Straubinger, Robert M.

Objectives: Preclinical studies demonstrated antitumor activity of dovitinib in pancreatic cancer models. This phase Ib study aimed to determine the maximum tolerated dose (MTD) of dovitinib in combination with gemcitabine and capecitabine and to characterize the safety and pharmacokinetic profile in patients with advanced pancreatic and biliary tract cancers and solid malignancies. Materials and Methods: Patients received gemcitabine 1000 mg/m² intravenously on days 1 and 8, capecitabine 1300 mg/m² oral daily from day 1 to 14, and dovitinib oral daily 5 days on and 2 days off, every 21-day cycle. The standard 3+3 dose escalation design was utilized and the study expanded to treat an additional 20 advanced pancreatic and biliary tract cancers patients at MTD. Results: A total of 29 patients were enrolled. One patient experienced dose-limiting grade 3 colitis. Two patients developed clinically significant neuropathy after the first cycle requiring dose reduction. The MTD was not reached and dovitinib 300 mg was declared the recommended dose for expansion. The most frequent grade 2 or worse adverse events were fatigue (45%), neutropenia (41%), thrombocytopenia (34%), anemia (24%), nausea (24%), and palmer-plantar erythrodysaesthesia syndrome (21%). Partial responses were observed in 5 patients. Pharmacokinetic studies showed no drug-drug interaction between dovitinib, capecitabine and gemcitabine. Fibroblast growth factor 23 plasma level increased in 4 of 5 patients during the first cycle of treatment. Conclusions: Dovitinib 300 mg daily is the recommended dose when combined with gemcitabine and capecitabine, achieving clinically relevant plasma concentrations. The study combination demonstrated encouraging efficacy signals in advanced pancreatic cancer.

Abstract Background: Pancreatic cancer (PaCA) is a deadly disease with 5-year survival of 6%. Poor prognosis is attributed to low tumor microvessel density, poor perfusion, and amplified stroma, constituting a drug delivery barrier. Tumor priming using NVP-LDE225, an inhibitor of sonic hedgehog (sHH) signaling, can compromise the stromal drug delivery barrier by mediating stromal thinning, and discharge of tumor interstitial pressure (IFP) and decompression of tumor vasculature, resulting in increased perfusion and deposition of drug-containing nanoparticles into tumors. However, convective fluid efflux may increase as interstitial tumor pressure declines during priming, increasing drug washout. We hypothesize that a targeting nanoparticle delivery system will increase drug retention during priming, thereby increasing efficacy. Approach: Patient-derived xenograft (PDX) PaCA tumors possessing varied stromal architecture and degrees of desmoplasia were implanted s.c. in SCID mice. They ranged from low- to high desmoplasia and varied in microvessel density. The sHH inhibitor (sHHI) NVP-LDE225 was administered p.o. for 10 days, and fluorescent 80nm sterically-stabilized liposomes (SSL) were administered at intervals to probe tumor vascular perfusion/permeability. Efficacy was investigated with SSL liposomes containing doxorubicin (SSL-DXR), optionally coupled covalently with Death Receptor 5 monoclonal antibody AMG655 (SSL-DXR-DR5), which binds the pro-apoptotic DR5 receptor and initiates the extrinsic apoptotic pathway. Results: Quantitative fluorescence microscopy showed that sHH inhibitor treatment mediated a temporal window of enhanced permeability/perfusion and deposition of SSL that varied with the amount of desmoplasia in PDX models, which are otherwise highly impermeant to SSL. Quantitative IFP measurements using the “wick and needle” technique showed reduction of IFP paralleled establishment of the priming window. In the absence of sHH inhibitor priming, SSL-DXR (2 mg/kg), SSL-DXR-DR5 (2 mg/kg of DXR), and free DR5 (dose-matched to SSL-DXR-DR5 protein) were administered to evaluate the effect of tumor priming on therapeutic efficacy. Any DR5-containing treatment was curative for MiaPaCA-2 tumors (high DR5 expression). The response of Panc-1 tumors (low DR5 expression) was greatest with SSL-DXR-DR5. Tumor responses with the PDX model #12424, (high DR5 expression) were greater in sHHI-treated animals compared to controls. SSL-DXR + free DR5 mediated a transient inhibition of tumor progression, whereas a durable inhibition of tumor progression was observed with SSL-DXR-DR5 immunoliposomes. Conclusions: Efficacy of SSL-DXR-DR5 immunoliposomes was superior to other treatments in two cell line-based tumors, and tumor response varied with DR5 receptor density. Efficacy in low permeability/perfusion PDX tumors was greatest following tumor priming by sHH inhibitors. Citation Format: Darren Chan, Charlene Minx, Jun Wang, Arindam Sen, Michael Johnston, Wen Wee Ma, Christopher J. Scott, Robert M. Straubinger. Efficacy of DR5-targeted immunoliposomes in pancreatic cancer models primed with SMO inhibitors [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 3704.

Abstract Pancreatic cancer (PaCA) is highly refractory to treatment, with a median survival of 6 months. Currently, gemcitabine (Gem), a difluoro analog of deoxycytidine, is the standard care for PaCA, but it renders only a modest survival benefit. Combination therapy, integrating novel agents into standard-of-care regimens, may maximize efficacy of Gem-based therapy. Fibroblast growth factor receptor (FGFR) function is aberrant in pancreatic cancer, and suppression of FGFRs inhibits pancreatic cancer growth and invasion. However, the mechanisms of FGFR action and their therapeutic utility in pancreatic cancer remain to be elucidated. Here we tested the hypothesis that FGFRs can impact Gem sensitivity of PaCA cells by employing pan-FGFR inhibitors and shRNAs against FGFRs. NVP-BGJ398 and AZD4547 are novel FGFR inhibitors (FGFRIs) specific to FGFR1, FGFR2 and FGFR3, and are in various stages of clinical trial. The FGFRIs modestly but significantly inhibited proliferation, migration, and invasion of PANC-1, MIAPaCa-2 cells in wound-healing and trans-well assays. Treatment with low-concentration Gem (7.5nM) enhanced MIAPaCa-2 cell migration at 24hrs, but migration was reduced subsequently, suggesting a sequence of delayed effects of Gem upon cell migration. After 72hrs of exposure, Gem combined with FGFRIs reduced MIAPaCa-2 cell proliferation significantly compared to controls or Gem- and FGFRI alone. Pharmacodynamic modeling was employed to evaluate drug interaction, and the interaction coefficient Psi was estimated by simultaneous modeling of 16 different drug combinations over a period of 0-96 hrs. The analysis estimated Psi=0.78, which indicates synergism. Compared to BGJ398 or Gem alone, the combination also increased the percentage of cells arrested at S phase for a longer period of time. Western blots revealed significant downregulation of ribonucleoside-diphosphate reductase large subunit (RRM1), DNA excision repair protein (ERCC1), and Epithelial-to-Mesenchymal transition biomarkers (vimentin and snail) with FGFRI/Gem treatment compared to Gem-treated cells, indicating that FGFRIs inhibit numerous factors that may contribute to Gem resistance. Loss-of-function by shRNA-mediated knockdown of FGFR1 in MIAPaCa-2 cells showed decreased expression of RRM1, whereas knockdown of FGFR2 and FGFR3 mediated an increase in RRM1 expression, implicating FGFR1 suppression in improving Gem-sensitivity. These results suggest that inhibition of FGFR1 could potentially enhance sensitivity of PaCA to Gem therapy, and that combining FGFRs with gemcitabine is a promising treatment strategy in pancreatic cancer. Citation Format: Qingxiang Lin, Tista Roy Chaudhuri, Ninfa L. Straubinger, Wen Wee Ma, Robert M. Straubinger. FGFR inhibitors enhance gemcitabine sensitivity in pancreatic ductal adenocarcinoma [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 4072. doi:10.1158/1538-7445.AM2017-4072

Abstract The majority of Pancreatic cancer (PaCA) patients present with metastatic disease and receive little benefit from chemotherapy. Although nanoparticulate carriers can potentially deposit sustained and high doses of chemotherapeutics in tumors, PaCA tumors are poorly perfused, which limits drug deposition. Ten days of oral dosing with NVP-LDE225 (40 mg/kg), an inhibitor of the sonic hedgehog (SHH) pathway (sHHI), increased tumor deposition of blood-borne, fluorescently labeled, sterically-stabilized lipidic (SSL) nanoparticles by enhancing the perfusion and permeability of the otherwise-impermeable microvasculature of PaCA patient-derived xenograft (PDX) tumors. However, literature indicates sHH ablation is associated with increased Epithelial-to-Mesenchymal (EMT) transition and invasiveness in PaCA. Here we investigated the compensatory role of FGFR1 in sHHI-induced tumor progression. Four to 8 daily treatments with the sHHI resulted in no significant reduction of tumor volume, but markedly increased the ratio of tumor cells (human mitochondria+) to Collagen1 in the stroma, in two s.c. low-passage PDX models of varying stromal content. Immunostaining of sHHI-treated tumors revealed no alteration in total FGFR1 expression, but showed a significant elevation in the (1) percent of FGFR1+ pixels correlating with DAPI+ nuclei in tumor (human mitochondria+) cells and stromal cells, (2) number of vimentin+ (EMT) cells, and (3) proliferative index marked by Ki67+ nuclei, compared to controls, suggesting accelerated tumor progression. Nuclear FGFR1 was associated with vimentin+ cells, but was excluded from the nuclei of Ki67+ cells in all groups, implicating nuclear translocation of FGFR1 in EMT. NVP-BGJ398, a small-molecule pan-FGFR inhibitor (FGFRI), administered p.o. for 3 days (15 mg/kg/day) after 7d of sHHI-pretreatment (1) significantly reduced nuclear localization of FGFR1 compared to sHHI-treated animals, (2) reversed the ratio of human mitochondria+ tumor cells to Collagen 1+ stroma, (3) depleted vimentin+ structures by >2 fold, and (4) reduced Ki67+ cells to control levels. FGFRI without sHHI-pretreatment resulted in decreased nuclear FGFR1 relative to controls, but did not impact proliferation, EMT, or tumor cell-to-stroma ratio. Finally, the sHHI/FGFRI sequence increased functional (FITC-L. esculentum lectin+) tumor vessel density and area the perfused by vascular permeability probes (fluorescent SSL) compared to both controls and sHHI-treated animals. FGFRI administration in vehicle-treated controls had no impact on vascular permeability or perfusion. We conclude that the combination of sHHI in sequence with FGFRI may reverse potentially deleterious effects of sHHI and mediate a transient enhancement of tumor permeability, and increase deposition and penetration of nanoparticulate SSL drug formulations into pancreatic cancers. Citation Format: Tista Roy Chaudhuri, Qingxiang Lin, Ninfa L. Straubinger, Wen Wee Ma, Robert M. Straubinger. FGFR1 inhibitor reverses Smoothened inhibition-induced epithelial-to-mesenchymal transition in pancreatic ductal adenocarcinoma [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 4071. doi:10.1158/1538-7445.AM2017-4071