Tumor eradication by triplet therapy with BRAF inhibitor, TLR 7 agonist, and PD-1 antibody for BRAF-mutated melanoma.

Programmed death 1 (PD-1)/programmed death-ligand 1 inhibitors are commonly used to treat various cancers, including melanoma. However, their efficacy as monotherapy is limited, and combination immunotherapies are being explored to improve outcomes. In this study, we investigated a combination immunotherapy involving an anti-PD-1 antibody that blocks the major adaptive immune-resistant mechanisms, a BRAF inhibitor that inhibits melanoma cell proliferation, and multiple primary immune-resistant mechanisms, such as cancer cell-derived immunosuppressive cytokines, and a Toll-like receptor 7 agonist that enhances innate immune responses that promote antitumor T-cell induction and functions. Using a xenogeneic nude mouse model implanted with human BRAF-mutated melanoma, a BRAF inhibitor vemurafenib was found to restore T-cell-stimulatory activity in conventional dendritic cells by reducing immunosuppressive cytokines, including interleukin 6, produced by human melanoma. Additionally, intravenous administration of the Toll-like receptor 7 agonist DSR6434 enhanced tumor growth inhibition by vemurafenib through stimulating the plasmacytoid dendritic cells/interferon-α/natural killer cell pathways and augmenting the T-cell-stimulatory activity of conventional dendritic cells. In a syngeneic mouse model implanted with murine BRAF-mutated melanoma, the vemurafenib and DSR6434 combination synergistically augmented the induction of melanoma antigen gp100-specific T cells and inhibited tumor growth. Notably, only triplet therapy with vemurafenib, DSR6434, and the anti-PD-1 antibody resulted in complete regression of SIY antigen-transduced BRAF-mutated melanoma in a CD8 T-cell-dependent manner. These findings indicate that a triple-combination strategy targeting adaptive and primary resistant mechanisms while enhancing innate immune responses that promote tumor-specific T cells may be crucial for effective tumor eradication.

Design, synthesis, and biological evaluation of phenylcyclopropylamine-entinostat conjugates that selectively target cancer cells.

Small molecule-based selective cancer cell-targeting can be a desirable anticancer therapeutic strategy. Aiming to discover such small molecules, we previously developed phenylcyclopropylamine (PCPA)-drug conjugates (PDCs) that selectively release anticancer agents in cancer cells where lysine-specific demethylase 1 (LSD1) is overexpressed. In this work, we designed PCPA-entinostat conjugates for selective cancer cell targeting. PCPA-entinostat conjugate 12 with a 4-oxybenzyl group linker released entinostat in the presence of LSD1 in in vitro assays and selectively inhibited the growth of cancer cells in preference to normal cells, suggesting the potential of PCPA-entinostat conjugates as novel anticancer drug delivery small molecules.

A Japanese multi-institutional phase II study of moderate hypofractionated intensity-modulated radiotherapy with image-guided technique for prostate cancer.

BACKGROUND: The aim of this multi-institutional phase II study was to confirm the safety and the potential efficacy of moderately hypofractionated intensity-modulated radiotherapy (IMRT) with prostate-based image-guidance for Japanese patients. METHODS: Patients with low- or intermediate-risk localized prostate cancer were eligible. Patients with a part of high risk (having only one of the following factors, cT3a, 20 < PSA ≤ 30, or GS = 8 or 9) were also included. Hypofractionated IMRT using daily image-guided technique with prostate matching was performed with a total dose of 70 Gy in 28 fractions. Neoadjuvant hormonal therapy for 4-8 months was mandatory for patients with intermediate or high-risk prostate cancer. RESULTS: From 20 institutions, 134 patients enrolled. The median follow-up was 5.16 years (range, 1.43-6.47 years). The number of patients with low, intermediate, and high-risk prostate cancer was 20, 80, and 34, respectively. The 5-year overall, biochemical failure-free, and clinical failure-free survival was 94.5%, 96.0%, and 99.2%, respectively. The 5-year biochemical failure-free survival for patients with low-, intermediate-, and high-risk disease was 94.1%, 97.4%, and 93.9%, respectively. The incidences of grade 2 gastrointestinal (GI) and genitourinary (GU) late toxicities at 5 years were 5.3% and 5.3%, respectively. There are no acute or late toxicities ≥ grade 3. Of 124 patients who were followed for up to 5 years, the grade 2 late GU or GI toxicities were 10.5% (90% confidence intervals, 6.3-16.2%, p = 0.0958). CONCLUSION: The safety and efficacy of moderately hypofractionated IMRT with prostate-based image-guidance was confirmed among Japanese patients with prostate cancer.

Real-world clinical outcomes in Japanese patients with locally advanced squamous cell carcinoma of the head and neck treated with radiotherapy plus cetuximab: a prospective observational study (JROSG12-2).

BACKGROUND: Radiotherapy plus cetuximab (bioradiotherapy: BRT) is a standard option in the treatment of locally advanced squamous cell carcinoma of the head and neck (LA-SCCHN). Published data on its safety and efficacy in real-world settings is limited. Here, we conducted a prospective multi-institutional observational study to evaluate clinical outcomes of BRT in patients with LA-SCCHN. METHODS: We analyzed real-world data of all patients who underwent BRT from 2013 to 2016. The primary endpoint was 1-year progression-free survival (PFS). Secondary endpoints were 1-year locoregional PFS (LPFS), treatment completion rate (TCR), and adverse events (AEs). RESULTS: A total of 171 patients with a minimum 1-year follow-up were analyzed. Median age was 67 (36-85) years, and 37 patients (21.6%) were aged 75 years or older. 1-year PFS and LPFS were 51.5 and 56.1%, respectively. N stage (p = 0.049) was significantly associated with PFS. TCR was 77.2%. Cetuximab was definitively discontinued in 30 patients (17.5%), in 15 cases due to severe mucositis. N stage, T stage, and comorbidity were significantly associated with TCR. Major AEs of grade 3 or higher were pharyngeal mucositis (48.5%), radiation dermatitis (45.6%), and oral mucositis (40.4%). Pneumonitis was observed in 12 patients (7.0%); 6 cases (3.5%) were grades 3-4 and 2 (1.2%) were grade 5. CONCLUSION: As a result of the large number of elderly patients in clinical practice,　toxicity reduced TCR. BRT-induced pneumonitis, which is sometimes fatal, was found to be more frequent than with chemotherapy plus cetuximab.

Real-world clinical outcomes and prognostic factors in Japanese patients with recurrent or metastatic squamous cell carcinoma of head and neck treated with chemotherapy plus cetuximab: a prospective observation study (JROSG12-2).

BACKGROUND: The aims of this study are to evaluate the efficacy and safety of first-line treatment with chemotherapy plus cetuximab in real-world patients with recurrent or metastatic squamous cell carcinoma of the head and neck (RM-SCCHN) and to identify prognostic factors for overall survival (OS). METHODS: This is a prospective observation study involving 20 oncology institutions in Japan. Patients with RM-SCCHN treated with a first-line therapy consisting of cetuximab plus any chemotherapy regimen between December 2013 and February 2017 were enrolled. The primary objective of the study was 1-year OS. Secondary objectives included response rate and adverse events. RESULTS: Of 120 patients recruited, 114 patients were analyzed. Median age was 64 years. Cetuximab in combination with platinum plus 5-FU (EXTREME regimen) was chosen in 86 patients (75.4%). The median OS was 12.4 months. A point estimate of the 1-year survival rate was 51.1%. Overall response rate was 26.3%. Grade 3 or worse adverse events included neutropenia (22.8%), hypokalemia (9.6%), acneiform rash (7.0%), pneumonitis (1.8%), and infusion-related reaction (0.9%). On multivariate analysis, regional lymph node metastasis, absence of intervention by dermatologists, lack of response to therapy, skin metastasis, and non-EXTREME regimen were identified as independent unfavorable prognostic factors for OS. CONCLUSION: The combination of cetuximab plus chemotherapy was tolerable and efficacious in patients with RM-SCCHN in a real-world setting. Clinical outcomes and prognostic factors extracted from this study provide a reference of the current clinical practice as well as for the future development of novel therapy in RM-SCCHN.

A phase II study of adaptive two-step intensity-modulated radiation therapy (IMRT) with chemotherapy for loco-regionally advanced nasopharyngeal cancer (JCOG1015).

BACKGROUND: A phase II study of adaptive two-step intensity-modulated radiotherapy (IMRT) with chemotherapy for nasopharyngeal cancer (NPC) (JCOG1015) was conducted to evaluate the efficacy and safety. METHODS: Patients aged 20-75 years with stages II-IVB NPC were enrolled. As adaptive two-step IMRT, computed tomography planning was performed twice before IMRT for the initial plan of 46 Gy/23 fractions and during treatment for the boost plan of 24 Gy/12 fractions with a total dose of 70 Gy. Chemotherapy (cisplatin 80 mg/m2/3-weeks × 3 courses) was administered concurrently with IMRT, followed by adjuvant chemotherapy (cisplatin at 70 mg/m2 with 5-FU 700 at mg/m2 for 5 days/4 weeks × 3 courses). RESULTS: Between 2011 and 2014, 75 patients were enrolled from 12 institutions. The 3-year overall survival (OS) for the 75 patients was 88%, and the upper and lower limits of the 95% CI of 78%-94% were higher than the expected 3-year OS of 75% for the target population adjusted by the actual proportion of stage II:III:IV = 21%:44%:35%. The 3-year progression-free survival (PFS) and loco-regional PFS were 71% [59-80%] and 77% [66-85%], respectively. Although no grade 4-5 late toxicities were observed, 15 patients (20%) developed grade 3 late toxicities. Grade 2 xerostomia was noted in 26%, 12%, and 9% at 1, 2, and 3 years after starting IMRT, respectively. CONCLUSIONS: Adaptive two-step IMRT for NPC demonstrated an excellent 3-year OS with acceptable toxicities. This method may be one treatment option for locally advanced NPC.

HDAC8 inhibition ameliorates pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a fibroproliferative lung disease, and fibroblast-myofibroblast differentiation (FMD) is thought to be a key event in the pathogenesis of IPF. Histone deacetylase-8 (HDAC8) has been shown to associate with α-smooth muscle actin (α-SMA; a marker of FMD) and regulates cell contractility in vascular smooth muscle cells. However, the role of HDAC8 in FMD or pulmonary fibrosis has never been reported. This study investigated the role of HDAC8 in pulmonary fibrosis with a focus on FMD. We observed that HDAC8 expression was increased in IPF lung tissue as well as transforming growth factor (TGF)ß1-treated normal human lung fibroblasts (NHLFs). Immunoprecipitation experiments revealed that HDAC8 was associated with α-SMA in TGFß1-treated NHLFs. HDAC8 inhibition with NCC170 (HDAC8-selective inhibitor) repressed TGFß1-induced fibroblast contraction and α-SMA protein expression in NHLFs cultured in collagen gels. HDAC8 inhibition with HDAC8 siRNA also repressed TGFß1-induced expression of profibrotic molecules such as fibronectin and increased expression of antifibrotic molecules such as peroxisome proliferator-activated receptor-γ (PPARγ). Chromatin immunoprecipitation quantitative PCR using an antibody against H3K27ac (histone H3 acetylated at lysine 27; a known HDAC8 substrate and a marker for active enhancers) suggested that HDAC8 inhibition with NCC170 ameliorated TGFß1-induced loss of H3K27ac at the PPARγ gene enhancer. Furthermore, NCC170 treatment significantly decreased fibrosis measured by Ashcroft score as well as expression of type 1 collagen and fibronectin in bleomycin-treated mouse lungs. These data suggest that HDAC8 contributes to pulmonary fibrosis and that there is a therapeutic potential for HDAC8 inhibitors to treat IPF as well as other fibrotic lung diseases.

Patient preference study comparing hypofractionated versus conventionally fractionated whole-breast irradiation after breast-conserving surgery.

OBJECTIVE: To compare patient preferences and acute adverse events of hypofractionated (HF) and conventionally fractionated (CF) whole-breast irradiation (WBI) after breast-conserving surgery in our institution. METHODS: We conducted a patient preference study comparing CF-WBI (50 Gy/25 fractions) and HF-WBI (41.6 Gy/16 fractions) after breast-conserving surgery. Eligible patients selected either type of fractionation following an explanation from the radiation oncologist. In this report, we analyzed the selection rate and acute toxicities. RESULTS: Between June 2009 and December 2013, 348 patients (349 breasts) were identified as eligible for the study. Among them, 259 patients (260 breasts [74.5%]) selected CF-WBI and 89 patients (89 breasts [25.5%]) selected HF-WBI. Factors significantly associated with the selection of HF-WBI were older age (P = 0.028) and no adjuvant chemotherapy (P = 0.041). Regarding acute adverse events, Grade 2 (G2) or higher radiation dermatitis was less frequently observed in HF-WBI than in CF-WBI (13.8% vs. 29.4%; P = 0.004). In addition, G2 or higher breast pain was only observed in the CF-WBI group (6.9%; P = 0.012). There were no significant differences in the presence of fatigue, wound pain or radiation pneumonitis of G2 or higher between the groups. CONCLUSIONS: In this study, in which patients themselves selected the irradiation method, more patients tended to select CF-WBI. The frequency of G2 or higher dermatitis and breast pain was significantly lower in the HF-WBI group than in the CF-WBI group. Our results support the evidence for recommending HF-WBI after breast-conserving surgery while presenting aspects of patient preferences.

Induction TPF chemotherapy followed by CRT with fractionated administration of cisplatin in patients with unresectable locally advanced head and neck cancer.

BACKGROUND: In treatment of locally advanced squamous cell carcinoma of the head and neck (SCCHN), the use of docetaxel, cisplatin, and 5-fluorouracil (TPF) followed by high-dose cisplatin chemoradiotherapy (CRT) carries concerns over toxicity. We evaluated the feasibility of TPF as induction chemotherapy (IC) to Japanese patients and the tolerability of CRT with fractionated administration of cisplatin after IC. METHODS: Patients with unresectable stage III, IV SCCHN received IC followed by CRT. IC consisted of three 3-week cycles of docetaxel 70-75 mg/m2 on day 1, cisplatin 70-75 mg/m2 on day 1, and 5-fluorouracil 750 mg/m2 on days 1-5. Patients subsequently received IMRT concomitant with fractionated administration of cisplatin (20 mg/m2) on days 1-4, repeated every 3 weeks. The primary endpoint was completion of the three cycles of IC. RESULTS: Forty-eight patients were enrolled. The IC treatment completion rate was 85%. Grade 3-4 toxicities of TPF were neutropenia (79%) and febrile neutropenia (15%). Thirty-eight patients (79%) achieved a response after IC. Forty patients subsequently underwent CRT. Thirty-three patients (83%) completed the planned cycles of fractionated administration of cisplatin, but seven (18%) did not. Grade 3-4 toxicities during CRT were neutropenia (23%), mucositis (53%), and dysphagia (33%). With a median follow-up of 36.1 months, 3-year overall survival was 65%. CONCLUSION: TPF IC is feasible and CRT with fractionated administration of cisplatin after IC is tolerable. IC followed by CRT appears to be a useful and safe sequential treatment. (Trial registration no. UMIN000024686).

Design, Synthesis, and Biological Evaluation of a Conjugate of 5-Fluorouracil and an LSD1 Inhibitor.

Prodrug approaches are useful for enhancing the efficacies and reducing the side effects of anticancer drugs. Previously, we proposed a prodrug strategy for targeting cancers overexpressing lysine-specific demethylase 1 (LSD1), namely, conjugates of trans-2-phenylcyclopropylamine (PCPA, an LSD1 inhibitor) and anticancer drugs. In this study, we applied this prodrug strategy to the anticancer agent 5-fluorouracil (5-FU). In vitro assays showed that the PCPA-5-FU conjugate (1) released 5-FU upon the inhibition of LSD1. Furthermore, the conjugate (1) exerted an antiproliferative effect on colon cancer HCT116 cells. Thus, the PCPA-5-FU conjugate (1) was able to function as a prodrug of 5-FU, activated by LSD1 inhibition, and provided a useful new lead structure for further development.

Drug Design Concepts for LSD1-Selective Inhibitors.

Lysine-specific demethylase 1 (LSD1) is one of the flavin-dependent oxidases and is involved in many cellular processes by controlling the methylation of histone H3. Recently, it has been reported that LSD1 is associated with several diseases such as cancer, metabolic disorders, and psychiatric diseases. Thus, LSD1 is an attractive molecular target for the treatment of these diseases, and its inhibitors are predicted as therapeutic agents. Although a variety of LSD1 inhibitors have been reported to date, many of them show insufficient activities and selectivity toward LSD1. Meanwhile, we identified several LSD1-selective inhibitors using target-guided synthesis strategies based on our original ideas. Our LSD1 inhibitors show not only potent LSD1-selective inhibitory activities, but also unique bioactivities both in vitro and in vivo. This account highlights our drug design concepts for and identification of LSD1-selective inhibitors.

Histone H3 peptides incorporating modified lysine residues as lysine-specific demethylase 1 inhibitors.

Lysine-specific demethylase 1 (LSD1) is a flavin-dependent enzyme that removes methyl groups from mono- or dimethylated lysine residues at the fourth position of histone H3. We have previously reported several histone H3 peptides containing an LSD1 inactivator motif at Lys-4. In this study, histone H3 peptides having a trans-2-phenylcyclopropylamine (PCPA), a 2,5-dihydro-1H-pyrrole, and a 1,2,3,6-tetrahydropyridine moiety at Lys-4 were prepared along with related compounds possessing a shorter side chain at the fourth position. Enzymatic assays showed that PCPA peptides containing a longer side chain, which can react with FAD in the active site, are potent LSD1-selective inhibitors.

Design, synthesis and evaluation of γ-turn mimetics as LSD1-selective inhibitors.

Lysine-specific demethylase 1 (LSD1) is an attractive molecular target for cancer therapy. We have previously reported potent LSD1-selective inhibitors (i.e., NCD18, NCD38, and their analogs) consisting of trans-2-phenylcyclopropylamine (PCPA) or trans-2-arylcyclopropylamine (ACPA) and a lysine moiety that could form a γ-turn structure in the active site of LSD1. Herein we report the design, synthesis and evaluation of γ-turn mimetic compounds for further improvement of LSD1 inhibitory activity and anticancer activity. Among a series of γ-turn mimetic compounds synthesized by a Mitsunobu-reaction-based amination strategy, we identified 1n as a potent and selective LSD1 inhibitor. Compound 1n induced cell cycle arrest and apoptosis through histone methylation in human lung cancer cells. The γ-turn mimetics approach should offer new insights into drug design for LSD1-selective inhibitors.

Design, Synthesis, and In Vitro Evaluation of Novel Histone H3 Peptide-Based LSD1 Inactivators Incorporating α,α-Disubstituted Amino Acids with γ-Turn-Inducing Structures.

Lysine-specific demethylase 1 (LSD1) mainly removes methyl groups of mono- or di-methylated lysine residues at the fourth position of histone H3 to epigenetically regulate the expression of genes associated with several diseases, such as cancer. Therefore, LSD1 inactivators are expected to be used as therapeutic agents. In this study, to identify novel peptide-based LSD1 inactivators, we focused on the X-ray structure of LSD1 complexed with a H3 peptide-based suicide substrate. It has been proposed that a methylated histone substrate forms three consecutive γ-turn structures in the active pocket of LSD1. Based on this, we designed and synthesized novel histone H3 peptide-based LSD1 inactivators 2a⁻c by incorporating various α,α-disubstituted amino acids with γ-turn-inducing structures. Among synthetic peptides 2a⁻c, peptide 2b incorporating two 1-aminocyclohexanecarboxylic acids at both sides of a lysine residue bearing a trans-2-phenylcyclopropylamine (PCPA) moiety, which is a pharmacophore for LSD1 inactivation, was the most potent and selective LSD1 inactivator. These findings are useful for the further development of histone H3 peptide-based LSD1 inactivators.

Retrospective analysis of definitive radiotherapy for neck node metastasis from unknown primary tumor: Japanese Radiation Oncology Study Group study.

OBJECTIVE: To investigate the optimal treatment method and risk factor of neck node metastasis from unknown primary tumors (NUP) treated by radiotherapy. METHODS: Retrospective case study based on a multi-institutional survey was conducted by the Japanese Radiation Oncology Study Group. Patients pathologically diagnosed as having NUP from 1998 to 2007 were identified. Univariate and multivariate analyses of overall survival (OS), progression free survival (PFS), neck progression free survival (NPFS) and mucosal progression free survival (MPFS) were evaluated. RESULTS: In total, 130 patients with median age of 65 years were included. Nodal stages N1, N2a, N2b and N2c were observed for 10, 26, 43, 12 and 39 patients, respectively. All the patients received radiotherapy (RT) with neck dissection in 60 and with chemotherapy in 67 cases. The median doses to the metastatic nodes, prophylactic neck and prophylactic mucosal sites were 60.0, 50.4 and 50.4 Gy, respectively. The median follow-up period for surviving patients was 42 months. Among 12 patients, occult primary tumors in the neck region developed after radiotherapy. The 5-year OS, PFS, NPFS and MPFS were 58.1%, 42.4%, 47.3% and 54.9%, respectively. Univariate analysis showed that lower N stage (N1-2b), non-bulky node (<6 cm) and negative extracapsular extension (ECE) status were the factors associated with favorable OS, PFS, NPFS and MPFS. Radical surgery proved to be a favorable factor of OS, NPFS and MPFS. On multivariate analysis, lower N stage and negative ECE status were correlated with improved survival. CONCLUSIONS: Lower nodal stage and negative ECE status showed a favorable impact on survival and disease control in patients with NUP treated by radiotherapy.

C-H activation enables a rapid structure-activity relationship study of arylcyclopropyl amines for potent and selective LSD1 inhibitors.

We describe the structure-activity relationship of various arylcyclopropylamines (ACPAs), which are potent LSD1 inhibitors. More than 45 ACPAs were synthesized rapidly by an unconventional method that we have recently developed, consisting of a C-H borylation and cross-coupling sequence starting from cyclopropylamine. We also generated NCD38 derivatives, which are known as LSD1 selective inhibitors, and discovered a more effective inhibitor compared to the original NCD38.

False HDAC Inhibition by Aurone Compound.

Fluorescence assays are useful tools for estimating enzymatic activity. Their simplicity and manageability make them suitable for screening enzyme inhibitors in drug discovery studies. However, researchers need to pay attention to compounds that show auto-fluorescence and quench fluorescence, because such compounds lower the accuracy of the fluorescence assay systems by producing false-positive or negative results. In this study, we found that aurone compound 7, which has been reported as a histone deacetylase (HDAC) inhibitor, gave false-positive results. Although compound 7 was identified by an in vitro HDAC fluorescence assay, it did not show HDAC inhibitory activity in a cell-based assay, leading us to suspect its in vitro HDAC inhibitory activity. As a result of verification experiments, we found that compound 7 interferes with the HDAC fluorescence assay by quenching the HDAC fluorescence signal. Our findings underscore the faults of fluorescence assays and call attention to careless interpretation.

Targeting Cancer with PCPA-Drug Conjugates: LSD1 Inhibition-Triggered Release of 4-Hydroxytamoxifen.

Targeting cancer with small molecule prodrugs should help overcome problems associated with conventional cancer-targeting methods. Herein, we focused on lysine-specific demethylase 1 (LSD1) to trigger the controlled release of anticancer drugs in cancer cells, where LSD1 is highly expressed. Conjugates of the LSD1 inhibitor trans-2-phenylcyclopropylamine (PCPA) were used as novel prodrugs to selectively release anticancer drugs by LSD1 inhibition. As PCPA-drug conjugate (PDC) prototypes, we designed PCPA-tamoxifen conjugates 1 a and 1 b, which released 4-hydroxytamoxifen in the presence of LSD1 in vitro. Furthermore, 1 a and 1 b inhibited the growth of breast cancer cells by the simultaneous inhibition of LSD1 and the estrogen receptor without exhibiting cytotoxicity toward normal cells. These results demonstrate that PDCs provide a useful prodrug method that may facilitate the selective release of drugs in cancer cells.

TLR7 tolerance is independent of the type I IFN pathway and leads to loss of anti-tumor efficacy in mice.

Systemic administration of small molecule toll-like receptor (TLR)-7 agonists leads to potent activation of innate immunity and to the generation of anti-tumor immune responses. However, activation of TLRs with small molecule agonists may lead to the induction of TLR tolerance, defined as a state of hyporesponsiveness to subsequent agonism, which may limit immune activation, the generation of anti-tumor responses and clinical response. Our data reveal that dose scheduling impacts on the efficacy of systemic therapy with the selective TLR7 agonist, 6-amino-2-(butylamino)-9-((6-(2-(dimethylamino)ethoxy)pyridin-3-yl)methyl)-7,9-dihydro-8H-purin-8-one (DSR-6434). In a preclinical model of renal cell cancer, systemic administration of DSR-6434 dosed once weekly resulted in a significant anti-tumor response. However, twice weekly dosing of DSR-6434 led to the induction of TLR tolerance, and no anti-tumor response was observed. We show that TLR7 tolerance was independent of type I interferon (IFN) negative feedback because induction of TLR7 tolerance was also observed in IFN-α/ß receptor knockout mice treated with DSR-6434. Moreover, our data demonstrate that treatment of bone marrow-derived plasmacytoid dendritic cells (BM-pDC) with DSR-6434 led to downregulation of TLR7 expression. From our data, dose scheduling of systemically administered TLR7 agonists can impact on anti-tumor activity through the induction of TLR tolerance. Furthermore, TLR7 expression on pDC may be a useful biomarker of TLR7 tolerance and aid in the optimization of dosing schedules involving systemically administered TLR7 agonists.

Histone H3 peptide based LSD1-selective inhibitors.

A series of candidates for the histone H3 peptide based LSD1-selective inhibitor were designed and synthesized. Among peptides 1a-c and 2a-c, peptide 1a, which has a phenylcyclopropylamine (PCPA) moiety at Lys-4 of the 21 amino acid residues of histone H3, was the most potent LSD1-selective inhibitor. Truncation studies of peptide 1a revealed the significance of the peptide sequence length. These findings will be useful for the further development of histone H3 peptide based LSD1-selective inhibitors.