Dual promoter-controlled oncolytic adenovirus CG5757 has strong tumor selectivity and significant antitumor efficacy in preclinical models.

PURPOSE: Transcriptionally controlled oncolytic adenovirus CG5757 is engineered with two tumor-specific promoters from E2F-1 and human telomerase reverse transcriptase genes. This virus has broad anticancer spectrum and higher specificity. The objective of the current study is to show its antitumor selectivity and therapeutic potential. EXPERIMENTAL DESIGN: The antitumor specificity of E2F-1 and human telomerase reverse transcriptase promoters was evaluated in a panel of tumor and normal cells. Under the control of these promoters, the tumor-selective expression of E1a and E1b genes was evaluated. Further in vitro antitumor specificity and potency of this virus were characterized by viral replication and cytotoxicity assays followed by a newly developed ex vivo tumor culture assay. Subsequently, in vivo antitumor efficacy and toxicology studies were carried out to assess the therapeutic potential of this oncolytic agent. RESULTS: In a broad panel of cells, E2F-1 and human telomerase reverse transcriptase promoters were activated in a tumor-selective manner. Under the control of these promoters, expression of E1a and E1b genes appears only in tumor cells. This specificity is extended to viral replication and hence the cytotoxicity in a broad range of cancer cells. Furthermore, CG5757 only replicates in cancer tissues but not in normal tissues that are derived from clinical biopsies. The safety profile was further confirmed in in vivo toxicology studies, and strong efficacy was documented in several tumor xenograft models after CG5757 was given via different routes and regimens. CONCLUSIONS: CG5757 has strong antitumor selectivity and potency. It has low toxicity and has great potential as a therapeutic agent for different types of cancers.

Anti-HER2 immunoliposomes: enhanced efficacy attributable to targeted delivery.

PURPOSE: Anti-HER2 immunoliposomes combine the tumor-targeting of certain anti-HER2 monoclonal antibodies (MAbs) with the pharmacokinetic and drug delivery capabilities of sterically stabilized liposomes. We previously showed that anti-HER2 immunoliposomes bind efficiently to and internalize in HER2-overexpressing cells in vitro, resulting in intracellular drug delivery. EXPERIMENTAL DESIGN: Here we describe the pharmacokinetics and therapeutic efficacy of anti-HER2 immunoliposomes containing doxorubicin (dox) in a series of animal models. RESULTS: Immunoliposomes displayed long circulation that was identical to that of sterically stabilized liposomes in single- and multiple-dose studies in normal rats. Anti-HER2 immunoliposome-dox produced marked therapeutic results in four different HER2-overexpressing tumor xenograft models, including growth inhibition, regression, and cures. These results demonstrated that encapsulation of dox in anti-HER2 immunoliposomes greatly increased its therapeutic index, both by increasing antitumor efficacy and by reducing systemic toxicity. Immunoliposome-dox was significantly superior to all other treatment conditions tested, including free dox, liposomal dox, and anti-HER2 MAb (trastuzumab). When compared with liposomal dox in eight separate therapy studies in HER2-overexpressing models, immunoliposome delivery produced significantly superior antitumor efficacy in each study (P < 0.0001 to 0.04). Anti-HER2 immunoliposome-dox containing either recombinant human MAb HER2-Fab' or scFv C6.5 yielded comparable therapeutic efficacy. Cure rates for immunoliposome-dox reached 50% (11 of 21) with optimized immunoliposomes and Matrigel-free tumors and overall was 16% (18 of 115) versus no cures (0 of 124) with free dox or liposomal dox. Finally, anti-HER2 immunoliposome-dox was also superior to combinations consisting of free MAb plus free dox or free MAb plus liposomal dox. CONCLUSIONS: Anti-HER2 immunoliposomes produced enhanced antitumor efficacy via targeted delivery.

Pegylated liposomal doxorubicin: proof of principle using preclinical animal models and pharmacokinetic studies.

Encapsulation of doxorubicin in polyethylene glycol-coated liposomes (Doxil/Caelyx [PLD]), was developed to enhance the safety and efficacy of conventional doxorubicin. The liposomes alter pharmacologic and pharmacokinetic parameters of conventional doxorubicin so that drug delivery to the tumor is enhanced while toxicity normally associated with conventional doxorubicin is decreased. In animals and humans, pharmacokinetic advantages of PLD include an increased area under the plasma concentration-time curve, longer distribution half-life, smaller volume of distribution, and reduced clearance. In preclinical models, PLD produced remission and cure against many cancers including tumors of the breast, lung, ovaries, prostate, colon, bladder, and pancreas, as well as lymphoma, sarcoma, and myeloma. It was also found to be effective as adjuvant therapy. In addition, it was found to cross the blood-brain barrier and induce remission in tumors of the central nervous system. Increased potency over conventional doxorubicin was observed and, in contrast to conventional doxorubicin, PLD was equally effective against low- and high-growth fraction tumors. The combination of PLD with vincristine or trastuzumab resulted in additive effects and possible synergy. PLD appeared to overcome multidrug resistance, possibly as the result of increased intracellular concentrations and an interaction between the liposome and P-glycoprotein function. On the basis of pharmacokinetic and preclinical studies, PLD, either alone or as part of combination therapy, has potential applications to treat a variety of cancers.

The role of the liposomal anthracyclines and other systemic therapies in the management of advanced breast cancer.

For patients whose breast cancers are not responsive to endocrine therapy, there are a large number of cytotoxic drugs that will induce a response. In spite of the introduction of new, very active drugs such as the taxanes, vinorelbine, capecitabine, gemcitabine, and trastuzumab, the anthracyclines are still as active as any--and more active than most--drugs used to treat breast cancer. Their inclusion in combinations to treat early and advanced disease prolongs survival. However, they cause nausea, vomiting, alopecia, myelosuppression, mucositis, and cardiomyopathies. There is no evidence that increasing the dose of conventional anthracyclines or any other of the cytotoxics beyond standard doses will improve outcomes. Schedule may be more important than dose in determining the benefit of cytotoxics used to treat breast cancer. Weekly schedules and continuous infusions of 5-fluorouracil and doxorubicin may have some advantages over more intermittent schedules. Liposomal formations of doxorubicin reduce toxicity, including cardiotoxicity; theoretically they should also be more effective because of better targeting of tumor over normal tissues. Both pegylated liposomal doxorubicin (Doxil/Caelyx [PLD]) and liposomal doxorubicin (Myocet [NPLD]) appeared to be as effective as conventional doxorubicin and much less toxic in multiple phase II and phase III studies. PLD has been evaluated in combinations with cyclophosphamide, the taxanes, vinorelbine, gemcitabine, and trastuzumab, and NPLD has been evaluated in combination with cyclophosphamide and trastuzumab. Both liposomal anthracyclines are less cardiotoxic than conventional doxorubicin. The optimal dose of PLD is lower than that of conventional doxorubicin or NPLD. Patients treated with PLD have almost no alopecia, nausea, or vomiting, but its use is associated with stomatitis and hand-foot syndrome, which can be avoided or minimized with the use of proper dose-schedules. In contrast, the optimal dose-schedule of NPLD is nearly identical to that of conventional doxorubicin. The toxicity profile of NPLD is similar to that of conventional doxorubicin, but toxicities are less severe and NPLD is better tolerated than conventional doxorubicin at higher doses.

STEALTH liposome-encapsulated cisplatin (SPI-77) versus carboplatin as adjuvant therapy for spontaneously arising osteosarcoma (OSA) in the dog: a randomized multicenter clinical trial.

PURPOSE: This trial was designed to compare the efficacy of adjuvant STEALH liposome-encapsulated cisplatin (SPI-77) to "standard-of-care" carboplatin therapy in dogs with osteosarcoma (OSA) in the context of a randomized study design. METHODS: The study included 40 pet dogs with spontaneously arising OSA which were randomized to receive SPI-77 (350 mg/m(2) i.v. every 3 weeks for four treatments) or carboplatin (300 mg/m(2) i.v. every 3 weeks for four treatments) along with amputation of the affected limb. Median disease-free (DFS) and overall survival (OS) were compared using standard life-table analysis. RESULTS: The median follow-up was 693 days (range 321-730 days). Of 38 dogs eligible for follow-up, 25 were dead of their disease, 9 were alive and disease-free (8 receiving SPI-77, 1 receiving carboplatin; P=0.02), 2 were free of disease when they were lost to follow-up at 321 and 395 days, and 2 had died of an unrelated disease. The median DFS times for dogs treated with SPI-77 and carboplatin were 156 and 123 days, respectively ( P=0.19). The median OS times for dogs treated with SPI-77 and carboplatin were 333 and 207 days, respectively ( P=0.18). CONCLUSIONS: While STEALTH liposome encapsulation of cisplatin allowed the safe administration of five times the maximally tolerated dose of free cisplatin to dogs without concurrent hydration protocols, this did not translate into significantly prolonged DFS or OS. However, a larger proportion of dogs receiving SPI-77 enjoyed long-term DFS when compared with dogs receiving carboplatin.

Systemic and tumor disposition of platinum after administration of cisplatin or STEALTH liposomal-cisplatin formulations (SPI-077 and SPI-077 B103) in a preclinical tumor model of melanoma.

PURPOSE: SPI-077 and SPI-077 B103 are formulations of cisplatin encapsulated in pegylated STEALTH liposomes that accumulate in tumors. However, the extent to which active platinum (Pt) is released from the liposome is unknown. Thus, we evaluated the disposition of encapsulated and released Pt in plasma and tumors after administration of STEALTH liposomal and nonliposomal cisplatin. METHODS: Cisplatin (10 mg/kg), SPI-077 (10 mg/kg), and SPI-077 B103 (5 mg/kg) were administered i.v. to mice bearing B16 murine melanoma tumors. Microdialysis probes were placed into the right and left sides of each tumor, and serial samples were collected from tumor extracellular fluid (ECF) after administration of each agent. After each microdialysis procedure, tumor samples were obtained at each probe site to measure total Pt and Pt-DNA adducts. In a separate study, serial plasma samples (three mice per time point) were obtained. Unbound Pt in tumor ECF and plasma, and total Pt in tumor homogenates were measured by flameless atomic absorption spectrophotometry. Area under the tumor ECF (AUC(ECF)) concentration versus time curves of unbound Pt were calculated. Intrastrand GG (Pt-GG) and AG (Pt-AG) Pt-DNA adducts were measured via (32)P-postlabeling. RESULTS: Mean+/-SD peak concentrations of total Pt in tumor homogenates after administration of cisplatin, SPI-077, and SPI-077 B-103 were 3.2+/-1.9, 11.9+/-3.0, and 3.5+/-0.3 microg/g, respectively. After cisplatin, mean+/-SD AUC(ECF) of unbound Pt was 0.72+/-0.46 microg/ml.h. There was no detectable unbound Pt in tumor ECF after SPI-077 or SPI-077 B-103 treatment. Mean+/-SD peak concentration of Pt-GG DNA adducts after administration of cisplatin, SPI-077, and SPI-077 B-103 were 13.1+/-3.3, 3.5+/-1.3, and 2.1+/-0.3 fmol Pt/microg DNA, respectively. CONCLUSION: This study suggests that more SPI-077 and SPI-077 B103 distribute into tumors, but release less Pt into tumor ECF, and form fewer Pt-DNA adducts than does cisplatin.

Characterization of a novel, trastuzumab resistant human breast cancer cell line.

HER2-positive breast cancers represent a distinct phenotype and are intrinsically more aggressive than HER2-negative tumors. Although HER2-targeted therapies have been rationally developed, resistance to these treatments represents a process understood poorly. There are few experimental models that allow studying the molecular mechanism of resistance. Our aim was to characterize a trastuzumab resistant breast cancer cell line (B585) that was established from an invasive ductal carcinoma. B585 grows only in immunodeficient mice as a xenograft. CGH and FISH were used to define cytogenetic alterations, gene-expression analysis and immunohistochemistry were applied to detect RNA and protein expression. By array-CGH focused amplifications were identified for C-MYC, EGFR, ErbB2, CCND1 and TOP2-A oncogenes. ErbB2 was co-amplified with TOP2-A. mRNA overexpression was detected for the amplified genes. ErbB2 protein was overexpressed and showed heterogeneous distribution. In summary, molecular cytogenetic analysis and expression profiling of B585 revealed several new alterations. Based on the experiments performed in SCID mice and the genotypic/phenotypic characteristics, this new in vivo breast cancer xenograft is a valuable model to investigate molecular mechanism of trastuzumab resistance.

MetMAb, the one-armed 5D5 anti-c-Met antibody, inhibits orthotopic pancreatic tumor growth and improves survival.

The hepatocyte growth factor (HGF) and its receptor, c-Met, have been implicated in driving proliferation, invasion, and poor prognosis in pancreatic cancer. Here, we investigated the expression of HGF and c-Met in primary pancreatic cancers and described in vitro and in vivo models in which MetMAb, a monovalent antibody against c-Met, was evaluated. First, expression of HGF and MET mRNA was analyzed in 59 primary pancreatic cancers and 51 normal samples, showing that both factors are highly expressed in pancreatic cancer. We next examined HGF responsiveness in pancreatic cancer lines to select lines that proliferate in response to HGF. Based on these studies, two lines were selected for further in vivo model development: BxPC-3 (c-Met(+), HGF(-)) and KP4 (c-Met(+), HGF(+)) cells. As BxPC-3 cells are responsive to exogenous HGF, s.c. tumor xenografts were grown in a paracrine manner with purified human HGF provided by osmotic pumps, wherein MetMAb treatment significantly inhibited tumor growth. KP4 cells are autocrine for HGF and c-Met, and MetMAb strongly inhibited s.c. tumor growth. To better model pancreatic cancer and to enable long-term survival studies, an orthotopic model of KP4 was established. MetMAb significantly inhibited orthotopic KP4 tumor growth in 4-week studies monitored by ultrasound and also improved survival in 90-day studies. MetMAb significantly reduced c-Met phosphorylation in orthotopic KP4 tumors with a concomitant decrease in Ki-67 staining. These data suggest that the HGF/c-Met axis plays an important role in the progression of pancreatic cancer and that targeting c-Met therein may have therapeutic value.