Recurrent hyperactive ESR1 fusion proteins in endocrine therapy-resistant breast cancer.

Background: Estrogen receptor-positive (ER-positive) metastatic breast cancer is often intractable due to endocrine therapy resistance. Although ESR1 promoter switching events have been associated with endocrine-therapy resistance, recurrent ESR1 fusion proteins have yet to be identified in advanced breast cancer. Patients and methods: To identify genomic structural rearrangements (REs) including gene fusions in acquired resistance, we undertook a multimodal sequencing effort in three breast cancer patient cohorts: (i) mate-pair and/or RNAseq in 6 patient-matched primary-metastatic tumors and 51 metastases, (ii) high coverage (>500×) comprehensive genomic profiling of 287-395 cancer-related genes across 9542 solid tumors (5216 from metastatic disease), and (iii) ultra-high coverage (>5000×) genomic profiling of 62 cancer-related genes in 254 ctDNA samples. In addition to traditional gene fusion detection methods (i.e. discordant reads, split reads), ESR1 REs were detected from targeted sequencing data by applying a novel algorithm (copyshift) that identifies major copy number shifts at rearrangement hotspots. Results: We identify 88 ESR1 REs across 83 unique patients with direct confirmation of 9 ESR1 fusion proteins (including 2 via immunoblot). ESR1 REs are highly enriched in ER-positive, metastatic disease and co-occur with known ESR1 missense alterations, suggestive of polyclonal resistance. Importantly, all fusions result from a breakpoint in or near ESR1 intron 6 and therefore lack an intact ligand binding domain (LBD). In vitro characterization of three fusions reveals ligand-independence and hyperactivity dependent upon the 3' partner gene. Our lower-bound estimate of ESR1 fusions is at least 1% of metastatic solid breast cancers, the prevalence in ctDNA is at least 10× enriched. We postulate this enrichment may represent secondary resistance to more aggressive endocrine therapies applied to patients with ESR1 LBD missense alterations. Conclusions: Collectively, these data indicate that N-terminal ESR1 fusions involving exons 6-7 are a recurrent driver of endocrine therapy resistance and are impervious to ER-targeted therapies.

Hybrid capture-based genomic profiling of circulating tumor DNA from patients with estrogen receptor-positive metastatic breast cancer.

BACKGROUND: Genomic changes that occur in breast cancer during the course of disease have been informed by sequencing of primary and metastatic tumor tissue. For patients with relapsed and metastatic disease, evolution of the breast cancer genome highlights the importance of using a recent sample for genomic profiling to guide clinical decision-making. Obtaining a metastatic tissue biopsy can be challenging, and analysis of circulating tumor DNA (ctDNA) from blood may provide a minimally invasive alternative. PATIENTS AND METHODS: Hybrid capture-based genomic profiling was carried out on ctDNA from 254 female patients with estrogen receptor-positive breast cancer. Peripheral blood samples were submitted by clinicians in the course of routine clinical care between May 2016 and March 2017. Sequencing of 62 genes was carried out to a median unique coverage depth of 7503×. Genomic alterations (GAs) in ctDNA were evaluated and compared with matched tissue samples and genomic datasets of tissue from breast cancer. RESULTS: At least 1 GA was reported in 78% of samples. Frequently altered genes were TP53 (38%), ESR1 (31%) and PIK3CA (31%). Temporally matched ctDNA and tissue samples were available for 14 patients; 89% of mutations detected in tissue were also detected in ctDNA. Diverse ESR1 GAs including mutation, rearrangement and amplification, were observed. Multiple concurrent ESR1 GAs were observed in 40% of ESR1-altered cases, suggesting polyclonal origin; ESR1 compound mutations were also observed in two cases. ESR1-altered cases harbored co-occurring GAs in PIK3CA (35%), FGFR1 (16%), ERBB2 (8%), BRCA1/2 (5%), and AKT1 (4%). CONCLUSIONS: GAs relevant to relapsed/metastatic breast cancer management were identified, including diverse ESR1 GAs. Genomic profiling of ctDNA demonstrated sensitive detection of mutations found in tissue. Detection of amplifications was associated with ctDNA fraction. Genomic profiling of ctDNA may provide a complementary and possibly alternative approach to tissue-based genomic testing for patients with estrogen receptor-positive metastatic breast cancer.

Safety and efficacy outcomes with erythropoiesis-stimulating agents in patients with breast cancer: a meta-analysis.

BACKGROUND: New data on erythropoiesis-stimulating agents (ESAs) regarding overall survival and disease progression-related outcomes in patients with breast cancer receiving chemotherapy are presented in a meta-analysis of controlled trials of ESA use (epoetin α, epoetin ß, darbepoetin α, biosimilars). PATIENTS AND METHODS: A literature search identified reports from January 1997 through March 2014. We used company databases for Amgen, Inc., or Janssen studies and published data for other studies. Random-effects odds ratios (ORs) were calculated to compare results for patients randomized to ESA with those randomized to control. RESULTS: Deaths were reported for 571 of 2346 patients (24%) in the ESA groups and 523 of 2367 patients (22%) in the control groups [OR, 1.20; 95% confidence interval (CI) 1.03-1.40]. Sensitivity analyses were conducted to explore the effects of individual studies and exclusion of one study (BEST) resulted in an OR for death of 1.12 (95% CI 0.94-1.34). In seven studies reporting progression-related end points (N = 4197; ESA n = 2088; control n = 2109), the OR was 1.01 (95% CI 0.87-1.16) for ESA compared with control. CONCLUSIONS: After incorporating recent results of ESA use in patients with breast cancer, risks of survival and progression-free survival remain consistent with previously published data.

Effects of erythropoietin receptors and erythropoiesis-stimulating agents on disease progression in cancer.

Erythropoiesis-stimulating agents (ESAs) increase red blood cell (RBC) production in bone marrow by activating the erythropoietin receptor (EpoR) on erythrocytic-progenitor cells. Erythropoiesis-stimulating agents are approved in the United States and Europe for treating anaemia in cancer patients receiving chemotherapy based on randomised, placebo-controlled trials showing that ESAs reduce RBC transfusions. Erythropoiesis-stimulating agent-safety issues include thromboembolic events and concerns regarding whether ESAs increase disease progression and/or mortality in cancer patients. Several trials have reported an association between ESA use and increased disease progression and/or mortality, whereas other trials in the same tumour types have not provided similar findings. This review thoroughly examines available evidence regarding whether ESAs affect disease progression. Both clinical-trial data on ESAs and disease progression, and preclinical data on how ESAs could affect tumour growth are summarised. Preclinical topics include (i) whether tumour cells express EpoR and could be directly stimulated to grow by ESA exposure and (ii) whether endothelial cells express EpoR and could be stimulated by ESA exposure to undergo angiogenesis and indirectly promote tumour growth. Although assessment and definition of disease progression vary across studies, the current clinical data suggest that ESAs may have little effect on disease progression in chemotherapy patients, and preclinical data indicate a direct or indirect effect of ESAs on tumour growth is not strongly supported.

Molecular characterisation of formalin-fixed paraffin-embedded (FFPE) breast tumour specimens using a custom 512-gene breast cancer bead array-based platform.

BACKGROUND: Formalin-fixed, paraffin-embedded (FFPE) tumour tissue represents an immense but mainly untapped resource with respect to molecular profiling. The DASL (cDNA-mediated Annealing, Selection, extension, and Ligation) assay is a recently described, RT-PCR-based, highly multiplexed high-throughput gene expression platform developed by Illumina specifically for fragmented RNA typically obtained from FFPE specimens, which enables expression profiling. In order to extend the utility of the DASL assay for breast cancer, we have custom designed and validated a 512-gene human breast cancer panel. METHODS: The RNA from FFPE breast tumour specimens were analysed using the DASL assay. Breast cancer subtype was defined from pathology immunohistochemical (IHC) staining. Differentially expressed genes between the IHC-defined subtypes were assessed by prediction analysis of microarrays (PAM) and then used in the analysis of two published data sets with clinical outcome data. RESULTS: Gene expression signatures on our custom breast cancer panel were very reproducible between replicates (average Pearson's R²=0.962) and the 152 genes common to both the standard cancer DASL panel (Illumina) and our breast cancer DASL panel were similarly expressed for samples run on both panels (average R²=0.877). Moreover, expression of ESR1, PGR and ERBB2 corresponded well with their respective pathology-defined IHC status. A 30-gene set indicative of IHC-defined breast cancer subtypes was found to segregate samples based on their subtype in our data sets and published data sets. Furthermore, several of these genes were significantly associated with overall survival (OS) and relapse-free survival (RFS) in these previously published data sets, indicating that they are biomarkers of the different breast cancer subtypes and the prognostic outcomes associated with these subtypes. CONCLUSION: We have demonstrated the ability to expression profile degraded RNA transcripts derived from FFPE tissues on the DASL platform. Importantly, we have identified a 30-biomarker gene set that can classify breast cancer into subtypes and have shown that a subset of these markers is prognostic of OS and RFS.

Prostate cancer genes associated with TMPRSS2-ERG gene fusion and prognostic of biochemical recurrence in multiple cohorts.

BACKGROUND: Recent studies have indicated that prostate cancer patients with the TMPRSS2-ERG gene fusion have a higher risk of recurrence. To identify markers associated with TMPRSS2-ERG fusion and prognostic of biochemical recurrence, we analysed a cohort of 139 men with prostate cancer for 502 molecular markers. METHODS: RNA from radical prostatectomy tumour specimens was analysed using cDNA-mediated, annealing, selection, extension and ligation (DASL) to determine mRNAs associated with TMPRSS2-ERG T1/E4 fusion and prognostic of biochemical recurrence. Differentially expressed mRNAs in T1/E4-positive tumours were determined using significance analysis of microarrays (false discovery rate (FDR) <5%). Univariate and multivariate Cox regression determined genes, gene signatures and clinical factors prognostic of recurrence (P-value <0.05, log-rank test). Analysis of two prostate microarray studies (GSE1065 and GSE8402) validated the findings. RESULTS: In the 139 patients from this study and from a 455-patient Swedish cohort, 15 genes in common were differentially regulated in T1/E4 fusion-positive tumours (FDR <0.05). The most significant mRNAs in both cohorts coded ERG. Nine genes were found prognostic of recurrence in this study and in a 596-patient Minnesota cohort. A molecular recurrence score was significant in prognosticating recurrence (P-value 0.000167) and remained significant in multivariate analysis of a mixed clinical model considering Gleason score and TMPRSS2-ERG fusion status. CONCLUSIONS: TMPRSS2-ERG T1/E4 fusion-positive tumours had differentially regulated mRNAs observed in multiple studies, the most significant one coded for ERG. Several mRNAs were consistently associated with biochemical recurrence and have potential clinical utility but will require further validation for successful translation.

Side-population cells in luminal-type breast cancer have tumour-initiating cell properties, and are regulated by HER2 expression and signalling.

BACKGROUND: The expression of side-population (SP) cells and their relation to tumour-initiating cells (T-ICs) have been insufficiently studied in breast cancer (BC). We therefore evaluated primary cell cultures derived from patients and a panel of human BC cell lines with luminal- or basal-molecular signatures for the presence of SP and BC stem cell markers. METHODS: The SPs from luminal-type BC were analysed for BC T-IC characteristics, including human epidermal growth factor receptor 2 (HER2), ERalpha, IGFBP7 expression and their ability to initiate tumours in non-obese diabetic severe combined immunodeficiency (NOD/SCID) mice. Pharmacological modulators were used to assess the effects of HER2 signalling and breast cancer-resistance protein (BCRP) expression on SPs. RESULTS: The SP was more prevalent in the luminal subtype of BC compared with the basal subtype. HER2 expression was significantly correlated with the occurrence of an SP (r(2)=0.75, P=0.0003). Disappearance of SP in the presence of Ko143, a specific inhibitor of the ATP-binding cassette transporter BCRP, suggests that BCRP is the predominant transporter expressed in this population. The SP also decreased in the presence of HER2 signalling inhibitors AG825 or trastuzumab, strengthening the notion that HER2 contributed to the SP phenotype, likely through downstream AKT signalling. The SP cells from luminal-type MCF-7 cells with enforced expression of HER2, and primary cells with luminal-like properties from a BC patient, displayed enrichment in cells capable of repopulating tumours in NOD/SCID mice. Engraftment of SP cells was inhibited by pretreatment with AG825 or by in vivo treatment with trastuzumab. INTERPRETATION: Our findings indicate an important role of HER2 in regulating SP and hence T-ICs in BC, which may account for the poor responsiveness of HER2-positive BCs to chemotherapy, as well as their aggressiveness.

EGFR-targeting drugs in combination with cytotoxic agents: from bench to bedside, a contrasted reality.

The clinical experience recently reported with epidermal growth factor receptor (EGFR)-targeting drugs confirms the synergistic interactions observed between these compounds and conventional cytotoxic agents, which were previously established at the preclinical stage. There are, however, examples of major gaps between the bench and the bedside. Particularly demonstrative is the failure of the tyrosine kinase inhibitors (TKIs) (gefitinib and erlotinib) combined with chemotherapy in pretreated nonsmall cell lung cancer patients. These discrepancies can be due to several factors such as the methodology used to evaluate TKI plus cytotoxic agent combinations in preclinical models and the insufficient consideration given to the importance of the drug sequences for the tested combinations. Recent advances in understanding the biologic basis of acquired resistance to these agents have great potential to improve their clinical effectiveness. The purpose of this review is to critically examine the experimental conditions of the preclinical background for anti-EGFR drug-cytotoxic agent combinations and to attempt to explain the gap between clinical observations and preclinical data.

Estimating the magnitude of trastuzumab effects within patient subgroups in the HERA trial.

BACKGROUND: Trastuzumab (Herceptin(R)) improves disease-free survival (DFS) and overall survival for patients with human epidermal growth factor receptor 2 (HER2)-positive early breast cancer. We aimed to assess the magnitude of its clinical benefit for subpopulations defined by nodal and steroid hormone receptor status using data from the Herceptin Adjuvant (HERA) study. PATIENTS AND METHODS: HERA is an international multicenter randomized trial comparing 1 or 2 years of trastuzumab treatment with observation after standard chemotherapy in women with HER2-positive breast cancer. In total, 1703 women randomized to 1-year trastuzumab and 1698 women randomized to observation were included in these analyses. Median follow-up was 23.5 months. The primary endpoint was DFS. RESULTS: The overall hazard ratio (HR) for trastuzumab versus observation was 0.64 [95% confidence interval (CI) 0.54-0.76; P < 0.0001], ranging from 0.46 to 0.82 for subgroups. Estimated improvement in 3-year DFS in subgroups ranged from +11.3% to +0.6%. Patients with the best prognosis (those with node-negative disease and tumors 1.1-2.0 cm) had benefit similar to the overall cohort (HR 0.53, 95% CI 0.26-1.07; 3-year DFS improvement +4.6%, 95% CI -4.0% to 13.2%). CONCLUSIONS: Adjuvant trastuzumab therapy reduces the risk of relapse similarly across subgroups defined by nodal status and steroid hormone receptor status, even those at relatively low risk for relapse.

Comparative cytotoxicity of C-1311 in colon cancer in vitro and in vivo using the hollow fiber assay.

The aim of this study was to investigate the antiproliferative effects of C-1311 (Symadex), a member of the imidazoacridinone family, in human colorectal cancer cells. In the in vitro screen, C-1311 led to the most prominent growth inhibition in HT29, HCT116, and COLO205 cell lines when compared to oxaliplatin, CPT-11, DFUR, 5-FU and capecitabine. The GI(50)values for C-1311 ranged from 0.12 to 0.83 microM and the TGI concentrations (resulting in total growth inhibition) were 6- to 13-fold lower than those of other agents. In the hollow fiber assay in vivo, C-1311 caused 77% growth inhibition of HT29 in the intraperitoneal site as compared to paclitaxel (17% growth inhibition). In the subcutaneous site, C-1311 produced 57% growth inhibition while paclitaxel showed no cell growth inhibition effects. This unique cytotoxicity profile of C-1311 warrants further investigation and supports its clinical development in colon cancer patients. Symadex (C-1311) is currently in phase 2 clinical trials.

The role of methotrexate in osteosarcoma.

High-dose methotrexate (MTX) is one of the agents currently used in intensive adjuvant chemotherapy regimens for nonmetastatic osteosarcoma. To elucidate the role of high-dose MTX in this disease, we present the history of trials conducted with MTX from the first single-agent studies through progressively complex combination regimens. With this background, some of the basic issues concerning MTX therapy in osteosarcoma are discussed.

Cephalotaxine esters: antileukemic advance or therapeutic failure?

Clinical trials conducted in the People's Republic of China and the United States of the antileukemic efficacy of the cephalotaxine esters are reviewed. Harrington has been incorporated into combination regimens for the treatment of newly diagnosed acute nonlymphocytic leukemia (ANLL) in China, and activity with cephalotaxine esters has also been noted in chronic myelogenous leukemia. While the investigational agent homoharringtonine has shown some activity in the United States in ANLL, investigator interest in the United States has waned because of toxicity and inconvenient schedules. The Chinese trials have used different schedules than have U.S. studies and have been associated with less toxicity. These trials provide new information that may lead to further investigations of the cephalotaxine esters in the United States.

Pentostatin in hairy cell leukemia: treatment by the special exception mechanism.

An analysis of the clinical outcomes in 66 patients with hairy cell leukemia treated with pentostatin under the Special Exception mechanism of the Division of Cancer Treatment, National Cancer Institute, between 1983 and 1987 has revealed a favorable balance of risk and benefit. Hematologic parameters and performance status were improved in most patients treated outside the clinical trials mechanism. The treating physicians considered 37 patients (56%) to be complete responders and 15 patients (23%) to be partial responders. Four patients (6%) died while receiving pentostatin. Life-threatening leukopenia (wbc count, less than 1,000/mm3) was reported in 24% of patients, and severe or life-threatening infection occurred in 11%. The experience gained with these patients supplements the information presently being collected from the controlled clinical trials and supports the development of a group C treatment protocol.

4-Ipomeanol: a novel investigational new drug for lung cancer.

4-Ipomeanol (IPO) is the first agent to undergo preclinical development at the National Cancer Institute (NCI) based principally on a specific biochemical-biological rationale for clinical investigation as an antineoplastic agent targeted against lung cancer. This disease-specific development of IPO was initially stimulated by observations that the compound was activated by metabolism, preferentially within the mammalian lung, specifically within bronchiolar Clara cells, and that its predominant toxicity was to the lung in most species. IPO is inactive or only minimally active against most conventional antitumor test systems. However, some human lung cancer cell lines, as well as a variety of fresh human lung tumor biopsy specimens, have been shown to be capable of mediating the in situ biotransformation of IPO to a potentially cytotoxic intermediate. In this report, the biochemistry, metabolism, preclinical pharmacology, and toxicology of IPO are reviewed and the clinical development plans for this unique and challenging new agent are presented.

Deoxycytidine and deoxythymidine kinase activities in plasma of mice and patients with neoplastic disease.

In C57BL x DBA/2 F1 (hereafter called BD2F1) mice inoculated with P815 neoplasms and in AKR mice with spontaneously developing leukemia, significant amounts of plasma deoxycytidine and thymidine kinase activities were detected in advanced disease. Undetectable or low levels of such kinase activities were observed in normal BD2F1 and in control AKR mice. Initial studies with leukemia patients revealed increased amounts of plasma deoxycytidine and thymidine kinase activities correlating favorably with the peripheral white blood cell counts. Initial studies with small numbers of patients with solid tumors revealed significant activities of both kinases in plasma of patients with four different cancers. Healthy volunteers revealed enzyme activities only insignificantly above background.

Antineoplastic drug sensitivity of human MCF-7 breast cancer cells stably transfected with a human alpha class glutathione S-transferase gene.

Studies have suggested that the alpha class glutathione S-transferase (GST) may protect cells from the chemotherapeutic drugs chlorambucil and melphalan. In order to further define the function of human alpha class GST, a complementary DNA which encodes it was ligated into an expression vector under the direction of the human metallothionein-IIA promoter and stably transfected into human MCF-7 breast cancer cells in conjunction with the G418-selectable plasmid pSV2neo. Clonal cell lines were identified which expressed increased levels of GST enzyme activity (2.2- to 5.6-fold). The transfected cell lines also had increased peroxidase activity using cumene hydroperoxide as the substrate (1.9- to 3.8-fold) which is consistent with the intrinsic peroxidase activity of alpha class GSTs. Southern blot analysis indicated that genomic DNA from these cells contained a fragment indistinguishable from the transfected alpha class GST complementary DNA (850 base pairs); Northern blot analysis of total cellular RNA indicated that these cells contained appropriately sized alpha class GST RNA (980 nucleotides); and Western blot analysis indicated that, while MCF-7 cells contained no detectable alpha class GST protein, the transfected cells contained markedly elevated levels of alpha class GST but no detectable mu or pi class GST. These alpha class GST transfected cells had increased resistance to ethacrynic acid (2.1- to 3.0-fold). However, the transfected cells failed to show any increased resistance measured at the drug dosage which inhibited 50% of the colony formation to the chemotherapeutic drugs chlorambucil, melphalan, Adriamycin, or cisplatin under conditions of either continuous or 1-h drug exposure. Neither was there any change in sensitivity to the cytotoxins benzo(a)pyrene, benzo(a)pyrene-trans-7,8-dihydrodiol-9,10-epoxide (anti), or 1-chloro-2,4-dinitrobenzene. These studies indicate that expression of this human alpha class GST by itself in MCF-7 human breast cancer cells does not confer resistance to the chemotherapeutic drugs tested under the conditions used in these studies.

Role of thymidine in biochemical modulation: a review.

The role of thymidine in the treatment of cancer has been under clinical investigation for nearly a decade. Clinical trials have demonstrated that it lacks antitumor activity in its own right. In this review, the mechanism of action and rationale for the use of thymidine as a biochemical modulator of standard agents such as 5-fluorouracil, 1-beta-D-arabinofuranosylcytosine, and methotrexate are summarized. With this background, the clinical trials which have been conducted with thymidine, either alone or in combination, are described. We suggest a number of further studies of the role of thymidine in the biochemical modulation of antimetabolites.

Cis-diamminedichloroplatinum(II) nephrotoxicity and its relationship to renal gamma-glutamyl transpeptidase and glutathione.

To investigate the mechanism of cis-diamminedichloroplatinum(II) (cisplatin) nephrotoxicity, male Sprague-Dawley rats were given one injection of cisplatin (6 mg/kg i.v.). Urinary levels of amino acids and gamma-glutamyl transpeptidase were monitored for 8 days; kidney homogenate content of gamma-glutamyl transpeptidase was followed for 50 hr, and that of selenium-dependent glutathione peroxidase and total glutathione was followed for 4 hr. Peak urinary levels of amino acids and gamma-glutamyl transpeptidase occurred 4.5 hr after the i.v. dose. Glutamine, glycine, and ethanolamine were all elevated greater than 20 times that of the control at 4.5 hr and were still significantly elevated at 50 hr. Total renal glutathione content increased 51 +/- 17% (S.D.) of control values 20 min after cisplatin was given, before returning to base-line levels. No depletion of either renal glutathione or glutathione peroxidase was detected over the time interval studied. These results demonstrate an earlier physiological impairment than has hitherto been shown. Furthermore, depletion of glutathione and glutathione peroxidase does not occur in the rat kidney following therapeutic doses of cisplatin, in contrast to the changes observed in cardiac tissue following doxorubicin treatment.

Phase I bioavailability and pharmacokinetic study of hexamethylene bisacetamide (NSC 95580) administered via nasogastric tube.

A Phase I clinical trial and pharmacological study of nasogastrically administered hexamethylene bisacetamide, a polar-planar compound with in vitro differentiating activity, was conducted in 14 adult patients with refractory cancer. Hexamethylene bisacetamide was administered as a 5% (w/v) solution via a nasogastric or gastrostomy tube every 4 h for 5 days, followed in 21 days by a 5-day continuous i.v. infusion at the same daily dose. Parenteral drug administration was then continued at the same interval in the absence of disease progression or unacceptable toxicity. Three patients each were treated at doses of 12 and 24 g/m2/day, while eight patients received a dose of 30 g/m2/day. Toxicity was comparable for both routes of drug administration at the above doses. Nasogastrically administered hexamethylene bisacetamide was well tolerated at the lower doses, whereas neurotoxicity and nausea and vomiting were the major, but manageable, toxicities at 30 g/m2/day. Metabolic acidosis, renal dysfunction, mucositis, and thrombocytopenia were the other commonly observed drug toxicities at this dose. No objective tumor responses were observed. Hexamethylene bisacetamide was rapidly absorbed from the gastrointestinal tract with a mean measured bioavailability of 99 +/- 15%. Pharmacokinetic parameters for hexamethylene bisacetamide and plasma concentrations of the two major metabolites, N-acetyl-1,6-diaminohexane and 6-acetamidohexanoic acid, were similar for either route of administration in individual patients. Hexamethylene bisacetamide exhibited apparent monoexponential plasma elimination after either nasogastric or parenteral administration with 27 to 60% of the administered dose being excreted in the urine as parent compound. Based on its demonstrated complete bioavailability and tolerability, nasogastric administration of hexamethylene bisacetamide can be directly and safely substituted for the comparable i.v. dose.