Intracavitary administration: pharmacokinetic advantages of macromolecular anticancer agents against peritoneal and pleural carcinomatoses

BACKGROUND

Pleural and peritoneal carcinomatoses are quite difficult to control in patients with advanced cancer. We have devised a suitable formulation of anticancer agents to be injected by the intracavitary route.

MATERIALS AND METHODS

The pharmacokinetics of macromolecular anticancer agent, copoly(styrene/maleic acid)-conjugated neocarzinostatin (smancs) and radiolabeled albumin were studied after intraperitoneal administration to ascitic tumor-bearing rats and mice, and were compared with the pharmacokinetics of other low-molecular-weight anticancer agents, mitomycin C (MMC) and doxorubicin (DOX).

RESULTS

Pharmacokinetic analyses indicated that smancs showed a much higher drug concentration for a longer time in the peritoneal cavity, and a much lower drug concentration in the blood circulation than did MMC or DOX. The cavity/blood ratios of the area under the concentration curve (AUC), of smancs, bovine serum albumin (BSA), DOX, and MMC were 9.69, 7.06, 1.38, 1.15, respectively.

CONCLUSION

These results suggest that macromolecular agents are cleared more slowly from the cavitary compartment and remain there at a high concentration while the blood concentration remains low.

Epstein-Barr virus-associated lymphoproliferative disorder after unrelated bone marrow transplantation in a young child with Wiskott-Aldrich syndrome

We report a case of a 16-month-old Wiskott-Aldrich syndrome (WAS) patient with a WASP gene mutation who received human leukocyte antigen (HLA)-matched, unrelated allogeneic bone marrow transplantation (BMT) followed by an Epstein-Barr virus-associated lymphoproliferative disorder (EB-LPD), diagnosed by clinical findings, polymerase chain reaction detection of the EB virus genome, and spontaneous lymphocyte proliferation of donor cell origin. EB-LPD is one of frequent lethal complications in HLA-mismatched or unrelated BMT in this syndrome. Adoptive immunotherapy with donor leukocyte transfusion, including appropriate numbers of CD3-positive T cells, was effective for the EB-LPD, achieving almost complete recovery 1 year later without any findings of graft-versus-host disease.

Tissue-specific involvement of multiple mitochondrial DNA deletions in familial mitochondrial myopathy

It is still uncertain how deleted mitochondrial DNA (mtDNA) is distributed to each tissue during development, although deletions of mtDNA have been extensively observed in various pathologic conditions. This paper presents two Japanese siblings with progressive external ophthalmoplegia exhibiting multiple mtDNA deletions. In one patient, similar multiple mtDNA deletions were found in skeletal muscle specimens as well as in the spinal cord but not in the myocardium, liver or leukocytes. A similar deletion pattern was found in the skeletal muscle but not in the leukocytes of the other patient. The results suggest the complex mechanism to generate, expand and eliminate the deleted mtDNA in humans.

A novel dosage approach for evaluation of SMANCS [poly-(styrene-co-maleyl-half-n-butylate) - neocarzinostatin] in the treatment of primary hepatocellular carcinoma

We report a Phase I/II clinical trial of poly-(styrene-co-maleyl-half-n-butylate)-neocarzinostatin (SMANCS) for intra-arterial treatment of hepatoma. Early patients received 4 or 8 mg SMANCS dissolved in Lipiodol; later patients were treated according to tumour size and degree of filling achieved. SMANCS/Lipiodol drained rapidly from normal liver but was retained within tumour interstitium. Tumour nodules filled with SMANCS/Lipiodol usually stabilised and often regressed. No UICC criteria-defined responses were achieved, partly due to difficulties of filling several lesions simultaneously. Signs of therapeutic activity suggest a more extensive clinical study is warranted.

Progression to moderate or severe mitral regurgitation after percutaneous transvenous mitral commissurotomy using stepwise inflation technique

Progression to moderate or severe mitral regurgitation (MR) was studied after Inoue balloon percutaneous transvenous mitral commissurotomy (PTMC) using the stepwise inflation technique, performed at increments of 1 mm of balloon diameter, in 49 consecutive patients with rheumatic mitral stenosis (aged from 32-73 years; 8 males, 41 females). The patients were classified on the basis of the degree of MR after PTMC, compared with that before PTMC, into either Group A, development of moderate or more severe (> or = grade 2) MR (n = 8) or Group B, no increase in MR or development of mild (grade 1) MR (n = 41). Progression to moderate or severe MR was significantly associated only with advanced age (60 +/- 8 vs 52 +/- 10 years, p < 0.05) and narrower mitral valve area (0.87 +/- 0.35 vs 1.11 +/- 0.29 cm2, p < 0.05), but other characteristics before PTMC were similar in both groups. There was no difference between the two groups in the total number and degree of balloon inflation. Immediately before the final inflation, the left atrial mean pressure and v wave pressure were decreased in smaller degrees in Group A compared with Group B (-2 +/- 2 vs -5 +/- 4 mmHg, p < 0.05; -2 +/- 2 vs -6 +/- 6 mmHg, p < 0.05, respectively). Thus, the stepwise inflations require careful monitoring of changes in the left atrial pressure and waveform to recognize the aggravation of MR, especially in older patients with severe stenosis. Patients who do not have a significant drop in left atrial mean pressure and v wave pressure during stepwise inflations of the balloon might be at risk of development of moderate or severe MR after further dilations.

Epstein-Barr virus-induced lymphoblastoid cell lines from patients with primary immunodeficiency diseases

Peripheral lymphocytes from eight patients with congenital immunodeficiency diseases were infected with Epstein-Barr virus (EBV) in an attempt to establish B lymphoblastoid cell lines (LCL). These patients included three boys with congenital agammaglobulinaemia, two girls with hypogammaglobulinaemia, one boy with common variable immunodeficiency, one boy with severe combined immunodeficiency with adenosine deaminase deficiency, and one boy with DiGeorge syndrome. Five of the patients bore no surface immunoglobulins (sIg) on their peripheral lymphocytes. LCL were established from seven of the eight patients. All the LCL established formed rosettes with EAC3 and had the ability to produce cytoplasmic immunoglobulins (cIg) of various classes. Culture supernatants concentrated up to 100-fold developed precipitin bands by Ouchterlony's method with antisera to human Ig in all the established LCL. These results suggested that both sIg-, cIg- and C3+ cells and sIg+, cIg- and C3+ cells might be the target cells for EBV and that sIg-, cIg- and C3+ cells might be the precursor cells of B lymphocytes.

Neonatal intrahepatic cholestasis with hepatic siderosis and steatosis

Neonatal intrahepatic cholestasis is a heterogeneous disease of undetermined cause. There is an unreported subset of idiopathic neonatal intrahepatic cholestasis with an unusual histological combination of hepatic siderosis and macrovesicular steatosis. The patients were a 34-day-old female and a 39-day-old male with normal birth weights. Their mothers had received oral iron supplement 4-6 weeks before delivery. The patients had obstructive jaundice noticed at the well-baby clinic at 1 month of life. They had high levels of serum galactose and tyrosine, hyperferritinemia. Urinary organic acid and bile acid analyses were negative, and galactose-1-phosphate uridyltransferase activity in red cells was normal. Liver biopsies showed diffuse iron deposits and macrovesicular fat. By substituting formula milk with lactose-free milk, the patients responded, and had normal biochemical tests within 5 months of life. Follow-up biopsies, at the age of 12 months, showed mild residual fibrosis without iron or fat deposits. They are both well at 3 and 6 years of age, respectively, without biochemical liver dysfunction and neurologic impairment. Prenatal iron-overload might contribute to the pathogenesis of the disease, but further studies are needed to confirm the assumption.

Prolonged secretion of IL-15 in patients with severe forms of acute graft-versus-host disease after allogeneic bone marrow transplantation in children

Graft-versus-host disease (GVHD) is one of the most common and fatal complications that follows allogeneic bone marrow transplantation (BMT). Donor origin T cells are responsible for the initiation of GVHD. In this report, we demonstrate that conditioning regimens for BMT resulted in elevated serum levels of interleukin-15 (IL-15), which reached maximum levels within 15 days and returned to basal levels within 25 days after allogeneic BMT, in all patients examined. Thereafter, circulating IL-15 was detected only in patients with grade III or IV acute GVHD with gut involvement. In contrast, IL-2 was not detected at any time in these patients. Since IL-15 is able to activate antigen-stimulated T cells and natural killer (NK) cells, IL-15 may play an important role in the development of severe forms of acute GVHD.

Conformational diversity of acid-denatured cytochrome c studied by a matrix analysis of far-UV CD spectra

The singular value decomposition (SVD) analysis was applied to a large set of far-ultraviolet circular dichroism (far-UV CD) spectra (100-400 spectra) of horse heart cytochrome c (cyt c). The spectra were collected at pH 1.7-5.0 in (NH4)2SO4, sorbitol and 2,2,2-trifluoroethanol (TFE) solutions. The present purpose is to develop a rigorous matrix method applied to far-UV CD spectra to resolve in details conformational properties of proteins in the non-native (or denatured) regions. The analysis established that three basis spectral components are contained in a data set of difference spectra (referred to the spectrum of the native state) used here. By a further matrix transformation, any observed spectrum could be decomposed into fractions of the native (N), the molten-globule (MG), the highly denatured (D), and the alcohol-induced helical (H) spectral forms. This method could determine fractional transition curves of each conformer as a function of solution conditions, which gave the results consistent with denaturation curves of cyt c monitored by other spectroscopic methods. The results in sorbitol solutions, for example, suggested that the preferential hydration effect of the co-solvent stabilizes the MG conformer of cyt c. This report has found that the systematic SVD analysis of the far-UV CD spectra is a powerful tool for the conformational analysis of the non-native species of a protein when it is suitably supplemented with other experimental methods.

The methanol-induced transition and the expanded helical conformation in hen lysozyme

Methanol-induced conformational transitions of hen egg white lysozyme were investigated with a combined use of far- and near-UV CD and NMR spectroscopies, ANS binding and small-angle X-ray scattering. Addition of methanol induced no global change in the native conformation itself, but induced a transition from the native state to the denatured state which was highly cooperative, as shown by the coincidence of transition curves monitored by the far- and near-UV CD spectroscopy, by isodichroic points in the far- and near-UV CD spectra and by the concomitant disappearance of individual 1H NMR signals of the native state. The ANS binding experiments could detect no intermediate conformer similar to the molten globule state in the process of the methanol denaturation. However, at high concentration of methanol, e.g., 60% (v/v) methanol/water, a highly helical state (H) was realized. The H state had a helical content much higher than the native state, monitored by far-UV CD spectroscopy, and had no specific tertiary structure, monitored both by near-UV CD and NMR spectroscopy. The radius of gyration in the H state, 24.9 angstroms, was significantly larger than that in the native state (15.7 angstroms). The Kratky plot for the H state did not show a clear peak and was quite similar to that for the urea-denatured state, indicating a complete lack of globularity. Thus we conclude that the H state has a considerably expanded, flexible broken rod-like conformation which is clearly distinguishable from the "molten globule" state. The stability of both N and H states depends on pH and methanol concentration. Thus a phase diagram involving N and H was constructed.

Detection of the PGP9.5 and tyrosine hydroxylase mRNAs for minimal residual neuroblastoma cells in bone marrow and peripheral blood

The "touchdown" polymerase chain reaction (PCR) technique has been applied to analyze expression of the neuron-specific protein, PGP9.5, and tyrosine hydroxylase (TH) genes for detection of minimal residual neuroblastoma cells in bone marrow and peripheral blood. PGP9.5 and TH gene products were not detected in any normal samples (n = 72) examined. However, in patients more than 1 year of age with stage III and IV neuroblastoma PGP9.5 mRNA was detected in six of seven bone marrow samples and in four of eight peripheral blood samples, and TH mRNA in four of seven and three of eight, respectively. The detection sensitivity was up to 10(-6) to 10(-7) micrograms of total cellular RNA for PGP9.5 and 10(-4) micrograms for TH. Among forty bone marrow specimens from nineteen patients with neuroblastoma both PGP9.5 and TH mRNAs were detected in six, and only PGP9.5 mRNA was detected in ten. Since detection of PGP9.5 and TH gene transcripts by the "touchdown" PCR was highly specific and sensitive, it might be most informative at present to carry out both PGP9.5 and TH mRNA assays for minimal residual neuroblastoma cells in blood and bone marrow.

Idiopathic neonatal hepatitis presenting as neonatal hepatic siderosis and steatosis

Idiopathic neonatal hepatitis (INH) is a heterogeneous disease of undetermined cause. We report a retrospective histologic reevaluation of INH. Sixty patients with INH were reviewed along with 32 biliary atresia (BA) patients. Histologic findings, iron and fat deposits, giant cell transformation, portal fibrosis, and bile duct proliferation were semiquantitatively graded from 0 to 4+. Significant histologic findings were defined as > or =2+. Frequencies of patients with significant histologic findings in the INH group were compared with those of the BA group. Among the patients with significant histologic findings, those in the INH group had significantly less iron deposits (P < 0.01), portal fibrosis (P < 0.01), and bile duct proliferation (P < 0.01) than those of the BA group. A combination of significant hepatic macrovesicular steatosis and siderosis was observed in 10 INH patients but not in any BA patient (10/60 vs 0/32, P < 0.05). Without extensive treatment, the 10 INH patients all recovered, and hepatic abnormalities normalized by the age of 12 months. In conclusion, the present study showed that the recognition of hepatic siderosis is helpful to distinguish BA from INH and that in a subset of INH patients hepatic macrovesicular steatosis and siderosis occurs.

[Targeted chemotherapy of hepatocellular carcinoma with SMANCS/Lipiodol--how to use SMANCS/Lipiodol]

The first drug only for arterial injection, SMANCS/Lipiodol, which offers targeted chemotherapy for hepatocellular carcinoma (HCC), now commercially available. Based on our experience using SMANCS/Lipiodol for 424 patients with HCC, the golden standard of how to use SMANCS/Lipiodol for complete necrosis of tumor was described. The initial dose of SMANCS/Lipiodol was varied 2 to 6 mg per body, mainly depending on the size of the tumor. All feeding arteries of HCC have to be verified on angiogram, and the drug must be injected via an adequate artery. Sometimes, a tumor changes its feeding arteries. Additional administrations with an interval of one month were done till the entire tumor was filled with SMANCS/Lipiodol (grade 4). One or two months after achievement of grade 4, we must examine how much drug was removed from tumor on CT. If the entire tumor is not filled with the drug, further injections are recommended to maintain grade 4. Almost all tumors shrank in 3 to 4 months while maintaining grade 4. Frequent administration of low doses (1-3 mg per body) is recommended. Discontinvation of administration was done on the following findings; tumor size reduction of over 90% or complete disappearance of tumor stain. With arterial injection therapy of SMANCS/Lipiodol, survival of patients with unresectable HCC was prolonged, especially in 272 patients who were good candidates for therapy. (Those with Child C liver cirrhosis, with a tumor occupying all four segments of the liver, and/or with extrahepatic spread at initial arterial injection of the drug were excluded.) The 1, 2, 5, and 10 year survival rates were 83%, 58%, 34%, and 25%, respectively.

Structural and functional roles of modules in hemoglobin. Substitution of module M4 in hemoglobin subunits

The alpha- and beta-subunits of human hemoglobin consist of the modules M1, M2 + M3, and M4, which correspond to the exons 1, 2, and 3, respectively (Go, M. (1981) Nature 291, 90-92). To gain further insight into functional and structural significance of the modules, we designed two kinds of chimeric hemoglobin subunits (chimeric alphaalphabeta- and betabetaalpha-subunits), in which the module M4 was replaced by the partner subunits. CD spectra in the far-UV region showed that the secondary structure of the chimeric alphaalphabeta-subunit drastically collapsed, while the chimeric betabetaalpha-subunit conserved the native globin structure (Wakasugi, K., Ishimori, K., Imai, K., Wada, Y., and Morishima, I. (1994) J. Biol. Chem. 269, 18750-18756). SAXS data also suggested a partially disordered structure of the chimeric alphaalphabeta-subunit. Based on tryptophan fluorescence spectra and computer modeling from x-ray structures of native globins, steric constraint between Trp14 and Tyr125 would be induced in the chimeric alphaalphabeta-subunit, which would perturb the packing of the A- and H-helices and destabilize the globule structure. On the other hand, such a steric constraint was not found for the counterpart chimeric subunit, the betabetaalpha-subunit. The different stabilities of these module-substituted globins imply that modules would not always be stable "structural" units, and interactions between modules are crucial to construct stable globin subunits.

Urea-induced conformational changes in cold- and heat-denatured states of a protein, Streptomyces subtilisin inhibitor

Streptomyces subtilisin inhibitor (SSI) is known to exist in at least two distinct denatured states, cold-denatured (D') and heat-denatured (D) under acidic conditions. In the present work, we investigated the manner how increasing urea concentration from 0 to 8 M changes the polypeptide chain conformation of SSI that exists initially in the D' and D states as well as in the native state (N), in terms of the secondary structure, the tertiary structure, and the chain form, based on the results of the experiments using circular dichroism (CD), small-angle X-ray scattering (SAXS) and 1H-NMR spectroscopy. Our results indicate that the urea-induced conformational transitions of SSI under typical conditions of D' (pH 1.8, 3 degrees C) occur at least in two steps. In the urea concentration range of 0-2 M (step 1), a cooperative destruction of the tertiary structure occurs, resulting in a mildly denatured state (DU), which may still contain a little amount of secondary structures. In the concentration range of 2-4 M urea (step 2), the DU state gradually loses its residual secondary structure, and increases the radius of gyration nearly to a maximum value. At 4 M urea, the polypeptide chain is highly disordered with highly mobile side chains. Increasing the urea concentration up to 8 M probably results in the more highly denatured or alternatively the stiffer chain conformations. The conformational transition starting from the N state proceeds essentially the same way as in the above scheme in which D' is replaced with N. The conformational transition starting from the D state lacks step 1 because the D state contains no tertiary structures and is similar to the DU state. The fact that similar conformations are reached at urea concentrations above 2 M from different conformations of D', D, and N indicates that the effect of urea dominates in determining the polypeptide conformation of SSI in the denatured states rather than the pH and temperature.

A circular dichroism study of preferential hydration and alcohol effects on a denatured protein, pig calpastatin domain I

Pig calpastatin domain I (CSD1), a proteinase inhibitor that specifically blocks activity of calpain I and II, is a good candidate protein for studying conformational variations in the denatured form of protein. An extensive structural characterization of CSD1 reported in the first part of this work has shown that CSD1 at neutral pH is in an expanded and flexible conformation without secondary and tertiary structures. Next, we further studied cosolvent effects of protein-stabilizers, polyols and sulfate salts, as well as protein-destabilizers, alcohols, on the conformation of CSD1 monitored by far- and near-UV CD spectroscopy. We found that both groups of cosolvents at high concentration induce highly helical structures of CSD1, but without specific tertiary interactions. Based on the results on the polyols and the sulfate salts, we have suggested that the preferential hydration is one of the thermodynamic forces to induce secondary structures in the denatured state of protein. Variations in isodichroic points of changes in far-UV CD spectrum as functions of cosolvent species and their concentration have exhibited complexity of the processes. The present study implies that protein stability in the presence of cosolvents is often determined by free energy difference between the folded and the highly structured denatured state, not between the folded and the random state.

Targeted vinblastine chemotherapy with two preparations of lipiodol contrast medium

BACKGROUND

Long-term survival and cure can not be achieved in patients with unresectable metastatic liver cancer. In this study, to improve the antitumor activity of oily anticancer agents, which enable targeted cancer chemotherapy, various concentrations of vinblastine dissolved in Lipiodol ultrafluid (vinblastine/Lipiodol U) or Lipiodol F, which has three times the viscosity of Lipiodol ultrafluid, were used.

MATERIALS AND METHODS

Rabbits bearing VX2 tumors measuring 1 to 2 cm in diameter in the liver received arterial injections of 0.2 ml of these drugs, and antitumor activity were examined.

RESULTS

Complete necrosis of the tumor was observed in three of nine rabbits received vinblastine/Lipiodol U at 2.5 mg/ml. Complete necrosis of the tumor was observed in all eleven rabbits which received vinblastine/Lipiodol U at 5 mg/ml. At concentrations of 7.5 and 10 mg/ml, the necrotic area spread from the tumor to the liver parenchyma surrounding the tumor. The antitumor activity of vinblastine dissolved in Lipiodol F was increased compared with that of vinblastine dissolved in Lipiodol ultrafluid.

CONCLUSIONS

The antitumor activity of a kind of the oily anticancer agents, vinblastine/Lipiodol increased with increasing amounts of vinblastine dissolved in Lipiodol ultrafluid and with the increasing viscosity of the carrier, Lipiodol.

Correlation between arteriographic and electrocardiographic features during spasm in the left anterior descending coronary artery

BACKGROUND

The clinical role of collateral vessels, which are transiently augmented during coronary artery spasm, remains controversial.

OBJECTIVE

To examine the correlation between coronary arteriographic and electrocardiographic features during spasm in the left anterior descending artery (LAD).

METHODS

We studied 45 patients in whom LAD spasms were induced by administration of acetylcholine or ergonovine maleate into the left coronary artery, or in whom spontaneous LAD spasms were documented during diagnostic cardiac catheterization.

RESULTS

During spasm, only three patients had transient appearance or augmentation of collateral flow opacifying the LAD. In these three patients, electrocardiograms obtained from anterior precordial chest leads during LAD spasm showed ST-segment depression, ST-segment elevation followed by ST-segment depression, and only T-wave change, respectively. Except for these three patients, ST-segment elevations were observed in all other patients (31 of 34) with main-branch spasm of the LAD. However, ST-segment elevation was observed in only two of 11 patients in whom spasm of the diagonal branch alone was induced.

CONCLUSIONS

Our observations suggest that the electrocardiographic changes during spasm are not always a sensitive indicator of LAD side branch spasm or LAD main-branch spasm associated with collateral circulation. From consideration of the angiographic features of the collaterals in the three patients with LAD main-branch spasm, we speculate that the balance of tonus of both the recipient and donor arteries, and the degree of organic stenosis of the recipient artery, may have important roles in the mechanism responsible for the change in the appearance of collaterals in patients with coronary spasm.

Decrease in Thy-1 expression on peripheral CD34 positive cells induced by G-CSF mobilization. The Tohoku Children Leukemia Study Group

In order to ascertain the cytological features of peripheral hematopoietic progenitor cells (PHPC) mobilized after administration of chemotherapeutic agents and G-CSF, lineage- and progenitor cell-specific surface markers on CD34 positive (+) cells were sequentially examined. Nineteen evaluable samples were obtained from a malignant lymphoma, an acute lymphoblastic leukemia and 5 neuroblastoma patients. CD38 and HLA-DR were respectively expressed on more than 95% and approximately 85% of CD34+ PHPC cells. CD19 was also expressed on the majority and CD117 on 10 to 20% of the CD34+ cells. The most striking finding was that the Thy-1(CDw90)+/CD34+ population was decreased at the peak of mobilization of CD34+ cells as compared to the early phase after G-CSF administration (approximately 20% vs. 60%). These results suggest that decrease in Thy-1 expression on CD34+ cells is related to mechanisms easing CD34+ cell mobilization to the peripheral blood.

Coronary artery perforation with subepicardial hematoma

Coronary artery perforation is a relatively rare complication in coronary angioplasty. We report the case of a 71-year-old male, who was salvaged by emergency surgery, for cardiogenic shock due to subepicardial hematoma associated with balloon angioplasty. Such a case has not yet previously been reported.

Expression of GATA transcription factors in myelogenous and lymphoblastic leukemia cells

In the hematopoietic lineage, the transcription factors GATA-1 and GATA-2 show restricted and largely overlapping expression profiles, but GATA-2 is uniquely expressed in early hematopoietic progenitors. GATA-3 is found exclusively in T cells of hematopoietic lineage. To clarify whether these expression profiles are preserved or changed during the development of malignancies, we analyzed the expression of GATA factors in the blasts from leukemic children. A total of 18 myelogenous leukemia and 24 lymphoblastic leukemia (ALL) cases were investigated. In the majority of the former cases, GATA-2 mRNA expression and the expression of CD34 and c-kit antigens on leukemic cells were demonstrated. In contrast, GATA-2 mRNA and c-kit antigen could not be detected in CD34-positive cells from ALL patients. GATA-3 mRNA was expressed in all T-ALL cases, but not in any precursor B-ALL. These findings suggest that down-regulation of GATA-2 and expression of GATA-3 are important events for the commitment of cells to lymphoid and T cell lineage, respectively. The expression profiles of GATA factors in leukemic cells are generally consistent with those in their normal counterparts, and thus provide a useful tool to determine the lineage commitment of unclassified leukemia.

Successful treatment of steroid-resistant severe acute GVHD with 24-h continuous infusion of FK506

We report our findings in two cases of steroid-resistant severe acute GVHD after allogeneic BMT successfully treated with FK506 (tacrolimus). An 18-year-old female (patient 1) who underwent BMT from an HLA-identical sibling for ALL in first CR, developed generalized erythema and profuse watery diarrhea, which progressed to acute GVHD of grade III severity, resistant to steroid control. After continuous 24-h administration of FK506, the diarrhea improved within 10 days. Patient 2, a 9-year-old girl with AML who underwent unrelated BMT, had skin, gut and liver lesions of acute GVHD grade IV, which did not respond to high-dose steroid therapy. They were controlled, however, by continuous intravenous infusion of FK506. Both patients are still surviving after more than 1 year without any acute GVHD sequelae or signs of chronic illness. The adverse effects of FK506 were mild and tolerable in both cases. Comparison of our findings with those in the literature suggests that it is important to give FK506 at plasma concentrations as high as 25-35 ng/ml by continuous intravenous infusion for extended periods to control steroid-resistant severe acute GVHD.