Reduction In Tumor Blood Flow Research Articles

Peptide-conjugated chlorin-type photosensitizer binds neuropilin-1 in vitro and in vivo

The strategy developed aims to favor the vascular effect of photodynamic therapy (PDT) by targeting tumor vasculature. This approach is considered by coupling a photosensitizer (PS) to an heptapeptide targeting neuropilin-1 (NRP-1). We previously demonstrated that this new conjugated PS, which binds to recombinant NRP-1 protein, was a much more potent PS compared to the non-conjugated PS in human umbilical vein endothelial cells (HUVEC) expressing NRP-1, due to the coupling of the peptide moiety. To argue the involvement of NRP-1 in the conjugated PS cellular uptake, MDA-MB-231 breast cancer cells were used, strongly over-expressing NRP-1 receptor, and we evidenced a significant decrease of the conjugated PS uptake after RNA interference-mediated silencing of NRP-1. In mice xenografted ectopically with U87 human malignant glioma cells, we demonstrated that only the conjugated PS allowed a selective accumulation in endothelial cells lining tumor vessels. Vascular endothelial growth factor (VEGF) plasma and tumor levels could not prevent the recognition of the conjugate by NRP-1. The vascular effect induced by the conjugated PS, was characterized by a reduction in tumor blood flow around 50% during PDT. In vivo, the photodynamic efficiency with the conjugated PS induced a statistically significant tumor growth delay compared to the non-coupled PS. The peptide-conjugated chlorin-type PS uptake involves NRP-1 and this targeting strategy favors the vascular effect of PDT in vivo.

Diffuse intrahepatic recurrence after percutaneous radiofrequency ablation for solitary and small hepatocellular carcinoma

Two patients developed segmental, diffuse intrahepatic recurrence after percutaneous radiofrequency ablation (RFA) to treat a primary, solitary, and small (2.5cm) hepatocellular carcinoma (HCC). Despite the size of the HCC, levels of the tumor markers (α-fetoprotein, α-fetoprotein-L3%, and des-γ-carboxyprothrombin) were all elevated before RFA, and tumors in both patients were contiguous with a major branch of the portal vein. Tumor biopsies of both patients revealed moderately differentiated HCC but diagnostic imaging showed an area of reduced tumor blood flow, suggesting a poorly differentiated component. Since early detection of post-RFA malignancies by standard ultrasonography and contrast-enhanced computed tomography was difficult, the most sensitive indicator of recurrence in these two patients was the elevated tumor markers. The diffuse intrahepatic recurrence was thought to be caused by increased intratumoral pressure during RFA, resulting in the dissemination of cancer cells through the contiguous portal vein. The clinical course of these tumors indicate that the choice of RFA should be carefully considered when treating specific subtype of HCC that is adjacent to main portal vein branch and involves a possible poorly differentiated component and that surgical resection or combinations of RFA with other treatment modalities such as transcatheter arterial chemoembolization should be considered as alternative treatment strategies.

Abstract No. 193: Combination Therapy of Radiofrequency Ablation and Bevacizumab in the Treatment of Ectopic Hepatocellular Carcinoma

Radiofrequency ablation (RFA) has a high local control rate for lesions < 4 cm; however, it is limited in the treatment of larger tumors, in part due to tumor blood flow that dissipates local heat and limits ablation diameter. Reducing tumor blood flow prior to RFA may increase ablation diameter and improve treatment outcomes in patients with lesions > 4 cm. It has been previously shown that a systemic antiangiogenic agent can improve tumor ablation but the optimum timing between applying antiangiogenic therapy and ablation is unknown.

Optimal Strategies for Combining Transcatheter Arterial Chemoembolization and Radiofrequency Ablation in Rabbit VX2 Hepatic Tumors

To determine the optimum combination strategy of transcatheter arterial chemoembolization and radiofrequency (RF) ablation in an experimentally induced hepatic tumor model. Twenty-five New Zealand White rabbits with VX2 carcinoma-induced hepatic tumors were randomly divided into five treatment groups, which received (i) chemoembolization followed 15 minutes later by RF ablation; (ii) RF ablation followed by chemoembolization; (iii) chemoembolization alone; (iv) RF ablation alone; and (v) bland embolization followed by RF ablation. Animals were euthanized at 48 hours to determine tumor infarction and coagulation, which were compared with analysis of variance. Representative histopathologic slides were compared. Significantly larger areas of coagulation were produced by chemoembolization followed by RF ablation (22.0 cm(3) +/- 7.7) compared with RF ablation followed by chemoembolization (13.1 cm(3) +/- 3.2) and RF ablation alone (10.0 cm(3) +/- 4.5; P < .05). RF ablation followed by chemoembolization showed larger treatment areas than chemoembolization alone (25.0 cm(3) +/- 9.6 vs 12.1 cm(3) +/- 4.6; P < .001), with chemotherapeutic agent preferentially depositing around the coagulation zone. Histopathologic analysis revealed greater vascular thrombosis and necrosis and reduced islands of viable tumor cells in the chemoembolization/RF ablation group versus the groups treated with chemoembolization alone or bland embolization/RF ablation. Larger treatment volumes were produced when chemoembolization was performed before RF ablation than when RF ablation preceded chemoembolization or when RF ablation or chemoembolization were performed alone. Larger treatment volumes were also produced when chemoembolization rather than bland embolization was performed before RF ablation, indicating the importance and synergy of the chemotherapeutic regimen. These results suggest that the reduction of tumor blood flow combined with the effect of hyperthermia and local chemotherapy creates the largest dimensions of treatment.

Vascular targeting agent Oxi4503 inhibits tumor growth in a colorectal liver metastases model

Oxi4503 is a potent vascular targeting agent belonging to the family of combretastatins. These agents produce an acute reduction in tumor blood flow leading to tumor necrosis. Despite evidence of its efficacy in certain malignancies, the effect on colorectal liver metastases remains largely unknown. This study investigates the effect of Oxi4503 on colorectal liver metastases in a murine model. The effect of a single dose of Oxi4503 on established tumors in a murine model of colorectal liver metastases was assessed following administration of 1-50 mg/kg Oxi4503. In addition, the effects of continuous, daily and intermittent dosing (1-5 mg/kg) on tumor necrosis and growth were studied by quantitative histological and stereological analysis. The effect of multiple dosing on long-term survival was also assessed using the Kaplan-Meier analysis. The microvascular effects of therapy were studied by scanning electron microscopy of microvascular resin casts. A single dose of 5 or 50 mg/kg of Oxi4503 produced significant tumor necrosis compared to the controls. Subcutaneous continuous dosing infusion with Oxi4503 at 1 mg/kg/day reduced tumor growth compared to the controls, but was associated with marked systemic toxicity. Daily administration over 21 days was associated with significant mortality. Intermittent dosing of Oxi4503 (two doses, 3 days apart) produced the greatest reduction in tumor growth with minimal toxicity and conferred a significant survival advantage. Microvascular casts demonstrated significant disruption of tumor vessels. A single dose of Oxi4503 produced significant necrosis and microvascular injury in colorectal liver metastases. Intermittent dosing with Oxi4503 produced the maximum reduction in tumor growth, minimal toxicity, and a significant improvement in survival. Oxi4503 is a potential anticancer agent. Further research into its mechanism of action and its synergistic use with other therapies is warranted.

Pharmacodynamic assessment of the anti-angiogenic and anti-vascular properties of bevacizumab by magnetic resonance imaging in metastatic colorectal carcinoma (CRC)

3546 Background: Addition of bevacizumab to FOLFOX-4 prolongs progression free and overall survival in patients with metastatic CRC. Bevacizumab reduces tumor blood flow, so may impair delivery of subsequent cytotoxic chemotherapy. We present the first data that describe in detail the temporal anti-angiogenic and anti-vascular effects of bevacizumab. Methods: DCE-MRI and volumetrics were used to evaluate tumor pharmacodynamics and growth inhibition in ten patients with newly diagnosed CRC liver metastases. Patients were imaged at baseline (twice), 4 hours after single agent 10mg/kg bevacizumab, and at days 3, 8, and 12. An extended Tofts model was applied to allow calculation of plasma volume (vp) and Ktrans. Results: 34 tumors were identified. Significant reductions in Ktrans and vp were detected within 4 hours, were maximal at day 3 and persisted until day 8 (all p<0.001). The proportion of enhancing voxels was also reduced within 4 hrs (p=0.007) and persisted to day 12 (p<0.001). Mean tumor volume exhi...

Hypoxia and Aggressive Tumor Phenotype: Implications for Therapy and Prognosis

Tumor hypoxia, mostly resulting from poor perfusion and anemia, is one of the key factors in inducing the development of cell clones with an aggressive and treatment-resistant phenotype that leads to rapid progression and poor prognosis. Studies in patients with solid tumors suggest that there is a range of hemoglobin (Hb) concentrations that is optimum for tumor oxygenation. When used to achieve an Hb level within this range, erythropoiesis-stimulating agents (ESAs) can be expected to increase tumor oxygenation, and this may favorably influence sensitivity to treatment as well as quality of life. There is no robust evidence that ESAs, when used as indicated, have a negative effect on survival in patients with solid tumors. When used outside the indications recommended, the rise in Hb level that results may reduce tumor blood flow and tissue oxygenation because of a raised viscosity within the abnormal tumor microvasculature. In the current situation, it remains important to use ESAs within the approved indications and according to treatment guidelines such as those developed by the European Organization for Research and Treatment of Cancer.

Targeting Vascular Endothelial Growth Factor in Advanced Carcinoid Tumor: A Random Assignment Phase II Study of Depot Octreotide With Bevacizumab and Pegylated Interferon Alfa-2b

Effective systemic therapy for advanced carcinoid is lacking. The combination of bevacizumab (BEV) and pegylated (PEG) interferon alpha-2b was evaluated among patients with metastatic or unresectable carcinoid tumors. Forty-four patients on stable doses of octreotide were randomly assigned to 18 weeks of treatment with bevacizumab or PEG interferon alpha-2b. At disease progression (PD) or at the end of 18 weeks (whichever occurred earlier), patients received bevacizumab plus PEG interferon until progression. Functional computer tomography (CT) scans were performed to measure effect on tumor blood flow. In the bevacizumab arm, four patients (18%) achieved confirmed partial response (PR), 17 patients (77%) had stable disease (SD), and one patient (5%) had PD. In the PEG interferon arm, 15 patients (68%) had SD and six patients (27%) had PD. Progression-free survival (PFS) rates after 18 weeks of monotherapy were 95% in bevacizumab versus 68% on the PEG interferon arm. The overall median PFS for all 44 patients is 63 weeks. Compared with paired baseline measurements on functional CT scans, we observed a 49% (P < .01) and 28% (P < .01) decrease in tumor blood flow at day 2 and week 18 among patients treated with bevacizumab. No significant changes in tumor blood flow were observed following PEG interferon. PEG interferon alpha-2b treatment was associated with decrease in plasma basic fibroblast growth factor (bFGF; P = .04) and increase in plasma interleukin-18 (IL-18; P < .01). No significant changes in bFGF or IL-18 following treatment with bevacizumab were observed. Bevacizumab therapy resulted in objective responses, reduction of tumor blood flow, and longer PFS in patients with carcinoid than PEG interferon treatment.

Vascular disrupting action of electroporation and electrochemotherapy with bleomycin in murine sarcoma

Electrochemotherapy has a direct cytotoxic effect on tumour cells, and presumably, a vascular disrupting effect. In this study, on the basis of the prediction of the mathematical model, histological evaluation and physiological measurements of the tumours were carried out to confirm that electroporation and electrochemotherapy of tumours have a vascular disrupting action. In the study, SA-1 solid subcutaneous sarcoma tumours in A/J mice were treated by bleomycin (BLM) given intravenously (1 mg kg−1), application of electric pulses (8 pulses, 1040 V, 100 μs, 1 Hz) or a combination of both – electrochemotherapy. The vascular effect was determined by laser Doppler flowmetry, power Doppler ultrasonographic imaging and Patent blue staining. The extent of tumour hypoxia was determined immunohistochemically by hypoxia marker pimonidazole and partial pressure of oxygen (pO2) in tumours by electron paramagnetic resonance oximetry. Electrochemotherapy with BLM induced good antitumour effect with 22 days, tumour growth delay and 38% tumour cures. The application of electric pulses to the tumours induced instant but transient tumour blood flow reduction (for 70%) that was recovered in 24 h. During this tumour blood flow reduction, we determined an increase in hypoxic tumour area for up to 30%, which was also reflected in reduced tumour oxygenation (for 70%). According to the described mathematical model, endothelial cells lining in tumour blood vessels are exposed to a ∼40% higher electric field than the surrounding tumour cells, and therefore easily electroporated, allowing access of high BLM concentration to the cytosol. Consequently, electrochemotherapy has, besides the immediate vascular disrupting action, also a delayed one (after 24 h), as a consequence of endothelial cell swelling and apoptosis demonstrated by extensive tumour necrosis, tumour hypoxia, prolonged reduction of tumour blood flow and significant tumour growth delay, and tumour cures. Our results demonstrate that in addition to the well-established direct cytotoxic effect on tumour cells, electrochemotherapy also has an indirect vascular disrupting action resulting altogether in extensive tumour cell necrosis leading to complete regression of tumours.

Phase I evaluation of OXi4503, a vascular disrupting agent, in patients with advanced solid tumours

14146 Background: OXi4500, the active product of OXi4503, is a vascular disrupting agent acting at the colchicine binding site on the β subunit of tubulin. OXi4503 has greater anti-tumour activity in human cancer cell lines, causes a greater reduction in tumour blood flow than combretastatin A4P and has single agent activity in human tumour xenograft models. A phase I trial has commenced to examine the safety, tolerability and pharmacokinetics of OXi4503, with the primary objective being determination of MTD. FDG-PET scans were performed prior to and 28 days after the first infusion of OXi4503. Several other pharmacodynamic endpoints are also being assessed including DCE &amp; BOLD MRI, circulating endothelial progenitor cells and cytokeratin 18. Methods: OXi4503 is administered by 3 weekly iv infusions to a maximum of 6 cycles. Starting dose was 0.06mg/m2. 100% dose escalation in single patient cohorts proceeded to 3.84mg/m2, when cohorts were expanded to three patients and 30% escalation due to emergence of grade 2 drug-related toxicity (thrombocytopaenia). Results: 11 patients have so far received OXi4503 (5F 6M, median age 54, range 33–68); median cycles received was 2 (range 1–4). Common AE’s include hypertension, pyrexia and anaemia. PK profiles show a dose-dependent linear increase in peak plasma concentrations and AUC of both OXi4503 and OXi4500. OXi4500 concentrations at current dosing (5 mg/m2) are close to that seen at the MTD in rats and dogs. DCE-MRI showed significant reduction in Ktrans in one patient (0.24mg/m2). In the 2 patients studied to date, PET images showed a decrease in the standardised uptake value (SUV) in 3 out of 4 metastases for one subject (1.92mg/m2) and in 5 out of 7 metastases for the other subject (3.84mg/m2) demonstrating a reduction in FDG uptake following drug treatment. Of 10 patients assessed, 2 have stable disease and 8 disease progression. Conclusions: OXi4503 has been tolerated at doses up to 5mg/m2 with no DLT observed, but changes in functional activity have been seen in 3 patients. MTD has not been reached and recruitment is ongoing. [Table: see text]

A randomized phase 2 trial of combretatstatin A4 phosphate (CA4P) in combination with paclitaxel and carboplatin to evaluate safety and efficacy in subjects with advanced imageable malignancies

14060 Background: CA4P is the lead compound in a class of agents termed Vascular Disrupting Agents. Phase I studies of CA4P demonstrated toxicities that do not overlap those of chemotherapy. In vitro studies show synergistic cytotoxicity for CA4P and chemotherapy. This study was designed to assess safety, toxicity and tumor perfusion of CA4P at 2 doses when combined with paclitaxel and carboplatin at fixed doses. Methods: A one stage, randomized trial for subjects with imageable tumors by DCE-MRI for perfusion. Subjects received either 45 or 63 mg/m2 CA4P IV on Days 1, 8, and 15, then 200 mg/m2 paclitaxel and AUC 6 carboplatin on Day 2 of each 21 day cycle. After completion of 6 cycles, subjects could continue with CA4P alone. DCE-MRI was measured prior and 24 hours after the first dose of CA4P. Results: 13 subjects were accrued from 3/05–11/05. 78 cycles were administered and 1 subject continues active therapy on cycle 19. The median number of cycles administered was 6. Both 45 and 63 CA4P with paclitaxel/carboplatin were well tolerated. The most frequent adverse events are listed in Table 1 . Grade 3–4 AEs were similar between the two dose groups. Table 1 : Most Frequent AEs by CA4P Dose DCE-MRI data showed a mean reduction in blood flow for both dose groups (46% vs. 19% respectively) confirming CA4P’s tumor vascular disrupting capabilities. Tumor responses were observed and were similar between both dose groups. Best overall response through cycle 6 was 3 PR, and 6 SD. Two subjects with thyroid cancer were randomized to the low dose group and completed cycle 6. The 1st had SD and progressed after cycle 6. The 2nd achieved PR and progressed after 8 cycles. These subjects also had the greatest reduction in tumor blood flow. Ktrans was reduced by 73 and 79% 24 hours post CA4P. Conclusion: These doses of CA4P in combination with paclitaxel and carboplatin were well tolerated, demonstrated anti-tumor activity and reduction of tumor blood flow. [Table: see text] No significant financial relationships to disclose.

Functional Neoangiogenesis Imaging of Genetically Engineered Mouse Prostate Cancer Using Three-Dimensional Power Doppler Ultrasound

We report the first application of high-frequency three-dimensional power Doppler ultrasound imaging in a genetically engineered mouse (GEM) prostate cancer model. We show that the technology sensitively and specifically depicts functional neoangiogenic blood flow because little or no flow is measurable in normal prostate tissue or tumors smaller than 2-3 mm diameter, the neoangiogenesis "switch-on" size. Vascular structures depicted by power Doppler were verified using Microfil-enhanced micro-computed tomography (micro-CT) and by correlation with microvessel distributions measured by immunohistochemistry and enhanced vascularity visualized by confocal microscopy in two GEM models [transgenic adenocarcinoma of the mouse prostate (TRAMP) and PSP94 gene-directed transgenic mouse adenocarcinoma of the prostate (PSP-TGMAP)]. Four distinct phases of neoangiogenesis in cancer development were observed, specifically, (a) an early latent phase; (b) establishment of a peripheral capsular vascular structure as a neoangiogenesis initiation site; (c) a peak in tumor vascularity that occurs before aggressive tumor growth; and (d) rapid tumor growth accompanied by decreasing vascularity. Microsurgical interventions mimicking local delivery of antiangiogenesis drugs were done by ligating arteries upstream from feeder vessels branching to the prostate. Microsurgery produced an immediate reduction of tumor blood flow, and flow remained low from 1 h to 2 weeks or longer after treatment. Power Doppler, in conjunction with micro-CT, showed that the tumors recruit secondary blood supplies from nearby vessels, which likely accounts for the continued growth of the tumors after surgery. The microsurgical model represents an advanced angiogenic prostate cancer stage in GEM mice corresponding to clinically defined hormone-refractory prostate cancer. Three-dimensional power Doppler imaging is completely noninvasive and will facilitate basic and preclinical research on neoangiogenesis in live animal models.

Combretastatin A-4-phosphate effectively increases tumor retention of the therapeutic antibody, 131I-A5B7, even at doses that are sub-optimal for vascular shut-down.

Radioimmunotherapy using 131I-A5B7, an anti-CEA antibody, in combination with the vascular disrupting agent, combretastatin A4-phosphate (CA-4-P, 200 mg/kg), has produced tumor cures in SW1222 colorectal xenografts. CA-4-P causes acute tumor blood vessel shutdown, which can be monitored in clinical trials using dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). The purpose of this study was to determine the magnitude of the anti-vascular effect of CA-4-P in the SW1222 tumor, at 200 mg/kg and at lower, more clinically relevant doses, using conventional assays; relate effects to changes in DCE-MRI parameters and determine the corresponding effects on tumor retention of 131I-A5B7. The tumor vascular effects of 30, 100 and 200 mg/kg CA-4-P were determined, at 4- and 24-h post-treatment, using DCE-MRI, uptake of Hoechst 33342 for tumor vascular volume and conventional histology for necrosis. The effect of CA-4-P on tumor and normal tissue 131I-A5B7 retention was also determined. A significant reduction in tumor DCE-MRI kinetic parameters, the initial area under the contrast agent concentration time curve (IAUGC) and the transfer constant (Ktrans), was demonstrated at 4 h after CA-4-P, for all dose levels. These effects persisted for at least 24 h for the 200 mg/kg group but not for lower doses. A similar pattern was seen for vascular volume and necrosis. Despite this dose response, all three dose levels increased tumor retention of radio labeled antibody to a similar degree. These results demonstrate that moderate tumor blood flow reduction following antibody administration is sufficient to improve tumor antibody retention. This is encouraging for the combination of CA-4-P and 131I-A5B7 in clinical trials.

Noninvasive Assessment of Tumor Vasculature Response to Radiation-Mediated, Vasculature-Targeted Therapy Using Quantified Power Doppler Sonography

Stereotactic radiotherapy (ablative radiation) is a modality that holds considerable promise for effective treatment of intracranial and extracranial malignancies. Although tumor vasculature is relatively resistant to small fractionated doses of ionizing radiation, large ablative doses of ionizing radiation lead to effective demise of the tumor vasculature. The purpose of this study was (1) to noninvasively monitor and compare tumor physiologic parameters in response to ablative radiation treatments and (2) to use these noninvasive parameters to optimize the schedule of administration of radiation therapy. Lewis lung carcinoma tumors were implanted into C57BL/6 mice and treated with ablative radiation. The kinetics of change in physiologic parameters of a response to single-dose 20-Gy treatments was measured. Parameters studied included tumor blood flow, apoptosis, and proliferation rates. Serial tumor sections were stained to correlate noninvasive Doppler assessment of tumor blood flow with microvasculature histologic findings. A single administration of 20 Gy led to an incomplete tumor vascular response, with subsequent recovery of tumor blood flow within 4 days after treatment. Sustained reduction of tumor blood flow by administering the successive ablative radiation treatment before tumor blood flow recovery led to a 3-fold tumor growth delay. The difference in tumor volumes at each measurement time point (every 2 days) was statistically significant (P=.016). This study suggests a rational design of schedule optimization for radiation-mediated, vasculature-directed treatments guided by noninvasive assessment of tumor blood flow levels to ultimately improve the tumor response.

A phase I pharmacokinetic (PK) and pharmacodynamic (PD) study of MN-029, a novel vascular disrupting agent (VDA), in patients (pts) with advanced solid tumors

3096 Background: MN-029 is a novel VDA that binds reversibly to the colchicine-binding site on tubulin and inhibits microtubule assembly, resulting in disruption of the cytoskeleton of tumor endothelial cells (EC). Disruption of the tumor EC cytoskeleton ultimately leads to a temporary reduction in tumor blood flow. Methods: MN-029 is administered IV as a 10–20 min infusion, at 3-wk intervals in pts with advanced cancer. The study has followed an accelerated titration design, with intrapatient dose escalation. PD effects on tumor blood flow are evaluated using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Results: 28 pts were enrolled (13M/15F), median age 56 (range 35 - 76) and tumor types: colorectal (5), renal (5), hepatocellular (3), ovarian (2), melanoma (2), soft tissue sarcoma (2), carcinoid (2) and others (7). A total of 110 cycles of MN-029 were given, median 3/pt (range 1–20), over 9 dose levels (4, 8, 16, 24, 36, 54, 80, 120 and 180 mg/m2). Escalation proceeded until an initial dose-limiting toxicity (DLT) was observed in 1 pt in the 180 mg/m2 cohort, consisting of a reversible episode (3 hours post dose) of acute coronary ischemia (without sequelae and with preservation of myocardial function) probably due to coronary vasospasm. Therefore, this cohort was expanded to 6 pts, with no further DLTs observed. Common mild to moderate toxicities included nausea, vomiting (which appears dose-related), hypotension, fatigue and diarrhea. There was no significant myelotoxicity, stomatitis or alopecia. Seven pts had stable disease after 3 cycles, including 2 pts with carcinoid tumor (+21 cycles and +17 cycles). PK data generally indicated dose-related increases in Cmax and AUC values, although substantial inter-patient variability was observed. Tumor blood flow reduction assessed by DCE-MRI was recorded at 120 and 180 mg/m2, but not at 80 mg/m2. Conclusions: MN-029 produced reductions in tumor blood flow at doses that were well tolerated. Accrual continues at 225 mg/m2. [Supported in part by grants from MediciNova, Inc. and M01 RR-000080] [Table: see text]

An enriched phase I, pharmacokinetic and pharmacodynamic study of the N-cadherin (NCAD) cyclic competitive binder exherin (ADH-1) in patients with solid tumors

3042 Background: N-cad is a cell adhesion molecule expressed by vascular endothelium and tumor cells of invasive tumors. ADH-1, a cyclic pentapeptide, antagonizes N-cad, causing rapid tumor vascular disruption and apoptosis in preclinical models. We report results from a Phase I study of weekly doses of intravenous ADH-1 given to patients with N-cad+ solid tumors, to evaluate safety, PK, antitumor activity, and effect of ADH-1 on tumor vasculature assessed by DCE-MRI. Methods: ADH-1 starting dose was 150 mg/m2 administered weekly for 3 W in 28 D cycles. DCE-MRI was performed to assess changes in tumor perfusion 90 mins after the first dose of ADH-1, and repeated on D 15 if no changes were noted. Following the 3rd dose level (DL 3, 600 mg/m2 ), the schedule was amended to weekly ADH-1 without interruption, in 21 D cycles. Results: 55 pts with refractory solid tumors were screened, 56% were N-cad+ [screened/N-cad+: GYN 16/21 (Ovarian 13/17), GI 5/14, breast 2/6, renal 5/5, head &amp; neck 2/3, others 2/6]. 13 pts (5 males, median age 53 yrs.) received 20 cycles of ADH-1 by bolus injection at 150, 300 and 600 mg/m2/weekly ×3 W Q21–28 D. No DLTs have occurred to date. No pts have experienced &gt; grade 2 study drug related AEs. One pt, with fallopian tube ca. had a mixed response. There was a 30% reduction in retroperitoneal nodal disease at the end of cycle 3, and a 37% reduction at the end of Cy 4. However, new bone lesions were also noted at the end of cycle 4 assessment. Tumor blood flow reduction of ≥40% was noted in this patient, and she also reported pain in the region of the tumor following multiple doses of ADH-1. PK parameters are available for the first 3 DLs (150, 300, and 600 mg/m2): mean Cmax 22.1, 37.0, and 50.8μg/mL, respectively; AUCinf 24.3, 60.6, and 110.3 h·μg/mL; Vss 12.6, 15.1, and 16.3 L/m2; and T1/2 1.8, 2.7, and 2.4hr. Conclusions: ADH-1 has been well tolerated in 4 dose levels tested to date, dose escalation is proceeding. No DLTs have occurred and the MTD has not been reached. Anti-tumor activity has been noted. Updated clinical, PK and PD results will be presented. [Table: see text]

Improved Tumor Destruction with Arsenic Trioxide and Radiofrequency Ablation in Three Animal Models

To assess the extent of tumor blood flow reduction that is achievable with arsenic trioxide (As2O3) and the effect of As2O3 on radiofrequency (RF)-induced coagulation. All animal protocols and experiments were approved by an institutional animal care and use committee before the start of the study. Experiments were conducted in three tumor models: intrarenal VX2 sarcoma in 27 rabbits, RCC 786-0 human renal cell carcinoma in 24 nude mice, and R3230 mammary adenocarcinoma in 40 rats. One dose (0-7.5 mg per kilogram of body weight) of As2O3 was administered (intraperitoneally in rodents, intravenously in rabbits) 1, 6, or 24 hours before standardized RF ablation, which was performed by using a 1-cm active tip, with mean temperatures of 70 degrees C +/- 2 (standard deviation) for 5 minutes in rodents and 90 degrees C +/- 2 for 6 minutes in rabbits. Laser Doppler flowmetry was used to quantify changes in blood flow, which were compared with diameters of induced tumor coagulation. Comparisons between groups were performed by using Student t tests or analysis of variance. The strengths of correlations between As2O3, tumor blood flow, and RF-induced coagulation were assessed by using linear and higher-order regression models and reported as R2 computations. Administration of As2O3 significantly (P < .05) reduced blood flow and increased tumor destruction in all tumor models. In VX2 sarcoma tumors, 1 mg/kg As2O3 reduced mean tumor blood flow to 46% +/- 13 of the normal value. The mean resultant coagulation (1.1 cm +/- 0.1) was significantly greater than that achieved with RF ablation alone (0.6 cm +/- 0.1, P < .01). In RCC 786-0 and R3230 tumors, 5 mg/kg As2O3 reduced mean tumor blood flow to 57% +/- 6 and 46% +/- 6 of normal, respectively, increasing mean ablation extent to 0.8 cm +/- 0.1 for both models, compared with those achieved with the control treatment (0.6 cm +/- 0.1 and 0.5 cm +/- 0.1, respectively; P < .05 for both comparisons). Dose studies revealed correlations between drug dose, tumor blood flow, and RF-induced coagulation in all three tumor models (R2 = 0.60-0.79). Maximal RF synergy was observed 1 hour after As2O3 administration. As2O3 administration represents a transient noninvasive method of reducing tumor blood flow during RF ablation, enabling larger zones of tumor destruction in multiple tumor models.

Effects of the tumor vasculature targeting agent NGR-TNF on the tumor microenvironment in murine lymphomas

TNF-alpha may improve drug delivery to tumors by alteration of vascular permeability. However, toxicity precludes its systemic administration in patients. NGR-TNF comprises TNF coupled to the peptide CNGRC, which is a ligand for CD13. CD13 is expressed on tumor vasculature. Therefore, to assess the efficacy of NGR-TNF its biological effect on tumor vasculature should be measured rather than its effect on tumor growth. The aim of this study was to assess the effects of a low dose of NGR-TNF (5 ng/kg) on vascular permeability, tumor hypoxia, perfusion and proliferation in lymphoma bearing mice. MRI measurements with blood pool contrast agent showed an increased leakage of the contrast agent from the vasculature in NGR-TNF treated tumors compared with controls (p < 0.05), suggesting NGR-TNF-induced vascular permeability. Immunohistochemical analysis two hours after NGR-TNF treatment showed a decrease in tumor hypoxia (p < 0.1) and an increase in labeling index of the S-phase marker bromodeoxyuridine (p < 0.1), possibly due to an increase in tumor blood flow after NGR-TNF treatment. Although a decrease in tumor hypoxia and an increase in labeling index could have lead to increased tumor growth, in this experiment after one day a decrease in tumor volume was measured. Possibly, the effects on tumor hypoxia and proliferation two hours after treatment are transient and overruled by other, more longlasting effects. For example, the observed increase in vascular permeability may lead to haemoconcentration and increased interstitial pressure, ultimately resulting in an reduction of tumor blood flow and thus a decrease in tumor growth. A beneficial effect of NGR-TNF in combination with other therapeutical agents may therefore critically depend on the sequence and timing of the regimens. Currently, NGR-TNF is being tested in clinical studies.

Inhibition of Tumor Growth by RGD Peptide–Directed Delivery of Truncated Tissue Factor to the Tumor Vasculature

Selective activation of blood coagulation in tumor vessels with subsequent tumor infarction is a promising anticancer strategy. To this end, a fusion protein consisting of the extracellular domain of tissue factor [truncated tissue factor (tTF)] was fused to the peptide GRGDSP selectively targeting alpha(v)-integrins on tumor endothelial cells. tTF-RGD retained its thrombogenic and integrin-binding activity in vitro. In vivo studies in mice bearing human adenocarcinomas (CCL185), melanoma (M21), and fibrosarcoma (HT1080) revealed that i.v. administration of tTF-RGD induced thrombotic occlusion of tumor vessels resulting in tumor growth retardation or regression in all three types of solid tumors. No apparent side effects, such as thrombosis, in other organs or other treatment-related toxicities were observed. Reduced tumor blood flow in tTF-RGD-treated animals as determined by contrast-enhanced magnetic resonance imaging underlines the proposed mechanism. In conclusion, we consider RGD peptide-directed delivery of tTF as alternative to previously used antibody fusion proteins. Small peptide-directed delivery of coaguligands does not cause immunologic side effects and those caused by accumulation in the reticuloendothelial system. This is the first report to describe the induction of selective thrombosis in tumor vessels by RGD peptide-directed delivery of tTF, which may be a promising strategy for the treatment of cancer.

Author reply

In their letter to the editor regarding our review1 of vascular targeting therapies, Brown et al.2 indicate that there exist alternatives to the agents we described, especially arsenic trioxide. The exclusion of compounds such as arsenic trioxide from the review was not an oversight. Our aim in the review article on vascular targeting therapies was to discuss agents developed specifically as small-molecule vascular disrupting drugs. In that context, we focused on agents that have made the greatest advances in the clinic. Lead agents in this category (CA4P, ZD6126, DMXAA) have demonstrated clear evidence of selective reductions in tumor blood flow, not only in a wide variety of preclinical tumor models but also in solid tumors in patients with cancer. Clearly, other agents, some of which have entered clinical trials, although not specifically designed for this purpose, also may induce vascular damage. Such agents include the colchicines, vinca alkaloids, the cytokines tumor necrosis factor-alpha and interleukin-1, as well as arsenic trioxide. Generally, these agents only induce vascular damage at doses close to their maximum tolerated doses, thus raising concerns about their potential future as vascular targeting agents. Whether this applies to arsenic trioxide remains to be seen. Certainly, the preclinical data obtained with this agent suggest that it has vasculardisrupting properties. It is unknown, however, whether its administration will lead to antivascular effects in solid tumors in patients. Given the significant potential of vascular disrupting therapies, we certainly encourage the investigation of all agents and therapies for their potential to target tumor blood vessels. It should be recognized, however, that in our review of vascular targeting therapies, we purposely concentrated on small molecules that were under development specifically as vascular disrupting agents with a focus on those that had entered patient trials. Dietmar W. Siemann Ph.D.*, David J. Chaplin Ph.D. , Michael R. Horsman PhD, DMSc , * Department of Radiation Oncology, University of Florida, Gainesville, FL, Oxigene, Inc., Boston, MA, Department of Experimental Oncology, Aarhus University, Aarhus, Denmark.