exclusive selection for yield raises, the harvest index of self-pollinated crops with little or no gain in total bipmass. In addition to selection for yield, it is suggested that efficient breeding for higher yield requires simultaneous selection for yield's three major, genetically controlled physiological components. The following are needed: (1) a superior rate of biomass accumulation. (2) a superior rate of actual yield accumulation in order to acquire a high harvest index, and (3) a time to harvest maturity that is neither shorter nor longer than the duration of the growing season. That duration is provided by the environment, which is the fourth major determinant of yield. Simultaneous selection is required because genetically established interconnections among the three major physiological components cause: (a) a correlation between the harvest index and days to maturity that is usually negative; (b) a correlation between the harvest index and total biomass that is often negative, and (c) a correlation between biomass and days to maturity that is usually positive. All three physiological components and the correlations among them can be quantified by yield system analysis (YSA) of yield trials. An additive main effects and multiplicative interaction (AMMI) statistical analysis can separate and quantify the genotype × environment interaction (G × E) effect on yield and on each physiological component that is caused by each genotype and by the different environment of each yield trial. The use of yield trials to select parents which have the highest rates of accumulation of both biomass and yield, in addition to selecting for the G × E that is specifically adapted to the site can accelerate advance toward the highest potential yield at each geographical site. Higher yield for many sites will raise average regional yield. Higher yield for multiple regions and continents will raise average yield on a world-wide basis. Genetic and physiological bases for lack of indirect selection for biomass from exclusive selection for yield are explained.

Interaction of sulfonamide and sulfone compounds with Toxoplasma gondii dihydropteroate synthase

Toxoplasma gondii is a common protozoan disease that often causes life-threatening disease, particularly among patients with the acquired immunodeficiency syndrome. This study demonstrates that the dihydropteroate synthase in T. gondii is kinetically distinct from the enzyme characterized from other sources and can be highly purified with a high yield using sequential dye-affinity chromatography. Conditions have been identified that allow for stabilization of the purified enzyme, and its physical characteristics have been elucidated. The molecular weight of the native protein was 125,000 and the protein appeared to contain both dihydropteroate synthase and 6-hydroxymethyl-dihydropterin pyrophosphokinase activities. The sulfonamide class of compounds vary in inhibitory potency by more than three orders of magnitude. Sulfathiazole, sulfamethoxazole, and sulfamethazine, with 50% inhibitory concentrations (IC50's) of 1.7, 2.7, and 5.7 microM, respectively, represent the most potent of this class of inhibitors. Several sulfone analogues, including dapsone, were identified as highly potent inhibitors with IC50's less than 1 microM. The results of these cell-free experiments were corroborated by investigating the metabolic inhibition produced by the various inhibitors in intact organisms. The qualitative and quantitative relations among the inhibitors were preserved in both the cell-free and intact cell assay systems. These studies suggest that the sulfones may be important therapeutic agents for the treatment of toxoplasmosis.

Characterization of de novo folate synthesis in Pneumocystis carinii and Toxoplasma gondii: potential for screening therapeutic agents

Drug therapy studies imply that Pneumocystis carinii and Toxoplasma gondii possess the enzymes necessary for de novo folate synthesis. To verify this, incorporation of [3H]paraaminobenzoic acid [( 3H]PABA) into reduced folates by P. carinii and T. gondii was investigated. Both organisms synthesized tritiated reduced folates. In P. carinii, 10-formyltetrahydrofolate and tetrahydrofolate, and in T. gondii, 5-formyltetrahydrofolate were the major synthesized folates. P. carinii remained metabolically active in vitro for only a few days. Because current systems for screening antipneumocystis agents are cumbersome, the utility of this assay system for screening therapeutic agents was investigated. Sulfonamides and pentamidine efficiently inhibited de novo folate synthesis in P. carinii. Inhibitors of dihydrofolate reductase such as trimethoprim and trimetrexate were poor inhibitors for P. carinii but efficient inhibitors for T. gondii. This study demonstrates the first unambiguous evidence of metabolic activity in P. carinii, and provides a potential assay for efficiently screening antipneumocystis drugs in vitro.

Pasteurella multocida septicemia during pregnancy

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