@misc{kelada2019noninvasive,

title = {Noninvasive imaging of tumor hypoxia during radiation-induced tumor vascular disruption},

author = {Olivia J Kelada and Sijumon Kunjachan and Needa A Virani and Alexandre Detappe and Jennifer Hayashi and Thomas Ireland and Douglas E Biancur and Rajiv Kumar and Srinivas Sridhar and Mike Makrigiorgos and others},

year  = {2019},

date = {2019-01-01},

publisher = {American Association for Cancer Research},

abstract = {Purpose Tumor vascular targeted gold nanoparticles induce tumor vascular disruption when combined with external beam radiation therapy. Although effective in suppressing tumor growth and improving progression-free survival, tumor hypoxia may be a potential challenge in this anti-vascular therapy. Here, we investigate, the dynamic changes in tumor hypoxia pre- and post-radiation therapy using a gold nanoparticle-based tumor vascular disrupting agent.



Materials and methods 4-6 weeks old female nude-FOXn1 mice were subcutaneously inoculated with human A549 cells (~3×106) into the left flank. Functionalized gold nanoparticles (AuNP) were used to target the tumor blood vessels and tumor vascular disruption was induced via radiation. 10 Gy radiation treatment was delivered using a clinical radiation beam (6 MV) and HypoxiSense680 based in vivo fluorescence imaging was performed to visualize changes in tumor hypoxia at 24 h, 48 h and an extended period of 10 days. Tumor hypoxia was confirmed via immunohistochemistry. Mice were divided into four treatment groups: control, AuNP only, IR only, and AuNP+IR. Following treatment, tumor progression and overall survival was measured. Further analysis of nanoparticle biodistribution and toxicity were accessed using TEM Imaging, IC-PMS, and immunohistochemistry.



Results Longitudinal changes in tumor hypoxia were observed in all radiation-based treatment conditions. Combining gold nanoparticle and radiation resulted in an increase in tumor hypoxia at 48 h (p < 0.05) and a return to baseline in 10 days. In contrast, the ‘radiation only’ group showed an increase in tumor hypoxia by a factor of 0.5 at 48 h post-IR compared to baseline while 10 days later the tumor hypoxia remained stable. Quantitative variation in the hypoxia blood factor, CA9 increased 24 h post IR in the AuNP+IR, followed by a decrease in hypoxic by day 10 in accordance with in vivo imaging data. No change was observed with the IR only group. These findings were confirmed with representative pimonidazole staining that showed an increase in tumor hypoxia a few hours after AuNP+IR treatment. The mean relative reduction in tumor size post-treatment was a factor of 5.2 (p < 0.05) in the AuNP+IR group compared to the control and 3.5 compared to the IR only group, nearly 80 days post-treatment. Overall survival showed an average gain of up to 24 days in the AuNP+IR group compared to all other treatments. Almost 100 days post-treatment, 50% survival was observed in the AuNP+IR group compared to 20% in the IR-only groups (p < 0.05).



Conclusions Noninvasive imaging showed that AuNP+IR results in a transient increase and subsequent decline in mean tumor hypoxia, leading to substantial tumor regression and an overall increase in tumor survival. High radiation-induced vascular damage may lead to better tumor reduction and prolonged survival in the human non-small cell lung cancer model.



Citation Format: Olivia J. Kelada, Sijumon Kunjachan, Needa A. Virani, Alexandre Detappe, Jennifer Hayashi, Thomas Ireland, Douglas E. Biancur, Rajiv Kumar, Srinivas Sridhar, Mike Makrigiorgos, Ross I. Berbeco. Noninvasive imaging of tumor hypoxia during radiation-induced tumor vascular disruption [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 85.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{baldwin2019combination,

title = {Combination nanotherapy using the PARP inhibitor talazoparib and cyclin dependent kinase inhibitor dinaciclib},

author = {Paige Baldwin and Adrienne Orriols and Srinivas Sridhar},

year  = {2019},

date = {2019-01-01},

publisher = {American Association for Cancer Research},

abstract = {Introduction: PARP inhibitors exploit defects in DNA repair pathways to selectively target cancerous cells. As such, Talazoparib (TLZ), a potent PARP inhibitor, offers a way to target the biology of a number of cancers with DNA repair defects until these tumors develop resistance. PARP inhibitors must be used in combination with other inhibitors or chemotherapeutics to reverse resistance and sensitize non-responsive tumors. Dinaciclib, a potent cyclin dependent kinase (CDK) inhibitor, has been shown to sensitize both BRCA wild-type tumors and PARP inhibitor resistant tumors to PARP inhibition through disruption of homologous recombination. In clinical trials, Talazoparib and Dinaciclib have both demonstrated hematologic toxicities, suggesting a combination of these drugs would result in compounded toxicity, leading to dose reduction and an ineffective combination. Nanoparticle delivery systems offer a means to modify the toxicity profiles of these drugs and enhance the therapeutic window, therefore allowing for effective combination treatment.



Methods: Separate nanoformulations of Talazoparib (NanoTLZ) and Dinaciclib (NanoDCB) were optimized, and pharmacokinetics and pharmacodynamics assessed. Nanoformulations were tested alone and in combination in vitro to ensure NanoDCB could sensitize a model with no known DNA repair defects to NanoTLZ. The combination of the two nanoformulations was then assessed for efficacy and toxicity in orthotopic MDA-MB-231 xenografts.



Results: Robust formulations of NanoTLZ and NanoDCB were developed. Each nanoformulation extended the half-life of the drug it encapsulates. A constant low dose of Dinaciclib sensitized MDA-MB-231 cells to Talazoparib, significantly lowering the IC50 value. As a single agent NanoDCB was more effective in vitro than free Dinaciclib. In vivo, the combination of the two nanoformulations was more effective than either single nanoformulation or the combination of the two free drugs. Assessments of hematologic toxicities are underway, but thus far, there were no signs of gross toxicity in the combination therapy group.



Conclusions: The combination of NanoDCB and NanoTLZ has provided an effective method for sensitizing tumors to PARP inhibition that are otherwise nonresponsive to this therapy. The development of two separate nanoformulations has allowed for tailored dosing. These long-circulating nanoformulations have proven more effective than the free drugs in stabilizing tumor growth and were well tolerated. This work was supported by ARMY/W81XWH-16-1-0731.



Citation Format: Paige Baldwin, Adrienne Orriols, Srinivas Sridhar. Combination nanotherapy using the PARP inhibitor talazoparib and cyclin dependent kinase inhibitor dinaciclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3642.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{singh2019development,

title = {Development of targeted nanoformulation of talazoparib for combined chemoradiation therapy in lung cancer},

author = {Bijay Singh and Mostafa Abdelhalim and Stephanee Warrington and Srinivas Sridhar},

year  = {2019},

date = {2019-01-01},

publisher = {American Association for Cancer Research},

abstract = {Poly (ADP-ribose) polymerase (PARP) inhibitor (PARPi) therapy exploits a synthetic lethality strategy in cancers with inherent damage in DNA repair or transcription pathways. Talazoparib is a potent PARPi that is currently indicated for oral inhibitor therapy in several cancer clinical trials. Oral administration of these inhibitors typically results in poor bioavailability and tumor accumulation. In contrast, nanoparticle formulation provides a safe vehicle for parenteral administration of therapeutic drugs with sustainable release reducing systemic toxicity and also protect from surveillance of immune cells, thereby increasing the bioavailability of the drugs in vivo. Moreover, targeting strategy for the nanoparticles will improve the accumulation of drugs in the tumors. Here, we developed a targeted formulation of Talazoparib (NanoTLZ) which was decorated with anti-EGFR antibody as a ligand to ameliorate the cellular uptake of NanoTLZ via EGFR-mediated endocytosis. In vitro tests showed that NanoTLZ is more effective in cell growth inhibition than free Talazoparib. When combined with radiation with different doses from 2-10Gy, NanoTLZ showed a strong radiosensitization effect as evidenced with almost no colonies formation at 6 Gy of radiation dose. The high therapeutic efficacy of combined chemoradiation therapy in Calu 6 cell line can be attributed to the higher accumulation of NanoTLZ in the cancer cells as compared to the free Talazoparib which is also marred with efflux of the drug from the cells. The slow and sustained release of Talazoparib from nanoparticle formulation inside the cells lead enhanced inhibition of DNA repair pathways. These studies provide very encouraging results to evaluate the efficacy of these nanoparticles in lung cancer animal models.



Citation Format: Bijay Singh, Mostafa Abdelhalim, Stephanee Warrington, Srinivas Sridhar. Development of targeted nanoformulation of talazoparib for combined chemoradiation therapy in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3631.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{baldwin2019abstract,

title = {Abstract NT-087: NANOFORMULATION OF TALAZOPARIB SUPPRESSES TUMOR GROWTH AND ASCITES IN A DISSEMINATED CANCER MODEL},

author = {Paige Baldwin and Anders Ohman and Jamie Medina and Daniela Dinulescu and Srinivas Sridhar},

year  = {2019},

date = {2019-01-01},

publisher = {American Association for Cancer Research},

abstract = {Talazoparib, a potent PARP inhibitor (PARPi), induces synthetic lethality in BRCA-deficient cancers making it an attractive candidate for ovarian cancer treatment. However, its potency lends itself to side effects associated more closely with traditional chemotherapeutics than other clinically approved PARPi's. We sought to formulate Talazoparib in a nanoparticle delivery system such that the drug could be administered intraperitoneally, localizing the entire dose at the disease site, to increase therapeutic efficacy and minimize toxicity. NanoTalazoparib was formulated and characterized and found to have a mean diameter of 70 nm and a neutral surface charge. Talazoparib and NanoTalazoparib were tested on a panel of murine tubal and human HGSOC cell lines and dose response compared to the first clinically approved PARPi, Olaparib. Dose response data indicated all cell lines were more sensitive to Talazoparib and NanoTalazoparib than Olaparib and all lines showed the same sensitivity to nanoformulations as free drugs. The human cell lines had various BRCA mutations and deletions, as well as a homologous recombination proficient (HRP) line, however, the HRP line was more sensitive to treatment than some HRD lines. Therapeutic efficacy was tested in vivo in a murine cancer model that mimics disseminated peritoneal disease. NanoTalazoparib 3X weekly for 8 weeks did not shrink tumors but resulted in tumor growth inhibition of 64% while an equivalent dose of oral Talazoparib only resulted in 34% growth inhibition. NanoTalazoparib suppressed the average volume of ascites at the study endpoint by 3.45 times more than oral Talazoparib. H&E staining of the tissues indicated no significant toxicity to the organs of the mononuclear phagocyte system. These results indicate that NanoTalazoparib can be used to localize PARPi therapy to the peritoneal cavity for disseminated late stage ovarian cancer treatment. Our data suggests that NanoTalazoparib could be utilized to delay the formation of tumor ascites for women with HR-deficient disease. While NanoTalazoparib did not effectively treat the disseminated disease at this dose, it may have clinical utility, either in combination with other therapies or as a maintenance therapy. Preclinical data indicates PARP inhibitors potentiate damage when combined with other cytotoxic treatments, however, in the clinic this has resulted in enhanced toxicity, forcing dose reduction and delay. The IP administration of NanoTalazoparib may provide a route to bypass some of the toxicities that have plagued combination treatments.



Supported in part by Rivkin Foundation and CDMRP Ovarian Cancer Research Program



Citation Format: Paige Baldwin, Anders Ohman, Jamie Medina, Daniela Dinulescu, Srinivas Sridhar. NANOFORMULATION OF TALAZOPARIB SUPPRESSES TUMOR GROWTH AND ASCITES IN A DISSEMINATED CANCER MODEL [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr NT-087.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{singh2019abstract,

title = {Abstract A104: Nanoformulations of PARP and CDK inhibitors for cancer therapy},

author = {Bijay Singh and Shicheng Yang and Paige Baldwin and Anne van de Ven and Srinivas Sridhar},

year  = {2019},

date = {2019-01-01},

publisher = {American Association for Cancer Research},

abstract = {Poly(ADP-ribose) polymerase (PARP) inhibitors have been majorly utilized in cancers with BRCA1/2 mutations that have deficiencies in the homologous recombination (HR) DNA repair pathway. Traditionally, PARP inhibitors have been administered through oral route in the clinic but they have resulted in poor bioavailability, low tumor accumulation and high systemic toxicity. Moreover, tumors develop resistance to PARP inhibitors necessitating the development of strategies to re-sensitize these resistant tumors. To overcome these limitations, nanoparticle drug formulation has demonstrated a great potential to increase the drug concentration and accumulation at tumor sites with low systemic toxicities. Here we report the development of several nanoformulations of PARP inhibitors and observe their efficacies by systemic administration to treat various cancer diseases. We used two FDA approved PARP inhibitors (Olaparib or Talazoparib) for nanoformulations of NanoOlaparib and NanoTalazoparib, decorated with EpCAM or EGFR antibody, and tested on breast, ovarian, prostate and lung cancer with or without irradiation. In HR deficient models, the nanoformulations showed significant inhibition of tumor cell growth in vitro and in vivo. Above all, combination of PARP inhibitor with irradiation resulted in greater efficacy in lung and prostate cancer models. To overcome PARP inhibitor resistance, we formulated nanoparticles, NanoDinaciclib of cyclin-dependent kinase 12 (CDK12) inhibitor (dinaciclib) and used in combination with nanoformulation of PARP inhibitor to arrest the tumor growth in animal model. Our current research reveals that the use of CDK12 inhibitor in PARP resistant tumors further arrests tumor growth compared with monotherapy alone. Further studies will help clarify to achieve clear understanding of the mechanism of action CDK12 inhibitor to determine the best way to use PARP inhibitors beyond HR deficiency.



Citation Format: Bijay Singh, Shicheng Yang, Paige Baldwin, Anne van de Ven, Srinivas Sridhar. Nanoformulations of PARP and CDK inhibitors for cancer therapy [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A104. doi:10.1158/1535-7163.TARG-19-A104



©2019 American Association for Cancer Research.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{vazquez2018nanoparticle,

title = {Nanoparticle-mediated concomitant radiation dose amplification and PARP inhibition in lung cancer},

author = {Ana G Vazquez-Pagan and Paige Baldwin and Ravina M Ashtaputre and Sijumon Kunjachan and Srinivas Sridhar and Rajiv Kumar and Ross Berbeco},

year  = {2018},

date = {2018-01-01},

publisher = {American Association for Cancer Research},

abstract = {Introduction: More than 50% of cancer patients receive radiation therapy at some point during their care. Gold nanoparticles (GNPs) can amplify the radiation dose by facilitating the ejection of low-energy photoelectrons, resulting in increased DNA damage. One of the main challenges of radiation therapy in cancer is to sustain this damage for longer durations. DNA single-strand breaks (SSBs) are repaired by base excision repair, which utilizes Poly(ADP-ribose) polymerase (PARP). PARP inhibition during radiotherapy provides an attractive alternative in maximizing treatment outcomes. Here, we explore a strategy to combine the radiosensitizing effect of GNPs with the DNA-repair inhibiting ability of NanoTalazoparib (nTLZ), a liposomal formulation of the PARP inhibitor, talazoparib (TLZ).



Methods: GNPs were synthesized by reducing AuCl4 using Tetrakis(hydroxymethyl)phosphonium chloride and further PEGylating using heterobifunctional PEGs. A liposomal formulation of TLZ was synthesized using the Nanoassemblr, a microfluidics-based device. Physicochemical characterization of GNPs and nTLZ was carried out using TEM, DLS and release kinetics studies. In vitro studies were carried out to assess the toxicity of the GNPs using MTT assay in non-small cell lung cancer (NSCLC) cell line Calu-6. The therapeutic efficacy of combination treatment using GNPs, nTLZ and radiation was done using clonogenic survival assays. Clonogenic assay was carried out using Calu 6 cells, which were sequentially treated with GNPs (1mg/mL), TLZ (0.5 uM) and nTLZ (0.5 uM) with and without radiation. The radiation doses varied from 0-10Gy for each set of treatments.



Results: PEGylated GNP's showed a hydrodynamic diameter of ~10-12 nm with a spherical morphology whereas nTLZ size was 70 nm encapsulating TLZ at a concentration of ~200 ug/ml. MTT assay showed no toxicity for PEGylated GNPs treated upto a concentration of 3.0 mg/mL. Cells treated with either GNPs, TLZ or nTLZ did not show significant reduction in colony formation, but were reduced with increasing doses of radiation. The survival plots showed a highly additive antiproliferative effect for the GNP + nTLZ combination at all radiation doses, while the free TLZ + GNPs combination was not as effective at inhibiting colony formation. In vivo experiments assessing the combination therapy in a subcutaneous xenograft mice model using Calu 6 are currently under way.



Conclusions: The preliminary in vitro results indicate that the combination of radiosensitizing GNPs with a potent DNA repair enzyme inhibitor, TLZ, has an immense potential as a complimentary combination therapy in conjunction with radiation therapy in treatment of lung cancer.



This work is supported by the CaNCURE program (grant #1CA174650-02), American Lung Association, Dana-Farber Cancer Institute and Brigham and Women's Hospital.



Citation Format: Ana G. Vazquez-Pagan, Paige Baldwin, Ravina M. Ashtaputre, Sijumon Kunjachan, Srinivas Sridhar, Rajiv Kumar, Ross Berbeco. Nanoparticle-mediated concomitant radiation dose amplification and PARP inhibition in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3710.



©2018 American Association for Cancer Research.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{baldwin2018targeted,

title = {Targeted nanotherapy using the PARP inhibitor talazoparib for breast cancer treatment},

author = {Paige Baldwin and Rajiv Kumar and Srinivas Sridhar},

year  = {2018},

date = {2018-01-01},

publisher = {American Association for Cancer Research},

abstract = {Introduction: PARP inhibitors exploit defects in DNA repair pathways to selectively target cancerous cells. These drugs are currently delivered orally, but Talazoparib, the most potent PARP inhibitor, exhibits greater toxicity than the others. Systemic administration of nanoparticles bypasses the first-pass metabolism of oral drugs and nanoparticles preferentially accumulate in tumors due to the leaky tumor vasculature. Additionally, nanoparticles can be actively targeted to tumors by conjugating different moieties such as antibodies that recognize overexpressed markers on the tumor cells. NanoTalazoparib (NanoTLZ) has been previously formulated and extensively characterized in breast, ovarian, and lung cancer models. Here we describe further characterization of NanoTLZ and the development of a next generation fluorescently labeled EPCAM targeted formulation of NanoTLZ for the treatment of triple negative breast cancer (TNBC).



Methods: Animals with orthotopic TNBC xenografts were injected with NanoTLZ and at various time points tumor biopsies were taken to assay tumor PAR levels. Blood was collected at various time points and plasma separated for drug extraction and quantification. Pharmacokinetic modeling is underway. Fluorescently labeled NanoTLZ was developed with the addition of Cy5, followed by further improvement via conjugation of anti-EPCAM antibodies. Targeting capability was assessed via laser scanning confocal microscopy after treatment of the TNBC cell line MDA-MB-231 with either non-targeted or targeted NanoTLZ. Therapeutic efficacy studies with targeted NanoTLZ alone and in combination with radiation are underway in an MDA-MB-231 xenograft model.



Results: Pharmacodynamics indicated PAR suppression in tumors within 30 minutes of NanoTLZ treatment. Tumor PAR levels began to increase 24 hours after a single dose but remained significantly lower than control levels up to 72 hours (P<0.005). Characterization of NanoTLZ after the addition of Cy5 and after anti-EPCAM targeting indicated that the formulation remained under 100 nm in diameter with a charge of ~10 mV and equivalent drug loading and release. Cy 5 labeling allowed for visualization of nanoparticle uptake and intracellular fluorescence was 70% greater in cells when treated with EPCAM targeted NanoTLZ compared to non-targeted.



Conclusions: The sustained release of Talazoparib from the nanoformulation decreases tumor PAR levels for up to 72 hours after a single dose, allowing for less frequent administration than the current daily regime used for oral Talazoparib. The targeted formulation of NanoTLZ shares the same physicochemical properties as the untargeted formulation, but is taken up much faster in vitro, suggesting it will allow for greater accumulation at the tumor site making it more effective than the previously tested untargeted NanoTLZ. Supported by ARMY/W81XWH-16-1-0731 and Rivkin Foundation.



Citation Format: Paige Baldwin, Rajiv Kumar, Srinivas Sridhar. Targeted nanotherapy using the PARP inhibitor talazoparib for breast cancer treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3715.



©2018 American Association for Cancer Research.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{wilfred2018biomaterials,

title = {Biomaterials for combined radiotherapy and immunotherapy of cancer},

author = {NGWA Wilfred and Rajiv Kumar and Gerassimos Makrigiorgos and Srinivas Sridhar and Stephanie Dougan},

year  = {2018},

date = {2018-00-01},

abstract = {Compositions and methods for the radiological and immunotherapeutic treatment of cancer are provided. Metallic nanoparticles conjugated with an immunoadjuvant are dispersed within a biodegradable polymer matrix that can be implanted in a patient and released gradually. The implant may be configured as, or be a component of, brachytherapy spacers and applicators, or radiotherapy fiducial markers. The composition may be combined with marginless radiotherapy, allowing for lower doses of radiation and enhancing the immune response against cancer, including at non-irradiated sites.},

note = {US Patent App. 15/752,099},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{paro2017abstract,

title = {Abstract B44: Biological mechanisms involved in nanoparticle-enhanced radiation therapy for pancreatic cancer},

author = {Autumn D Paro and Ilan Shanmugam and Anne van de Ven and Rajiv Kumar and Thomas J Webster and Srinivas Sridhar},

year  = {2017},

date = {2017-01-01},

publisher = {American Association for Cancer Research},

abstract = {Introduction: The objective of this project is to study the biological pathways activated in irradiated pancreatic cancer cells pre-treated with gold nanoparticles. Metallic nanoparticles emit Auger electrons and photoelectrons upon exposure to X-rays. When selectively delivered to tumors, these nanoparticles can locally enhance the effects of radiation therapy. Previous in vitro work has primarily studied the effectiveness of nanoparticle-enhanced therapy, without elucidating the underlying biological mechanisms. Understanding the biological mechanisms (such as changes in gene expression) of how nanoparticles enhance radiation therapy can help in the further design of more effective nanoparticles.



Methods: Gold nanoparticle sensitization was tested using a human based pancreatic cancer cell line, Capan-1. Nanoparticle toxicity was tested using a combination of MTS and Alamar Blue assays after 24 hours of treatment. Gene expression was tested using immunofluorescence and western blot techniques. Cells were pretreated with 0.8 mg gold nanoparticles 24 hours prior to radiation. Cells were then harvested at various time points to determine how gene expression changes over time. Radiosensitization was carried out using a clonogic cell survival assay where cells were pretreated with 0.8 mg gold nanoparticles 24 hours prior to radiation and then re-plated at various densities 4 hours post radiation, and allowed to incubate for 14 days. Statistical differences were determined using ANOVA followed by student t-tests.



Results: The MTS and Alamar blue assays showed low gold nanoparticle toxicity towards cells up to a dose of 1mg for Capan-1 cells. Capan-1 cells pretreated with 0.8 mg gold nanoparticles for 24 hours prior to radiation showed lower cell survival than cells only treated with radiation. Western blots and immunofluorescence data showed that certain genes, such as γ-H2AX, were upregulated when pretreated with gold nanoparticles and irradiated compared to cells treated with radiation alone. It was also shown that γ-H2AX expression peaked around 30 minutes post radiation and then returned to basal levels after 24 hours.



Conclusions: Capan-1 cells experience more DNA damage when pretreated with gold nanoparticles than when only treated with radiation. γ-H2AX, which is a DNA damage-related protein, was upregulated in the combined dose showing that there was more DNA damage in the combined treatment. It was also shown that protein and gene expression analysis needs to be carried out at various time points post radiation to obtain a better understanding of the mechanisms involved in radiation induced damage to pancreatic cancer cells.



Supported by NSF-DGE- 0965843 and CA188833-02.



Citation Format: Autumn D. Paro, Ilan Shanmugam, Anne van de Ven, Rajiv Kumar, Thomas J. Webster, Srinivas Sridhar. Biological mechanisms involved in nanoparticle-enhanced radiation therapy for pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr B44.



©2016 American Association for Cancer Research.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{baldwin2017abstract,

title = {Abstract B29: Nanoformulations and sustained delivery systems for the PARP inhibitors Olaparib and Talazoparib},

author = {Paige Baldwin and Anders Ohman and Jodi Belz and Jeremy Thong and Noelle Castilla Ojo and Karen Liby and Daniela Dinulescu and Srinivas Sridhar},

year  = {2017},

date = {2017-01-01},

publisher = {American Association for Cancer Research},

abstract = {Introduction: Poly(ADP-ribose) Polymerase (PARP) plays an important role in a number of DNA repair pathways. PARP inhibitors (PARPi) such as Olaparib and Talazoparib exploit the concept of synthetic lethality by selectively targeting cancer cells with defective DNA repair pathways. These drugs are currently only available in oral form which results in limited bioavailability, poor tumor accumulation, and systemic toxicity, specifically when combined with other DNA damaging agents. Here we report the development of two different delivery techniques including nanoformulations of Olaparib and Talazoparib and a biodegradable implant for localized delivery of Talazoparib. The nanoformulations allow for intravenous or intraperitoneal delivery, providing greater bioavailability and tumor accumulation, while limiting systemic toxicities and the implant provides a sustained release for intratumoral delivery to enhance the dose at the tumor site thereby limiting systemic toxicity.



Methods: Nanoparticle formulations of Olaparib and Talazoparib were synthesized and characterized via TEM, DLS, and HPLC to elucidate size, loading, and release before testing in vivo. In vitro experiments for testing nanoformulations include dose response with a panel of ovarian cancer cell lines. In vivo, NanoOlaparib was tested in an IP spread model using 404 cells derived from BRCA2-/-, TP53-/-, PTEN-/- genetically engineered mouse models. Animals were treated IP with NanoOlaparib alone, and in combination with cisplatin. The 1-2 mm long Talazoparib implant was characterized with SEM and HPLC for structure, loading, and release. A spontaneous tumor forming breast cancer model was used to test the Talazoparib implant. Implants were directly injected into the tumor of Brca1Co/Co;MMTV-Cre;p53+/- mice for a one time treatment.



Results: PA1 demonstrated high sensitivity to NanoOlaparib which may be attributed to genetic instability at 11/13 polymorphic loci. Both PTEN and BRCA deficiencies resulted in comparable IC50's likely due to synthetic lethality attributed to dysfunctional homologous recombination pathways. NanoTalazoparib is more potent than NanoOlaparib, resulting in a similar relationship in cell line sensitivity with overall lower IC50's. Bioluminescence images illustrated that NanoOlaparib administered IP daily in the ovarian cancer model resulted in a greater inhibition of tumor growth than those treated with oral Olaparib daily. The Talazoparib implant released therapeutically relevant doses of Talazoparib over multiple weeks. In vivo the implant reduced tumors 50% following the one time treatment, while untreated tumors increased significantly in size.



Conclusions: Robust nanoparticle formulations of NanoTalazoparib and NanoOlaparib have been successfully developed and characterized. These results show that NanoOlaparib and NanoTalazoparib amplify the efficacy of PARP inhibitors in vivo. The Talazoparib implant provides a safe strategy for sustained local delivery of Talazoparib directly to the tumor. These strategies provide opportunities to increase the efficacy of PARP inhibitors via tailored delivery to the type of tumor.



This work was supported by the DOD Ovarian Cancer Research Program under Army- W81XWH-14-1-0092 and IGERT grant NSF-DGE- 0965843.



Citation Format: Paige Baldwin, Anders Ohman, Jodi Belz, Jeremy Thong, Noelle Castilla Ojo, Karen Liby, Daniela Dinulescu, Srinivas Sridhar. Nanoformulations and sustained delivery systems for the PARP inhibitors Olaparib and Talazoparib. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr B29.



©2016 American Association for Cancer Research.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{van2017abstract,

title = {Abstract B48: Prostate cancer pre-treatment with nanoformulated Olaparib overcomes radiation resistance},

author = {Anne L van de Ven and Shifalika Tangutoori and Paige Baldwin and Ju Qiao and Codi Gharagouzloo and Nina Seitzer and John Clohessy and Houari Korideck and Mike G Makrigiorgos and Robert Cormack and others},

year  = {2017},

date = {2017-01-01},

publisher = {American Association for Cancer Research},

abstract = {Prostate cancers with PTEN deletions are promising candidates for DNA repair inhibitors such as olaparib and talazoparib. Here we show that radiation-resistant cells and tumors derived from Ptenpc-/-;Trp53pc-/- mice are rendered radiation-sensitive following pre-treatment with liposomal nanoOlaparib. This enhancement in radiosensitivity is accompanied by radiation dose-dependent changes in γ-H2AX expression and is specific to nanoformulated Olaparib alone. In animals, twice-weekly intravenous administration of nanoOlaparib alone results in significant tumor growth inhibition. When nanoOlaparib is administered prior to radiation, we find that a single dose of radiation is sufficient to increase mouse survival time by as much as 10 weeks (study duration = 13 weeks). Using ferumoxytol as a surrogate nanoparticle, magnetic resonance imaging (MRI) studies revealed that nanoOlaparib administration enhances the ability of nanoparticles to accumulate in tumors. Compared to untreated and radiation-only controls, nanoOlaparib-treated tumors showed 18-fold higher nanoparticle accumulation, suggesting that the in vivo efficacy of nanoOlaparib may be potentiated by its ability to enhance its own accumulation in tumors.



Citation Format: Anne L. van de Ven, Shifalika Tangutoori, Paige Baldwin, Ju Qiao, Codi Gharagouzloo, Nina Seitzer, John Clohessy, Houari Korideck, G. Mike Makrigiorgos, Robert Cormack, Pier Paolo Pandolfi, Srinivas Sridhar. Prostate cancer pre-treatment with nanoformulated Olaparib overcomes radiation resistance. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr B48.



©2016 American Association for Cancer Research.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{kumar2017abstract,

title = {Abstract B41: Gold nanoparticles based platforms for localized radiosensitization in cancer radiation therapy},

author = {Rajiv Kumar and Wilfred Ngwa and Vinit Joshi and Sijumon Kunjachan and Ross Berbeco and Mike Makrigiorgos and Srinivas Sridhar},

year  = {2017},

date = {2017-01-01},

publisher = {American Association for Cancer Research},

abstract = {The use of nanoparticles with high atomic (Z) number have been known to attenuate X-rays and the unique properties associated with gold nanoparticles makes them as potent radiosensitizers for enhancing Radiotherapy (RT) treatments. The interaction of high Z materials with the X-rays results in photoelectric absorption which leads to generation of photoelectrons. These low energy photoelectrons can deliver lethal energy in the close proximity. The success of cancer radiation therapy relies heavily on the effective delivery of radiation dose to the tumor site sparing the surrounding normal tissues. To overcome the limitations associated with increasing the radiation dose, due to normal tissue toxicities, the feasibility of radiosensitizing the tumor using gold nanoparticles provide a promising alternative. Targeting gold nanoparticles based formulations to the tumor prior to radiation therapy will result in radiation dose enhancement, by generating secondary photoelectrons, locally inside the tumor and thereby minimizing the dose dependent toxicity to non-specific neighboring tissues. Here, we have developed different Gold nanoparticles based formulations to locally radiosensitize the tumor cells in three different cancer models.



For targeting pancreatic cancers, we have fabricated a new generation of GNPs formulation which are 3-4 nm in diameter and surface passivated with hetero-bifunctional PEG, fluorophore AlexaFlour 647 and peptide RGD. This formulation showed a 2.8-fold in vitro cell kill enhancement with X-rays, as demonstrated by clonogenic survival assays. In vivo studies confirmed the highly specific tumor uptake in tumor endothelial cells in orthotopic pancreatic tumor mice model. The combined treatment in animals treated with GNPs and radiation (10Gy) showed the maximum endothelial cells damage, as confirmed with confocal imaging of the tumor sections and CD31 immunostaining.



For targeting the lung cancer, we have used the same GNPs formulation but adopted a inhalation/instillation (INH) route for administering the nanoparticles in vivo in transgenic lung cancer mice model as opposed to customary intravenous (i.v) route. Fluorescence imaging and ex-vivo electron microcopy results showed a 4.7 times higher concentration of GNPs in the lung tumors of mice when using INH delivery compared to i.v. approach. The survival studies with these animals are currently underway.



For using these radiosensitizing nanoparticles in brachytherapy applications, we have incorporated GNPs in modified brachytherapy spacers to enhance radiation dose locally in tumor without any additional surgical intervention. These spacers are normally placed inside the tumor to spatially distribute the radioactive seeds. The incorporation of GNPs in these spacers allowed for enhancing the radiation dose by the GNPs released from the spacers. These spacers have same morphology (5 mm in length and 0.8 mm in diameter) as commercial spacers with additional radiosensitizing properties because of doped GNPs. We have shown the time dependent release of the GNPs as a function of size of GNPs from the spacers into the tumor by optical imaging. We have further incorporated the GNPs based brachytherapy spacer with the immunoadjuvants, anti-CD40 to combine the radiation and immunotherapy in a single platform. The preliminary results indicate that gold nanoparticles based nanoplatform shows promise as a potential theranostic radiosensitizer which allows for combining multiple therapies in a single platform.



This work is supported by ARMY/ W81XWH-12-1-0154, NSF DGE 0965843, HHS/5U54CA151881-02, NCI R03CA164645, NCI1 K01CA17247801, the Electronics Materials Research Institute at Northeastern University, and Brigham and Women's Hospital.



Citation Format: Rajiv Kumar, Wilfred Ngwa, Vinit Joshi, Sijumon Kunjachan, Ross Berbeco, Mike Makrigiorgos, Srinivas Sridhar. Gold nanoparticles based platforms for localized radiosensitization in cancer radiation therapy. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr B41.



©2016 American Association for Cancer Research.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{belz2017abstract,

title = {Abstract B30: Sustained release of PARP inhibitor Talazoparib and chemotherapeutic Docetaxel from modified brachytherapy spacers for treatment of breast and prostate cancer},

author = {Jodi Belz and Noelle Castilla Ojo and Paige Baldwin and Rajiv Kumar and Anne van de Ven and Karen Liby and Robert Cormack and Mike Makrigiorgos and Srinivas Sridhar},

year  = {2017},

date = {2017-01-01},

publisher = {American Association for Cancer Research},

abstract = {Sustained localized delivery of cancer therapeutics is a safe and effective unique option for local control of tumors. Here we report a novel biodegradable implant with the capability to encapsulate different therapeutics, molecular agents, or nanoparticles for local intratumoral delivery. We have successfully demonstrated in vivo the delivery of PARP inhibitor Talazoparib to treat Brca1-mutated cancers and Docetaxel to treat localized or recurring prostate cancers. This one-time intratumoral injection provides a safe vehicle for the sustained release of PARP inhibitor Talazoparib and chemotherapeutic Docetaxel in contrast to low bioavailability and toxicity associated with oral or systemic delivery.



Methods: Biodegradable implants of 1-2mm length and 0.8mm diameter were loaded with ~50μg Talazoparib for BRCA1-mutated breast cancer studies and ~500μg Docetaxel (DTX) for prostate cancer studies. The implants were characterized in vitro using SEM and HPLC, and the release kinetic studies were carried out in PBS buffer (pH 6.0) at 37°C. The IC50's were determined using an MTS assay in breast cancer cell lines derived from Brca1 Co/Co; MMTV-Cre; p53+/−mice, W0069 and W780, and human-derived prostate cancer, PC3. In vivo studies were carried out in Brca1 Co/Co; MMTV-Cre; p53+/− spontaneous tumored mice for breast cancer studies. Subcutaneous PC3 tumors were xenografted in nude mice. Prostate cancer studies were done with and without radiation. Drug-loaded implants were injected once intratumorally using an 18G brachytherapy needle.



Results: The release profile of the drug from the implant in buffer showed a highly sustained release for multiple weeks at therapeutically relevant doses for both docetaxel and Talazoparib loading implants. Breast cancer cell lines W0069 and W780 were highly sensitive to Talazoparib, most likely due to Brca1 mutation. Following a one-time intratumoral implantation of Talazoparib, tumors reduced in size by an average of 50%, while untreated tumors increased ~5X in size. Talazoparib dosing appeared to be well tolerated by the mice. Docetaxel implants proved to be an effective method for prostate cancer in vivo with no significant weight loss observed. The local docetaxel spacer group showed sustained tumor inhibition compared to empty implants and an equivalent DTX dose given systemically. At 40 days 89% survival was observed for mice treated with localized DTX implants compared with 0% in all other treatment groups. Histology samples were taken from sacrificed mice and immunohistochemistry are currently underway.



Conclusions: Sustained local release of therapeutically relevant doses of Talazoparib and Docetaxel were observed in vitro and in vivo. Therapeutics-loaded implants represent a novel delivery route that are well-tolerated. Sustained release of Talazoparib appears to amplify the therapeutic efficacy of PARP inhibition in BRCA1 mutated breast cancers and sustained release of Docetaxel is an effective chemotherapy option alone or in combination with radiation therapy. These results laid a strong foundation for the use of localized biodegradable implants for the treatment of breast and prostate cancer.



This work was supported by the Army- W81XWH-14-1-0092, Breast Cancer Research Foundation and Northeastern University–Dana Farber Cancer Institute collaborative grant.



Citation Format: Jodi Belz, Noelle Castilla Ojo, Paige Baldwin, Rajiv Kumar, Anne van de Ven, Karen Liby, Robert Cormack, Mike Makrigiorgos, Srinivas Sridhar4. Sustained release of PARP inhibitor Talazoparib and chemotherapeutic Docetaxel from modified brachytherapy spacers for treatment of breast and prostate cancer. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr B30.



©2016 American Association for Cancer Research.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{baldwin2017abstractb,

title = {Abstract NTOC-080: NANOOLAPARIB: AN INTRAPERITONEAL PARP INHIBITOR THERAPY FOR OVARIAN CANCER},

author = {Paige Baldwin and Anders Ohman and Daniela Dinulescu and Srinivas Sridhar},

year  = {2017},

date = {2017-01-01},

publisher = {American Association for Cancer Research},

abstract = {PURPOSE: PARP inhibitor therapy for ovarian cancer exploits the concept of synthetic lethality by taking advantage of defects in DNA damage repair pathways. Currently Olaparib is the only FDA-approved PARP inhibitor and is available as an oral dosage, which has plenty of advantages, but requires the drug to undergo first pass metabolism, inactivating a significant fraction of the dose. We have developed a nanoparticle delivery system to allow for local delivery of Olaparib directly to the intraperitoneal cavity.



METHODS: NanoOlaparib was characterized in vitro in regards to size, charge, drug loading and release before testing on a panel of ovarian cancer cell lines, including KURAMOCHI, SKOV3, OVSAHO, JHOS2, PA1, COV318, 403 and 404, derived from tumors of Brca2-/-, Pten-/-, Tp53-/- mice, and 4306 and 4412, developed from conditional KrasLSL-G12D/+, Pten-/- mice, to elucidate sensitivity profiles and ensure comparable activity to the free drug. 404 cells, derived from Brca2-/-, Tp53-/-, Pten-/- genetically engineered mouse models, were utilized to develop an IP spread xenograft model to test NanoOlaparib in vivo. Animals were treated with NanoOlaparib or oral Olaparib daily for 4 weeks. Tumor burden was monitored weekly via bioluminescence imaging.



RESULTS: NanoOlaparib shows comparable efficacy in vitro to free Olaparib. The murine cell lines were the most sensitive to the treatment regardless of BRCA status, suggesting that Pten deletions are just as susceptible to PARP inhibitor therapy as the BRCA mutations. The average fold change in bioluminescence for NanoOlaparib decreased, while it increased for oral Olaparib. The oral Olaparib animals had widely varied responses, with some animals' tumors shrinking and others never responding. All NanoOlaparib tumors shrank initially, however, severe toxicity was noted after 3 weeks of treatment.



CONCLUSIONS: NanoOlaparib toxicity in vivo was observed with daily dosing likely due to the sustained release of the drug in comparison to the much more rapid clearance of the oral drug. While the NanoOlaparib was toxic, it provided a much more uniform response to the treatment than the oral Olaparib. It is clear that because this strategy provides 100% of the dose to the disease site with a sustained delivery it is no longer necessary to administer daily. This suggests that NanoOlaparib changes the pharmacokinetics to allow for a lower dose to be administered. A modified dosing regime is to be tested with the goal of lowering the toxicity while still maintaining therapeutic efficacy.



Citation Format: Paige Baldwin, Anders Ohman, Daniela Dinulescu, Srinivas Sridhar. NANOOLAPARIB: AN INTRAPERITONEAL PARP INHIBITOR THERAPY FOR OVARIAN CANCER [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr NTOC-080.



©2017 American Association for Cancer Research.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{baldwin2017nanoformulated,

title = {Nanoformulated Talazoparib and Olaparib for enhanced delivery},

author = {Paige Baldwin and Rajiv Kumar and Edward Favours and Karen Liby and Raushan Kurmasheva and David Kozono and Srinivas Sridhar},

year  = {2017},

date = {2017-01-01},

publisher = {American Association for Cancer Research},

abstract = {Introduction: PARP inhibitors such as Talazoparib and Olaparib exploit deficiencies in DNA repair pathways, making them attractive candidates for treatment of a number of different cancers. These drugs are particularly effective when used in combination with other DNA damaging agents such as chemotherapeutics and radiation therapy. Combination trials, however, have resulted in severe toxicities, necessitating either dose reduction or delay. Dose reduction leads to suboptimal dosing and provides little therapeutic benefit compared to monotherapy. Systemically administered nanoparticles offer a more effective way to selectively accumulate drugs in tumors and bypass toxicities associated with oral delivery. We have developed nanoparticle delivery systems for both Olaparib and Talazoparib in order to improve tumor accumulation while bypassing the toxicity associated with oral administration.



Methods: Lipid nanoformulations of Olaparib and Talazoparib have been developed and characterized in regard to size, surface charge, drug loading, release, and stability. NanoTalazoparib has been tested in vitro in breast cancer cell lines including W0069, W780, and HCC1937 which exhibit BRCA1 and 2 mutations, and NanoOlaparib in the lung cancer cell line Calu-6 which also has a defective FA-BRCA pathway. Mice have been treated with NanoOlaparib and NanoTalazoparib alone and in combination with radiation or temozolomide in order to evaluate toxicity. Therapeutic efficacy studies are currently underway.



Results: The nanoformulations have been formulated to encapsulate a clinically relevant dose of either Talazoparib or Olaparib and release at 37°C over a period of days, while remaining stable during storage at 4°C. In vitro, both nanoformulations show the same activity as free drug with IC50s in the nanomolar range for these cell lines with varying deficiencies in the BRCA pathway. Mice have shown no appreciable weight loss during treatment with either nanoformulation alone or in combination with other treatment modalities.



Conclusion: Nanoformulations of Talazoparib and Olaparib have been developed and characterized to demonstrate activity in vitro and tolerable doses in vivo. We have found that mice tolerate NanoTalazoparib at higher doses when combined with Temozolomide than when given oral Talazoparib. The sustained release from the nanoparticles allows for the nanoformulation to be administered less often than the daily administration for oral drug and the improved tolerability opens the door for combination therapy with both chemotherapeutics and radiation therapy. Therapeutic efficacy studies are underway and we expect that as a monotherapy NanoTalazoparib will be more effective at lower doses than oral Talazoparib, based on the longer circulation time and more selective accumulation in tumors. We also anticipate that combination therapy will be more effective with the nanoformulation, as the maximum tolerated dose is higher than that of the oral drug.



Citation Format: Paige Baldwin, Rajiv Kumar, Edward Favours, Karen Liby, Raushan Kurmasheva, David Kozono, Srinivas Sridhar. Nanoformulated Talazoparib and Olaparib for enhanced delivery [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3100. doi:10.1158/1538-7445.AM2017-3100



©2017 American Association for Cancer Research.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}

@misc{baig2017nanoformulation,

title = {Nanoformulation of talazoparib to increase efficacy when combined with temozolomide for the treatment of Ewing sarcoma xenografts},

author = {Nabeela Baig and Rostislav Likhotvorik and Paige Baldwin and Srinivas Sridhar and Raushan Kurmasheva},

year  = {2017},

date = {2017-01-01},

publisher = {American Association for Cancer Research},

abstract = {Ewing Family of tumors (EFT) comprises the fourth most common highly malignant childhood cancer. Although sustained event-free survival (EFS) can be achieved with intensive chemo-radiation therapy for patients with local-regional disease, this therapy is relatively ineffective in the treatment of metastatic disease with EFS of 12% at 5 years. Ewing sarcoma is characterized by a reciprocal translocation between chromosomes 11 and 22 that encodes a chimeric oncoprotein resulting from the fusion of EWSR1 to the FLI1 transcription factor in ~85% of tumors. Therapy for patients with EFT comprises surgery, intensive use of cytotoxic agents and radiation therapy. Dose intensification and dose compression has resulted in some improvement in outcome, but patents with advanced or metastatic disease at diagnosis still represent a challenge. Further, patients alive at 5 years from diagnosis still have a high probability of subsequent relapse. Further, long-term consequences of treatment included cardiac dysfunction, and secondary malignancies. Thus, more effective and less toxic therapies are required to treat patients with advanced disease.



Our studies, as part of the Pediatric Preclinical Testing Program (PPTP), identified the combination of the PARP inhibitor, talazoparib, with the DNA damaging agent temozolomide, as being highly synergistic in xenograft models of Ewing sarcoma, but not against other tumor types. In this study 5 of 10 Ewing tumor xenografts models showed dramatic regressions to the combination, while administered as single agents neither talazoparib or temozolomide were active. We have studied the talazoparib-temozolomide synergy in vitro, and results indicate that in models where there is no synergy as xenografts, the cell lines have either intrinsic resistance to talazoparib, temozolomide or both drugs. In mice, and in the clinical trial (NCT02116777), the talazoparib-temozolomide combination is toxic requiring a reduction in temozolomide dose to ~15% of its single maximum-tolerated dose.



We are exploring the use of nanoparticle-formulated talazoparib (npTLZ) developed by Nanomaterials Synthesis Laboratory at Northeastern University without tumor targeting or with antibody-mediated targeting to increase the tumor-drug delivery, reduce normal tissue toxicity (mainly thrombocytopenia), and potentially allow escalation of temozolomide dose. In the PPTP study, the MTD for temozolomide combined with free talazoparib (0.25 mg/kg PO BID daily x 5) was 12 mg/kg. Our recent data showed no toxicity of temozolomide at 66 mg/kg (PO daily x 5) in mice treated with npTLZ (0.5 mg/kg IV daily x 5), suggesting that npTLZ does not potentiate TMZ toxicity to normal mouse tissues. We anticipate that nanoparticle delivery of talazoparib combined with temozolomide will allow reduced toxicity while increasing the response rate for this combination in preclinical models of Ewing sarcoma.



Citation Format: Nabeela Baig, Rostislav Likhotvorik, Paige Baldwin, Srinivas Sridhar, Raushan Kurmasheva. Nanoformulation of talazoparib to increase efficacy when combined with temozolomide for the treatment of Ewing sarcoma xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5054. doi:10.1158/1538-7445.AM2017-5054



©2017 American Association for Cancer Research.},

keywords = {Nanomedicine},

pubstate = {published},

tppubtype = {misc}

}