Effectiveness of Chinese Herbal Medicine as a Complementary Treatment for Neutropenia Prevention and Immunity Modulation During Chemotherapy in Patients With Breast Cancer: Protocol for a Real-World Pragmatic Clinical Trial

BACKGROUND

In recent years, advancements in cancer treatment have enabled cancer cell inhibition, leading to improved patient outcomes. However, the side effects of chemotherapy, especially leukopenia, impact patients' ability to tolerate their treatments and affect their quality of life. Traditional Chinese medicine is thought to provide complementary cancer treatment to improve the quality of life and prolong survival time among patients with cancer.

OBJECTIVE

This study aims to evaluate the effectiveness of Chinese herbal medicine (CHM) as a complementary treatment for neutropenia prevention and immunity modulation during chemotherapy in patients with breast cancer.

METHODS

We will conduct a real-world pragmatic clinical trial to evaluate the effectiveness of CHM as a supplementary therapy to prevent neutropenia in patients with breast cancer undergoing chemotherapy. Patients will be classified into CHM or non-CHM groups based on whether they received CHM during chemotherapy. Using generalized estimating equations or repeated measures ANOVA, we will assess differences in white blood cell counts, absolute neutrophil counts, immune cells, and programmed cell death protein 1 (PD-1) expression levels between the 2 groups.

RESULTS

This study was approved by the research ethics committee of Hualien Tzu Chi Hospital (IRB 110-168-A). The enrollment process began in September 2021 and will stop in December 2024. A total of 140 patients will be recruited. Data cleaning and analysis are expected to finish in the middle of 2025.

CONCLUSIONS

Traditional Chinese medicine is the most commonly used complementary medicine, and it has been reported to significantly alleviate chemotherapy-related side effects. This study's findings may contribute to developing effective interventions targeting chemotherapy-related neutropenia among patients with breast cancer in clinical practice.

TRIAL REGISTRATION

International Traditional Medicine Clinical Trial Registry ITMCTR2023000054; https://tinyurl.com/yc353hes.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/55662.

Effects and core patterns of Chinese herbal medicines on hematologic manifestations in systemic lupus erythematosus: A systematic review and meta-analysis

OBJECTIVE

This systematic review and meta-analysis of randomized controlled trials (RCTs) aimed to evaluate the effects of Chinese herbal medicines (CHMs) on hematologic manifestations in patients with systemic lupus erythematosus (SLE).

DATA SOURCES

PubMed, Embase, Cochrane Central Register of Controlled Trials, China National Knowledge Infrastructure, and Airiti Library were searched for the period January 2000 to February 2022.

STUDY SELECTION

RCTs involving CHMs in patients with SLE with available hematologic data.

DATA EXTRACTION

The primary outcomes included white blood cell (WBC) count, hemoglobin level, and platelet count. The Cochrane risk of bias tool was used to assess the quality of the included RCTs. Sensitivity analysis of RCTs with abnormal hematologic data before intervention was performed to verify the robustness of the results. Subgroup analysis was also applied for results with high heterogenicity. Core patterns of used herbal drug pairs had also been analyzed and visualized.

DATA SYNTHESIS

Fifteen RCTs involving 1183 participants were included. The effects of elevating WBC count (weighted mean difference [WMD]: 0.69; 95% confidence interval [CI]: 0.33-1.06; p <0.001), hemoglobin levels (WMD: 0.64; 95% CI: 0.31-0.97; p <0.001), and platelet count (WMD: 0.61; 95% CI: 0.48-0.74; p <0.001) in the CHM group were significantly greater than those in the control group. In total, 23 single herbs and 152 herbal drug pairs were identified for core patterns network analysis.

CONCLUSIONS

We demonstrated significantly superior therapeutic effects achieved with CHMs and conventional therapy regarding leukopenia, anemia, and thrombocytopenia compared to that of conventional therapy alone in patients with SLE.

Lower risk of ischemic stroke among patients with chronic kidney disease using chinese herbal medicine as add-on therapy: A real-world nationwide cohort study

Background: The incidence of ischemic stroke (IS) is much higher among patients with chronic kidney disease (CKD) compared to the general population. Few studies have evaluated the association between the risk of IS and the use of Chinese herbal medicine (CHM) in patients with CKD. We aimed to investigate the risk of IS among patients with CKD using CHM as add-on therapy.

Methods: We conducted a retrospective cohort study based on Taiwan’s National Health Insurance Research Database to assess 21,641 patients with newly diagnosed CKD between 2003 and 2012. Patients were classified as either the CHM (n = 3,149) or the non-CHM group (n = 3,149) based on whether they used CHM after first diagnosis of CKD. We used the proportional subdistribution hazards model of Fine and Gray to examine the hazard ratio (HR) of IS in propensity-score matched samples at a ratio of 1:1 for two groups.

Results: The risk of IS was significantly reduced in the CHM group (adjusted HR [aHR]: 0.58, 95% confidence interval [CI]: 0.48–0.70) compared with the non-CHM group. Those who used CHM for &gt;180 days had an even lower risk of IS than those in the non-CHM group (aHR: 0.51, 95% CI: 0.41–0.63). Additionally, frequently prescribed formulae, such as Ji-Sheng-Shen-Qi-Wan, Liu-Wei-Di-Huang-Wan, and Zhen-Wu-Tang were associated with a 30%–50% reduced risk of IS.

Conclusion: Our results suggest that patients with CKD who used CHM as add-on therapy had a lower hazard of IS than those in the non-CHM group, especially for patients taking CHM for &gt;180 days. Further experimental studies are required to clarify the causal relationship.

Chinese Herbal Medicines Have Potentially Beneficial Effects on the Perinatal Outcomes of Pregnant Women

Introduction: Tocolytic treatment is beneficial to pregnant women with a risk of premature labor or miscarriage. However, previous reports have shown that progestogen might not be effective and ritodrine may increase the risk of maternal vascular-related diseases. Chinese herbal products (CHP) are used as alternative therapies for pregnant women. The goal was to evaluate the efficacy of combined tocolytic therapy and CHP therapy in pregnancy outcomes for pregnant women in Taiwan.

Materials and Methods: We conducted a retrospective cohort study based on the National Health Insurance Research Database. A total of 47,153 pregnant women treated with tocolytics aged 18–50 years from 2001 to 2015 were selected from two million random samples. According to the medical use of tocolytics and CHP, we divided the users into two groups: western medicine (WM) only (n = 40,961) and WM/CHP (n = 6,192) groups. A propensity score (PS)-matched cohort (6,192 pairs) was established based on baseline confounders. All participants were followed up to perinatal outcomes. Conditional logistic regression analysis was used to examine the effects of CHP use on the odds of miscarriage and preterm birth.

Results: The adjusted odds ratio (OR) for premature birth in the WM/CHP group (n = 411, 6.64%) was significantly lower than in the WM group (n = 471, 7,61%) (0,86, 95% confidence interval [CI], 0.74–0.99). Further subgroup analysis based on the usage of formulae that activate blood and remove stasis or purgative formulae, the adjusted OR of preterm birth of those using these formulae was significantly lower in the WM/CHP group (n = 215, 6.32%) than that in the WM group (n = 265, 7.77%) (OR: 0.79, 95% CI: 0.65–0.96).

Conclusion: We found that the combination of CHP and tocolytics can be beneficial to pregnant women in the prevention of premature birth. Further research is required to investigate causal relationships.

Prescription patterns and factors influencing the use of Chinese herbal medicine among pregnant women in Taiwan: a population-based retrospective study

BACKGROUND

The use of Chinese herbal medicine (CHM) has been widely promoted as a natural and safe way to treat illness during pregnancy. However, prescription patterns and factors influencing its use are largely unknown. Therefore, we conducted a population-based study to address these questions.

METHODS

Pregnant women aged 18-50 years were selected from Taiwan's National Health Insurance Research Database between 2001 to 2011. CHM prescriptions and diagnostic records were collected. Demographic data and pre-existing diseases were compared between CHM users and non-users. A multivariate logistic regression analysis was performed to identify possible factors influencing the use of CHM during pregnancy.

RESULTS

A total of 81,873 eligible prescription records were identified, and 16,553 pregnant women were prescribed CHM during pregnancy, yielding a CHM prescription rate of 20.2%. The three most frequently used herbs were Scutellariae Radix (Huang Qin) (4.4%), Eucommiae cortex (Du Zhong) (2.5%), and Atractylodes Rhizome (Bai Zhu) (2.4%). The most frequently used herbal formulae were Dang-Guei-Shao-Yao-San (4.1%), Jia-Wei-Xiao-Yao-San (3.5%), and Xiang-Sha-Liu-Jun-Zi-Tang (2.6%). Multivariate logistic regression revealed that subjects with an older age, a university education, a pre-pregnancy history of CHM use, asthma, chronic renal disease, and cardiac valvular disease and living in a residential area other than northern Taiwan had an increase in adjusted odds ratio for CHM use during pregnancy.

CONCLUSIONS

In this population-based study, we found that demographic factors and pre-existing diseases were associated with the use of CHM among pregnant women. It is worth noting that Leonuri Herba (Yi Mu Cao) and Shao-Fu-Zhu-Yu-Tang should be used with caution in the first trimester. Further research is needed to explore the safety and effectiveness of the use of CHM in pregnant women.

The risk of coronary artery disease in patients with rheumatoid arthritis using Chinese herbal products and conventional medicine in parallel: a population-based cohort study

Background

Few studies have evaluated the association between the risk of coronary artery disease (CAD) and the use of Chinese herbal products (CHP) in patients with rheumatoid arthritis (RA). This study investigated the risk of CAD among patients with RA using CHP in combination with conventional medicine.

Methods

A retrospective cohort study was conducted using the Taiwan National Insurance Research Database to assess 22,353 patients who had been newly diagnosed with RA between 1997 and 2010. Patients were assigned to the CHP group or non-CHP group according to their use or nonuse of CHP after being diagnosed with RA. The Cox proportional hazards model was used to estimate the hazard ratio (HR) of CAD for a 1:1 matched sample.

Results

Both the CHP and non-CHP groups comprised 4889 patients after 1:1 matching. The risk of CAD was significantly reduced in the CHP group [adjusted HR (aHR): 0.59, 95% confidence interval (CI): 0.50–0.71] compard with the non-CHP group. Those who used CHP for > 180 days had an even lower risk of CAD than users with CHP usage less than 30 days (aHR: 0.64, 95% CI: 0.43–0.95). Additionally, frequently prescribed formulae, such as Kuei-Chih-Shao-Yao-Chih-Mu-Tang, Tang-Kuei-Nien-Tung-Tang, and Shu-Ching-Huo-Hsieh-Tang, were associated with a reduced risk of CAD.

Conclusion

The use of CHP was associated with a lower risk of CAD in patients with RA. Additional randomized controlled trials are required to assess any causal relationship between the effect of CHP usage and the risk of CAD.

Adjunctive Chinese Herbal Products Therapy Reduces the Risk of Ischemic Stroke Among Patients With Rheumatoid Arthritis

We performed a retrospective cohort study to investigate the association between the risk of ischemic stroke (IS) and the use of Chinese herbal products (CHP) in combination with western medicine (WM) among patients with rheumatoid arthritis (RA). The data were sourced from the registry for beneficiaries, inpatient and ambulatory care claims, and Registry for Catastrophic Illness from the National Health Insurance Research Database (NHIRD) in Taiwan between 1997 and 2011. Patients, who were newly diagnosed with RA between 1997 and 2010, were classified as the CHP group or non-CHP group depending on the presence of absence the adjunctive use of CHP following a diagnosis of RA. A total of 4,148 RA patients were in both the CHP and non-CHP groups after 1:1 matching. Patients in the CHP group had a significantly lower risk of IS compared to patients in the non-CHP group (adjusted hazard ratio [aHR], 0.67; 95% confidence interval [CI], 0.52-0.86). In the CHP group, patients who used CHP for more than 30 days had a lower risk of IS than their counterparts (aHR: 0.61, 95% CI: 0.40-0.91). Gui-Zhi-Shao-Yao-Zhi-Mu-Tang, Shu-Jin-Huo-Xie-Tang, and Du-Huo-Ji-Sheng-Tang might be associated with a lower risk of IS. Finally, the use of CHP in combination with WM was associated with a decreased risk of IS in patients with RA, especially among those who had used CHP for more than 30 days. A further randomized control trial is required to clarify the casual relationship between these results.

Effect of early use of Chinese herbal products on mortality rate in patients with lung cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Patients with lung cancer are frequently treated with Western medical treatments. Recently, patients have begun to use Chinese medicine to strengthen the immune system and alleviate side effects.

AIM OF THE STUDY

We aimed to evaluate the association between mortality rate and early use of Chinese herbal products (CHPs) among patients with lung cancer.

MATERIALS AND METHODS

We conducted a retrospective cohort study based on the National Health Insurance Research Database, Taiwan Cancer Registry, and Cause of Death Data. Patients with newly diagnosed lung cancer between 2002 and 2010 were classified as either the CHP (n = 422) or the non-CHP group (n = 2828) based on whether they used CHP within 3 months after first diagnosis of lung cancer. A robust Cox regression model was used to examine the hazard ratio (HR) of death for propensity score (PS) matching samples.

RESULTS

After PS matching, average survival time of the CHP group was significantly longer than that of the non-CHP group. The adjusted HR (0.82; 95% CI: 0.73-0.92) in the CHP group was lower than the non-CHP group. Stratified by clinical cancer stages, CHP group had longer survival time in stage 3 subgroup. When the exposure period of CHP use was changed from 3 to 6 months, results remained similar (HR = 0.85; 95% CI: 0.76-0.95).

CONCLUSION

Results indicated that patients with lung cancer who used CHP within 3 months after first diagnosis had a lower hazard of death than non-CHP users, especially for stage 3 lung cancer. Further experimental studies are needed to examine the causal relationship.

4-(1,3-Dimethoxyprop-2-ylamino)-2,7-dimethyl-8-(2, 4-dichlorophenyl)pyrazolo[1,5-a]-1,3,5-triazine: a potent, orally bioavailable CRF(1) receptor antagonist

Structure-activity studies in the pyrazolo[1,5-a]-1,3,5-triazine series led to the discovery that compound 11i (DMP696) is a potent hCRF(1) receptor antagonist (K(i) = 1.7 nM vs 7.5 nM for alpha-hel-CRF(9-41), hCRF(1) adenylate cyclase IC(50) = 82 nM vs 286 nM for alpha-hel-CRF(9-41)). Compound 11i has excellent oral pharmacokinetic profiles in rats and dogs (37% and 50% oral bioavailabilities, respectively). This compound displays good activity in the rat situational anxiety model (MED = 3 mg/kg (po)), whereas a literature standard 1 (CP154526-1) was inactive (MED > 30 mg/kg (po)). Analogue 11i reduced stereotypical mouth movements in rhesus monkeys by 50% at 21 mg/kg (po) using the human intruder paradigm. Overall, the profile of pyrazolotriazine 11i indicates that hCRF(1) receptor antagonists may be anxiolytic agents, which have reduced motor side effect profiles.

The discovery of 4-(3-pentylamino)-2,7-dimethyl-8-(2-methyl-4-methoxyphenyl)-pyrazolo-[1 ,5-a]-pyrimidine: a corticotropin-releasing factor (hCRF1) antagonist

Structure activity relationship studies led to the discovery of 4-(3-pentylamino)-2,7-dimethyl-8-(2-methyl-4-methoxyphenyl)-pyrazo lo-[1,5-a]-pyrimidine 11-31 (DMP904), whose pharmacological profile strongly supports the hypothesis that hCRF1 antagonists may be potent anxiolytic drugs. Compound 11-31 (hCRF1 Ki = 1.0+/-0.2 nM (n = 8)) was a potent antagonist of hCRF1-coupled adenylate cyclase activity in HEK293 cells (IC50= 10.0+/-0.01 nM versus 10 nM r/hCRF, n = 8); alpha-helical CRF(9-41) had weaker potency (IC50 = 286+/-63 nM, n = 3). Analogue 11-31 had good oral activity in the rat situational anxiety test; the minimum effective dose for 11-31 was 0.3 mg/kg (po). Maximal efficacy (approximately 57% reduction in latency time in the dark compartment) was observed at this dose. Chlordiazepoxide caused a 72% reduction in latency at 20 mg/kg (po). The literature compound 1 (CP154526-1, 30 mg/kg (po)) was inactive in this test. Compound 11-31 did not inhibit open-field locomotor activity at 10, 30, and 100 mg/kg (po) in rats. In beagle dogs, this compound (5 mg/kg, iv, po) afforded good plasma levels. The key iv pharmacokinetic parameters were t1/2, CL and Vd,ss values equal to 46.4+/-7.6 h. 0.49+/-0.08 L/kg/h and 23.0+/-4.2 L/kg, respectively. After oral dosing, the mean Cmax, Tmax t1/2 and bioavailability values were equal to 1260+/-290 nM, 0.75+/-0.25 h. 45.1+/-10.2 h and 33.1%, respectively. The overall rat behavioral profile of this compound suggests that it may be an anxiolytic drug with a low motor side effect liability.

Protein binding of brequinar in the plasma of healthy donors and cancer patients and analysis of the relationship between protein binding and pharmacokinetics in cancer patients

The protein binding of weakly acidic and basic drugs has been shown to be altered in cancer patients. Brequinar is a weakly acidic, low-clearance, and highly protein-bound (> 98% bound) antitumor agent. The pharmacokinetic parameters of brequinar are subject to large interpatient variability. This large interpatient variability may be related to brequinar's plasma protein-binding capacity (assuming no change in the intrinsic clearance of the unbound drug). The objectives of this study, therefore, were (a) to characterize brequinar's protein binding in the plasma of healthy donors and cancer patients and (b) to examine the relationships between brequinar's plasma protein binding and its pharmacokinetics in patients. Brequinar protein binding was determined in human serum albumin (HSA) solution, drug-free donor plasma, and brequinar-free, predose plasma samples obtained from a phase I cancer trial. Pharmacokinetic results from this study were used to examine relationships between plasma protein binding and drug disposition. In HSA solution and healthy donor plasma, brequinar's protein binding as determined using spiked samples was concentration-dependent. The unbound brequinar fraction increased by a factor of 3 (from 0.3% to 0.9% free) in 4% HSA solution and by a factor of 4 (from 0.4% to 1.6% free) in donor plasma as the brequinar concentrations increased from 0.1 to 2.3 mM in the HSA solution and from 0.076 to 1.5 mM in the donor plasma. Analysis of brequinar binding characteristics using the binding ratio and Rosenthal binding plots showed that albumin was the primary protein for brequinar binding in human plasma. The addition of various concentrations of alpha 1-acid glycoprotein to 4% HSA solution did not affect the protein binding of brequinar to HSA. The protein binding determined in the plasma of cancer patients was not quantitatively different, except for variability, from that observed in the plasma of healthy donors. Examination of relationships between the unbound brequinar fraction and pharmacokinetics suggested that plasma protein binding was not a major determinant of brequinar disposition in cancer patients.

Phase I and pharmacokinetic study of brequinar sodium (NSC 368390)

Brequinar sodium is a quinoline carboxylic acid derivative that has shown antitumor activity in a number of in vivo murine and human tumor xenograft models. Its mechanism of action is blockade of de novo pyrimidine biosynthesis by inhibition of dihydroorotic acid dehydrogenase. In vitro and in vivo studies demonstrate the superiority of prolonged drug exposure in achieving tumor growth inhibition. This phase I study evaluated the administration of brequinar sodium by short, daily i.v. infusion for 5 days repeated every 4 weeks. Fifty-four subjects were enrolled in the study and received drug in doses ranging from 36-300 mg/m2. The dose-limiting toxicities were mucositis and diffuse skin rash. Other toxicities included myelosuppression, nausea, vomiting, malaise, and burning at the infusion site. The maximum tolerated dose on the "daily times 5" schedule was 300 mg/m2. The recommended phase II dose is 250 mg/m2. Pharmacokinetic analysis of the day 1 drug clearance curves in 51 subjects showed slight nonlinearity in the relationship between dose and area under the clearance curve (AUC). The dose versus AUC relationship was well described using a Michaelis-Menten model of brequinar elimination kinetics with Vmax = 45 (micrograms/ml)/h and Km = 123 micrograms. Analysis of the day 5 drug clearance curves revealed a diminution in Vmax to 30 (micrograms/ml)/h. As a consequence of the reduction in Vmax brequinar plasma concentrations on day 5 were higher than predicted from day 1 drug kinetics. Pharmacodynamic analysis of the day 1 kinetic parameters and the toxicities occurring during the first cycle of drug therapy revealed significant correlations between mucositis and dose, AUC, and peak brequinar concentration; between leukopenia and AUC and peak drug concentration; and between thrombocytopenia and beta elimination rate.

Determination of unlabeled and 13C6-labeled moricizine in human plasma using thermospray liquid chromatography-mass spectrometry

Moricizine hydrochloride is an orally effective antiarrhythmic agent currently marketed in the Soviet Union and undergoing clinical testing in the United States. To facilitate the simultaneous analysis of unlabeled and 13C6-labeled moricizine in human plasma, a specific and sensitive method employing liquid-liquid extraction followed by thermospray liquid chromatography-mass spectrometry (LC-MS) was developed. Plasma samples, after addition of [2H11]moricizine as an internal standard, were extracted into methylene chloride under alkaline conditions. Extracts were evaporated, reconstituted with mobile phase, and chromatographed on an ODS column. The LC mobile phase consisted of methanol-0.1 M ammonium acetate containing 0.2% triethylamine (65:35) and it was used at a flow-rate of 1.5 ml/min. Under these conditions, moricizine and [13C6]moricizine coeluted at 1.2 min, while [2H11]moricizine eluted slightly earlier. The MS system consisted of a Finnigan 4600 TSQ and a Vestec thermospray interface. Selected ions at m/z 428, 434, and 439 were scanned at 0.2 s per ion. Over a plasma concentration range of 10-800 ng/ml, intra-day precision (n = 3) ranged from 1.8 to 13.3% and intra-day accuracy ranged from 1.9 to 15.8%. This method was successfully used to assay human plasma samples from a pilot moricizine bioavailability study in which tablets and solution containing moricizine hydrochloride and [13C6]moricizine, respectively, were simultaneously administered.

Phase I clinical and pharmacokinetic trial of Brequinar sodium (DuP 785; NSC 368390)

Brequinar sodium is a 4-quinolinecarboxylic acid analogue that inhibits dihydroorotate dehydrogenase and subsequent de novo pyrimidine biosynthesis. It has shown dose-dependent antineoplastic activity against several mouse and human tumor models. This trial evaluated Brequinar given as a single daily i.v. bolus over a 5-day period repeated every 28 days. One hundred seven courses of treatment at dosages ranging from 36 to 300 mg/m2/day x 5 were administered to 45 patients (31 male and 14 female) with refractory solid tumors; median age was 58 years (range 30-74); median Southwest Oncology Group performance status was 1 (range, 0-3). Thirty patients had prior cytotoxic chemotherapy. Dose-limiting toxicities were thrombocytopenia and a severe desquamative maculopapular dermatitis. Two of 5 good risk patients at 300 mg/m2 and 3 of 6 poor risk patients at 170 mg/m2 developed a platelet count less than 25 x 10(3)/microliters. Two of 5 good risk patients at 300 mg/m2 and 1 of 6 poor risk patients at 170 mg/m2 developed a severe desquamative dermatitis. Moderate to severe mucositis was usually associated with the thrombocytopenia and/or the dermatitis. Nonhematological drug-related toxicities included nausea and vomiting, malaise, anorexia, diarrhea, phlebitis, reversible transaminase elevation, and mucositis. Other hematological toxicities were anemia, granulocytopenia, and leukopenia. There were no drug-related deaths. There were no objective tumor responses. Plasma and urine levels of Brequinar were quantified by high pressure liquid chromatography in 28 patients. Plasma levels and areas under the curve increased proportionally with increased dose. Brequinar had a harmonic mean terminal t1/2 of 8.1 +/- 3.6 h with a model-independent determined apparent volume of distribution at steady state of 9.0 +/- 2.9 liters/m2 and a total body clearance of 19.2 +/- 7.7 ml/min/m2. Renal excretion was a minor route of elimination for Brequinar. The maximally tolerated dose of Brequinar on a daily x 5 i.v. schedule was 250 mg/m2 for good risk patients. For the daily x 5 i.v. schedule, the recommended dose of Brequinar for phase II evaluation is 250 mg/m2 for good risk patients and 135 mg/m2 for poor risk patients.

Distribution of the novel anticancer drug candidate Brequinar sodium (DuP 785, NSC 368390) into normal and tumor tissues of nude mice bearing human colon carcinoma xenografts

The distribution of the novel anticancer drug candidate Brequinar Sodium (DuP 785, NSC 368390) was studied in control mice and mice implanted subcutaneously with human colon carcinoma xenografts. Mice were given radiolabeled 14C-Brequinar Sodium intravenously. Brequinar concentrations in blood and various tissues were determined at 1, 6, and 24 h after drug administration. Within 1 h Brequinar distributed to the tumor and all other tissues studied. The tumor-to-blood drug concentration ratios ranged from 0.19 to 0.41. Radioactivity in the liver and small intestine at 1 h accounted for 17% and 13%, respectively, of the dose given. Elimination rates of Brequinar from all tissues were approximately equal to that from blood. Comparison of blood concentrations determined by both radioactivity and HPLC methods suggests that the intact drug is probably the only form in the blood.