Drug Concentration In Tumor Research Articles

N-Butyl-2-cyanoacrylate-based injectable and in situ-forming implants for efficient intratumoral chemotherapy

The local delivery of chemotherapeutic drugs to tumor sites is an effective approach for achieving therapeutic drug concentrations in solid tumors. Injectable implants with the ability to form in situ represent one of the most promising technologies for intratumoral chemotherapy. However, many issues must be resolved before these implants can be applied in clinical practice. Herein, we report a novel injectable in situ-forming implant system composed of n-butyl-2-cyanoacrylate (NBCA) and ethyl oleate, and the sol–gel phase transition is activated by anions in body fluids or blood. This newly developed injectable NBCA ethyl oleate implant (INEI) is biodegradable, biocompatible, and non-toxic. INEI solidifies in several seconds after exposure to body fluids or blood, and the implant’s in vivo degradation time can be controlled. In addition, the pore sizes formed by the polymerization of NBCA can be decreased by increasing the NBCA concentration in the implants. Therefore, the drug retention/release time can be adjusted from a few weeks to several months by changing the concentration of NBCA in the implant formulation. Anti-tumor experiments in animal models showed that the average growth inhibition rate of xenografted human breast cancer cells by the paclitaxel-loaded INEI (40% NBCA) was 80%, and they also indicated that tumors in some of the mice were completely eliminated by just a single dosage injection. For the epirubicin-loaded INEI (50% NBCA), the average growth inhibition rate of xenografted human liver cancer cells was 58%. Thus, the chemotherapeutic drug-loaded INEIs exhibited excellent therapeutic efficacy for local chemotherapy.

Hyaluronic acid decorated pluronic P85 solid lipid nanoparticles as a potential carrier to overcome multidrug resistance in cervical and breast cancer.

This work aimed to develop hyaluronic acid (HA) decorated pluronic 85 (P85) coated solid lipid nanoparticles (SLN) loaded with paclitaxel (HA-PTX-P85-SLN) and to evaluate its potential to overcome drug resistance and to increase antitumor efficacy in mice bearing cervical and breast tumor. P85-Distearoyl Phosphoethanolamine (DSPE) was synthesized from P85 and DSPE by coupling in the presence of 1,10-carbonyldiimidazole (CDI) as a catalyst. The SLN were prepared by the hot homogenization technique and electrostatic interaction. PTX-loaded SLN was characterized for mean diameter, zeta potential, morphology, entrapment efficiency (EE), drug loading capacity (LC) and in vitro drug release. In vivo animal evaluation containing antitumor effect, pharmacokinetics and biodistribution were conducted in mice bearing cervical and breast tumor. The HA-PTX-P85-SLN showed a mean diameter of 160.3nm, negative zeta potential (-31.6mV), EE of 88.2%, and LC of 4.9%. PTX from HA-PTX-P85-SLN exhibited greater sustained drug release profiles compared free PTX. Pharmacokinetics results indicated that HA-PTX-P85-SLN exhibited a 5.5-fold increase in AUC in comparison to free PTX. Biodistribution results revealed that HA-PTX-P85-SLN exhibited higher tumor drug concentration compared with free PTX.

A Computational/Experimental Assessment of Antitumor Activity of Polymer Nanoassemblies for pH-Controlled Drug Delivery to Primary and Metastatic Tumors.

Polymer nanoassemblies (PNAs) with drug release fine-tuned to occur in acidic tumor regions (pH < 7) while sparing normal tissues (pH = 7.4) were previously shown to hold promise as nanoparticle drug carriers to effectively suppress tumor growth with reduced systemic toxicity. However, therapeutic benefits of pH-controlled drug delivery remain elusive due to complex interactions between the drug carriers, tumor cells with varying drug sensitivity, and the tumor microenvironment. We implement a combined computational and experimental approach to evaluate the in vivo antitumor activity of acid-sensitive PNAs controlling drug release in pH5 ~ 7.4 at different rates [PNA1 (fastest) > PNA2 > PNA3 (slowest)]. Computational simulations projecting the transport, drug release, and antitumor activity of PNAs in primary and metastatic tumor models of colorectal cancer correspond well with experimental observations in vivo. The simulations also reveal that all PNAs could reach peak drug concentrations in tumors at 11h post injection, while PNAs with slower drug release (PNA2 and PNA3) reduced tumor size more effectively than fast drug releasing PNA1 (24.5 and 20.3 vs 7.5%, respectively, as fraction of untreated control). A combined computational/experimental approach may help to evaluate pH-controlled drug delivery targeting aggressive tumors that have substantial acidity.

Multifunctional Mixed Micelles Cross-Assembled from Various Polyurethanes for Tumor Therapy.

A challenge in the development of multifunctional drug delivery systems is to establish a reasonable and effective synthetic route for multifunctional polymer preparation. Herein, we propose a unique protocol to prepare multifunctional micelles by a cross-assembly process using three different functional polyurethanes incorporating acidic sensitive hydrazone, folic acid for active targeting, and gemini quaternary ammonium (GQA) as efficient cell uptake ligands, respectively. These multifunctional mixed micelles (GFHPMs) have been endowed tunable particle sizes and zeta potential and a unique three-order-layer cross-assemble structure. Their drug-loading contents have been significantly improved, and drug release profiles displayed controlled release of their payloads under acid condition. The folate and GQA ligands showed a synergistic effect to enhance the cell uptake. Biodistribution and antitumor effect of these micelles were systematically investigated in vivo, the mixed micelles could penetrate into the depths of tumors, and drug concentrations in tumors reached the maximum of 6.5% ID/g at 24 h, resulting in an excellent therapeutic effect that the volumes of tumors treated with GFHPM are five times smaller than those treated with blank micelles. Our present work provides an effective approach to the design of multifunctional nanocarriers for tumor-targeted and programmed intracellular drug delivery.

Targeting, bio distributive and tumor growth inhibiting characterization of anti-HER2 affibody coupling to liposomal doxorubicin using BALB/c mice bearing TUBO tumors

Human epidermal growth factor receptor 2 (HER2) is overexpressed in 20–30% of breast cancer tumors. In the current investigation, we exploited such a feature and utilized an anti-HER2 affibody (ZHER2:477) in combination with a pegylated liposomal doxorubicin (PLD) for concurrent passive and active targeting of HER2 overexpressing TUBO tumor, using BALB/c mice. It was determined that the affibody coupled liposomes (affisomes) was capable of increasing doxorubicin (Dox) delivery to HER2+ cells (SK-BR-3 and TUBO cells), while transferring drug similarly as low as naïve PLD to HER2- MDA-MB-231 cells. This also resulted in selectively enhance cytotoxicity. The veracity of targeting was further assessed utilizing DiD lipophilic tracer model liposomes via competition assay. An approximated 10 ligand/liposome integration caused Dox delivery at 50% of maximal delivery capacity (Kd). Such integration did not alter Dox release in vitro, while it affected the serum clearance profile. Affibody integration to PLD increased drug concentration in tumor and led to significantly further augmentation of drug in liver and spleen compared to those of PLD. Overall, such differences led to prolonging the mice life spans as compared to PLD.

Low-Frequency Ultrasound Enhances Paclitaxel Efficacy in EMT6 Subcutaneous Tumors in Balb/c Mice

Background: The objective of this study was to explore the effects of 30 kHz ultrasound on the efficacy of paclitaxel in subcutaneous breast tumors in Balb/c mice in vivo. Materials and Methods: 40 Balb/c female mice were divided into 5 groups: model control group, paclitaxel intraperitoneal (ip) group (20 mg/kg, ip, at 3 day intervals for a total of 3 doses (q3d×3)), paclitaxel intratumoral (it) group (20 mg/kg, it, q3d×3), paclitaxel intraperitoneal (20 mg/kg, ip, q3d×3) combined with low-frequency ultrasound (LFU) group, and paclitaxel intratumoral (20 mg/kg, it, q3d×3) combined with LFU group. Ultrasound parameters were 30 kHz, 200 MW intensity, 15 min, q3d×3. The antitumoral effect was determined by examining the tumor weight in subcutaneously inoculated EMT6 breast carcinoma models in Balb/c mice. All subcutaneous tumors were examined using high performance liquid chromatography (HPLC) upon completion of the experiments. Drug concentrations in the subcutaneous tumors were also analyzed using HPLC. Finally, paraffin sections of the subcutaneous tumors were made, and after hematoxylin and eosin staining, the tumor morphology was examined under a light microscope. Results: LFU combined with paclitaxel significantly restrained tumor growth in transplanted subcutaneous EMT6 tumors in Balb/c mice, and this effect correlated with increased local concentrations of paclitaxel in the tumors. Body weight measurement did not reveal significant adverse effects on the Balb/c mice during the study. Conclusion: LFU combined with paclitaxel has a significant synergistic effect in the treatment of breast cancer.

Abstract P6-13-22: Pharmacodynamics and consequences of PI3K inhibition in ER+ breast tumors

Abstract PI3K inhibitors have shown promise for the treatment of anti-estrogen-resistant ER+ breast cancers. Current PI3K inhibitor treatment regimens may incompletely and transiently inhibit the pathway in carcinomas, and are accompanied by significant adverse effects in patients. We hypothesized that short-term, complete inhibition of PI3K will have a greater anti-tumor effect and reduce systemic toxicity compared to chronic, partial inhibition. Pharmacokinetic analysis of the orally available pan-PI3K inhibitor GDC-0941 at low (100 mg/kg) and high (800 mg/kg) doses in mice revealed that plasma levels peaked after 15-30 min, and decreased below the limit of detection within 24 h (low dose) and 72 h (high dose), respectively. Administering 2 doses at 100 mg/kg 12 h apart provided continuous drug exposure. Drug pharmacokinetics in MCF-7 tumors was similar. Mice bearing s.c. MCF-7 tumors were treated with the anti-estrogen fulvestrant (fulv; 5 mg/wk) three days before GDC-0941 treatment to assess pharmacodynamic effects. Phospho-AKT and -S6 levels (markers of PI3K and mTORC1 activities, respectively) were inversely correlated with tumor drug concentrations. Mice bearing MCF-7, fulv-resistant T47D/FR, or HCC-003 patient-derived xenografts were treated with vehicle, fulv, GDC-0941 (100 mg/kg QD 5 d/wk; 100 mg/kg BID 3 d on/4 d off; 800 mg/kg QW), or combinations. Tumor growth curves indicated that different schedules of PI3K inhibition with fulv similarly induced tumor regression. Molecular analysis of MCF-7 tumors showed that fulv plus GDC-0941 QW induced 30.14% apoptosis (assessed by TUNEL) at 48 h, which dropped to baseline (2.72%) at 72 h. Fulv plus GDC-0941 BID induced 18.27% apoptosis at 24 h, and maintained apoptosis rate near 10% until 96 h (when GDC-0941 washed out), which is a rate similar to that observed with fulv plus GDC-0941 QD. Fulv plus GDC-0941 QW decreased cell proliferation (assessed by geminin and Ki67 staining) from 34.89% (baseline) to 11.46%, which rebounded to 60.54% at the time of GDC-0941 washout (at 96 h). Fulv plus GDC-0941 QD or BID modestly decreased cell proliferation to 28.84% and 24.32%, respectively, after 24 h, which returned to baseline after 36 h and 72 h, respectively, then maintained the level for a week. Temporal analysis of PI3K signaling revealed that fulv plus GDC-0941 QW and BID maximally decreased phospho-AKT levels after 3 h, which returned to baseline within 48 h and 72 h, respectively. With fulv + GDC-0941 QD, phospho-AKT levels decreased after 3 h, but rebounded to baseline within 24 h. These results indicate that 2 approaches to PI3K inhibition provide similar anti-tumor efficacy: 1) complete/intermittent (QW) PI3K inhibition induces a burst of apoptosis with a rebound in cell proliferation after drug clearance; and 2) metronomic/repeated (QD) PI3K inhibition repeatedly induces a smaller amount of apoptosis without significantly affecting cell proliferation. These findings may inform clinical testing of PI3K inhibitors to maximize therapeutic index. Citation Format: Yang W, Bean J, Hosford S, Lloye D, Liu S, Salphati L, Pang J, Zhang X, Nannini M, Miller TW. Pharmacodynamics and consequences of PI3K inhibition in ER+ breast tumors. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-13-22.

MRI monitoring of nanocarrier accumulation and release using Gadolinium-SPIO co-labelled thermosensitive liposomes.

Encapsulation of anticancer drugs in triggerable nanocarriers can beneficially modify pharmacokinetics and biodistribution of chemotherapeutic drugs, and consequently increase tumor drug concentration and efficacy, while reducing side effects. Thermosensitive liposomes release their contents triggered by hyperthermia, which can be, for example, precisely delivered using an MR Imaging-guided focused ultrasound procedure. In such a scenario, it is attractive to demonstrate the accumulation of liposomes before applying hyperthermia, as well as to document the release of liposome content using MRI. To address this need, thermosensitive liposomes were developed and characterized, which were doubly loaded by iron oxide nanoparticles and Gd-chelate, as opposed to loading with a single contrast agent. When intact, the transverse relaxivity of the liposomes is high allowing detection of carriers in tissue. After heating the longitudinal relaxivity steeply increases indicating release of the small molecular contents. By choosing the appropriate MR sequences, availability and release can be evaluated without interference of one contrast agent with the other. Copyright © 2016 John Wiley & Sons, Ltd.

Роль nab-паклитаксела в лечении больных метастатическим раком молочной железы

Nab-paclitaxel is nanoparticle albumin-bound paclitaxel. Nab-paclitaxel is free from any kind of solvent and thus reduces the risk of hypersensitivity reactions and other side effects, compared with standard taxanes (paclitaxel, docetaxel). There is no need to use premedication with glucocorticoids and antihistamines during nab-paclitaxel application. In addition, several studies have demonstrated that nab-paclitaxel allows achieving a higher drug concentration in tumor. The article deals with the basic studies of nab-paclitaxel application using different doses and introduction regimens in patients with metastatic breast cancer. We show the algorithm for optimal use of nab-paclitaxel in different clinical cases.

Electrospun PLA/MWCNTs composite nanofibers for combined chemo- and photothermal therapy

Carbon nanotubes are effective thermal generators by absorbing near-infrared radiation (NIR). In this study, multiwalled carbon nanotubes (MWCNTs) and doxorubicin (DOX) were successfully electrospun into the poly-l-lactic acid (PLLA) nanofibers. It is confirmed that NIR radiation could not only initiate burst release of DOX from the fibers due to the relatively low glass transition temperature (Tg) of PLLA, but also significantly increase the temperature of fibers-covering tumor site. The multifunctional fibers showed increased cytotoxicity both in vitro and in vivo by the combination of photothermal induced hyperthermia and chemotherapy with DOX. This drug delivery system could be very useful and convenient in future clinical applications for localized cancer therapy. Statement of SignificanceCombination of chemo- and photothermal therapy has been widely researched owing to its enhanced cancer treatment efficacy. In this study, chemotherapy and photothermal therapy were integrated into one single system using electrospun DOX/MWCNTs loaded PLLA nanofiber mats and the anti-cancer efficacy of the fibers was studied in vivo for the first time. The effective NIR irradiation control showed a typical switch on/off effect on the release behavior of drug. As local delivery system, the fibers maximize the drug concentration in tumor and keep the MWCNTs in the surroundings of tumor, thus allowing a repeated localized heating. The high porosity of nanofibers is easy for cell binding, which may present an attractive alternative for local hyperthermia treatment of easily metastasizing tumors.

Abstract 5444: Development of a noninvasive assay to determine drug concentration in tumor during hsp90 inhibitor therapy

Abstract As molecularly targeted agents assume a more prominent role in anticancer therapy there is a growing need to determine in a noninvasive manner whether the target is being engaged and to what extent such drug-target binding results in desirable effects. We address this need in the context of Hsp90, a target of significant value and one in critical need for such assessment tools, by combining a novel chemical tool selective for tumor Hsp90 with PET imaging and mathematical modeling. The chemical tool is [124I]-PU-H71, the iodine-124 radiolabeled analog of the potent Hsp90 inhibitor PU-H71, which can be administered in tracer quantities for PET imaging. The resulting diagnostic, PU-PET, has been optimized and validated preclinically in mouse models of cancer and then translated to the clinic. The exquisite design of this assay is based on three essential concepts as it relates to the target (Hsp90) as well as to the PET tracer (124I-PU-H71). First, the target is “oncogenic” Hsp90 and has been shown by numerous biochemical and pharmacokinetic studies to have a strong affinity for inhibitors and a very low koff resulting in selective and prolonged retention in tumor. Secondly, the tracer incorporates a 124I in place of the naturally occurring 127I in the structure of PU-H71 and therefore there is no change in the chemical structure. This feature in a PET tracer intended as a companion diagnostic is unprecedented and ensures that the PK properties are identical to the therapeutic agent (PU-H71). Finally, the radionuclide 124I has a four-day half-life and thus is well-suited to monitor the extended tumor retention profile observed for Hsp90 inhibitors. We here demonstrate that this PET assay informs on Hsp90 targeting in individual tumors in real time and provides accurate tumor drug concentrations for at least four chemically distinct Hsp90 drugs. In contrast, we find that plasma pharmacokinetics is not predictive of intratumor parameters and therefore provides limited value in estimating target engagement. Using PU-PET we demonstrate that at least one Hsp90 inhibitor exhibits tumor targeting and retention in humans, delivering and retaining therapeutic, micromolar, concentrations at safe doses. PU-PET is currently being evaluated in Phase 0/1 (NCT01269593) clinical trials as a noninvasive companion diagnostic to determine intratumoral concentration as well as to identify those patients who would best benefit from Hsp90 inhibitor therapy. This diagnostic assay is intended to be incorporated into future Phase 2 clinical trials in order to preselect those patients who would most likely benefit from Hsp90 inhibitor treatment. Citation Format: Tony Taldone, Nagavarakishore Pillarsetty, Mark PS Dunphy, John F. Gerecitano, Eloisi Caldas-Lopes, Brad Beattie, Radu I. Peter, Yanlong Kang, Anna Rodina, Pengrong Yan, Erica M. DaGama Gomes, Alexander Bolaender, Christina Pressl, Blesida Punzalan, Anson Ku, Thomas Ku, Smit Shah, Mohammad Uddin, Mei H. Chen, Elmer Santos, Jacek Koziorowski, Adriana Corben, Shanu Modi, Komal Jhaveri, Oscar Lin, Efsevia Vakiani, Yelena Janjigian, Pat Zanzonico, Clifford Hudis, Steven M. Larson, Jason S. Lewis, Gabriela Chiosis. Development of a noninvasive assay to determine drug concentration in tumor during hsp90 inhibitor therapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5444. doi:10.1158/1538-7445.AM2015-5444

Abstract 1653: BGB-290: A highly potent and specific PARP1/2 inhibitor potentiates anti-tumor activity of chemotherapeutics in patient biopsy derived SCLC models

Abstract Small cell lung cancer (SCLC) is one of the most aggressive forms of lung cancer with a 5-year survival rate of less than 10%. Despite the initial high response rate to the frontline platinum based chemotherapy, relapse is common and rapid. The clinical activity of PARP inhibitors has shown good correlation with platinum sensitivity in breast and ovarian cancers. Thus, there is good rationale to test PARP inhibitors in SCLC. BGB-290 is a novel PARP-1/2 inhibitor, which is currently under clinical investigation in solid tumors. In this study, we evaluated the in vitro and in vivo activities of BGB-290, and its combination activity with chemotherapies in patient biopsy derived SCLC xenograft models. In the biochemical assays, BGB-290 demonstrated great potency for PARP1/2 (IC50 = 0.83 and 0.11 nM, respectively) and high selectivity over other PARP enzymes. The DNA-trapping activity of BGB-290 was measured in a fluorescence polarization (FP) binding assay. BGB-290 showed potent DNA-trapping activity with IC50 of 13 nM. In the cellular assays, BGB-290 inhibited intracellular PAR formation with an IC50 of 0.24 nM. Tumor cell lines with homologous recombination defects were profoundly sensitive to BGB-290. Oral administration of BGB-290 resulted in time-dependent and dose-dependent inhibition of PARylation in MDA-MB-436 (BRCA1 mutant) breast cancer xenograft, correlating well with the tumor drug concentrations. Compared to olaparib, BGB-290 induced PAR inhibition was more sustained. Consistent with this finding, BGB-290 demonstrated excellent anti-tumor activity in this model, over 10-fold more potent than olaparib. In a panel of 7 SCLC cell lines tested, 3 of them were sensitive to BGB-290. SCLC primary tumor models were established in house using patient biopsy samples obtained from Beijing Cancer Hospital. The anti-tumor activities of BGB-290 as single agent or in combination with etoposide/carboplatin (E/C) were evaluated in 8 SCLC primary tumor models. BGB-290 showed weak single agent activity in these models. Six of the 8 models (75%) were sensitive to E/C treatment, consistent with the clinical response observed in these patients. Addition of BGB-290 as concomitant treatment or maintenance therapy significantly prolonged the response duration in these chemo-sensitive models. In the two chemo-insensitive models, BGB-290 and E/C combo was less effective. Addition of BGB-290 to the chemo regiment was well-tolerated throughout the study. In conclusion, BGB-290 is a potent and selective inhibitor of PARP1/2. It is highly active both in vitro and in vivo in BRCA mutant tumors. BGB-290 has also demonstrated good combination activity with chemotherapeutics in patient biopsy derived SCLC models, supporting further investigation in the clinic. Citation Format: Zhiyu Tang, Ye Liu, Qin Zhen, Bo Ren, Hexiang Wang, Zhenyan Shi, Wenfeng Gong, Yong Liu, Xing Wang, Yajuan Gao, Fenglong Yu, Yiyuan Wu, Bing Jiang, Xuebing Sun, Min Wei, Changyou Zhou, Lusong Luo, Zhengxiang Li, Jiangyong Yu, Jun Zhao, Jie Wang, Lai Wang. BGB-290: A highly potent and specific PARP1/2 inhibitor potentiates anti-tumor activity of chemotherapeutics in patient biopsy derived SCLC models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1653. doi:10.1158/1538-7445.AM2015-1653

Abstract P5-20-03: Understanding pharmacodynamics and consequences of PI3K inhibition in ER+ breast tumors

Abstract PI3K inhibitors have shown promise for the treatment of anti-estrogen-resistant breast cancers. Current PI3K inhibitor treatment regimens incompletely and transiently inhibit the pathway in carcinomas, and are accompanied by adverse effects in patients. We found that different periods of PI3K inhibition (12, 24, 36 h) potentiated anti-estrogen-induced apoptosis and inhibition of proliferation to similar extents in cultured ER+ cells. We thus hypothesized that short-term, complete inhibition of PI3K will have a greater anti-tumor effect and reduced systemic toxicity than chronic, partial inhibition. Pharmacokinetic analysis of the orally available pan-PI3K inhibitor GDC-0941 at low (100 mg/kg) and high (800 mg/kg) doses in mice revealed that plasma levels peaked after 15-30 min. (18.6 uM and 20.7 uM, respectively), and decreased to a plateau phase after 1 h that was maintained for 8 h with low dose (6.8-10.7 uM) and 23 h with high dose (7.9-15 uM). We performed MCF-7 tumor pharmacokinetic analyses with low and high doses, and with 2 low doses administered 12 hours apart. Tumor GDC-0941 levels peaked after 9 h (1.6 uM with low-dose; 16.9 uM with high-dose). The second low dose increased tumor drug concentrations to 3.2 uM at 9 h after the second dose, compared to 1.6 uM at 9 h after the first dose. After 48 h, tumor drug concentrations decreased to 0 uM with low dose, and to 4.5 uM with high dose. Mice bearing MCF-7 tumors were treated with fulvestrant (5 mg/wk). Three days later, GDC-0941 was administered to assess pharmacodynamic effects. Phospho-AKT and -S6 levels (markers of PI3K and mTORC1 activities, respectively) were maximally suppressed after 1 h and 3 h of high- and low-dose treatments, respectively, returned to baseline within 16 h after low-dose treatment, and remained suppressed for 36 h following high-dose treatment. PARP cleavage (marker of apoptosis) occurred within 1 h and 3 h of high- and low-dose treatments, and increased over time. Re-treatment of mice with low-dose GDC-0941 after 12 h induced continued inhibition of PI3K and mTORC1 for 9-12 h, suggesting that BID low-dose treatment may be sufficient to continually inhibit PI3K. Comparison of high-dose and low-dose BID tumors showed that these treatments induced similar amounts of PI3K inhibition and PARP cleavage at 21-24 h. Mice bearing MCF-7 or fulvestrant-resistant T47D/FR tumors were treated with vehicle, fulvestrant, GDC-0941 (100 mg/kg QD 5 d/wk; 100 mg/kg BID 3 d/wk, 800 mg/kg QW), or combinations of fulvestrant and GDC-0941. Drug combinations induced tumor regression, fulvestrant did not affect tumor growth, high-dose GDC-0941 QW slowed tumor growth, and low-dose GDC-0941 QD or BID appreciably inhibited tumor growth. However, there was no significant difference among doses and schedules of GDC-0941 in the context of a fulvestrant backbone in either tumor model. These data suggest that transient/metronomic (QD, BID) and chronic/infrequent (QW) PI3K inhibition may provide similar anti-tumor efficacy in combination with an anti-estrogen. However, these tumor growth data conflict with cell fate data indicating that high-dose GDC-0941 induced much more apoptosis than low-dose GDC-0941. Ongoing studies will reveal how different schedules of PI3K inhibition shape tumor biology. Citation Format: Wei Yang, Jennifer R Bean, Lloye Dillon, Laurent Salphati, Jodie Pang, Xiaolin Zhang, Michelle Nannini Pepe, Todd W Miller. Understanding pharmacodynamics and consequences of PI3K inhibition in ER+ breast tumors [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-20-03.

Abstract P6-11-02: Spatial distribution of veliparib measured by matrix assisted laser desorption ionization mass spectrometry in triple negative breast cancer tumors

Abstract Background: Veliparib, an inhibitor of Poly(ADP-ribose) polymerase (PARPi), in combination with DNA-damaging agents showed significant efficacy, especially in triple negative breast cancer (TNBC) patients. However, in I-SPY 2, approximately 42% of TNBC did not optimally respond to the veliparib based treatment. To exert therapeutic effect, drugs such as veliparib or the DNA damaging agent carboplatin must reach cancer cells at an adequate concentration. Differences within the microenvironment of the tumor (e.g. reduced vascular density and leaky endothelium) are responsible for variability in the uptake and distribution of the drug in the tumor. We hypothesize that heterogeneous or insufficient drug concentrations in the solid tumor lead to inadequate response to PARPi in some TNBC patients. First we performed a mouse xenograft study to determine the penetration and distribution of veliparib and carboplatin in TNBC tumors in mice. Methods: 1*106 MDA.MB.231, HCC70 or MDA.MB.436 cells were injected bilaterally into mamamary fat pad of a total of 36 Beige SCID mice. When the tumors exceeded 200 mm3, veliparib (20mg/kg or 60mg/kg) or placebo was orally administered 3 times daily for 3 days + Carboplatin 60mg/kg on day 1+2. These doses and dosing schedules were estimated to result equivalent plasma and tumor concentrations in mice compared to the doses currently used in clinical trials. Mice were euthanized 3 hours after the last dose of veliparib and tumors, and muscle tissues were obtained. In addition, control tissues were spiked with a broad range of concentrations of veliparib. The spatial distribution of the drugs in the tumor tissue was measured using Matrix-assisted laser desorption/ ionization mass spectrometric imaging (MALDI). The protonated molecular ion at m/z 245.1 was used to construct 2D ion maps of the tissue showing relative quantitation of drug levels. H&amp;E staining was performed to characterize the tumors. Results: Veliparib in control tissues was detected at very low concentrations with a range of detection between 100 fmol-1nmol. After dosing, veliparib penetrates into the tumors and was detectable at both dose levels. However, drug distribution within the tumors was observed to be inhomogeneous. In spots where the drug accumulated, necrosis was observed. Veliparib accumulated in spots in the tumor and near the rim of the tumor. Differences between cell lines were observed, with the largest accumulation at the rim in BRCA mutated cells. Conclusions: Veliparib can be measured using MALDI with good specificity and sensitivity and using concentrations equivalent to patients. TNBC tumors show largely heterogeneous distribution of PARPi, with accumulation in the pushing margings of the tumor. Future analyses will determine whether this heterogeneity in drug distribution explains variability in response to PARPi therapies. Citation Format: Imke H Bartelink, Brendan Prideaux, Byron Hann, Gregor Krings, Jean-Phillippe Coppe, Lamorna Swigart-Brown, Pei Rong Evelyn Lee, Laura Esserman, Douglas Yee, Denise Wolf, Rada M Savic, Laura van t Veer. Spatial distribution of veliparib measured by matrix assisted laser desorption ionization mass spectrometry in triple negative breast cancer tumors [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-11-02.

Synthesis and therapeutic effect of styrene–maleic acid copolymer‐conjugated pirarubicin

Previously, we prepared a pirarubicin (THP)-encapsulated micellar drug using styrene–maleic acid copolymer (SMA) as the drug carrier, in which active THP was non-covalently encapsulated. We have now developed covalently conjugated SMA-THP (SMA-THP conjugate) for further investigation toward clinical development, because covalently linked polymer–drug conjugates are known to be more stable in circulation than drug-encapsulated micelles. The SMA-THP conjugate also formed micelles and showed albumin binding capacity in aqueous solution, which suggested that this conjugate behaved as a macromolecule during blood circulation. Consequently, SMA-THP conjugate showed significantly prolonged circulation time compared to free THP and high tumor-targeting efficiency by the enhanced permeability and retention (EPR) effect. As a result, remarkable antitumor effect was achieved against two types of tumors in mice without apparent adverse effects. Significantly, metastatic lung tumor also showed the EPR effect, and this conjugate reduced metastatic tumor in the lung almost completely at 30 mg/kg once i.v. (less than one-fifth of the maximum tolerable dose). Although SMA-THP conjugate per se has little cytotoxicity in vitro (1/100 of free drug THP), tumor-targeted accumulation by the EPR effect ensures sufficient drug concentrations in tumor to produce an antitumor effect, whereas toxicity to normal tissues is much less. These findings suggest the potential of SMA-THP conjugate as a highly favorable candidate for anticancer nanomedicine with good stability and tumor-targeting properties in vivo.

Biocompatible Microemulsion Modifies the Tissue Distribution of Doxorubicin

The incorporation of doxorubicin (DOX) in a microemulsion (DOX-ME) has shown beneficial consequences by reducing the cardiotoxic effects of DOX. The aim of this study was to determine the distribution of DOX-ME in Ehrlich solid tumor (EST) and the heart, and compare it with that of free DOX. The distribution study was conducted with female Swiss mice with EST (n = 7 per group; 20-25 g). Animals received a single dose (10 mg/kg, i.p.) of DOX or DOX-ME 7 days after tumor inoculation. Fifteen minutes after administration, the animals were sacrificed, and the tumor and heart tissues were taken for immediate analysis by ultra-performance liquid chromatography. No difference was observed in DOX concentration in tumor tissue between DOX and DOX-ME administration. However, the most remarkable result in this study was the statistically significant reduction in DOX concentration in heart tissue of animals given DOX-ME. Mean DOX concentration in heart tissue was 0.92 ± 0.54 ng mg(-1) for DOX-ME and 1.85 ± 0.34 ng mg(-1) for free DOX. In conclusion, DOX-ME provides a better tissue distribution profile, with a lower drug concentration in heart tissue but still comparable tumor drug concentration, which indicates that antitumor activity would not be compromised.

Spatial distribution of veliparib measured by matrix-assisted laser desorption ionization mass spectrometry in triple-negative breast cancer tumors.

161 Background: Veliparib is a potent inhibitor of the protein Poly(ADP-ribose) polymerase (PARP). Although effective, in the first clinical trials some TNBC patients fail to respond. We hypothesize that heterogeneous or insufficient drug concentrations in the solid tumor lead to inadequate response to PARPi in some TNBC patients. First we performed a mouse xenograft study to determine the penetration and distribution of veliparib in TNBC tumors in mice. Methods: MDA.MB.231 cells were injected bilaterally into mamamary fat pad of 10 Beige SCID mice. Veliparib (20mg/kg or 60mg/kg) or placebo was orally administered 3 times daily for 3 days. These doses and dosing schedules were estimated to result in equivalent plasma and tumor concentrations in mice compared to the doses currently used in clinical trials. Mice were euthanized 3 hours after the last dose of veliparib and tumors, liver and muscle tissues were obtained. In addition, control tissues were spiked with a broad range of concentrations of veliparib. The spatial distribution of the drugs in the tumor tissue was measured using Matrix-assisted laser desorption/ionization mass spectrometric imaging (MALDI). The protonated molecular ion at m/z245.1 was used to construct 2D ion maps of the tissue showing relative quantitation of drug levels. HE staining was performed to characterize the tumors. Results: Veliparib in control tissues was detected at very low concentrations with a range of detection between 100 fmol-1nmol. After dosing, veliparib penetrates into the tumors and was detectable at both dose levels. However, drug distribution within the tumors was observed to be inhomogeneous. In spots where the drug accumulated, necrosis was observed. Conclusions: Veliparib can be measured using MALDI with good specificity and sensitivity and using concentrations equivalent to patients. TNBC tumors show largely heterogeneous distribution of PARPi. Future analyses will determine whether this heterogeneity in drug distribution explains variability in response to PARPi therapies.

Formulation design and evaluation of liposomal sepantronium bromide (YM155), a small-molecule survivin suppressant, based on pharmacokinetic modeling and simulation.

Sepantronium bromide (YM155) is administered by 168-hour continuous infusions in clinical studies due to its time-dependent pharmacological efficacy and rapid elimination from plasma. To enable more convenient administration, i.e., bolus injections with low frequency, we prepared liposomal formulations of YM155 and evaluated their antitumor activities. A kinetic simulation model of liposomal YM155 to predict the free drug concentration in both tumor and plasma was developed. A liposomal formulation with the target drug release rate was prepared based on the simulation. Antitumor activities of the formulation were examined in various tumor xenograft mouse models. In addition, antitumor activities of liposomal formulations with different drug release rates were compared in order to confirm the validity of the simulation-based prediction. Liposomal YM155 with the release half-life of 48h was prepared as a promising formulation. This formulation showed significantly potent antitumor activities in tumor xenograft models by weekly bolus injections. Further studies demonstrated that this release rate was optimal for YM155 in terms of both efficacy and safety. We successfully developed a liposomal formulation of YM155 that could substitute for long-term continuous infusion of the drug solution in clinical settings by being given as weekly bolus injections.

Pharmacokinetics and Antitumor Efficacy of Chemoembolization Using 40 µm Irinotecan-Loaded Microspheres in a Rabbit Liver Tumor Model

PurposeTo evaluate the pharmacokinetics and antitumor efficacy of 40 μm irinotecan-loaded drug-eluting microspheres (Embozene TANDEM Microspheres; CeloNova BioSciences, Inc, San Antonio, Texas) (TANDEM-IRI). Materials and MethodsThe following three groups included eight VX2 rabbits each: group 1, full-loaded (50 mg irinotecan/1 mL TANDEM)/high-dose injection (1 mg irinotecan/kg); group 2, full-loaded (50 mg irinotecan/1 mL TANDEM)/low-dose injection (0.5 mg irinotecan/kg); and group 3, half-loaded (25 mg irinotecan/1 mL TANDEM)/low-dose injection (0.5 mg irinotecan/kg). Irinotecan and SN-38 in the plasma and tumors were measured within 72 hours. Histologic examinations were conducted on days 1, 3, and 7. ResultsSerum irinotecan levels remained near the maximum concentration for 180 minutes after transarterial chemoembolization; in group 1, levels were 351.4 ng/mL at 30 minutes, 329.0 ng/mL at 60 minutes, and 333.5 ng/mL at 180 minutes. The area under the curve for 0–24 hours of irinotecan in group 1 was approximately two times higher than the same value in groups 2 and 3. High irinotecan and SN-38 concentrations in the tumors were measured at 24 hours and 72 hours. After transarterial chemoembolization, levels of liver enzymes aspartate aminotransferase and alkaline phosphatase were significantly higher in group 1 compared with groups 2 and 3. Histologic findings showed microspheres had deeply penetrated into tumors. Significantly higher tumor necrosis ratios were observed in groups 1 (86.6%–90.0%) and 3 (90.0%–100%) compared with group 2 (63.3%–70%) (P = .031 and P = .016). ConclusionsSlow drug release with high drug concentration in tumors can be provided with 40 μm TANDEM-IRI. When complete arterial embolization is performed, the dose of irinotecan loaded on 40 μm TANDEM microspheres can be reduced while maintaining efficacy.

Apoptosis imaging for monitoring DR5 antibody accumulation and pharmacodynamics in brain tumors noninvasively.

High-grade gliomas often possess an impaired blood-brain barrier (BBB), which allows delivery of large molecules to brain tumors. However, achieving optimal drug concentrations in brain tumors remains a significant hurdle for treating patients successfully. Thus, detailed investigations of drug activities in gliomas are needed. To investigate BBB penetration, pharmacodynamics, and tumor retention kinetics of an agonistic DR5 antibody in a brain tumor xenograft model, we utilized a noninvasive imaging method for longitudinal monitoring of apoptosis induction. Brain tumors were induced by intracranial (i.c.) implantation of a luciferase-expressing tumor cell line as a reporter. To quantify accumulation of anti-DR5 in brain tumors, we generated a dosage-response curve for apoptosis induction after i.c. delivery of fluorescence-labeled anti-DR5 at different dosages. Assuming 100% drug delivery after i.c. application, the amount of accumulated antibody after i.v. application was calculated relative to its apoptosis induction. We found that up to 0.20% to 0.97% of antibody delivered i.v. reached the brain tumor, but that apoptosis induction declined quickly within 24 hours. These results were confirmed by three-dimensional fluorescence microscopy of antibody accumulation in explanted brains. Nonetheless, significant antitumor efficacy was documented after anti-DR5 delivery. We further demonstrated that antibody penetration was facilitated by an impaired BBB in brain tumors. These imaging methods enable the quantification of antibody accumulation and pharmacodynamics in brain tumors, offering a holistic approach for assessment of central nervous system-targeting drugs.