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Owing to the marked sexual dimorphism of hepatocellular carcinoma (HCC), sex hormone receptor signaling has been implicated in numerous aspects of liver cancer pathogenesis. We sought to reconcile the clear contribution of androgen receptor (AR) activity that has been established in preclinical models of HCC with the clinical failure of AR antagonists in patients with advanced HCC by evaluating potential resistance mechanisms to AR-targeted therapy. The AR locus was interrogated for resistance-causing genomic modifications using publicly available primary HCC datasets (1,019 samples). Analysis of HCC tumor and cell line RNA-seq data revealed enriched expression of constitutively active, treatment-refractory AR splice variants (AR-SV). HCC cell lines expressed C-terminal–truncated AR-SV; 28 primary HCC samples abundantly expressed AR-SV. Low molecular weight AR species were nuclear localized and constitutively active. Furthermore, AR/AR-SV signaling promoted AR-mediated HCC cell progression and conferred resistance to AR antagonists. Ligand-dependent and -independent AR signaling mediated HCC epithelial-to-mesenchymal transition by regulating the transcription factor SLUG. These data suggest that AR-SV expression in HCC drives HCC progression and resistance to traditional AR antagonists. Novel therapeutic approaches that successfully target AR-SVs may be therapeutically beneficial for HCC.Significance:Treatment-refractory, constitutively active androgen receptor splice variants promote hepatocellular carcinoma progression by regulating the epithelial-to-mesenchymal transition pathway.

These tables contain relevant patient characteristics, primer sequence information for RT-PCR, whole genome sequencing read statistics, and a tabulation of DEGS from publicly available HCC cell RNA-seq data.

Missing or erroneous information is a common problem in the analysis of pharmacokinetic (PK) data. This may present as missing or inaccurate dose level or dose time, drug concentrations below the analytical limit of quantification, missing sample times, or missing or incorrect covariate information. Several methods to handle problematic data have been evaluated, although no single, broad set of recommendations for commonly occurring errors has been published. In this tutorial, we review the existing literature and present the results of our simulation studies that evaluated common methods to handle known data errors to bridge the remaining gaps and expand on the existing knowledge. This tutorial is intended for any scientist analyzing a PK data set with missing or apparently erroneous data. The approaches described herein may also be useful for the analysis of nonclinical PK data.

BackgroundConventional dendritic cells subtype 1 (cDC1) play a vital role in the priming and expansion of tumor specific CD8+ T cells and their recruitment to tumor microenvironment (TME). However, cDC1s are often underrepresented in the TME. Systemic administration of Fms-like tyrosine kinase 3 ligand (FLT3L), a hematopoietic growth factor that binds to FLT3 on myeloid and lymphoid progenitor cells, leads to expansion of cDC1s in the periphery which can then be recruited into the TME. FLT3 pathway stimulation using GS-3583, a novel FLT3 agonistic Fc fusion protein, has the potential to promote T cell mediated anti-tumor activity. We sought to evaluate the pharmacodynamic (PD) effect of a single dose of GS-3583 in healthy volunteers alongside its safety. Herein, we present the updated results of the study.MethodsThis was a first-in-human, placebo-controlled study of GS-3583 in healthy volunteers to evaluate the safety, pharmacokinetics (PK), and PD of escalating single doses (ranging from 75 micrograms to 2000 micrograms) of GS-3583. The study was blinded to the subjects and the investigator. Each dose cohort enrolled 8–12 healthy subjects who received GS-3583 or placebo as single IV infusion at 3:1 ratio. Subjects were observed in the phase 1 unit for 15 days and then for 12 weeks as outpatients. As part of the PD evaluation, we investigated the changes in the number of cDC1 and cDC2 cells.ResultsAs of 2nd July 2021, selected safety, PK and PD data from all 4 cohorts were available. GS-3583 was well tolerated and all subjects had been discharged. To date, there have been no serious or grade 3 or higher adverse events. Preliminary PK analysis suggested dose-dependent increase in GS-3583 exposure (AUC and Cmax). Preliminary PD analysis shows that administration of GS-3583 resulted in temporary, dose-dependent increases in cDC1/cDC2 cells that peaked between days 5–11 (higher doses resulted in later peaks) and returned to baseline within 3 weeks of drug administration (table 1, figure 1).Abstract 380 Table 1Selected subject characteristics and pharmacodynamic resultsAbstract 380 Figure 1A) Comparison of cDC1 cell quantitative changes in cohorts 1–4; B) Comparison of cDC2 cell quantitative changes in cohorts 1–4ConclusionsGS-3583 infusion was well tolerated and induced dose dependent expansion of dendritic cells in the periphery in healthy volunteers. In patients with cancer, this increase in dendritic cells can be utilized to enhance anti-tumor therapeutic effects of immuno-oncology therapies.AcknowledgementsFunding provided by Gilead Sciences, Inc.Ethics ApprovalThe study received study site IRB/Ethics Committee approval prior to enrollment of subjects.

Hairy cell leukemia (HCL) is a rare B-cell malignancy, and there is a need for novel treatments for patients who do not benefit from purine analogs. Ibrutinib, an oral agent targeting Bruton tyrosine kinase in the B-cell receptor signaling pathway, is highly effective in several malignancies. Its activity in HCL was unknown, so we conducted a multisite phase 2 study of oral ibrutinib in patients with either relapsed classic or variant hairy cell leukemia. The primary outcome measure was the overall response rate (ORR) at 32 weeks, and we also assessed response at 48 weeks and best response during treatment. Key secondary objectives were characterization of toxicity and determination of progression-free survival (PFS) and overall survival (OS). Thirty-seven patients were enrolled at 2 different doses (24 at 420 mg, 13 at 840 mg). The median duration of follow-up was 3.5 years (range, 0-5.9 years). The ORR at 32 weeks was 24%, which increased to 36% at 48 weeks. The best ORR was 54%. The estimated 36-month PFS was 73% and OS was 85%. The most frequent adverse events were diarrhea (59%), fatigue (54%), myalgia (54%), and nausea (51%). Hematologic adverse events were common: anemia (43%), thrombocytopenia (41%), and neutropenia (35%). Ibrutinib can be safely administered to patients with HCL with objective responses and results in prolonged disease control. Although the initial primary outcome objective of the study was not met, the observation of objective responses in heavily pretreated patients coupled with a favorable PFS suggests that ibrutinib may be beneficial in these patients. This trial was registered at www.clinicaltrials.gov as #NCT01841723.

No approved therapy exists for cancer‐associated cachexia. The colon‐26 mouse model of cancer cachexia mimics recent late‐stage clinical failures of anabolic anti‐cachexia therapy and was unresponsive to anabolic doses of diverse androgens, including the selective androgen receptor modulator (SARM) GTx‐024. The histone deacetylase inhibitor (HDACi) AR‐42 exhibited anti‐cachectic activity in this model. We explored combined SARM/AR‐42 therapy as an improved anti‐cachectic treatment paradigm. A reduced dose of AR‐42 provided limited anti‐cachectic benefits, but, in combination with GTx‐024, significantly improved body weight, hindlimb muscle mass, and grip strength versus controls. AR‐42 suppressed the IL‐6/GP130/STAT3 signaling axis in muscle without impacting circulating cytokines. GTx‐024‐mediated β‐catenin target gene regulation was apparent in cachectic mice only when combined with AR‐42. Our data suggest cachectic signaling in this model involves catabolic signaling insensitive to anabolic GTx‐024 therapy and a blockade of GTx‐024‐mediated anabolic signaling. AR‐42 mitigates catabolic gene activation and restores anabolic responsiveness to GTx‐024. Combining GTx‐024, a clinically established anabolic therapy, with AR‐42, a clinically evaluated HDACi, represents a promising approach to improve anabolic response in cachectic patients., Cancer cachexia increases morbidity and mortality of cancer patients. Given the multifactorial pathogenesis of cachexia, effective treatment remains elusive. Here, a novel therapeutic strategy combining anti‐catabolic and anabolic activities is established in a murine model of cancer cachexia.

High-dose melphalan (HDM) is part of the conditioning regimen in patients with multiple myeloma (MM) receiving autologous stem cell transplantation (ASCT). However, individual sensitivity to melphalan varies, and many patients experience severe toxicities. Prolonged severe neutropenia is one of the most severe toxicities and contributes to potentially life-threatening infections and failure of ASCT. Granulocyte-colony stimulating factor (G-CSF) is given to stimulate neutrophil proliferation after melphalan administration. The aim of this study was to develop a population pharmacokinetic/pharmacodynamic (PK/PD) model capable of predicting neutrophil kinetics in individual patients with MM undergoing ASCT with high-dose melphalan and G-CSF administration. The extended PK/PD model incorporated several covariates, including G-CSF regimen, stem cell dose, hematocrit, sex, creatinine clearance, p53 fold change, and race. The resulting model explained portions of interindividual variability in melphalan exposure, therapeutic effect, and feedback regulation of G-CSF on neutrophils, thus enabling simulation of various doses and prediction of neutropenia duration.

The mTOR pathway is activated in about 50% of patients with hepatocellular carcinoma (HCC). In an effort to identify new pathways and compounds to treat advanced HCC, we considered the ATP-competitive mTOR inhibitor INK128. ATP-competitive mTOR inhibitors attenuate both mTORC1 and mTORC2. INK128 was evaluated in sorafenib sensitive and insensitive HCC cell lines, CD44low and CD44high HCC and those cell lines with acquired sorafenib resistance. CD44 was significantly increased in Huh7 cells made resistant to sorafenib. Forced expression of CD44 enhanced cellular proliferation and migration, and rendered the cells more sensitive to the anti-proliferative effects of INK128. INK128 suppressed CD44 expression in HCC cells while allosteric mTOR inhibitors did not. CD44 inhibition correlated with 4EBP1 phosphorylation status. INK128 showed better anti-proliferative and anti-migration effects on the mesenchymal-like HCC cells, CD44high HCC cells compared to the allosteric mTOR inhibitor everolimus. Moreover, a combination of INK128 and sorafenib showed improved anti-proliferative effects in CD44high HCC cells. INK128 was efficacious at reducing tumor growth in CD44high SK-Hep1 xenografts in mice when given as monotherapy or in combination with sorafenib. Since the clinical response to sorafenib is highly variable, our findings suggest that ATP-competitive mTOR inhibitors may be effective in treating advanced, CD44-expressing HCC patients who are insensitive to sorafenib.

Owing to the marked sexual dimorphism of hepatocellular carcinoma (HCC), sex hormone receptor signaling has been implicated in numerous aspects of liver cancer pathogenesis. We sought to reconcile the clear contribution of androgen receptor (AR) activity that has been established in preclinical models of HCC with the clinical failure of AR antagonists in patients with advanced HCC by evaluating potential resistance mechanisms to AR-targeted therapy. The AR locus was interrogated for resistance-causing genomic modifications using publicly available primary HCC datasets (1,019 samples). Analysis of HCC tumor and cell line RNA-seq data revealed enriched expression of constitutively active, treatment-refractory AR splice variants (AR-SV). HCC cell lines expressed C-terminal–truncated AR-SV; 28 primary HCC samples abundantly expressed AR-SV. Low molecular weight AR species were nuclear localized and constitutively active. Furthermore, AR/AR-SV signaling promoted AR-mediated HCC cell progression and conferred resistance to AR antagonists. Ligand-dependent and -independent AR signaling mediated HCC epithelial-to-mesenchymal transition by regulating the transcription factor SLUG. These data suggest that AR-SV expression in HCC drives HCC progression and resistance to traditional AR antagonists. Novel therapeutic approaches that successfully target AR-SVs may be therapeutically beneficial for HCC. Significance: Treatment-refractory, constitutively active androgen receptor splice variants promote hepatocellular carcinoma progression by regulating the epithelial-to-mesenchymal transition pathway.

TPS3147 Background: Productive antitumor immune responses in nonclinical models depend on a type of dendritic cell (DC), conventional DC subtype 1 (cDC1), which in the context of cancer, primes tumor-reactive T cells through presentation of tumor-derived antigens. FMS-related tyrosine kinase 3 ligand (FLT3L) is a hematopoietic growth factor that binds to and activates FLT3 on terminally differentiated DCs. Activated FLT3 promotes proliferation, inhibits cell death, and is required for the differentiation, expansion, and maintenance of DCs in peripheral and lymphoid organs. GS-3583 is a fusion protein composed of the extracellular domain of recombinant human FLT3L fused to an engineered fragment crystallizable (Fc) region of human immunoglobulin G4. GS-3583 has PK properties that support sustained cDC in patients and potential combination with established immunotherapies. This phase 1b, open-label, multicenter, dose-finding study will evaluate safety, tolerability, PK, and preliminary efficacy of GS-3583 monotherapy in patients with advanced solid tumors (NCT04747470). Methods: Approximately 33 adults aged ≥18 years with a histologically or cytologically confirmed locally advanced or metastatic malignant solid tumor that is refractory to or intolerant of standard therapy or for which no standard therapy is available will be enrolled. The study employs a 3+3 dose escalation design in which GS-3583 is administered intravenously for up to 52 weeks or until progressive disease or unacceptable toxicity. Up to five dose escalation cohorts have been planned. The maximum tolerated dose is the highest dose with incidence of DLT in < 33% of 6 or more patients in the first 28 days of GS-3583 dosing; recommended phase 2 dose will be determined. Assessments include safety, PK, pharmacodynamics including cDCs, immunogenicity, and efficacy by RECIST 1.1 in CT/MRI imaging conducted every 8 weeks. Accrual at approximately 3-4 centers in the US is ongoing. Clinical trial information: NCT04747470.

2559 Background: Conventional dendritic cells subtype 1 (cDC1) play a vital role in the priming and expansion of tumor specific CD8+ T cells and their recruitment to tumor microenvironment (TME). However, cDC1s are often underrepresented in the TME. Systemic administration of Fms-like tyrosine kinase 3 ligand (FLT3L), a hematopoietic growth factor that binds to FLT3 on myeloid and lymphoid progenitor cells, leads to expansion of cDC1s in the periphery which can then be recruited into the TME. We hypothesize that FLT3 pathway stimulation using GS-3583, a FLT3 agonist Fc fusion protein, has the potential to promote T cell mediated anti-tumor activity. Methods: This was a first-in-human placebo-controlled study of GS-3583 in healthy volunteers to evaluate the safety, PK, and PD of escalating single doses (ranging from 75μg to 2000μg) of GS-3583. The study was blinded to the subjects and the investigator. Each dose cohort enrolled 8-12 healthy subjects who received GS-3583 or placebo as single IV infusion at 3:1 ratio. Subjects were observed in the phase 1 unit for 15 days and then for 12 weeks as outpatients. As part of the PD evaluation, we investigated the changes in the number of cDC1s and cDC subtype 2 (cDC2) cells. Results: As of 8th Feb 2021, selected safety, PK and PD data from the first 3 cohorts were available. GS-3583 was well tolerated and all subjects had been discharged. To date, there have been no serious or grade 3 or higher adverse events. Preliminary PK analysis suggested dose-dependent increase in GS-3583 exposure (AUC and Cmax). Preliminary PD analysis shows that administration of GS-3583 resulted in dose-dependent increases in cDC1/cDC2 cells that peaked at day 5 or day 8 and returned to baseline within three weeks of drug administration. Conclusions: GS-3583 was safe and well tolerated and induced dose dependent expansion of dendritic cells in the periphery. In patients with cancer, this increase in dendritic cells can be utilized to enhance anti-tumor responses to immuno-oncology therapies.[Table: see text]

Cholesterol-lowering response to 40 mg simvastatin daily for 6 weeks was examined for associations with common genetic polymorphisms in key genes affecting simvastatin metabolism (CYP3A4 and CYP3A5) and transport (SLCO1B1). In white people (n = 608), SLCO1B1 521C was associated with lesser reductions of total and low-density lipoprotein cholesterol. Associations between SLCO1B1 521C and cholesterol response were not detected in African Americans (n = 333). Associations between CYP3A4*22 or CYP3A5*3 and cholesterol response were not detected in either race, and no significant race-gene or gene-gene interactions were detected. As several of the analyses may have been underpowered (especially the analyses in the African American cohort), the findings not suggesting an association should not be considered conclusive and warrant further investigation. The finding regarding SLCO1B1 521C in whites was consistent with several previous reports. SLCO1B1 521C resulted in a diminished cholesterol-lowering response, but a marginal effect size limits utility for predicting simvastatin response.

Summary Statin-induced myopathy (SIM) is the most common reason for discontinuation of statin therapy. A polymorphism affecting the gene encoding glycine amidinotransferase ( GATM rs9806699 G > A) was previously associated with reduced risk for SIM. Our objective was to replicate the GATM association in a large, multicenter SIM case-control study. Mild and severe SIM cases and age- and gender-matched controls were enrolled. Participants were genotyped, and associations were tested (n = 715) using chi-square and logistic regression with consideration for SIM severity and exclusion of subjects with potentially confounding comedications. The minor allele (A) frequencies of GATM rs9806699 in the controls (n = 106), mild SIM (n = 324), and severe SIM (n = 285) cases were 0.26, 0.28, and 0.29, respectively (p = 0.447). The unadjusted odds ratio for the A allele for any SIM (mild or severe) was 1.14 (0.82–1.61; p = 0.437), which remained nonsignificant in all models. Our results do not replicate the association between GATM rs9806699 and SIM.

PurposeThe common colon-26 mouse (C-26) model of experimental cachexia mimics recent late stage clinical failures of anabolic anti-cachexia therapy, and does not respond to the anabolic selective androgen receptor modulator (SARM) GTx-024. Based on the demonstrated anti-cachectic efficacy of the histone deacetylase inhibitor (HDACi) AR-42 in this model, we hypothesized that combined SARM/AR-42 would provide improved anti-cachectic efficacy.DesignIn the C-26 model, we determined a reduced efficacious dose of AR-42 which was combined with anabolic SARM therapy and evaluated for anti-cachectic efficacy. The effects of treatment and tumor burden on anabolic and catabolic signaling occurring in skeletal muscle were characterized using muscle performance parameters and RNA-seq.ResultsAnabolic anti-cachexia therapy with diverse androgens had no impact on cachectic outcomes in the C-26 model. A reduced dose of the HDACi AR-42 alone provided limited anti-cachectic benefits, but when combined with the SARM GTx-024, significantly improved bodyweight (pConclusionsCachectic signaling in the C-26 model is comprised of catabolic signaling insensitive to anabolic GTx-024 therapy and a blockade of GTx-024-mediated anabolic signaling. AR-42 treatment mitigates catabolic gene activation and restores anabolic responsiveness to GTx-024. Combining GTx-024, a clinically established anabolic therapy, with a low dose of AR-42, a clinically evaluated HDACi, represents a promising approach to improve anabolic response in cachectic patient populations.

e14017Background: In this Phase I study, we evaluated the ability of the DNA alkylating agent, bendamustine (BD), to serve as a radiosensitizer in patients receiving stereotactic radiotherapy (SRT)...