Phase I Study of SYNB1891, an Engineered E. coli Nissle Strain Expressing STING Agonist, with and without Atezolizumab in Advanced Malignancies

PURPOSE

SYNB1891 is a live, modified strain of the probiotic Escherichia coli Nissle 1917 (EcN) engineered to produce cyclic dinucleotides under hypoxia, leading to STimulator of INterferon Genes (STING) activation in phagocytic antigen-presenting cells in tumors and activating complementary innate immune pathways.

PATIENTS AND METHODS

This first-in-human study (NCT04167137) enrolled participants with refractory advanced cancers to receive repeat intratumoral injections of SYNB1891 either alone or in combination with atezolizumab, with the primary objective of evaluating the safety and tolerability of both regimens.

RESULTS

Twenty-four participants received monotherapy across six cohorts, and 8 participants received combination therapy in two cohorts. Five cytokine release syndrome events occurred with monotherapy, including one that met the criteria for dose-limiting toxicity at the highest dose; no other SYNB1891-related serious adverse events occurred, and no SYNB1891-related infections were observed. SYNB1891 was not detected in the blood at 6 or 24 hours after the first intratumoral dose or in tumor tissue 7 days following the first dose. Treatment with SYNB1891 resulted in activation of the STING pathway and target engagement as assessed by upregulation of IFN-stimulated genes, chemokines/cytokines, and T-cell response genes in core biopsies obtained predose and 7 days following the third weekly dose. In addition, a dose-related increase in serum cytokines was observed, as well as stable disease in 4 participants refractory to prior PD-1/L1 antibodies.

CONCLUSIONS

Repeat intratumoral injection of SYNB1891 as monotherapy and in combination with atezolizumab was safe and well tolerated, and evidence of STING pathway target engagement was observed.

Phase I study to assess the effect of adavosertib (AZD1775) on the pharmacokinetics of substrates of CYP1A2, CYP2C19, and CYP3A in patients with advanced solid tumors

PURPOSE

Adavosertib may alter exposure to substrates of the cytochrome P450 (CYP) family of enzymes. This study assessed its effect on the pharmacokinetics of a cocktail of probe substrates for CYP3A (midazolam), CYP2C19 (omeprazole), and CYP1A2 (caffeine).

METHODS

Period 1: patients with locally advanced or metastatic solid tumors received 'cocktail': caffeine 200 mg, omeprazole 20 mg, and midazolam 2 mg (single dose); period 2: after 7- to 14-day washout, patients received adavosertib 225 mg twice daily on days 1-3 (five doses), with cocktail on day 3. After cocktail alone or in combination with adavosertib administration, 24-h pharmacokinetic sampling occurred for probe substrates and their respective metabolites paraxanthine, 5-hydroxyomeprazole (5-HO), and 1'-hydroxymidazolam (1'-HM). Safety was assessed throughout.

RESULTS

Of 33 patients (median age 60.0 years, range 41-83) receiving cocktail, 30 received adavosertib. Adavosertib co-administration increased caffeine, omeprazole, and midazolam exposure by 49%, 80%, and 55% (AUC_0-12), respectively; AUC_0-t increased by 61%, 98%, and 55%. Maximum plasma drug concentration (C_max) increased by 4%, 46%, and 39%. Adavosertib co-administration increased 5-HO and 1'-HM exposure by 43% and 54% (AUC_0-12) and 49% and 58% (AUC0-t), respectively; paraxanthine exposure was unchanged. Adavosertib co-administration decreased C_max for paraxanthine and 5-HO by 19% and 7%; C_max increased by 33% for 1'-HM. After receiving adavosertib, 19 (63%) patients had treatment-related adverse events (six [20%] grade ≥ 3).

CONCLUSION

Adavosertib (225 mg bid) is a weak inhibitor of CYP1A2, CYP2C19, and CYP3A.

CLINICALTRIALS

GOV: NCT03333824.

Adavosertib (AZD1775) does not prolong the QTc interval in patients with advanced solid tumors: a phase I open-label study

PURPOSE

Adavosertib is a small-molecule, ATP-competitive inhibitor of Wee1 kinase. Molecularly targeted oncology agents have the potential to increase the risk of cardiovascular events, including prolongation of QT interval and associated cardiac arrhythmias. This study investigated the effect of adavosertib on the QTc interval in patients with advanced solid tumors.

METHODS

Eligible patients were ≥ 18 years of age with advanced solid tumors for which no standard therapy existed. Patients received adavosertib 225 mg twice daily on days 1-2 at 12-h intervals and once on day 3. Patients underwent digital 12-lead electrocardiogram and pharmacokinetic assessments pre-administration and time-matched assessments during the drug administration period. The relationship between maximum plasma drug concentration (C_max) and baseline-adjusted corrected QT interval by Fridericia (QTcF) was estimated using a prespecified linear mixed-effects model.

RESULTS

Twenty-one patients received adavosertib. Concentration-QT modeling of ΔQTcF and the upper limit of the 90% confidence interval corresponding to the geometric mean of C_max observed on days 1 and 3 were below the threshold for regulatory concern (not > 10 ms). No significant relationship between ΔQTcF (vs baseline) and adavosertib concentration was identified (P = 0.27). Pharmacokinetics and the adverse event (AE) profile were consistent with previous studies at this dose. Eleven (52.4%) patients experienced 17 treatment-related AEs in total, including diarrhea and nausea (both reported in six [28.6%] patients), vomiting (reported in two [9.5%] patients), anemia, decreased appetite, and constipation (all reported in one [4.8%] patient).

CONCLUSION

Adavosertib does not have a clinically important effect on QTc prolongation.

CLINICALTRIALS

GOV: NCT03333824.

Subsea permafrost organic carbon stocks are large and of dominantly low reactivity

Subsea permafrost carbon pools below the Arctic shelf seas are a major unknown in the global carbon cycle. We combine a numerical model of sedimentation and permafrost evolution with simplified carbon turnover to estimate accumulation and microbial decomposition of organic matter on the pan-Arctic shelf over the past four glacial cycles. We find that Arctic shelf permafrost is a globally important long-term carbon sink storing 2822 (1518-4982) Pg OC, double the amount stored in lowland permafrost. Although currently thawing, prior microbial decomposition and organic matter aging limit decomposition rates to less than 48 Tg OC/yr (25-85) constraining emissions due to thaw and suggesting that the large permafrost shelf carbon pool is largely insensitive to thaw. We identify an urgent need to reduce uncertainty in rates of microbial decomposition of organic matter in cold and saline subaquatic environments. Large emissions of methane more likely derive from older and deeper sources than from organic matter in thawing permafrost.

Estimating the aquatic risk from exposure to up to twenty-two pesticide active ingredients in waterways discharging to the Great Barrier Reef

Pesticides decrease the quality of water reaching the Great Barrier Reef (GBR), Australia. Up to 86 pesticide active ingredients (PAIs) were monitored between July 2015 to end of June 2018 at 28 sites in waterways that discharge to the GBR. Twenty-two frequently detected PAIs were selected to calculate their combined risk when they co-occur in water samples. Species sensitivity distributions (SSDs) for the 22 PAIs to fresh and marine species were developed. The SSDs, the multi-substance potentially affected fraction (msPAF) method, Independent Action model of joint toxicity and a Multiple Imputation method were combined to convert measured PAI concentration data to estimates of the Total Pesticide Risk for the 22 PAIs (TPR₂₂) expressed as the average percentage of species affected during the wet season (i.e., 182 days). The TPR₂₂ and percent contribution of active ingredients of Photosystem II inhibiting herbicides, Other Herbicides, and Insecticides to the TPR₂₂ were estimated. The TPR₂₂ ranged from <1 % to 42 % of aquatic species being affected. Approximately 85 % of the TPR₂₂ estimates were >1 % - meaning they did not meet the Reef 2050 Water Quality Improvement Plan's pesticide target for waters entering the GBR. There were marked spatial differences in TPR₂₂ estimates - regions dominated by grazing had lower estimates while those with sugar cane tended to have higher estimates. On average, active ingredients of PSII herbicides contributed 39 % of the TPR₂₂, the active ingredients of Other Herbicides contributed ~36 % and of Insecticides contributed ~24 %. Nine PAIs (diuron, imidacloprid, metolachlor, atrazine, MCPA, imazapic, metsulfuron, triclopyr and ametryn) were responsible for >97 % of TPR₂₂ across all the monitored waterways.

Effect of Pevonedistat, an Investigational NEDD8-Activating Enzyme Inhibitor, on the QTc Interval in Patients With Advanced Solid Tumors

The purpose of this study was to assess the effect of pevonedistat, a neural precursor cell expressed, developmentally down-regulated protein 8 (NEDD8)-activating enzyme inhibitor, on the heart rate-corrected QT (QTc) interval in cancer patients. Patients were randomized 1:1 to receive pevonedistat 25 or 50 mg/m² on day 1 and the alternate dose on day 8. Triplicate electrocardiograms were collected at intervals over 0-11 hours and at 24 hours via Holter recorders on days -1 (baseline), 1, and 8. Changes from time-matched baseline values were calculated for QTc by Fridericia (QTcF), PR, and QRS intervals. Serial time-matched blood samples for analysis of pevonedistat plasma pharmacokinetics were collected and a concentration-QTc analysis conducted. Safety was assessed by monitoring vital signs, physical examinations, and clinical laboratory tests. Forty-four patients were included in the QTc analysis. Maximum least square (LS) mean increase from time-matched baseline in QTcF was 3.2 milliseconds at 1 hour postdose for pevonedistat at 25 mg/m² , while the LSs mean change from baseline in QTcF was -1.7 milliseconds 1 hour postdose at 50 mg/m² . The maximum 2-sided 90% upper confidence bound was 6.7 and 2.9 milliseconds for pevonedistat at 25 and 50 mg/m² , respectively. Pevonedistat did not result in clinically relevant effects on heart rate, nor on PR or QRS intervals. Results from pevonedistat concentration-QTc analysis were consistent with these findings. Administration of pevonedistat to cancer patients at a dose of up to 50 mg/m² showed no evidence of QT prolongation, indicative of the lack of clinically meaningful effects on cardiac repolarization. ClinicalTrials.gov identifier: NCT03330106 (first registered on November 6, 2017).

Mocetinostat in Combination With Durvalumab for Patients With Advanced NSCLC: Results From a Phase I/II Study

BACKGROUND

Histone deacetylase (HDAC) inhibitors have potential to augment the effectiveness of immune checkpoint inhibitors and overcome treatment resistance. This dose-escalation/expansion study (NCT02805660) investigated mocetinostat (class I/IV HDAC inhibitor) plus durvalumab in patients with advanced non-small cell lung cancer (NSCLC) across cohorts defined by tumor programmed death-ligand 1 (PD-L1) expression and prior experience with anti-programmed cell death protein-1 (anti-PD-1) or anti-PD-L1 regimens.

PATIENTS AND METHODS

Sequential cohorts of patients with solid tumors received mocetinostat (starting dose: 50 mg TIW) plus durvalumab at a standard dose (1500 mg Q4W) to determine the recommended phase II dose (RP2D: phase I primary endpoint), based on the observed safety profile. RP2D was administered to patients with advanced NSCLC across 4 cohorts grouped by tumor PD-L1 expression (none or low/high) and prior experience with anti-PD-L1 /anti-PD-1 agents (naïve, clinical benefit: yes/no). The phase II primary endpoint was objective response rate (ORR, RECIST v1.1).

RESULTS

Eighty-three patients were enrolled (phase I [n = 20], phase II [n = 63]). RP2D was mocetinostat 70 mg TIW plus durvalumab. ORR was 11.5% across the phase II cohorts, and responses were durable (median 329 days). Clinical activity was observed in NSCLC patients with disease refractory to prior checkpoint inhibitor treatment: ORR 23.1%. Across all patients, fatigue (41%), nausea (40%), and diarrhea (31%) were the most frequent treatment-related adverse events.

CONCLUSION

Mocetinostat 70 mg TIW plus durvalumab at the standard dose was generally well tolerated. Clinical activity was observed in patients with NSCLC unresponsive to prior anti-PD-(L)1 therapy.

Phase 1 first-in-human study of dalutrafusp alfa, an anti-CD73-TGF-β-trap bifunctional antibody, in patients with advanced solid tumors

BACKGROUND

Cluster of differentiation (CD)73-adenosine and transforming growth factor (TGF)-β pathways are involved in abrogated antitumor immune responses and can lead to protumor conditions. This Phase 1 study (NCT03954704) evaluated the safety, pharmacokinetics, pharmacodynamics, and efficacy of dalutrafusp alfa (also known as GS-1423 and AGEN1423), a bifunctional, humanized, aglycosylated immunoglobulin G1 kappa antibody that selectively inhibits CD73-adenosine production and neutralizes active TGF-β signaling in patients with advanced solid tumors.

METHODS

Dose escalation started with an accelerated titration followed by a 3+3 design. Patients received dalutrafusp alfa (0.3, 1, 3, 10, 20, 30, or 45 mg/kg) intravenously every 2 weeks (Q2W) up to 1 year or until progressive disease (PD) or unacceptable toxicity.

RESULTS

In total, 21/22 patients received at least one dose of dalutrafusp alfa. The median number of dalutrafusp alfa doses administered was 3 (range 1-14). All patients had at least one adverse event (AE), most commonly fatigue (47.6%), nausea (33.3%), diarrhea (28.6%), and vomiting (28.6%). Nine (42.9%) patients had a Grade 3 or 4 AE; two had Grade 5 AEs of pulmonary embolism and PD, both unrelated to dalutrafusp alfa. Target-mediated drug disposition appears to be saturated at dalutrafusp alfa doses above 20 mg/kg. Complete CD73 target occupancy on B cells and CD8+ T cells was observed, and TGF-β 1/2/3 levels were undetectable at dalutrafusp alfa doses of 20 mg/kg and higher. Free soluble (s)CD73 levels and sCD73 activity increased with dalutrafusp alfa treatment. Seventeen patients reached the first response assessment, with complete response, partial response, stable disease, and PD in 0, 1 (4.8%), 7 (33.3%), and 9 (42.9%) patients, respectively.

CONCLUSIONS

Dalutrafusp alfa doses up to 45 mg/kg Q2W were well tolerated in patients with advanced solid tumors. Additional evaluation of dalutrafusp alfa could further elucidate the clinical utility of targeting CD73-adenosine and TGF-β pathways in oncology.

Manufacturing-dependent change in biological activity of the TLR4 agonist GSK1795091 and implications for lipid A analog development

A phase I trial (NCT03447314; 204686) evaluated the safety and efficacy of GSK1795091, a Toll-like receptor 4 (TLR4) agonist, in combination with immunotherapy (GSK3174998 [anti-OX40 monoclonal antibody], GSK3359609 [anti-ICOS monoclonal antibody], or pembrolizumab) in patients with solid tumors. The primary endpoint was safety; other endpoints included efficacy, pharmacokinetics, and pharmacodynamics (PD). Manufacturing of GSK1795091 formulation was modified during the trial to streamline production and administration, resulting in reduced PD (cytokine) activity. Fifty-four patients received GSK1795091 with a combination partner; 32 received only the modified GSK1795091 formulation, 15 received only the original formulation, and seven switched mid-study from the original to the modified formulation. Despite the modified formulation demonstrating higher systemic GSK1795091 exposure compared with the original formulation, the transient, dose-dependent elevations in cytokine and chemokine concentrations were no longer observed (e.g., IP-10, IL10, IL1-RA). Most patients (51/54; 94%) experienced ≥1 treatment-emergent adverse event (TEAE) during the study. Safety profiles were similar between formulations, but a higher incidence of TEAEs associated with immune responses (chills, fatigue, pyrexia, nausea, and vomiting) were observed with the original formulation. No conclusions can be made regarding GSK1795091 anti-tumor activity due to the limited data collected. Manufacturing changes were hypothesized to have caused the change in biological activity in this study. Structural characterization revealed GSK1795091 aggregate size in the modified formulation to be twice that in the original formulation, suggesting a negative correlation between GSK1795091 aggregate size and PD activity. This may have important clinical implications for future development of structurally similar compounds.

505 Relationship of infusion duration and dose to safety, efficacy and pharmacodynamics: second part of a phase 1–2 study using VSV-IFNβ-NIS (VV1) oncolytic virus in patients with refractory solid tumors

Background

Oncolytic viruses (OVs) show significant potential for treating tumors alongside immunotherapies.1 VV1 is an OV derived from the innocuous vesicular stomatitis virus (VSV). VV1 has been engineered to expresses human interferon (IFN) β and thyroidal sodium iodide symporter (NIS).2 VV1-infected cells produce IFNβ, which protects non-cancer cells from VV1 and allows VV1 to spread more efficiently in cancerous tissue.3 4 NIS expression on cells imports 99mTc pertechnetate, which facilitates in vivo imaging of virus infection.2 This three-part, phase 1–2 study was designed to determine the safety and tolerability of VV1 in patients with advanced unresectable and metastatic solid tumors. Here we report on the second part of this study: selection of recommended phase 2 regimen (RP2D), comprising further assessment of both duration and dose.

Methods

Patients (n=29) were enrolled to receive a single IV infusion of VVI monotherapy. 23 patients received IV VV1 1.7 x1010 TCID50 over 15, 30, 60 or 180 min. Six patients received 1.0 x1011 TCID50 over 30 min with aggressive premedication and fluid support overnight. Patients were monitored for dose limiting toxicities over 21 days with efficacy assessments after 6 weeks and then every 3 months for survival. The primary objective was to establish the safety and tolerability of IV VV1. Secondary objectives included preliminary efficacy, pharmacokinetics and pharmacodynamics.

Results

In this study VV1, demonstrated an acceptable safety profile. No deaths or Grade 4 infusion-related reactions (IRR) were reported. VV1 shedding by buccal swabs was negative at all study visits. Peak IFNβ serum levels and preliminary efficacy signals (2 PRs) were associated with 30 min infusion duration and higher dose, with RECIST data pending for 1 x 1011(table 1).

Abstract 505 Table 1

Conclusions

In this study, the absence of viral shedding demonstrates that VV1 is safe for patient and caregiver with little/no environmental impact. There was no difference in safety between the lower and the higher dose infusions. In this patient population acceptable tolerability was observed at the higher dose with 30 min duration, thus the RP2D is 1x 1011 over 30 mins.

Trial Registration

NCT02923466

References

Hemminki O, Dos Santos JM, Hemminki A. Oncolytic viruses for cancer immunotherapy. J Hematol Oncol 2020;13(1):84.

Naik S, Nace R, Federspiel MJ, Barber GN, Peng KW, Russell SJ. Curative one-shot systemic virotherapy in murine myeloma. Leukemia 2012;26(8):1870–1878.

Barber GN. Vesicular stomatitis virus as an oncolytic vector. Viral Immunol 2004;17(4):516–527.

Lichty BD, Power AT, Stojdl DF, Bell JC. Vesicular stomatitis virus: re-inventing the bullet. Trends Mol Med 2004;10(5):210–216.

Ethics Approval

Ethics approval was granted by WCG IRB. IRB tracking number: 20163005. Voluntary written informed consent was obtained from every patient prior to participation.

500 SYNB1891, a bacterium engineered to produce a STING agonist, demonstrates target engagement in humans following intratumoral injection

Background

SYNB1891 is a live, modified strain of probiotic E. coli Nissle engineered to produce cyclic dinucleotides under hypoxia leading to stimulator of interferon genes (STING)-activation in phagocytic antigen-presenting cells in tumors and activating complementary innate immune pathways.

Methods

This first-in-human study (NCT04167137) enrolled patients with refractory advanced solid tumors to receive intratumoral (IT) injections of SYNB1891 monotherapy or in combination atezolizumab. Patients enrolled in the monotherapy arms received doses of 1x106 - 3x108 live cells on Days 1, 8 and 15 of the first 21-day cycle and then on Day 1 of each subsequent cycle. Patients enrolled in the 2 combination cohorts received doses of 1x107 - 3x107 live cells in combination with atezolizumab administered on a 21-day cycle. The primary objective of the study was to evaluate safety and tolerability of SYNB1891 alone and in combination with atezolizumab. Other objectives include SYNB1891 kinetics in blood and injected tumor, STING-target engagement as assessed by IT gene expression and serum cytokines, and tumor responses.

Results

This interim analysis includes 23 patients across 6 monotherapy cohorts dosed at 1x106, 3x106, 1x107, or 3x107, 1x108 and 3x108 live cells, and 7 patients dosed in 2 combination therapy cohorts (1x107 and 3x107 live cells). The mean (range) age was 61 (25–82); 19 patients were female. There were 4 cytokine release syndrome events in monotherapy cohorts, including one grade 3 event which met the criterion for dose limiting toxicity at 3x108 live cells; there were no other SYNB1891-related serious adverse events. There were no SYNB1891-related infections. SYNB1891 was not detected in the blood at 6 or 24 hours after the first dose or intratumorally 7 days following the first dose. Treatment with SYNB1891 demonstrated activation of the STING pathway and target engagement as assessed by upregulation of interferon-stimulated genes (ISG15, IFIT1, IFIt2), chemokines/cytokines (CXCL9, CXCL10, TNFRS18, TNFSF10) and T-cell response genes (GZMA, CD4, PD-L2) in core biopsies obtained pre-dose and 7 days following the third weekly dose. In addition, there was a dose-response increase in serum cytokines. Durable, stable disease was observed in two patients treated with SYNB1891 monotherapy refractory to prior PD-1/L1 antibodies with vulvar melanoma (1x106 live cells; RECIST -28%) and small cell lung cancer (1x107 live cells; RECIST -12%).

Conclusions

Repeat IT injection of SYNB1891 as monotherapy and in combination atezolizumab in this ongoing study is safe and well-tolerated up to at least 1x108 live cells, and shows evidence of STING pathway target engagement.

Acknowledgements

We thank Inessa Vulfova for her clinical support in conduct of this study.

Trial Registration clinicaltrials.gov (NCT04167137)

Ethics Approval

The study protocol, the informed consent form (ICF), and printed subject information materials were reviewed and approved by the institutional review board (IRB) at the investigational site before any study procedures were performed. Written informed consent to participate in the study was obtained from each subject before any study-specific procedures were performed.The Ohio State University Cancer Institutional Review Board; Approval ID: 2020C0194MD Anderson Cancer Center Institutional Review Board; Approval ID: 2019–0576Mary Crawley Medical Research Center Institutional Review Board; Approval ID: 19–31 SYNB1891-CP-001North Texas Institutional Review Board; Approval ID: 2019.040WIRB Approval ID: 20192779University of Pittsburgh Institutional Review Board Approval ID: STUDY20010116

524 A phase 2, multi-arm study of anti-CD47 antibody, magrolimab, in combination with docetaxel in patients with locally advanced or metastatic solid tumors

Background

Patients with solid tumors who progress on standard chemotherapy and/or immune checkpoint inhibitors, have limited efficacy with existing standard of care chemotherapy options (objective response rates [ORR] ~10%). These patients have a significant unmet medical need. Novel agents that can safely enhance treatment efficacy are urgently needed. Magrolimab is a first-in-class monoclonal antibody that blocks the macrophage inhibitory immune checkpoint CD47, a ”do not eat me” signal overexpressed on tumor cells. Pre-clinical studies provide compelling evidence that magrolimab triggers phagocytosis and eliminates cancer cells from human solid tumors and hematologic malignancies. Magrolimab has demonstrated clinical activity in both hematologic and solid tumor malignancies. Chemotherapeutic agents, including taxanes, enhance prophagocytic signals on tumor cells, leading to synergistic antitumor activity when combined with magrolimab. This study (NCT04827576) is evaluating the safety, tolerability, and efficacy of magrolimab with docetaxel in relapsed/refractory (R/R) metastatic non-small cell lung cancer (mNSCLC), urothelial cancer (mUC), and small cell lung cancer (mSCLC).

Methods

This phase 2, open-label, multi-arm study consists of a safety run-in cohort and a phase 2 cohort. Eligible patients are ≥18 years old with chemotherapy and/or immunotherapy refractory mNSCLC, mSCLC, or mUC. Magrolimab is administered intravenously (IV) with an initial 1 mg/kg priming dose to mitigate on target anemia, followed by 30 mg/kg dose during cycle 1 (cycles are 21 days) in the safety run-in to identify any dose-limiting toxicities (DLTs) and determine a recommended phase 2 dose (RP2D). De-escalation may occur for DLTs per protocol. In phase 2, following the priming dose on day 1, magrolimab RP2D will be administered on days 8 and 15 of cycle 1; days 1, 8, 15 of cycle 2; and day 1 for cycles 3 and beyond. Docetaxel 75 mg/m2 (IV) is administered on day 1 of each cycle for all study participants. Patients may continue treatment until unacceptable toxicity, progressive disease by RECIST 1.1, or patient/investigator choice to discontinue. The primary endpoints are incidence of adverse events (safety and phase 2 cohorts) and ORR (phase 2). Secondary endpoints (phase 2) are progression-free survival, duration of response, and overall survival. Exploratory endpoints are to evaluate the pharmacodynamic, mechanism of action, and/or therapeutic response of biomarkers in blood and tumor biopsy samples and to explore biomarkers that may predict response to therapy. Planned enrollment is approximately 116 patients, and recruitment is ongoing.

Acknowledgements

Funding provided by Gilead Sciences, Inc.

Trial Registration

NCT04827576

Ethics Approval

The study protocol was approved by an institutional review board before enrollment of patients.

Consent

Patients provided written informed consent based on Declaration of Helsinki principles.

377 Characterization of peripheral biomarkers of GS-1423, a first in class bifunctional anti-CD73-TGFβ receptor II- trap molecule, in a phase 1 dose escalation study in patients with advanced solid tumors

Background

GS-1423 is a first-in-class bifunctional molecule comprised of an anti-CD73 antibody fused to the extracellular domain of TGFβ receptor II (TGFβRII). GS-1423 is designed to inhibit CD73-mediated adenosine production and neutralize active TGFβ within the tumor microenvironment. Dual antagonism of these 2 broadly immunosuppressive barriers is anticipated to facilitate productive anti-tumor immunity.

Methods

This open label Phase 1a study (NCT03954704) evaluated the safety, tolerability, and pharmacokinetics of GS-1423. Exploratory biomarkers included the evaluation of the inhibition of GS-1423 targets, i.e.CD73 and TGFβ, in the periphery. Biomarker assessments were performed in serial blood samples from patients receiving GS-1423 every two weeks (Q2W). Biomarker assays, unless otherwise stated, were custom built and qualified to measure the following: 1) TGF-beta 1/2/3 (Luminex, Bio-Rad) in platelet poor plasma, 2) CD73 target occupancy (TO) on B and CD8 T cells in whole blood, 3) free soluble CD73 (sCD73) not bound to GS-1423, and 4) sCD73 activity in platelet poor plasma. Biomarker values were plotted longitudinally by patient and by dose.

Results

A dose dependent decrease in TGF-beta 1/2/3 in plasma of patients was observed on treatment. There was no detectable TGFβ at the 20 mg/kg dose level and above at 2 hours post first dose and for the duration of the Q2W dosing interval. A dose dependent increase in CD73 TO on B and CD8 T cells was also observed with treatment, and complete TO was achieved at 20 mg/kg and above at 2 hours post first dose for the duration of the Q2W dosing interval. Free sCD73 decreased at 2 hours post first dose, while remaining above the lower limit of quantitation, and then increased above baseline after 24 hours post-dose at the 3 mg/kg dose level and above. The sCD73 activity in blood correlated with changes in free sCD73 levels.

Conclusions

Blood biomarker analyses of GS-1423 in patients with advanced solid tumors demonstrated undetectable soluble TGFβ1/2/3 and complete TO of CD73 on B and T cells at the 20 mg/kg dose level and above. The mechanism underlying the increase in sCD73 following GS-1423 treatment remains to be elucidated.

Ethics Approval

The study obtained ethics approval from the IRB/IEC and all participants gave informed consent before taking part in the study.

367 Pharmacokinetic and immunologic data from a phase I study of the click chemistry-based therapy SQ3370 in advanced solid tumors and soft-tissue sarcoma provides proof-of-concept for the CAPAC platform

Background

Conventional chemotherapeutics lack specificity for tumor tissue and usually have anarrow therapeutic index. SQ3370, a novel therapy that activates doxorubicin (Dox) at the tumor sitewhile minimizing systemic exposure, is based on intratumoral injection of a protodrug-activatinghyaluronic acid-based biopolymer (SQL70) followed by five daily intravenous (IV) doses of an attenuatedprotodrug of Dox (SQP33). SQ3370 utilizes Shasqi’s proprietary Click Activated Protodrugs AgainstCancer (CAPAC) platform where mutually-reactive click chemistry groups in the two components allowrelease of active Dox specifically at the tumor site. In animals, SQ3370 allowed for an 8.95-fold increase in dosing with minimal systemic adverse eventsand no cardiotoxicity. SQ3370 treatment of mouse tumor models showed improved overall survival,enhanced T-cell infiltration, and a robust anti-tumor response against both biopolymer-injected andnon-injected lesions,1 suggesting that SQ3370 promotes activation of the native immune systemagainst the tumor.

Methods

SQ3370-001 (NCT04106492) is a phase 1 trial open to patients with relapsed/refractory soft-tissue sarcoma or other advanced, potentially anthracycline-responsive solid tumors with an injectablelocal or metastatic lesion and =300 mg/m 2 prior exposure to Dox (or equivalent). Primary objectivesinclude safety, tolerability, and recommended Phase 2 dose. Additional objectives include preliminaryefficacy, plasma and tumor biopsy pharmacokinetics (PK), and immune response by peripheral bloodmass cytometry/tumor IHC.

Results

To date, ten patients have been enrolled. SQ3370 treatment has been well-tolerated with nodose-limiting toxicities observed. Plasma PK appeared consistent with preclinical data; rapid conversionof SQP33 protodrug to active Dox occurred but slowed as the residence time of the injected biopolymerlengthened. Systemic exposure to active Dox peaked on days 1–2 post biopolymer injection, followed bya decline on days 3–5. Preliminary tumor analysis shows that substantial local exposure to Dox continues2 weeks after the last SQP33 dose. Immune response analysis of early patient samples suggestsincreased tumor immune cell infiltration that dynamically changes with each cycle of treatment.

Conclusions

SQ3370 appears to be well-tolerated and demonstrates proof-of-concept for the first click-chemistry-based therapy in the clinic. Preclinical and clinical PK are consistent; high tumor exposure canbe achieved, so far without the typical clinical adverse events seen with IV Dox and potentiallyimproving the therapeutic index of a frequently-used chemotherapeutic agent.

Trial Registration

NCT04106492

Reference

Srinivasan S, Yee NA, Wu K, et al. SQ3370 activates cytotoxic drug via click chemistry at tumor andelicits sustained responses in injected and non-injected lesions. Advanced Therapeutics 2021;4(3):2000243.

Therapeutic targeting of SLC6A8 creatine transporter suppresses colon cancer progression and modulates human creatine levels

Colorectal cancer (CRC) is a leading cause of cancer mortality. Creatine metabolism was previously shown to critically regulate colon cancer progression. We report that RGX-202, an oral small-molecule SLC6A8 transporter inhibitor, robustly inhibits creatine import in vitro and in vivo, reduces intracellular phosphocreatine and ATP levels, and induces tumor apoptosis. RGX-202 suppressed CRC growth across KRAS wild-type and KRAS mutant xenograft, syngeneic, and patient-derived xenograft (PDX) tumors. Antitumor efficacy correlated with tumoral expression of creatine kinase B. Combining RGX-202 with 5-fluorouracil or the DHODH inhibitor leflunomide caused regressions of multiple colorectal xenograft and PDX tumors of distinct mutational backgrounds. RGX-202 also perturbed creatine metabolism in patients with metastatic CRC in a phase 1 trial, mirroring pharmacodynamic effects on creatine metabolism observed in mice. This is, to our knowledge, the first demonstration of preclinical and human pharmacodynamic activity for creatine metabolism targeting in oncology, thus revealing a critical therapeutic target.

Abstract 3035: Phase I study to assess the effect of adavosertib (AZD1775) on the pharmacokinetics of substrates of CYP1A2, CYP2C19 and CYP3A4 in patients with advanced solid tumors

Background: Adavosertib (AD), a selective WEE1 inhibitor, may alter exposure to compounds metabolized by cytochromes P450 (CYP); this two-period open-label study (NCT03333824) assessed the effect of AD on pharmacokinetics (PK) of probe substrates for CYP1A2 (caffeine; C), CYP2C19 (omeprazole; O) and CYP3A4 (midazolam; M).

Methods: In period 1, patients (pts) with locally advanced or metastatic solid tumors received a cocktail (CKT) of C 200 mg, O 20 mg, M 2 mg (single dose); in period 2, after a 7–14-day washout, pts received AD 225 mg bid on days 1–3 (5 doses), and with CKT on day 3. After CKT and AD administration, 24-hour PK sampling took place for C, O, M and their respective metabolites paraxanthine (P), 5-hydroxyomeprazole (5-HO), and 1′-hydroxymidazolam (1′-HM). Safety was assessed throughout.

Results: Of 33 pts (median age, 60.0 years, range 41–83; F:M, 18:15) receiving CKT, 30 pts were given AD. AD co-administration increased C, O and M exposure by 49%, 80% and 55% (AUC), respectively; AUC0–t increased by 61%, 98% and 55%; Cmax increased by 4%, 46% and 39% (Table 1). AD addition increased 5-HO and 1′-HM exposure by 43% and 54% (AUC), respectively, and by 49% and 58% (AUC0–t) respectively; P exposure was unchanged. AD co-administration decreased Cmax for P and 5-HO by 19% and 7%, respectively, whereas Cmax increased by 33% for 1′-HM. AD addition decreased CL/F and Vz/F for all substrates and increased t1/2 and tmax for most substrates and metabolites; tmax for M and 1′-HM were unchanged. A trend of decreasing metabolite/substrate ratios for AUC, AUC0–t and Cmax was seen with AD co-administration. After receiving AD, 24 (80%) pts reported adverse events (AEs), most commonly diarrhea (16 [53%]), vomiting (9 [30%]) and nausea (8 [27%]). Nineteen (63%) pts had treatment-related AEs (6 [20%] pts with grade ≥3).

Table 1Point estimates of the geometric least-square mean ratios S+AD/S (90% CI), %Median (range) tmax, hMean (SD) t½, hMean (SD) CL/F, L/hMean (SD) Vz/F, LMean MRAUCAUC0–tCmaxAUCAUC0–tCmax−AD+AD−AD+AD−AD+AD−AD+AD−AD+AD−AD+AD−AD+ADCaffeine*149.1 (131.3, 169.3)160.8 (143.3, 180.5)103.8 (92.2, 116.9)0.5 (0.3–3.0)0.7 (0.3–3.0)6.4 (3.8)13.5 (6.8)5.7 (2.5)3.8 (1.9)39.3 (15.0)37.9 (12.1)NAOmeprazole180.2 (145.7, 222.9)198.1 (160.3, 244.7)145.5 (114.0, 185.7)3.0 (0.7–6.0)3.9 (0.5–8.0)2.0 (1.0)2.5 (1.3)13.3 (10.5)7.6 (7.3)28.3 (16.6)19.8 (10.1)NAMidazolam155.3 (138.6, 173.9)155.2 (140.5, 171.5)138.5 (118.9, 161.3)0.5 (0.2–1.0)0.5 (0.2–1.0)5.5 (2.6)6.6 (3.0)59.0 (34.3)39.7 (14.5)409.9 (211.5)364.1 (182.7)NAParaxanthine†NCNC81.2 (74.6, 88.5)8.0 (4.0–11.8)9.9 (6.0–24.9)7.0 (2.7)12.2 (5.4)NA0.65NC0.540.320.230.165-HO143.0 (123.8, 165.0)148.8 (129.6, 170.8)92.9 (78.6, 109.8)3.0 (0.7–6.0)4.0 (1.8–7.8)2.7 (1.7)4.5 (4.7NA0.500.460.730.500.530.301′-HM153.5 (131.0, 179.8)158.2 (139.1, 180.0)133.4 (106.5, 167.1)0.5 (0.3–2.1)0.5 (0.2–1.0)7.2 (6.1)7.6 (7.1)NA0.410.450.430.440.470.43Patient numbers for cocktail without AD (period 1) were: caffeine (AUC: 22; AUC0–t, Cmax, tmax and t½: 25), omeprazole (AUC and t½: 21; AUC0–t, Cmax and tmax: 27), midazolam (AUC and t½: 22; AUC0–t, Cmax and tmax: 23), paraxanthine (AUC: 10; t½: 14; AUC0–t, Cmax and tmax: 19), 5-HO (AUC: 22; t½: 24; AUC0–t, Cmax and tmax: 28) and 1''-HM (AUC: 20; t½: 22; AUC0–t, Cmax and tmax: 24). Patient numbers for cocktail with AD (period 2) were: caffeine (AUC: 8; AUC0–t and t½: 18; Cmax and tmax: 19), omeprazole (AUC and t½: 15; AUC0–t: 18; Cmax and tmax: 20), midazolam (AUC and t½: 18; AUC0–t, Cmax and tmax: 19), paraxanthine (AUC: 1; t½: 5; AUC0–t: 15; Cmax and tmax: 16), 5-HO (AUC: 13; t½: 17; AUC0–t: 18; Cmax and tmax: 20) and 1''-HM (AUC: 17; t½: 18; AUC0–t, Cmax and tmax: 19). *Caffeine AUC was only reliably characterized in eight patients receiving cocktail with AD in period 2. Caffeine AUC increased in all patients with paired data for both periods for seven patients; results were considered representative of the data; †Paraxanthine AUC was only reliably characterized in 10 patients in period 1 (only cocktail) and one patient in period 2 (cocktail with AD); thus, the treatment comparison for AUC was not considered scientifically meaningful. 1′-HM, 1′-hydroxymidazolam; 5-HO, 5-hydroxyomeprazole; AD, adavosertib; AUC, area under the plasma concentration–time curve from time zero to infinity; AUC0–t, area under the plasma concentration–time curve from time zero to time of last quantifiable concentration; CI, confidence interval; CL/F, apparent clearance; Cmax, maximum plasma drug concentration; MR, metabolic ratio in relation to parent compound; NA, not available; NC, not calculable; S+AD/S, substrate (or compound) + AD compared with substrate or compound alone; SD, standard deviation; tmax, time to reach maximum plasma concentration; t½, terminal half-life; Vz/F, apparent volume of distribution

Conclusions: AD (225 mg bid) is a weak inhibitor of CYP1A2, CYP2C19 and CYP3A4. No new AD-related safety concerns were identified.

Citation Format: Mats Någård, Mei-Lin Ah-See, Karen So, James Strauss, Trisha Wise-Draper, Howard Safran, Ding Wang, Laura Nadeau, William Edenfield, Lionel D. Lewis, Lone Ottesen, Yan Li, Ganesh Mugundu. Phase I study to assess the effect of adavosertib (AZD1775) on the pharmacokinetics of substrates of CYP1A2, CYP2C19 and CYP3A4 in patients with advanced solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3035.

Abstract 591: Adavosertib (AZD1775) does not prolong QT interval in patients with advanced solid tumors: A Phase I open-label study

Background: Adavosertib (AZD1775; AD), a highly selective inhibitor of WEE1 kinase, regulates S and G2/M cell-cycle checkpoints. This study (NCT03333824; Part B) assessed the effect of doses of AD on the QT interval in patients (pts) with advanced solid tumors.

Methods: After a 7-14-day washout from prior short-term AD exposure, pts received AD 225 mg bid (five doses; combi therapy MTD/RP2D) on days 13 at 12-h intervals, under fasted conditions: 2 h pre-dose to 2 h post-dose. Pts underwent digital electrocardiogram (dECG) on day −1 (time-matched baseline), and dECG and pharmacokinetic (PK) sampling before AD administration and up to 12 h post-dose on days 1 and 3. Antiemetic(s) were given (1 mg granisetron ± 4 mg dexamethasone) on day −1 (baseline), and 30 min prior to AD (days 1-3). Pts had their final PK/dECG assessments on day 4, 24 h post-dose. Corrected QT interval by Fridericia (QTcF) outliers following dosing were defined as values &gt;450 ms or increases from baseline &gt;30 ms.

Results: Of 33 enrolled pts (median age, 60.0 years, range 41-83; F:M, 18:15), 21 (64%) received AD (Part B of the study). There was no significant relationship between ΔQTcF (vs baseline) and AD concentration. The slope of the linear relationship between ΔQTcF and AD concentration was not statistically significant (P=0.27), with the 95% CI of the slope (−0.003978, 0.01351) incl 0. Model predictions of ΔQTcF at the geometric mean of AD Cmax were, on day 1 (712.8 nM) and day 3 (1462 nM), −2.4 ms (90% CI −5.9, 1.1) and −0.8 ms (90% CI −5.1, 3.6), respectively. The largest mean difference in ΔQTcF was 7.3 ms, 3 h post-dose, on day 3. On day 1, two pts had an increase in QTcF &gt;30 ms, and one of these (who took mirtazapine) had increases in QTcF &gt;30 ms on day 3. No QTcF &gt;450 ms or increase in QTcF &gt;60 ms was observed. On day 1 and day 3, there were no apparent effects of AD on mean QRS, mean PR interval or heart rate (mean change was within ± 10 bpm). Geometric mean AUC0-12 and Cmax of AD on day 1 were 4940 nM·h and 712.8 nM, respectively, vs 10810 nM·h and 1462 nM on day 3. Cmin on day 3 was 410.4 nM. Geometric least-squares mean ratios (90% CI) of AD on day 3 vs day 1 for AUC0-12 and Cmax were 231% (200, 266) and 207% (170, 251), respectively; accumulation of AD over the dosing period was ~2.3 for AUC0-12 and ~2.1 for Cmax. Median tmax of AD was 3.0 h (range 1.0-6.0) on day 1 and 2.5 h (range 1.0-3.1) on day 3. Intra-subject variability was low (5% for AUC0-12 and 9% for Cmax) on day 3. AEs were reported by 16 (76%) patients, most commonly diarrhea, nausea (each 7 [33%] pts) and vomiting (5 [24%] pts). Eleven (52%) pts had treatment-related AEs (2 [10%] pts with grade ≥3).

Conclusions: No significant relationship was found between ΔQTcF and AD concentration. Modeling showed that AD does not have a clinically important effect on QT prolongation. Accumulation over the dosing period was approximately twofold, concordant with results from prior studies at this AD dose. No new safety concerns were reported.

Citation Format: Mats Någård, Mei-Lin Ah-See, Karen So, James Strauss, Trisha Wise-Draper, Howard Safran, Ding Wang, Laura Nadeau, William Edenfield, Lionel D. Lewis, Dinko Rekić, Corina Dota, Lone Ottesen, Yan Li, Ganesh Mugundu. Adavosertib (AZD1775) does not prolong QT interval in patients with advanced solid tumors: A Phase I open-label study [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 591.

Abstract LB-133: Correlative analysis of pharmacokinetics and pharmacodynamics of RGX-104, a first-in-class Liver-X-Receptor (LXR) agonist, and clinical outcomes in patients with advanced solid tumors

RGX-104, a first-in-class small-molecule LXR agonist modulates innate immunity and cancer progression via transcriptional activation of ApoE. ApoE protein suppresses tumor cell invasion and angiogenesis, and also depletes circulating and tumoral myeloid derived suppressor cells (MDSC), leading to T cell activation.A multivariate approach was used to address pharmacokinetic (PK) and pharmacodynamic relationships of RGX-104 in a phase 1 dose escalation study in patients with relapsed/refractory solid tumors. The study entailed multiple escalation arms with RGX-104 as monotherapy and in combination with nivolumab, ipilimumab, or docetaxel. Various markers including intratumoral ApoE and its receptor LRP1 in biopsy specimens, gene expression of LXR-targets in whole blood, serum markers including cytokines and lipids, as well as immune cell types such as MDSC, CD8 T-cells, and neutrophils in peripheral blood from patients were monitored at several time points. PK metrics were tracked to assess dose response relationships. Clinical outcomes such as objective response, time to disease progression, and duration on therapy were used for exploratory correlative analyses. A generally dose dependent increase in steady state exposure to RGX-104 was observed among all cohorts; the lowest efficacious exposure among patients with partial response was ~14,000 ng*h/mL. Treatment with RGX-104 at doses ranging from 120 mg BID to 240 mg BID induced expression of LXR targets, ApoE [2.7X (p=0.008) to 7.1X (p=0.007)] and ABCA1 [ 6.3X (p=1.20E-03) to 7X (p=8.1E-04] over baseline in a generally dose-dependent manner as assessed in whole blood. Similarly, MDSC depletion, ranging from 70%-90% relative to baseline, was observed in patients treated with RGX-104 along with concomitant CD8 T-cell activation; similar effects were noted in patients in combination cohorts. A model to explore dose dependency of change in immune cell types suggested that baseline levels of MDSC were most predictive of the magnitude of MDSC reduction after treatment, and that favorable clinical outcomes correlate with the extent of MDSC reduction and T cell activation. Low baseline levels of tumoral ApoE were associated with greater clinical benefit, with almost all patients with stable disease or partial response exhibiting ApoE tumor positive score of ≤20%; these patients also exhibited low/negative PD-L1 (&lt;1%) staining, revealing a target specific tumor biomarker and PD-L1 subset that could support prospective patient selection. These and additional markers will be tracked in expansion cohorts of RGX-104 in combination with pembrolizumab and carboplatin/pemetrexed for 1st line treatment of patients with metastatic non-small cell lung cancer (PD-L1 &lt;1%) and in combination with docetaxel for 2nd line treatment of patients with small cell lung cancer.

Citation Format: Monica Mita, Alan Mita, Erika Hamilton, Gerald S. Falchook, Michael Postow, Bartosz Chmielowski, Russell J. Schilder, James Strauss, Emerson Lim, Shubham Pant, Angela Jain, Oliver Rixe, Rebecca Redman, Kevin B. Kim, Tomislav Dragovich, R. Donald Harvey, Igor Puzanov, Nimisha Schneider, Renee Deehan, Tobi Guennel, Joe Lin, Sohail Tavazoie, Roger Waltzman, Eric Rowinsky, Michael Szarek, Subhasree Sridhar, Robert Busby, Narayan Lebaka, Celia Andreu, Isabel Kurth, David Darst, Masoud Tavazoie, Syed Raza, Robert Wasserman, Foster C. Gonsalves. Correlative analysis of pharmacokinetics and pharmacodynamics of RGX-104, a first-in-class Liver-X-Receptor (LXR) agonist, and clinical outcomes in patients with advanced solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-133.

Abstract CT146: RGX-104, a first-in-class immunotherapy targeting the liver-X receptor (LXR): Initial results from the phase 1b RGX-104 plus docetaxel combination dose escalation cohorts

Background: RGX-104 is a small-molecule LXR agonist that modulates innate immunity via transcriptional activation of the ApoE gene. Binding of ApoE to its receptor LRP8 robustly inhibits angiogenesis and depletes myeloid derived suppressor cells (MDSC), thereby activating cytotoxic T-lymphocytes. MDSCs are associated with resistance to both checkpoint inhibitors (CPI) and chemotherapy, providing a rationale for combination therapy with RGX-104. We previously reported results of the RGX-104 monotherapy dose escalation for which 26 patients with refractory solid tumors were treated in 5 dose cohorts. On-target AEs included hyperlipidemia and neutropenia. Flow-cytometry demonstrated MDSC depletion with associated T cell activation, which correlated with clinical benefit. A 40% disease control rate (DCR; SD+PR) was observed with a confirmed partial response (PR) by irRC (&gt;79% reduction in index lesions) in a patient with platinum-refractory small cell lung cancer (SCLC). Methods: Here, we present the safety, biomarker and efficacy results of the docetaxel combination arm of the RGX-104 trial. Cohort 1- RGX-104 80 mg BID, and docetaxel at 35 mg/m2 days 1, 8, and 15 of a 28-day cycle; Cohort 2- RGX-104 80 mg BID, 5 days-on/2 days-off (5/2), and docetaxel at 28 mg/m2 on above schedule. Cohort 3- RGX-104 100 mg BID (5/2), and docetaxel as per cohort 2. Results: As of February 7, 2020, 11 patients with refractory solid tumors have been treated in 3 dose escalation cohorts with RGX-104 plus docetaxel. AEs were consistent with the individual toxicity profiles of docetaxel and RGX-104, with neutropenia being the most common AE and dose-limiting in cohort 1. The 5/2 dosing regimen in cohorts 2 and 3 resulted in significantly fewer episodes of neutropenia and no DLTs, while maintaining pharmacodynamic effects including &gt;50% sustained MDSC depletion. A 66% DCR was observed in 9 evaluable patients including 2 patients in cohort 2 with PRs, a CPI-refractory SCCHN patient and a CPI-refractory melanoma patient, who remains on treatment at 36 weeks. A patient with melanoma in Cohort 3 had an initial assessment of SD and continues on study at 14 weeks. Clinical responses were associated with increases in T cell activation markers exceeding that generally observed with RGX-104 alone (up to a 5-fold increase in total CD8 T cells, a 7-fold increase in LAG-3+ CD8 T cells, and a 75-fold induction of serum IFNγ). Conclusion: The safety profile and marked pharmacodynamic and clinical activity of the RGX-104/docetaxel combination in CPI-refractory patients supports further development of this regimen. Consequently, the RGX-104/docetaxel regimen will be evaluated in a Phase 1b/2 expansion cohort in patients with relapsed/refractory ES-SCLC/high grade-neuroendocrine tumors.

Citation Format: Emerson Lim, Erika P. Hamilton, Rebecca Redman, Michael A. Postow, Russell J. Schilder, Monica M. Mita, Alain C. Mita, Bartosz Chmielowski, James Strauss, Angela Jain, Shubham Pant, Olivier Rixe, Tomislav Dragovich, R. Donald Harvey, Igor Puzanov, Kevin B. Kim, Eric K. Rowinsky, Michael Szarek, Foster Gonsalves, Isabel Kurth, Celia Andreu, Robert W. Busby, David Darst, Masoud Tavazoie, Syed Raza, Narayan Lebaka16, Robert Wasserman, Gerald Falchook. RGX-104, a first-in-class immunotherapy targeting the liver-X receptor (LXR): Initial results from the phase 1b RGX-104 plus docetaxel combination dose escalation cohorts [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT146.

A phase Ia/Ib dose-escalation study of intravenously administered SB 11285 alone and in combination with nivolumab in patients with advanced solid tumors

TPS3162

Background: Activation of the Stimulator of Interferon Genes (STING) pathway in immune cells in the tumor microenvironment (TME) and tumor cells results in the induction of innate and adaptive immunity and subsequent activation of cytotoxic T cells and NK cells for durable anti-tumor responses. SB 11285 is a novel agonist of the STING pathway leading to the activation of tumor-resident APCs and priming of tumor antigen specific CD8+ T cells. In our preclinical studies using multiple tumor-derived cell lines, SB 11285 has been observed to cause the induction of cytokines, such as INF-b, INF- a, TNFa and others consistent with engagement of the STING target, as well as tumor cell death by STING-mediated apoptosis. SB 11285 reduced tumor volumes in multiple rodent tumor models when administered intravenously, intraperitoneally or intratumorally as monotherapy or in combination with checkpoint inhibitors such as anti-CTLA-4 or anti-PD-1 antibody. Systemic administration could additionally facilitate trafficking of newly activated CD8+T cells from periphery into the tumor site. Methods: This open-label, multicenter phase 1a/1b clinical trial (NCT04096638) aims to enroll approximately 110 patients in the dose escalation (Part 1) and expansion cohorts (Part 2). Part 1 of the trial is a dose escalation study with IV SB 11285 monotherapy followed by combination with the checkpoint inhibitor nivolumab. Part 1 Dose Escalation of the study will evaluate ascending doses of intravenously administered SB 11285 with respect to dose-limiting toxicities (DLTs), maximum tolerated dose (MTD), recommended phase 2 dose (RP2D) and the pharmacokinetic (PK)/pharmacodynamic profile as monotherapy and in combination with nivolumab. SB 11285, with a starting dose of 0.3μg/kg, will be administered as monotherapy weekly on Days 1, 8, 15, and 22 of repeated 28-day cycles in escalating doses and in combination with nivolumab administered on Q4W schedule. Part 2 Expansion Cohorts of the study will explore initial signs of efficacy in pre-specified tumor types (such as Melanoma, Head and Neck squamous cell carcinoma) using the recommended phase 2 dose (RP2D) of SB 11285 in combination with nivolumab. In addition, the biological effects of SB 11285 will be evaluated by changes in immune cell types and activation state, serum cytokines, and gene expression patterns indicative of activation of the immune compartment. The trial is being conducted at multiple sites in the U.S . Clinical trial information: NCT04096638 .

Phase II trial of BPM31510-IV plus gemcitabine in advanced pancreatic ductal adenocarcinomas (PDAC)

723

Background: BPM31510-IV is an Ubidecarenone (CoQ10) drug-lipid conjugate nanodispersion targeting metabolic machinery in cancer, shifting bioenergetics from lactate dependency towards mitochondrial OxPhos to generate ROS and activate apoptosis. An MTD of BPM31510-IV in combination with gemcitabine was established at 110mg/kg in a Phase I clinical trial, which determined the dose for the Phase 2 investigation. Methods: Eligible patients (aged ≥ 18 y) with relapsed/refractory PDAC to standard treatment (ST) and met inclusion/exclusion criteria were recruited. Patients received 110mg/kg IV BPM31510 in combination with gemcitabine in a 144-hour infusion. Tumor response was evaluated at week 10 and then every 8 weeks. Study endpoints assessed were Overall Response Rate (ORR), Overall Survival (OS), Progression-Free Survival (PFS), Time to Progression (TTP), Tumor Response using Adaptive Molecular Responses (multi-omic molecular profiling), changes in CA 19-9 levels and patient reported Quality of Life (QOL) using the validated FACT-HEP PRO. A comprehensive multi-omic profiling for identification of biomarkers for patient stratification was explored. Results: Of the 35 patients enrolled to receive therapy, 18 patients met criteria of an adequately treated cohort (ATC- received BPM31510-IV + gemcitabine for 30 days over 2 cycles and had a RECIST 1.1 evaluation) while remaining (n = 17) had progressive disease (PD). Half of the ATC population (n = 9/18, 50%) achieved best ORR of stable disease (SD); 10/18 (55 %) demonstrated SD as best response at target lesions and 8/18 demonstrated SD at end of Cycle 2. The mTTP was 121 days (70 – 147, 95% CI); PFS 118 days (70 – 131, 95% CI) and OS 218 days (131 – 228, 95% CI), respectively. Overall, BPM31510-IV was well tolerated; the most common AE’s were GI related. Conclusions: The efficacy signal observed in this heavily pretreated population in addition to the toxicity profile warrants further clinical investigation of BPM31510-IV + gemcitabine in advanced PDAC. Clinical trial information: NCT02650804 . [Table: see text]

Determination of Atrazine in Water by Magnetic Particle Immunoassay: Collaborative Study

A collaborative study was performed to determine mean recovery and precision for analysis of atrazine in drinking and surface waters by immunoassay. The study design was based on the blind duplicate test plan for collaborative studies. Three blank waters (municipal drinking water, well water, and surface water) were spiked at 3 atrazine levels. Two water samples with naturally incurred atrazine loads were also spiked with atrazine at 3 levels. In the enzyme-linked immunoassay method, the water sample is mixed with a pesticide–enzyme conjugate and added to paramagnetic particles with triazine-specific antibodies attached. After separation of antibody-bound atrazine and atrazine–enzyme conjugate from free components, the bound enzyme conjugate catalyzes a reaction producing a colored end product. The color developed is inversely proportional to the original concentration of atrazine in the water sample. Fourteen laboratories participated in the collaborative study. Data were analyzed for repeatability and reproducibility, and average recoveries at the spike levels were calculated. Over the concentration range tested, the mean recovery of atrazine spiked into blank and pesticide-contaminated waters was 104%. Overall RSDRaveraged about 40% for atrazine concentrations near the method detection limit (0.05 μg/L) and about 15% at concentrations above 5 times the detection limit (0.25 μg/L). Corresponding single-analyst RSDr values were 24 and 10%. Recovery and precision for the 3 blank water matrixes and the waters that had been naturally contaminated with atrazine showed no significant differences. The magnetic particle immunoassay

Abstract CT090: Rational design of an oncolytic virus permits use of interferon beta as a pharmacodynamic marker for clinical application

Introduction. Voyager-V1 (VV1) is an oncolytic vesicular stomatitis virus engineered to express human interferon beta (IFNβ) to enhance cellular antitumor immune responses and tumor selectivity. VV1 also contains the human sodium iodide symporter (NIS) as an imaging gene. We report here the novel use of virus-encoded IFNβ as a PD marker using correlative data from three Phase I trials of VSV-IFNβ-NIS in patients with refractory cancers (n=46).

Methods. 46 patients with solid tumors (n=34) and hematological malignancies (n=12) received 1 dose of VV1 either intratumorally (ITu) or intravenously (IV) at doses ranging from 3 x 106 to 5 x 1010 TCID50. Plasma IFNβ levels were collected pre-treatment, 4 hours post-infusion, Day 2 (24-hour), Day 3, 8, 15 and 29 (IT only). Samples were processed using a standard IFNβ specific ELISA kit.

Results. ITu dose escalation is complete with 27 patients treated and no DLTs. IV escalation is ongoing at 5 x 1010 TCID50 with 19 patients treated to date. In the ITu study, plasma IFNβ levels at 24h were undetected at the lowest dose levels (up to 1 x 107 TCID50), and became detectable from 3 x 107 TCID50. In the IV patients, IFNβ was detectable at all dose levels (5 x 109 through 5 x 1010 TCID50) with the highest peak and longest duration in a patient with metastatic endometrial cancer coincident with shrinkage of multiple tumors. The IFNβ produced by virus-infected cells can be differentiated from the acute innate antiviral responses by magnitude of response and AUC as the majority of the inflammatory cytokines returned to baseline by 48h. Peak IFNβ levels were variable between patients, likely reflecting heterogeneity in tumor susceptibility to VV1, ranging from 1.4pg/mL to 656pg/mL across 6 patients (mean 153pg/ml) at the highest ITu dose. Plasma IFNβ 24 hours post-therapy of &gt;20pg/mL appears to predict for RECIST 1.1-evaluated SD vs PD, p=0.048 in the ITu patients. Peak IFNβ ranged from 18 to 1700 pg/mL across 9 patients (mean=442pg/ml) at 1.7 x 1010 in the IV study. Peak IFNβ was highest in two cases of endometrial cancer (1500 and 1700 pg/ml). The patient with the highest IFNβ levels on the IV trial showed 16.7% tumor shrinkage at the first tumor evaluation. SPECT imaging, which shows location of viral replication, was positive in 50% of ITu injected tumors, also validating of VV1 infection of target cells. To date, SPECT images were negative in the IV trial despite IFNβ positivity, reflecting IFNβ as a more sensitive PD marker of viral infection. IHC staining of tumor biopsies collected pre-treatment and 1 month after VSV showed increased numbers of CD3, CD8, CD68, PDL1 or PD1 in some injected or noninjected tumors. Other immune markers and tumor gene signatures are also being evaluated.

Conclusions. Plasma IFNβ has emerged as a simple and convenient biomarker of viral replication in tumors. IFNβ will be used in future studies as a PD marker to assess the impact of immune-modulating combination drugs with VV1.

Citation Format: Timothy P. Cripe, Jamie Bakkum-Gamez, Jaime R. Merchan, Martha Q. Lacy, Manish R. Patel, Steven Powell, James Strauss, Lianwen Zhang, Toshie Sakuma, Memy Diaz, Nandakumar Packiriswamy, Deepak Upreti, Bethany Brunton, Dragan Jevremovic, Stephen J. Russell, Alice Bexon, Kah-Whye Peng. Rational design of an oncolytic virus permits use of interferon beta as a pharmacodynamic marker for clinical application [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 CT090.

Abstract CT051: Preliminary correlative and clinical data from a first-in-human (FIH) study of the intratumoral (IT) oncolytic virotherapy, Voyager-V1, in patients with solid tumors

Introduction Voyager-V1TM is derived from VSV, a bullet-shaped negative sense RNA virus with very low human seroprevalence; it is engineered to selectively replicate in and kill human cancer cells. Voyager-V1 encodes the human IFNβ gene to boost antitumoral immune responses and the thyroidal sodium iodide symporter NIS gene to permit noninvasive imaging of virus spread. FIH studies are underway via both IV and IT routes. Here we report safety and preliminary correlative data from the FIH IT study.

Methods and objectives This is a classical 3+3 phase 1 design, using escalating single IT viral doses from 3 x 106 to 3 x 109 TCID50 into one target lesion. The primary objective is safety and tolerability, monitored by committee. Other objectives include PK by RT-PCR for viral genomes, serum IFNβ levels, Tc-99m SPECT/CT imaging to monitor virus infection in injected lesions, peripheral blood immunophenotyping with 11-color flow cytometry for activation markers on T cells, T-regs, NK cells, and MDSCs, and serial biopsies to assess the tumor microenvironment (TME). IHC was performed on tumor biopsies for CD3, CD8, CD4, FoxP3, CD68, PD-1 and PDL-1 pre and post treatment in non-injected and injected lesions. CD45 staining is ongoing.

Results Dose level 3 is ongoing (n=8+). No DLTs have been observed to date. Most patients were male (75%), white (100%), with ECOG PS1 (75%) and a median of &gt;6 lines of prior systemic therapy. AEs (in 63% patients) reported as related to study drug were mild-moderate, short-lived, and consisted of G1 fever, chills, hot flashes, nausea, vomiting, hyperhidrosis and G2 fatigue. Most patients had some mild AEs (pain, bruising, subclinical pneumothorax) related to biopsy and IT injection procedures and one had an SAE related to biopsy (G2 pneumothorax). There was no difference in incidence, intensity or duration of related AEs between dose levels so far. In patients analyzed to date, at the first three dose levels of 3 x 106, 1 x 107 and 3 x 107 TCID50 (n=7), viremia and serum IFNβ were below levels of detection after IT injection. There is evidence in all patients of an increase in PD-1 expression on CD4 and CD8 T cells, suggesting T cell activation post- single virus injection. One patient at dose level 2 had increased CD4 and CD8 T cells in the peripheral blood. TME analysis revealed increased infiltration of CD3 and CD8 cells in tumors of some patients. In addition, there are changes in numbers of FoxP3 and CD68 positive cells in the injected lesions compared to the pre-treatment and non-injected lesion. Two patients at dose level 3, one with an injected adrenal metastasis of colorectal cancer and another with a chest wall lesion from a head of pancreas primary, have positive SPECT/CTs on days 3-15 showing viral replication in tumor plus concomitant lymphocyte/neutrophil trafficking in the periphery.

Conclusions IT injection of a single dose of the novel oncolytic virotherapy Voyager-V1 has proven safe at doses up to 3 x 107 TCID50. There was evidence of T cell activation with increased PD-1 expression in peripheral blood lymphocytes after a single IT injection. Tumor biopsies indicate increased lymphocyte infiltration. Two patients at the highest dose tested show signs of viral replication in the injected lesion plus evidence of systemic impact on leukocyte populations.

Citation Format: Steven Powell, Manish R. Patel, Jaime R. Merchan, Timothy P. Cripe, James Strauss, Rosa M. Diaz, Nandakumar Packiriswamy, Bethany A. Brunton, Deepak Upreti, Rehan Khan, Lukkana Suksanpaisan, Rianna Vandergaast, Stephen J. Russell, Alice S. Bexon, Kah Whye Peng. Preliminary correlative and clinical data from a first-in-human (FIH) study of the intratumoral (IT) oncolytic virotherapy, Voyager-V1, in patients with solid tumors [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 CT051.