Evaluation of the drug-drug interaction potential of treosulfan using a physiologically-based pharmacokinetic modelling approach.

AIMS: The aim of this work is the development of a mechanistic physiologically-based pharmacokinetic (PBPK) model using in vitro to in vivo extrapolation to conduct a drug-drug interaction (DDI) assessment of treosulfan against two cytochrome p450 (CYP) isoenzymes and P-glycoprotein (P-gp) substrates. METHODS: A PBPK model for treosulfan was developed de novo based on literature and unpublished clinical data. The PBPK DDI analysis was conducted using the U.S. Food and Drug Administration (FDA) DDI index drugs (probe substrates) midazolam, omeprazole and digoxin for CYP3A4, CYP2C19 and P-gp, respectively. Qualified and documented PBPK models of the probe substrates have been adopted from an open-source online model database. RESULTS: The PBPK model for treosulfan, based on both in vitro and in vivo data, was able to predict the plasma concentration-time profiles and exposure levels of treosulfan applied for a standard conditioning treatment. Medium and low potentials for DDI on CYP3A4 (maximum area under the concentration-time curve ratio (AUCRmax = 2.23) and CYP2C19 (AUCRmax = 1.6) were predicted, respectively, using probe substrates midazolam and omeprazole. Treosulfan was not predicted to cause a DDI on P-gp. CONCLUSION: Medicinal products with a narrow therapeutic index (eg, digoxin) that are substrates for CYP3A4, CYP2C19 or P-gp should not be given during treatment with treosulfan. However, considering the comprehensive treosulfan-based conditioning treatment schedule and the respective pharmacokinetic properties of the concomitantly used drugs (eg, half-life), the potential for interaction on all evaluated mechanisms would be low (AUCR < 1.25), if concomitantly administered drugs are dosed either 2 hours before or 8 hours after the 2-hour intravenous infusion of treosulfan.

The effect of the triazene compound CT913 on ovarian cancer cells in vitro and its synergistic interaction with the PARP-inhibitor olaparib.

OBJECTIVES: Extending the therapeutic spectrum of PARP-inhibitors (PARPi) beyond BRCA1-deficiency and/or overcoming PARPi-resistance is of high clinical interest. This is particularly true for the identification of innovative therapeutic strategies for ovarian cancer, given the recent advances in the use of PARPi in clinical practice. In this regard, the combination of PARPi with chemotherapy is a possible strategy for defining new therapeutic standards. In this study, we analyzed the therapeutic effect of novel triazene derivatives, including the drug CT913 and its metabolite CT913-M1 on ovarian cancer cells and describe their interaction with the PARPi olaparib. METHODS: In vitro assays for drug characterization including RNA-Seq were applied in a selected panel of ovarian cancer cell lines. RESULTS: CT913 treatment conferred a dose-dependent reduction of cell viability in a set of platinum-sensitive and platinum-resistant ovarian cancer cell lines with an IC50 in the higher micromolar range (553-1083 µM), whereas its metabolite CT913-M1 was up to 69-fold more potent, especially among long-term treatment (IC50 range: 8-138 µM). Neither of the drugs sensitized for cisplatin. CT913 conferred synthetic lethality in BRCA1-deficient ovarian cancer cells, indicating that its effect is augmented by a deficiency in homologous recombination repair (HR). Furthermore, CT913 showed a synergistic interaction with olaparib, independently of BRCA1 mutational status. CT913 strongly induced CDKN1A transcription, suggesting cell cycle arrest as an early response to this drug. It moreover downregulated a variety of transcripts involved in DNA-repair pathways. CONCLUSIONS: This is the first study, suggesting the novel triazene drug CT913 as enhancer drug for extending the therapeutic spectrum of PARPi.

Treosulfan, Fludarabine, and Low-Dose Total Body Irradiation for Children and Young Adults with Acute Myeloid Leukemia or Myelodysplastic Syndrome Undergoing Allogeneic Hematopoietic Cell Transplantation: Prospective Phase II Trial of the Pediatric Blood and Marrow Transplant Consortium.

This multicenter study evaluated a treosulfan-based regimen in children and young adults with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) undergoing allogeneic hematopoietic cell transplant (HCT). Forty patients with median age 11 years (range, 1 to 19) underwent allogeneic HCT for AML in first (n = 18), second (n = 11), and third or greater remission (n = 3) or MDS (n = 8) using bone marrow (n = 25), peripheral blood stem cells (n = 5), or cord blood (n = 9). The regimen consisted of body surface area (BSA)-based treosulfan 10 g/m2/day (BSA ≤ .5 m2), 12 g/m2/day (BSA > .5 to 1.0 m2), or 14 g/m2/day (BSA > 1.0 m2) on days -6 to -4; fludarabine 30 mg/m2/day on days -6 to -2; and a single fraction of 200 cGy total body irradiation on day -1. Graft-versus-host disease (GVHD) prophylaxis included tacrolimus and methotrexate for marrow and peripheral blood stem cell and cyclosporine/mycophenolate mofetil for cord blood. One-year overall survival, disease-free survival, and nonrelapse mortality were 80%, 73%, and 3%, respectively. One-year relapse was 38% for AML and 13% for MDS. No serious organ toxicities were observed. All 37 assessable patients engrafted. Cumulative incidences of grades II to IV acute GVHD and chronic GVHD were 22% and 40%, respectively. BSA-based treosulfan dosing resulted in predictable area under the curve and maximum concentration, which is required for dosing without measuring individual pharmacokinetic parameters. Observed differences in pharmacokinetics did not impact disease control or regimen toxicity. This BSA-based treosulfan regimen resulted in excellent engraftment and disease-free survival and minimal toxicity and transplant-related mortality (3%) in children and young adults with AML and MDS.

Validation of a Commercial Assay and Decision Support Tool for Routine Paclitaxel Therapeutic Drug Monitoring (TDM).

BACKGROUND: The value of therapeutic drug monitoring (TDM) for paclitaxel (PTX) was recently demonstrated in the largest TDM trial ever conducted in oncology. The trial demonstrated significant reduction in neuropathy when using TDM. Dose adjustment for PTX was based on time above a threshold concentration (Tc>0.05). Tc>0.05 must be calculated with a pharmacokinetic model and complex nonlinear mixed-effects software. The use of the software and chromatographic methods to measure PTX requires specialized expertise. User-friendly methods to quantitate PTX and calculate Tc>0.05 could simplify the introduction of TDM into routine clinical practice. METHODS: The immunoassay (MyPaclitaxel) was used to quantitate PTX in samples from the clinical trial; the results were used to calculate Tc>0.05 using a stand-alone computer program with a simple, friendly graphical user interface for nonlinear mixed-effects pharmacokinetic calculations (MyCare Drug Exposure Calculator). The resulting dose recommendations from the calculated Tc>0.05 were compared with those using liquid chromatography-ultraviolet detection and NONMEM to examine the efficacy of the simpler tools for TDM. RESULTS: There was a good agreement between the immunoassay and liquid chromatography-ultraviolet detection: Passing-Bablok regression slope was 1.045 and intercept was -6.00, R was 0.9757, and mean bias was -1.77 ng/mL (-2.07 nmol/L). Dosing recommendations were identical for 70% of the cycles and within 10% for 89% of the samples. All Tc>0.05 values were at the same or adjacent medical decision points. CONCLUSIONS: MyPaclitaxel assay and MyCare Drug Exposure Calculator are convenient, user-friendly tools that may be suitable for routine TDM of PTX in clinical care.

Chemosensitivity of conjunctival melanoma cell lines to target-specific chemotherapeutic agents.

OBJECTIVE: In conjunctival melanoma, local chemotherapy has been based so far on clinical evidence and limited to the therapy of melanoma in situ. Our aim was to define substances that may have the potential to add to therapeutic options in extended local growth and metastatic disease. Two conjunctival cell lines (CRMM-1 and CRMM-2) have been established from recurrent conjunctival melanoma. In this study, we examined the chemosensitivity of these cell lines to different cytotoxic substances. MATERIALS AND METHODS: The cell lines CRMM-1 and CRMM-2 were exposed to chemotherapeutics for 24 h and the IC50 was generated. Sulforhodamin-B assays were used for quantification of in vitro efficacy. Time of exposure and escalating concentrations of the substances were adapted to the experimental setting. RESULTS: Bortezomib, clusianone 502 (nemorosone), ranpirnase, and sorafenib were efficient in inhibiting the growth of conjunctival melanoma cell lines. The IC50 achieved concentrations below or around 10 µM for these substances. CONCLUSIONS: Bortezomib, clusianone 502, ranpirnase, and sorafenib inhibited growth in conjunctival melanoma cell lines efficiently. The new substances may be a suitable alternative for local therapy. New therapeutic options with highly specific targeted agents for metastatic disease have to be evaluated in further experiments.

Population pharmacokinetic modeling of treosulfan and rationale for dose recommendation in children treated for conditioning prior to allogeneic hematopoietic stem cell transplantation.

Intravenously infused treosulfan was evaluated in adult and pediatric patients for conditioning regimen prior to allogeneic hematopoietic stem cell transplantation. A population pharmacokinetic (PK) model was initially developed on 116 adult and pediatric PK profiles from historical trials, to support treosulfan dose recommendations for children in 2 prospective trials. The aim was to assess and update the initial population PK model by inclusion of additional 83 pediatric PK profiles from these 2 trials. The final population PK model was 2-compartmental with dosing in the central compartment, linear elimination, and inter-compartmental clearance. Inter-individual variability was included on clearance (CL), central volume (V1), peripheral volume (V2), and inter-compartmental clearance (Q). The final model described an effect of the body surface area (BSA) on CL, V1, V2, and Q. The final model resulted in a modified dose recommendation for children and advises treosulfan doses of 10 g/m2, 12 g/m2, and 14 g/m2 for BSAs of <0.4 m2, ≥0.4 to <0.9 m2, and ≥0.9 m2, respectively. This simplified BSA-dependent dose recommendation was developed for children, ensuring a well comparable treosulfan exposure as a dose of 14 g/m2 in adults - irrespective of their age and without applying individual therapeutic drug monitoring.

SAM-Competitive EZH2-Inhibitors Induce Platinum Resistance by EZH2-Independent Induction of ABC-Transporters.

T-cell lymphomas are heterogeneous and rare lymphatic malignancies with unfavorable prognosis. Consequently, new therapeutic strategies are needed. The enhancer of zeste homologue 2 (EZH2) is the catalytic subunit of the polycomb repressive complex 2 and responsible for lysine 27 trimethylation of histone 3. EZH2 is overexpressed in several tumor entities including T-cell neoplasms leading to epigenetic and consecutive oncogenic dysregulation. Thus, pharmacological EZH2 inhibition is a promising target and its clinical evaluation in T-cell lymphomas shows favorable results. We have investigated EZH2 expression in two cohorts of T-cell lymphomas by mRNA-profiling and immunohistochemistry, both revealing overexpression to have a negative impact on patients' prognosis. Furthermore, we have evaluated EZH2 inhibition in a panel of leukemia and lymphoma cell lines with a focus on T-cell lymphomas characterized for canonical EZH2 signaling components. The cell lines were treated with the inhibitors GSK126 or EPZ6438 that inhibit EZH2 specifically by competitive binding at the S-adenosylmethionine (SAM) binding site in combination with the common second-line chemotherapeutic oxaliplatin. The change in cytotoxic effects under pharmacological EZH2 inhibition was evaluated revealing a drastic increase in oxaliplatin resistance after 72 h and longer periods of combinational incubation. This outcome was independent of cell type but associated to reduced intracellular platinum. Pharmacological EZH2 inhibition revealed increased expression in SRE binding proteins, SREBP1/2 and ATP binding cassette subfamily G transporters ABCG1/2. The latter are associated with chemotherapy resistance due to increased platinum efflux. Knockdown experiments revealed that this was independent of the EZH2 functional state. The EZH2 inhibition effect on oxaliplatin resistance and efflux was reduced by additional inhibition of the regulated target proteins. In conclusion, pharmacological EZH2 inhibition is not suitable in combination with the common chemotherapeutic oxaliplatin in T-cell lymphomas revealing an EZH2-independent off-target effect.

Conditioning with treosulfan and fludarabine followed by allogeneic hematopoietic cell transplantation for high-risk hematologic malignancies.

In this prospective study 60 patients of median age 46 (range: 5-60 years), with acute myelogenous leukemia (AML; n = 44), acute lymphoblastic leukemia (ALL; n = 3), or myelodysplastic syndrome (MDS; n = 13) were conditioned for allogeneic hematopoietic cell transplantation with a treosulfan/fludarabine (Flu) combination. Most patients were considered at high risk for relapse or nonrelapse mortality (NRM). Patients received intravenous treosulfan, 12 g/m(2)/day (n = 5) or 14 g/m(2)/day (n = 55) on days -6 to -4, and Flu (30 mg/m(2)/day) on days -6 to -2, followed by infusion of marrow (n = 7) or peripheral blood stem cells (n = 53) from HLA-identical siblings (n = 30) or unrelated donors (n = 30). All patients engrafted. NRM was 5% at day 100, and 8% at 2 years. With a median follow-up of 22 months, the 2-year relapse-free survival (RFS) for all patients was 58% and 88% for patients without high-risk cytogenetics. The 2-year cumulative incidence of relapse was 33% (15% for patients with MDS, 34% for AML in first remission, 50% for AML or ALL beyond first remission and 63% for AML in refractory relapse). Thus, a treosulfan/Flu regimen was well tolerated and yielded encouraging survival and disease control with minimal NRM. Further trials are warranted to compare treosulfan/Flu to other widely used regimens, and to study the impact of using this regimen in more narrowly defined groups of patients.

Diphenhydramine increases the therapeutic window for platinum drugs by simultaneously sensitizing tumor cells and protecting normal cells.

Platinum-based compounds remain a well-established chemotherapy for cancer treatment despite their adverse effects which substantially restrict the therapeutic windows of the drugs. Both the cell type-specific toxicity and the clinical responsiveness of tumors have been associated with mechanisms that alter drug entry and export. We sought to identify pharmacological agents that promote cisplatin (CP) efficacy by augmenting the levels of drug-induced DNA lesions in malignant cells and simultaneously protecting normal tissues from accumulating such damage and from functional loss. Formation and persistence of platination products in the DNA of individual nuclei were measured in drug-exposed cell lines, in primary human tumor cells and in tissue sections using an immunocytochemical method. Using a mouse model of CP-induced toxicity, the antihistaminic drug diphenhydramine (DIPH) and two methylated derivatives decreased DNA platination in normal tissues and also ameliorated nephrotoxicity, ototoxicity, and neurotoxicity. In addition, DIPH sensitized multiple cancer cell types, particularly ovarian cancer cells, to CP by increasing intracellular uptake, DNA platination, and/or apoptosis in cell lines and in patient-derived primary tumor cells. Mechanistically, DIPH diminished transport capacity of CP efflux pumps MRP2, MRP3, and MRP5 particularly in its C2+C6 bimethylated form. Overall, we demonstrate that DIPH reduces side effects of platinum-based chemotherapy and simultaneously inhibits key mechanisms of platinum resistance. We propose that measuring DNA platination after ex vivo exposure may predict the responsiveness of individual tumors to DIPH-like modulators.

Correction: Generation and Characterisation of Cisplatin-Resistant Non-Small Cell Lung Cancer Cell Lines Displaying a Stem-Like Signature.

[This corrects the article DOI: 10.1371/journal.pone.0054193.].

TFEB-mediated lysosomal biogenesis and lysosomal drug sequestration confer resistance to MEK inhibition in pancreatic cancer.

Oncogenic KRAS mutations are encountered in more than 90% of pancreatic ductal adenocarcinomas. MEK inhibition has failed to procure any clinical benefits in mutant RAS-driven cancers including pancreatic ductal adenocarcinoma (PDAC). To identify potential resistance mechanisms underlying MEK inhibitor (MEKi) resistance in PDAC, we investigated lysosomal drug accumulation in PDAC models both in vitro and in vivo. Mouse PDAC models and human PDAC cell lines as well as human PDAC xenografts treated with the MEK inhibitor trametinib or refametinib led to an enhanced expression of lysosomal markers and enrichment of lysosomal gene sets. A time-dependent, increase in lysosomal content was observed upon MEK inhibition. Strikingly, there was a strong activation of lysosomal biogenesis in cell lines of the classical compared to the basal-like molecular subtype. Increase in lysosomal content was associated with nuclear translocation of the Transcription Factor EB (TFEB) and upregulation of TFEB target genes. siRNA-mediated depletion of TFEB led to a decreased lysosomal biogenesis upon MEK inhibition and potentiated sensitivity. Using LC-MS, we show accumulation of MEKi in the lysosomes of treated cells. Therefore, MEK inhibition triggers lysosomal biogenesis and subsequent drug sequestration. Combined targeting of MEK and lysosomal function may improve sensitivity to MEK inhibition in PDAC.

Pharmacokinetics of a novel anticancer ruthenium complex (KP1019, FFC14A) in a phase I dose-escalation study.

A phase I and pharmacokinetic study was carried out with the new ruthenium complex indazolium trans-[tetrachlorobis(1H-indazole)ruthenate(III)] (KP1019, FFC14A). Seven patients with various types of solid tumours refractory to standard therapy were treated with escalating doses of KP1019 (25-600 mg) twice weekly for 3 weeks. No dose-limiting toxicity occurred. Ruthenium plasma concentration-time profiles after the first dose and under multiple-dose conditions were analysed using a compartmental approach. The pharmacokinetic disposition was characterised by a small volume of distribution, low clearance and long half-life. Only a small fraction of ruthenium was excreted renally. The area under the curve values increased proportionally with dose indicating linear pharmacokinetics.

Boron analysis and boron imaging in biological materials for Boron Neutron Capture Therapy (BNCT).

Boron Neutron Capture Therapy (BNCT) is based on the ability of the stable isotope 10B to capture neutrons, which leads to a nuclear reaction producing an alpha- and a 7Li-particle, both having a high biological effectiveness and a very short range in tissue, being limited to approximately one cell diameter. This opens the possibility for a highly selective cancer therapy. BNCT strongly depends on the selective uptake of 10B in tumor cells and on its distribution inside the cells. The chemical properties of boron and the need to discriminate different isotopes make the investigation of the concentration and distribution of 10B a challenging task. The most advanced techniques to measure and image boron are described, both invasive and non-invasive. The most promising approach for further investigation will be the complementary use of the different techniques to obtain the information that is mandatory for the future of this innovative treatment modality.

Preclinical studies of treosulfan demonstrate potent activity in Ewing's sarcoma.

OBJECTIVES: High-dose chemotherapy with the alkylating agent busulfan has been widely used in the treatment of patients with high-risk Ewing's sarcoma. Because of risks for toxicity, busulfan and radiotherapy can not be applied together, leading to the omission of one effective therapy component. Treosulfan is a derivative of busulfan which has a lower side effect profile than busulfan and which can be used together with radiotherapy. We investigated the effect of treosulfan in a panel of Ewing's sarcoma cell lines on cell survival, cell cycle and apoptosis in vitro and compared it to busulfan. Furthermore, the anti-tumor effect of treosulfan was studied in an orthotopic Ewing's sarcoma mouse xenograft model. METHODS: Cell survival was measured by MTT assay and cell cycle analysis by flow cytometry. Apoptosis was analyzed via detection of DNA fragmentation, Hoechst 33258 staining, Annexin V, and cleavage of caspases-3 and 9. The effect of treosulfan and busulfan on primary tumor growth was assessed in Ewing's sarcoma xenografts in NOD/SCID mice (10 mice per group), pharmacokinetics of treosulfan were analyzed in nude mice. RESULTS: Treosulfan inhibited cell growth to at least 70% in all cell lines at concentrations achievable in vivo. Treosulfan had a greater effect on the inhibition of cell growth at equivalent concentrations compared to busulfan. The growth inhibitory effect of treosulfan at low concentrations was mainly due to a G2 cell cycle arrest, whereas at higher concentrations it was due to apoptosis. Apoptosis was induced at lower concentrations compared to busulfan. In contrast to busulfan, treosulfan induced cell death in an apoptosis-deficient cell line at concentrations achievable in vivo. In mice, treosulfan suppressed tumor growth at dosages of 2,500 and 3,000 mg/kg. Pharmacokinetic exposures of treosulfan in mice were similar to previous reports in human patients. At maximal tolerated dosages treosulfan had a higher anti-tumor activity than busulfan. CONCLUSIONS: Our results suggest that treosulfan has efficacy against Ewing's sarcoma cells in vitro and in mice. Therefore, controlled trials examining the role of treosulfan in patients with Ewing's sarcoma are warranted.

Phase I clinical and pharmacokinetic study of the Novel Raf kinase and vascular endothelial growth factor receptor inhibitor BAY 43-9006 in patients with advanced refractory solid tumors.

PURPOSE: BAY 43-9006 is a novel dual-action Raf kinase and vascular endothelial growth factor receptor inhibitor that inhibits tumor cell proliferation and angiogenesis. This study established the safety and pharmacokinetics of BAY 43-9006 in 69 patients with advanced refractory solid tumors. PATIENTS AND METHODS: BAY 43-9006 (50 to 800 mg) was administered once or twice daily on a varying weekly schedule. Pharmacokinetic sampling was performed in all patients; preliminary tumor response was also assessed. The effect of BAY 43-9006 on phorbol myristate acetate-stimulated ERK phosphorylation in peripheral blood lymphocytes was studied using flow cytometry. RESULTS: Mild to moderate diarrhea was the most common (55%) treatment-related adverse event. The maximum-tolerated dose was 400 mg bid continuous. Dose-limiting toxicities were grade 3 diarrhea and fatigue at 800 mg bid, and grade 3 skin toxicity at 600 mg bid. BAY 43-9006 pharmacokinetics were highly variable for single and multiple dosing, and toxicity did not appear to be dose dependent. Significant decreases of phorbol myristate acetate-stimulated ERK phosphorylation (P < .01) were identified at doses >/= 200 mg bid continuous. Forty-five patients were assessable for efficacy; one patient had a partial response (hepatocellular carcinoma at 400 mg bid continuous), 25 patients had stable disease, with eight lasting > 6 months and five for >12 months. Eighteen patients had progressive disease, and tumor response could not be evaluated in one patient. CONCLUSION: Oral BAY 43-9006 was well tolerated and appeared to provide some clinical benefits. Based on the results of this study, BAY 43-9006 at 400 mg bid continuous is recommended for ongoing and future studies.

Improved Treatment of MT-3 Breast Cancer and Brain Metastases in a Mouse Xenograft by LRP-Targeted Oxaliplatin Liposomes.

The anti-cancer drug oxaliplatin (OxP) has rarely been used to treat breast carcinoma, as it cannot cross the BBB to treat the frequently subsequent brain metastases. Here, we encapsulated OxP in liposomes prepared to reduce side effects and to simultaneously treat primary tumor and brain metastasis. The angiopep LRP-receptor ligand was bound to the vesicular surface for targeting. Targeted and non-targeted OxP liposomes were tested in vitro (binding, uptake, and transcytosis) and in vivo. Liposomes contained 0.65 mg OxP/mL, their mean diameter was 165 nm, and they released 50% of OxP within 8 days at 4 degrees C and within 22 h at 36 degrees C. MDCK cells were used for uptake and transcytosis quantification. Compared to non-targeted liposomes, targeted liposomes showed 12-fold greater uptake, and 2.25-fold higher transcytosis. In vivo efficacy was tested using human MT-3 breast cancer cells transplanted subcutaneously and intracerebrally into female nude mice, and tumor growth inhibition was measured. OxP was injected (6 mg OxP/kg) four times. The best results were obtained with targeted liposomes (T/C: 21% for subcutaneous and 50% for intracerebral). OxP liposomes with a fluid membrane all inhibited MT-3 tumors significantly better than free OxP, with no significant difference between targeted and non-targeted liposomes. The therapeutic effect was accompanied with strong leukopenia and mild thrombocytopenia with all formulations. The newly developed OxP liposomes significantly improved the treatment of subcutaneously and intracerebrally growing breast cancer, but the targeted angiopep-equipped liposomes showed no superior effect in vivo.

Results of a phase I trial of sorafenib (BAY 43-9006) in combination with oxaliplatin in patients with refractory solid tumors, including colorectal cancer.

BACKGROUND: Sorafenib (BAY 43-9006), a multiple kinase inhibitor, has been shown to inhibit tumor growth and tumor angiogenesis by targeting Raf kinase, vascular endothelial growth factor receptor, and platelet-derived growth factor receptor. In phase I studies, sorafenib demonstrated single-agent activity in patients with advanced solid tumors and was successfully combined with oxaliplatin in preclinical studies. This phase I study investigated the safety, pharmacokinetics, and efficacy of sorafenib in combination with oxaliplatin. PATIENTS AND METHODS: Twenty-seven patients with refractory solid tumors were enrolled in the initial dose-escalation part (cohorts 1, 2A, and 2B) and 10 additional patients with oxaliplatin-refractory colorectal cancer were subsequently enrolled in an extension part (cohort 3). Oxaliplatin 130 mg/m2 was given on day 1 of a 3-week cycle and oral sorafenib was administered continuously from day 4 of cycle 1 at 200 mg twice daily (cohort 1) or 400 mg twice daily (cohorts 2A, 2B, and 3). RESULTS: Adverse events were generally mild to moderate and the maximum tolerated dose was not reached. Common adverse events were diarrhea (52% of patients in the dose-escalation part and 20% in the extension part), sensory neuropathy (44% and 20%), and dermatologic toxicities (41% and 80%). No pharmacokinetic interaction between sorafenib and oxaliplatin was detectable. Two patients with gastric cancer had a partial response. Forty-three percent of patients in cohorts 1 and 2A/B and 78% of patients in cohort 3 exhibited stable disease for >or=10 weeks. CONCLUSION: Continuous oral sorafenib 400 mg twice daily was safely combined with oxaliplatin without detectable drug interactions and showed preliminary antitumor activity in this phase I study. This dose is recommended for phase II studies.

Assessing the contribution of the two protein disulfide isomerases PDIA1 and PDIA3 to cisplatin resistance.

Intracellular binding of cisplatin to non-DNA partners, such as proteins, has received increasing attention as an additional mode of action and as mechanism of resistance. We investigated two cisplatin-interacting isoforms of protein disulfide isomerase regarding their contribution to acquired cisplatin resistance using sensitive and resistant A2780/A2780cis ovarian cancer cells. Cisplatin cytotoxicity was assessed after knockdown of either protein disulfide isomerase family A member 1 (PDIA1) or protein disulfide isomerase family A member 3 (PDIA3). Whereas PDIA1 knockdown led to increased cytotoxicity in resistant A2780cis cells, PDIA3 knockdown showed no influence on cytotoxicity. Coincubation with propynoic acid carbamoyl methyl amide 31 (PACMA31), a PDIA1 inhibitor, resensitized A2780cis cells to cisplatin treatment. Determination of the combination index revealed that the combination of cisplatin and PACMA31 acts synergistically. Our results warrant further evaluation of PDIA1 as promising target for chemotherapy, and its inhibition by PACMA31 as a new therapeutic approach.