Intravascular adenoviral agents in cancer patients: lessons from clinical trials

A large number of adenoviral agents are being developed for the treatment of cancer. However, the treatment-related death of a patient with ornithine transcarbamylase deficiency following adenovirus administration by hepatic artery has led to serious concerns regarding the safety of intravascular adenovirus. Both replication-incompetent (rAd.p53, e.g., SCH58500) and replication-selective (dl1520, aka Onyx-015; CG7870) oncolytic adenoviruses, by intravascular administration, are in clinical trials. We review Phases I and I/II results from these clinical trials. dl1520 and rAd.p53 were well-tolerated following hepatic artery infusion at doses of up to 2x10(12) and 2.5x10(13) particles, respectively. At a dose of 7.5x10(13) particles, rAd.p53 was associated with dose-limiting cardiac output suppression; dl1520 dose escalation did not proceed higher than 2x10(12). Intravenous (i.v.) infusions of dl1520 and CG7870 have been well tolerated by i.v. infusion at doses of 2x10(13) and 6x10(12), respectively, without identification of a maximally tolerated dose to date. Mild/moderate transaminitis was demonstrated in some patients on both the hepatic arterial and i.v. trials at doses >or=10(12) particles. Interleukin (IL)-6 and IL-10 were induced in a dose-dependent manner in most patients, but significant interpatient and intrapatient (on repeat doses) variabilities were demonstrated. Evidence of p53 gene expression (Ad.p53) or viral replication (dl1520) was demonstrated in the majority of patients receiving >or=10(12) particles. Over 100 cancer patients have been treated with intravascular adenovirus constructs to date with an acceptable toxicity profile; further clinical trial testing appears appropriate in cancer patients.     

Phase I trial of intraperitoneal injection of the E1B-55-kd-gene-deleted adenovirus ONYX-015 (dl1520) given on days 1 through 5 every 3 weeks in patients with recurrent/refractory epithelial ovarian cancer.

PURPOSE: Resistance to chemotherapy in ovarian cancer is frequently associated with mutations in the p53 gene. The adenovirus dl1520 (ONYX-015) with the E1B 55-kd gene deleted, allowing selective replication in and lysis of p53-deficient tumor cells, has shown preclinical efficacy against p53-deficient nude mouse-human ovarian carcinomatosis xenografts. PATIENTS AND METHODS: We undertook a phase I trial of intraperitoneal dl1520 in patients with recurrent ovarian cancer. Sixteen women with recurrent/refractory ovarian cancer received 35 cycles (median, two cycles) of dl1520 delivered on days 1 through 5 in four dose cohorts: 1 x 10(9) plaque forming units (pfu), 1 x 10(10) pfu, 3 x 10(10) pfu, and 1 x 10(11) pfu. RESULTS: The most common significant toxicities related to virus administration were flu-like symptoms, emesis, and abdominal pain. One patient receiving 1 x 10(10) pfu developed common toxicity criteria grade 3 abdominal pain and diarrhea, which was dose-limiting. The maximum-tolerated dose was not reached at 10(11) pfu, and at this dose level patients did not experience significant toxicity. There was no clear-cut evidence of clinical or radiologic response in any patient. Blood samples were taken for adenovirus DNA and neutralizing antibodies. Polymerase chain reaction data indicating presence of virus up to 10 days after the final (day 5) infusion of dl1520 are suggestive of continuing viral replication. CONCLUSION: This article therefore describes the first clinical experience with the intraperitoneal delivery of any replication-competent/-selective virus in cancer patients.     

An oncolytic adenovirus defective in pRb-binding (dl922-947) can efficiently eliminate pancreatic cancer cells and tumors in vivo in combination with 5-FU or gemcitabine

Pancreatic adenocarcinoma has a poor prognosis and frequently develops resistance to standard chemotherapeutics. Oncolytic adenoviruses represent a promising approach to overcome treatment resistance. The replication-selective dl922-947 adenovirus, defective in pRb binding, targets cancers with deregulated cell cycle control, such as the majority of pancreatic tumors. Cell killing efficacy was higher for dl922-947 than for adenovirus type 5 (Ad5) and the clinically approved dl1520 in pancreatic cancer cells with K-ras, p16 and p53 mutations. Combinations of dl922-947 and 5-fluorouracil or gemcitabine (2'2'-difluoro-2-deoxytidine) resulted in strong synergistic cell killing in Suit-2 and the highly drug- and virus-resistant Hs766T cells. Viral uptake increased in response to drugs, but was independent of the expression levels of the viral attachment receptor coxsackie and adenovirus receptor (CAR), whereas expression levels of the internalization receptors α(v)β(3)- and α(v)β(5)-integrins were increased. Early viral E1A expression was potently induced with drugs contributing to the synergistic effects. The dl922-947 mutant was more efficacious than Ad5 in vivo in Hs766T and Suit-2 xenograft models. In combination with gemcitabine, median survival was further prolonged. We demonstrate that dl922-947 is highly efficacious in pancreatic cancers and conclude that oncolytic adenoviruses harboring the E1ACR2 deletion have great potential for development into future clinical candidates for pancreatic cancer.     

Liver-directed viral therapy for cancer p53-targeted adenoviruses and beyond

Loss of p53 function is one of the most frequent genetic alterations in human cancers. Both replication-incompetent (rAd.p53, or SCH58500) and replication-selective (dl1520, or Onyx-015) adenoviruses are being developed for the treatment of p53-deficient cancers. Hepatic arterial infusion (HAI) has historically been used to selectively target colorectal tumors within the liver; consequently, regional therapy with adenovirus in this setting is an attractive approach. This article reviews Phase I and I/II HAI trial results with these adenovirus constructs.     

Biological activities of a recombinant adenovirus p53 (SCH 58500) administered by hepatic arterial infusion in a Phase 1 colorectal cancer trial

The major focus of intrahepatic arterial (IHA) administration of adenoviruses (Ad) has been on safety. Currently, there is little published data on the biological responses to Ad when administered via this route. As part of a Phase I study, we evaluated biological responses to a replication-defective adenovirus encoding the p53 transgene (SCH 58500) when administered by hepatic arterial infusion to patients with primarily colorectal cancer metastatic to the liver. In analyzing biological responses to the Ad vector, we found that both total and neutralizing Ad antibodies increased weeks after SCH 58500 infusion. The fold increase in antibody titers was not dependent on SCH 58500 dosage. The proinflammatory cytokine interleukin-6 (IL-6) transiently peaked within 6 h of dosing. The cytokine sTNF-R2 showed elevation by 24 h post-treatment, and fold increases were directly related to SCH 58500 doses. Cytokines TNF-alpha, IL-1beta, and sTNF-R1 showed no increased levels over 24 h. Predose antibody levels did not appear to predict transduction, nor did serum Ad neutralizing factor (SNF). Delivery of SCH 58500 to tumor tissue occurred, though we found distribution more predominantly in liver tissues, as opposed to tumors. RT-PCR showed significantly higher expression levels (P<0.0001, ANOVA) for adenovirus type 2 and 5 receptor (CAR) in liver tissues, suggesting a correlation with transduction. Evidence of tumor-specific apoptotic activity was provided by laser scanning cytometry, which determined a coincidence of elevated nuclear p53 protein expression with apoptosis in patient tissue. IHA administration of a replication defective adenovirus is a feasible mode of delivery, allowing for exogenous transfer of the p53 gene into target tissues, with evidence of functional p53. Limited and transient inflammatory responses to the drug occurred, but pre-existing immunity to Ad did not preclude SCH 58500 delivery.     

Bevacizumab increases viral distribution in human anaplastic thyroid carcinoma xenografts and enhances the effects of E1A-defective adenovirus dl922-947

PURPOSE: Anaplastic thyroid carcinoma is a prime target for innovative therapy because it represents one of the most lethal human neoplasms and is refractory to conventional treatments such as chemotherapy and radiotherapy. We have evaluated a novel therapeutic approach based on the oncolytic replication-selective adenovirus dl922-947. EXPERIMENTAL DESIGN: The antitumor efficacies of the E1ADeltaCR2 (dl922-947) and DeltaE1B55K (dl1520) mutants were compared in human thyroid anaplastic carcinoma cells in culture and in xenografts in vivo. To enhance the effects of dl922-947, anaplastic thyroid carcinoma tumor xenografts were treated with dl922-947 in combination with bevacizumab. RESULTS: We showed that the efficacy of dl922-947 exceeded that of dl1520 in all tested anaplastic thyroid carcinoma cells in vitro and in vivo. Furthermore, bevacizumab in combination with dl922-947 significantly reduced tumor growth compared with single treatments alone. Bevacizumab treatment significantly improved viral distribution in neoplastic tissues. CONCLUSIONS: Our data showed that dl922-947 had a higher oncolytic activity compared with dl1520 in anaplastic thyroid carcinoma cell lines and might represent a better option for virotherapy of anaplastic thyroid carcinoma. Moreover, bevacizumab increased the oncolytic effects of dl922-947 by enhancing viral distribution in tumors. The results described herein encourage the use of the dl922-947 virus in combination with bevacizumab.     

Human dendritic cells efficiently phagocytose adenoviral oncolysate but require additional stimulation to mature

Oncolytic adenoviruses are emerging agents for treatment of cancer by tumor-restricted virus infection and cell lysis. Clinical trials have shown that oncolytic adenoviruses are well tolerated in patients but also that their antitumor activity needs improvement. A promising strategy toward this end is to trigger systemic and prolonged antitumor immunity by adenoviral oncolysis. Antitumor immune activation depends in large part on antigen presentation and T cell activation by dendritic cells (DCs). Thus, it is likely that the interaction of lysed tumor cells with DCs is a key determinant of such "oncolytic vaccination." Our study reveals that human DCs effectively phagocytose melanoma cells at late stages of oncolytic adenovirus infection, when the cells die showing preferentially features of necrotic cell death. Maturation, migration toward CCL19 and T cell stimulatory capacity of DCs, crucial steps for immune induction, were, however, not induced by phagocytosis of oncolysate, but could be triggered by a cytokine maturation cocktail. Therefore, oncolytic adenoviruses and adenoviral oncolysate did not block DC maturation, which is in contrast to reports for other oncolytic viruses. These results represent a rationale for inserting immunostimulatory genes into oncolytic adenovirus genomes to assure critical DC maturation. Indeed, we report here that adenoviral transduction of melanoma cells with CD40L during oncolysis triggers the maturation of human DCs with T cell stimulatory capacity similar to DCs matured by cytokines. We conclude that triggering and shaping DC-induced antitumor immunity by oncolytic adenoviruses "armed" with immunostimulatory genes holds promise for improving the therapeutic outcome of viral oncolysis in patients.     

Activity of the adenoviral E1A deletion mutant dl922-947 in ovarian cancer: comparison with E1A wild-type viruses, bioluminescence monitoring, and intraperitoneal delivery in icodextrin

The adenoviral mutant dl922-947 has potent activity in a variety of tumors. We investigated the efficacy of dl922-947 in ovarian carcinoma; compared its activity to wild-type adenovirus, dl309, and dl1520; and investigated the use of icodextrin to enhance activity in vivo. We also assessed the utility of luciferase bioluminescence imaging to quantify the response of human ovarian carcinoma xenografts to dl922-947. Ovarian carcinoma cell lines were transfected in vitro with dl922-947, adenovirus 5 wild-type (Ad5 WT), dl309, and dl1520 and monitored for S-phase induction, viral protein expression, replication, and overall survival. In vivo, the efficacy of dl922-947 when delivered in PBS or icodextrin to female nude mice bearing IGROV1 xenografts was determined. In vitro, dl922-947 induced lysis with greater efficacy than Ad5 WT, dl309, or dl1520 in all ovarian carcinoma cell lines tested, which was associated with earlier expression of viral proteins and S-phase induction. The lytic effect in immortalized ovarian surface epithelial cells confirmed that cellular retinoblastoma pathway status is a strong determinant of dl922-947 activity. In vivo, i.p. delivery of dl922-947 (5 x 10(9) particles daily x 5) increased median survival from 20 to 96 days (P < 0.0001) and delivery in icodextrin-enhanced survival further. However, delayed hepatic toxicity was evident in some dl922-947-treated mice, which was not dependent upon viral replication within tumor cells or the liver. dl922-947 has potency in ovarian carcinoma and i.p. delivery in icodextrin may enhance this activity. Immunocompetent models of ovarian carcinoma are required for further evaluation of hepatotoxicity.     

Inefficient killing of quiescent human epithelial cells by replicating adenoviruses: potential implications for their use as oncolytic agents

Cultured primary human cells have been widely used to assess the selectivity of oncolytic viruses as potential anticancer agents. As culture conditions can potentially have a significant impact on virus replication and ultimately cell killing, we evaluated the effects of dl309, a wild-type adenovirus, and dl01 / 07, a conditionally replicating adenovirus mutant, on quiescent and proliferating primary mammary epithelial cells. When primary cells were induced into quiescence, both viruses exhibited similar attenuated cell killing. However, cell killing by dl309 was superior to dl01 / 07 in proliferating primary cells. Analysis of viral effects at the level of entry, E2F activation, DNA replication, and late gene expression indicated that attenuation of dl309 in quiescent cells correlated with decreased expression of viral late genes such as hexon. In contrast, attenuation of dl01 / 07 in quiescent cells correlated with inefficient induction of E2F activity and inability to undergo efficient DNA replication. In proliferating cells, dl309 replicated efficiently, whereas dl01 / 07 still showed attenuated replication. In summary, our results indicate the intrinsic preference of wild-type adenoviruses for killing proliferating cells, which is an attractive feature for using adenoviruses as oncolytic agents. These results also highlight the need for the use of appropriate growth conditions for primary cells in vitro to distinguish subtle differences in cell killing among various oncolytic viruses.     

Oncolytic adenoviral mutants induce a novel mode of programmed cell death in ovarian cancer

Oncolytic adenoviral mutants have considerable activity in ovarian cancer. However, the mechanisms by which they induce cell death remain uncertain. dl922-947, which contains a 24 bp deletion in E1A CR2, is more potent than both E1A wild-type adenoviruses and the E1B-55K deletion mutant dl1520 (Onyx-015). We investigated the mode of death induced by three E1A CR2-deleted replicating adenoviruses in models of ovarian cancer and also the importance of E3 11.6 (adenovirus death protein) in determining this mode of death. Ovarian cancer cells were infected with dl922-947 (E3 11.6+) and dlCR2 (E3 11.6-). We also generated dlCR2 tSmac, which also encodes the gene for processed Smac/DIABLO. Classical apoptosis does not occur in adenoviral cell death and there is no role for mitochondria. Expression of Smac/DIABLO does not enhance cytotoxicity nor increase apoptotic features. A role for cathepsins and lysosomal membrane permeability was excluded. Autophagy is induced, but is not the mode of death and may act as a cell survival mechanism. There is no evidence of pure necrosis, while the presence of E3 11.6 does not modulate the mode or extent of cell death. Thus, E1A CR2-deleted oncolytic adenoviral cytotoxicity in ovarian cancer may define a novel mode of programmed cell death.     

Enhanced antitumor effect of oncolytic adenovirus expressing interleukin-12 and B7-1 in an immunocompetent murine model.

PURPOSE: We investigated whether an armed viral platform, where lytic property of a viral infection is coupled to viral-mediated delivery of therapeutic genes, could increase the therapeutic potential of a viral-based therapy. EXPERIMENTAL DESIGN: We generated interleukin (IL)-12-expressing oncolytic adenovirus (YKL-IL-12) and IL-12- and B7-1-expressing (YKL-IL12/B7) oncolytic adenovirus. Therapeutic efficacy of these newly engineered adenoviruses was then evaluated in vivo using an immunocompetent mouse bearing murine melanoma B16-F10 tumors. Overall survival was assessed with the Kaplan-Meier method. The induction of immune cell cytotoxicity was assessed by CTL assay, IFN-gamma enzyme-linked immunospot assay, and immunohistochemical studies. RESULTS: YKL-IL12/B7 oncolytic adenovirus, expressing both IL-12 and B7-1, showed a higher incidence of complete tumor regression compared with the analogous oncolytic adenovirus, YKL-1, or IL-12-expressing, YKL-IL12. Significant survival advantage was also seen in response to YKL-IL12/B7. Moreover, IL-12 and IFN-gamma levels produced in tumors treated with YKL-IL12/B7 was significantly greater than those treated with YKL-IL12. The enhanced survival advantage was mediated by the induction of immune cell cytotoxicity. In agreement with these results, massive infiltration of CD4(+) and CD8(+) T cells into tissues surrounding the necrotic area of the tumor was observed following in situ delivery of YKL-IL12/B7. CONCLUSION: Combination of oncolysis and the enhancement of antitumor immune response by oncolytic adenovirus expressing both IL-12 and B7-1 elicits potent antitumor effect and survival advantage.     

E1B55kDa缺陷型腺病毒对人肝癌细胞的杀伤研究

目的 探讨E1B55kDa缺陷型腺病毒dl1520对肝癌细胞的体内外杀伤作用。方法 用dl1520分别感染p53基因型不同的人肝癌细胞,感染后第4天用染色的方法检测存活细胞。用RT－PCR检测细胞内p53和p21^Waf-1基因表达的改变,通过检测腺病毒衣壳蛋白hexon基因的表达证实腺病毒的感染。在SCID裸鼠瘤体内注射dl1520,观察dl1520对肝癌细胞的体内杀伤作用。结果 p53基因缺失的肝癌细胞Hep3B对dl1520诱导的细胞毒性作用最敏感,超过60％的细菌被杀伤,而不足20％的PLC／PRF／5（p53基因突变型）和HepG2(p53基因野生型）肝癌细胞被杀伤。腺病毒感染后,HepG2细胞内p53和p21^Waf-1基因表达水平均明显升高。瘤体内注射dl1520,可显著抑制Hep3B裸鼠移植瘤的生长,而对PLC／PRF／5和HepG2的裸鼠移植瘤则无明显的生长抑制作用。结论 E1B55kDa缺失的腺病毒可以选择性地杀伤p53基因缺失的肝癌细胞,是一种潜在的肿瘤治疗手段。     

Enhanced antitumor efficacy of fiber‐modified,midkine promoter‐regulated oncolytic adenovirus in human malignant mesothelioma

Oncolytic virotherapy using adenoviruses has potential for therapeutic benefits in malignant mesothelioma. However, the downregulation of coxsackie virus/adenovirus receptor (CAR) expression is frequently a critical rate‐limiting factor that impedes the effectiveness of adenovirus serotype 5 (Ad5)‐based vectors in many cancer types. We evaluated CAR (Ad5 receptor) and CD46 (adenovirus serotype 35 [Ad35] receptor) expression in six human malignant mesothelioma cell lines. Very low CAR expression was observed in MSTO‐211H and NCI‐H2052 cells, whereas the other cell lines showed strong expression. In contrast, CD46 was highly expressed in all mesothelioma cell lines. On this basis, we replaced the CAR binding sequence of Ad5 with the CD46 binding sequence of Ad35 in the replication‐defective adenoviruses and the tumor‐specific midkine promoter‐regulated oncolytic adenoviruses. By this fiber modification, the infectivity, virus progeny production, and in vitro cytocidal effects of the adenoviruses were significantly enhanced in low CAR‐expressing MSTO‐211H and NCI‐H2052 cells, also resulting in similar or even higher levels in high CAR‐expressing mesothelioma cell lines. In MSTO‐211H xenograft models, the fiber‐modified oncolytic adenovirus significantly enhanced antitumor effect compared to its equivalent Ad5‐based vector. Our data demonstrate that Ad35 fiber modification of binding tropism in a midkine promoter‐regulated oncolytic Ad5 vector confers transductional targeting to oncolytic adenoviruses, thereby facilitating more effective treatment of malignant mesothelioma.     

Recent advances in genetic modification of adenovirus vectors for cancer treatment

Adenoviruses are widely used to deliver genes to a variety of cell types and have been used in a number of clinical trials for gene therapy and oncolytic virotherapy. However, several concerns must be addressed for the clinical use of adenovirus vectors. Selective delivery of a therapeutic gene by adenovirus vectors to target cancer is precluded by the widespread distribution of the primary cellular receptors. The systemic administration of adenoviruses results in hepatic tropism independent of the primary receptors. Adenoviruses induce strong innate and acquired immunity in vivo. Furthermore, several modifications to these vectors are necessary to enhance their oncolytic activity and ensure patient safety. As such, the adenovirus genome has been engineered to overcome these problems. The first part of the present review outlines recent progress in the genetic modification of adenovirus vectors for cancer treatment. In addition, several groups have recently developed cancer‐targeting adenovirus vectors by using libraries that display random peptides on a fiber knob. Pancreatic cancer‐targeting sequences have been isolated, and these oncolytic vectors have been shown by our group to be associated with a higher gene transduction efficiency and more potent oncolytic activity in cell lines, murine models, and surgical specimens of pancreatic cancer. In the second part of this review, we explain that combining cancer‐targeting strategies can be a promising approach to increase the clinical usefulness of oncolytic adenovirus vectors.     

A novel assay to assess primary human cancer infectibility by replication-selective oncolytic adenoviruses.

PURPOSE: Replication-selective oncolytic adenoviruses hold promise for cancer treatment, but the predictive use of cell lines, dissociated tumor tissue, and animal models for efficacy against primary cancers are unclear. To further evaluate cytotoxicity and the potential for efficacy of replication-competent adenoviruses we therefore developed a novel methodology using primary human cancer specimens ex vivo; ovarian, colon, rectal, and breast carcinomas were included. EXPERIMENTAL DESIGN: Tissue culture conditions were developed to maintain viability of adenocarcinomas ex vivo for 48 hours postsurgery. Explants were infected by replication-competent (wild type 5 and E1A mutant dl922-947) and replication-defective (dl312) adenoviruses; early (E1A) and late (hexon) viral gene expression, alphav integrins, coxsackievirus and adenovirus receptor (CAR) and tissue viability were assessed by immunohistochemistry and histopathology. Viral replication was verified by replication assays on selected samples. RESULTS: Viral gene expression varied dramatically among cancer specimens (n = 41). With Ad5, hexon expression was high in 8 of 11 tested specimens, whereas E1A levels were detectable in 16 of 27 tumor explants. Viral gene expression, distribution, and cytopathic effects were greater postinfection with dl922-947. Specimens that supported early gene expression (E1A) also supported viral replication in 13 of 14 tested cases, determined by recovery of infectious units. As predicted, the replication-defective adenovirus dl312 was not associated with viral gene expression. CONCLUSIONS: Primary human tumor tissue remained viable when cultured ex vivo enabling evaluation of viral mutants in tissue with intact morphology. This assay may have great use in determining treatment-sensitive cancers and assess specific oncolytic mutants in individual cases.     

Two cases of gastric cancer with multiple liver metastases responding to TS-1 with hepatic arterial infusion of CDDP following low-dose 5-FU and CDDP chemotherapy

Case 1: A 77-year-old man was revealed to have type 3 gastric cancer with synchronous liver metastases. He underwent total gastrectomy with lymphatic dissection of D1+a and tubing of the hepatic artery. After surgery, two courses of hepatic arterial infusion of low-dose 5-FU plus CDDP were performed. The patient was discharged, and TS-1 (60 mg/day) was administered from day 1 to 14 followed by 7 days rest as one course. CDDP (10 mg/ body) was infused in the hepatic artery bolus on day 8 and 15 as outpatient treatment. After 8 months, the CEA was decreased from 3,098 ng/dl to 5.4 ng/dl, hepatic metastases were decreased by 85% assessed as a partial response. Case 2: A 71-year-old man was diagnosed with multiple liver metastases 10 months after distal gastrectomy for early gastric cancer. After tubing of the hepatic artery, three courses of hepatic arterial infusion of low-dose 5-FU plus CDDP were performed. TS-1 with hepatic arterial infusion of CDDP was administered using the same regimen as an outpatient. After 4 months, hepatic metastases decreased by 73%. These cases suggest that TS-1 with hepatic arterial infusion of CDDP in an outpatient may be an effective treatment with low toxicities and no damage to QOL in gastric cancer patients with multiple liver metastases.     

Minimal hepatic toxicity of Onyx-015: spatial restriction of coxsackie-adenoviral receptor in normal liver

We administered an adenoviral vector, Onyx-015, into the hepatic artery of patients with metastatic colorectal cancer involving the liver. Thirty-five patients enrolled in this multi-institutional phase I/II trial received up to eight arterial infusions of up to 2 x 10(12) viral particles. Hepatic toxicity was the primary dose-limiting toxicity observed in preclinical models. However, nearly 200 infusions of this adenoviral vector were administered directly into the hepatic artery without significant toxicity. Therefore, we undertook this analysis to determine the impact of repeated adenoviral exposure on hepatic function. Seventeen patients were treated at our institution, providing a detailed data set on the changes in hepatic function following repeated exposure to adenovirus. No changes in hepatic function occurred with the first treatment of Onyx-015 among these patients. Transient increases in transaminase levels occurred in one patient starting with the second infusion and transient increases in bilirubin was observed in two patients starting with the fifth treatment. These changes occurred too early to be explained by viral-mediated lysis of hepatocytes. In addition, viremia was observed starting 3-5 days after the viral infusion in half of the patient, but was not associated with hepatic toxicity. To further understand the basis for the minimal hepatic toxicity of adenoviral vectors, we evaluated the replication of adenovirus in primary hepatocytes and tumor cells in culture and the expression of the coxsackie-adenoviral receptor (CAR) in normal liver and colon cancer metastatic to the liver. We found that adenovirus replicates poorly in primary hepatocytes but replicates efficiently in tumors including tumors derived from hepatocytes. In addition, we found that CAR is localized at junctions between hepatocytes and is inaccessible to hepatic blood flow. CAR is not expressed on tumor vasculature but is expressed on tumor cells. Spatial restriction of CAR to the intercellular space in normal liver and diminished replication of adenovirus in hepatocytes may explain the minimal toxicity observed following repeated hepatic artery infusions with Onyx-015.     

Clinical trial of E1B-deleted adenovirus (dl1520) gene therapy for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. The prognosis of HCC is poor and current therapies are largely ineffective. Genetic abnormalities are commonly seen in HCC tumors particularly with inactivation of the p53 tumor suppressor. Gene therapy with E1B-deleted (dl1520) adenovirus could be of therapeutic value as it offers the potential of tumor growth control in patients with p53 mutation. Ten patients with posthepatitis cirrhosis and histologically proven HCC were enrolled into an open label, randomized prospective study. Randomization was to receive either percutaneous ethanol injection (control group) or dl1520. Toxicity and complications in the ethanol group were pain and fever, whereas in the gene therapy group complications were minimal. Grade I-II toxicity fever, stable performance status, and no significant rise in liver enzymes were observed in patients treated with dl1520. Analysis of patients' response to treatment in the gene therapy group showed one patient with a partial response and four patients with progressive disease. In the ethanol-treated group two patients had stable disease and three patients showed disease progression. In conclusion, this study showed that the adenovirus was well tolerated, but did not seem to offer significant tumor control. Although only a small number of patients were treated here it appears that more effective vectors are needed to achieve a useful clinical impact.     

Potentiation of radiation therapy by the oncolytic adenovirus dl1520 (ONYX-015) in human malignant glioma xenografts

In spite of aggressive surgery, irradiation and/or chemotherapy, treatment of malignant gliomas remains a major challenge in adults and children due to high treatment failure. We have demonstrated significant cell lysis and antitumour activity of the E1B-55 kDa-gene-deleted adenovirus ONYX-015 (dl1520, CI-1042; ONYX Pharmaceuticals) in subcutaneous human malignant glioma xenografts deriving from primary tumours. Here, we show the combined efficacy of this oncolytic therapy with radiation therapy. Total body irradiation (5 Gy) of athymic nude mice prior to intratumoral injections of ONYX-015 1 x 10(8) PFU daily for 5 consecutive days yielded additive tumour growth delays in the p53 mutant xenograft IGRG88. Radiation therapy was potentiated in the p53 functional tumour IGRG121 with a 'subtherapeutic' dose of 1 x 10(7) PFU daily for 5 consecutive days, inducing significant tumour growth delay, 90% tumour regression and 50% tumour-free survivors 4 months after treatment. These potentiating effects were not due to increased adenoviral infectivity or replication. Furthermore, cell lysis and induction of apoptosis, the major mechanisms for adenoviral antitumour activity, did not play a major role in the combined treatment strategy. Interestingly, the oncolytic adenovirus seemed to accelerate radiation-induced tumour fibrosis. Potentiating antitumour activity suggests the development of this combined treatment for these highly malignant tumours.