Merja Särkioja

Oncolytic Adenovirus Coding for Granulocyte Macrophage Colony-Stimulating Factor Induces Antitumoral Immunity in Cancer Patients

Granulocyte macrophage colony-stimulating factor (GMCSF) can mediate antitumor effects by recruiting natural killer cells and by induction of tumor-specific cytotoxic T-cells through antigen-presenting cells. Oncolytic tumor cell-killing can produce a potent costimulatory danger signal and release of tumor epitopes for antigen-presenting cell sampling. Therefore, an oncolytic adenovirus coding for GMCSF was engineered and shown to induce tumor-specific immunity in an immunocompetent syngeneic hamster model. Subsequently, 20 patients with advanced solid tumors refractory to standard therapies were treated with Ad5-D24-GMCSF. Of the 16 radiologically evaluable patients, 2 had complete responses, 1 had a minor response, and 5 had disease stabilization. Responses were frequently seen in injected and noninjected tumors. Treatment was well tolerated and resulted in the induction of both tumor-specific and virus-specific immunity as measured by ELISPOT and pentamer analysis. This is the first time that oncolytic virus-mediated antitumor immunity has been shown in humans. Ad5-D24-GMCSF is promising for further clinical testing.

Combination of gemcitabine and Ad5/3-Δ24, a tropism modified conditionally replicating adenovirus, for the treatment of ovarian cancer

Conditionally replicating adenoviruses (CRAds) represent a novel approach for the treatment of cancers resistant to conventional therapies. The efficacy of CRAds might be further improved by using chemotherapeutic agents in a multimodal antitumor approach. We have evaluated the use of Ad5/3-Δ24, a serotype 3 receptor targeted Rb/p16 pathway selective CRAd, in combination with gemcitabine against human ovarian adenocarcinoma. The combination of these agents showed synergistic cell killing in vitro compared to single treatments. However, the effect was dependent on dose and sequencing of the agents. Our results also indicate that gemcitabine reduces the initial rate of Ad5/3-Δ24 replication without affecting the total amount of virus produced. Possible reasons for synergy between Ad5/3-Δ24 and gemcitabine include the chemosensitizing activity of E1A and/or altered replication kinetics. In an orthotopic murine model of peritoneally disseminated ovarian cancer, the combination increased the survival of mice over either agent alone, and almost 60% of treated mice were cured. Sequencing of the agents was critical for toxicity versus efficacy. Mice remained free from intraperitoneal disease, but some succumbed to treatment-related hepatic or bone marrow toxicity. This suggests that improved efficacy may uncover treatment-related toxicity, which needs to be monitored closely in clinical trials.

Oncolytic Adenovirus ICOVIR-7 in Patients with Advanced and Refractory Solid Tumors

Purpose: Twenty-one patients with cancer were treated with a single round of oncolytic adenovirus ICOVIR-7. Experimental Design: ICOVIR-7 features an RGD-4C modification of the fiber HI-loop of serotype 5 adenovirus for enhanced entry into tumor cells. Tumor selectivity is mediated by an insulator, a modified E2F promoter, and a Rb-binding site deletion of E1A, whereas replication is optimized with E2F binding hairpins and a Kozak sequence. ICOVIR-7 doses ranged from 2 × 1010 to 1 × 1012 viral particles. All patients had advanced and metastatic solid tumors refractory to standard therapies. Results: ICOVIR-7 treatment was well tolerated with mild to moderate fever, fatigue, elevated liver transaminases, chills, and hyponatremia. One patient had grade 3 anemia but no other serious side effects were seen. At baseline, 9 of 21 of patients had neutralizing antibody titers against the ICOVIR-7 capsid. Treatment resulted in neutralizing antibody titer induction within 4 weeks in 16 of 18 patients. No elevations of serum proinflammatory cytokine levels were detected. Viral genomes were detected in the circulation in 18 of 21 of patients after injection and 7 of 15 of the samples were positive 2 to 4 weeks later suggesting viral replication. Conclusions: Overall, objective evidence of antitumor activity was seen in 9 of 17 evaluable patients. In radiological analyses, 5 of 12 evaluable patients had stabilization or reduction in tumor size. These consisted of one partial response, two minor responses and two cases of stable disease, all occurring in patients who had progressive disease before treatment. In summary, ICOVIR-7 treatment is apparently safe, resulting in anticancer activity, and is therefore promising for further clinical testing. Clin Cancer Res; 16(11); 3035–43. ©2010 AACR.

Prolonged systemic circulation of chimeric oncolytic adenovirus Ad5/3-Cox2L-D24 in patients with metastatic and refractory solid tumors

Eighteen patients with refractory and progressive solid tumors were treated with a single round of triple modified oncolytic adenovirus (Ad5/3-Cox2L-D24). Ad5/3-Cox2L-D24 is the first non-Coxsackie-adenovirus receptor-binding oncolytic adenovirus used in humans. Grades 1–2 flu-like symptoms, fever, and fatigue were seen in most patients, whereas transaminitis or thrombocytopenia were seen in some. Non-hematological grades 3–5 side effects were seen in one patient with grade 3 ileus. Treatment resulted in high neutralizing antibody titers within 3 weeks. Virus appeared in serum 2–4 days after treatment in 83% of patients and persisted for up to 5 weeks. One out of five radiologically evaluable patients had partial response (PR), one had minor response (MR), and three had progressive disease (PD). Two patients scored as PD had a decrease in tumor density. Tumor reductions not measurable with Response Evaluation Criteria In Solid Tumors (RECIST) were seen in a further four patients. PR, MR, stable disease, and PD were seen in 12, 23.5, 35, and 29.5% of tumor markers analyzed, respectively (N=17). Ad5/3-Cox2L-D24 appears safe for treatment of cancer in humans and extended virus circulation results from a single treatment. Objective evidence of anti-tumor activity was seen in 11/18 (61%) of patients. Clinical trials are needed to extend these findings.

Treatment of metastatic renal cancer with capsid-modified oncolytic adenoviruses

Renal cancer is a common and deadly disease that lacks curative treatments when metastatic. Here, we have used oncolytic adenoviruses, a promising developmental approach whose safety has recently been validated in clinical trials. Although preliminary clinical efficacy data exist for selected tumor types, potency has generally been less than impressive. One important reason may be that expression of the primary receptor, coxsackie-adenovirus receptor, is often low on many or most advanced tumors, although not evaluated in detail with renal cancer. Here, we tested if fluorescence-assisted cell sorting could be used to predict efficacy of a panel of infectivity-enhanced capsid-modified marker gene expressing adenoviruses in renal cancer cell lines, clinical specimens, and subcutaneous and orthotopic murine models of peritoneally metastatic renal cell cancer. The respective selectively oncolytic adenoviruses were tested for killing of tumor cells in these models, and biodistribution after locoregional delivery was evaluated. In vivo replication was analyzed with noninvasive imaging. Ad5/3-Δ24, Ad5-Δ24RGD, and Ad5.pK7-Δ24 significantly increased survival of mice compared with mock or wild-type virus and 50% of Ad5/3-Δ24 treated mice were alive at 320 days. Because renal tumors are often highly vascularized, we investigated if results could be further improved by adding bevacizumab, a humanized antivascular endothelial growth factor antibody. The combination was well tolerated but did not improve survival, suggesting that the agents may be best used in sequence instead of together. These results set the stage for clinical testing of oncolytic adenoviruses for treatment of metastatic renal cancer currently lacking other treatment options. [Mol Cancer Ther 2007;6(10):2728–36]

A heparan sulfate-targeted conditionally replicative adenovirus, Ad5.pk7-Δ24, for the treatment of advanced breast cancer

Conditionally replicating adenoviruses (CRAds) that replicate in tumor but less in normal cells are promising anticancer agents. A major determinant of their potency is their capacity for infecting target cells. The primary receptor for serotype 5 adenovirus (Ad5), the most widely used serotype in gene therapy, is the coxsackie-adenovirus receptor (CAR). CAR is expressed variably and often at low levels in various tumor types including advanced breast cancer. We generated a novel p16/retinoblastoma pathway-dependent CRAd, Ad5.pK7-Δ24, with a polylysine motif in the fiber C-terminus, enabling CAR-independent binding to heparan sulfate proteoglycans (HSPG). Ad5.pK7-Δ24 mediated effective oncolysis of all breast cancer cell lines tested. Further, we utilized noninvasive, fluorescent imaging for analysis of antitumor efficacy in an orthotopic model of advanced hormone refractory breast cancer. A therapeutic benefit was seen following both intratumoral and intravenous delivery. Murine biodistribution similar to Ad5, proven safe in trials, suggests feasibility of clinical safety testing. Interestingly, upregulation of CAR was seen in low-CAR M4A4-LM3 breast cancer cells in vivo, which resulted in better than expected efficacy also with an isogenic CRAd with an unmodified capsid. These results suggest utility of Ad5.pK7-Δ24 and the orthotopic model for further translational studies.

Changing the adenovirus fiber for retaining gene delivery efficacy in the presence of neutralizing antibodies

Prior infection has primed most adult humans for a rapid neutralizing antibody (NAb) response when re-exposed to adenovirus. NAb induction can severely limit the efficacy of systemic re-administration of adenoviral gene therapy. We hypothesized that changing the fiber knob could overcome NAb. Immune-competent mice were exposed to serotype 5 adenovirus (Ad5)(GL), Ad5/3luc1, Ad5lucRGD or Ad5pK7(GL). Mice immunized with Ad5(GL) featured reduced intravenous Ad5(GL) gene transfer to most organs, including the liver, lung and spleen. Ad5(GL) gene transfer was affected much less by exposure to capsid-modified viruses. Anti-Ad5(GL) NAb blocked intravenous Ad5(GL) gene transfer to orthotopic lung cancer xenografts, whereas capsid-modified viruses were not affected. When gene transfer to fresh cancer and normal lung explants was analyzed, we found that capsid-modified viruses allowed effective gene delivery to tumors in the presence of anti-Ad5(GL) NAb, whereas Ad5(GL) was blocked. In contrast, crossblocking by NAbs induced by different viruses affected gene delivery to normal human lung explants, suggesting the importance of non-fiber-knob-mediated infection mechanisms. We conclude that changing the adenovirus fiber knob is sufficient to allow a relative degree of escape from preexisting NAb. If confirmed in trials, this approach might improve the efficacy of re-administration of adenoviral gene therapy to humans.

Utility of TK/GCV in the context of highly effective oncolysis mediated by a serotype 3 receptor targeted oncolytic adenovirus

Arming oncolytic adenoviruses with therapeutic transgenes and enhancing transduction of tumor cells are useful strategies for eradication of advanced tumor masses. Herpes simplex virus thymidine kinase (TK) together with ganciclovir (GCV) has been promising when coupled with viruses featuring low oncolytic potential, but their utility is unknown in the context of highly effective infectivity-enhanced viruses. We constructed Ad5/3-Δ24-TK-GFP, a serotype 3 receptor-targeted, Rb/p16 pathway-selective oncolytic adenovirus, where a fusion gene encoding TK and green fluorescent protein (GFP) was inserted into 6.7K/gp19K-deleted E3 region. Ad5/3-Δ24-TK-GFP killed ovarian cancer cells effectively, which correlated with GFP expression. Delivery of GCV immediately after infection abrogated viral replication, which might have utility as a safety switch. Due to the bystander effect, killing of some cell lines in vitro was enhanced by GCV regardless of timing. In murine models of metastatic ovarian cancer, Ad5/3-Δ24-TK-GFP improved antitumor efficacy over the respective replication-deficient virus with GCV. However, GCV did not further enhance efficacy of Ad5/3-Δ24-TK-GFP in vivo. Simultaneous detection of tumor load and virus replication with bioluminescence and fluorescence imaging provided insight into the in vivo kinetics of oncolysis. In summary, TK/GCV may not add antitumor activity in the context of highly potent oncolysis.

Infectivity-Enhanced Adenoviruses Deliver Efficacy in Clinical Samples and Orthotopic Models of Disseminated Gastric Cancer

Purpose: Metastatic gastric cancer remains a common and devastating disease without curative treatment. Recent proof-of-concept clinical trials have validated gene therapy with adenoviruses as an effective and safe modality for the treatment of cancer. However, expression of the primary coxsackie-adenovirus receptor is variable in advanced cancers, and therefore, the use of heterologous receptors could be advantageous. Experimental Design: Here, we used capsid-modified adenoviruses for increasing the transduction and subsequent antitumor efficacy. 5/3 chimeric viruses have a serotype 3 knob which allows binding to a receptor distinct from coxsackie-adenovirus receptor. The fiber of Ad5lucRGD is modified with an integrin-targeted motif. Polylysine motifs, pK7 and pK21, bind to heparan sulfates. Oncolytic adenoviruses replicate in and kill tumor cells selectively. Gastric cancer cell lines and fresh clinical samples from patients were infected with transductionally targeted viruses. Capsid-modified oncolytic adenoviruses were used in cell killing experiments. To test viral transduction and therapeutic efficacy in vivo, we developed orthotopic mouse models featuring i.p. disseminated human gastric cancer, which allowed the evaluation of biodistribution and antitumor efficacy in a system similar to humans. Results: Capsid modifications benefited gene transfer efficiency and cell killing in gastric cancer cell lines and clinical samples in vitro and in vivo. Modified oncolytic adenoviruses significantly increased the survival of mice with orthotopic gastric cancer. Conclusions: These preclinical data set the stage for the clinical evaluation of safety and efficacy in patients with disease refractory to current modalities.

Systemic efficacy of oncolytic adenoviruses in imagable orthotopic models of hormone refractory metastatic breast cancer

Conditionally replicating oncolytic adenoviruses represent a promising developmental strategy for the treatment of cancer refractory to current treatments, such as hormone refractory metastatic breast cancer. In clinical cancer trials, adenoviral agents have been well tolerated, but gene transfer has been insufficient for clinical benefit. One of the main reasons may be the deficiency of the primary adenovirus receptor, and therefore viral capsid modifications have been employed. Another obstacle to systemic delivery is rapid clearance of virus by hepatic Kupffer cells and subsequent inadequate bioavailability. In this study, we compared several capsid‐modified oncolytic adenoviruses for the treatment of breast cancer with and without Kupffer cell inactivation. Replication deficient capsid‐modified viruses were analyzed for their gene transfer efficacy in vitro in breast cancer cell lines and clinical samples and in vivo in orthotopic models of breast cancer. The effect of Kupffer cell depleting agents on gene transfer efficacy in vivo was evaluated. An aggressive lung metastatic model was developed to study the effect of capsid‐modified oncolytic adenoviruses on survival. Capsid‐modified viruses displayed increased gene transfer and cancer cell killing in vitro and resulted in increased survival in an orthotopic model of lung metastatic breast cancer in mice. Biodistribution of viruses was favorable, tumor burden and treatment response could be monitored repeatedly. Kuppfer cell inactivation led to enhanced systemic gene delivery, but did not increase the survival of mice. These results facilitate clinical translation of oncolytic adenoviruses for the treatment of hormone refractory metastatic breast cancer.