Phase I study of the intravenous administration of attenuated Salmonella typhimurium to patients with metastatic melanoma.

PURPOSE: A strain of Salmonella typhimurium (VNP20009), attenuated by chromosomal deletion of the purI and msbB genes, was found to target to tumor and inhibit tumor growth in mice. These findings led to the present phase I study of the intravenous infusion of VNP20009 to patients with metastatic cancer. PATIENTS AND METHODS: In cohorts consisting of three to six patients, 24 patients with metastatic melanoma and one patient with metastatic renal cell carcinoma received 30-minute intravenous bolus infusions containing 10(6) to 10(9) cfu/m(2) of VNP20009. Patients were evaluated for dose-related toxicities, selective replication within tumors, and antitumor effects. RESULTS: The maximum-tolerated dose was 3 x 10(8) cfu/m(2). Dose-limiting toxicity was observed in patients receiving 1 x 10(9) cfu/m(2), which included thrombocytopenia, anemia, persistent bacteremia, hyperbilirubinemia, diarrhea, vomiting, nausea, elevated alkaline phosphatase, and hypophosphatemia. VNP20009 induced a dose-related increase in the circulation of proinflammatory cytokines, such as interleukin (IL)-1beta, tumor necrosis factor alpha, IL-6, and IL-12. Focal tumor colonization was observed in two patients receiving 1 x 10(9) cfu/m(2) and in one patient receiving 3 x 10(8) cfu/m(2). None of the patients experienced objective tumor regression, including those patients with colonized tumors. CONCLUSION: The VNP20009 strain of Salmonella typhimurium can be safely administered to patients, and at the highest tolerated dose, some tumor colonization was observed. No antitumor effects were seen, and additional studies are required to reduce dose-related toxicity and improve tumor localization.     

Inhibition of spontaneous and experimental lung metastasis of soft-tissue sarcoma by tumor-targeting Salmonella typhimurium A1-R

Prognosis of patients with lung metastases of soft-tissue sarcoma is still poor. Therefore, novel systemic therapy is needed to improve the survival of soft-tissue sarcoma. In the present study, tumor-targeting therapy with a genetically-modified auxotrophic strain of Salmonella typhimurium, termed A1-R, was evaluated. Mouse models of primary soft tissue sarcoma and spontaneous lung metastasis were obtained by orthotopic intra-muscular injection of HT1080-RFP human fibrosarcoma cells. S. typhimurium A1-R was administered from day 14, once a week for two weeks. On day 28, lung samples were excised and observed with a fluorescence imaging system. The number of lung metastasis was 8.8 ± 3.4 in the untreated group and 0.8 ± 0.8 in the treated group (P = 0.024). A mouse model of experimental lung metastasis was obtained by tail vein injection of HT1080-RFP cells. The mice were treated with S. typhimurium A1-R (i.v.) on day 7, once a week for three weeks. S. typhimurium A1-R significantly reduced lung metastases and improved overall survival (P = 0.004). S. typhimurium A1-R bacterial therapy has future potential for treating advanced soft tissue sarcoma and improving prognosis of patients with lung metastasis.     

Intraperitoneal administration of tumor-targeting Salmonella typhimurium A1-R inhibits disseminated human ovarian cancer and extends survival in nude mice

Peritoneal disseminated cancer is highly treatment resistant. We here report the efficacy of intraperitoneal (i.p.) administration of tumor-targeting Salmonella typhimurium A1-R in a nude mouse model of disseminated human ovarian cancer. The mouse model was established by intraperitoneal injection of the human ovarian cancer cell line SKOV3-GFP. Seven days after implantation, mice were treated with S. typhimurium A1-R via intravenous (i.v.) or i.p. administration at the same dose, 5×10⁷ CFU, once per week. Both i.v. and i.p. treatments effected prolonged survival compared with the untreated control group (P=0.025 and P<0.001, respectively). However, i.p. treatment was less toxic than i.v. treatment. Tumor-specific targeting of S. typhimurium A1-R was confirmed with bacterial culture from tumors and various organs and tumor or organ colony formation after i.v. or i.p. injection. Selective tumor targeting was most effective with i.p. administration. The results of the present study show S. typhimurium A1-R has promising clinical potential for disseminated ovarian cancer, especially via i.p. administration.     

Systemic administration of doxorubicin-containing liposomes in cancer patients: a phase I study

A clinical study was designed to evaluate the tolerance of cancer patients to liposome-associated doxorubicin (L-DXR). The liposomes used contain phosphatidylglycerol, phosphatidylcholine, cholesterol, and DXR intercalated in the lipid bilayer, and have a mean size in the range of 0.3–0.5 μm. Thirty-two patients, most of them with primary or metastatic liver cancer refractory to conventional therapy, were entered into the study. A total of 69 courses of therapy was administered by intravenous infusion of a suspension of L-DXR (0.5-2.0 mg DXR/ml) in physiologic saline at an approximate rate of 2 ml/min given on a 3-week intermittent schedule. The L-DXR and phospholipid doses were escalated from 20 mg/m² and 0.3 g/m² to 120 mg/m² and 3.2 g/m² respectively. Treatment was generally well tolerated and acute toxic effects such as nausea and vomiting were mild and infrequent. Chills and fever (>38.0°C) were observed in three patients during infusion of L-DXR and in seven patients 6–12 h after the end of infusion. Median WBC nadir counts were 2700, 2300 and 700/μl at 85, 100 and 120 mg/m² respectively. All three patients receiving 120 mg/m² developed grade 4 leukopenia and fever requiring intravenous antibiotics, and, in two of them, severe stomatitis (grades 3 and 4) was observed. Significant hair loss was apparent in all patients receiving doses higher than 50 mg/m². The maximal tolerated dose of L-DXR appears to be 120 mg/m², with leukopenia and stomatitis being the dose-limiting factors. While the subacute toxicity of L-DXR appears to be qualitatively similar to that of free DXR, its tolerance exceeds the recommended dose of free DXR (75 mg/m²) in the standard 3-weekly schedule.     

Acodazole hydrochloride: phase I trial, pharmacokinetics, and evaluation of cardiotoxicity in dogs

Acodazole (NSC 305884) was examined in a Phase I trial evaluating a 1-h infusion repeated every 21 days in 37 patients with advanced carcinomas. Cardiac toxicity was dose-limiting at 1370 mg/m2, manifested as multiple premature ventricular contractions, QTc interval prolongation, and decreasing heart rate. Other toxicities included mild to moderate nausea and vomiting and local reaction near the i.v. injection site requiring the use of central venous catheters. Antineoplastic activity was not observed. Acodazole levels assayed by high-performance liquid chromatography disclosed a peak plasma level of 19 +/- 4 (SEM) micrograms/ml for 1370 mg/m2. Acodazole plasma levels decreased in a triphasic manner over a 100-fold range. The volume of distribution at steady state was 238 +/- 18 liter/m2 suggesting extensive tissue binding. The total body clearance was 13.6 +/- 0.9 liter/h/m2; the percentage of urinary excretion was 29 +/- 2% for 48 h. To evaluate cardiac toxicity, acodazole was administered to five dogs at 2262 mg/m2 (1-h infusion) which provided plasma concentrations similar to those achieved at 1370 mg/m2 in humans. Consistent findings in dogs were drug-related prolongation of QTc intervals, and reduction in heart rate, left ventricular dP/dt, and mean blood pressures. Clinical development of acodazole requires studies to further elucidate and alleviate this cardiac toxicity.     

In vivo administration of bryostatin 1, a protein kinase C activator, decreases murine resistance to Salmonella typhimurium.

Bryostatin 1, a potent activator of protein kinase C, has antitumor activity against murine lymphoma, leukemia, and melanoma. In vitro, this compound stimulates the release of gamma-interferon, interleukins, and hematopoietic growth factors from accessory cells and activates both T- and B-cells. Bryostatin 1 is also able to stimulate neutrophils to undergo oxidative burst and degranulation. Because of the ability of this compound to stimulate the immune system, cause release of immune mediators, and activate neutrophils, we have examined its effect on bacterial infection by using the gram-negative bacterium Salmonella typhimurium in mice. We find that animals given injections i.v. of S. typhimurium have a shortened life span if they are also given injections i.p. of nonlethal doses of bryostatin 1. There is a dose-response relationship with 100 micrograms/kg bryostatin 1 having a greater effect on survival than 40 micrograms/kg. Below 40 micrograms/kg there are no effects on survival. Analysis of the first 4 h of Salmonella infection demonstrates that bryostatin 1 does not affect the blood clearance of the bacterium. However, by day 2 of infection greater numbers of bacteria are found in the livers and spleens of mice given injections of bryostatin 1. By day 5, 10-fold more S. typhimurium bacteria are found in the livers and spleens of mice receiving 40 micrograms/kg of bryostatin 1. To determine whether bryostatin 1 was affecting growth or causing the death of bacteria, we used a Salmonella carrying a plasmid which has a temperature-sensitive origin of replication and is unable to replicate when the bacteria are in mice. This experiment demonstrates that bryostatin 1 represses bacterial killing but does not affect bacterial growth. Bryostatin 1 given i.p. stimulates a transient syndrome of weight loss and diarrhea from which the mice recover and regain weight, suggesting that bryostatin 1 may release a number of important humoral mediators in vivo. The weight loss is exacerbated by Salmonella infection with mice receiving bryostatin 1 and S. typhimurium, in that they lose approximately 33% of body weight prior to death. Thus, at doses used to treat murine tumors, bryostatin 1 treatment does not affect the clearance of S. typhimurium from the blood but does decrease the killing of bacteria in the liver and spleen, leading to early animal death. Such potential effects of bryostatin 1 on the outcome of bacterial infections should be evaluated in ongoing human trials of this agent.     

Oral administration of attenuated S. typhimurium carrying shRNA-expressing vectors as a cancer therapeutic

RNAi has been successfully applied in genomic research, and it also holds considerable promise as a therapeutic approach to suppress disease-causing gene expression. Here, we show that attenuated S. typhimurium were capable of delivering shRNA-expressing vectors to mammalian cells and inducing RNAi in vitro and in vivo. Upon oral administration, S. typhimurium carrying shRNA-expressing vectors targeting bcl2 induced significant gene silencing in murine melanoma cells that led to a remarkably delayed tumor growth and prolonged survival in the mouse model. These results suggest that bacteria mediated RNAi may be a new potent approach to the treatment of cancers.     

Adjuvant treatment with tumor-targeting Salmonella typhimurium A1-R reduces recurrence and increases survival after liver metastasis resection in an orthotopic nude mouse model

Colon cancer liver metastasis is often the lethal aspect of this disease. Well-isolated metastases are candidates for surgical resection, but recurrence is common. Better adjuvant treatment is therefore needed to reduce or prevent recurrence. In the present study, HT-29 human colon cancer cells expressing red fluorescent protein (RFP) were used to establish liver metastases in nude mice. Mice with a single liver metastasis were randomized into bright-light surgery (BLS) or the combination of BLS and adjuvant treatment with tumor-targeting S. typhimurium A1-R. Residual tumor fluorescence after BLS was clearly visualized at high magnification by fluorescence imaging. Adjuvant treatment with S. typhimurium A1-R was highly effective to increase survival and disease-free survival after BLS of liver metastasis. The results suggest the future clinical potential of adjuvant S. typhimurium A1-R treatment after liver metastasis resection.     

Mutagenicity of five cyclic N-nitrosamines: assay with Salmonella typhimurium.

The mutagenicity of five cyclic N-nitrosamines was studied with the use of Salmonella typhimurium TA1535 in vitro with and without microsomal activation. The carcinogens nitrosopiperidine and nitrosopyrrolidine required metabolic activation before manifesting mutagenic activity. Nitrosoproline and nitrosohydroxyproline, noncarcinogens, were not mutagenic. Nitroso-3-pyrrolidinol was mutagenic in the absence of microsomes, thereby suggesting a role of hydroxylation in the metabolic activation of nitrosopyrrolidine to an ultimate carcinogenic species.     

A phase I study of Onyx-015, an E1B attenuated adenovirus, administered intratumorally to patients with recurrent head and neck cancer.

An E1B 55 kDa gene-deleted adenovirus, Onyx-015, which reportedly selectively replicates in and lyses p53-deficient cells, was administered by a single intratumoral injection to a total of 22 patients with recurrent head and neck cancer. The objectives of this Phase I study were to determine the safety, feasibility, and efficacy of this therapy and determine any correlation to p53 status. Six cohorts were investigated with a dose escalation from 10(7)-10(11) plaque-forming units. Toxicity was assessed using NCIC criteria. Tumor response was assessed by clinical and radiological measurement. Blood samples were taken to detect adenovirus DNA and neutralizing antibody to adenovirus. Tumor biopsies were taken to detect adenovirus by in situ hybridization. Treatment was well tolerated, with the main toxicity being grade 1/2 flu-like symptoms. Dose-limiting toxicity was not reached at the highest dose of 10(11) plaque-forming units. Twenty-one of the 22 patients treated showed an increase in neutralizing antibody to adenovirus. In situ hybridization showed viral replication in 4 of 22 patients treated, all of whom had mutant p53 tumors. Using conventional response criteria, no objective responses were observed. However, magnetic resonance imaging scans were suggestive of tumor necrosis at the site of viral injection in five patients, three of whom were classified using nonconventional criteria as partial responders, and two of whom were classified using nonconventional criteria as minor responders. Of these five cases, four had mutant p53 tumors. The response duration for the three partial responders was 4, 8, and 12 weeks. An additional eight patients had stable disease in the injected tumors lasting from 4-8 weeks. These preliminary results show that intratumoral administration of Onyx-015 is feasible, well tolerated, and associated with biological activity. Further investigation of Onyx-015, particularly with a more frequent injection protocol and in combination with systemic chemotherapy, is warranted.     

Frequent administration of Dabis Maleate, a phase I study.

Dabis Maleate (1,4-bis(2'-chloroethyl)-1,4-diazabicyclo[2.2.1] Heptane dihydrogen dimaleate) (NSC 262666) is an alkylating quaternary nitrogen compound. In a previous phase I study using a once-every-3-weeks administration the dose-limiting toxicity was neurotoxicity and the recommended dose for phase II studies was 750 mg/m2 iv every 3 weeks. In vitro studies suggested a higher activity after more frequent administration, and in vivo studies a better therapeutic index with prolonged infusion. We studied 11 patients with solid tumors. Dose levels tested ranged from 250-750 mg/m2, either as a day 1-3 regimen or weekly, the latter as bolus administration or as prolonged infusion. The dose-limiting toxicity was neurotoxicity consisting of paresthesias and ataxia. Nausea and vomiting were moderate. No other major toxicity was observed. The dose recommended for phase II studies is 500 mg/m2/week as a 6-hour iv infusion for 6 weeks, followed by a 3-week rest period.     

Systemic administration of attenuated Salmonella choleraesuis carrying thrombospondin-1 gene leads to tumor-specific transgene expression, delayed tumor growth and prolonged survival in the murine melanoma model

Some anaerobic and facultative anaerobic bacteria have been used experimentally as anticancer agents because of their selective growth in the hypoxia regions of solid tumors after systemic administration. We have previously shown the feasibility of using attenuated Salmonella choleraesuis as a gene delivery vector. In this study, we exploited S. choleraesuis carrying thrombospondin-1 (TSP-1) gene for treating primary melanoma and experimental pulmonary metastasis in the syngeneic murine B16F10 melanoma model. Systemic administration of S. choleraesuis allowed targeted gene delivery to tumors. The bacteria accumulated preferentially in tumors over livers and spleens at ratios ranging from 1000:1 to 10,000:1. The level of transgene expression via S. choleraesuis-mediated gene transfer in tumors could reach more than 1800-fold higher than in livers and spleens. Notably, bacterial accumulation was also observed in the lungs with metastatic nodules, but not in healthy lungs. When administered into mice bearing subcutaneous or pulmonary metastatic melanomas, S. choleraesuis carrying TSP-1 gene significantly inhibited tumor growth and enhanced survival of the mice. Immunohistochemical studies in the tumors from these mice displayed decreased intratumoral microvessel density. Taken together, these findings suggest that TSP-1 gene therapy delivered by S. choleraesuis may be effective for the treatment of primary as well as metastatic melanomas.     

Anterior pituitary function in female dogs with spontaneous mammary tumors: I. Growth hormone

It has been hypothesized that growth hormone (GH) plays a major role in the pathogenesis of canine mammary tumor disease. In order to test this hypothesis, plasma GH levels were measured at rest and during dynamic function tests in dogs with benign or malignant proliferative mammary lesions and in control dogs. Both in control dogs and in dogs with benign disease, basal GH levels were found to be elevated during both metestrus and progestin treatment, as compared to anestrus. Dogs with benign or malignant disease did not have higher basal GH levels than control dogs matched for the effect of endogenous or exogenous progestin exposure. The GH response to glucose or thyrotropin releasing hormone (TRH) did not vary significantly with progestin exposure, nor between the 3 groups of animals. The stimulatory effect of clonidine upon GH secretion was reduced in dogs with benign or malignant disease as compared to controls matched for the effect of progestin exposure. These findings indicate that mammary tumor disease in the dog is associated with a disturbance in the regulation of GH release.     

A phase I and pharmacology study of an oral platinum complex,JM216: dose-dependent pharmacokinetics with single-dose administration

JM216 [bis-acetato-ammine-dichloro-cyclohexylamine-platinum (IV)] is an oral platinum complex with in vivo activity against murine and human tumor models and a lack of nephro- and neurotoxicity in rodents. During a phase I study of a single-dose schedule, JM216 was given in dry-filled hard gelatin capsules by mouth without hydration or diuresis. In all, 37 patients were given a total of 88 courses at doses ranging from 60 to 700 mg/m². The study was stopped before the MTD was reached because of nonlinear pharmacokinetics. Myelosuppression was manifest by leucopenia or thrombocytopenia and showed marked variability at 420–700 mg/m². Vomiting was mild and controllable by antiemetics in approximately 50% of courses. The onset of vomiting was delayed to 4 h after during ingestion. There was no nephro-, oto- or neurotoxicity. A partial response was recorded in a patient with recurrent ovarian cancer, and significant falls in plasma tumour markers (CA125) were seen in two further cases. Plasma pharmacokinetics were linear and showed moderate interpatient variability at dose levels of 120 mg/m². At dose levels of 200 mg/m², C_max and AUC increased less than proportionally to dose. This was associated with greater interpatient pharmacokinetic variability and reduced urinary platinum recovery. A significant sigmoidal relationship existed between ultrafilterable plasma AUC and the percentage of reduction in platelet count (r ²=0.78). Nonlinear absorption was a limitation to this single-dose schedule of oral NM216; however, little nonhaematological toxicity was seen at doses associated with myelosuppression and antitumour activity. Clinical studies of divided dose schedules using doses within the range of pharmacokinetic linearity (120 mg/m²) are now being investigated.Abbreviations AUC Area under the plasma concentration versus time curve - C _max peak plasma concentration - cxs courses - FAAS flameless atomic absorption spectrophotometry - Gd CTC toxicity severity grade - JM216 bis-acetato-ammine-dichloro-cyclohexylamineplatinum(IV) - MRT mean residence time - MTD maximally tolerable dose - pts patients - T _max time of peak plasma concentration     

Antitumor effect of VNP20009, an attenuated Salmonella, in murine tumor models

VNP20009, a genetically modified strain of Salmonella typhimurium with deletions in the msbB and purI loci, exhibited antitumor activities when given systemically to tumor-bearing mice. VNP20009 inhibited the growth of subcutaneously implanted B16F10 murine melanoma, and the human tumor xenografts Lox, DLD-1, A549, WiDr, HTB177, and MDA-MB-231. A single intravenous injection of VNP20009, at doses ranging from 1 x 10(4) to 3 x 10(6) cfu/mouse, produced tumor growth inhibitions of 57-95%. Tumor volume doubling time, another indicator for tumor growth inhibition, also significantly increased in mice treated with VNP20009. Using mice with immune system deficiencies, we also demonstrated that the antitumor effects of VNP20009 did not depend on the presence of T and B cells. In addition, VNP20009, given intravenously, inhibited the growth of lung metastases in mice. Only live bacteria showed the antitumor effect.     

Intravenous administration of recombinant human macrophage colony-stimulating factor to patients with metastatic cancer: a phase I study.

PURPOSE: Recombinant human macrophage colony-stimulating factor (M-CSF) has been shown to stimulate specifically macrophage lineage differentiation in vitro and to induce cells capable of antitumor activity alone or in combination with an antibody. The administration of M-CSF to mice has demonstrated antitumor therapeutic effects in vivo. Therefore, a phase I trial of M-CSF administration to patients with metastatic cancer was undertaken. PATIENTS AND METHODS: M-CSF was given by intermittent intravenous bolus infusion every 8 hours for 7 days; the treatment cycle was repeated once after a week of rest. Cohorts of three patients underwent dose escalation from 10 to 100,000 micrograms/m2/d; 23 patients received 27 courses of M-CSF administration. All patients had metastatic solid tumors refractory to conventional therapy, including renal cell carcinoma (RCC) (nine), melanoma (seven), and colorectal carcinoma (seven). RESULTS: Treatment-related toxicity was minimal; five patients developed transient signs of ocular or periorbital inflammation, with iridocyclitis as the most severe manifestation. At the highest doses, platelet counts decreased with therapy (but remained > 100,000/mm3) and the absolute monocyte count increased during the course of therapy. Only at 30,000 and 100,000 micrograms/m2/d was treatment limited because of toxicity (iritis and malaise). Pharmacokinetic studies demonstrated up to a 1,000-fold increase in circulating serum M-CSF after bolus infusion; half-life varied from 1 to 6 hours. Complete regression of mediastinal adenopathy and multiple pulmonary metastases were observed in one patient with RCC. CONCLUSION: Recombinant M-CSF can be administered safely to patients with metastatic cancer at doses that demonstrate biologic activity.     

Hepatic drug targeting: phase I evaluation of polymer-bound doxorubicin.

PURPOSE: Preclinical studies have shown good anticancer activity following targeting of a polymer bearing doxorubicin with galactosamine (PK2) to the liver. The present phase I study was devised to determine the toxicity, pharmacokinetic profile, and targeting capability of PK2. PATIENTS AND METHODS: Doxorubicin was linked via a lysosomally degradable tetrapeptide sequence to N-(2-hydroxypropyl)methacrylamide copolymers bearing galactosamine. Targeting, toxicity, and efficacy were evaluated in 31 patients with primary (n = 25) or metastatic (n = 6) liver cancer. Body distribution of the radiolabelled polymer conjugate was assessed using gamma-camera imaging and single-photon emission computed tomography. RESULTS: The polymer was administered by intravenous (i.v.) infusion over 1 hour, repeated every 3 weeks. Dose escalation proceeded from 20 to 160 mg/m(2) (doxorubicin equivalents), the maximum-tolerated dose, which was associated with severe fatigue, grade 4 neutropenia, and grade 3 mucositis. Twenty-four hours after administration, 16.9% +/- 3.9% of the administered dose of doxorubicin targeted to the liver and 3.3% +/- 5.6% of dose was delivered to tumor. Doxorubicin-polymer conjugate without galactosamine showed no targeting. Three hepatoma patients showed partial responses, with one in continuing partial remission 47 months after therapy. CONCLUSION: The recommended PK2 dose is 120 mg/m(2), administered every 3 weeks by IV infusion. Liver-specific doxorubicin delivery is achievable using galactosamine-modified polymers, and targeting is also seen in primary hepatocellular tumors.     

Patterns of hepatic and splenic colonization by an attenuated strain of Salmonella typhimurium containing the gene for human interleukin-2: a novel anti-tumor agent

Currently, there is no effective treatment for unresectable hepatic malignancies. Salmonella sp. are known to naturally track to the liver during active infection. A live biological vector was developed for delivery of Interleukin-2 (IL-2) to the liver for anti-tumor purposes. The avirulent and highly immunogenic c4550 strain of Salmonella typhimurium was used to express the IL-2 protein [renamed c4550(pIL-2)]. We have previously demonstrated that the c4550(pIL-2) produces biologically active IL-2 (up to 46.2 IU/ml) and that a single gavage feeding of 10(7) colony forming units (cfu) of c4550(pIL-2) significantly reduced the number of hepatic metastases when compared to animals fed salmonella lacking the IL-2 gene or non-treated controls. The goal of the current studies was to determine the pattern of splenic and hepatic colonization of Salmonella-IL2. Hepatic and splenic colonization was determined following administration of 10(7) cfu of c4550(pIL-2) and c4550(pYA292) via a single gavage feeding to C57BL/6 mice. Five experiments of antibiotic regimen administration were conducted where splenic and hepatic homogenates were cultured after 14 days of parenteral and/or oral antibiotics. The natural history of hepatic and splenic colonization was also determined for animals without antibiotic treatment. Despite administration of various antibiotic regimens using different routes, eradication of salmonella with and without IL-2 was not achieved. Salmonella, however, was not cultured from hepatic and splenic tissue at 4 months after a single gavage feeding of salmonella with no specific treatment. In conclusion, oral administration of c4550(pIL-2) may represent a novel form of in vivo biotherapy for unresectable hepatic malignancies. Antibiotics do not accelerate eradication of this bacteria and it appears that c4550(pIL-2) follows the natural pathophysiological of salmonella infection in which eradication from the splenic and hepatic tissue occurs over a period of 2-4 months.