PRT treatment had an effect on the development of the normal platelet storage lesion at a level which seems tolerable for clinical usage.
There is no evidence from these studies that Mirasol PRT treatment alters PLT mitochondrial structural and functional integrity immediately after treatment and during PLT storage. An increased demand for ATP may be the driving force for observed increases in both the glycolytic flux and the oxidative metabolism observed in treated PLTs.
We are developing a technology based on the combined application of riboflavin (RB) and light for inactivating pathogens in blood products while retaining the biological functions of the treated cells and proteins. Virus and bacteria reduction measured by tissue culture infectivity or colony formation with UV light alone and in combination with RB yield equivalent results. The effects of RB as a sensitizing agent on DNA in white cells, bacteria and viruses in combination with UV light exposure have been evaluated. UV-mediated DNA degradation in Jurkat T cells and leukocytes in plasma as measured by the FlowTACS assay was significantly increased in the presence of RB. Agarose gel electrophoretic analysis of DNA in Escherichia coli and leukocytes in plasma demonstrated enhanced DNA degradation in the presence of RB. UV light in combination with RB prevented the reactivation of lambda phage compared with samples irradiated in the absence of RB. UV-mediated oxidative damage in calf thymus DNA was also enhanced in the presence of RB. These observations clearly demonstrate that the presence of RB and UV light selectively enhances damage to the guanine bases in DNA. These data also suggest that the type and extent of damage to DNA for virus in the presence of RB and light make it less likely to be repaired by normal repair pathways available in host cells.
Purpose: This in vivo study was designed to determine the optimal doses and schedules of vandetanib, a dual epidermal growth factor receptor (EGFR)-vascular endothelial growth factor receptor tyrosine kinase inhibitor, in combination with irinotecan in a murine xenograft model of human colon cancer. Experimental Design: HT-29 tumor-bearing nude mice were treated with two doses of vandetanib (12.5 and 25 mg/kg/d) with or without irinotecan (100 mg/kg) using either sequential or concurrent schedules for 30 days. Tumor size was measured using standard variables, whereas the antiangiogenic response was evaluated using dynamic contrast-enhanced magnetic resonance imaging. Additionally, effects on EGFR-dependent signal transduction pathways and proliferation were assessed using immunohistochemistry. These pharmacodynamic end points were then evaluated for associations with antitumor efficacy and/or to plasma/tumor concentrations of vandetanib. Results: The greatest antitumor efficacy was observed in the groups receiving the highest dose of vandetanib given continuously (concurrent schedule), alone or in combination with irinotecan. These dosing schedules resulted in significant effects on tumor vasculature, with decreased volume transfer constants, area under the curve, and permeability surface factor as well as increased gadolinium clearance after 30 days of treatment. In addition, these groups showed the greatest inhibition of EGFR signaling. Interestingly, tumor concentrations of vandetanib were increased by irinotecan in the concurrent schedule, possibly due to decreased tumor perfusion in this group. Conclusions: These data suggest that higher, sustained concentrations of vandetanib (versus intermittent), alone and in combination with irinotecan, result in optimal antitumor efficacy in this model and may have implications for the design of future clinical studies with this drug.
To date, clinical studies combining the new generation of targeted therapies and chemotherapy have had mixed results. Preclinical studies can be used to identify potential antagonism/synergy between certain agents, with the potential to predict the most efficacious combinations for further investigation in the clinical setting. In this study, we investigated the sequence-dependent interactions of ZD6474 with oxaliplatin in two human colon cell lines in vitro. We evaluated the in vitro antitumor activity of ZD6474, an inhibitor of vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR) and RET tyrosine kinase activity, and oxaliplatin using three combination schedules: ZD6474 before oxaliplatin, oxaliplatin before ZD6474, and concurrent exposure. Cell proliferation studies showed that treatment with oxaliplatin followed by ZD6474 was highly synergistic, whereas the reverse sequence was clearly antagonistic as was concurrent exposure. Oxaliplatin induced a G 2 -M arrest, which was antagonized if the cells were previously or concurrently treated with ZD6474. ZD6474 enhanced oxaliplatin-induced apoptosis but only when added after oxaliplatin. The sequence-dependent antitumor effects appeared, in part, to be based on modulation of compensatory prosurvival pathways. Thus, expression of total and active phosphorylated EGFR, as well as AKT and extracellular signal-regulated kinase, was markedly increased by oxaliplatin. This increase was blocked by subsequent treatment with ZD6474. Furthermore, the synergistic sequence resulted in reduced expression of insulin-like growth factor-I receptor and a marked reduction in secretion of vascular endothelial growth factor protein. ZD6474 in combination with oxaliplatin has synergistic antiproliferative properties in human colorectal cancer cell lines in vitro when oxaliplatin is administered before ZD6474.
Introduction: Despite the progress that has been made for standard risk multiple myeloma (MM), subsets of patients with the most advanced and aggressive plasma cell dyscrasias still suffer comparatively poor outcomes. One example is plasma cell leukemia (PCL), which carries a median overall survival of under two years. For patients with PCL, response to front line therapy occurs but is often short-lived, ultimately giving way to aggressive multi-drug resistant disease and patient mortality. Thus, there is a need for the development of new strategies that improve the prognoses for these patients. Melflufen (melphalan flufenamide) is a first-in-class peptide-drug conjugate that is currently in late-phase clinical trials for multiple myeloma. This highly lipophilic agent is preferentially retained in malignant plasma cells (MPCs), where overexpressed aminopeptidases lead to trapping of the alkylator melphalan. We evaluated the anti-myeloma effects of melflufen on patient samples treated ex vivo, and found pronounced sensitivity to melflufen in most samples, with particularly potent efficacy in PCL samples. Methods: Bone marrow aspirate or peripheral blood samples were obtained from patients with plasma cell disorders after IRB approval and informed consent. Ex vivo efficacy of melflufen and melphalan were compared using our Myeloma Drug Sensitivity Testing (My-DST) platform that optimizes viability and tests the malignant cells in the context of the normal cells from their microenvironment (Walker et al, Blood Advances, 2020). In brief, mononuclear cells from patients with plasma cell dyscrasia, including MM and PCL, were isolated and cultured in triplicate wells with titrations of melphalan, melflufen or untreated controls for 48 hours. Post-treatment survival was measured by high-throughput flow cytometry with antibodies for CD138, CD38, CD45 and CD19, and a live/dead dye to discriminate viable MPCs from normal bone marrow cells. EC50 values were determined from these titrations using nonlinear regression curve fits. When the EC50 for melflufen was established in My-DST, a single dose concentration of 10 nM was used to screen patient samples and distinguish relative sensitivity or resistance. Results: Using the My-DST approach with 48 hour drug treatments, melflufen significantly decreased the viable MPC populations, whereas melphalan had little effect (Fig 1A). Concurrent titrations revealed significantly higher MPC sensitivity to melfufen (mean melphalan EC50 = not reached, mean melflufen EC50 = 22.9 nM) (Fig 1B). By comparison to another alkylator, cyclophosphamide's active metabolite has an EC50 of 3.75 µM in this assay. Response to melflufen was accentuated in 2/3 PCL samples tested (HTB-1802.1, HTB-1389.1), with the EC50 < 1nM (Fig 1B). Melflufen demonstrated toxicity in CD45 positive white blood cells, which is consistent with neutropenia observed in clinical trials (data not shown). In single dose screening studies in additional MM patient samples, 4/8 (50%) showed >20% decrease in viable MPCs after incubation with melflufen at 10 nM (Fig 1C). Overall, using those parameters for ex vivo "response" to meflufen, 3/3 patients with PCL responded, 5/6 patients with del(17p) responded, and 3/3 patients with c-MYC translocations responded (Fig 1C, italics). In addition, 3/5 samples from patients that were clinically daratumumab-refractory displayed sensitivity to melflufen. Of five samples from patients with prior exposure to alkylators, four were sensitive to melflufen. Conclusion: Overall, these data support that the peptide-drug-conjugate melflufen shows a broad efficacy across samples from patients with plasma cell disorders. Patients facing poor prognoses, including those with PCL, high-risk cytogenetics and daratumumab-refractory disease, have a great need for new treatments. Thus, the encouraging ex vivo results with melflufen in samples from these aggressive subsets support further clinical exploration. In particular, our preliminary data suggest that plasma cell leukemia patients may be exquisitely sensitive to melflufen. To follow-up these findings, we will expand the number of samples tested from PCL and other forms of high-risk MM samples. Ultimately, if the trend for accentuated sensitivity in plasma cell leukemia holds, a clinical approach for melflufen in these patients may improve outcomes for this group. Figure 1 Disclosures Lockerbie: Oncopeptides AB: Current Employment. Flanagan:Oncopeptides AB: Current Employment. Lehmann:Oncopeptides AB: Current Employment. Forsberg:Celgene: Speakers Bureau; Genentech, Inc., Sanofi, Karyopharm, Abbvie: Research Funding. Mark:Takeda: Consultancy; Kayopharm: Consultancy; Bristol-Myers Squibb: Research Funding; Janssen: Research Funding; Celgene: Consultancy; Amgen: Consultancy; Sanofi: Consultancy; Janssen: Consultancy. Sherbenou:Oncopeptides Inc.: Research Funding.
13171 Background: Vascular endothelial growth factor receptors 1, 2 and 3 (VEGFR-1, -2 and -3) have a key role in activation and proliferation of endothelial cells, with expression of VEGFR-3 largely restricted to lymphatic endothelial cells. Although high expression of VEGFR-3 and its specific ligands, VEGF-C and VEGF-D, has been associated with an increased incidence of lymph node metastasis and a poor prognosis in different human malignancies, little is known about the role of this signaling pathway in tumor cells. This study investigated VEGFR-3 and its specific ligands in human colon cancer cells, and the antiproliferative activity of ZD6474, an inhibitor of VEGFR, epidermal growth factor receptor (EGFR) and RET tyrosine kinases, and of the EGFR inhibitors gefitinib and cetuximab. Methods: The expression of VEGFRs and EGFR was determined by RT-PCR, immunoblotting, flow cytometry and immunohistochemistry in four human colon cancer cell lines (HCT-116, HT-29, HCT-15 and SW480). Secretion of transforming growth factor-α (TGF-α), VEGF-A and VEGF-C by cancer cells was determined by ELISA. The in vitro antiproliferative effects of ZD6474, gefitinib and cetuximab were determined using an MTT assay. Results: All four human colon cancer cell lines expressed functional EGFR and secreted high levels of TGF-α. All four cell lines expressed VEGFR-1 and VEGFR-3, but not VEGFR-2, and secreted both VEGF-A and VEGF-C. Treatment with ZD6474 resulted in a dose-dependent cell growth inhibition (IC50 3–5 μM), whereas treatment with gefitinib or with cetuximab produced little growth inhibition under the same culture conditions. Addition of VEGF-C induced a 2-fold increase in cell growth in vitro in all four colon cancer cell lines. Treatment with ZD6474 blocked both basal and VEGF-C-induced phosphorylation of VEGFR-3, as well as VEGF-C-induced cell proliferation. Conclusions: Human colon cancer cell lines express VEGFR-1 and VEGFR-3, and secrete VEGF-A and VEGF-C. A potential VEGF-C/VEGFR-3 autocrine loop has been identified in human colon cancer cells, which can be inhibited by ZD6474, suggesting that ZD6474 may have direct antitumor activity through inhibition of VEGFR signaling. [Table: see text]
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