Self-assembled micelles based on gambogenic acid-phospholipid complex for sustained-release drug delivery.

Objective: To improve the water solubility and enhance the oral bioavailability of gambogenic acid (GNA). Methods: GNA-phospholipid complex (GNA-PLC) micelles were successfully prepared by anti-solvent method. Results: The encapsulation efficiency of GNA-PLC micelles can reach 99.33 % (w/w). The average particle size of the GNA-PLC micelles was 291.23 nm which was approximate agreed with the transmission electron microscopy (TEM). In vitro release profile showed the GNA-PLC and GNA-PLC micelles have significant sustained-release of GNA compared with crude GNA. Pharmacokinetic parameters indicated that the area under concentration-time curve (AUC0→t) of GNA in cases of GNA-PLC and GNA-PLC micelles are 2.04- and 3.92-fold higher than crude GNA, respectively. Conclusions: The better water solubility and higher bioavailability of GNA in GNA-PLC micelles with significant sustained-release of GNA endow the nanoparticle with great potential in GNA delivery system.

Anticancer activity and underlying mechanism of neogambogic acid.

Garcinia, a kind of dry resin secreted by Garcinia hanburyi Hook. F. G., is a traditional Chinese medicine with various biological functions such as detoxification, anti-inflammatory, and anthelmintic activities. Recent studies suggest that garcinia has potential anticancer activity. Increasing evidences indicate that the main active monomer gambogic acid isolated from garcinia can inhibit the growth of various cancer cells. Neogambogic acid is an isolated compound with a similar chemical structure as gambogic acid. Preliminary studies show that the neogambogic acid can selectively inhibit the growth of various cancer cells, and has a broader antitumor activity and lower toxicity than gambogic acid. In this review, we summarize the advances made in the investigation of the anti-tumor effect of neogambogic acid in recent years.

Pharmacokinetics of mangiferin and its metabolite-Norathyriol, Part 1: Systemic evaluation of hepatic first-pass effect in vitro and in vivo.

Mangiferin (MGF), a glucoside of xanthone existing in phytomedicines and food, is increasingly attracting attention on diabetes treatment, while the underlying mechanism leading to its low oral bioavailability is unclear. Norathyriol (NTR), an active metabolite with hypoglycemic activity and its exposure after MGF dosing remains unclear. Hence, a rapid and sensitive LC-MS/MS method was established and validated to determine MGF and NTR and applied in the PK study in rats. Correspondingly, the in vitro experiments on temperature-dependent uptake, and MGF metabolism in hepatocyte and enterobacteria samples were performed. Results revealed that hepatic first-pass effect slightly contributed to the poor bioavailability of MGF, based on the MGF exposure in portal vein plasma was nearly similar to that in systemic plasma, and the MGF accumulation in the liver was limited, so was that of NTR. Correspondingly, the in vitro study revealed the MGF uptake was mainly dependent on poor passive transport, possibly leading to its limited hepatic metabolism and accumulation. Moreover, the NTR exposure remained considerably low (Cmax < 3 ng/mL, AUCNTR /AUCMGF < 3%) in plasma after single MGF dosing, corresponding to its tiny proportion (0.1%) of MGF in MGF-incubated enterobacteria samples. However, given the low generation and elimination rates of NTR, NTR might accumulate in plasma and exert effects after repeated MGF dosing, although requires further study. This work is the first systemic study on PK profiles of MGF and NTR in vitro and in vivo, which is important for the interpretation on the poor bioavailability and pharmacodynamics of MGF. © 2016 BioFactors, 42(5):533-544, 2016.

Pharmacokinetics of mangiferin and its metabolite-norathyriol, Part 2: Influence of UGT, CYP450, P-gp, and enterobacteria and the potential interaction in Rhizoma Anemarrhenae decoction with timosaponin B2 as the major contributor.

The poor bioavailability of mangiferin (MGF) is a major obstacle on its further development. Aimed to illustrate the underlying mechanism and improve its poor exposure, the compared PK profiles of MGF and norathyriol (NTR) after different MGF preparation were performed: pure MGF, the Rhizoma Anemarrhenae (Zhi-mu) decoction, MGF, and timosaponin B2 (TB-2) combination. Furthermore, the potential contributing factors, including uridine diphosphoglucuronosyltransferase (UGT), cytochrome P450 (CYP450), P-gp, and enterobacterial were investigated by comparing the PK profiles with and without the corresponding inhibitors or in different rat models. After taking MGF, CYP450 and UGT inhibition could decrease MGF and NTR exposure; P-gp inhibition slightly enhanced (48%) MGF exposure, whereas more apparent for the improved NTR exposure (302%); enterobacterial inhibition almost completely stopped the NTR production, but no such effect was observed for MGF. Compared with the limited improvement by the abovementioned inhibition, the MGF and NTR exposure could significantly increase by 11.5- and 5.9-fold in the Zhi-mu decoction compared with the MGF treatment, probably contributed to TB-2 as an absorption enhancer because the MGF and TB-2 combination produced a similar level of improvement on the PK paremeters of MGF and NTR to the herb treatment. Likewise, most of the effects by UGT, CYP450, P-gp, and enterobacteria followed a similar variation tendency between them. Therefore, the poor bioavailability of MGF possibly mainly attributed to its poor membrane permeability, but not transporters or metabolic enzymes, and the compatibility of MGF and TB-2 could probably expand the prospective application of MGF by improving its bioavailability. © 2016 BioFactors, 42(5):545-555, 2016.

Simultaneous determination and pharmacokinetic study of gambogic acid and gambogenic acid in rat plasma after oral administration of Garcinia hanburyi extracts by LC-MS/MS.

Gambogic acid and gambogenic acid are two major bioactive components of Garcinia hanburyi, and play a pivotal role in biologic activity. In this study, a specific and sensitive liquid chromatography-tandem mass spectrometry was developed and validated for simultaneous determination of gambogic acid and gambogenic acid in rat plasma. Chromatographic separation was achieved on a C18 column using an isocratic elution with methanol-10 m m ammonium acetate buffer-acetic acid (90:10:0.1, v/v/v) as the mobile phase. The detection was performed on a triple-quadrupole tandem mass spectrometer equipped with electrospray positive ionization using multiple reaction monitoring modes. The transitions monitored were m/z 629.3 [M + H](+) → 573.2 for gambogic acid, m/z 631.2 [M + H](+) → 507.2 for gambogenic acid and m/z 444.2 [M + NH4 ](+) → 83.1 for IS. Linear calibration curves were obtained in the concentration range of 2.00-1000 ng/mL for gambogic acid and 0.500-250 ng/mL for gambogenic acid. The lower limits of quantification of gambogic acid and gambogenic acid in rat plasma were 2.00 and 0.500 ng/mL, respectively. The intra- and inter-day precision (RSD) values were <11.7% and accuracy (RE) was -10.6-12.4% at three QC levels for both analytes. The assay was successfully applied to evaluate pharmacokinetics behavior in rats after oral administration of Garcinia hanburyi extracts.

Pharmacokinetic Interaction of astragaloside IV with atractylenolide I and prim-O-glucosylcimifugin in male Sprague Dawley rats.

Astragaloside IV, atractylenolide I, and prim-O-glucosylcimifugin are main medicinal components of the traditional Chinese medicine prescription Yu-ping-feng which is composed of three herbs: Astragalus membranaceus, Atractylodes macrocephala, and Saposhnikovia divaricata. This study is aimed to assess the influence of atractylenolide I and prim-O-glucosylcimifugin on the pharmacokinetic profile of astragaloside IV so as to investigate the pharmacokinetic mechanisms of the Yu-ping-feng prescription. Fifteen Sprague Dawley rats were randomized to three groups; astragaloside IV, astragaloside IV plus atractylenolide I, and a combination of astragaloside IV, atractylenolide I, and prim-O-glucosylcimifugin were respectively administered to rats of these three groups via intragastric gavage. Serum samples were collected at different times after drug administration, and serum concentrations of astragaloside IV and atractylenolide I were simultaneously detected using HPLC-electrospray ionization-MS. Compared with administration of astragaloside IV alone, concentrations of astragaloside IV in the serum were significantly increased when it was given in combination with atractylenolide I or atractylenolide I+prim-O-glucosylcimifugin, with higher values for Cmax (p = 0.019 and p = 0.033 compared with astragaloside IV + atractylenolide I and astragaloside IV + atractylenolide I + prim-O-glucosylcimifugin groups, respectively) and AUC (p = 0.0052 and p = 0.0047 compared with astragaloside IV + atractylenolide I and astragaloside IV + atractylenolide I + prim-O-glucosylcimifugin groups, respectively). Improvement in mean oral Cmax and mean systemic serum exposure because of the pharmacokinetic interaction between astragaloside IV and atractylenolide I might explain the rationale for the use of multiple herbs in Yu-ping-feng and of combinations of A.membranaceus and A. macrocephala.

Comparative pharmacokinetics of prim-O-glucosylcimifugin and cimifugin by liquid chromatography-mass spectrometry after oral administration of Radix Saposhnikoviae extract, cimifugin monomer solution and prim-O-glucosylcimifugin monomer solution to rats.

A sensitive and reliable liquid chromatography-mass spectrometry method has been developed and validated for simultaneous determination of cimifugin and prim-O-glucosylcimifugin in rat plasma after oral administration of Radix Saposhnikoviae (RS) extract, prim-O-glucosylcimifugin monomer solution and cimifugin monomer solution. Plasma samples were pretreated by protein precipitation with acetonitrile containing the internal standards puerarin and daidzein. LC separation was achieved on a Zorbax SB-C(18) column (150 × 4.6 mm i.d., 5 µm) with 0.1% formic acid in water and methanol by isocratic elution. The detection was carried out in select-ion-monitoring mode with a positive electrospray ionization interface. The fully validated method was successfully applied to the pharmacokinetic study of the analytes in rats. A bimodal phenomenon appeared in the concentration-time curve of prim-O-glucosylcimifugin and cimifugin after oral administration of RS extract. Prim-O-glucosylcimifugin mainly transformed to cimifugin when it was absorbed into blood. Both absorption and elimination of cimifugin after oral administration of RS were longer than after administration of single cimifugin. The pharmacokinetic parameters (AUC(0-t) , AUC(0-∞) and t(1/2) ) of prim-O-glucosylcimifugin and cimifugin by giving cimifugin monomer solution, prim-O-glucosylcimifugin monomer solution and RS extract had significant differences (P < 0.05).

Trafficking of systemic fluorescent gentamicin into the cochlea and hair cells.

Aminoglycosides enter inner ear hair cells across their apical membranes via endocytosis, or through the mechanoelectrical transduction channels in vitro, suggesting that these drugs enter cochlear hair cells from endolymph to exert their cytotoxic effect. We used zebrafish to determine if fluorescently tagged gentamicin (GTTR) also enters hair cells via apically located calcium-sensitive cation channels and the cytotoxicity of GTTR to hair cells. We then examined the serum kinetics of GTTR following systemic injection in mice and which murine cochlear sites preferentially loaded with systemically administered GTTR over time by confocal microscopy. GTTR is taken up by, and is toxic to, wild-type zebrafish neuromast hair cells. Neuromast hair cell uptake of GTTR is attenuated by high concentrations of extracellular calcium or unconjugated gentamicin and is blocked in mariner mutant zebrafish, suggestive of entry via the apical mechanotransduction channel. In murine cochleae, GTTR is preferentially taken up by the stria vascularis compared to the spiral ligament, peaking 3 h after intra-peritoneal injection, following GTTR kinetics in serum. Strial marginal cells display greater intensity of GTTR fluorescence compared to intermediate and basal cells. Immunofluorescent detection of gentamicin in the cochlea also revealed widespread cellular labeling throughout the cochlea, with preferential labeling of marginal cells. Only GTTR fluorescence displayed increasing cytoplasmic intensity with increasing concentration, unlike the cytoplasmic intensity of fluorescence from immunolabeled gentamicin. These data suggest that systemically administered aminoglycosides are trafficked from strial capillaries into marginal cells and clear into endolymph. If so, this will facilitate electrophoretically driven aminoglycoside entry into hair cells from endolymph. Trans-strial trafficking of aminoglycosides from strial capillaries to marginal cells will be dependent on as-yet-unidentified mechanisms that convey these drugs across the intra-strial electrical barrier and into marginal cells.

Demethylbellidifolin preserves endothelial function by reduction of the endogenous nitric oxide synthase inhibitor level.

The present study examined the anti-oxidation and protective effects of demethylbellidifolin (DMB), a xanthone compound extracted from swertia davidi Franch, on endothelium. The relationship between the protective effects of DMB on endothelium and the level of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase, was also determined in the present study. DMB significantly inhibited Cu(2+)-induced low-density lipoprotein (LDL) oxidation and scavenged DPPH radicals. DMB significantly attenuated the inhibition of endothelium-dependent vasodilator responses, induced by lysophosphatidycholine (LPC) in vitro and LDL in vivo, and increased release of lactate dehydrogenase induced by LDL in cultured endothelial cells. DMB significantly attenuated the increased concentration of malondialdehyde and ADMA, and the decreased level of nitric oxide induced by LDL in vivo and in cultured endothelial cells. DMB also significantly reduced the decreased activity of dimethylarginine dimethylaminohydrolase (DDAH) induced by LDL in cultured endothelial cells. In summary, the present results suggest that DMB protects endothelial damage induced by LPC in vitro and LDL in vivo or in endothelial cells, and the protective effect of DMB on the endothelium is related to reduction of ADMA concentration via an increase of DDAH activity by inhibition of lipid peroxidation.

Demethylbellidifolin inhibits adhesion of monocytes to endothelial cells via reduction of tumor necrosis factor alpha and endogenous nitric oxide synthase inhibitor level.

The effect of demethylbellidifolin (DMB), a major compound of Swertia davidi Franch, on the adhesion of monocytes to endothelial cells induced by oxidized low-density lipoprotein (ox-LDL) was studied. Adhesion of monocytes to endothelial cells was induced by treatment with ox-LDL (100 microg/mL) for 48 h. Levels of tumor necrosis factor-alpha (TNF-alpha) and asymmetric dimethylarginine (ADMA, an endogenous inhibitor of NOS) in conditioned medium and the activity of dimethylarginine dimethylaminohydrolase (DDAH) in endothelial cells were measured. DMB (3 or 10 micromol/L) significantly inhibited the adhesion of monocytes to endothelial cells, attenuated an increase in levels of TNF-alpha and ADMA, and a decrease in the activity of DDAH by ox-LDL. The present results suggest that DMB inhibits the increased adhesion of monocytes to endothelial cells induced by ox-LDL, and that the effect of DMB is related to reduction of the ADMA concentration via reduction of TNF-alpha production in cultured endothelial cells treated with ox-LDL.

Differential activation of protein kinase C isoforms by euxanthone, revealed by an in vivo yeast phenotypic assay.

The protein kinase C (PKC) modulatory effects of euxanthone, isolated from the wood of Cratoxylum maingayi, on isoforms alpha, betaI, delta, eta and zeta were characterised using an alternative in vivo yeast phenotypic assay. The present study shows that euxanthone can activate isoforms alpha, betaI, delta, eta and zeta, being more effective on PKC-betaI, -delta, -eta and -zeta than the established PKC activators used (the phorbol ester PMA and arachidonic acid for PKC-zeta). Furthermore, euxanthone presents differences on its potency towards individual PKC isoforms, showing a remarkable selectivity for PKC-zeta. These results can help to clarify the molecular basis of the euxanthone-mediated effects.

Potentiation of the anti-tumour effect of hyperthermia by combining with the vascular targeting agent 5,6-dimethylxanthenone-4-acetic acid.

The potential of the vascular targeting agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA) to enhance the effect of hyperthermia was investigated in a C3H mouse mammary carcinoma grown in the feet of female CDF1 mice and in normal foot skin. DMXAA, when injected intraperitoneally in restrained non-anaesthetized animals, reduced tumour perfusion, as measured using the RbCl extraction procedure, and increased necrosis in histological section, but these effects were dependent on the drug dose and time interval. At a dose of 20 mg/kg, it significantly enhanced the thermal damage of this tumour, when given 1 h or more before the start of heating, as assessed by a tumour growth assay. This enhancement became larger with increasing interval between the two treatments. No thermo-potentiation was seen at doses of 10 mg/kg or lower. These combined effects seem to be associated with the tumour vascular shut-down by DMXAA. Thermal potentiation by DMXAA was also dependent on the heating temperature, with a greater enhancement relative to hyperthermia alone obtained at the lower temperatures at 40.5 and 41.5 degreesC than at the higher temperature of 42.5 degrees C. DMXAA (20 mg/kg) also enhanced the heat damage of normal skin, and this could not be explained by any DMXAA-induced TNF-alpha production. The heat enhancement-ratio by DMXAA was larger in tumours (1.9) than in normal skin (1.3-1.5), thus giving rise to a therapeutic gain.

Enhancement of antibody-directed enzyme prodrug therapy in colorectal xenografts by an antivascular agent.

The irregular nature of solid tumor vasculature produces a heterogeneous distribution of antibody-targeted therapies within the tumor mass, which frequently results in reduced therapeutic efficacy. We have, therefore, combined two complementary therapies: Antibody-directed Enzyme Prodrug Therapy (ADEPT), which targets tumor cells, and an agent that selectively destroys tumor vasculature. A single i.p. dose (27.5 mg/kg) of the drug 5,6-dimethylxanthenone-4-acetic acid (DMXAA), given to nude mice bearing the LS174T colorectal xenograft, destroyed all but a peripheral rim of tumor cells, without enhancing survival. The ADEPT system, in which a pretargeted enzyme activates a prodrug, consisted of the F(ab')2 fragment of anti-carcinoembryonic antigen antibody A5B7 conjugated to the bacterial enzyme carboxypeptidase G2 and the prodrug 4-[(2-chloroethyl)(2-mesyloxyethyl)amino]benzoyl-L-glutamic acid, which was given i.p. in three doses of 500 mg/kg at 72, 84, and 96 h post-conjugate administration (25 units of carboxypeptidase G2). The antibody-enzyme conjugate could be selectively retained at approximately twice the control levels by administration of the antivascular agent at the time of optimal conjugate localization within the tumor (20 h post-conjugate administration), as demonstrated by gamma counting, phosphor plate image analysis, and active enzyme measurement. This resulted in significantly enhanced tumor growth inhibition in groups of six mice, compared to conventional ADEPT therapy, with no concomitant increase in systemic toxicity. In a separate experiment, aimed at trapping the prodrug within the tumor, a 16-fold increase over control values was produced (means, 44.8 versus 2.8 microg/g tumor) when DMXAA was given 4 h prior to 4-[(2-chloroethyl)(2-mesyloxyethyl)amino]benzoyl-L-glutamic acid. The therapeutic window was small, with no significant enhancement of prodrug retention when DMXAA was given at either earlier or later time points. This correlated with the time of vascular shut-down induced by the antivascular agent. We are currently investigating whether it is more advantageous to trap increased levels of conjugate or prodrug within the tumor for maximal enhancement of conventional ADEPT. These studies demonstrate that combined use of antibody-directed and antivascular therapies can significantly benefit the therapeutic outcome of either strategy alone.

Controlled clinical trials of hypericum extracts in depressed patients--an overview.

In Germany, hypericum extracts are among the most widely prescribed antidepressants. Additionally, many preparations of St. John's wort are sold on the free market and one extract is even the best selling antidepressant in the country. In contrast to synthetic antidepressants, the approval procedures are not so strict, which implies that the pharmaceutical industry is not forced to conduct clinical trials suitable for licensing. Nevertheless, numerous studies on hypericum extracts including depressed patients have been published in the last 20 years. The purpose of this paper is to review these investigations in respect of methodological considerations and to draw conclusions pertaining to the proof of antidepressant efficacy. To this effect, a computer-assisted literature research was performed and manufacturers were asked to supply the author with study results. A total of 12 placebo-controlled trials with hypericum extracts were performed, mostly with positive results. Also in comparison with synthetic antidepressants (3 studies published), a similar reduction of depressive symptomatology was seen, although the comparators were not adequately dosed. No trials in severely depressed patients have been published yet. Since most studies on hypericum have methodological flaws, further studies are warranted.

[Reversible increase in photosensitivity to UV-B caused by St. John's wort extract]. / Reversible Erhöhung der Photosensitivität im UV-B-Bereich durch Johanniskrautextrakt-Präparate.

A 61-year-old woman with depression developed recurring elevated itching erythematous lesions in light-exposed areas after taking St. John's Wort-extract for three years. Routine patchtesting did not reveal any relevant reactions and photopatch testing was negative. Using a systemic oral photoprovocation test with St. John's Wort, we were able to demonstrate a decrease of the MED-UVB which was reversible after withdrawal of the medication.

Antinociceptive properties of the hydroalcoholic extract and preliminary study of a xanthone isolated from Polygala cyparissias (Polygalaceae).

Polygala cyparissias (Polygalaceae) grows abundantly on Brazil's Atlantic coast, belonging to the typical underbrush vegetation of dunes and have been used in folk medicine for treatment of several diseases, such as disturbances of bowel and kidney. The hydroalcoholic extract of P. cyparissias (HE, 3 to 60 mg kg(-1), i.p. or 25 to 200 mg kg(-1), p.o.) produced significant and graded inhibition of acetic acid-induced abdominal constrictions, with mean ID50 values of 6 and 72 mg kg(-1), respectively. The HE (at this same range of doses) also produced dose-related inhibition of both the early and the late phase of formalin-induced licking. The calculated mean ID50 values for the early phase were: >60 and >200 mg kg(-1), while for the late phase they were 11 and 101 mg kg(-1), respectively, by i.p. and p.o. routes. The HE also caused dose-related inhibition of formalin-induced edema formation (P<0.01). The HE (3 to 60 mg kg(-1), i.p. or 50 to 200 mg kg(-1), p.o.) produced significant and dose-related inhibition of the neurogenic nociception caused by topical injection of capsaicin, with mean ID50 values of 12 and 71 mg kg(-1), respectively. Given orally, the HE (50 to 200 mg kg(-1)) prevented in a dose-dependent manner, bradykinin (3 nmol/paw) and substance P (10 nmol/paw)-induced hyperalgesia in the rat paw, with mean ED50 values of 122 and 121 mg kg(-1), respectively, but was ineffective in the hot-plate model of nociception. The antinociception caused by the HE, in contrast to that of morphine (5 mg kg(-1), s.c.), was not reversed by naloxone (5 mg kg(-1), i.p.) when assessed in the acetic acid writhing test. The HE, at antinociceptive doses, did not affect motor coordination of animals when assessed in the rota-rod model. The xanthone isolated from P. cyparissias, identified as 1,7-dihydroxy-2,3-dimethoxy xanthone (0.3 to 30 mg kg(-1), i.p.), produced dose-related inhibition of acetic acid-induced abdominal constriction, with mean ID50 value of 1.5 mg kg(-1). These data show that the active principle(s) present in the HE of P. cyparissias, elicited pronounced antinociception when assessed by i.p. or p.o. routes, against both inflammatory and neurogenic nociception, and was able to prevent bradykinin and substance P-induced hyperalgesia. Its precise mechanism of action still remains unclear.

Central action of hyperici herba cum flore extractum siccum in freely moving rats.

The central action of a plant extract containing hyperici herba flore extractum siccum has been investigated in freely moving rats during a 6 h exposure with two dosages. After frequency analysis of local field potentials electrical power changes of delta waves and alpha2 waves (less pronounced) could be observed within the frontal cortex and hippocampus. As these frequencies are changed predominantly in the presence of drugs acting at the cholinergic or dopaminergic transmitter system, a similar mode of action can be suspected for this plant extract. Despite the fact that statistical significance could only be observed during the fourth hour (p <0.1), the changes induced by the higher dose of the extract containing 1 mg of hypericine were very stable from the 2. to 4. hour after oral application. Classification of the parameters obtained by means of discriminant analysis revealed a trend into the direction of antidepressive EEG drug profiles. Results suggest that quantitative EEG analysis is a very sensitive methodology for the description of pharmacodynamic actions of plant extracts and data can be compared to the action of pure chemical entities.

Ablation of colorectal xenografts with combined radioimmunotherapy and tumor blood flow-modifying agents.

Radioimmunotherapy (RIT) does not readily eradicate common solid tumors and therefore requires augmentation by complementary therapies that do not increase normal tissue damage. We have examined the efficacy of RIT combined with 5,6-dimethylxanthenone-4-acetic acid (DMXAA), a drug which induces immunomodulation and cytokine production and preferentially reduces tumor blood flow, using a colorectal xenograft model in nude mice. Although an optimal i.p. dose (27.5 mg/kg) of drug alone induced massive hemorrhagic necrosis of all but a thin peripheral rim of viable tumor cells, survival was unaffected. However, when combined with i.v. 18.5 MBq 131I-labeled anti-carcinoembryonic antigen IgG, DMXAA significantly potentiated the RIT without increased toxicity, with five of six mice showing complete cures. Scheduling was critical because the antibody must be allowed to reach maximum tumor accumulation before initiation of drug-induced blood flow inhibition. Subsequently, the antibody was retained preferentially in the tumor, reaching approximately twice control levels by 5 days after drug delivery. In combined studies, the drug had a narrow therapeutic window, 30 mg/kg being toxic to two of six mice, whereas 20 mg/kg were ineffective. However, the addition of a second vasoactive agent, serotonin, to RIT plus 20 mg/kg DMXAA enhanced therapy without increasing systemic toxicity. Tumor histology and phosphor image plate analysis reflected these results. When given without RIT, the two drugs combined, although not alone, also significantly inhibited tumor growth. Drug-induced tumor necrosis and tumor retention of radioantibody may both contribute to the enhanced RIT produced by this combined complementary therapy.