Atezolizumab Plus PEGPH20 Versus Chemotherapy in Advanced Pancreatic Ductal Adenocarcinoma and Gastric Cancer: MORPHEUS Phase Ib/II Umbrella Randomized Study Platform.

BACKGROUND: The MORPHEUS platform comprises multiple open-label, randomized, phase Ib/II trials designed to identify early efficacy and safety signals of treatment combinations across cancers. Atezolizumab (anti-programmed cell death 1 ligand 1 [PD-L1]) was evaluated in combination with PEGylated recombinant human hyaluronidase (PEGPH20). METHODS: In 2 randomized MORPHEUS trials, eligible patients with advanced, previously treated pancreatic ductal adenocarcinoma (PDAC) or gastric cancer (GC) received atezolizumab plus PEGPH20, or control treatment (mFOLFOX6 or gemcitabine plus nab-paclitaxel [MORPHEUS-PDAC]; ramucirumab plus paclitaxel [MORPHEUS-GC]). Primary endpoints were objective response rates (ORR) per RECIST 1.1 and safety. RESULTS: In MORPHEUS-PDAC, ORRs with atezolizumab plus PEGPH20 (n = 66) were 6.1% (95% CI, 1.68%-14.80%) vs. 2.4% (95% CI, 0.06%-12.57%) with chemotherapy (n = 42). In the respective arms, 65.2% and 61.9% had grade 3/4 adverse events (AEs); 4.5% and 2.4% had grade 5 AEs. In MORPHEUS-GC, confirmed ORRs with atezolizumab plus PEGPH20 (n = 13) were 0% (95% CI, 0%-24.7%) vs. 16.7% (95% CI, 2.1%-48.4%) with control (n = 12). Grade 3/4 AEs occurred in 30.8% and 75.0% of patients, respectively; no grade 5 AEs occurred. CONCLUSION: Atezolizumab plus PEGPH20 showed limited clinical activity in patients with PDAC and none in patients with GC. The safety of atezolizumab plus PEGPH20 was consistent with each agent's known safety profile. (ClinicalTrials.gov Identifier: NCT03193190 and NCT03281369).

Synthesis and Evaluation of Camptothecin Antibody-Drug Conjugates.

Antibody-drug conjugates (ADCs) that incorporate the exatecan derivative DXd in their payload are showing promising clinical results in solid tumor indications. The payload has an F-ring that also contains a second chiral center, both of which complicate its synthesis and derivatization. Here we report on new camptothecin-ADCs that do not have an F-ring in their payloads yet behave similarly to DXd-bearing conjugates in vitro and in vivo. This simplification allows easier derivatization of camptothecin A and B rings for structure-activity relationship studies and payload optimization. ADCs having different degrees of bystander killing and the ability to release hydroxyl or thiol-bearing metabolites following peptide linker cleavage were investigated.

Tumour and host cell PD-L1 is required to mediate suppression of anti-tumour immunity in mice.

Expression of PD-L1, the ligand for T-cell inhibitory receptor PD-1, is one key immunosuppressive mechanism by which cancer avoids eradication by the immune system. Therapeutic use of blocking antibodies to PD-L1 or its receptor PD-1 has produced unparalleled, durable clinical responses, with highest likelihood of response seen in patients whose tumour or immune cells express PD-L1 before therapy. The significance of PD-L1 expression in each cell type has emerged as a central and controversial unknown in the clinical development of immunotherapeutics. Using genetic deletion in preclinical mouse models, here we show that PD-L1 from disparate cellular sources, including tumour cells, myeloid or other immune cells can similarly modulate the degree of cytotoxic T-cell function and activity in the tumour microenvironment. PD-L1 expression in both the host and tumour compartment contribute to immune suppression in a non-redundant fashion, suggesting that both sources could be predictive of sensitivity to therapeutic agents targeting the PD-L1/PD-1 axis.

pH- and Thiol-Responsive BODIPY-Based Photosensitizers for Targeted Photodynamic Therapy.

A diiodo distyryl boron dipyrromethene (BODIPY) core was conjugated to two ferrocenyl quenchers through acid-labile ketal and/or thiol-cleavable disulfide linkers, of which the fluorescence and photosensitizing properties were significantly quenched through a photoinduced electron-transfer process. The two symmetrical analogues that contained either the ketal or disulfide linkers could only be activated by a single stimulus, whereas the unsymmetrical analogue was responsive to dual stimuli. Upon interaction with acid and/or dithiothreitol (DTT), these linkers were cleaved selectively. The separation of the BODIPY core and the ferrocenyl moieties restored the photoactivities of the former in phosphate buffered saline and inside the MCF-7 breast cancer cells, rendering these compounds as potential activable photosensitizers for targeted photodynamic therapy. The dual activable analogue exhibited the greatest enhancement in intracellular fluorescence intensity in both an acidic environment (pH 5) and the presence of DTT (4 mm). Its photocytotoxicity against MCF-7 cells also increased by about twofold upon preincubation with 4 mm of DTT. The activation of this compound was also demonstrated in nude mice bearing a HT29 human colorectal carcinoma. A significant increase in fluorescence intensity in the tumor was observed over 9 h after intratumoral injection.

A dual activatable photosensitizer toward targeted photodynamic therapy.

An unsymmetrical bisferrocenyl silicon(IV) phthalocyanine has been prepared in which the disulfide and hydrazone linkers can be cleaved by dithiothreitol and acid, respectively. The separation of the ferrocenyl quenchers and the phthalocyanine core greatly enhances the fluorescence emission, singlet oxygen production, intracellular fluorescence intensity, and in vitro photocytotoxicity. The results have been compared with those for the two symmetrical analogues which contain either the disulfide or hydrazone linker and therefore can only be activated by one of these stimuli. For the dual activatable agent, the greatest enhancement can be attained under a slightly acidic environment (pH = 4.5-6.8) and in the presence of dithiothreitol (in millimolar range), which can roughly mimic the acidic and reducing environment of tumor tissues. This compound can also be activated in tumor-bearing nude mice. It exhibits an increase in fluorescence intensity in the tumor over the first 10 h after intratumoral injection and can effectively inhibit the growth of tumor upon illumination.

Inhibition of c-Kit is not required for reversal of hyperglycemia by imatinib in NOD mice.

AIM/HYPOTHESIS: Recent studies indicate that tyrosine kinase inhibitors, including imatinib, can reverse hyperglycemia in non-obese diabetic (NOD) mice, a model of type 1 diabetes (T1D). Imatinib inhibits c-Abl, c-Kit, and PDGFRs. Next-generation tyrosine kinase inhibitors for T1D treatment should maintain activities required for efficacy while sparing inhibition of targets that might otherwise lead to adverse events. In this study, we investigated the contribution of c-Kit inhibition by imatinib in reversal of hyperglycemia in NOD mice. METHODS: The T670I mutation in c-Kit, which confers imatinib resistance, was engineered into the mouse genome and bred onto the NOD background. Hematopoietic stem cells (HSCs) from NOD.c-Kit(T670I) mice and NOD.c-Kit(wt) littermates were expanded in the presence or absence of imatinib to verify imatinib resistance of the c-Kit(T670I) allele. Diabetic mice were treated with imatinib at the onset of hyperglycemia for three weeks, and blood glucose was monitored. RESULTS: In vitro expansion of HSCs from NOD.c-Kit(wt) mice was sensitive to imatinib, while expansion of HSCs from NOD.c-Kit(T670I) mice was insensitive to imatinib. However, in vivo treatment with imatinib lowered blood glucose levels in both strains of mice. CONCLUSIONS/INTERPRETATION: The HSC experiment confirmed that, in NOD.c-Kit(T670I) mice, c-Kit is resistant to imatinib. As both NOD.c-Kit(T670I) and NOD.c-Kit(wt) mice responded comparably to imatinib, c-Kit inhibition does not substantially contribute to the efficacy of imatinib in T1D. Thus, we conclude that inhibition of c-Kit is not required in next-generation tyrosine kinase inhibitors for T1D treatment, and may be selected against to improve the safety profile.

A disulfide-linked conjugate of ferrocenyl chalcone and silicon(IV) phthalocyanine as an activatable photosensitiser.

A novel bis(ferrocenyl chalcone) silicon(IV) phthalocyanine has been prepared in which the disulfide linker can be cleaved by dithiothreitol. The separation of the ferrocenyl quencher and the phthalocyanine core greatly enhances the fluorescence emission, singlet oxygen production and in vitro photocytotoxicity.

A zinc(II) phthalocyanine conjugated with an oxaliplatin derivative for dual chemo- and photodynamic therapy.

A novel zinc(II) phthalocyanine substituted with an oxaliplatin derivative via a triethylene glycol linker has been synthesized. The two components work in a cooperative manner in the antitumor action. The conjugate shows a cytotoxic effect in the dark due to the cytostatic oxaliplatin moiety and an enhanced cytotoxicity upon illumination due to the photosensitizing phthalocyanine unit against the HT29 human colon adenocarcinoma cells. The IC(50) value of the conjugate is as low as 0.11 µM, which is 5-fold lower than that of the reference compound without the platinum complex. The high photodynamic activity of the conjugate can be attributed to its high cellular uptake and efficiency in generating intracellular reactive oxygen species. The conjugate also shows preferential localization in the lysosomes of the cells and induces cell death mainly through apoptosis.

Preparation and photodynamic activities of silicon(IV) phthalocyanines substituted with permethylated ß-cyclodextrins.

A series of silicon(IV) phthalocyanines linked to two permethylated ß-cyclodextrin moieties through different spacers at the axial positions have been synthesized and characterized. The effects of these spacers on the photophysical properties and in vitro photodynamic activities have also been examined. Having two bulky hydrophilic substituents, all of these compounds are soluble and essentially nonaggregated in DMF and even in aqueous media. The fluorescence and singlet oxygen quantum yields in DMF are lower for the analogue with the shortest separation between the amino group in the spacer and the phthalocyanine ring. The fluorescence quantum yield of this compound increases in water probably due to protonation of the amino group, which inhibits the reductive quenching process. This series of compounds also exhibit photocytotoxicity toward HT29 human colon adenocarcinoma and HepG2 human hepatocarcinoma cells with IC(50) values in the range of 0.04-1.32 µM. The analogue with an α,ω-aminohydroxypentyl linker shows the highest potency, which can be ascribed to its high cellular uptake and high efficiency in generating intracellular reactive oxygen species. This compound also shows preferential localization in the lysosome, induces cell death mainly through apoptosis, and inhibits the growth of tumor in vivo. The results suggest that it is a promising photosensitizer for photodynamic therapy.

Primary cilia regulate Gli/Hedgehog activation in pancreas.

Previous studies have suggested that defects in pancreatic epithelium caused by activation of the Hedgehog (Hh) signaling pathway are secondary to changes in the differentiation state of the surrounding mesenchyme. However, recent results describe a role of the pathway in pancreatic epithelium, both during development and in adult tissue during neoplastic transformation. To determine the consequences of epithelial Hh activation during pancreas development, we employed a transgenic mouse model in which an activated version of GLI2, a transcriptional mediator of the pathway, is overexpressed specifically in the pancreatic epithelium. Surprisingly, efficient Hh activation was not observed in these transgenic mice, indicating the presence of physiological mechanisms within pancreas epithelium that prevent full Hh activation. Additional studies revealed that primary cilia regulate the level of Hh activation, and that ablation of these cellular organelles is sufficient to cause significant up-regulation of the Hh pathway in pancreata of mice overexpressing GLI2. As a consequence of overt Hh activation, we observe profound morphological changes in both the exocrine and endocrine pancreas. Increased Hh activity also induced the expansion of an undifferentiated cell population expressing progenitor markers. Thus, our findings suggest that Hh signaling plays a critical role in regulating pancreatic epithelial plasticity.

GLI1 is regulated through Smoothened-independent mechanisms in neoplastic pancreatic ducts and mediates PDAC cell survival and transformation.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by the deregulation of the hedgehog signaling pathway. The Sonic Hedgehog ligand (Shh), absent in the normal pancreas, is highly expressed in pancreatic tumors and is sufficient to induce neoplastic precursor lesions in mouse models. We investigated the mechanism of Shh signaling in PDAC carcinogenesis by genetically ablating the canonical bottleneck of hedgehog signaling, the transmembrane protein Smoothened (Smo), in the pancreatic epithelium of PDAC-susceptible mice. We report that multistage development of PDAC tumors is not affected by the deletion of Smo in the pancreas, demonstrating that autocrine Shh-Ptch-Smo signaling is not required in pancreatic ductal cells for PDAC progression. However, the expression of Gli target genes is maintained in Smo-negative ducts, implicating alternative means of regulating Gli transcription in the neoplastic ductal epithelium. In PDAC tumor cells, we find that Gli transcription is decoupled from upstream Shh-Ptch-Smo signaling and is regulated by TGF-beta and KRAS, and we show that Gli1 is required both for survival and for the KRAS-mediated transformed phenotype of cultured PDAC cancer cells.

Identification of elongation factor 1alpha as a potential associated binding partner for Akt2.

Akt protein kinase has been shown to play a pivotal role in diverse cell functions, including motility, apoptosis, growth and metabolism. How it differentially regulates these diverse functions is of significant interest. Three isoforms have been well characterized, Akt1, 2, and 3, encoded by separate genes, but showing high homology over the entire coding sequence (> 80%). An area of variability between the three isoforms is the C-terminal tail. To find potentially regulating binding partners of Akt2, the isoform implicated in metabolic control, we used a glutathione-S-transferase (GST) fusion protein expressing the C-terminal 75 residues of Akt2 (GST-Akt2 tail) to screen for proteins that specifically bound the Akt2 tail. Elongation factor 1alpha (EF1alpha) and beta-tubulin were identified as binding partners for the Akt2 tail by peptide mass fingerprinting. These two proteins have themselves been previously identified as interacting partners (Nakazawa et al.FEBS Lett. 453,29-34, 1999). Using CHOT cells that overexpress insulin receptors and HA-tagged Akt2, we showed that EF1alpha co-immunoprecipitated with HA-tagged Akt2. It is thus possible that these proteins colocalise as part of a regulatory signaling complex with the cytoskeleton directing them to sites of cell activity.

Stabilization of beta-catenin impacts pancreas growth.

A recent study has shown that deletion of beta-catenin within the pancreatic epithelium results in a loss of pancreas mass. Here, we show that ectopic stabilization of beta-catenin within mouse pancreatic epithelium can have divergent effects on both organ formation and growth. Robust stabilization of beta-catenin during early organogenesis drives changes in hedgehog and Fgf10 signaling and induces a loss of Pdx1 expression in early pancreatic progenitor cells. Together, these perturbations in early pancreatic specification culminate in a severe reduction of pancreas mass and postnatal lethality. By contrast, inducing the stabilized form of beta-catenin at a later time point in pancreas development causes enhanced proliferation that results in a dramatic increase in pancreas organ size. Taken together, these data suggest a previously unappreciated temporal/spatial role for beta-catenin signaling in the regulation of pancreas organ growth.